半干旱黄土区坡面尺度柠条生长状况及影响要素分析

Spatial patterns of Caragana korshinskii growth on hillslope scale and influencing factors in the semi-arid Loess Plateau

以半干旱黄土丘陵区典型小流域坡面大规模人工种植柠条林为例,基于坡面不同部位柠条生长状况和生境条件调查,定量分析了地形变化、土壤水分及灌木密度对柠条生长的直接、间接影响及其贡献率。结果表明:(1)东坡大株柠条生长明显好于南坡,下坡位柠条生长状况略好于中上坡位,其他各坡位之间柠条生长状况差异较小;(2)大株柠条生长与浅层土壤水分有正相关关系,而与灌木密度和深层土壤水分则呈负相关关系;大株柠条灌木高度、灌木纵截面积和冠幅体积对浅层土壤水分的响应敏感,冠幅长度对坡向和坡位的响应较为敏感,冠幅宽度对灌木密度的响应较为敏感;(3)地形和土壤水分变化解释了59.9%的大株柠条生长变异,其中坡向、坡位和浅层土壤水分是影响大株柠条生长的主导环境因子,它们分别解释了21.1%、16.0%和13.1%的柠条生长变化。研究认为半干旱黄土区人工植被恢复既要重视空间布局,也要在后期实施必要的管理措施以维持人工林地的稳定性。

Topography and soil moisture are the key factors affecting the spatial growth patterns of artificial Caragana korshinskii shrubs in the semi-arid loess region. However, the recognition of the growth status of C. korshinskii shrubs affected by topographic variation, soil moisture content, and shrub density is limited on the hillslope scale. In this study, we selected a typical artificial C. korshinskii shrub on the hillslope as a research model, and the data on its growth status and habitat conditions under different （east-and south-facing） slope positions were collected. Furthermore, the relationships between the growth status of C. korshinskii shrubs and the shrub density, topographic variation, and soil moisture content were quantitatively analyzed using the Pearson correlation, path analysis, and RDA. The following results were obtained in this study. （1）The growth status of C. korshinskii shrubs on the east-facing slope was significantly better than that of the shrubs on the south-facing slope. Furthermore, the growth status of the C. korshinskii shrubs on the lower slope position was slightly better than that of the shrubs on the upper or middle slope positions, and no significant difference was observed between the other slope positions. （2） Shallow soil moisture content had a direct, positive effect on the growth status of C. korshinskii, and the shrub density and deep soil moisture content had a negative relationship with the growth status of C. korshinskii. For the large C. korshinskii shrubs, the height, crown diameter multiplied by the height, and canopy volume showed sensitive responses to the shallow soil moisture content. The results also demonstrated that the crown length responded with more sensitivity to the slope aspect and slope position than the other factors did, and the crown width showed a sensitive response to shrub density. （3） The topographical features （slope aspect, position, and gradient） and soil moisture content （shallow and deep soil moisture contents） determined the growth status of C. korshinskii shrubs and explained the 59.9% variation in the growth changes. Furthermore, the variation of the growth changes in the slope aspect, slope position, and shallow soil moisture content were 21.1%, 16.0%, and 13.1%, respectively. Therefore, human-introduced vegetation restoration of the semi-arid loess regions should consider the spatial pattern of vegetation based on soil water conditions of the hillslope scale, and the scientific management of the middle and later periods of revegetation is also necessary to sustain the C. korshinskii shrub in the semi-arid loess region.