4405 Notes

Net Ecosystem Exchange (NEE)

*Net Ecosystem Exchange:* is a measurement of how much carbon is entering and leaving the ecosystem.

Spatial patterns - 3 different patterns of changes over distance

Gradients (trends) steady directional change in numbers over a specific distance Patches (clumps) a relatively uniform and homogenous area separated by gaps Noise (random fluctuations) variation not able to be explained by a model

4 different ways we can think about measuring stability

the degree to which a *variable changes* after a perturbation or disturbance. the amount of change a system can *absorb*. *return time* to an equilibrium / original state after perturbation or disturbance how *variable* the system is around an equilibrium point.

Historical Views on Ecosystem Ecology & 3 Early Key Players

*1600's* Focus on plants and the origins of the how plants grew and what they were made of *1800's* Subsequently shown to produce O2 and CO2 ultimately linking the biotic and abiotic *1900's* Only recently returned to study integrated biogeochemical processes at large spatial scales. Tansley (1935) - coined the term Ecosystem Ecology Hutchinson & Lindeman (1942) - trophic dynamics H. Odum & E.P. Odum (1969) - systems approach (viewed as a whole, not the sum of parts)

Ecosystem Structure (components)

*Abiotic components* • Atmosphere • Soil • Water *Biotic components* • Plants (primary producers) • Animals • Microbes • Detritus? (detritus is not necessarily alive though) Note: Plants aren't always the primary producers In deep sea hydrothermal vents bacteria are primary producers

Plant allocation

*Allocation:* - ways in which plants distribute elemental and energy resources among various plant functions: • Growth, Reproduction, Maintenance • Storage, Defense Allocation varies among species, in response to environmental changes, and developmental stage *Stoichiometry:* - the relative proportion of components - ratio of nutrients in biomass (C:N:P)

Autotrophs vs Heterotrophs

*Autotrophs:* synthesize organic molecules from inorganic sources (primary producers) • Photosynthesis • Chemosynthesis *Heterotrophs:* obtain energy by feeding on other organisms (consumers)

Biomes

*Biomes are groups of biological communities and ecosystems based on climate and dominant plant form, which give them their overall character* Biomes can be: - Terrestrial (land based) - Aquatic (water based) • Fresh Water • Marine The biome concept organizes large scale ecological variation

Plant adaptations to low nutrient environments

*Carnivorous Plants* - ie: venus fly trap, pitcher plants, sun dews *Relationships with Nitrogen fixing bacteria* - Nitrogen as a molecule is not actually limiting... Nitrogen is just not available in a biologically available way from air (N₂ gas) - Its too much energy to break the triple bond. - Nitrogen fixing bacteria are the exception, who can break those bonds - N bacteria can be free living or epiphitic (living on other plants) *Relationships with mycorrhizal fungi* (myco = fungi rhizal = root) - Ectomycorrhizal forms sheaths outside the roots - Endomycorrhizal: penetrate inside the root itself

Name 3 ways we can measure large scale processes:

*Chamber methods:* Similar to light-dark methods Fundamental/Individual level *Eddy Covariance:* Meteorological towers across ecosystems that measure CO₂ and O₂. Helps understand highest scale of carbon flux *MODIS:* Satellite data combined with mathematical modelling. Very useful to include both the temporal and spatial scales

Community ecology

*Community ecology:* Description & quantification of natural assemblages of different species/populations. • Interspecific interactions • Variability across space and time

What is a Community?

*Community:* Collection of species/populations interacting directly and indirectly in the same place & time.

Convergence

*Convergence* is the process by which unrelated organisms evolve a resemblance to each other in response to similar environmental conditions. *Convergence is the underlying principle of the biome concept* Different species evolve similar traits because they face similar selective pressures To be repeatable, it means that species found there are similar due to similar selective pressures

Limiting Nutrients

*Ecological stoichiometry* Stoichiometry refers to the proportion of elements of living organisms. (Biotic entities only) Elements are available in varying proportions in the environment The limiting element will determine the overall rate of development Typically nitrogen (N) or phosphorus (P) Often linked to trophic interactions

Ecosystem ecology

*Ecosystem ecology:* Study of interactions among organisms and their physical environment as an integrated system. • Rates of energy and nutrient flux Ask large scale questions What powers life? How do sunlight and nutrients affect plants as primary producers? How do contaminants propagate or degrade through biogeochemical cycles? What are the causes and consequences of climate change?

What is an Ecosystem?

*Ecosystem:* Bounded ecological system consisting of all organisms in a given area & the physical environment.

Response - effect trait framework:

*Effect traits* of a species underlie its impacts on ecosystem properties and the services or disservices that human societies derive from them. *Response traits* influence the abilities of species to colonize or thrive in a habitat and to persist in the face of environmental changes.

Environmental Science

*Environmental science:* is an interdisciplinary study of how the Earth works (physical, chemical and biological), that also includes: • How humans interact with the Earth • How to deal with environmental problems

Measuring Spatial scale

*Grain* - the size of the individual units of observation. *Extent* - the overall area encompassed by an investigation or the area included within the landscape boundary.

Gross Primary Productivity (GPP) What scale is this on?

*Gross Primary Production (GPP)* is the total amount of CO₂ that is fixed by plants in photosynthesis. GPP is an *ecosystem scale* process, looks at total amount of photosynthesis occurring

Watershed Structure

*Headwaters*: collect precipitation *Divide*: height-of-land *Stream Order*: tributaries -> river *Mouth*: riven opens into a larger body of water *Estuary*: where stream meets ocean (brackish) Gravity is main factor Height of land becomes physical boundary

Landscape Ecology

*Landscape ecology:* Study of the spatial arrangement of ecosystems & how this affects biotic & abiotic components.

What is a Landscape?

*Landscape:* heterogeneous region consisting of ≥2 interacting ecosystems exchanging organisms, energy, water, nutrients, etc.

Mass Balance Approach

*Most foundational concept* Like an accounting system Flows of energy, nutrients, contaminants in and out of the system We can quantify the inputs and outputs in the system Once we do this, we can formulate hypotheses about the rates Input = Output + Accumulation - Materials enter a system (input) - Materials are in a component of the system (accumulation) - Materials leave the system (output)

Steady State

*Mostly not realised, but is an assumption of Mass Balance:* inputs = outputs Why do we assume this if it rarely exists? It gives us a simplified place to start; a null hypothesis of sorts The distribution of elements is always changing, but... A steady state can occur when: - All fluxes between different compartments balance, and there are no net changes. - Input = Output (dN/dt = 0) - Does not mean that nothing happens

Niche complementarity:

*Niche complementarity:* Differences among species in their requirements for different resources Consequence: Complementary interactions so that a combination of species obtain more resources than a single species. Outcome: Higher biomass production and lower levels of unconsumed resources. Cedar creek - david tilman Plots have 1-26 different species in them (a gradient of diversity) Shows greater amounts of biomass, less unconsumed resources when we have more species doing different things in a system

Nitrogen Mineralization

*Nitrogen Mineralization:* how much nitrogen is being liberated from tissues/biomass through the process of decomposition by microbes - microbes making nitrogen available (ammonia and nitrite) Productivity increases with increased mineralization rates

Nutrient Limitation What makes a nutrient limiting?

*Nutrient limitation:* any nutrient in small supply is likely limiting growth, and is therefore also likely to be preferentially absorbed by plants. (Liebig's barrel) Limiting occurs because: *1. They need a lot of it* *2. There's not enough* in the environment or the *availability doesn't match requirements* of the plant What controls plant acquisition/allocation? • Dynamic balance between supply and demand • Proportional availability of nutrients (nutrient ratio) Different plants have different requirements too (can't use fertilizer for roses as you would with another plant because they need different fertilizer ratios)

Nutrient use efficiency (NUE)

*Nutrient use efficiency (NUE):* is a measure of how well plants use the available mineral nutrients. It can be defined as yield (biomass, NPP) per unit input (fertilizer, nutrient content). The environment provides a feedback systems for nutrient use efficiency NUE depends on: ability to take up the nutrients from the soil (e.g. CEC) transport storage mobilization usage within the plant environment

Individual (organismal) ecology

*Organismal Ecology:* Study of the life history (and behaviour) of an individual & its response to its environment. • Genotype/phenotype • Trade-offs

Soil Formation and Classification

*Pedogenesis* = soil formation Soils are formed through: 1. Weathering of parent material (rocks) 2. Organisms (organic matter input and decomposition) 3. Climate - rates of activity 4. Local topology (relief) 5. Time Soils classified schemes are based on the percentage of sand, silt and clay.

Population ecology

*Population ecology:* Study of the abundance, distribution, productivity, & dynamics of a group of individuals of the same species. • Intraspecific interactions • Rates of growth (r)

What is a population?

*Population:* group of potentially interbreeding & interacting individuals of the same species living in the same place & time.

Production vs Primary Production

*Production:* the creation of new organic matter -even humans do this (creating muscle/bone) *Primary production:* the synthesis and storage of organic molecules during the growth and reproduction of autotrophs - this is the first time it happens in the food web

The riparian zone and flood plains

*Riparian areas* are the lands adjacent to streams, rivers, lakes and wetlands, where the vegetation and soils are strongly influenced by the presence of water. Are an important area in conservation and management

Water holding capacity of soils

*Soil Texture* = how big soil particles are Small soil particles means more surface area (high perimeter to volume ratios Fine particle soils hold lots of water Sand is large, few pore spaces, and small pore volume Therefore we have low field capacity and low wilting point Clay has many small pore spaces; high adhesion forces Therefore we have high field capacity and high wilting point At very small and very large soil particles, there is a very narrow range between field capacity and wilting point which is bad The best soils have large range (distance between wilting point and field capacity) = loamy/silt-loamy

Define Spatial Ecology and Landscape Ecology

*Spatial ecology:* the identification of spatial patterns and their relationships to ecological phenomena. *Landscape ecology:* the study of the pattern and interactions between ecosystems within a region.

