Forest Ecology Exam 2

Effects of fire on composition

-Fire regimes and fire suppression. -E.g. Battlement Mesa Forest Reserve and Grand Mesa and Gunnison National Forest -actual map reconstructed disturbance history to. -What tree construction looks like, gradually replacing aspen. -How we can use historic maps and tree ring info to make inferences about the area.

Difference between stand structure and ecological succession

-Stand structure is the distribution of trees by species and size within a stand. The structure is the result of several factors: Growth habit of the tree species, especially the degree of shade tolerance. -Ecological succesion describes what happens over time to species composition. (how it changes after a disturbance) -A stand structure is more general terms.

(d.) Some mutual exclusion, no obvious associations of species in different layers

-Similar to relationship in (c.) but with more broadly overlapping ranges of species with any layer. -There is some degree of mutual exclusion within a layer but no obvious associations of species in different layers.

K-selection

-Species in a more predictable and uniform environment with high levels of inter and intraspecific competition. -They are selection to produce fewer, but larger offspring with greater competitive abilities. -The K is the same K as carrying capacity but is associated with more stable populations.

Micro topography

-This is the surface features of an area, or material which can also tell us the HRV. -E.g. Fallen logs are oriented in the same direction which is the opposite way of the way the trees that are still growing. In conclusion, it is possible that the area was effected by wind disturbance.

Primary succesion

-This is when succession begins in environments that lack organic matter and that have not yet been altered in any way by living organisms. -Sites where that was not previously vegetated or all sources of vegetation have been removed. -E.g. lava flow that covers and eliminated seeds, or glacial retreat: may have been vegetation before, but there is no more remnants of the vegetation. Severe fires could also cause this.

Regeneration Niche

-This refers to the sum of everything a plant needs to establish and to grow. -Environmental conditions are susceptible to growth. -Example of regeneration niche: there is more regeneration closer to rocks and fallen logs because they modulate temperature and protect against wind. -Regeneration on top of fallen logs is different depending on moisture and dryness.

European association concept (concerning species distribution)

(1.) The individual species in the association are, to some extent, adapted to each other. (2.) The association is made up of species that have similar habitat requirements. (3.) The association has some degree of integration.

Seral

-A seral community (or sere) is an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community. In many cases more than one seral stage evolves until climax conditions are attained.

Population vs. community

-Groups of similar organisms vs. groups of dissimilar organisms. -A population is a group of a member of species living in a specific area.

Advantage of this climax theory

-It doesn't require discrete units. -It recognizes space over time and continuous change (this is closer to reality). -Landscape consists of environmental gradients. -There is a movement away from trying to think of ecosystems as superorganism and looking more at patterns or process.

Life table

-This provides a summary of the schedule of deaths in a population and has the causes of mortality in each age group. -The number of survivors at the start of each age interval.

(a.) Steep environmental gradients

(a.) Walking through discrete communities, there is tight integration. -Mutually exclusive associations with little overlap. -There are mutually exclusive (disjoint and cannot both be true/occur) associations because there is strong competition between the domination species. -Each dominate species creates a particular habitat where a characteristic group of subordinate (lower ranked) species develops. -This grouping represents how the subordinate vegetation adapted to the presence of the dominate species (Tree is on top, then shrub, then herb, then moss). -Each dominate species occupies a particular section of the complex gradient. -There is a change in environmental conditions over relatively short distances (there is tight integration).

Mechanisms of regeneration

- Regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. -There are three main modes of regeneration: continuous mode, fine-scale gap phase mode, and large disturbance mode. -Large disturbance regeneration mode happens directly after a disturbance, the other 2 modes happen in the latter stage of development.

Physiognomy

- The overall size and shape of an organism. -Descriptions such as 'trees', 'shrubs', and 'herbs' are frequently used to characterize the general appearance of the vegetation of a region. -The variation in physiognomy along such gradients occurs with variations in species composition (the 2 variations go together). -As physiognomy varies, species composition (makeup) varies.

Variations in the physical environment

-Dispersal of seeds can result in either a random or uniform distribution of plant propagules over a large area. -Only the plant propagules that land on a suitable substrate will become established. -For moisture-requiring plant, only the propagules that land on moist soil will survive, which will lead to clumping of these species on this particularly moist site.

Bud bank

-A bud bank is the population of buds on the lower stem; the root crown; or roots, rhizomes, or other underground organs. -This refers to the seedlings and saplings that were in tact before the disturbance and survived the disturbance (small trees that were already established). -The region of the plant containing these buds remains dormant due to hormones produced by the live aboveground biomass. -When this biomass is killed, this region of the plant becomes active and new shoots are produced. -E.g. If you have a high intensity fire vs a high intensity wind storm: the seedling bank would be more important after a high intensity wind storm rather than following a fire disturbance because the fire would also destroy the seedling bank.

Coenocline (Community Gradient)

-A coenocline is the sequence of biotic communities along an environmental gradient. -The assemblage of physical environmental factors that change as one moves along a community gradient is called a complex gradient. -The combined community-environment gradient is called an ecocline.

Community example of spacial patterns

-A natural forest stand that reestablished itself after a forest fire. It has a relatively regular special pattern as a result of competition (post disturbance stands generally have a regular special pattern because only the trees that do best will survive, so they have less competition).

Challenges and limitations to ENFD and HRV approaches

-A problem is that longterm, natural climatic variations, changes in frequency of forest fires, invasion of nonnative species, air pollution, and rapid climate change make the looking at the past disturbances and HRV irrelevant as a template for the future. -Zonation (the distribution of plants or animals into specific zones according to such parameters as altitude or depth, each characterized by its dominant species): is not well matched with all values. -Large infrequent disturbances pose special problems (more difficult to work with and are dangerous). -The appropriate historical period is unknown. -Knowledge of HRV is often unknown. -Equilibrium models (perceptions) tend to bias expectations. -Climatic variation may change everything.

Inhibition

-All species resist invasion of competitors. Can make the soil more or less available to next species. -It is much more common, given a seed source, there is competition and inhibition. -This looks like the relay floristics model, however, early seral stages prevent establishment of later stages. -Competitive inhibition of juvenile stages of later seral species. -Early seral stages act as habitat for consumers of later seral species

Allogenic succession

-Allogenic secessione occurs when physical processes that are independent and external to the biotic community cause changes in the physical environment, which leads to changes in biota. -E.g. filling in a lake with sediment to form a bog will change the biota. -Stimulus for change is an external one (comes from outside the ecosystem).

Super-organism Concept

-Although there are connections between an individual and an ecosystem, the differences are too great to make inferences. -This is easy and more convenient. If you look at how policy is structured, the super-organism ideas are still there. -The concept of the community as a supra-organism has never received widespread acceptance because of the numerous fundamental differences between a community and an individual organism.

Mount Zirkel Wilderness

-An area in the study. -Its 2,400-3,400 meters above sea level. -Dominated by Engelmann spruce, subalpine fir, lodgepole pine, and quaking aspen.

Injured trees

-Another example of observational field evidence of HRV is looking at injured trees. -Tree injuries could be due to fire, other fallen trees, animals, cars, or other things. -One specific injured tree might not tell you enough, but if there are many injured trees over a large area, you can make inferences.

Aspen Death and Drought

-Another graph: compared the drought severity to aspen deaths. -The recent peak in mortality correlated with the PDSI (drought conditions). -Lower values mean a drier index (harsh drought conditions).

Disturbance

-Any relative discrete event (forest fires, wind storms, logging operations, insect outbreak) in time (there is a clear beginning and a clear end) that disrupts ecosystem, community, or population structure and changes resources, substrate availability or the physical environment (nothing has been destroyed or ruined, just changed). -This is a very literal description of change. Looking at this from an ecological perspective, it may or may not be a bad thing (makes us think neutrally). -There is a book that changed collective ecological thinking towards the idea that ecological disturbances are the norm.

What has been important in getting an ecosystem to how it is today?

-Ask about the univariate and bivariate special patterns. From this we can infer regeneration patterns and understand dynamics within a stand. -This will tell us what the ecosystem was like in the past.

