Spatio-temporal variation of karst ecosystem service value and its correlation with ambient environmental factor

For the restoration and reconstruction of karst ecosystems, it is vital to explore the spatio-temporal variations in ecosystem service value of karst regions in Southwest China and its correlation with ambient environmental factors. Based on multi-temporal satellite imagery, weather and statistical data, spatial distributions and dynamics of karst ecosystem service value were evaluated for Northwest Guangxi. The links between karst ecosystem service value and ambient environmental conditions were also analyzed for 1985~2005 using Canonical Correspondence Analysis (CCA). The results show an initial decline in karst ecosystem service value, followed by a steady increase at 109.652, 103.384 and 106.257 billion Yuan in 1985, 2000 and 2005 respectively. Ecosystem service values for nutrient cycling, organic matter production, gas regulation and soil formation are high, with respective total contribution ratio of 72.69%, 70.18% and 72.10% in 1985, 2000 and 2005. However, ecosystem service values for water and soil conservation, recreation and culture are much low and well below 10 billion Yuan. Woodlands and shrubs are the main contributors to ecosystem service value with total contribution ratio of 71.22%, 73.66% and 67.03% in 1985, 2000 and 2005 respectively. While residential and rocky land contribute less to the ecosystem service, their contribution ratio sum are 0.62%, 0.52% and 0.76%, respectively. CCA ordination diagram shows that ecosystem service values are closely linked with ambient environmental factors. Slope gradient, elevation have a significant impact on ecosystem service value. There also exist significant spatio-temporal differences among these factors. Ecosystem service value of the studied area shows a declining trend from West to East. Ecosystem service value for typical karst regions is obviously increasing, while that for non-karst regions markedly decreasing. Based on the study, ecological conditions are improving due to better policies such as ecological migration and afforestation of farmlands to control rock desertification.