Study On The Diversity Of Woody Plants Of Natural Forest Communities In Southwest Hubei

A key subject in ecology is to explore the patterns and causes of species diversity in plant communities,which is supposed to provide significant contributions to the conservation and sustainable utilization of biodiversity.One of the hotspots of plant diversity in China is southwest Hubei,which is also known as the major distribution areas of natural forests in Central China with diverse forest community types.Regarding to the patterns and causes of species diversity in forest communities in southwest Hubei,existing analyses and understandings remain far from being enough.The natural forest communities in Xingdoushan National Natural Reserve are representative.Our study focused on the four natural forest communities in Xingdoushan Reserve,and a total of 79 plots were established in these communities.We analyzed the species compositions,community structure,and environmental conditions of these communities.On these bases,we further analyzed the patterns and drivers of species,phylogenetic,and functional diversity of these communities.The main results are as followings:(1)From the perspective of species composition,Fagus lucida community was highly different from Pinus massoniana community and Cunninghamia lanceolata community,while Carpinus fargesiana community was the transitional type among the other communities.In Fagus lucida community,no species showed extremely strong dominance,while some of the species in the other communities are extremely dominant.Fagus lucida community and Pinus massoniana community had higher basal area than the other communities;individuals in Pinus massoniana community and Cunninghamia lanceolata community were uneven in diameter at breast height compared with those in the other communities.Cunninghamia lanceolata community had lower stem density than the other communities.With enlarging the number of sampled individuals or plots,the species accumulation rate was generally highest in Carpinus fargesiana community but lowest in Cunninghamia lanceolata community.(2)Species abundance distribution(SAD)of each community could be well fitted by either log-series model or lognormal model,but log-series generally provided better fits than lognormal,especially for the SAD of Fagus lucida community.The rarefied SADs of the four communities were significant different: the rarefied SAD of Fagus lucida community was more logseries-like,but that of Cunninghamia lanceolata community was less logseries-like.Within Carpinus fargesiana community,the standard deviation of species abundance decreased with increasing soil p H and total phosphorus(TP),while Berger-Parker index increased with increasing soil available phosphorus(AP).Within Fagus lucida community,environmental factors had non-significant effects on plot-level SADs.Within Cunninghamia lanceolata community,standard deviation of species abundance decreased with decreasing TP,while Berger-Parker index and the parameter of geometric series model increased with increasing AP.Within Pinus massoniana community,above measurements of plot-level SAD increased with decreasing elevation and increasing AP and AK.(3)Carpinus fargesiana community had the highest species ?-diversity,Cunninghamia lanceolata community and Pinus massoniana community exhibited intermediate diversity level,while Fagus lucida community exhibited the lowest levels.Within Fagus lucida community,species ?-diversity did not exhibit significant changes along environmental gradients.Within Cunninghamia lanceolata community,species ?-diversity decreased with increasing AP.Within Pinus massoniana community,species ?-diversity increased with increasing elevation but decreased with increasing AP and available potassium(AK).Species ?-diversity,determined by both spatial and environmental factors,did not significantly differ among communities.Spatial factors exhibited stronger effects than environmental factors on species ?-diversity of Fagus lucida community,while they exhibited similar effects on those of the other communities.Specifically,the species ?-diversity of Fagus lucida community was determined by elevation and soil organic matter(OM),that of Carpinus fargesiana community by elevation and soil p H,that of Pinus massoniana community by elevation and soil AK,and that of Cunninghamia lanceolata community by soil TP.(4)Difference in the phylogenetic compositions of the four communities was significant: the strongest difference was found between Fagus lucida community and Cunninghamia lanceolata community.Carpinus fargesiana community had higher phylogenetic ?-diversity than the others.Within Carpinus fargesiana community,phylogenetic structure changed from convergence to divergence with increasing soil TP and p H and decreasing elevation.Within Fagus lucida community,phylogenetic structure became more divergent while phylogenetic ?-diversity decreased as elevation and steepness elevated.Within Cunninghamia lanceolata community,phylogenetic ?-diversity increased with increasing elevation,while phylogenetic structure changed from convergence to divergence with decreasing elevation and increasing soil TP.Within Pinus massoniana community,phylogenetic structure changed from convergence to divergence with increasing soil TP,AP and p H and decreasing elevation.Phylogenetic ?-diversity did not significantly differ among communities,while,in each community,elevation is the environment factors with significant effects on that.(5)Difference in the functional traits of the four communities was significant.Specifically,Pinus massoniana community and Cunninghamia lanceolata community were similar in trait weighted-mean values,but their wood density(WD),specific leaf area(SLA)and leaf nitrogen content(LNC)were significant lower than the others but leaf phosphorus content(LPC)was significant higher.Fagus lucida community had significant higher leaf dry mass content(LDMC)but lower LPC than Carpinus fargesiana community.Functional ?-diversity was significantly different among communities,but functional ?-diversity was not.Carpinus fargesiana community had significant higher functional richness than the other communities,while Fagus lucida community had significant lower functional divergence than the other communities.Compared with the simulated values from null model,the most pronounced feature of trait variability for Carpinus fargesiana community is the low community-weighed variance(CWV)of LPC,that for Fagus lucida community is the low CWV of LPC and LNC,while that for either Pinus massoniana community or Cunninghamia lanceolata community is the high CWV of SLA.Environmental factors had pronounced but complex effects on the functional features of the four communities,and such effects acted on several aspects;in general,steepness,reflected by slope,was the factor with broad influences on the functional features of Carpinus fargesiana community and Fagus lucida community,while elevation and soil TP were the factors with broad influences on those of Pinus massoniana community and Cunninghamia lanceolata community.Our results show that the four communities are different in community structure,species compositions,functional traits,and phylogenetic relationships.Carpinus fargesiana community shows higher ?-diversity than the other communities in our study area.The diversity maintenance of all the communities are driven by both niche-based and neutral processes.Neutral processes may be more important than niche-based processes in Fagus lucida community,while their importance in the other communities is similar.All the communities have their diversity patterns determined by elevation.In addition,those of Fagus lucida community and Carpinus fargesiana community are also widely influenced by slope and soil p H,while those of Pinus massoniana community and Cunninghamia lanceolata community are also widely influenced by soil nutrients.