Future disturbance regimes

-Aspen needs this disturbance to exist. If you do know the spatial scale, you know what each species needs to survive, in the absence of disturbances, the aspen will look more like the fir. Role of disturbance in maintaining this composition. -The compositional future of this stand in the figure? Must consider: -What would aspen need to persist on the land?If fir have a high mortality rate and never make it to the canopy, then aspen would persist. The aspen themselves are not generating, so they need to have seedlings that can compete. -The reason there are no young aspen is because they can't compete with the fir. -The fir is more shade tolerant (fir is more k selected and aspen is more r selected). Aspen need a post disturbance regeneration because they are shade intolerant.

Stand edges

-By looking at stand edges, you can observe a patch in the landscape and can make assumptions about how these patches arise (can tell by the stand edge how the patch ended). -E.g.: patches created by human activates usually have linear patterns and right angles. Patterns that arise from natural causes tend to reflect disturbances without patterns. Look at changes in aspect and soil, if there is no change, this could tell us that the patch could have been caused by natural causes. Forests on windward sides, stand edges.

Insect causing mortality

-Can examine the ring-width index over years and see the changes in growth rates. -This might help determine the cause of the tree growth fluctuation. -Insect and wind disturbance both look the same on a dendro examination. -The destruction is difficult to establish. -Establishment, mortality, and releases in tree rings (insects cause mortality?).

1. Can discrete (separate) units of vegetation be clearly defined?

-Can this be true, or is there continuous, gradual variation over space in the attributes of vegetation? -When plant populations are analyzed according to their quantitative distribution along an environmental gradient, each species forms a bell-shaped curve. -The curves are distributed along the gradient as a series with overlapping ranges, but no two curves have identical ranges or optima (best). -No clusters of species are found (representing similar species behavior relative to the gradient) -This leads to recognition of a series of discrete units. -This suggests that species populations form a shifting series of combinations along environmental gradients. -This leads to the interpretation of vegetation as a complex and largely continuous population pattern

Tree seedling recruitment/establishment example

-Figure 14-14 represents the seed rain from Picea engelmannii in three forest clearings in Utah as a function of distance from the stand. -Seed rain is the production at and dispersal of seeds to a site. The seed rain varies as a function of distance from the plant. -Figure 14-14: The y-axis is the uncut forest and the x-axis is the distance from the uncut forest. This shows the total amount of seed rain arriving on the ground as a function of distance from the uncut forest. -The greater the distance from the uncut forest, the less seed rain (aka as you move away from the uncut forest, the total amount of seed rain decreases.

Old Growth

-Canopy gaps created by death of large trees are sufficient for juvenile trees to grow into the canopy, resulting in a mixed-age and multi-canopy with snags (dead standing tree). -There is increasing heterogeneity (uniqueness) as the stand develops. -Old growth is poetic. -An old-growth forest — also termed primary forest, virgin forest, primeval forest, late seral forest, or (in Great Britain) ancient woodland. -It is a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community. -E.g.: Post wind storm or insect outbreak disturbance: The old growth stage would be quicker during regeneration because there is so much more developed understory. Structural stand is important for determining likely post disturbance development.

Climax

-Climax is a self-replacing seral stage that is relatively stable (in the sense that it persists for a long time- several to many generations of dominant plant species-relative to other seral stages).

Clustered spacial patterns

-Clustered for the single tree with other bush type species, because the 2 species rely on each other. -You tend to find clustered patterns in areas with established organisms in harsh environments.

Communities

-Communities vary in their composition and structure according to variations in the physical environment -Local and regional gradients (categories) of physical factors are associated with characteristic patterns of ecosystem types and biomes.

Community Ecology (Synecology)

-Community ecology is the studies involving the description and quantification of some aspect of a natural assemblage of different species of organisms. -E.g.: the study, classification, and mapping of forest plant associations, or forest types (the description of the animal community in a small lake; or study of the change in plant and animal communities in an area over time). Community ecology is the association of populations of two or more different species occupying the same geographical area and in a particular time. -No longer talking about population ecology (dynamics of species populations and how these populations interact with the environment. It is the study of how the population sizes of species change over time and space.) -Community Ecology is community integrated (united) or not integrated (not united) -Specific objectives of community ecology including understanding forest dynamics

Quasi-organismal view

-Concept of the community as a quasi-organism: says that there are certain similarities and parallels between these 2 different levels of biological organization. -A plant community differs from a true organism in the following ways: -In a community, there are more than one (made up of multiple organisms) different from an organism which is made up of cells that are all genetically identical. -Communities lack genetic identity because organisms are all different/not all the same. -The source of energy is usually fixed when talking about just one organism. -But in a community, there are different variables that determine the amount of energy (so the sources is no longer fixed). -A community has boundaries that are not as discrete (distinct) as that of an organism.

Observational field evidence

-Data can be collected without any instruments, just by observing. -This method rarely tells us the definitive answer to HRV, especially since we wish to understand long term forest development (how far back can observations go?).

The subalpine forest of the Colorado Rocky Mountains

-Decrease in aspen in the landscape. Quaking aspen resprouts vegetatively and from seed (a self replacing aspen forest). -Shade tolerant conifers replacing the aspen. -Whether or not the decline in aspen is due to climate change or poor management decisions depends on our understanding of the HRV.

Fire extent

-Dendrochronology can be helpful in determining fire extent and therefore showing HRV. -This can help determine fire extent: identified patches then look at the boundries and locate them on topographic maps and can construct the dates of last stand-replacing fire. -Then, look at the digital orthophotoquad with polygon boundaries, once you have determined the dates of the last stand-replacing fire. -Can also compare fire and climate once you have the dates of past fires and areas. -Can look at the tree index (measurement of trees) from x years before and after the fire. How does this index in one area compare to the index in a another area.

Dead trees

-Dendrochronology of dead trees can also be helpful when finding the HRV. -You can cross date the dead trees and the live trees and check for growth releases. -With wind events, samples can be taken from both dead and alive trees. Can take cross sections of injured trees.

Dendroecological reconstruction of stand history

-Dendroecology: The science that uses tree rings to study factors that affect the earth's ecosystems. -E.g.: analyzing the effects of air pollution on tree growth by studying changes in ring widths over time. -Dendroecological reconstruction of stand history uses tree rings to recreate a stand. -How good the map was at depicting the land is important. -Can tell if a disturbance occurred or not. -Is aspen declining? If so, over what temporal scale?

Alex Tansely (quasi-organismal view)

-Developed the ecosystem concept in 1935. -Tansely's points include: -Lack of clear delimitations (determining boundaries) -Lack of genetic unity (same community types might develop differently/have different life histories) -Lack of coordinated reproduction -Lack of structural integrity -However, Tansley saw a strong enough similarity between an organism and a community, so that an analogy is valid (distinction between the literal similarities and the analogy).

Ramensky and Gleason

-Different concept of vegetation was developed independently by these 2 plant ecologists (1920s). -Consider that species are distributed along their environmental gradients according to their individual adaptations and tolerances. -The community of plants observed in a particular habitat consists of populations of those species that are able to invade, survive, and reproduce successfully in that environment. -Because no 2 species are alike in distribute, the centers of species distributions along the gradient is scattered with a broad overlap.

Should we take action?

-Difficult to tell when we soul take management applications. -It is hard to know when to step in because we are unsure whether a disturbance is in the HRV or not. -If it is, then we don't take action, but if it isn't we do. -Is the HRV changing? This is important because if this changes, then our limits to management applications within the HRV will change also.

Polyclimax Theory (Tansely)

-During succession, floristic convergence (intersecting of vegetation) is only partial (incomplete). -There may be more than one type of stable endpoint. -Alternative stable endpoints are controlled by local factors such as topographic position or soil type (consequently, called topographic climax, edaphic climax, etc. as apposed to climatic climax). -This theory points out that there are many factors that can intervene to prevent and area from reaching the climatic climax condition. -In addition to the climatic climax, there are other environmental factors including: pyral climax (fire), edaphic climax (soil), and biotic climax (animal influences). -Polyclimax theory: the vegetation of a region is viewed as a pattern of communities at different stages of succession, some of which may reach climatic climax relatively rapidly (only a few centuries). -The idea of many climaxes (not only climate factor). -This view reduces the scale and looks at finer spatial patterns. -Also recognized that there may be more than one type of stable endpoint that are controlled by local factors.

Ecosystems are dynamic

-Dynamic: (of a process or system) characterized by constant change, activity, or progress. -All of the descriptors of a disturbance regime infer that that ecosystems are dynamic.

Stress tolerance/competitive ability

-Early stages of succession are relatively free of competition because their focus is on growing. In early stages, the efficiency with which solar energy enters the ecosystem is low. -In late stages of succession, there is more competition.