Soil horizons

*TOP* o Organic (O horizon) o Topsoil (A horizon) o Leached (E horizon) o Subsoil (B horizon) o Weathered rock (C horizon) o Solid bedrock (R horizon) *BOTTOM*

What causes variation in the strength of a trophic cascade?

*Top-down* processes dominate *trophic dynamics* - how different trophic levels interact *Bottom up* processes determine *food web structure* - availability of nutrients and energy will determine overall structure and complexity of the food web What will determine the strength of a trophic cascade? - Comes down to efficiencies *1. Relative body sizes of predators and prey* • Larger predators (or pred:prey size ratio) impose stronger top-down controls (depends on consumption efficiency) - Larger bodied organisms have greater metabolic costs than smaller bodied organisms, eat more of their prey as a result (would be less if they were similar sizes) *2. Metabolism of predators* • Determines rate of both assimilation and respiration - Assimilation and production efficiencies - More metabolic costs means trophic transfer efficiency is decreasing (weakens top down controls) - Related to size in that larger organisms have more metabolic costs *3. Production-to-Biomass of plants* - essentially a system's productivity • Plants with high production-to-biomass ratios provide more energy (related to 10% rule - more energy at base) - base of food web has more energy - more productive systems have stronger bottom up trophic cascades

Trophic transfer efficiency

*Trophic transfer efficiency* (TTE) = the efficiency with which energy is transferred from one trophic level to the next. *Trophic Efficiency = Consumption Efficiency x Assimilation Efficiency x Production Efficiency* - Loss of carbon through respiration, root exudates, death - Only about 10% of primary producers standing biomass/energy is moved on to next trophic level - Herbivores also respire, poop, die, etc. only about 10% here transfers as well - Loss of energy as you go up the food chain Equivalent to the amount of consumer production divided by the amount of prey production

Feedbacks to Climate

*Turbulence through latent and sensible heat flux* • Heat rises (sensible heat flux) • Evaporation and condensation (latent heat flux) *Atmospheric circulation* • Coriolis effect (essentially a drag effect) • Uneven due to Earth's surface *The Ocean* • Has stable layers (depth) • Currents and upwells *Landforms* • Regional and local scale • Offshore breezes, rainshadow effects, and inversions Air rising in tropics, falling in poles but also being affected by tilt and rotation Coriolis effect - essentially a drag effect

Watershed Ecology

*Watershed Ecology*: The study of watersheds as ecosystems, primarily the analysis of interacting biotic and abiotic components within a watershed's boundaries. It is a funnel essentially Primary factor is gravity Interacting biotic and abiotic interactions

Watershed

*Watershed*: An area of land that drains water, sediment and dissolved materials to a common receiving body or outlet. Can draw a physical "box" around this ecosystem/entity; It has a delineable boundary Watershed is also called: Drainage basin River basin Catchment (area)

Lecture 3:

- Open versus closed ecosystems (Bounded?) - Earth's climate system - Geology and soils - Cornerstones of ecosystem ecology

The Water Balance

- Precipitation - Interception, stemflow, and throughfall - Surface runoff and soil infiltration

Precipitation

- Water falling to the Earth from the atmosphere in the form of rain, snow, sleet, or hail. - Total annual volume of precipitation on Earth =~500,000 km^3, Only ¼ of which falls on land surfaces; majority of water falls back into the ocean

What is a Species?

Species: all individuals that can potentially breed with one another and produce viable offspring.

5 Types of Food Webs

1. *Connectivity Web* = only who's connected to who - very little descriptive information from this web... no numbers 2. *Diet Proportion Web* = what proportion of a diet is species A or species B - could look at gut contents - just what is in the stomach isn't necessarily a good representation of energy flow 3. *Assimilation Web* = fraction that is assimilated - if 90% of diet is celery and 10% pizza, you will probably assimilate more energy from pizza than you will from celery in assimilation web, it might be 50/50 even though your diet proportion is different 4. *Energy Flow Web* = amount of energy flow ie calories, grams of carbon 5. *Ingestion/Production Web* = Influence of one trophic level on another - proportion of feeding by a consumer divided by biomass available for them to feed on

5 Major Ecosystem Attributes

1. Climate 2. Parent Material (geology) 3. Topology (geography) 4. Potential Biota 5. Time (ecological succession)

Functional Redundancy Functional Insurance

1. Functional redundancy - the disappearance of one species within a functional effect group has no effect on ecosystem function 2. Functional insurance - the greater the variation of different response traits of species belonging to the same functional effect group enable the maintenance of long-term ecosystem functioning

Types of soil water

1. Hygroscopic 2. Capillary 3. Gravitational Most water in the soil is in the form of *hygroscopic water* - *thin film* of water around soil particles held there by *adhesion forces* Hygroscopic water is *unavailable to plants because roots cant disrupt adhesion forces* Can't support plant growth - this is the *wilting point* for plants More soil moisture Still have hygroscopic water but then also have accumulating water around *pore spaces of soil particles* - held there by attraction of water molecules (*cohesion forces*) which *oppose gravitational forces* = *capillary water* This water is available to plants When we have *complete saturation* (no air spaces) we still have hygroscopic and capillary water, but then also have *gravitational water* which is under the effect of gravity and can flow to groundwater *Field capacity* = point of soil moisture after we have lost all gravitational water, only hygroscopic and capillary water left *Wilting point* = only hygroscopic

Two general mechanisms

1. Niche complementarity (resource partitioning) • Differences among species in their requirements for different resources • Higher biomass production • Lower levels of unconsumed resources 2. Selection effect • the higher the species richness in a community, the higher the probability of the presence of a species with a particularly important trait

Categories of Ecosystem Services

1. Provisioning services: supply of goods of direct benefit to people; often have a dollar value (food, water, fiber, fuelwood) 2. Regulating services: the range of functions carried out by ecosystems; more and more of these are being given a dollar value (climate regulation, water purification, pollination) 3. Cultural services: contributing to wider needs and desires of society; non-material benefit - intangible (spiritual & religious, ecotourism, aesthetic, educational) 4. Supporting services: essential to the functioning of ecosystems; required for all the other ecosystem services (nutrient cycling, evolution, soil formation, primary produciton)

Plant nutrient loss

1. Release to atmosphere • CO2 from respiration • Volatile hydrocarbons from leaves • Aerosols • NH3 (decomposition), N2 (denitrification) 2. Tissue senescence / death • Reduced by increasing longevity of biomass and/or resorption 3. Root exudation (including diffusion out of roots) 4. Consumption by herbivores (& loss to parasites) 5. Disturbances

Ecosystem Management

1. Requires consideration of geographic areas defined by ecological boundaries 2. Requires managers to account for complexity of natural processes and social systems 3. Incorporates explicit definition of biological and social goals at national and local scales 4. Emphasizes collaborative decision making 5. Uses a process of adaptive management to account for uncertainty Several approaches to effective ecosystem management engage conservation efforts at both a local or landscape level and involves: adaptive management natural resource management strategic management command and control management

Controls on litter decomposition

1. Temperature — as a metabolic process, decomposition increases with increasing temperature 2. Moisture - decomposition is limited at very low, or very high moisture (unimodal relationship) 3. Litter quality (and quantity) - relative proportions of nutrients (e.g. C:N), as well as structural form 4. Soil organisms - microbial activity regulated and facilitated by soil animals.

Intermediate grazing hypothesis

A variant of the intermediate disturbance hypothesis: - Microbial productivity hypothesised to peak at an intermediate level of grazing

Climate change as a stressor

Systematic and progressive changes in climate including: • Temperature • Atmospheric CO2 levels • Precipitation • Variability • Ocean acidification

Mass ratio hypothesis

Abundant species matter (dominants) Singletons don't matter (transients) • Calculated by community weighted means of traits

Allochthonous vs Autochthonous

Allochthonous: inputs coming from outside the system Autochthonous: produced from within a system

Regime shifts and Alternative stable states

Alternative stable state - systems exist in different configurations, and these different configurations represent different equilibrium states. Regime shift (phase shift) - a change from one system's state to another Tipping point - the critical threshold at which a system undergoes a regime shift

Lecture 20:

Anthropocene

Applicability of the biome concept

Applicability of the biome concept - good for basic broad categorical applications Whittaker's biome delineation (1975) is the most common graphical representation of terrestrial biomes

Tundra Biomes

Arctic tundra: in the northern hemisphere above the taiga Alpine tundra: located on mountains throughout the world at high altitude where trees cannot grow. Physiological limits of tree growth is temperature Very low temperatures, but also very low precipitation Moisture is mainly in form of snow, but still relatively low

Assimilation efficiency

Assimilation efficiency: the amount of assimilation divided by the amount of food ingestion - The food you eat - some will be assimilated into tissues, some will be excreted - Pooping more = less assimilation efficiency relative proportion of assimilation and ingestion

Lecture 13:

BG Foodwebs

Adaptive management

Based on the concept that predicting future influences/disturbance to an ecosystem is limited and unclear. Dangers include: • expecting too much of it • assuming that it will always enhance • license to try -> timelines?

