If a grassland has a GPP of 1,600 g/m^2/year and plants use 1,000 g/m^2/year for respiration, the NPP is:...

1) If a grassland has a GPP of 1,600 g/m^2/year and plants use 1,000 g/m^2/year for respiration, the NPP is:
2) Select ALL factors that directly affect primary productivity in ecosystems. (Choose 4)
a) Sunlight availability
b) Water availability
c) Soil nutrient levels
d) Temperature
e) Number of herbivores
f) Presence of decomposers