4) Potential net primary productivity (NPP-p)
We used the Thornthwaite model to calculate the potential NPP
(NPP-P) (Lieth and Box, 1972) as follows:
\(\text{NPP}_{p}=3000\times[1-\exp^{-0.0009695(V-20)}]\),
where V is the annual
actual evapotranspiration (mm), and NPP-P is measured in
units of g·C·m−2·yr−1.
The annual actual evapotranspiration data were retrieved from the
MOD16A3 dataset of the NTSG, in which the evapotranspiration values are
determined using the Penman–Monteith equation (Mu et al., 2007). The
parameter used to estimate the NPP-P; i.e., the actual
evapotranspiration, depends on solar radiation, temperature,
precipitation, air pressure, and wind speed. Blank spaces on the
evapotranspiration map (Figure 2) indicate an absence lack of data.