Net primary productivity and plant species richness

Evapotranspiration, ET, is the most important climatic predictor of the net primary productivity, NPP, of ecosystems. It has also been shown that ET is the single climatic variable that best predicts plant species richness, n. We investigate whether a new theoretical expression for NPP in terms of climatic variables can be utilized to predict the variability of n across geographic regions. Our main hypothesis is that the most important input to the variability of n is climatic. We evaluate the proposed theoretical approach using a wide range of experimental data, collected from the literature. Our results appear to confirm the hypothesis underlying the research and are, therefore, compatible with the existing observations that n is strongly correlated with NPP.