Abstract
Land use profoundly changes the terrestrial ecosystem and landscape patterns, and these changes reveal the extent and scope of the ecological influence of land use on the terrestrial ecosystem. The study area selected for this research was the middle reaches of the Heihe River. Based on land use data (1986, 2000, and 2014), we proposed an ecological risk index of land use by combining a landscape disturbance index with a landscape fragility index. An exponential model was selected to perform kriging interpolation, as well as spatial autocorrelations and semivariance analyses which could reveal the spatial aggregation patterns. The results indicated that the ecological risk of the middle reaches of the Heihe River was generally high, and higher in the northwest. The high values of the ecological risk index (ERI) tended to decrease, and the low ERI values tended to increase. Positive spatial autocorrelations and a prominent scale-dependence were observed among the ERI values. The main hot areas with High-High local autocorrelations were located in the north, and the cold areas with low-low local autocorrelations were primarily located in the middle corridor plain and Qilian Mountains. From 1986 to 2014, low and relatively low ecological risk areas decreased while relatively high risk areas expanded. A middle level of ecological risk was observed in Ganzhou and Minle counties. Shandan County presented a serious polarization, with high ecological risk areas observed in the north and low ecological risk areas observed in the southern Shandan horse farm. In order to lower the eco-risk and achieve the sustainability of land use, these results suggest policies to strictly control the oasis expansion and the occupation of farmland for urbanization. Some inefficient farmland should transform into grassland in appropriate cases.
Highlights
Human activities are currently causing profound changes to the terrestrial ecosystem, primarily through land use [1]
This research analyzed the characteristics of the dynamic spatial-temporal changes of ecological risk based on land use data, GIS technical support, spatial autocorrelation analyses, and semivariance analyses
The main conclusions are as follows: (1) the ecological risk of the middle reaches of the Heihe River was generally high, whereas the high ecological risk index (ERI) values tended to decrease and the low ERI values tended to increase; (2) positive spatial autocorrelations were observed among the ERIs, prominent scale-dependence was observed for the ERI spatial distribution, and the spatial autocorrelations tended to decrease with increases of grain
Summary
Human activities are currently causing profound changes to the terrestrial ecosystem, primarily through land use [1]. In landscapes dominated by human activities, the land use reflects the manner and extent of human influence on the natural ecosystem. With regional and cumulative characteristics, the influence of land use on ecosystems can directly reflect changes of ecosystem structure and components [7]. Ecological risk analysis based on land use and landscape structure can integrate evaluations of different potential ecological influences and their cumulative characteristics. With the development of studies on ecological risk management, the ecological risk caused by land use has become a focus of research because it is an important human disturbance risk [8,9,10,11]
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