| Fagaceae Quercus is the most widely distributed group of forest tree species,with a large range of ecological adaptation.Many species are dominant species or constructive species in the community,with high adaptability to the environment and self-regulation ability in complex environment.Litter is the key link connecting the underground and aboveground ecological processes of forest ecosystem,and its stock and stoichiometry can also reflect the stability of the community.Taking the Quercus natural secondary forest in Anhui Tianma National Nature Reserve in Dabie Mountain Area as the research object,this paper set sample plots every 100 m in the range of 200 ～ 1200 m from July to October 2021,carried out species diversity investigation and litter collection of Quercus natural secondary forest,and analyzed the effects of sea elevation and slope direction on species composition,flora,community structure,plant diversity To reveal the spatial heterogeneity of different communities and their litter stoichiometry,so as to provide a scientific basis for the management and management of Quercus natural secondary forest.The main results are as follows:(1)A total of 292 species of plants were investigated in the sample plot,belonging to79 families and 202 genera,including 2 species of gymnosperms in 2 families and 2genera,269 species of dicotyledons in 66 families and 181 genera,and 16 species of monocotyledons in 6 families and 13 genera,with the largest number of species of Compositae in the community.(2)In terms of floristic elements,the most widely distributed elements in the world(accounting for 37.9%),followed by the pan tropical distribution(accounting for24.1%);The north temperate component is the most(accounting for 18.3%),followed by the pan tropical component(accounting for 15.3%).(3)The Shannon Wiener diversity index of shrub layer under oak natural secondary forest in Tianma Nature Reserve is less than that of herb layer;Simpson dominance index of herbaceous layer changed little;The evenness index of herb layer is slightly higher than that of Pielou shrub layer.(4)With the increase of altitude,the species richness index of shrub layer showed a downward trend;The Shannon Wiener diversity index of shrub layer and herb layer showed a "single peak" trend,the Simpson dominance index and the Pielou evenness index changed irregularly.In the slope direction,the species richness and Pielou evenness index of shrub layer and herb layer were higher on the sunny slope than on the shady slope;In terms of Shannon Wiener diversity index and Simpson dominance index,the sunny slope is greater than the shady slope.(5)The nutrient content of litter in different altitude gradients varies greatly.The nutrient content of non decomposed layer(OL layer)is greater than that of decomposed layer(OH layer).(6)The litter content in different slope directions showed as follows in each decomposition layer of litter on the shady slope: the SOC content showed OL > Oh layer;TN content showed OL< Oh layer;TP content showed OL < Oh;In the sunny slope,the decomposition layers of litter showed that the content of SOC showed OL>Oh layer;TN content showed OL< Oh layer;TP content showed OL< Oh layer.(7)The litter C: N,C: P and N: P values of Quercus natural secondary forests at different altitudes and slope directions were significantly lower than the global average level.(8)The correlation between species diversity index and litter of understory vegetation shrub layer is mainly reflected in the relationship between species richness and Simpson dominance index,Shannon Wiener diversity index and TP content;The correlation between species diversity index of understory vegetation and litter is mainly reflected in the relationship between species richness and Simpson dominance index,Shannon Wiener diversity index,SOC content and TN content. |
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