不同荒漠化阶段植被生态特征对土壤环境因子的响应——以民勤荒漠绿洲过渡带为例

荒漠绿洲过渡带是荒漠化和绿洲化两种地理过程共同影响的生态交错区,是恢复生态学重点关注的区域。利用第五次全国荒漠化和沙化监测数据,采用方差分析和冗余分析,研究了民勤荒漠绿洲过渡带4种不同荒漠化发展阶段的植被生态特征和土壤环境因子的变化规律与相互关系。结果表明:(1)随着荒漠化的发展,土壤环境因子中,除有效土层厚度逐渐变浅外,风蚀痕迹占地率、表土砾石含量、盐碱斑占地率和坡度均呈现增加的动态趋势;植被因子中,除优势种盖度与植被总盖度的比值逐步增加,物种丰富度、优势种多度等其他指标均表现出明显的下降特征;(2)土壤环境因子中,有效土层厚度在4种荒漠化阶段对植被生态特征的影响程度达显著水平(P0.05),风蚀痕迹占地率在轻度、中度和重度阶段是植被生态特征变化的主导驱动因子。其他因子在多数荒漠化阶段与植被生态特征相关性不显著;(3)相比其他荒漠化阶段,中度阶段中植被生态特征对土壤环境因子的响应更加敏感,应是荒漠化防治重点关注的阶段。

Vegetation and soil environmental factor characteristics, and their relationship at different desertification stages: a case study in the Minqin desert-oasis ecotone

The desert oasis ecotone is a ecological zone influenced by desertification and oasisization, and is a major research focus for restoration ecology. Based on the fifth national desertification monitoring, our research used variance analysis and redundancy analysis to study the relationships between vegetation ecological characteristics and soil environmental factors at four different desertification developmental stages in the Minqin Desert Oasis Transition Zone. The results showed that (1) with the development of desertification, all the soil environmental factors, such as occupancy rate of wind erosion, topsoil gravel content, and saline-alkali spots, showed an increased dynamic trend, while the effective soil thickness showed a decreased dynamic trend. Among the vegetation factors, species richness, total vegetation coverage, shrub coverage, herb coverage, dominant species coverage, plant height, and abundance decreased significantly, whereas the ratio of dominant species coverage to total vegetation coverage increased gradually; (2) among the soil environmental factors, the effects of the effective soil layer thickness on vegetation ecological characteristics at the four stages of desertification were significant; the occupancy rate of wind erosion was the dominant driving factor behind the variation in the vegetation ecological characteristics at the mild, moderate, and severe stages, but other factors were not correlated with vegetation ecological characteristics for most desertification stages; and (3) compared to the mild, severe, and extremely severe desertification stages, the response of vegetation ecological characteristics to soil environmental factors was more sensitive at the moderate stage and it should be the focus for desertification control.