Desert Ecosystem Service And Its Responses To The Change Of Land Cover

Ecosystem services means the benefits people get from the nature through direct or indirect manners.Due to its lower biological production, the desert ecosystem services in arid area is often tend to be ignored. The desert ecological problems are getting more attention and ecological restoration projects are implemented in recent years. How large scale of services can desert ecosystem provide to human? What’s the relationship between ecosystem services and the change of land cover caused by human activities? This paper focus on Shapotou national nature reserve in Zhongwei, Ningxia located in the southeast edge of Tengger desert, based on the framework of Millennium Ecosystem Assessment, the ecosystem services was evaluated from the following five aspects:food providing, wind prevention and stabilization, soil conservation, carbon fixation and oxygen release and nutrient cycling. Combining previous relevant ecosystem services evaluation models, this paper evaluated the quantity of each ecosystem service in 2002,2006 and 2011. Meanwhile, considering the prices fluctuating with time, this paper revised the prices using CPI, then evaluated the economic value of each ecosystem services and analysis their spatial distribution and changes over time. In order to clear the relationship between ecosystem services and land cover changes, we use the identical meteorological elements (meteorological data of 2002) to reevaluate each ecosystem services in 2002.2006 and 2011. The results show that:(1) Quantity evaluation of ecosystem services:lower ecosystem services value present continuously,higher value areas present scattered, and different land cover types usually possess different ecosystem services value. Ecosystem services change largely from 2002 to 2011.From 2002 to 2006, per unit area of ecosystem service undergo a decrease since the climate change and vegetation degradation. From 2006 to 2011, vegetation got restoration, so most of the ecosystem services increased except the wind prevention and stabilization.(2) The economic value of ecosystem services:the economic value of ecosystem services in study area is 85.5102 million yuan in 2002,82.146 million yuan in 2006 and 155.53 million yuan in 2011. The indirect value is much higher than direct value and it is about 13 to 30 times as much as the value of direct. The sequence of all service values go as wind prevention and stabilization> soil conservation> carbon fixation and oxygen release> food providing> nutrient cycling. The total economic value sequences of land cover types is:timber forest> farmland> scrub>protection forests>grassland>water area.(3) Land cover changes:land cover changes largely from 2002 to 2011, which features the expansion of timber forests and farm land and the reduction of grassland and sand. Land cover changes from 2002 to 2006 mainly was grassland convert to water and timber forest, sand convert to farmland and timber forests. Land cover changes from 2006 to 2011 was mainly was sand convert to timber forests and farmland, farmland convert to timber forests, grassland convert to timber forest, water area convert to timber forests.(4) The relationship between ecosystem services and land cover changes:through the nearly 10 years of desertification prevention and control in the study area by converting land cover types such as from the sand to timber forests, the NPP, wind prevention and stabilization and soil conservation has increased dramatically.