Exam Room

TC 341

Lecture 17:

Biodiversity-Productivity

Biomass

Biomass = the dry weight of living material

Recall: A Biome is?

Biome: a repeatable ecosystem type based on similar vegetation (dependent on temperature and moisture)

Biosphere

Biosphere: Global sum of all ecosystems (biotic and abiotic) as an integrated system. • Climate systems Earth as an ecological entity or system.

Desert Biome Biota

Biota • Generally species poor compared to most biomes • Specialised vegetation and animals • Ecological analogues via convergent evolution Physiological limitations of low moisture result in very specialized species Morphological attributes that are adaptation to this biome (ie: Chloroplasts in stems, specialized cell structures to retain moisture) Plants and animals take on similar strategies and converge on similar looks Similar plants don't share traits because they're related necessarily, but due to convergent evolution

Grasslands Biome Biota

Biota • Grasses are dominant with lots of non-woody flowering plants • Temperate grasslands have low diversity but high abundance of animals (biomass!) Sweepnet sampling for invertebrates Alberta-style! Think: Hoard of Locusts

Tundra Biome Biota

Biota • Nearly 2,000 species of plants, mainly mosses, sedges, grasses and flowering plants, form the vegetation of the tundra • Migratory animals • Oscillating populations Thick waxy leaves to protect themselves, retain moisture Wind can be detrimental too in open system Flowering plants need pollinators, lots of them still up there Lots of the species there are migratory species Lots of migratory birds use these areas as habitats Lots of diversity near oceans Predator prey relationships are often offset for the next year

Temperate Forest Biome Biota

Biota • Tree species diversity is lower than tropics • Net primary productivity varies geographically and is primarily influenced by growing season • Ecological succession is critical in determining biodiversity Amount of biodiversity is highly affected by disturbance High mite diversity

Body size spectra

Body size spectra: inverse relationship between abundance and body size Smaller organisms are far more abundant than large organisms Body size spectra describes the negative relationship between abundance and body mass The *slope* is hypothesised to predict *trophic transfer efficiency* Steepening of the slope suggests less efficient transfer of nutrients Body size determines where they can live Microfauna - live in soil water film (hygroscopic) Mesofauna and Macrofauna - live in air-filled pore spaces

Boreal peatlands

Boreal peatlands only cover ~3% of Earth's surface, but contains ~30% of the Earth's terrestrial SOC Decomposition rates are even lower because of anoxic conditions sphagnum mosses dominate thrive in nutrient poor conditions Very slow nitrogen cycling Low nutrients, plants that uptake nitrogen, but protect it - slow growing, long lived, toxic secondary metabolites, low herbivory - these mosses are very slow to breakdown which facilitates nutrient poor conditions Vegetation is generally recalcitrant Boreal peatlands are very important for carbon sequestration also have high mining potentials - threatened ecosystems

Why do Boreal systems have high carbon stocks?

Boreal trees - lots of conifers - needles are calcitrant so they take a long time to break down = low decomposition rates

Nutrient Use Efficiency versus Carbon Use Efficiency

CUE: determines energy flow to higher trophic levels, and rates of ecosystem carbon storage Recalcitrant C sources can reduce CUE Affected by environmental conditions (e.g. temperature) Depends on nitrogen availability Nutrient use efficiency (NUE): uptake for growth (and reproduction) (retention and immobilisation) versus release Also depends on nitrogen availability (limited N -> Increased NUE) NUE is independent of CUE in microbes

Measuring decomposition

Can solve for K - decomposition constant. Decomposition constant, when taking inverse of it, gives you estimate of mean residence time (on average, how long is this substrate going to last in the environment?) Follows negative exponential pattern.

Carbon Use Efficiency

Carbon Use Efficiency (CUE) = NPP to GPP ratio Maximizing carbon in, minimizing carbon out = how efficient you are at using carbon • describes the capacity of forests to transfer carbon from the atmosphere to terrestrial biomass Level of efficiency when looking at all ecosystems and their biomes is relatively the same (~0.5 or 50%) - If there is an increase we know that the plant can increase their biomass of the ecosystem • Older a plant gets, the more C it releases relative to what it takes in - Photosynthetically useless, they aren't really growing anymore

Carbon

Carbon makes up ~1/2 of organic matter on Earth (H and O account for most of the rest) Carbon (≈ Biomass) = Energy currency in ecosystems Photosynthesis makes carbon bioavailable (from an inorganic state to an organic state)

Lecture 14:

Cascades

Cation Exchange Capacity (CEC)

Cation Exchange Capacity = the degree to which a soil can adsorb and exchange cations. (Tiny root hairs are responsible for taking up nutrients) Can talk about the CEC of both the soil and the roots Clay soil particle is negatively charged, so the cations (positive) are stuck to anions of clay Root remove those cations from the soil particle by exchanging hydrogen molecules for the other cations The cations need to go into solution in the soil water before the root can take it up, therefore the nutrient can get lost through gravitational flow or leaching (of both cations and anions) If soils are watered too much, anions in the soils like nitrates that plants need are leached out How negatively charged soils are also affects CEC Soils with high capacity to hold cations in (ie clay) actually reduce leaching of soil nutrients Sand doesn't hold cations as well so there is more leaching

Radiative Balance

Changes in atmospheric radiatively active gases will alter the balance • CO2 • CH4 • N2O • CFCs Wavelengths are related to energy - earth emits long wave radiation (low energy) most of which cannot escape the atmosphere (therefore it retains the energy) 3 different means of retaining energy

The Biome Concept

Clements 1916 - The Biome Concept "The concept of the biome is a logical outcome of the treatment of the plant community as a complex organism, or superorganism, with characteristic development and structure" Clements followed succession deterministic model Biomes reflected a "super organism" He believed it was predictive ie: embryo develop into person. It needs to have 2 lungs, 2 eyes, 1 heart etc. Plants must fill these predestined end point This endpoint is concept of biome Biome concept is outdated now We know its a lot more random We still utilize the term biome for broad classification of vegetative communities "putting ecosystems into boxes"

Tundra Biomes Climate

Climate Extreme cold and low precipitation • Average winter -34°C • Average summer 3-12°C Short growing season (< 60 days), low growth potential for organisms

Grasslands Biome Climate

Climate Hot summers (> 38°C) and cold (-40°C) winters Low to moderate rainfall, and marked seasonality Hot summers, nice growing seasons Huge seasonality in precipitation Temperature and precipitation follow same trend of increasing in summer, decreasing in winter Excellent biome for humans to exploit

Savanna Biome Climate

Climate Mean monthly temperature above 18°C Always warm with a notable wet-dry seasonality Always warm Notable wet and dry season There is enough rain throughout the year to support tree growth if it was consistent... The main issue is the variability! The dry seasons have fires! Grasses are very good fire starters (fires = patchy) These limit tree growth

Boreal Forest Biome (Taiga) Climate

Climate Occurring at high latitudes, therefore: • Climate is cold, with average annual temperature -5 to +5 °C • Rainfall is about 40 cm annually • Short summer growing season • Forest productivity is largely related to soil temperature

Climate Variation

Climate and climate variability is determined by: 1. Solar radiation 2. Chemical composition and dynamics of the atmosphere 3. Surface properties of Earth

Earth's Climate System

Climate exerts a key control over the functioning of Earth's ecosystems Temperature and Water Availability influence Plant Productivity, Decomposition, Weathering of Rocks

Tropical Forest Biome Climate

Climate in these areas show little seasonal variation with high yearly rainfall and relatively constant, warm temperatures. • High temperature (20-25°C) • High precipitation (>200 cm) • Low variability in both temperature and rainfall

Desert Biome Climate

Climate is variable • Hot and dry - very low ppt, extreme temperatures • Semiarid - very low ppt, moderate temperatures • Coastal - low moisture also due to sandy soils • Cold -low ppt, lower temperatures Extreme temperatures from night and day cycles High variation in day-night temperature No moisture in the air to backscatter sunlight No moisture in soils to hold in the heat... lost when sun goes down Cold deserts have marked seasonality Still low precipitation, but have climate variability

Temperate Forest Biome Climate

Climate shows high seasonal variation but temperatures and precipitation vary regionally • Hot, dry summers, cool, rainy winters • Moderate temperatures, rainy year-round • Moderate summers, cold snowy winters High seasonality Productivity limited by moisture in summer, by temperature in winter Deciduous trees - shed their leaves to conserve energy Leaves are ephemeral, not permanent structures

Comparison of Cloud cover over agriculture fields and native forested area

Clouds are over native landscape Native landscape has darker colour High albedo on flat, light, hot area on agriculture side (light reflected off the earth) Any moisture on agriculture is evaporating away, but on forested side it is condensed into clouds

Complex Adaptive Sytems

Complex Adaptive Systems (CAS): • Contain high diversity, many interactions and feedback loops • Are dynamic, and capable of changing • But have regular emergent properties (like stability)

Trophic cascades

Concept: Changes in the abundances of organisms at one trophic level can influence energy flow at multiple trophic levels.

Lecture 22

Conservation

Soil Food Webs

Consumers are not that important in terms of biomass, energy flow, or interaction effect strength on detritivores Microbes are 95% of the total biomass, and consume 95% of detrital energy Detritus is a donor-controlled system (bottom-up effects)

Consumption efficiency

Consumption efficiency is the amount of food ingested divided by the amount of prey/resource available (production) - going to be less than 1 usually... wont eat everything available to us - someone who goes to a buffet and eats more than you, has a higher consumption efficiency - how efficient are you at consuming

Desert Biomes

Cover ~20% of the Earth's surface Less than 50 cm/yr total precipitation Subdivision based on temporal variability in temperature: • Hot and dry • Semiarid • Coastal • Cold

What is the current concentration of atmospheric CO₂?