Types of succession

-Ecological succession, the process of ecosystem development, occurs in virtually every type of environment found on earth. The details of succession vary according to the type of ecosystem. -Primary or secondary succession. -Succesion begins after a disturbance, whether it is at a slow rate (primary succession) or a fast rate (secondary succession).

Ecological Theory

-Ecological theory is used to be an expectation that ecosystems remain unchanged over long periods of time. -During the 20th century we realized that forests are changing and this is due to disturbances. -If we look at variation over time of forest ecosystems, we can call it HRV.

Ecosystem Management

-Ecosystem management (EM) means managing forests as a whole, integrated systems rather than the frequently fragmented and uncoordinated management for individual ecosystem components and values- trees, wildlife, water, aesthetics. -Similar to how to protect endangered species: protection of individual species or protection of ecosystem. -EM requires a clear definition of a desired future forest condition with respect for all diversity.

What is ecological succession?

-Ecosystems change for a variety of reasons: change in climate, soil conditions, change as a result of interactions between the members of a living community, and change caused by disturbances like wind and fire. -The process of change after disturbance is called ecological succession. -Over time, there is a series of living communities- plants, animals, and microbes- that successively occupy and are replaced on a particular area of land, with accompanying changes in soil and microclimatic conditions. -Ecological succession is a directional (non cyclical, there is some difference in species that occur in latter and before), non-seasonal(longer time periods, decades to centuries ago), cumulative change in the types of plant species that occupy a given area though time.

Selection patterns

-Either r-selected or K-selected. -For r-selected, the mortality is density independent, it has a type 3 survivorship curve, there is low competitive ability, a short life span, and rapid rate of growth. -For K-selected, the mortality is density dependent, the survivorship curve is types 1 and 2, the competitive ability is high, the life span is long, and the rate of growth is slow.

Facilitation

-Environmental alteration by pioneer species is frequently a necessary condition for successful establishment of later successional species. -Facilitation model -like clemencies model, follows the relay floristics model -Each wave of colonists "prepares the way" for the next group. -Biotic modification changes conditions to favor later stages. -More likely to occur in primary succession. -Facilitation would be more important during primary succession because when you start at the base level, with nothing, the gradual growth of the first species that establish in this area provide a more available area to thrive.

Dead trees

-Examination of dead tree cohorts can also be a good observation method in leading us the HRV. -Dead trees are indicative of past disturbance events. -E.g. Observation: looks like all the same species of trees that is dead. Probably an insect outbreaks because they usually only infect one species of trees. You can tell this destruction was due to insects because there are two species of trees, one is alive and one is dead. -It isn't just an old growth forest because if it was, you would be able to tell the difference between the mortality rates and there would be many different species of trees. -E.g. Observation: shorter single tree damage that is isolated and look burned. Can tell that the dead trees without branches were killed longer ago. There are surrounding trees that are part of the post disturbance cohort. -E.g. Dead trees are all oriented in the same direction. Could be due to a wind storm.

Morphological causes of special patterns CH14

-Example: dead adult trees and new sprouts. -What bivariate patterns would you expect to see in a burned forest? -The burned forest would be clustered. There would be clumps of live regeneration of sprouts (because there is a positive association between the sprouts and the dead parent trees). -Were there any dead trees that you would expect to see more sprouts coming out of? (positive association) -There would be positive bivariate special pattern between dead trees and sprouts.

Possible Patterns of Species Distribution

-Figure 13.1 shows 7 hypothetical patterns (a-g) of distribution of plant species along an environmental gradient such as moisture or elevation. -There are several possible ways plants could distribute themselves along environmental gradients. -Figure 13.1 shows a line for species of: tree, shrub, herb, and moss. (The importance value of each species changes as the environmental gradient changes). -It IS possible for different ecosystems to be in different regions (no ecosystem is always the same) -All species arise and grow together. They are either tightly integrated or individual.

Assumption of climax theories

-Figure proposes mono climax theories. -It is looking at ecosystems being more or less integrated or individual. -Shows that ecosystems are coherent (logical and consistent) units. -It's important to recognize that individual species can respond individually to different environmental conditions.

Fires In Rocky Mountain National Park (RMNP)

-Fires are integral to most ecosystems on earth. -E.g. Data from Rocky Mountain National Park (RMNP). The line graph represents tree ring index (a standardized average of all tree rings in a stand). -Growth of trees that established after a fire. All competition is removed after disturbance, so new trees that are established have rapid growth because there is no competition. As the competition increases, the growth slows down. -Climatic influences on large, severe fires. In the past 1695, there were more trees, when the fire hits, the over the years, the tree-ring index decreases (so there is lower growth rate in the years following the fire). -If there is a canopy disturbance, there is growth release. We expect rapid initial growth when the disturbance effects the entire area. -The map of the entire RMNP shows what arose after fires (temporal data applied to landscape). -The area has been shaped by large fires over the past years. We can say that large fires are within the HRV. If one large fire occurs, it doesn't mean something is not normal.

The role of HRV in ecosystem-based management

-Fore resource managers, it is important to know the range of critical ecological processes and conditions that have characterized particular ecosystems over specified time periods and under varying degrees of human influences. -An understanding of how ecosystems functioned and sustained themselves in the absence of major human modification of ecological patterns and processes provides a concrete model of ecosystem integrity.

Fredrick Clements (organismal view)

-Fredrick Clements proposed a high degree of integration, a plant community is an organic entity (a complex organism). -Development of the analogy between the community and the individual organism is largely attributed to Clements. -He believed that a community, like an organism, is born, grows, matures, reproduces, and dies. Organismal view of a community. A community is like an organism.

Geometric vs. Logistic Growth

-Geometric population increase is characteristic of the early phases of population growth (growth of a population that has recently escaped from the traditional population control e.g. the human population). -Geometric growth ignores the reality that the early growth of a population changes (the populations develop over time). -Despite the enormous reproductive potentials, populations of some organisms grow at geometric rates for only a brief period of time (ignoring disturbances, they generally don't show sustained growth over many generations). -Logistic growth considers the lack of sustained growth over many generations.

Early critiques (Gleason)

-Gleason discussed some of the problems with mono climax theory. -He pointed out that it ignores climatic variability and disturbances as ecosystems change. -These people worked in the 20s and 30s. -Early theories of succession ignores the importance of disturbances and climatic variation (must consider disturbance and climate change). -Disturbances were seen as abnormal which led to problems of management.

Henry Gleason (individualistic concept of the plant association)

-Gleason thought we should think about individuals responding to environmental changes. -Based this on 3 simple premises: (1) Dispersal of propagules (a vegetative structure that can become detached from a plant and give rise to a new plant, e.g., a bud, sucker, or spore) occurs at different rates. Therefore, propagules arrive at different sites at different times. (2) The site (operational environment) acts as a filter so that only certain species can survive at a particular site. (3) Sites vary over space and time. Therefore, species composition at any particular site will be unique because of chance dispersal and the independent distribution of each species.

Recent growth of live vs. dead trees

-Graph: the green dots represent dead trees and the red dots represent alive trees (time period over a span of 3 years). -Trees that ended up dying had a slower growth rate (narrow tree rings) compared to trees that ended up not dying. -The growth conditions were worse.

Why are HRV studies needed?

-HRV studies are needed because: -Forests are dynamic and forests are changing: this does not mean that everything is normal. -Sometimes we need to do nothing if the change is within the limits. We can be flexible in our management approach. If we go outside the HRV, management should do something. -An ecological perspective: nature has a range of ways to be but there is a limit to those ways and human changes must be within those limits. -A resource management perspective: awareness and understanding of disturbance ecology and how disturbances play a role in ecosystem dynamics (must know the consequences of management decisions). We must know what nature is intended to do.

Ecology of natural disturbances

-How and why forests look the way they do after a natural disturbance.

1997 Wind Storm and 2002 Fire

-How do pre-fire composition and disturbance history affect the abundance and composition post-fire regeneration? -Total regeneration varies with pre-fire composition: total amount of aspen increased over a period of time (this is regeneration via a bud bank). -Pine has (serotenous cones) a more steady increase. -Intensitiy of fire changes which could change th regeneration pattern. -There are different modes of regeneration (there is rapid post-fire regeneration).

Ecological question

-How is HRV relevant for putting disturbance regimes into context? -What are the limitations to using photographs and maps to determine HRV?

