Aims: The aim of the present study was to determine the most important environmental factors affecting aboveground net primary production (ANPP) of plants along the altitude gradient in QezelOzan-Kosar rangelands, Iran.
Materials & Methods: Eight sites along the altitude gradient were selected, in each of which three transects parallel and perpendicular to the slope were established. Along each transect (totally 240 plots), ANPP and soil samples were measured. Using digital elevation model (DEM) map, the maps of slope, aspect, elevation, topographic index (CTI), stream power index (SPI), plan curvature (PC), precipitation and temperature were extracted. The soil parameters measured in soil laboratory. To determine the important effective factors, principal component analysis (PCA) was used. Moreover, the ANPP prediction equation was simulated using the parameter which had the greatest impact and correlation with ANPP (precipitation), using 2^nd-order polynomial model and mapped further.
Findings: The results of PCA revealed that six components had the highest effect on the ANPP variations (76.35% of ANPP variations). The result of simulated equation and map indicated acceptable accuracy (R²= 0.95, RMSE= 0.73).
Conclusion: The results of the present study highlight the importance of topographic, climatic, and soil factors in ANPP variations, and can be used to manage QezelOzan-Kosar rangelands for establishing balance between biomass and carbon of the ecosystem and ecosystem supply and demand.