Relationship Between Bryophyte Diversity And Site Factors Under Different Environmental Gradients

Bryophyte plants,important components of forest ecosystems,play important roles in water conservation,nutrient cycling,and biodiversity maintenance.We established a 4-ha permanent monitoring plot in a subtropical forest in Kanghe Provincial Nature Reserve in Guangdong province.We conducted a bryophyte plant survey in the plot and test the effects of environmental factors on species composition,distribution patterns,alpha and beta diversity of bryophyte plants.The main results are as follows:(1)We recorded 40 species of bryophytes from 23 families and 34 genera in the monitoring plot.Among 40 bryophyte species,14 species from 7 families and 11 genera are liverwort s and 26 species from 16 families and 23 genera are mosses.Flora element analysis of dominant species showed that dominant species of bryophytes are tropical or subtropical plants.Beta diversity of bryophytes varied among plots.Abundance and species richness were highest at the mid-elevations and lowest at the high-elevations.The Shannon-wiener index and evenness index varied unregularly among plots.The variation magnitude of the evenness index was much smaller than that of the Shannon-Wiener index.(2)Results of MRPP showed that no significant differences of species composition of bryophytes across aspects,across total nitrogen content classes,across total potassium content classes,across soil organic material classes,across canopy openness classes,and across total transmitted solar radiation classes.Species composition differed highly significantly across elevational classes,across total phosphorus content classes,and across soil texture classes;differed significantly across soil moisture classes.(3)Results of Kruskal-Wallis test showed that beta diversity differed highly significantly across the Shannon-Wiener index classes and across dominance classes;differed significantly across richness classes and across abundance classes;differed marginally significantly across the evenness classes.(4)Results of correlations between beta diversity and its drivers showed that beta diversity was significantly correlated with total nitrogen content,total phosphorus content,richness,and the Shannon-Wiener index;but not significantly with soil organic material,totalpotassium content,soil moisture,soil bulk density,canopy openness,total transmitted solar radiation,abundance,dominance,and evenness.(5)Species richness was significantly and negatively correlated with soil organic material content and elevation;significantly and positively with total phosphorus content and total potassium content;but not significantly with other environmental factors.Evenness was significantly and negatively correlated with canopy openness and total transmitted solar radiation;but not significantly with other factors.Shannon-Wiener index was significantly and negatively correlated with elevation and aspect;significantly and positively with total phosphorus content;but not significantly with other factors.Abundance was significantly correlated with soil organic material content;significantly and positively with total potassium content and aspect;but not significantly with other factors.Dominance was significantly and positively correlated with canopy openness,total transmitted solar radiation,and elevation;significantly and negatively with soil bulk density;but not significantly with other factors.(6)Results of random forest showed that bryophyte beta diversity was strongly affected by evenness,elevation,Shannon-Wiener index,dominance,species richness,soil organic material,total nitrogen content,and total phosphorus content.