2. How integrated (merged) is a plant community?

-How is this, and does a plant community function as a coordinated, harmonious whole? -Each community is characterized by a particular species composition, vertical structure, patterns of change over time, biomass, energy flow, and nutrient cycling. -It is the biotic component of the ecosystem. -Community has no implicit definition of spatial extent or boundaries. -This is a question of interdependence (2 or more things being dependent on each other) or functional integrity (the state of being whole/unity and undivided). in -A community is a multispecies aggregation with varying degrees of integration (a more or less specific composition) -A community is a multi-species aggregation (formation of things in a cluster) with some degree of repeatability and consistency from place to place (a formation of clusters of many species that can repeat and can be consistent).

Spacial Arrangement of Populations

-How populations are structures in space. -We can put patterns into 3 possible categories: random, clustered, and regular. (1) A common pattern in nature is random. (2) There could also be clustered populations (a fine spacial scale may be random, but looking at a larger scale, it can be clustered). (3) Another pattern in nature is regular, which maximizes the space between trees.

Geometric Population Growth

-If a reproductive unit of a species with a short regeneration time is placed in an environment that provides all it needs to live, then the abundance of the organism will increase over time. (Figure 14-4) -This pattern of population change is called geometric/exponential growth. It starts of exponentially but as it approaches the carrying capacity it levels off (e.g. elk herds get too large until they cant support themselves any longer). -The abundance of the population shows an increase with time. -If an organism has discrete/non-overlapping generations (annual plants w/ a single generation per year), then N(t+1)=R(sub0)*N(subt) -Aka: The population size in the subsequent generation (N(t+1)) is equal to the net reproductive rate (Rsub0) times the population size at generation (Nsubt). -The higher the reproductive rate, the more rapid the population growth. -There are usually constraints that make this logic non-realistic. The reason this doesn't apply is because there are different.

(f.) Continuum of vegetation change along environmental gradient

-If all species distribute themselves along the environmental gradient simply in response to their individual environmental tolerances (independent of the presence of other species). -Then, species in all layers appear and drop out again in an irregular manner when moving along the complex gradient. -There is neither identifiable grouping between layers nor sharp exclusion of species within a layer. -There is a continuum (continuous sequence) of vegetation change along the environmental gradient.

What is the convenience of being a super organism?

-If our worldview is structures into distinct units then our world view is more simple. -Just like if we look at each organism separately, we will have a better understanding of each one and therefore, a better understanding of the ecosystem as a whole. -Once you can categorize a site, then you can be prescriptive (narrow) (I understand what this super organism is, what it looks like, and what it does).

Long term variability

-If we can understand long term variability, we can put more things into context. -There are pros and cons to using any type of sources for information. -How do we reconcile (reunite) long term variability with current change?

Implications of the organismal view

-Implications: discrete, repeatable vegetation units can be recognized and classified. -E.g.: A cell is a part of an organism just as an organism is part of a cell. A cell has predictable stages, just like an ecosystem has predictable stages. -Succession constitutes the series of life history stages of the complex organism (progression amounts to the stages of an organisms life history).

New recruitment

-In fine-scale gap phase regeneration, new recruitment comes from new seed dispersal or from a seed bank. -Within the gap phase mode: there is either new recruitment (new seedling are being established) or reorganization response.

Mutual exclusion

-In logic and probability theory, two propositions (or events) are mutually exclusive or disjoint if they cannot both be true (occur). -Strong competition between each of the dominant species (tree, shrub, herb, moss) leads to strong mutual exclusion (so in competition, if one species wins, the other can not also win because if they are mutually exclusive, they can't both win).

Autogenic succession

-In many cases, the replacement of one community by the next happens because of changes in the physical, chemical and biotic environment that have been produced by the resident organisms. -These changes often leave the site less optimal for the organism that produce the change and more optimal for those organisms that replace them. -The stimulus for change is an internal one (comes from inside the ecosystem) (e.g., gradual soil improvements could allow a new species to develop).

Tree rings on trees in the tropics

-In most areas in the tropics, trees don't produce tree rings because there are no seasons, so dendrochronology is not a good method for finding the HRV in this area. -If there is no seacsonal variability there are no rings, however, some tree rings have monsoon season instead of regular growth seasons. -The dry season and the wet season sometimes show rings.

Spatial scale

-In spatial ecology, scale refers to the spatial extent of ecological processes and the spatial (of or relating to space) interpretation of the data. -The response of an organism or a species to the environment is particular to a specific scale, and may respond differently at a larger or smaller scale.

Survivorship curve type III

-In type III, a constant percentage of the survivors die in each time interval. -There is high initial mortality then lower mortality at old age -This is common in plants because as -Type IV is similar but its more heavy juvenile mortality followed by low and fairly constant mortality for the rest of the life span.

Continuous mode

-Individual trees are continuously establishing and growing. Shade tolerant species can reach maturity under a closed canopy. The seedling and sapling will move into the canopy without a gap. This is less common because there is competition. -Highly shade tolerant species (species that can live well in the shade/ don't need sun) that can complete their life cycle beneath a relatively closed forest canopy. -In a strict sense, this is relatively rare. -Implies continuous juvenile recruitment and growth into the main canopy, even though attainment of dominance may be favored by the death of another canopy tree.

Individualistic and Continuum hypothesis

-Individualistic and continuum hypothesis of a region as a series of plant distributions views the vegetation of a region as a series of plant species populations distributed independent of each other along the physical gradients of the environment. (f.) -Gleason was looking at the individual concept of the plant association. -Supporting evidence for validity of Gleason's concept: Quantitative studies of floristic composition and vegetation gradients. -Independent migration of species as shown by paleo-ecological studies. -Implications: vegetation varies gradually in space and discrete boundaries between different vegetation units are rare. -Due to the uniqueness of associations, vegetation cannot be perfectly classified.

Difference between fire and wind disturbances

-It is important to know the difference between fire and wind because when wind destroys forests, we try to fix it but we end up causing more destruction and end up slowing down the regeneration. -Distinction between wind and fire: wind usually only kills tree canopy, and fire either kills floor vegetation or all vegetation.

Large disturbance mode

-Large disturbance (i.e., stand-replacing) mode is cohort establishment after coarse-scale (large) disturbance. -This fits the early stages of Oliver's model of whole stand replacement. -With this mode, regeneration is associated with large disturbances. The beginning point of Oliver's structural changes of forest development. The other 2 modes happen at latter stages of development.

Disturbance

-Large patches in the landscape created by disturbance. Once regeneration is in full swing, patches of regeneration will be clumped as entire area of blown down stands.

Issues with Monoclimax theory (theoretical explanation)

-Life history (the series of changes undergone by an organism during its lifetime) of the climax formation as a theoretical explanation of succession: if you know previous climate, it can explain the succession. -This theory is false. -There is microclimatic variability these could affect vegetation. -If you apply this view, it won't be accurate because ecosystems are changing either gradually or abruptly. -This view also ignores the role of disturbances as an agent of change. -This view also says ecosystems are the base of environmental movements. -Also says that everything is stable and unchanging.

Survivorship curves

-Look at the age distribution of a population. We can say there are a certain number of people that are young and a certain number that are old, then assume that the age structure is a predictor of mortality. -There are a large variety of survivorship curves that can be found in nature, but there are 4 major types. -There are two categories of a survivorship curve: 1. the cohort or dynamic type 2. the stationary age distribution, or static type. -Survivorship curves are not constant they change with removal of predators.

Does HRV always make sense?

-Looking at climate change: does it make sense for us to look at this still. Even if we say climate is changing and it doesn't make sense to stay without these limits. But without the limits, we don't know if this should happen.

Historical map

-Map of timber forest reserve. -The legend depicts different forest types (species composition). -What might this map be able to tell and what might you not be sure about, still? -Positional accuracy and categorical accuracy we are still unsure of. To what degree do the forest types in the areas depicted on the map, actually correspond to forest types on the ground.

Maps and photographs

-Maps and photography (terrestrial photographs aka photos taken from the ground) can also help determine the HRV of an area. -If available, excellent for documenting gross changes and generating hypotheses to explain the changes (especially when combined with other data). -Problems with the photographs: they are only available after 1850. -Locations may not be represented (e.g. along roads, railroads). -We tend to take photos of unusual things (some things grab our attention more than others) which is not a good representation of the whole area. -Changes are not easily quantified. -Both maps and photographs are just snapshots in time and may not represent landscape conditions over long period of time.

