Species Diversity of the Tree Layer with Changes in Altitudes in Rhinopithecus roxellana Habitats at Shennongjia,China

Tree species diversity and community structure along the altitudinal gradient were analyzed through quadrat investigation at Rhinopithecus roxellana habitat of Shennongjia Nature Reserve.Major results include:(1) 289 woody species from 23 genera and 37 families were recorded in the 160 sampled plots,including 198 tree species from 90 genera and 25 families,84 shrub species from 29 genera and 7 families and 7 liana species from 4 genera and 5 families.Rosaceae,Caprifoliaceae,Lauraceae,Fagaceae,and Ericaceae were the dominant families.(2) Based on the difference in tree species composition at different altitudes,vegetation of the study area was divided into Deciduous Broad-leaved Forest(1900-2100 m),Coniferous and Broad-leaved Mixed Forest(2200-2400 m),and Dark Coniferous Forest(2500-2600 m).(3) The Shannon-Wiener index of the tree layers decreased with increasing elevation;the Pielou’s index decreased with increasing elevation in the Coniferous and Broad-leaved Mixed Forest and the Dark Coniferous Forest,whereas showed no significant change in the Defoliate Broad-leaved Forest.(4) The proportion of the first tree layer(>20 m) decreased as elevation rose,the proportion of the second tree layer(10-20 m) showed no distinct change and the proportion of the third tree layer(<10 m) increased.(5) As height of trees indicates age,the population age structure of nine dominant tree species showed that the tree layer had a steadily increasing trend in the study area.