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.
Methods: Initially, we used correlation
analysis and a 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 w 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 marsh region, temperate humid
region, and semi-humid marsh region, and (b) lower in the Tibetan Plateau marsh
region, temperate arid and semi-arid marsh region, and coastal marsh 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 influencing
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.