祁连山北坡青海云杉林下苔藓层对土壤水分空间差异的影响

Effects of moss layers on the spatial variation in soil moisture in a Picea crassifolia forest on the north-facing slope of the Qilian Mountains

苔藓层是青海云杉林(Picea crassifolia forest)下的一个重要层片,它通过截持降水和减少土壤蒸发,对土壤水分产生影响。以祁连山北坡排露沟小流域的一个阴坡(海拔2700 m,植被为青海云杉林)作为样坡,于2010—2012年生长季对青海云杉林下有、无苔藓层覆盖地点的土壤水分进行对比观测。结果表明在祁连山青海云杉林下,苔藓层覆盖能减少土壤水分的空间差异。主要表现为:(1)无苔藓覆盖各观测点土壤含水量极差达62.2 mm,空间变异系数(CV)为17.3%;有苔藓层覆盖观测点土壤含水量空间变异系数为2.3%,仅为无苔藓覆盖地点的1/7.5,空间差异极显著(sig.<0.001)。(2)在持续无雨、小雨后和连阴雨天气下,有苔藓覆盖地点土壤含水量空间差异均显著小于无苔藓覆盖地点(sig.<0.05)。在持续无雨的情况下,无苔藓层覆盖各观测点土壤含水量空间变异系数平均值为19.8%,有苔藓覆盖地点土壤含水量空间变异系数平均值为6.6%,仅为无苔藓覆盖地点的1/3。小雨后,无苔藓覆盖各观测点土壤含水量空间变异系数平均值为15.2%,有苔藓覆盖地点土壤水分空间变异系数平均为5.1%,为无苔藓覆盖地点的1/3。连阴雨后,无苔藓覆盖各观测点土壤含水量空间变异系数平均为15.4%,有苔藓覆盖地点土壤水分空间变异系数平均为4.6%,为无苔藓覆盖地点的1/3.3。(3)持续无雨的情况下,苔藓层减小土壤水分空间差异的作用主要反映在土壤表层0—15 cm,对深层的作用不显著。而小雨和连阴雨后,苔藓层对15—80 cm深层土壤影响显著,而表层0—15 cm没有明显规律。

Moss layers comprise an important synusia under the Picea crassifolia forest, as they can change the soil moisture content by intercepting precipitation and reducing soil water evaporation. In this study, a shady slope at an elevation of 2700 m in the Pailugou Small Watershed of the Qilian Mountains was chosen as the study region to analyze the influence of moss layers on soil moisture content through observations performed from years 2010 to 2012 in the Picea crassifolia forest. The results showed that moss layers can dramatically reduce the spatial variability of soil moisture content during the growingseason of the Picea crassifolia forest. The spatial variability of the soil moisture content was 62.2 mm in the sites without moss layers, and the coefficient of variation （CV） in spatial change was 17.3%. The CV in the sites with moss layers was 2. 3%. The sites with moss layers only account for 1/7.5 of the without moss layer covered. So the spatial variability of soil moisture content showed significant differences between sites. The CV of the sites with moss layers was significantly lower than that of sites without moss layers （sig. 〈 0.05 ）. The presence of moss layers could reduce the spatial variability no matter the level of rainfall. For example, the CV of soil moisture content was 19.8% in the rainless sites without moss layers, while the sites with moss layers showed only 1/3 of this variation under rainless conditions. The CV of soil moisture content was 15.2% in the sites with light rain and without moss layers, while the sites with moss layers only showed 1/3 of this variation under light rain conditions. The CV of soil moisture content was 15.4% in the sites experiencing continuous rain that did not have moss layers, while the sites with moss layers only accounted for 1/3.3 of the sites with continuous min. Under rainless conditions, spatial differences in sites with moss layers were significantly smaller than those in sites without moss layers in soil layers at a depth of 0-15 cm. Under conditions of light or continuous rain, spatial differences between sites with moss layers had no correlation with the sites without moss layers in the 0--15 cm soil layers, as the function of moss layers in reducing spatial differences in soil water content was mainly reflected in the 15-80 cm soil layers.