Eco Chap 20
Where is oceanic NPP the greatest? Why?
Oceanic NPP peaks at mid-latitudes, in zones of upwelling .
Is all fixed carbon used to build tissue? Explain.
no only half is used
What is NDVI, and how is it calculated? What does a high NDVI value indicate?
normalized difference vegetation index NDVI= (NIR-red) (NIR +red)
What is chemosynthesis? Are these organisms heterotrophs or autotrophs?
the synthesis of organic compounds by bacteria or other living organisms using energy derived from reactions involving inorganic chemicals, typically in the absence of sunlight. heterotrophs
What limits NPP in lakes? How is it measured?
limited by the supply of both phosphorus and nitrogen The NPP response is measured by changes in chlorophyll concentrations or numbers of phytoplankton cells
How are chlorophyll concentrations measured, and how can these measurements be used to estimate NPP?
Chlorophyll concentrations can be estimated using remote sensing techniques that rely on the reflection of solar radiation Indicators of NPP that are based on chlorophyll concentrations can overestimate NPP if the vegetation is not physiologically active, as in boreal forests in winter, but remote sensing generally provides the best estimate for NPP at regional to global scales.
23. What is secondary production? A) What are these organisms called? What are the four different types? B) How are stable isotopes used to determine an organism's diet? C) How do you calculate net secondary productivity? D). What does net secondary productivity depend on? E) How does secondary productivity differ between endotherms and ectotherms?
Energy derived from consuming organic compounds produced by other organisms. A)Heterotrophs include archaea, bacteria, fungi, animals, and a few plants. B)Isotopic measurements of preserved bone specimens have been used to study the diets of extinct animals as well as modem ones. D) Net secondary production by a heterotroph depends on the quality of its food, related to its digestibility and nutrient content E)
Where are the highest rates of NPP on land found? Why?
Highest rates of NPP on land are found in the tropics (long growing seasons and high precipitation).
What types of organisms are most associated with secondary productivity?
Most is associated with detritivores, primarily bacterial and fungi.
19. In the open ocean, what is NPP mainly from? a) What is picoplankton? B) What else contributes to the NPP of the marine system? C) What is the main limiting nutrient in the open ocean? What is another one that may influence NPP?
NPP in the open ocean is derived primarily from phytoplankton, including a group referred to as the picoplankton, consisting of cells smaller than 1 ~m. A)the fraction of plankton composed by cells between 0.2 and 2 μm that can be either prokaryotic and eukaryotic phototrophs and heterotrophs B) Floating mats of seaweed, kelp forests. C) Nitrogen, iron.
Why is it important to understand NPP in a system?
NPP is the ultimate source of energy for all organisms in an ecosystem and thus determines the amount of energy available to support that ecosystem. NPP provides a metric for examining ecosystem health. NPP is intimately associated with the global carbon cycle, and it is therefore an important influence on global climate change
What is Leaf Area Index (LAI)? A)When the LAI is below 1, what does this indicate? If the LAI is above 1, what does this indicate? B) If a higher LAI means more area to capture light and an increased photosynthetic rate, what limits the number of layers of leaves in a system?
One half the total green leaf area per unit ground surface area. A) if it is below 1 there is no cover between the tree and the ground. If it is higher than 1 then there are more layers of leaves. B) Eventually, the respiratory costs associated with adding leaf layers outweigh the photosynthetic benefits. Plants generally match their leaf area index to the climate conditions and the supplies of resources, particularly water and nutrients, in order to maximize carbon gain.
What is primary production? A)What types of organisms are primary producers? B)How is this energy stored? Why is this important for measuring primary productivity? C)What is gross primary productivity (GPP)? What does it depend on? D) What influences photosynthetic rate?
Primary production is the generation of chemical energy by autotrophs A) plants, lichens, moss, bacteria, algae B) Stored as carbon compounds in plant and phytoplankton tissues C) The amount of carbon fixed by the autotrophs in the ecosystem. Depends on the climate. D) climate influences the rate.
What is net primary productivity (NPP)? How is it different from gross primary productivity?
The balance between GPP and autotrophic respiration. NPP is the energy left over for plant growth, plant reproduction, and consumption by herbivores and detritivores. It also represents the total net input of carbon into ecosystems.
Between terrestrial and aquatic systems, which has a higher proportion of NPP that becomes part of secondary production?
The fraction is greater in aquatic ecosystems than terrestrial.
What is the variation in NPP in estuaries correlated with?
Variation in NPP among estuaries is correlated with variation in nitrogen inputs from rivers
Variation in NPP in terrestrial biomes is associated mostly with what two factors? What affects NPP variation most in aquatic ecosystems?