Current concentration = 400 ppm London = 430 ppm Pre-industrial revolution it was around 280 ppm - In 1 year we emit 10 billion tons of carbon

Rates of nutrient cycling

Ecosystem NUE = NPP / soil nutrient supply Ecosystem NUE therefore depends on two component indexes: (a) Plant-level NUE (i.e. NPP of individuals / unit nutrient) (b) Total uptake efficiency Effective uptake of soil nutrients: • Temporal partitioning • Spatial partitioning • Different nutrient ratios (ecostoichiometry) • Different nutrient forms

Watershed Streams

Different types of streams tend to appear in different parts of the landscape Level I is the initial integration of basin characteristics, valley types, and landforms with stream system morphology. Headwaters in mountains, high elevation, steep slopes - high flow rates, can be deep but in narrow channels = very linear channels As gradient get shallower, stream can widen, more affected by geology, parent material of rocks, shallower, wider Sediment taken with the fast flowing waters begin to build up, rivers start to meander "Braided type stream" sedimentation layers are non permanent F towards mouth forms larger deeper

Degradative succession Phases of Decomposition:

Degradative succession: Sequence of changes associated with decomposition processes Phases of Decomposition: - *Leaching* (Labile compounds used up) - *Fragmentation* (Recalcitrant compounds) - *Humification* (stable) Humus stability arises from: 1. Recalcitrance 2. Physical protection within soil aggregates 3. Substrate supply regulation

Tropical Forest Biomes

Delineated by tropics of Cancer 23.5N and Capricorn 23.5S Many forested areas in the tropics are not rainforests. Subdivision based on *rainfall*, *elevation*, and/or *substrate*: • Evergreen (rainforest) - no dry season • Seasonal deciduous - short dry period in a wet tropical region • Monsoon - alternating wet and dry seasons • Tropical cloud - persistent low-level cloud cover

Trade-offs during succession

Dichotomy of life history traits Trade-offs - you cant be good at everything Colonisation vs Competition

Ecological Succession

Directional change in species composition, structure, and resource availability over time that is driven by biotic activity and interactions, and/or changes in the physical environment.

Disturbance

Disturbance: A discrete event in time that disrupts ecosystem structure, changes substrate and resource availability and/or the physical environment. • Endogeneous - originates inside the system (e.g. pathogens) • Exogenous - originates outside the system (e.g. fire)

The 3 dominant controls over ecosystem processes:

Dominant control over ecosystem processes: Light Water Nutrients

Ecosystem Concept

Ecosystem Concept resulted from the synthesis of 3 different sets of ecological ideas: 1. Succession - directional change in ecosystem structure 2. Trophic interactions (niche concept, food webs) 3. Biogeochemistry - the biological influence on chemical processes

Emulating Natural Disturbance

END is based on the concept that forests, particularly the boreal forest - have evolved with, and are shaped by, natural disturbances such as fire.

Stages of ecological succession

Early/Pioneer Seral stage succession Climax stage

Earth's Radiation

Earth's radiation = energy from Earth and Earth's temperature Earth emits radiation and reflects solar radiation • Low energy emission (long wavelength) • The Earth's albedo (reflected energy) • The greenhouse effect (captured energy)

Ecosystem Nutrient use efficiency:

Ecosystem NUE: the ratio of net primary productivity to soil nutrient supply • *Unproductive sites tend to have high NUE* On limited nutrient sites, plants are more efficient - have higher nutrient use efficiency This however is a feedback system between nutrient availability, net primary productivity and nutrient release. Plants can increase nutrient use efficiency by increasing how productive they are, given the nutrients that are available to them Can increase this by putting the nutrients to a permanent use (ie: conifer needle) Structure needs to be protected, long lived, not very nutrient rich, non very edible At ecosystem level, there is a bit of a feedback - where everything is slowed down NUE can increase by: - Increased nutrient productivity - Increased tissue residence time Conifers have low nutrient, long-lived tissues (e.g. needles) Conifers typically occur on unproductive sites

Ecosystem Analysis

Ecosystem analysis seeks to understand the factors that regulate the pools (quantities) and fluxes (flows) of materials and energy through ecological systems.

Ecosystem services

Ecosystem services are resources and services derived from nature that bring benefits to humans that contribute to making human life both possible and worth living.

How does ecosystem-level NUE change with an increase in richness of species in a community?

Ecosystem-level NUE *increases* with an increase in the richness of species in a community

Productivity

Energy and carbon balance in plants; NPP across terrestrial systems

Geology and Soil Erosion

Erosion is caused by water or wind; can be exacerbated by disturbance Soil is detached, moved and re-deposited. Erosion by water: • Rainfall and runoff • Soil erodability • Slope gradient • Vegetation Erosion by wind: • Soil surface roughness • Climate • Unsheltered distance

Other Water Losses

Evapotranspiration Water losses from transpiration and evaporation Both are linked to vegetation structure Both require energy *Evaporation*: Water changing from a liquid to a gaseous state (water vapor). *Transpiration:* Evaporation from moist surfaces of plants (via stomata).

Midterm 1 Notes

Exam on Feb 2nd (Lectures 2 - 7)

Food webs

Food webs are better resolved at the 'top' (better resolved meaning we know more) We know more about predator species than low connections at the bottom 'plants' and 'detritus'

Role of Forests in Global Climate Change

Forests contribute to climate change through their influence on the global carbon cycle: they store large quantities of carbon in vegetation and soil exchange carbon with the atmosphere through photosynthesis and respiration release carbon into the atmosphere when they are disturbed become atmospheric carbon sinks during regrowth after disturbance Canada is a major player on international stage. Newer growing forests take up more carbon than old forests... So can forests be managed (locally) to alter their role in the carbon cycle?

Cornerstones in Ecosystem Ecology

Four foundational principles *Mass balance* - the mass balance of all elements are always conserved *Steady state* • Steady state is an ideal condition which permits comparisons *Limiting nutrients* • Organisms are always in short supply of something *Optimality* • Organisms are multiply constrained

Natural resource management

Frequently used when dealing with a particular resource for human use rather than managing the whole ecosystem. Based on how management affects quality of life for current and future generations (stewardship)

Changes in GPP and NPP across Biomes

GPP and NPP generally declines from tropics to the poles because of temperature and light limitations. Remember Gpp and Npp are driven by photosynthesis which is governed by enzymes with specific ranges in which they do best

Gradients and ecotones 2

Hill slopes from height-of-land (divide) to river Geomorphology Climate (precipitation) Soils input into system - precipitation some is intercepted by plants, some evaporates precipitation that hits surface can take a variety of pathways it can infiltrate the soil, it can be stored or can flow over land can then percolate though rock layer and onto groundwater layer

The Hydrologic Cycle

Is driven by solar energy Drives all other biogeochemical cycles The hydrologic cycle describes a series of processes by which water passes from the atmosphere to the Earth and back to the atmosphere Models can fuels discovery based research if mass balancing doesn't add up, we know we're missing something

Watersheds: The physical template

Geology - rock formations affect watershed Geomorphology helps explain river and watershed form Climate (precipitation, temp) affects hydrology in watershed

Green World vs Brown World

Green world when odd numbers of trophic levels Brown world happens when there is even numbers of trophic levels - boom bust system

Green World Hypothesis

HSS green world hypothesis was used to explain why plants are so ubiquitous in the world (world is green because there are so many plants) Theory talked about processes that regulated trophic levels They simplified trophic levels to construct the analogy Predators - no top down control on them - what limits their production is their resource availability and therefore their competition with each other for those resources Herbivores - limited by trophic interactions (top down predation) If herbivores are controlled by top down predation, this "frees" the trophic level below the herbivores Producers - are controlled by competition for light, nutrients, space Why is this model criticized? - over simplified (just 3 trophic levels) - plants do put effort into defenses to prevent herbivory - there are systems where plants are overgrazed

How to quantify an ecosystem?

Hard to do, but temporal and spatial scale is important.

Hubbard Brook Ecosystem Study

Historic Watersheds in Ecology They used watershed as a repeatable unit They subdivided replicates of watersheds and mass balanced the entire systems (water, nitrogen and phosphorus) The Hubbard Brook Ecosystem Study is a long-term monitoring and data management study that is still ongoing Export exceeded Input of most nutrients: 1. Absence of evapotranspiration lead to a 40% increase in stream discharge and accelerated leaching of soil nutrients. 2. Decoupling of decomposition and plant nutrient uptake in the watersheds. Increased decomposition, decreased plant nutrient and water uptake (because there are no plants), so combined increased stream flow and increased nutrient export out of the system Challenged the practice of clear cutting

Temporal scale and NPP

Hourly • Environmental drivers (ie sunlight, cloud cover) that govern rates of photosynthesis on an hourly scale Seasonal • Photoperiod - short days in winter, long days in summer • Temperature - enzymes are restricted by the cold Yearly • Changes in climate. - If this trend continues, some species are going to be pushed passed their thermal optimum. If species are pushed past this optimum, they are no longer maximizing the carbon in at the primary productivity level. Has a cascading effect if primary productivity is not the same Decadal • Shifts in species competition and disturbance - Extremes like wildfires (release a lot of carbon at the forest level), then have successional species come in. - A question of how often disturbances happen

Graph (Network) Theory

How patches are connected matters. Emergent properties from patch arrangement based on a network perspective (similar to food webs). 4 Types: a) regular/nearest neighbour - everything connected to nearest neighbour - not too far away b) Random; every patch has an equal likelihood of interacting c) Scale-free; more clustered d) Small-world - lots of nodes connected to nearest neighbour like first one, but every so often you have a longer distance relationship - patterns not about habitats, but natural networks - interactions of spatial patterns - emerging properties - Kevin bacon; six degrees of separation Most ecological (and other) networks are small-world. • exhibit low mean path lengths between any two arbitrary nodes and yet contains high clustering coefficients.