Mechanisms, pathways, and models of succession

-Mechanisms: a process or interaction that contributes to successional change (e.g., competition, predation, change in soil moisture and nutrients availability). -Pathways: the temporal pattern of ecosystem change (e.g., the sequence of plant communities and changes in physical and other biotic components of the ecosystem over time). -Models: some abstract conceptual representation used to describe and or explain successional pathways in terms of successional mechanisms that result in successional change. -Ecologists have been struggling to find a general explanation of the mechanisms and pathways of ecological succession.

Supraorganisms

-Monoclimax theory is linked to the idea that the climax is comparable to the supra organisms. -The term "supraorganism" refers to a collection of individuals which behave as a single unit with enhanced function. -(we prefer to the more common but slightly less informative "superorganism") -Biologist Mobius recognized the intimate association among oysters and the algae they fed on, the parasites that prey on them, and the other organisms they compete with. -Recognition of the integration of the components of a biotic community into a functional system led to idea of the community as a supra organism.

Survivorship curve type II

-Mortality in type II populations is distributed evenly across all age classes -Its the straight line -There is a constant number of deaths per unit time. -Mortality is independent of age -Birds tend to have this.

Population ecology

-Most living organisms exist for most of their lives as members of a population: a group of interacting individuals of the same species. -There are both advantages and disadvantages to an individual organism as a member of a population. -The study of the abundance, distribution, productivity, and or dynamics of a group or organisms of the same type (a single-species population). -E.g.: Investigating the competition for light and nutrients in a pine plantation, the role of disease in controlling the numbers of insects on a tree, or the rate of growth and mortality of the individuals in a salmon population.

(b.) Gentle environmental gradients

-Mutually exclusive associations with broad overlap (more spread out). -Similar to (a.) but there is broad overlapping ranges because of less intense competition and less competitive exclusion among the dominate species. -There are identifiable groupings involving all layers.

Historic Range of Variability (HRV) of Ecosystems

-Natural historic range of variation (NRV or HRV): is the range in ecosystem conditions that is the outcome of past natural disturbance. -Historic range of variability of ecosystems: the fluctuation in the amount of something over time. -Ecosystems exist within a range of conditions. Conceptually, to set some bounds on normal or historical variability within the ecosystem. HRV is critical in allowing us to know what is presitent and what is unpresitent.

Seedling bank

-Seedlings of shade-tolerant tree species can remain in the understory as surpassed seedlings or saplings for decades. -These are capable of responding to increased light and reduced competition for soil resources after disturbance to the understory canopy. -If there is a well established seedling bank that survives a stand-replacing disturbance, it may dominate the seed rain, seed bank, and bud bank in determining the composition of the post disturbance community of trees. -Regeneration that relies on a seedling bank is quicker than other forms because they are already established, they just need to take advantage of their resources (light, water, nutrients).

Range of natural variability

-Natural range of variability is often used to describe disturbance processes, and the ecosystem variability that these disturbances create (breadth of natural conditions). -Ecosystems shaped by frequent process/events tend to be characterized by a narrow/limited range of natural variability (less variability with frequent environmental change). -Ecosystems shaped by infrequent events are characterized by a broad range of variability (more variability with infrequent environmental change). -E.g. you have 2 friends, one friend mows the lawn every day, the other mows their lawn once a year. The lawn that is mowed everyday looks the same because its being maintained. The other lawn looks different every day because the disturbances aka the mower is infrequent. -The ecosystems with a wide range offer both opportunities and difficulties. -We know that any range of conditions within these limits is normal. The difficulty is what the limits are.

Biogenic succession

-Occurs when there is sudden interference with an autogenic or allogenic succession by a living organism that temporarily becomes the major agent of successional change.

Young forests vs. old forests

-Old forests are more heterogeneous (different/diverse). -Older forests are more susceptible to wind because of the micro gusts and the different level of the canopy causes more damage. -The old forest have a larger seedling bank because of the different canopy level which leads to a quicker regeneration rate.

Univariate

-One variable -There are 3 possible univariate groups: random, clustered, and regular.

Figure 17-11 A Temperate seral forest (2 species)

-Page 499 graphs -A successional forest in Arizona in where aspen is failing to reproduce itself and is being replaced by white fir. -A lot of small fir trees on the forest floor, canopy is mostly aspens. -The small fir must have regenerated continuously. Because of the peak in aspen, they regenerated using gap tree dynamics. The aspen could have regenerated following a disturbance. -The curve is bell-shaped, so the species is probably not replacing itself and may be seral. -In C, the dominant species exhibit a reverse J-shaped age curve, so we could conclude that the area is climax.

Initial floristics

-Part of the individualistic/stochastic view of succession by Gleason (part of the mono climax theory of succession). -Eglar proposed that the succession of plant species in abandoned agricultural fields depends on relative growth rates and shade tolerance of the species arriving (succession was dependent on who gets there first and their relative growth rates). -All species establish soon after disturbance. -Dominance (not establishment) occurs in stages over time.

Historical Photograph Example (Timber Reserve)

-Photo: looks like logging operation with horses, some trees down, dirt road, mountains in background. -You know that a timber operation happened at some point. You don't know where it is, or what time it's from. The mountains might give an indication of where it is. You don't know the species composition or if the logging operation targeted a specific species, or how extensive the logging operation is. -Are current forest conditions shaped by natural causes or by humans (logging operations)? This photo can help answer this question. The text that went with it: "the timber in the area was "exceedingly poor -- second- or third-rate, from which almost no clear lumber could be expected" "[Very little of any tree species was cut and of what timber was used, the dead timber was preferred because of its lighter weight.]" -Not good for logging, there was limited resource extraction in this area. Writing along with photo helps.

Windstorm effects

-Photograph of an area affected by a windstorm in 1997. -Then in 2002, there was a forest fire. -Some forests were just affected by wind, some just by fire, and some by both. -Regenration was tracked in these areas to find connections and more information for a better understanding of how different disturbances have a different effect on regeneration.

Population ecology

-Population ecology is the study of the abundance, distribution, productivity, and/or dynamics of a group of organisms of the same type (a single-species population). -An example would be the rate of growth and mortality of the individuals in a salmon population. -This is the study of the abundance and dynamics of species populations.

Conclusions and Implications

-Pre-fire forest composition and disturbance history affect post-fire regeneration. -Effect of compounded disturbances on regeneration varies across species. -Implications for aspen decline. -Possible feedback loops. -Future work, especially predictive models of forest development under different climate scenarios should explicitly consider how potential interactions among disturbance affect trajectories of ecosystem development. -If aspen decline, we have to acknowledge that the same factors that are causing this are also declining.

Recruitment of new plants into a population

-Recruitment of new plants into a population can occur in several ways as a result of either sexual reproduction or vegetative reproduction. -This is how regeneration following some disturbance occurs. -The production at and dispersal of seeds to a site occur in 4 ways: seed rain, seed bank, bud bank, and seedling bank. -Regeneration that relies on seedling bank is quicker than other forms because they are already established, they just need to take advantage of their resources (light, water, nutrients).

Community causes of spacial patterns

-Regular for area with trees planted in rows and evenly separated (people did this to minimize competition between the individual organisms).

Seed bank

-Seed rain contributes to the seed bank. -A seed bank is the population of living but ungerminated seeds contained in the soil (live viable seeds that are in the soil/already on site after a disturbance). -The ratio of viable seeds of different species changes between the soil surface and deeper soil layers so removal of different layers will alter the species composition of germinates. -The larger the seed bank, the better the regeneration. -If there is a disturbance event that eliminates soil, then the seed bank, nutrients, and water is also removed. If soil is removed, the shape and area of the forest becomes more important when thinking about regeneration because now seed bank isn't important, but seed rain is. -If soil is intact, the seed bank is there still. -Some fires are so hot that the upper part of the soil is eliminatied/destroyed and the seed bank is compromised. If disturbances get larger and more intense, then there is a higher reliance on seed rain which takes longer and depends on the size and shape of the live/undisturbed forest.

Static vs. cohort (dynamic) life tables

-Static life tables: we use static life tables to assume the future. You have to make assumptions about survival and mortality (e.g. you could assume there would be more fir than spruce in the future, but survivorship curve would have to stay the same to assume this. This can be difficult because survivorship curves to NOT hold constant). -Cohort (dynamic) life table: if you follow a population over a time period (e.g. you see a cohort of trees establish, come back and see and record which trees have survived) The advantage of this is you can see the actual development, however this is very impractical.

