ecology chapter 20

primary production

the rate at which chemical energy in an ecosystem is generated by autotrophs, derived from the fixation of carbon during photosynthesis and chemosynthesis

majority of energy on earth comes from photosynthesis. True or False?

True

Gross primary production

the amount of energy that autotrophs capture by photosynthesis and chemosynthesis per unit of time.

The GPP in most terrestrial ecosystems is equivalent to the total of all plant photosynthesis. True or False?

True

The GPP of an ecosystem is controlled by…

climate through it’s influence on rates of photosynthesis

Leaf area index

the area of leaves per unit ground area 

what is labeled?

1. ecosystem photosynthesis increases as the leaf area index increases 

2. but the incremental carbon gain is less for each additonal leaf layer 

3. shading of the leaves below the top of the canopy increases with the addition of each new leaf layer 

4. Layer 1 is at the top of the canopy and layer 15 is at the bottom 

A plant uses all of the carbon it fixes by photosynthesis. True or False?

False, A plant uses approximately half of the carbon it fixes by photosynthesis in cellular respiration to support biosynthesis and cellular maintenance.

All living plant tissues lose carbon via….

respiration

plant that have a large proportion of nonphotosynthetic stem tissue tend to…

have higher overall respiratory carbon losses than herbaceous plants. 

plant respiration rates increase with increasing temperatures and as a result…

respiratory carbon losses are higher in tropical forests than in temperate and boreal forests

net primary production

the amount of energy per unit of time that producers capture by photosynthesis and chemosynthesis, minus the amount they use in cellular respiration. 

The equation of net primary production

NPP = GPP - respiration

NPP of a terrestrial ecosystem is the amount of energy captured by autotrophs that results in….

an increase in living plant matter, or biomass

the energy left over for plant growth, plant reproduction, defense, and consumption by herbivores and detritivores 

NPP

what is labeled?

1. in nutrient-poor biomass, such as tundra and grasslands, over 50% of NPP is allocated to roots

2. in biomes where competition for light is important, a smaller percentage of npp is allocated to roots.