乌鲁木齐山地草地生态系统服务价值变化评估——基于遥感与GIS

草地生态系统服务功能是指草地生态系统及其生态过程所形成和维持的人类赖以生存的自然环境及其有效性,中国干旱半干旱地区的草地退化严重制约着生态系统服务功能的。以乌鲁木齐市山地草地为研究靶区,利用遥感图像(Landsat TM/OLI)划分出7种不同草地类型并计算其生态系统服务价值(Ecosystem Service Values, ESV)。使用空间统计方法、网格分析、空间自相关等方法进一步分析研究区山地草地退化程度和ESV变化。结果表明:21年中,乌鲁木齐市草地生态系统服务价值呈现波动性下降趋势,年均减少0.27×10~7元。生态损失主要是由山地荒漠草地(7.44%)、山地荒漠草原草地(10.71%)、山地草甸草原草地(18.32%)和高寒草甸草地(40.69%)退化造成。单项生态系统服务价值中,草地对调节服务(土壤形成)和供给服务的贡献率较高。草地ESVs Moran平均值为0.869(1994—2015年),并且草地ESV与相邻网格(2 km×2 km)具有更高的空间相关性。草地ESV具有明显的空间分布特征,高ESV区基本上分布在南山山区,低ESV区主要分布在平原草地区,博格达山草地亚区呈现随机分布格局。研究区气候变化对草地的影响十分显著,平均气温、平均地表温度、湿度、蒸散量、降水量和风速对草地ESV变化均有一定的影响,过度放牧、不合理垦荒、药用植物过度开发、城市化等人为活动仍然是驱动草地退化的主要因子,因此亟需采取措施保育乌鲁木齐市山地草原生态系统。

Spatio-temporal changes of grassland ecosystem service values in Urumqi City based on the RS and GIS

Grassland deterioration is an urgent problem in China. Changes in seven grassland types and their ecosystem service values (ESVs) in Urumqi City were calculated based on the classification results. A classification and grading system for grassland was designed based on fieldwork and an expert review. In addition, grid cell and spatial autocorrelation analyses were used to explain the degree of mountain grassland degradation and ESV changes in the study area. We interpreted Landsat TM/OLI images of the study area in 1994, 2000, 2005, 2010, and 2015. The results showed that the degraded grasslands reached a maximum area of 1.22×10⁵ hm² in 2000. However, the rate of grassland degradation decreased from 2000 to 2015 with the decreased 387 hm² each year. The total ESVs of the grasslands demonstrated volatile decreasing trends with an annual reduction of 0.27×10⁷ yuan. The ecological losses were mainly caused by the degradation of mountain desert grassland, mountain desert steppe type rangeland, mountain meadow type rangeland, and alpine meadow steppe type rangeland. Among the individual ESVs, grasslands made higher contributions to the regulating (soil formation) and supporting (pollination) services, while the provisioning and cultural services of the grasslands were relatively low and accounted for only 0.69% and 0.55% of the total ESV. The mean Moran''s I value was 0.869 for the grassland ESVs from 1994 to 2015. The grassland ESVs exhibited high spatial autocorrelation with adjacent grid cells (2 km×2 km). The grassland ESVs had clear spatial distributions characteristics. The regions with high ESVs were basically distributed in the Nanshan mountainous area. The low ESV regions were mainly located in the plain grassland region. The Bogda mountainous regions presented random distribution patterns. The results showed that a region-wide grazing ban and the control of rodent and locust hazards combined with other ecological engineering measures were promising for reversing the degradation and promoting the recovery of grassland vegetation. Thus, the urgent actions are required to maintain or promote the ecosystem services of mountain grassland in the arid and semiarid regions of Urumqi City, Northwest China.