Density-independent mortality

-Suggests that because mortality affects individual organisms rather than populations, investigations of animal distribution and abundance should focus on the individual -There are other factors that influence the survival and reproduction of individuals: weather, food, other organisms, and shelter. -E.g. Droughts or natural disturbances are not dependent on how dense a forest stand is. -r-selected species tend to have a density independent mortality.

(g.) Bimodal or multimodal distribution

-The distribution of species along the gradient can display various combinations of the foregoing patterns at different locations on the gradient. -The distribution of species along the gradient can display a bimodal or multimodal distribution.

(e.) Few species in the dominant layer (responding to climatic factors) and many species in the lower layers (responding to a complex of local factors)

-The dominant tree species do not show mutual exclusion, but subordinate species do show mutual exclusion. -Species (tree canopy) in upper layer have broadly overlapping distributions along the complex gradient. -Species in lower layers show marked grouping. -This occurs if: there are relatively few species in the dominant layer (all responding primarily to factors relating to climate that vary gradually along a major complex gradient). -And if there are many species in the lower layers [all responding primarily to a complex of local site factors (like soil characteristics) that vary considerably over short distances].

Compounded disturbances affect composition of regeneration

-The effect of compound disturbances on regeneration varies across species.

Distinguishing between gap phase dynamics and post disturbance regeneration

-The graph does not provide all the information to make assumptions. -The figure does not provide the spatial area. If there is a large spatial area (10,000 ha forest) then we can conclude that the forest regenerated from a post disturbance stand replacement. -The regeneration mode can be determined by spatial area.

Forest development (Oliver 1981)

-The graph shows structural changes over time which may or may not be accompanied by species composition. -Not only the changes in species composition but proposed stand initiation, stem exclusion, understory re-initiation, and old growth stage. -Ecosystem recovery from disturbance is a major cause of change in community structure over time. -LIfe forms and structural arrangement of there life forms in the community change from the stand initiation, through the stem exclusion, to the understory reinitiation phases of the development of a stand after stand replacing disturbances.

Patch Dynamics

-The patchiness in vegetation is both due to patchiness in the underlying physical environment and due to vegetation responses to disturbances. -They situated disturbances fundamentally in vegetation structure.

Survivorship curve type 1

-The population has very low mortality until near the end of their life span -Most dying organisms are old. -Humans -Its the top curve

Article 1: Results and Discussion

-The relationship between ring width and temperature during the summer, spring, and all previous seasons are shown. -Only the red bars are significant, and there are both negative and positive correlations. -The only significant relationship is: the relationship between temperature and the spring of this year. It is a inverse/negative correlation. -The cooler the temperature, the greater the ring width. The cooler it is, the better the aspen grows. -When temperature is above average, the aspen grew less than average. -The same comparison was done with precipitation instead of temperature. -Literally, the only statistical significance was in the winter. -Ecologically, if there was a higher precipitation, there was a wider ring width (meaning better growth year).

Article 1: Site locations and field methods

-The studied across a large region. -10 sites were selected based on dominant aspen canopy and less than 50% mortality. -There were increment core samples collected from about 50 live and dead trees at each site. -They went to stands where aspen had suddenly died. -The intent was not to look for random samples or not trying to map it, but trying to understand mortality. -Philip used method of dendrochronology, comparing the core samples and the growth to temperature for any given year.

Understanding Forest Dynamics

-The study of how plant communities originate, develop, and maintain themselves. -Why and how forests change in their structures and species composition -E.g.: concept, data collection, data analysis, interpretation of data. -General explanations of forest dynamics include: critical evaluation of alternative theories or models that have been proposed -Consider how certain premises (assumptions) related to general theories and concepts influence contemporary debates about forest management. -E.g.: Given global environmental change, how do we understand what is happening, what do we know about ecosystem structure and function? What is the nature of plant community? Are there general models of special patterns of biotic (living) communities?

Article 1: Conclusion

-The tree rings were used to come to conclusions. -There is long term climatic variability and an increase in disturbances. -Apen growth is positively associated with winter precipitation and negatively correlated with spring temperatures. -There are also apparent peaks of mortality during periods of harsh drought conditions. -Multiple years of reduced growth precede (lead up to) mortality.

What is the unit of a population?

-The units of a population are what organisms make up that population (e.g. a plant) -A genet is a unit (plant) in the population arising from a seed from sexual reproduction (e.g. a seedling). This is genetically unique. -A ramen is a unit (plant) in the population arising from a vegetative reproduction (e.g. one that comes from asexual reproduction). -These are the same population but have different development aka different tree seedling recruitment and establishment (long term population development can be more similar).

Compound Disturbances

-There are 2 or more disturbances effecting a particular ecosystem in a short period of time. -This is a result of changes in forest disturbance regimes. -Extent, magnitude, and/or frequency of various forest disturbances are increasing. -Compound disturbances can affect ecosystem development in ways that are not well understood. -Need to understand future forest patterns and processes in the face of a changing climate and changing disturbance regimes.

Size frequency curves for the dominant trees in three forests

-There are issues with the definition of climax and the idea of it. -The early seral stages of both primary and secondary seres may outlast the climax, and seral communities may be self-replacing for many generations before they are in turn replaced. -Is this equilibrium? (or is it a climax?) Is a particular regeneration mode important? What kind is most important in a given forest ecosystem? Spatial scale is important. -By examining a series of areas that vary in age since disturbance, we can construct the probable seral sequence (or range of alternative sequences).

Logistic population growth

-There is a lack of sustained growth because as a population grows in numbers, its negative feedback (environmental resistance) also grows due to competition, disease, stress. -As a population increases, so does the environmental resistance which steadily reduces the rate of population growth until the resistance is so great that population increase is no longer possible. -The population grows slowly at first, then there is a period of rapid increase, then the population growth rate slows down as it approaches the carrying capacity (this is where the environment is full of a particular species). -The population can come crashing down because the more a population overreaches the carrying capacity, the more it will quickly shoot down.

Sudden Aspen Decline

-There is long term variability in aspen (fluctuates broadly as a function of fires). -Climate change is changing disturbance regimes (arrangements). -There was a sudden spike in aspen decline in 2005. -When this is put into context of long term variability, it might be due to climate change.

Morphological example of spacial patterns

-There would be a positive bivariate association between adult trees and new trees with large seeds (because large seeds can't travel far). -Some trees regenerate almost entirely through the help of bird species.

Static life table

-These are made by examining the age distribution of the population at the time of a census. -e.g. the age distribution of trees in a 1 ha Douglas-fir forest at the time of measurement

Disadvantages of climax theory

-These people came up with the ideas that shaped ecology. -All theories except Whittaker's have been discredited because no scientists talk about climax systems anymore. -If you look at forests that haven't been disturbed for many years, you will see characteristics of the region, however, you cannot assume that this is normal. -When there is a disturbance we need to see it as a normal event in order to have correct management responses. -The climax concepts carried so much baggage because it was so difficult to save some of these theories that they just discredited all of them. -Some of this viewpoint still exist today and if we recognize these, we can see why some policies are wrong.

Descriptors (parameters) of a disturbance regime

-Things that characterize a disturbance regime: -Size: of area disturbed per event -Spatial distribution: (in relation to environmental gradients and in terms of large patch size vs. small patch size, etc.). Does it vary with topography? -Frequency: (mean number of events per time period). -Mean return interval: (mean number of years between successive events) (a disturbance returns 10 times per century). -Predictability: (i.e., do events occur regularly or sporadically? High statistical variance of the mean means low predictability. Simply minimum and maximum intervals between disturbance events are useful descriptors of predictability). -Rotation period: (this is an area equal to the whole area that has been disturbed) (aka turnover time or disturbance cycle; it is the average time requires to disturb an area equivalent to the size of the study area once). This is a combination of the size of the disturbance and its frequency. It refers to the time it takes to disturb an area.

Article 1: "The Influences of Climate on Aspen Decline

-This article was written by a Clark University graduate student, Philip Hanna. -He looked for the reason for the decline in aspen. -Key questions from his article: -Is annual aspen growth related to temperature and/or precipitation? -Is aspen mortality a sudden or multiyear process? -Does aspen mortality increase with drought?

