伊犁河流域1990—2020年耕地转入-转出评价

Assessment of cultivated land transfer in and transfer out in the Ili River Basin from 1990 to 2020

  • 摘要: 以往在评估转入、转出耕地的质量变化时很少将耕地土壤理化性质考虑进来。伊犁河流域是新疆重要的农牧业基地, 过去30年来, 伊犁河流域自然环境和社会经济发生了巨大变化。本研究利用30 m分辨率的中国多时期土地覆盖数据集获取伊犁河流域1990和2020年耕地空间分布数据, 探究耕地的数量变化以及转入耕地的来源和分布情况; 基于DEM数据集、中国高分辨率国家土壤信息网格基本属性数据集等, 通过计算Cohen’s D值比较新增耕地和转出耕地在海拔、坡度、土壤有机碳含量、全磷含量、全氮含量、砂粒含量和pH上的差异, 并与全国七大农区进行对比。与1990年相比, 2020年伊犁河流域耕地面积由6 196.80 km2增加至8 606.51 km2, 新增的耕地主要是高海拔的草地, 且集中在河流的两岸, 这与流域的灌溉调水能力有所提升有关; 1990—2020年新增耕地与转出耕地相比海拔有较大程度增加, 但坡度仅有较小程度增加(Cohen’s D值分别为0.851、0.276); 有机碳含量、全氮含量分别有中等和较小程度的增加, 且全磷含量、砂粒含量和pH的变化很小(Cohen’s D值分别为0.558、0.308、−0.116、0.081、0.001), 即伊犁河流域新增耕地的土壤质量较好, 这与新疆和全国七大农区明显不同。伊犁仍有大量可开垦草地作为后备耕地, 但为保障农牧业平衡发展和降低生态风险, 未来应该限制草地的过度开垦, 尤其是生态脆弱的高海拔(如海拔2 000 m以上)和陡坡地带的开垦活动应受到特别关注。

     

    Abstract: In previous assessments of the quality changes associated with the transfer in and out of cultivated land, soil physical and chemical properties have rarely been considered. The Ili River Basin is an important agricultural and husbandry base in Xinjiang, which has undergone significant changes in its natural environment and socio-economic conditions over the past 30 years. This study used a 30-meter resolution dataset of China’s multi-year land cover to obtain the spatial distribution data of cultivated land in the Ili River Basin for the year of 1990 and 2020, exploring the changes in the quantity of cultivated land as well as the source and distribution of transferred-in cultivated land. Based on the DEM data and basic attribute dataset of China high resolution national soil information grid, we calculated the Cohen’s D values to compare the differences in elevation, slope, organic carbon content, total phosphorus content, total nitrogen content, sand content, and pH between transferred-in and transferred-out cultivated land, and compared these with the those from the seven major agricultural regions of China. Compared with 1990, the area of cultivated land in the Ili River Basin increased from 6,196.80 km2 to 8,606.51 km2 by 2020. The transferred-in cultivated land was mainly high-elevation grassland concentrated along the bank of the rivers, which is mainly related to improved irrigation and water diversion capacities in the Basin. From 1990 to 2020, transferred-in cultivated land increased greatly in elevation compared to transferred-out cultivated land, while the slope only showed a slight increase (Cohen’s D values of 0.851 and 0.276, respectively). Organic carbon content, total nitrogen content increased moderately and slightly, respectively, while the changes in total phosphorus content, sand content, and pH were very small (Cohen’s D values of 0.558, 0.308, −0.116, 0.081, and 0.001, respectively). This indicates that the soil quality of transferred-in cultivated land in the Ili River Basin is fairly good, which is different from those in Xinjiang and seven agricultural regions of China. There is still a large amount of arable grassland available for future cultivation in Ili. However, to ensure balanced development of agriculture and husbandry and to reduce ecological risks, future over-cultivation of grasslands should be limited, especially in ecologically vulnerable high-altitude areas (such as those above 2 000 m) and steep-slopes, which should receive special attention.

     

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