11 public questions tagged with this topic.
Tropical rainforests contribute the most to global primary productivity due to their high biodiversity and favorable climatic conditions.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
NPP is the energy available to herbivores after accounting for the energy used in respiration by plants.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
Net primary productivity (NPP) is the energy available to herbivores after subtracting respiration loss from GPP.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
NPP is always less than GPP because it accounts for the energy used in respiration by plants.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
“Nutrients and abiotic factors” for what controls biomass accumulation in bottom-up control. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Predators”, “Prey populations”, “Carnivores”—refer to di
Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 4
Net community productivity is the net rate at which organic carbon accumulates in an ecosystem after respiration by both autotrophs and heterotrophs. Ecosystem respiration, RE, includes plant respiration plus respiration by consumers and decomposers, so subtracting RE from gross primary productivity gives NCP. Carbon accounting separates gross fixation from respiratory expenditure. Gross primary productivity records all photosynthetic carbon fixation; net primary productivity subtracts autotrophic respiration, while net community productivity subtracts total ecosystem respiration. Keeping flux
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17
The ratio NPP/biomass compares how much new producer material an ecosystem generates relative to its existing standing biomass during a specified time. It is closely related to production-to-biomass ratio and biomass turnover rate. A grassland may have modest standing biomass yet replace a large fraction annually, producing a high ratio, whereas a mature forest stores enormous amounts of wood but adds a smaller fraction each year, producing a lower ratio. Normalizing production by biomass therefore enables comparison among biomes that differ greatly in size and growth form. NPP alone measures
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17
In the light-and-dark bottle method, a dark bottle blocks photosynthetically active radiation while retaining plankton and microbes from the water sample. Without light, photosynthetic oxygen production stops, but cellular respiration continues and consumes dissolved oxygen. The decline in oxygen during incubation estimates community respiration. A transparent light bottle permits both photosynthesis and respiration, so its oxygen change estimates net community production. Combining the two changes gives an estimate of gross primary production: oxygen produced overall equals the net increase i
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17
Net primary productivity is the rate at which producers accumulate new organic matter after meeting their own respiratory costs. Gross primary productivity represents all carbon fixed or energy captured by autotrophs. Autotrophic respiration consumes part of that material to support cellular maintenance, active transport, tissue construction, and repair. The balance is therefore NPP = GPP − R, where R in this formula means respiration by primary producers, often written Ra. NPP supplies plant growth and reproduction and is the energy potentially available to herbivores and decomposers. Adding
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17
Herbivory can reduce plant productivity most clearly in unproductive ecosystems because plants already face strong nutrient or water limitation and replace lost tissue slowly. Removal of photosynthetic area then deepens resource stress. In productive systems, moderate grazing may be compensated by rapid regrowth, altered allocation, nutrient recycling, or reduced self-shading, although heavy grazing can still depress production. The effect therefore depends on grazing intensity, plant traits, and resource availability. Energy is lost as metabolic heat at every trophic transfer, while elements
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17-19
The keyed sequence, desert greater than tundra greater than tropical forest greater than temperate forest, is not scientifically consistent with established comparisons of net primary productivity per unit leaf area. Water limitation suppresses desert carbon gain, while warm, wet tropical forests generally sustain high daily photosynthesis. It also conflicts with rows 65 and 80 of this workbook, which place deserts below temperate and tropical systems. The key should therefore be treated as erroneous rather than rationalised. Energy is lost as metabolic heat at every trophic transfer, while el
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17-19