Variation in terrestrial biomes = leaf area index and length of growing season. Variation in aquatic ecosystems = variation in nutrient inputs.
15. What other factors can have an effect on the NPP of a system? A) Why might there be different responses to different climatic conditions between different areas of varying species composition? B) What controls NPP in terrestrial ecosystems? C) Why does the addition of water to a dry system not always increase the NPP of the system?
Water A)Cloud cover over long periods lowers available sunlight. High amounts of precipitation leach nutrients from soils, and high soil water content results in hypoxic conditions that cause stress for both plants and decomposers. B)water
Why is NPP often low in rivers and streams? A) Where is most energy derived from? B) According to the river continuum concept, the importance of in-stream NPP increases with what? C) How do suspended sediment and nutrients affect NPP?
Water movement limits the abundance of phytoplankton, except where the water velocity is relatively low. AThe majority of the energy in those ecosystems is derived from terrestrial organic matter. B)the increasing importance of in-stream NPP as the river flows downstream C)Suspended sediment in rivers can limit light penetration; thus, turbidity often controls NPP. Nutrients, particularly nitrogen and phosphorus, can also limit NPP in streams and rivers
What is the definition of an ecosystem based on energy flow?
all of the components of an ecological system, biotic and abiotic, that influence the flow of energy and element. Elements are nutrients, pollutants
What is the most important factor that affects NPP? A) How does NPP change with precipitation? Why? B) How does NPP change with increased annual temperature? Why? What happens to the net ecosystem exchange (NEE)?
climate A) as the avg annual precipitation increases npp increases B) NPP increases with average annual temperature. NPP is directly linked to water availability and temperature. The loss of carbon from ecosystems due to respiration of heterotrophic organisms also increases at warmer temperatures, so NEE may potentially decrease
What organism is responsible for most of the photosynthesis in aquatic habitats? A) Why don't harvest techniques work for this system?
phytoplankton A)These organisms have much shorter life spans than terrestrial plants, so the biomass present at any given time is very low compared with NPP
How are CO2 concentrations measured in a closed chamber used to estimate NPP? A) Where does this CO2 in this system come from? Is it just plants? B) What does this measurement give you? C) What must you do to calculate the NPP of the system?
placing a chamber around stems and leaves, whole plants, or whole stands of plants. A)The emissions of C02 to the atmosphere in such a closed system are from respiration by the plants and heterotrophs, including microorganisms in the soil and animals in the forest. B)Thus, the net change in C02 inside the system results from the balance between GPP and total respiratory release by the plants and the heterotrophs. C)Heterotrophic respiration must be subtracted from NEE to obtain NPP; as a result, NEE provides a more refined estimate of ecosystem carbon storage than NPP.
Why does NPP vary with succession stage? During which stage is NPP that highest, and why?
succession can therefore influence gains or losses of C02 from ecosystems, thereby affecting atmospheric C02 concentrations. Most ecosystems have their highest NPP at mid-successional stages. Several factors contribute to this pattern, including the tendency for the proportion of photosynthetic tissues, plant diversity, and nutrient supply to be highest at mid-successional stages.
How is NPP in a terrestrial ecosystem measured? A) Why is this only reasonable for aboveground NPP measurements? B) Why is this technique only useful for small plants in an area of low diversity? C) Why is it difficult to measure belowground NPP? D) What can be used to measure belowground NPP?
the increase in plant biomass during the growing season by harvesting plant tissues in experimental plots, measuring biomass, and scaling the results up to the ecosystem level A)the aboveground biomass can be harvested from plots at the start of the growing season and again when the amount of plant biomass reaches its maximum. The difference in plant biomass between the two harvests is used as an estimate of NPP. B)In forests, the radial growth of wood must be included in estimates of NPP. In the tropics, plants may continue to grow throughout the year, and tissues that die decompose rapidly, making the use of harvest techniques problematic C)growth belowground is more difficult because root growth is more dynamic than the growth of leaves and stems. The proportion of NPP in roots exceeds that in aboveground tissues in some ecosystems: in grassland ecosystems, for example, root growth may be twice that of aboveground leaves, stems, and flowers combined D)The use of minirhizotrons, underground viewing tubes outfitted with video cameras, has led to advances in the understanding of below ground production processes
How can a plant direct tissue growth to help it survive in a harsh environment? Other than growth, where might energy from NPP be allocated?
with the left over carbon not used in respiration is then used for growth. They allocate carbon to the growth of different tissues. Can also be used as storage and defense
