基于地统计学的黄土高寒区典型林地土壤水分盈亏状况研究

土壤水分是黄土高寒区水循环、地下水补给和植被恢复的关键因素,基于地统计学研究土壤水分空间分布及其盈亏状况,揭示林地土壤水分的空间分布规律、变异特征及空间结构,对于区域植被恢复具有重要价值。以大通县安门滩小流域人工林地作为研究对象,运用地统计学方法对其5月、7月和9月的土壤储水量、林地耗水量和土壤水分盈亏量进行综合分析。研究结果表明:(1)土壤储水量总体表现为9月5月7月,而林地耗水量为7月9月5月,5—7月绝大多数林地的土壤水分呈亏损状态,而7—9月所有林地土壤水分都得到了补充,总体来看,5—9月研究区多数林地的土壤水分有所盈余,土壤储水量、林地耗水量和土壤水分盈亏量均采用指数模型作为最优理论变异函数模型;(2)5月、7月和9月土壤储水量呈南高北低、西高东低的空间分异规律,且西南-东北方向变异较东南-西北方向剧烈;各月林地耗水量在西南-东北方向变异较东南-西北方向剧烈,总体表现为西南部区域低于东北部区域;在5—7月、7—9月和5—9月这三个时期内,土壤水分盈亏量的取值均呈现出东北部区域小于西南部区域的特点。综上,当地土壤水分状况与林地耗水量分布格局并不完全匹配,虽然绝大部分林分能够维持土壤水分收支平衡,但部分山脚处的青杨林地和中部区域的华北落叶松林地出现了土壤水分亏损的现象。为防止林地水分环境恶化,在之后黄土高寒区的植被建设过程中,应适当调整林分配置。

Soil moisture surplus and loss of typical forestland in loess alpine area by the geostatistical analyst method

Soil moisture is a key factor for water circulation, groundwater supply, and vegetation restoration in the loess alpine region. Based on geostatistics, the spatial distribution of soil moisture and its profit and loss are studied to reveal the spatial distribution law, variation characteristics, and the spatial structure of soil moisture in forestland, which is of great value for regional vegetation restoration. In this study, the artificial forest land in the Anmentan watershed of Datong County was selected. The soil water storage, forest water consumption, and soil water profit and loss in May, July, and September were comprehensively analyzed by the geostatistical method. The results showed that:(1) the overall performance of soil moisture was in order of September > May > July, while the water consumption of woodland was in order of July > September > May. The soil moisture of most of woodland in May-July was in a loss state. The soil moisture of all woodland in July-September was supplemented. There was a surplus of the soil moisture in most woodlands in the study area in May-September. The exponential model could be used as a optimal theoretical variation function model in soil water storage, woodland water consumption, and soil moisture surplus and loss. (2) In May, July and September, the soil water storage capacity was generally higher in the south and the west, but lower in the north and the east. The variation in the southwest-northeast direction was more intense than that of the southeast-northwest direction. The water consumption of forest land in each month was more intense in the southwest-northeast direction than in the southeast-northwest direction, and its overall performance in the southwest is lower than that in the northeast. In three periods of May-July, July-September, and May-September, the value of soil water surplus and loss showed the characteristics of the northeast region smaller than the southwest region. In summary, the local soil water status does not exactly match the water consumption distribution pattern of the forest land. Although most of the forest stands can maintain the balance of soil moisture, some Populus cathayana forests at the foot of the mountain and Larix principis-rupprechtii forests in the central region had a phenomenon of soil moisture loss. In order to prevent the deterioration of the water environment of woodland, the stand allocation should be adjusted appropriately in the process of vegetation construction in the loess alpine area after that.