Forcing Function

Human population is viewed by many as the forcing function of global environmental change A forcing function is one perceived to be a cause of (responsible for, driver of) other changes. • New technologies, such a obtaining energy from the burning of fossil fuels • Advances in social organization allowing more effective exploitation of natural resources • Global dispersal capabilities

The global water cycle

Humans use and divert a lot of water from their natural purposes Anthropogenic Changes • Increased evaporation and precipitation • More extreme wet/dry • Land use change alters albedo effects Consequences of changes • Increased demands for fresh water (irrigation, household, municipal, industrial) • Impacts to aquatic ecosystems • Alterations in soil moisture

Watershed Function

Hydrological functions: Collection of water Discharge of water Storage of water can mass balance and parameterize the model can measure inputs and outputs Ecological functions: Provides diverse abiotic locations for chemical reactions Provides diverse biological locations (habitats) for flora and fauna

Implementing Ecosystem Management

International Union for the Conservation of Nature (IUCN) • Protected areas • Core reserves (based on SLOSS) • Habitat corridors • Buffer zones • Restoration areas

Measuring nutrient supply and limitation

Ion Exchange Resin Resin Capsule Anion/Cation PRS Probes all of these methods of nutrient measurements are only snapshots of the nutrients at one specific time - doesn't show rates

The Ecological Hierarchy

Individual (organism) Population (species) Community Ecosystem

Top-down vs Bottom-up

Individual efficiencies are what will determine whether top down or bottom up is stronger We can consider consumption, assimilation, other efficiencies green world hypothesis invokes both top down and bottom up controls they both happen at the same time Top-down processes dominate trophic dynamics Bottom-up processes determine food web structure

Keystone species Ecosystem engineers

Keystone Species - have a proportionally greater impact on the environment not related to population abundance Ecosystem engineers - make physical transformations in the environment

Spatial autocorrelation (Tobler's Law)

Locations closer together and more similar than locations further apart Distance decay plots Mantel Test

Differences in energy flow between Terrestrial and Aquatic systems

More standing biomass of autotrophs, detritus, and decomposers in terrestrial systems Aquatic - lower number of autotrophs in terms of biomass - a lot more of the autotrophic production goes into the herbivores than on terrestrial Terrestrial - more autotrophs - lower proportion goes to herbivores, lots recycled into soil system

LFH Horizon

L - Litter: accumulation of organic matter. Original structures are easily recognizable. F - Fragmentation: partly decomposed organic matter. Some original structures are recognizable. H - Humus: decomposed organic matter in which the organic structures are indiscernible.

Landscape and Restoration Ecology

Landscape ecology: focus on spatial patterns in landscape with particular emphasis on disturbance or land use change. Restoration ecology: application of ecological knowledge to the reparation of highly (and usually humanly) disturbed locales. (ie recovering from land use change back to natural grassland or forest system)

Where is the largest store of carbon? What form is it in (mostly)?

Largest store of Carbon is in the *air* (mainly in the form of CO₂) This is unavailable for use - To convert it to an organic state, plants use photosynthesis

Lecture 10:

Lecture 10: Foodwebs The aims of this lecture are to: Introduce trophic interactions and food webs (brief) Understand the energetics of food webs and secondary production Resources & Energy are limiting: • Resources increase productivity • Energy loss occurs through trophic levels

Lecture 8:

Lecture 8: Productivity The aims of this lecture are to: Understand plant productivity at several levels (leaf, plant, ecosystem) Understand the environmental controls on photosynthesis Understand the carbon balance of terrestrial ecosystems

Lecture 9:

Lecture 9: Nutrients *Plant growth (productivity) is limited by nutrient availability* Lecture goals are to understand: Plant nutrient acquisition, use, allocation and loss Plant-soil-microbe exchanges of nutrients How this is a key step in nutrient cycling in terrestrial ecosystems

River Continuum Concept

Longitudinal gradients along stream beds (River Continuum Concept) Depends on geomorphology > (narrow, fast steep vs. shallow, wide, slow) Incorporates nutrient inputs and 'spiraling' Influences the benthic invertebrate communities Differences in resources, nutrients, biotic entities as you head down from headwaters organic material downstream are more fragmented changes in feeding groups *shredders and collectors dominate* *then more grazers and collectors* *then collectors dominate*

Sustainable Forest Management

Management that maintains and enhances the long-term 'health' of forest ecosystems for the benefit of all living things while providing environmental, economic, social, and cultural opportunities for present and future generations. Forest Stewardship Council An international certification and labeling system dedicated to promoting responsible forest management of the world's forests. The number of FSC certified forests has grown by 191% in the past five years. • 34% of Canada's certified forests are FSC-certified • 1/3 of the world's FSC-certified forests are in Canada

How do we measure GPP?

Measure photosynthesis and respiration in both light and dark environments Tests in Light: In light, plants photosynthesis and respire. These 2 processes produce opposite substances so you can't really parse the two processes out. That means you are measuring the NPP. Test in Dark: In the dark, plants only undergo respiration (They can't photosynthesise in the dark) Then use the formula (NPP = GPP - Rp) to find the GPP

How do we measure NPP?

Measure the rate of increase of plant biomass (rarely considers belowground, herbivory, etc.) Measure the rate of photosynthesis: • The amount of carbon dioxide used • The rate of sugar formation • The rate of oxygen production

Most powerful greenhouse gas

Methane What hets the earth isnt the sun... its greenhouse gasses retaining the energy

Moisture

Moisture has many other things affecting it proximity to water, the temperatures around that water (whether it will precipitate), the effects of rain forests (they act like their own bodies of water)

Where does carbon go?

Most energy is located to the roots (about half) How a plant allocates its carbon will dictate how and where it will survive - tradeoff of providing energy to leaves or roots Just measuring the biomass aboveground does not reflect the total plant productivity • Plant loses Carbon from herbivory and such Energy is measured in tons of carbon per hectare per year - temporal aspect important Always a unit of area and time

Mycorrhizal Benefits

Mycorrhiza mineralize nitrogen Mycorrizhae are fungi, which spread out and their mycelium branch like crazy - they are heterotrophs which feed on dead decaying matter and make it bioavailable Plants then take advantage of this relationship and have 2-3 fold increase of surface area for nutrient availability Small diameter of hyphae (0.01 mm) allows plant to explore larger volume of soil But the plants also need to provide the fungi with carbon (trade off) but plants have lots of carbon so whatever It is suggested that up to 20% of net primary productivity actually goes towards supporting the mycorrhizal association

Nitrogen Fixation

N2 gas to biologically available forms (NH3) Occurs through three processes: • lightening strikes • industrial Haber-Bosch process • biological N fixation (nitrogenase enzyme)

Net Biome Exchange (NBE) or Net Biome Production (NBP):

NBE or NBP: refers to the change in carbon stocks after episodic carbon losses due to natural or anthropogenic disturbances have been taken into account

Which is stronger: 1. Negative effects of predation on prey 2. Positive effects of feeding for predators

Negative interactions are stronger than positive ones due to energy loss with trophic transfer efficiency

Net Ecosystem Production (NEP)

Net Ecosystem Production = is the net amount of primary production for the whole ecosystem after the costs of respiration by plants, heterotrophs, and decomposers are all included. *NEP = GPP - (Rp + Rh + Rd)* or *NEP = NPP - (Rh + Rd)*

Net Primary Productivity (NPP)

Net Primary Productivity = what you're left with once you calculate the carbon in (GPP) and carbon out (Respiration) by plants *NPP = GPP - Rp* - This is *primary*, so we dont consider the heterotrophs and decomposers yet - Amount of NPP translates into biomass (plants using the incoming carbon to convert it to biomass) - To measure this, you can measure the increase in plant biomass (difficult to measure because of the significant below ground biomass)

Lecture 21:

Nine variables of high importance to habitability of Earth: 1. Climate change 2. Ocean acidification 3. Biodiversity loss 4. Atmospheric aerosol loading 5. Stratospheric ozone layer 6. Chemicals dispersion 7. Freshwater consumption and the global hydrological cycle 8. Land system change 9. Nitrogen and phosphorus inputs to the biosphere and oceans We have already exceeded capacity of the earth in terms of: - Biodiversity loss - Climate Change - Nitrogen Cycle (biogeochemical flow boundary)

What happens when N, P, K are limited

Nitrogen Limitation - stunted growth - yellow leaves - reductions in yield Phosphorus - reduced growth rate - reduced yields of products - reduced reproductive products (ie: fruits) Potassium Limitation - looks like it has been scorched - important for water balance

Aquatic Aspect of Watersheds

Non-terrestrial... Biomes are for terrestrial environments; repeatable units The biome concept is different for aquatic systems Doesn't work as well for aquatic systems because there are more than 2 axis (not just temp/precip) Temperature is tied closely to depth Still has repeatable "concepts" though *Littoral Zone* - closest to shore - light penetration - rooted aquatic or semi-aquatic plants - high vegetation, primary productivity *Limnetic Zone* - stratified upper part - light penetration for photosynthetic organisms - stratification of nutrients, temperature *Benthic Zone* - sediments

