Aims Determining the distribution pattern and drivers of broad-scale species richness is significant for predicting the response to biodiversity and formulating conservation programs to reduce biodiversity loss. This paper discusses the distribution pattern and driving mechanism of plant species richness obtained from nationwide field survey of Phragmites australis marsh data, combined with climate, geography, soil, and other environmental factors.
Method Initially, we used correlation analysis and general linear model to determine the relationship between species richness and annual mean temperature (MAT), annual precipitation, minimum temperature of coldest month (MTCM), altitude, latitude, longitude, soil pH, soil organic carbon (SOC), soil total nitrogen (TN), and topographic wetness index (TWI). Then, we used hierarchical partitioning to determine the most important drivers of species richness utilizing the following nine variables: soil factors (soil pH, SOC, TN), climate factors (MAT, annual precipitation, MTCM), geography factors (latitude, altitude), and water regime. Finally, piecewise structural equation modeling was used to assess the direct and indirect effects of these nine variables on plant species richness.
Results (1) The overall richness of plant species in Chinese P. australis marshes was (a) higher in the subtropical humid zone, temperate humid and semi-humid zone, and (b) lower in the Tibetan Plateau region, temperate arid and semi-arid zone, and coastal region. (2) The richness of plant species in P. australis marshes was significantly positively correlated with annual precipitation, SOC, TN, and latitude, but negatively correlated with the MAT, MTCM, soil pH, and altitude. (3) Soil factors, especially soil pH, were the most important factors affecting the richness of plant species in P. australis marshes, followed by water regime, climate factors, and geography factors. (4) Piecewise structural equation modeling showed that soil factors, water regime, and climate factors directly affected the richness of plant species, while geography factors indirectly affected the species richness of plants by regulating soil factors, water regime, and climate factors.
Conclusion Species richness of plants in Chinese P. australis marshes is spatially heterogeneous between the different regions. The species richness distribution pattern is affected by a combination of factors, where soil factors are the key environmental factors affecting the species richness pattern of plants. This study provides a new understanding of the broad-scale distribution pattern of plant diversity and the pattern’s conservation in P. australis marshes.