Species Diversity Variation And Environmental Interpretation Of Cupressus Funebris Secondary Forest In Landslide Site After 5.12 Wenchuan Earthquake

This article selects the typical landslide surface of Fenghuang Mountain,Leigu Town,Beichuan County,which was derived from the 5.12 Wenchuan earthquake.To explore characteristics of species diversity in Cupressus funebris secondary forest under the effect of geological hazard.Detrended Canonical Correspondence Analysis(DCCA)was used to analyze the relationships between the distribution of herb layer and 20 environmental factors.The results showed that 93 species belonged to 42 families and 78 genera were found in landslide area whose families were mainly Compositae,Leguminosae,Gramineae.based.97 species in transition area belonged to 39 families and 80 genera,and main families were Compositae,Gramineae,Rosaceae-based.108 species were recorded in non-landslide area which belonged to 59 families and 92 genera,whose families were mainly Compositae,Rosaceae and Gramineae-based.Compositae and Gramineae played important roles in the landslide recovery process after earthquake.The Pielou index(Jsw)0.671 and Simpson index(H')0.794 were the highest in non-landslide area of the herb layer,while the richness index(DS)29 was the lowest,while the Shannon-Wiener index(H)0.982 was in the middle.In the non-landslide area,the DS(30)and H(1.084)were the highest in the shrub layer,while the H'(0.825)and Jsw(0.735)was the lowest.Meanwhile,the species diversity index of the transitional area was higher than that of the landslide area.In the tree layer,the DS and H were both the highest and the lowest in the landslide area and the transition area,respectively.Whereas,the H' and Jsw were both the highest in the transition area and the lowest in the non-landslide area.The results of Detrended Canonical Correspondence Analysis showed that The collected environmental factors accounted for 56.2% of the plant communities,the unexplained portion for 43.8%.Results of DCCA ordination showed that density of tree and shrub layer,soil fertility and texture was dominant among the 20 environmental factors that affected community distribution.The first DCCA axis(66%)accounted for the largest fraction of the variation and showed gradients of density of tree and shrub layer,total potassium and gravel contentration.Along the first ordinal axis from left to right reveals a comprehensive gradient with increased stand density,soil texture and fertility.The second DCCA axis(22.7%)showed variation due to slope,elevation and average diameter.From the bottom of the second sorting axis reveals a steep gradient,high altitude,and a gradient of increased stability of aggregates.The distribution of species is affected by multiple environmental factors,among which landslides and transitional areas have more obvious responses to environmental factors than landslides,and tend to change more with environmental gradients.