Lecture 12:

Nutrient Cycles

Savanna Biome

Often considered a Tropical Grassland. Sometimes considered an open forest. Here I will differentiate between savanna and grasslands (with and without trees) Graminoids (grasses) are main vegetation Sparse trees Savannahs have sparse trees but are still grassland-like True grasslands have no trees

Surface run-off and soil infiltration

On the ground, liquid water can either infiltrate the soil or run-off on the surface Surface run-off depends on: • Soil texture • Soil moisture content • Slope of terrain • Vegetation / litter Runoff on the surface - steeper slopes have more runoff because it doesn't get into the soil Soil texture (ie hard packed calcrete) has a significant effect on whether the water can infiltrate the surface Soil moisture - If saturated, then infiltrative ability of water is inhibited

Production efficiency

Production efficiency: the amount of consumer production divided by the amount of assimilation - Energy that is assimilated might not actually become biomass - Amount of biomass increase divided by amount of assimilation - high metabolism people are inefficient at putting on biomass because of metabolic costs - low production efficiency

Optimality

Organisms face simultaneous constraints Organisms, facing multiple environmental constraints, must balance resource use. Organisms must 'act' optimally Evolutionary Stable Strategies, Optimal foraging strategy etc. Cost/Benefit ratios

Lecture 5:

Other terrestrial biomes: • Desert • Savanna • Grasslands • Tundra

Aboveground inputs to Soil Organic Matter

Over 90% of what happens aboveground ends up falling and becoming a part of the the soil system Coniferous is contributing the same amount of litter (just gradually over the year) compared to deciduous which is all at one time pretty much (Fall)

Productivity-Diversity Relationship

Productivity-Diversity Relationship is essentially the idea of different plants doing different things in different ways which maximizes things through complementarity

PCNM - principal coordinate analysis of neighbor matrices

PCNM - take spatial information (ie lat/long) and use it to talk about spatial relationships among locations - talks about dissimilarities - quantifies distances between separate locations Things that are close together are more important to know exactly how close they are really far away things are just far away who cares then use spatial information and environmental information and see patterns would never do this with global data Essentially Toblers law?

4 Soil Vegetation Impacts on Down-Slope Processes

Patterns in vegetation follow soil characteristics (including moisture), but also alter the physical down-slope processes: 1. Interception of precipitation 2. Root uptake and evapotranspiration 3. Root structure - holds surface soil and prevents erosion 4. Surface vegetation slows velocity and catches sediment

Photosynthesis

Photosynthesis provides carbon/energy that drives nearly all biotic processes Controlled by: • Leaf: availability of water, nutrients, temp, light, CO2 • Ecosystem: growing season, leaf area • Both are also ultimately controlled by availability of soil resources, climate, and time since disturbance Inputs of carbon to ecosystems are based on photosynthesis Photosynthetic plants synthesize carbon-based energy molecules from the energy in sunlight.

Interception, stemflow, and throughfall

Physical characteristics of foliage and type of precipitation play a role in how much water reaches the land surface Stemflow and throughfall transport nutrients from the canopy to the soil. Example: potassium transport in throughfall greatly exceeds that in litterfall When water hits surface, it can evaporate back up (from ground, or vegetation surfaces) in deserts rain can evaporate even before it hits the surface *Throughfall hits vegetation and falls off* *Stem flow moves down the stem* how much of each depends on type of vegetation trees have more stem fall than a blade of grass when water moves down the vegetation it picks up dust and nutrients potassium a major one more nutrients from stem fall than leaves falling?

Potential vs Actual Evapotranspiration

Potential Evapotranspiration (POTET; PET) - the rate of water loss from the free water surface under given weather conditions. (Potential meaning if water is unlimited, how much evapotranspiration can happen) vs. Actual Evapotranspiration (ACTET; AET) - the amount of evapotranspiration that does occur given water availabilities. During summer months PET is highest, because temperature is high, but so is the potential for water shortage

What do plants need?

Primary Nutrients (macronutrients) - *Nitrogen* (for proteins) - *Phosphorus* (phospholipid fatty acids) - *Potassium* (structural components and water balance) Numbers on fertilizers refer to abundance of the primary nutrients N:P:K (ie: 30 : 8 : 14) Secondary Nutrients - required in large amounts, but not usually limiting in the environment Micronutrients - also needed but not limiting in the environment

Primary Productivity and Global Change

Recent evidence suggests that terrestrial NPP may be declining in response to global warming and accompanying drought • Global change encompasses more than just warming of the earth (climate and precipitation patterns) Forest is essentially a stock of carbon (stored in tissues, roots and organisms) As climate shifts (temp and precip), the productivity of the forest shifts and therefore affects the species composition of the ecosystems If plant species are less efficient, less energy is there for species up the food chain As we see increases in temperature and changes in precipitation patterns, we can follow it in changes in composition of forests and energy transfer of carbon

What determines number of trophic levels

Relatively low number of trophic levels • Nearly all food webs have maximum food chain lengths of 5 or less. • Most common maximum food chain length is 4 Energy Flow Hypothesis is why - 10% energy loss

Relay Floristic Model vs Initial Floristic Model

Relay - Clements Change to completely different communities all predetermined to be together Early species facilitate the colonization of later successional species Later successional species inhibit early successional species Initial - Egler - same pattern, not because of communities come in over time, but because they're already there - found that most of the species we see over successional species exist there as seed stalks or rhizomes that we don't see there yet - Species tolerate each other until they overtake them Difference between them - Timing of immigration (already there vs coming in at same time) - importance of sequential changes to environment

Respiration

Respiration is the amount of CO₂ that is lost from an organism or system due to metabolic activity Rp = Plant respiration Rh = Heterotroph respiration Rd = Decomposer respiration (the microbes) Plants also need O₂ for energy to breakdown CO₂ At ecosystem scale we need to consider respiration by plants, heterotrophs and by decomposers Decomposition (by microbes) is a heavy producer of CO₂

Richness Abundance Relative Abundance Evenness Community Composition

Richness = number of different species Abundance = the number of individuals Relative abundance = the proportional abundance of a species (# ind. sp. A / total # ind. in community) Evenness = the distribution of relative abundances Community composition = a description of who and in what abundance

Relationship between Ecosystem Function and Biodiversity

Rivet Redundancy Proportional Loss If all species were functionally unique = Linear Immediate Catastrophe If only particular species matter

How do plants obtain nutrients? (3)

Roots are small part of soil volume (1%) and have to come in contact with nutrients to take them up Small root hairs primarily responsible for the uptake. Three ways to obtain nutrients (all three in constant operation): *1. Interception* - Roots grow and explore new soil areas and encounter new nutrients in that soil system *2. Mass Flow* - Nutrients dissolved in capillary water (available for plant use). - Evapotranspiration occurs at top of plant, creates a suction through plants body, and the water is drawn in towards the root surface from the soil and nutrients absorbed along with it *3. Diffusion* - nutrients in high concentration in solution within soil water move from an area of high concentration towards an area of low concentration (surface of roots)

Soil Organic Matter

SOM is the organic constituents of soil (live and dead) - largely comes from the aboveground system (as detritus). Soils contain carbon in both organic and inorganic (e.g. carbonates) forms. In most soils, the majority of C is held as soil organic carbon (SOC), which can be live or dead. We just say 50% of SOM is Carbon We used LOI in lab (Loss on ignition) to measure soil organic carbon *Living organisms: <5%* microbes, nematodes, earthworms, arthropods, living roots, etc. *Fresh inputs: <10%* plant, animal, or other organic substances. (Litter) *Active fraction: 33-50%* undergoing decomposition. (Fragmentation) *Stable component: 33-50%* humic components. (Humus)

Boundaries

Serpentine soil outcrops: • low calcium-to-magnesium ratio • lack of essential nutrients (N, P, K) • high heavy metal concentration

Diversity- Stability Relationships

So ecosystem stability comes as a result of instability of populations This concept also relates to functional redundancy

Soil

Soil (the soil) - the material itself, it's organic and inorganic components 25% air 25% water 45% mineral particles 5% Organic Matter (organisms, roots, humus) Soils - a natural body with a specific composition such as sand, clay, and/or loam Soil type - a category of soil produced by a specific set of soil-forming factors (e.g. a Podsol or Podzolic Order)

Local carbon cycling

Soil Respiration and Net Photosynthesis almost mass balance- But overall there is a net carbon sequestration On average 80% carbon in an ecosystem is stored belowground, only 20% aboveground Boreal systems have highest overall carbon stocks

Tundra Biome Soils

Soils • Form very slowly and are poorly drained • *Permafrost*: permanently frozen ground (1-2 m) consisting of mainly gravel and finer particulates • *Cryoturbation*: soil movement that arises from frost action Soils form very slowly, very slow decomposition, productivity of the system is even lower though, poorly drained soils due to permafrost Lost of moisture accumulation in some areas Lots of freeze-thaw cycles

Desert Biome Soils

Soils • Generally little to no organic matter • Mineral soils are typically dry (obviously), with good drainage and high salt concentrations Little or no plant biomass; is none deposited into the soils Since organic matter significantly helps with retaining moisture in soil, soil is poor at retention Highly mineral soils Good drainage, high salt conc. - this affects plant productivity Natural concrete *Calcrete* forms where calcium carbonate hardens Due to this concrete, water will just run off - also contributes to good drainage and poor moisture retention

Lecture 18:

