Comparative Study On The Forest Community Niche Of The Gansu Xiaolongshan Expressway Area And The Forest Area

The Gansu Xiaolongshan forest area is the important natural forest in China,it is also one of the most intact natural forests in Gansu Province and the ecological value is inestimable.The main part of the Baoji-Tianshui Expressway is located in the Tianshui Beidao District,the southeast of Gan Su,with most of engineering construction through the Xiaolongshan forest area.The expressway project go through Dangchuan,Maiji,Dongcha,Baihua,the four tree farms.With the opening of the expressway,the local traffic has largely improved.However,it also brings some negative ecological effects on the growth and distribution of the forest population in the area.For that reason,we set up quadrats for community survey in the road area and Xiaolongshan forest area.Also,the composition of forest communities were analysed.We applied the Levins model and Shannon-Wiener index to measure the niche breadth and niche overlap and niche proportional similarity of Pinus armandi community,Quercus acutidentata community and Pinus tabulaeformis community in the BaojiTianshui Expressway area and the Xiaolongshan forest area.Then contrasted the comparative study between the road area and Xiaolongshan forest area.The results show that:(1)In general,the niche breadth value of the edificators is the biggest in the community.Except for the edificators,the arrangement order of niche breadth of other populations have been changed.Except for the Platycladus orientalis community,the niche breadth of each community in the range of disturbance shows an increasing trend than that in the Xiao Longshan forest area.In the road area,in addition to the niche breadth of population of Carpinus turczaninowii and Quercus acutidentata in Pinus armandi community,Toxicodendron vernicifluum in Pinus tabulaeformis community are less than the Xiaolongshan forest area,others are larger than the Xiaolongshan forest area.The niche breadth of Pinus armandi in Pinus armandi community has largest increased by 1.2%,Dendrobenthamia japonica in Quercus acutidentata community has largest increased by 26.8%,Quercus acutidentata in Pinus tabulaeformis community has largest increased by 35.5%,Artemisia gmelinii in Platycladus orientalis community has largest decreased by 38.6%.(2)The greater the niche overlap value is,the closer the biological characteristics are,the use of environmental resources is more similar and the competition between them is more intense.Because of disturbance,except for the Platycladus orientalis community,the niche overlap degree of populations in the community is larger than that in the Xiaolongshan forest areas.The population niche overlap value of Pinus armandi community,Quercus acutidentata community and Pinus tabulaeformis community in the Baoji-Tianshui Expressway area and the Xiaolongshan forest area are larger than 0.2,accounted for 85.7% and 66.1%,73.8% and 66.7%,63.3% and 56.7% of the total respectively,and the population niche overlap value of Platycladus orientalis community are larger than 0.2,accounted for 92.9% and 96.4%.(3)By comparing and calculating the niche proportional similarity of the community in the road area and the Xiaolongshan forest area,the result shows that the niche similarity of each community is larger than that of the Xiaolongshan forest area,except for the Platycladus orientalis community.The proportion of niche similarity of each community in road area is larger than that in the Xiaolongshan forest area.The niche similarity for each community of Pinus armandi,Quercus acutidentata,Pinus tabulaeformis and Platycladus orientalis community are larger than 0.5,accounted for 89.3% and 67.9%?81% and 71.4%?80% and 53.3%,64.3% and 100% respectively.