Quantifying Plant Species α-Diversity Using Normalized Difference Vegetation Index and Climate Data in Alpine Grasslands

Quantitative plant species alpha-diversity of grasslands at multiple spatial and temporal scales is important for investigating the responses of biodiversity to global change and protecting biodiversity under global change. Potential plant species alpha-diversity (i.e., SRp, Shannon(p), Simpson(p) and Pielou(p): potential species richness, Shannon index, Simpson index and Pielou index, respectively) were quantified by climate data (i.e., annual temperature, precipitation and radiation) and actual plant species alpha-diversity (i.e., SRa, Shannon(a), Simpson(a) and Pielou(a): actual species richness, Shannon index, Simpson index and Pielou index, respectively) were quantified by normalized difference vegetation index and climate data. Six methods (i.e., random forest, generalized boosted regression, artificial neural network, multiple linear regression, support vector machine and recursive regression trees) were used in this study. Overall, the constructed random forest models performed the best among the six algorithms. The simulated plant species alpha-diversity based on the constructed random forest models can explain no less than 96% variation of the observed plant species alpha-diversity. The RMSE and relative biases between simulated alpha-diversity based on the constructed random forest models and observed alpha-diversity were <= 1.58 and within +/- 4.49%, respectively. Accordingly, plant species alpha-diversity can be quantified from the normalized difference vegetation index and climate data using random forest models. The random forest models of plant alpha-diversity build by this study had enough predicting accuracies, at least for alpine grassland ecosystems, Tibet. The proposed random forest models of plant alpha-diversity by this current study can help researchers to save time by abandoning plant community field surveys, and facilitate researchers to conduct studies on plant alpha-diversity over a long-term temporal scale and larger spatial scale under global change.

Automated summary

Quantifying plant species alpha-diversity in grasslands at different scales is crucial for studying the impact of global change on biodiversity and protecting biodiversity under global change. This study used multiple methods to quantify the alpha-diversity, and found that random forest models performed the best. The models can accurately predict alpha-diversity based on normalized difference vegetation index and climate data, providing a useful tool for studying plant alpha-diversity in alpine grassland ecosystems.