Stability

Tropical Forest Biome Soils

Soils • Highly variable • Typically characterized by significant leaching and poor nutrients • High rate of decomposition Soils are poor High precipitation = lots of leaching, less nutrients available More homogeneous soils Shallow organic material on top layer Organic material on soils don't stay there when they die Very fast decomposition due to temp and precip Vines, lianas are epiphytes (epi = on, phyte = plant) They acquire nutrients before they hit the forest floor Buttress roots shoot out and form network right at soil surface to maximize soil nutrient absorption

Grasslands Biome Soils

Soils • Nutrient-rich from many-branched grass roots • Little leaching, high soil fauna • *Chernozem*: fertile, black-coloured soil with high humus in Canadian prairies Temperate zone - moderate temperatures, slower decomposition, great growing season temperature/precipitation, lots of vegetation Therefore lots of organic matter deposited on/in soils Fine root systems of grasses help to support soils (very little soil erosion) These roots are ephemeral roots (short-lived, constant growth and deaths) Root biomass in soils are nutritious and contribute to the high organic matter in the soils Very dark soils Humus - highly organic, highly degraded soils- highly sought after for growing

Boreal Forest Biome (Taiga) Soils

Soils • Tannins cause the upper soil layers to become very acidic • Highly leached - podzolisation (podsols) • Peaty wetlands where surface drainage is impeded by permafrost • Mycorrhizal associations are important (symbioses between plant roots and fungi) • Slow decomposition • Nutrient poor Short tree lifespan (80 yrs) Cone shaped trees, retain moisture, don't shed their waxy leaves. Needles - highly conservative structures, produce secondary metabolites, polyphenols, waxy, slow growing Upper layers in boreal system are highly acidic Highly water logged or leached soils, especially in permafrost soils Any moisture is trapped at surface Carbon is retained in soil system Productivity is greater than decomposition Highly organic soil that isn't being decomposed Our boreal forests store lots of carbon Boreal stores more than both tropical and temperate forests combined

Savanna Biome Soils

Soils are diverse and similar to other grasslands... Typically porous, with rapid drainage of water (low water holding capacity). Soils are porous and highly mineral Can have a hard impermeable crust As such, areas with greatest wet season rain tend also to be the most infertile. Low water holding capacity for soils Low rain throughout the year When rains do come, it leaches the soils Therefore soils rather infertile

The Energy of Ecosystems

Solar energy powers all plant physiological and physical processes. A large part of solar energy drives the hydrological cycle Only a small fraction of solar energy is used in biological reactions Photosynthetically Active Radiation (PAR) - not the energy of the wavelength but the absolute number of photons

Solar Radiation

Solar radiation = energy available to drive the climate system Solar radiation absorption is uneven in both space and time -> seasonal variation in climate. • Earth's elliptical rotation around the sun • Earth's off-spherical shape and tilted axis • Earth rotating at 23 degree angle

Can We Predict Tipping Points?

Somewhat (and it involves lots of math): *Critical slowing down* • Slowing rate of return from perturbations • Increases in the variability of a system • Increased autocorrelation Problematic because: • high-resolution time series are required

Variation in NPP across Space

Space is easier for us to see ie different forest types in different regions (here we are in a southern carolinian forest) Changes is space dictate what kind of species can grow/if they can grow at all Then dictates the level of productivity (certain species can photosynthesis better than others) Latitude If we look at latitude gradient, equator is most diverse and productive Increase latitude, decrease in biodiversity (less productivity in general) Longitude (East to west gradient): There are general reduction in precipitation levels in North America from east to west Solar radiation differences exist as well which alters the amount of sun gets absorbed So we have temperature, precipitation, and solar radiation gradients Gradients over space and time are important

Lecture 15

Spatial

Gradients and ecotones

Spatial autocorrelation (Tobler's Law): Locations closer together are more similar than locations further apart (Legendre 1993). Species composition of communities are more similar when communities are close together than further apart. Gradient of abiotic factors in streams through space (or time) Can talk about how similar areas are based on absolute distance Distance decay model Things start off very similar, as distance increases, similarity of abiotic conditions will decrease

Species Abundance Distributions (SADs):

Species Abundance Distributions (SADs): High proportion of species with only one individual - (singletons). X-axis is abundance Y-axis is the number of species with that abundance Few common, many rare

Stakeholders

Stakeholders are individuals or groups of people who are affected by environmental decisions and actions. • May have power to influence the outcomes of environmental decisions Four main stakeholder groups: • Stakeholder who may benefit (beneficiary) • Stakeholder who is negatively affected (burden) • Stakeholders who directly impact (e.g. landowner) • Stakeholder who indirectly influences (e.g. decision maker)

Water movement through plants

Stomata: pores in the leaf surface that open/close to regulate CO2 and water ~10 % of atmospheric moisture is released by plants through transpiration Stomata open on leaves allows for gas exchange for gas exchange to occur When stomata are open, water evaporates When water evaporates, it draws water up from the roots (cohesive forces) Evaporation causes suction which enables flow of water in plants

Strategic management

Strategic management encourages the establishment of goals that will benefit the ecosystem while keeping socioeconomic and politically relevant issues in mind. • keeps stakeholders involved and relies on their input • high level of importance on evaluating and reviewing

Unique Properties of Water

Strong forces of attraction between molecules of water Water exists as a liquid over a wide range of temperatures All three phases (gas, liquid, solid) occur within standard Earth's temperature and pressure regime Water expands when it freezes (why?) Liquid water changes temperature slowly (high specific heat: 1 calorie/gram °C = 4.186 joule/gram °C ) It takes a large amount of energy to change the temperature of water Water, around 4 degrees, stops shrinking? and begins forming a crystalline structure Takes a large amount of energy to change water temperature

Temperate Forest Biomes

Subdivision based on *tree type* and *rainfall*: • Temperate coniferous, mixed wood, or deciduous • Mediterranean forest/scrub • Temperate rainforests

Resource-Ratio hypothesis

Succession is a result of turnover in the identity of competitively dominant species along a *soil-light resource ratio gradient*. The resource-ratio hypothesis assumes that each plant species is a superior competitor for a particular proportion of the limiting resources.

Savanna Biome Biota

Tall grasses with sparse trees and shrubs Large herbivores and predators Predator - prey interactions are drivers of community dynamics Large herbivores in open system What are some adaptations for living on the savanna? To avoid predation herbivores stay in groups (herds), camouflage, group characteristics, migratory (herbivores following resources, predators following prey) Very classic predator prey dynamics seen here

Ecosystem Concept - Tansley (1935)

Tansley (1935) "an ecosystem is an integrated system composed of interacting biotic and abiotic components" Much of modern science at the time was focused on the parts: mechanistic, reductionist New placement of emphasis on the whole: holistic, emergent properties shift from looking at objects, to the relationships between the objects reciprocal interactions when we look at whole instead of sum of parts, we find a whole different level of patterns called emergent properties (more abstract concepts like stability and resilience). These emerge not because of organisms interacting, but because of HOW these organisms are interacting with each other

Grasslands Biomes

Temperate grasslands are N/S of 23.5° Areas of high human activity including agriculture and livestock grazing. Prairie: grasslands with tall grasses (Canada) Steppe: grasslands with short grasses (Asia) More seasonality in temperate zone These areas are intense human development areas; highly populated areas Grasslands under huge pressure from agriculture and animal grazing

Lecture 16:

Temporal

Terrestrial Biomes

Terrestrial biomes are distinguished primarily by their predominant vegetation, which are mainly determined by *temperature* and *rainfall*

Thames Watershed

Thames valley watershed watershed is really scale dependent... anything that happens upstream, affects the downstream area in emborough (tiny circle) they don't care about what happens it Perth but London is affected by both emborough and perth upstream effects lots of smaller watersheds embedded in others = nested design we can use smaller watersheds act as replicates

The Green Revolution Why did it end?

The Green Revolution = the period of time about technological advance and commercialization of agriculture - increasing need for increasing food yield (grain yield increases with an increase in fertilizer use) Greed revolution ended. Why? We realised that all these technological advances had consequences ecologically and in terms of productivity Reasons: - plateau of benefits (productivity was saturated) - lots of soil erosion and nutrient losses from widespread use of these chemicals - we shifted into a different type of green revolution - non-target biodiversity losses due to nondiscriminant pesticides like DDT Insects (and many pollinators) were dying Bioaccumulation of DDT up the food chain Birds and insects dying carcinogenic to humans too

Intermediate Disturbance Hypothesis

The IDH predicts that diversity will - reach its maximum at intermediate levels of disturbance - remain low at high and low levels of disturbance. Balance between who is good at colonization vs competition Unimodal relationship

Lecture 6:

The aims of this lecture are to: Introduce terms and concepts associated with watershed ecology. Describe typical watershed structure and how watersheds work, at different geographic scales and through time. Provide related examples of contemporary issues in watershed ecology. Mainly a terrestrial environment but also contains aspects of aquatic environments

The amount of SOC depends on:

The amount of SOC depends on: Input rates • Root biomass • Litter deposition Output rates • Decomposition rates • Leaching / erosion

Four Fundamental Ecological Processes of Ecosystems

The four fundamental ecological processes of ecosystems are: 1. The Hydrologic Cycle 2. Energy Flow 3. Biogeochemical (or Nutrient) cycling 4. Community Dynamics (i.e. how the composition and structure of an ecosystem changes)

Soil Catena

The soil catena is a sequence of soil profiles on a downhill slope *Plateau Zone* - flatter, waterlogged; peat develops on acidic waterlogged soil *Zone of Eluviation* - leaching occurs here *Zone of Translocation* - Water moves faster; thinner, less acidic soil here *Zone of Illuviation* - areas where nutrients, sediment accumulate; waterlogged; peat develops on acidic waterlogged soil

Forest Terrestrial Biomes

There are four major types of forests, classified (mostly) according to *latitude*: • Tropical • Temperate Rainforest • Temperate Deciduous • Boreal/Taiga

Scales of Disturbance (regimes)

Time scale: • Duration - how long a disturbance affects the community (press vs. pulse) • Frequency - how often an ecosystem is disturbed. Spatial scale: the spatial extent of the impact relative to the size of the landscape Intensity: the strength of the disruptive forces; typically measured by the proportion of total biomass, or population of a species is killed by the disturbance.