Article 2: "Compounded Disturbance in Sub-Alpine Forests in Western Colorado Favor Future Dominance by Quaking Aspen"

-This article was written by another graduate student from Clark University, Caroline Mathews. -This was thinking about long term variability in species composition.

Steady-state concepts (Whittaker)

-This concept talks about literally what is happening in ecosystems. -A steady-state ecosystem is a constant biomass and nutrient content over time (there are inputs and outputs, but over time/decades there is no huge change). -Steady-state populations have constant population sizes. -Steady-state communities (aka compositional equilibrium) has species persistence. -In steady-state, there is no endpoint, it's just saying over centuries and decade, things haven't changed much. -The relative proportion of species isn't changing that much. This allows for change more than the climax theory. -In practice, the steady-state concepts displaced Whittaker's patterns climax theory. -E.g.: to interpret whether it is a steady-state community, you have to know the past of the specific ecosystems and the past species composition.

r-selection

-This happens in environments that are patchy and unpredictable, there is high risk to any individual, there is very little competition from other organisms. -The optimum evolutionary strategy is to produce large numbers of small offspring. -These species are r-strategists and have been produced by r-selection. -Rapid rate of increase in early stages of succession. -They have initially high survivorship curves, life span is short but growth rate is rapid.

Reorganized response

-This happens in the fine-scale gap phase regeneration mode. -Advance regeneration is released (either from seedlings or vegetative shoots). -Reorganization response also includes growth of non-tree species and lateral encroachment from surrounding mature trees. -Reorganization response (this doesn't involve new establishment, only trees that are shade tolerant because they were alive under the closed canopy. This is much quicker).

Monoclimax Theory (Cements)

-This is a classical theory of succession. -This theory states that the species composition and structure of the end community (what the dynamics of the area und up looking like aka the climax) are determined by the regional macroclimate. -The theory only requires a definite linear development toward the climatic climax. -Clements had the idea of monoclimax (one climate): the view was a convergence (intersection) of floristic composition (vegetation structure and plant community types) that's determined primarily by climate. -If you know the climate, you can determine what type of species will be there. This theory shows stability of the endpoint of succession. There is a strong role of climate control which is seen as the dominate factor determining what type of organisms. -This theory states: There is a strong role of climatic control of the climax; ensures stability of the endpoint of succession (permanence of climax); reaction (community control, dominance of autogenic change) as the mechanism (proximate cause) of change.

Stem Exclusion

-This is a phase with and without remains overstay trees, the phase following canopy closure. -Few or no new trees are established. -Move from density dependent tree mortality (competition). -New recruitment is excluded. -The stem exclusion stage is generally referred to as the "stem exclusion" or "dense" structure, both with and without residual (remaining) overstory trees. -However, sometimes a stem exclusion structure with snags, logs, and many species in a stratified condition can be referred to as the old growth structure.

Issues with Polyclimax theory

-This is also a false theory because this idea is only talking about climax. -This theory doesn't fit reality because we need to recognize disturbances as normal, usual occurrences, not as rare events.

White River Timber Reserve Example (G. Sudworth)

-This is an example from a historical report. -The writer of the report works for the GS. -"...there is a considerable quantity of dead standing spruce and fir mingled with the green timber. It extends in an interrupted, irregular, narrow belt from the region of Deep Lake and Carbonate westward to the headwaters of East Elk Creek. The dead timber amounts to from 10 to 25 per cent of the total stand and includes nearly, or quite, all the largest and oldest trees. They bear evidence of having died about twenty to twenty-five years ago." -Interpretation of written record: he makes a point to say that the largest and oldest trees are all attacked. Given the pattern of mortality, we can assume the disturbance is a bark beetle outbreak. The first part doesn't say this. -E.g. "It is impossible to state how many horses and cattle are annually ranged in this forest reserve; doubtless many thousands. Large numbers were constantly seen on the east, north, and west sides of the reserve." -Interpretation of written record: forest reserve, the precede of national forests. There was some type of agricultural land use. Gives us a glimpse of possible past events. Can get a sense of long term forest development. But don't know for sure.

Dendrochronology

-This is another method for finding the HRV. -Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings to the exact year they were formed in order to analyze atmospheric conditions during different periods in history. -Tells us when things happen in time through looking at tree core samples. Reconstructing historic range of variability. -Tree ring methods with tell you when the thing happened that you observe. -Collecting tree core samples is a common field method used to study a specific forest ecosystem. -E.g. see a patch in an ecosystem you can collect tree core samples from the patch edge. The growth of the rings will tell you when the patch occurred.

Understory Reinitiation

-This is self-thinning and fall of larger trees creates higher light levels in the understory. -In this phase, there is more vertical heterogeneity, more standing dead trees, and more fallen dead trees. -This goes on for a period of time until it turns to an old growth forest. -The third stage, understory reinitiation, involves further disturbance and the creation of gaps; at this point stratification develops, with layers of canopy, midstory, and understory appearing.

Stand Initiation

-This is the early development of a cohort before stand closure, not a lot of competition, more focus on stand development.

Emulation of natural forest disturbance (ENFD)

-This is the effort to match or surpass a natural forest disturbance, typically by imitation. -This is done by: -Maintenance of the historical (natural) range of ecosystem conditions. -Incorporating natural disturbance is usually more cost effective than suppressing it. -Use of ENFD implies an understanding of Historical Range of Variability of ecosystems. -If we know a forest has been maintained and the disturbance has been effective, we can try to create conditions that would have occurred by the disturbance. For this we have to know about long term forest development. This can be done by doing things that mimic the disturbance.

Are these disturbances within the HRV?

-This is the more difficult thing to determine because things are changing (climate change and other variability). -Hard to determine whether or not an observed disturbance is within the HRV (is the current disturbance a reflection of the past disturbances?). -Is this related to climate, human causes or is it normal? -E.g. Compare annual summer temperatures and estimates of forest area infested by spruce beetles. More recent years have larger areas effected by beetle outbreaks. There are also warmer temperatures in more recent years. -Warm temperatures in the winter stress trees and reduce defense mechanisms as well as speed up the life cycle of beetles and can keep them alive. -Outbreaks of native insects are getting larger with warmer temperatures. -It helps to understand ecological changes that are due to climate change. -Without HRV we couldn't relate today to past outbreaks or we wouldn't be able to put the size of disturbance into context (we need comparison, HRV allows this).

Seed rain

-This is the production at and dispersal of seeds to a site. This can be compared to the processes of birth rates and dispersals. This is how seeds begin dispersing and arriving at a site. -Plants have a genetically determined ability to produce an abundance of offspring. -The seed rain varies as a function of distance from the plant (this distance can be caused by things like wind). -The larger the disturbance (all other things equal, only thinking about seed rain), the longer the regeneration will take because there is a larger area that is far away from the uncut forest (it will take a while to get the seeds to be dispersed throughout the disturbed area). -The shape of the tree makes a difference when thinking about seed rain. -Regeneration will vary with tree shape. A circular shape vs a semicircle. -For a semicircle shaped patch, there is a larger proportion of undisturbed forest closer to the disturbed area (easier dispersal). -The more circular the patch, the longer the regeneration time because the disturbed area is further from the undisturbed area.

Patterns Climax Theory (Whittaker)

-This theory does not require discrete (separate) units. -Landscape consists of environmental gradients. -Tendency for a stable type of vegetation to develop will be different at each point along these gradients. -Therefore, the climax vegetation will be a spatial pattern of vegetation which reflects the spatial variation in the underlying physical environment. -Work in the 50s proposed that we view ecosystems using a continuum and recognize that ecosystems change along the continuum. -He put forth the last climax theory which was a combination of individualistic concept of plant association and the continuum/gradient concept. -Whittaker was trying to get us away from viewing ecosystems as being stable. -This is a combination of the continuum/gradient concept and the individualistic concept of the plant association. -In areas of relatively homogeneous regional climate, Whittaker recognized the most common climax type as the prevailing (current/existing) climax.

Southwestern Ponderosa Pine Forests and other Examples

-Three different photographs one from 1909, one from 1949, one from 1994. -It is hard to tell what is going on in the area. -Comparison between photographs of the same area taken in different years can be helpful to see the differences. -Images with mountains may be easier to depict because it's easier to see a disturbed area from far away. Can tell which side of the slope has changed and how much it has changed. -Some photographs might show regeneration starting which allows us to make better interpretations of the disturbance.

