NR 228 EXAM 2 QUESTIONS AND
THEIR REVIEWED ANSWERS
Carbon enters an ecosystem as...
GPP
Carbon returns to the atmosphere via...
respiration or disturbance or is transported to other
ecosystems
how do plants lose carbon (in addition to respiration)?
6 ways
1. litterfall 2. root exudation 3. michorizal fungi 4. herbivory
5. human harvest 6. a volatile organic compound loss
NPP is limited by precipitation at most locations, why
not temperature?
many hot ecosystems are also DRY ecosystems (if we left
out the really dry ecosystems, temp could be a good
predictor of NPP)
what limits productivity and growth besides water and
nutrients?
light availability and CO2
limitations to growth in the tundra?
nutrients (N)
limitations to growth in the desert?
water and N (co-limited)
limitations to growth in the tropics?
too much water, not enough oxygen
limitations to growth in boreal forests?
N and other nutrients
, climate controls over NPP are mediated primarily
through the availability of
_________________________ ________________.
belowground resources
MAJOR factor explaining biome differences in NPP
the length of the growing season
A desert or grassland can never be as productive as a
tropical forest- even with ample water and nutrients.
WHY?
leaf area, leaves are larger in the tropics and will always
be more productive than smaller leaves (but plants
adapted to dry areas are less likely to die in a drought,
importance of extreme climates, not average climate)
how do plants respond to long-term environmental
change?
plant traits!
- plants adjust resource acquisition (more leaves, more
roots) to capture limiting resource
- plants can increase supply of limiting nutrients
(mycorrhizae)
- plants can retain nutrients when they are in short supply
(resorption)
- plants are usually limited by more than one thing
plants allocate to leaves when light is...
limiting
plants allocate to roots when the soil is...
dry or nutrient poor
plants constantly adjust allocation which prevents
overwhelming limitation by any one resource, BUT ...
tends to make plants limited by multiple resources
NPP in most ecosystems is limited most strongly by...
THEIR REVIEWED ANSWERS
Carbon enters an ecosystem as...
GPP
Carbon returns to the atmosphere via...
respiration or disturbance or is transported to other
ecosystems
how do plants lose carbon (in addition to respiration)?
6 ways
1. litterfall 2. root exudation 3. michorizal fungi 4. herbivory
5. human harvest 6. a volatile organic compound loss
NPP is limited by precipitation at most locations, why
not temperature?
many hot ecosystems are also DRY ecosystems (if we left
out the really dry ecosystems, temp could be a good
predictor of NPP)
what limits productivity and growth besides water and
nutrients?
light availability and CO2
limitations to growth in the tundra?
nutrients (N)
limitations to growth in the desert?
water and N (co-limited)
limitations to growth in the tropics?
too much water, not enough oxygen
limitations to growth in boreal forests?
N and other nutrients
, climate controls over NPP are mediated primarily
through the availability of
_________________________ ________________.
belowground resources
MAJOR factor explaining biome differences in NPP
the length of the growing season
A desert or grassland can never be as productive as a
tropical forest- even with ample water and nutrients.
WHY?
leaf area, leaves are larger in the tropics and will always
be more productive than smaller leaves (but plants
adapted to dry areas are less likely to die in a drought,
importance of extreme climates, not average climate)
how do plants respond to long-term environmental
change?
plant traits!
- plants adjust resource acquisition (more leaves, more
roots) to capture limiting resource
- plants can increase supply of limiting nutrients
(mycorrhizae)
- plants can retain nutrients when they are in short supply
(resorption)
- plants are usually limited by more than one thing
plants allocate to leaves when light is...
limiting
plants allocate to roots when the soil is...
dry or nutrient poor
plants constantly adjust allocation which prevents
overwhelming limitation by any one resource, BUT ...
tends to make plants limited by multiple resources
NPP in most ecosystems is limited most strongly by...
