Chapter 20: Production Flashcards
When was the first use of the term ecosystem and what did it refer to?
-Tansley (1935)
-Refers to all the components of an ecological system that influence the flow of energy and elements
Ecosystem Concept
integrates ecology with other disciplines such as geochemistry, hydrology, and atmospheric science
Where does the energy in ecosystem originate?
autotrophs
Primary Production
chemical energy generated by autotrophs during photosynthesis and chemosynthesis
Source of Energy for all organisms
primary production
Where are fossil fuels derived from?
primary production
Where is energy assimilated from autotrophs stored?
carbon compounds in plant tissues
Primary Productivity
rate of primary production
Gross Primary Production (GPP)
total amount of carbon fixed by autotrophs
What is GPP controlled by?
-climate through its influence on photosynthetic rate
-Leaf area index: leaf area per unit of ground area
What is the variation in LAI among biomes?
-less than 0.1 in Arctic tundra (less than 10% of the ground surface has leaf cover)
-12 in boreal and tropical forests (12 layers of leaves between the canopy and the ground, on average)
What is the relationship between shading and photosynthesis?
-When shading increases, the incremental gain in photosynthesis for each added leaf layer decreases
-Eventually, the respiratory costs associated with adding leaf layers outweigh the photosynthetic benefits
How much fixed carbon do plants use in photosynthesis for cellular respiration?
about half
What type of plants have higher respiratory carbon losses?
plants with a lot of non-photosynthetic tissue (trees)
What increases with temperature?
respiratory rate
What biome has the higher respiratory losses?
tropical forests
Net Primary Production (NPP)
GPP-Respiration
NPP
-the amount of energy captured by autotrophs that results in an increases in biomass (living plant matter)
-the energy left over for plant growth and for consumption by detritivores and herbivores
How do plants respond to environmental conditions?
allocating carbon to the growth of different tissues
How does allocation of NPP to storage products affect the plant?
provides insurance against loss of tissue to herbivores, disturbances such as fire, and weather events such as frost
How much NPP may be allocated to defensive secondary compounds?
up to 20%
What varies during succession and why?
-NPP as LAI and species composition all change
When is NPP the highest?
usually during intermediate stages when plant diversity and nutrient supply tend to be highest
What happens to NPP and LAI in old growth forests?
-NPP may decline as LAI and photosynthetic rates decrease
-But Old-Growth ecosystems have large pools of stored carbon and nutrients for many animal species
-Decrease in NPP over time is less pronounced in grasslands than in forests