Tree ring examination and analyzing

-Through tree core sample examination, we can conclude that the same physical and biological processes that link current environmental processes with current patterns of tree growth must have in operation in the past. -Analyzing the sample provides specification of years with less or more growth compared to the growth of nearby years. This can help identify some of the major limiting factors of the rates of tree processes that constrain them. The sample can also pinpoint exact years of tree injury leading to hypothesis of past disturbance in the region. -You analyze a sample by marking it, counting the rings, and creating a skeleton plot for cross-dating. -Made marks on the graph paper if the rings were narrow, relative to those around it and "b" if they were wide. -If the ring is much wider, this is indicating an exceptionally good growing year. -If the ring is much narrower than those nearby, this marks a limiting factor that caused a very poor year of growth.

Tree morphology

-Tree morphology (study of plant growth habit, the overall architecture of a plant aka how it looks) can also tell the history of a forest. - The pattern of branching in a tree will vary from species to species, as will the appearance of a plant as a tree, herb, or grass. -E.g. One large tree with many lateral branches surrounded by small trees with less lateral branches (interpretation of this: used to be a field with one tree growing). -E.g. Can see the rock wall which tells us that this was previously an agricultural field. Can then examine the small tree cohorts to see how long ago it was a field.

Fine-scale gap phase mode

-Tree regeneration is dependent on canopy openings created by the death of the former canopy occupants. The gap can be created by either a small disturbance or the death of a single tree. -The difference between this and the continuous mode: the latter juveniles (new trees) will not reach the canopy unless the gap is created. They will remain suppressed or die in the absence of a gap whereas in the continuous mode, juveniles survive and slowly grow even in the absence of the gap. -Shade intolerant species can take advantage of this mode, but not the continuous mode. -The scale of the canopy gap needs to be defined but is usually small (e.g. canopy openings have a diameter of 4m to 40m).

Density-dependent vs. density-independent regulation (mortality)

-Two major properties of populations: variation in mean abundance and variation in temporal fluctuation. -These are types f mortality -Theories grouped into schools of thought: the biotic (density-dependent) school, and the abiotic (density-independent).

Relay floristics

-Two principles are considered as being involved in vegetation development on abandoned agricultural lands. -The first, called Relay Floristics, involves a succession of incoming and outgoing plants, each group invading the land, driving out its predecessor, and in turn preparing the site so as to be driven out itself. -Entry and growth of the latter species depends on earlier species. -Establishment occurs in stages over time. first there were crops then weeds came after, then grassland, shrubland and finally forrest came after respectively. -Sequence of species arriving later and the alteration of the site by the early colonizers.

Bivariate point patterns

-Two variables -There are 2 basic patterns, either positive or negative. -Positive association: the occurrences of A increases the likelihood of B. -Negative association: the presence of A decreases the probability of finding B.

Why does ecological succession occur?

-Under the changed conditions of the environment, the previously dominant species may fail and another species may become ascendant. Ecological succession may also occur when the conditions of an environment suddenly and drastically change. -Either allogenic or autogenic succession occurs. -The driving force behind succession, the reason why the change occurs, is not always the same. -We can classify according to the driving force with 3 main categories of succession: autogenic succession, allogenic succession, and biogenic succession. -Describes what happens to species composition over time.

Wind as a mechanical force

-Uprooting, and wind-snap. Regeneration and ecosystem structure after the disturbances will be clumped in the area of the canopy of the disturbed trees.

Continuum/Gradient Concept

-Views vegetation of a region as a series of plant species populations distributed independent of each other along the physical gradients of the environment. -Stressed the idea that plant species populations are independently distributed along environmental gradients (elevation, moisture) so that plant communities change gradually in their species composition. -We are now more concerned with what is happening over time (puts us closer to the bottom of the figure, (f.) continuum of vegetation change along environmental gradient). -E.g.: If you hike a mountain, generally tree species composition changes gradually, because tree distribution is relative to temperature and elevation, this changes over spacial distribution. More abrupt changes in shrub distribution is due to the soil composition (soil composition is a main factor that can change suddenly).

Life history "strategies" or "vital attributes"

-Vital attributes are 3 types of knowledge that allow for predicting the direction and patterns of succession in a disturbed ecosystem. 1. Method of persistence (the method of invasion and colonization and the method of persistence of propagules after disturbance). 2. Conditions for establishment (the conditions required for establishment and growth to maturity). 3. Critical life history events (time taken to reach critical stages in the life history). -E.g.: seed dispersal characteristics of dominant plants, photosynthetic efficiency of dominant plants at low light, competitive ability, plant longevity, r-selected or K-selected, plant biomass, rate of Net primary productivity, site of nutrient storage.

How do early successional species differ from late successional species?

-We can classify species as being early of late successional species based on their seed size. -Seed dispersal matters, because some seeds are extremely small and other plants force larger seeds. -Early successional species need to establish in areas that are free from competition, so the smaller and the lighter the seed is, the easier it is for the seed to do this. -Late successional species have more intense conditions and greater competition, so the larger seeds are more successful (there are less larger seeds, but these few large seeds have low mortality rates).

How do we find the historic range of variability?

-What are the ways to describe forest landscapes over previous, past centuries? -We can use observational field evidence, dendrochronology, written records, and maps and photographs.

(c.) Complex gradient and interlayer competition

-When species in any layer compete strongly with other species in that layer, but show a weak response to species in other layers (or species in other layer are responding to different environmental gradients) -This leads to very little overlap in the ranges of species within a layer. -This also leads to little or no grouping of species between layers. -Therefore, there is little association between species in different layers which means no clearly identifiable plant associations when looking along the gradient.

Secondary succession

-Where succession begins in an environment that has already been more or less modified by a period of occupancy by living organisms. -This is more common, and refers to areas that were previously vegetated. -Secondary succession is faster because the soil already has the nutrients and it doesn't have to be recreated. -If the soil is still intact, post-disturbance regeneration will be much quicker because the soil is still there.

Density-dependent mortality

-With density dependent feedback mechanisms, populations can avoid increasing to levels where they destroy their habitat or supply of resources, or they decrease to extinction. It matters how dense the trees are when thinking about mortality. -r-selected species tend to have a density -Even mortality driven by external forces has a component of density dependance. -E.g. We think of drought as an external factor. There is still a density component. -E.g. Parasites and predators (but there is a lag in the response time, so there is less balance). -E.g. Competition for food or other resources.

Written Records

-Written records are another indicator of the HRV. -Pros to examining written records: helpful in developing hypothesis because although they are rarely definitive, they can give a sense of disturbance. -There can be questions raised about using written records to determine the HRV: -Who wrote the record, are they telling the truth, is there evidence? Is there any deliberate lying? -There could be examples of written documents of things that the author believes are correct but doesn't actually know are true. -Writing can embellish to justify actions, or they can lead to unintentional misinterpretation. -Consider potential influences when writing especially regarding disturbances. Rare events/things are overrepresented in writing unless the person writing is deliberately writing about the non-rare things. -Also, names of species and locations can change over time making it difficult to use the collected data.

Spruce beetle outbreak

-Written records of graphs can also help. -There are 2 graphs that depict spruce beetle outbreak. -Accumulative data that shows the approximate extent of the outbreak and whether or not these types of disturbances are normal (disturbance regime). -You can't just say that: because there is a beetle outbreak, there is a problem. -Disturbances are a part of historic range of variability, so disturbances are normal occurrences.

Climatic influences on large, severe fires

-Year 0 is all fires. This represents the climate before and after fires. Cool and dry conditions vs. warm and wet conditions. -Interpretation: large fires occur in drier years (large severe fires are associated with drought). -Look at time period of past decades and see a trend of temperature with the frequency of large wildfires. -Is HRV relative in the context of climate change? We can say that the occurrence of any one large fire isn't abnormal, but it doesn't take away from the fact that large fires are increase as the climate changes. -Different places in the world have different types of disturbances. -There is a direct and indirect effect of climate change.

Zonation

-Zonation is the distribution of plants or animals into specific zones according to such parameters as altitude or depth, each characterized by its dominant species. -Zonation helps with potential goals of resource management. -Any particular area might meet more than one goal, some might be mutually exclusive. -We think of different zones for different goals. -One zone we maintain something different than another zone. -E.g.: HRV in Europe vs North America. In Europe it is being applied for cultural reference. Management happens with farmers being paid by government to keep vallies looking like valleys.