Quantification of water resource utilization efficiency as the main driver of plant diversity in the water-limited ecosystems

Abstract

Identifying the drivers of species richness is a crucial for biodiversity conservation and community ecology. In this paper, the maximum utilization efficiency of water resources available to community is determined as the assembly law in an ecologically stable community with limited water resources. A plant community diversity model that incorporates water potential impedance is established, and the optimization model of community biodiversity structure was obtained based on water niche is also derived. It is shown that this optimization model can theoretically derive a species-area function similar to the traditional island biogeography curve, and it can also verify the predicted values of the species-area relationship experimentally and validated by long-term observations of plant diversity survey data. According to the model analyses, the total number of individuals (N) and the number of species (S) are determined by the combination of the water resources factors (the total quantity of available water resources in the growth season), the individual biological factors (the water consumption per unit mass of species in unit time), the complementary factors of inter- and intra-species water niche (the difference in water potential depending on the water use efficiency of the community), and plant community function factors (the total productivity of plant community). And as the area of plant communities increases, the heterogeneity of the water environment has increased. By adaptation and coevolution, more species are able to go through environmental and biological filtration, becoming community species that can utilize more available water resources at different spatial scales. Changes in water resources resulted in the community maximizing the utilization efficiency of water resources by adjusting the number and abundance of species. The main driving force for the increasing number of species is the full utilization of available water resources.