黄土高原生态分区及概况

黄土高原地域广阔,水土流失区域差异显著。为了有效治理水土流失,评估水土流失治理技术和模式及生态恢复建设工程的成效性,需要对黄土高原进行区域划分。依据自然条件、水土流失治理技术和模式的区域性特征及差异,基于国家基础地理信息系统数据的县级行政界,对其进行合并,进行生态分区的划分,并分别统计其气候、地形地貌、植被特征及水土流失现状,以期为黄土高原水土流失治理技术和模式的改良优化提供依据。主要结论如下:(1)黄土高原分为黄土高塬沟壑区,黄土丘陵沟壑区,沙地和农灌区,土石山区及河谷平原区。其中黄土高塬沟壑区和黄土丘陵沟壑区分别划分为两个副区。(2)黄土高原的气候、植被、水土流失具有明显的分区差异。降水和植被覆盖度自东南向西北递减,二者在空间分布上具有很好的一致性,降水量大的分区,植被覆盖度也高。在年际变化方面,丘陵沟壑区B2副区降水量呈增加趋势,其他分区呈减小趋势,变化均不显著。80年代以来,黄土高原和各生态分区的植被覆盖度均逐渐增加,黄土丘陵沟壑区的增加量最大。各分区的面平均气温均呈非显著增加趋势,90年代以来增温明显。(3)1970年以来,黄土高原侵蚀产沙强度减弱趋势显著,至2002—2015年,多年平均输沙模数在0.13—3924 t km~(-2) a~(-1)之间,侵蚀强度最大为中度侵蚀(2500—5000 t km~(-2) a~(-1)),但面积较小,主要分布于第二高塬沟壑区的泾河流域。

Ecological regionalization and overview of the Loess Plateau

The Loess Plateau covers a wide area where soil erosion is significantly different from region to region. To effectively control soil erosion and evaluate the effectiveness of soil erosion control technology, mode, and ecological restoration construction project, it is necessary to divide the Loess Plateau into several ecological regions. Given the regional characteristics and differences in the natural conditions of soil erosion control techniques and models, this study used the data in the National Fundamental Geographic Information System as references and re-divided the County boundary for appropriate ecological regionalization. The zonal characteristics of climate, topography, vegetation, and soil erosion status were analyzed to provide references for the improvement and optimization of soil erosion control technology and modes. The major findings are as follows. (1) The Loess Plateau was divided into five regions, namely, loess sorghum gully region, loess hilly and gully region, sandy land and agricultural irrigation region, earth-rocky mountainous region, and river valley plain region. The loess sorghum gully region and the loess hilly and gully region were then subdivided into two sub-regions. (2) The climate, vegetation, and soil erosion in the Loess Plateau showed clear regional differences. Precipitation and vegetation coverage decreased from southeast to northwest and were consistent in spatial distribution; regions with high precipitation showed high vegetation coverage. In terms of interannual variation, precipitation in the B2 sub-region of the hilly and gully region tended to increase, while it tended to decrease in the other regions, but the changes were not significant. Since the 1980s, vegetation coverage of the Loess Plateau and its regions have been increasing gradually, the most significant increase lying in the loess hilly and gully region. The area-averaged temperature in each region showed a non-significant increase, and a clear temperature increase has occurred since the 1990s. (3) Since 1970, erosion intensity of the Loess Plateau has been remarkably weakened. The average sediment transport modulus ranged from 0.13 to 3924 t km^-2 a^-1 until 2002 to 2015, and the maximum erosion intensity was moderate (2500-5000 t km^-2 a^-1), but the eroded area was small and lied in the Jinghe River basin, an area belonging to the B2 sub-region of the loess sorghum gully region.