Spatio-temporal Changes Of Main Ecosystem Services In Forestry Ecological Project Region Of The Yangtze River Economic Belt

The Yangtze River Economic Belt（YREB）spans the three major regions of China’s east,middle and west,involving 11 provinces and municipalities.It has unique advantages and huge development potential,and is an important ecological security barrier area in China.The long-term unreasonable farming methods in the last century have caused extensive damage to forests,the quality of forests has declined,soil erosion has been serious,and the ecological environment has deteriorated continuously.Since the 1980s,China has carried out a series of major forestry ecological projects such as the Yangtze River Shelter Forest Project,the Natural Forest Protection Project in the Upper and Middle Reaches of the Yangtze River,and the“Grain to Green”to promote the greening and ecological restoration of the Yangtze River Basin.In the past 40 years,these forestry ecological projects have made significant contributions to the ecological environment of China and the world.Nowadays the scope of the forestry ecological engineering construction system is getting larger,but the land for afforestation is gradually decreasing,and the construction cost of the project is increasing.It is necessary to explore the role of forestry ecological engineering on ecosystem services at this stage.Based on forest resource inventory data,remote sensing image data,meteorological data,soil data,traffic data and historical literatures,this paper adopts Biomass-Volume models,the universal soil loss equation（RUSLE）,and the In VEST model to evaluate ecosystem services:carbon storage of forests biomass,soil conservation services,and provision of habitat quality in the YREB.The GIS spatial analysis method was used to set up a single driving force scenario for forestry projects,to analyze the changes in the forests area based on the forest resource inventory data and the changes in the Woodlands area based on the remote sensing image data,and to explore the impact of forests/Woodlands changes on the three ecosystem services in YREB.The main conclusions are as follows:（1）The change trend of forests/woodlands area in the YREB based on two different data sources is different.The forests area based on forest resource inventory data in 2000,2005,2010and 2015 were 66.80×10⁶hm²、78.42×10⁶hm²、84.32×10⁶hm² and 89.78×10⁶hm²respectively,which continued to increase significantly.The woodlands area based on remote sensing images in 2000,2005,2010,and 2015 were 89.05×10⁶hm²,89.96×10⁶hm²,89.77×10⁶hm²,and 89.60×10⁶hm²,respectively,showing a small change range and a trend of increasing first and then decreasing.（2）The total forest biomass carbon storage in the YREB in 2000,2005,2010 and 2015 were1990.41 Tg C,2347.05 Tg C,2584.52 Tg C and 3005.86 Tg C,respectively,showing a continuous increasing trend.From 2000 to 2015,the forest biomass carbon storage increased by 51.02%,and the average annual carbon sequestration was 67.70Tg C·a^-1.Yunnan and Sichuan are the provinces with the largest forest biomass carbon storage and carbon sequestration,accounting for 55.90%and 44.49%of the total forest biomass carbon storage and carbon sequestration in the YREB,respectively.The non-engineered area and the area where only the Yangtze River protection forest project has taken place have strong biomass carbon sequestration in new forests.The area where only the natural forest protection project has taken place and the forest management part in the overlapping area of the two projects have higher biomass carbon sequestration.（3）The soil erosion capacity and soil retention capacity are both high in the west and low in the east of the YREB.In 2015,the sum of soil erosion and soil conservation in Sichuan Province and Yunnan Province accounted for 67.28%and 61.86%of the entire YREB,respectively.From 2000 to 2015,the amount of soil erosion and soil retention in the YREB declined first and then rised.Woodlands is the land type with strongest soil retention capacity,and it also contributes more than 60%of the total amount of soil retention in the YREB in 2000,2005,2010 and 2015.The increase of the woodland area in the forestry project area has played a positive role in the improvement of the soil retention capacity of the YREB,but the impact is relatively small compared with other influencing factors,and it is not the main cause of the current changes of the soil retention capacity in the YREB.（4）The habitat quality（HQ）of the YREB presents a spatial distribution characteristic of low in the east and high in the west.The areas with low HQ index are mainly distributed in the northern Yangtze River Delta,the Jianghan Plain and the Sichuan Basin,while the average HQ index of Yunnan,Jiangxi and Zhejiang is higher.Woodlands are with higher HQ index,while built-up land,farmland and bare land are the areas with lower HQ index.From 2000 to 2015,the HQ of the YREB is developing towards polarization.Areas with medium-level HQ gradually shift to lower and higher levels,and the average HQ index of the YREB has not changed significantly.Forestry ecological projects have a certain effect on the improvement of HQ,which is specifically manifested in further improving the HQ of areas with medium and higher HQ index,but has weak effect on areas with lower HQ index.In the future,the construction of urban forestry should be strengthened to avoid further expansion of the polarization of habitat quality.