The Dynamics Of Ecosystem Services And Their Driving Factors In The Jing-Jin-Ji Region

Ecosystem services and the impacts of land use/cover changes on ecosystem services have become a global research hotspot.Beijing,Tianjin and Hebei,the so called Jing-Jin-Ji region in China are facing serious ecological degradation such as water scarcity,water contamination,soil erosion and air pollution,which has restricted regional development.The Jing-Jin-Ji coordinated development strategy aims to break the administrative boundaries,establish a regional social-ecological complex system,and achieve the mutual sustainability of ecosystem and economy.Under such background,this study anlalyzes the land use/cover pattern,spatial distribution and transfer matrix from 1990 to 2015,and explores the corresponding characteristics of ecosystem services by using the Integrated Valuation of Ecosystem Services and Tradeoffs?InVEST?model.The study explores the spatiotemporal changes of ecosystem services on the watershed and administrative patterns and elaborates their driving factors from natural and social perspectives by using correlation and statistic methods.The study also analyzes the dynamics between ecosystem and economy,and figure out ways towards ecological-economic integrity in Jing-Jing-Ji.The main research results are as follows.?1?The land use/covers in Jing-Jin-Ji contains cultivated land,forest,grassland,wetland and built-up land,and their spatial distributions kept stable.From 1990 to 2015,the area of cultivated land,grassland and wetland decrease by 17,033 km2,668 km2 and 1037 km2 respectively,while the area of forest and built-up land increase by 13,495 km2 and 5533 km2 respectively.The transfer matrix of land use/covers between 1990 and 2015 shows,136;89km2 of cultivated land is converted to forest land,and 4487km2 is converted into built-up land;of wetland,1005km2 is converted into cultivated land,and 642km2 is converted into built-up land;of the grassland,298km2 is converted into cultivated land,and 281km2 is converted to built-up land.Such trend is mainly due to the effects of forest conservation measures and increased urbanization brought by social-economic development.?2?The temporal and spatial evolution of ecosystem services in Jing-Jin-Ji presents different patterns.The total water yield is different year to year,the highest water yield is occurred in 2010 and the lowest is in 2000.The spatial distribution of water yield shows a low-high belt distribution pattern from northwest to southeast,and the average water yield depth in the high water yield areas is 100-200mm,and the water depth in the low water yield area is less than 100mm.The spatial difference between 1990 and 2015 is that the water yield depth of central areas of the region is increased by about 50mm while the other parts is decreased byaverage 70mm.There is little variation in annual nutrient output,but the spatial distribution pattern is different.The high value is concentrated in the plain area in the southeast,and the low value is concentrated in the north and northwest.The average nutrient output of high value area is about 10 times of that in the low value area.The spatial and temporal differences between 2015 and 1990 are as follows:the nutrient output of more than half of the area is reduced,of which the average reduction of nitrogen?n?is 0.5-1 kg/ha,and the average reduction of phosphorus?p?is 0.1-0.2 kg/ha.There annual variation of soil retention is small,but the spatial distribution shows the characteristics of low-high-low belt pattern from the northwest to the southeast;the highest value is distributed in the belt-shaped mountainous area from north to southwest,and the low value is mainly distributed in the southeast.The annual average soil retention in high-value areas is about 30 times higher than that in low-value areas.The spatial difference between 2015 and 1990 shows that water retention is reduced by 100-300t/ha in two-thirds of the area,located at the central part that crosses east-west to south-west.The annual variation of carbon sequestration is small,and the spatial distribution is irregular.The average carbon storage in high value areas is about 1.2 times that of low value areas.The difference between 2015 and 1990 is that the total carbon storage decreases year by year,and the spatial distribution of carbon storage decreases by 0-10t/ha in most areas.Only for some small scattered areas,the carbon storage is increased.Based on the spatial distribution pattern of each of ecosystem services,the water conservation function Zone is identified in the northwest,including the northwestern part of the Luanhe river basin,the western part of the Beisan mountain River basin,the western Inner Mongolia Plateau river basin,the Yongding river basin,and the Daqing Rive basin.The water purification function zone is located in the northern part of the region,consisting of Beisanhe mountain area and the basin area to the north,the Daqinghe mountain river basins,Daqing river basin and the river basins alongside the Bohai bay.The soil retention function zone is located in mountain parts of Luanhe river basin and Beisan river basin,the Yongding river basin and the south and north of the Daqing mountain river basin.The carbon storage function zone is mainly distributed at the river basins of northern Beijing,the river basins in western mountain areas and eastern Bohai bay.?3?There is trade-off between water yield and other three ecosystem services of nutrient export,carbon storage and soil retention.The relationship between nutrient export and soil retention also shows the negative tradeoffs.There is coordinated relationship between carbon storage and soil retention.The dynamics of each of the four ecosystem services are driven by complex of natural and social factors.Under the only the effect of land use/covers,there are obvious differences among ecosystem service coefficiets of each land use/cover type.The water yield coefficient of built up land is highest?0.52±0.06?,followed by vegetation land of cultivated land?0.16±0.04?,forest?0.21±0.03?and grassland?0.18±0.04?;the water yield of wetaland is aprroching to 0.The nutrient export coefficient?kg/ha?of cultivated land is highest,?n=1.48±0.02,p=0.4±0.005?,followed by built-up land?n=1.19±0.05,p=0.34±0.008?,wetland?n=0.61±0.05,p=0.15±0.01?,grassland?n=0.58±0.003,p=0.11?and forest?n=0.3±0.001,p=0.05?.The soilretent coefficient?t/ha?of forest is highest(907±18.79,followed by grassland?563±2.85?,cultivated land?99±0.7?and wetland?7±9.98?.The carbon storage coefficient?t/ha?of wetland is highest?217±0.3.15?,followed by forest?125±0.55?,cultivated land?93± 1.15?and grassland?91±1.12?₄From 1990 to 2015,the elasticity indicator?EI?of Jing-Jin-Ji is improved from 0.028 to 0.293,indicating the development of ecological and economic development tend to be synchronized.The regional average economic ecological load?ESL?is reduced by 1.24,showing the ecological pressure on undertaking the economic development is decreased.There are large disparities in El and ESL for Beijing,Tianjin and Hebei due to different ecological resources,GDP compositions and development levels.The results show that from 1990 to 2015,the forest in Jing-Jin-Ji is in continuous increase as a result of forest protection policies and measures;the population growth and economic development lead to an increase in built-up areas,and a decline in cultivated land,grassland and wetland.Influenced by natural and social factors,the quantity and spatial pattern of each of the ecosystem services present different characteristics and changing patterns.There is imbalance between ecological and economic development,and the ecosystem undertakes high pressure on sustaining the economic growth.Therefore,in the process of Jing-Jin-Ji coordinated development,it is urgent to form rational land use/cover pattern,strengthen the ecological conservation and release the ecological burden to achieve the integrity of ecological and economic development.