Comprehensive Assessment of Soil Conservation Capacity of Forest Ecosystems in Beijing

In this paper,five factors such as vegetation cover ratio,the depth of forest floor,forest type,crown density and community structure were employed to comprehensively evaluate Beijing's forest ecosystems effects on soil conservation.The results showed that 65.7% of forests in Beijing had the soil conservation ability at the middle and higher level,16.8% at low level.The capacity of soil conservation in Beijing's forests varied greatly in different districts(or counties),and was ranked in the descending order as follows:Shijingshan District,Yanqing County,Miyun County,Mentougou District,Fangshan District,Haidian Distrcit,Pinggu District,Changping District,Fengtai District,Huairou District,Chaoyang District,Shunyi District,Tongzhou District and Daxing District.The capacity of soil conservation in Beijing's forests had a positive relationship with altitude,and was ranked from low to high as plain area(less than 100 m),hilly area(between 100 and 500 m),low mountain(between 500 and 800 m)and middle mountain(more than 800 m).With the increasing slope,the soil conservation ability of forests increased slightly,however,when slope more than 25 degree,there was little differences of soil conservation capacity.The capacity of soil conservation also varied with forest soil type,those forests with mountain meadow soil,mountain brown earth and cinnamon soil had the higher level,and paddy soil,alluvial soil,aeolian soil and meadow-boggy soil had lower level.