Tipping points have at least one of the following characteristics:

Tipping points have at least one of the following characteristics: The change becomes self-perpetuating. There is a threshold beyond which an abrupt shift of ecological states occurs. The changes are long-lasting and hard to reverse. Time lag between the pressures driving the change and the appearance of impacts.

Top 3 Anthropogenic contributions to the Climate Change

Top 3 Fossil Fuels - 7.6 Land Use Change - 1.5 Cement - 0.1

Ecosystem Use trade-offs

Traditional dichotomy of land management lead to large trade-offs; trade-offs still exist under new model of management Natural ecosystem vs. Intensive cropland vs. cropland with restored ecosystem services need to think about ecosystems - not in terms of short term gain at the cost of long term - and think in terms of sustainability

Trait

Trait: any measurable feature of an individual that potentially affects performance or fitness. Environmental change alters trait distributions through response traits. The correlation between response and effect traits will dictate the degree by which changes in biodiversity will manifest at the ecosystem level.

Why is Primary Production so important?

Transfer of energy from the most abundant source (inorganic CO2 in the sky useless to most organisms) down through plants into organic Carbon, available Primary productivity of an ecosystem = transfer from abiotic to biotic Plants use energy for their own growth and reproduction and convert energy into biomass Herbivores then eat plants Predators eat herbivores and so on and so on Every level you scale up you have to subtract the carbon expenses - leaves us with net ecosystem productivity

Nutrient cycling

Two hypotheses: Nutrient cycle 'tighten' as cycling within the system increases The ratio of output to input decreases and then equalises following a pattern of net ecosystem production (NEP)

Keeling curve Explain the patterns

Two main trends: 1. Atmospheric CO₂ as a whole is increasing 2. Zigzag shape due to seasonality - More land mass in the northern hemisphere than southern hemisphere - most of the plants are in the northern hemisphere - seasonality in the northern hemisphere largely dictates this seasonal zig zag pattern - In the winter, carbon isn't being drawn down from the atmosphere as effectively

Trophic pyramids

Typically the numbers and biomass of organisms decrease as one ascends the food chain

Primary Productivity Over time

Unimodal NPP, plant respiration, and GPP Increasing plant biomass and mortality larger trees aren't growing as much, less growth

Using stable isotopes to estimate trophic position of soil animals

Using stable isotopes to estimate trophic position of soil animals • δ15N estimates the relative trophic position • δ13C estimates the relative niche width

Command and control management

Utilizes a linear problem solving approach where a perceived problem is solved through controlling devices such as laws, threats, contracts and/or agreements. • A top-down (authoritarian) approach Examples of where it has been applied: • the use of herbicides and pesticides to safeguard crops • the culling of predators in order to obtain larger, more reliable game species • the safeguarding of timber supply, by suppressing forest fires

Lecture 7:

Water (& Energy) The aims of this lecture are to: Understand the hydrologic cycle and the main components of the water balance in an ecosystem Understand the importance of water in ecological processes Understand how energy budgets drive hydrologic processes

Water Losses at the Soil Level

Water losses from soil through: surface runoff (saturation or low infiltration) High gravitational water (percolation) to groundwater Water lost through transpiration Plants absorb the water and undergo evaporation, transpiration, evapotranspiration

What are the boundaries of an ecosystem?

We are interested in nutrient movement so its not always clear where the boundaries are: Ie; Plant is both in the water and out Frog lives both in the water and outside Different lifecycles of species can occur in different areas (dragonfly; in water and out) Essentially a whole ton of nutrient cycling. Pretty much every system in nature is an open system which has energy/material move in and out of the system

Effects of Human Activities

We as humans divert a lot of water We alter the water cycle by: Withdrawing large amounts of freshwater from the cycle Clearing vegetation and eroding soils Polluting surface and groundwater Contributing to climate change

Boreal Forest Biome (Taiga)

Why is it only found in the Northern Hemisphere? Not much land mass in southern hemisphere for it What dictates where it ends? Tree line, where physiological boundary of where trees can survive (mostly related to temperature)

Geology and soils

Within a given climate regime, soil properties are the major factor governing ecosystem processes. Soils are formed... • Physical and chemical properties of rock • Weathering • Biotic activity (chemical - ie detritus deposited into the soil system) • Biotic contributions And soils are lost... • Erosion

Is there an Upper Limit to Primary Production?

YES • Upper limit to primary production exists because of: -> Nitrogen (this affects the speed of enzymes because they are made of nitrogen) -> Water (photosynthesis requires H2O and nutrients) Different parts of the earth at different times have different relative abundances of these limiting elements

Multiple drivers of change (anthropogenic)

land conversion is most significant threat to ecosystems by humans climate changes

Decomposition

is the biological, physical and chemical breakdown of organic material • Releases nutrients for plant growth • Provides energy for microbial growth (heterotrophs) • Major pathway for C loss from ecosystems • Influences ecosystem C storage

The Anthropocene

new epoch of geologic time Anthro = human Cene = new

Tropical Forest Biome Biota

• Tropical forests are characterized by the greatest diversity of species. • Net primary productivity ranges from 2-3 kg m^-2 y^-1 or higher. • The tropical forest biome is estimated to contain over half of the terrestrial species on Earth How can the most productive forests in the world occur on soils of extremely low fertility? Why is biological diversity concentrated in the tropics? *Steady state* - at low nutrient level, high input can occur if there is also high output/uptake of those nutrients When we measure soil nutrients and fertility we see it is low, but we only see a snapshot... We can't see the *rate* of nutrient cycling. The rates are high! Why biological diversity in tropics? (latitudinal gradient) - it is oldest; more time to accumulate species - energy coming in is higher - null hypothesis (artefact of being large in area) ... there is no definitive answer

Pools and Fluxes

• 4 major pools: atmosphere, ocean, soil and vegetation, rocks and sediments • The atmosphere is the smallest and most dynamic pool (5 yr turnover time) • Ocean is mostly inorganic (bicarbonate) • Terrestrial is largest biological store • Carbon in rocks is >99%, but cycles slowly • Most of Earth's water is in Ocean (96.5%), ice caps and glaciers, and ground water • Only a tiny fraction of Earth's water is in soils (~0.01%) • Water in the atmosphere ~2.6% of the annual cycle with an average turnover time of 10 days

Clements vs Gleason

• Clements (1916) - deterministic and predictable • Gleason (1926) - random and unpredictable Both observed a pattern over time - a directional change following disturbance

Indeterminacy of food webs

• Complexity - there are many, many nodes and links • Time lags - effects don't show up until the interactions flow through many intermediate species • Unpredictable behaviour - Trait-mediated interactions, ecology of fear, ecosystem engineering

Factors affecting stability

• Disturbance frequency and intensity (last lecture) • Species diversity, interactions, and life history strategies (this lecture) • Trophic complexity, redundancy , and food web structure • Rate of nutrient or energy flux (feedbacks among hierarchical levels)

Lecture 2:

• Ecosystem Concept • Ecological Hierarchy • History of Thought • Structure of Terrestrial Ecosystems

Temporal scale:

• Instantaneous (sec) • Seasonal (monthly) • Successional (10-100 years) • Evolutionary (100s - 1000s years) • Geologic (millenia)

Lecture 4:

• Introduction to the Biome Concept • Terrestrial Biomes - General • Forest Biomes of the World • Forests in Canada

Rivet hypothesis

• Loss of species is compensated for by other species with a similar function. • System is relatively insensitive to changes in diversity. • Functional groups are important • Species within groups are redundant. Rivet hypothesis: species are like rivets holding together a machine: *threshold failure*

Types of interactions

• Predation/herbivory/parasitism (+/-) • Competition (-/-) • Amensalism (0/-) • Mutualism (+/+) • Commensalism (+/0)

Temperate Forest Biome Soils

• Soils strongly influenced by aboveground vegetation type • Distinct organic layer (Litter, Fragmentation, Humus) • High fauna biomass • Generally fertile Layers of soils with distinct horizons - distinct litter (leaf) layer - subsurface layer (mixed organic and mineral layer) - done by worms? Most sought after soil = top layer - fragmentation litter - Humus = well decomposed organic material Highly organic = lots of space, nutrients lots of diversity in soils Highly fertile soils

Stability and Resilience

• Stability - the ability of a system to return to an equilibrium state after temporary disturbance • Resilience - a measure of the persistence and ability to absorb change and disturbance

Why does increasing the number of species increase functional redundancy and the resulting ecosystem stability

• The Sampling Effect: A greater chance of including a species of greatest inherent productivity in a plot that is more diverse. • Complement: Plant species coexistence is thought to be the result of niche partitioning, or differences in resource requirements among species. - asynchrony of species' intrinsic responses to disturbance - differences in the speed at which species respond to disturbance • Facilitation: Mechanism whereby certain species help or allow other species to grow by modifying the environment in a way that is favorable to a co-occurring species