土壤水分是沙地植被格局和过程改变的主要驱动力,也是干旱半干旱区植物生长最大的限制因子。沙漠地区的土壤水分表现出明显的空间异质性。以高寒半干旱沙地青海湖东沙地为研究区,以栽植人工固沙植物（小叶杨、樟子松、沙棘和乌柳）的沙丘和自然固定沙丘（沙蒿为优势种）作为研究样地,探讨不同固沙植物影响下的沙丘不同地貌部位土壤水分变化特征。结果表明：（1） 土壤水分的季节变化受降水、植被蒸腾作用和地表蒸发的共同影响,不同物种的分布模式具有差异性,但都表现为7月的土壤含水量最高。（2） 同一植物在不同地貌部位的土壤含水量具有差异性,小叶杨在迎风坡最高,樟子松、沙棘和乌柳在背风坡最高,而沙蒿在丘顶最高,但只有乌柳的土壤含水量在沙丘地貌部位间的差异明显（P<0.05）。不同植物在同一地貌部位的土壤含水量也具有差异性,迎风坡樟子松的土壤含水量最小,只有1.81%,而沙蒿的土壤含水量能达到3.48%。丘顶处乌柳的土壤含水量仅为1.82%,而沙蒿可达3.58%。背风坡处的土壤含水量相差不大,乌柳最大为3.41%。（3） 土壤水分随着土层深度的变化模式不同,土壤含水量整体表现为10~20 cm处最高。不同植物的土壤水分的垂直分布具有差异性,小叶杨和樟子松下方的土壤含水量随着土层深度的增加而降低,沙棘和沙蒿表现为120 cm土层深度内无明显变化,而乌柳下方的土壤含水量随着土层深度的变化在各地貌部位不同,具体表现为迎风坡无明显变化、丘顶降低和背风坡增加的趋势。土壤水分在高寒半干旱沙地不同植被恢复措施下的分布除受到降水、土壤分布、物种类型、植物根系分布的影响之外,还与沙丘微地貌形态具有一定的相关性。

Spatial-temporal heterogeneity of soil moisture is the main driving force for variation of vegetation patterns and processes in the desert, directly affecting plant growth in arid and semi-arid regions. Here, we used the dunes of planted sand-fixing plants (Populus sylvestris, Pinus sylvestris, Hippophae rhamnoides, and Salix cheilophila) at the eastern sandy shore of Qinghai Lake as study site and compared them to natural fixed dunes dominated by Artemisia ordosica. Our objectives were to analyze how soil’s moisture and geomorphological features influence the plants’ distribution in alpine semi-arid sandy lands. Our results showed that: (1) Precipitation, vegetation transpiration, soil’s surface evaporation were the main environmental features affecting soil’s seasonal moisture content, that varied among species, but that was the highest in July; (2) Depending on the dune’s position, soil moisture content might be different, even for the same species: Populus simonii had the most increased soil’s moisture content windward, while P. sylvestris, H. rhamnoides, and S. cheilophila had the most increased soil’s moisture content when leeward, and A. ordosica had the highest soil’s moisture content at dune’s top. However, geomorphology only played a significant difference in soil’s moisture content for S. cheilophila (P<0.05). Soil’s water content for different species in the same position was also different: At the windward, soil’s water content for P. sylvestris was 1. 81% and that of A. ordosica was 3.48%. At the dune’s top, the soil’s water content for S. cheilophila was 1. 82%, while that for A. ordosica was 3.58%. There was no significant difference in soil’s moisture content among species at the leeward, but that for S. cheilophila was 3.41%; (3) Soil’s moisture varied with depth and was the highest at 10-20 cm. The soil’s moisture vertical distribution also varied according to the plant species: it increased with depth with P. simonii and H. rhamnoides, while it gradually decreased with increasing soil depth for the other species. The soil’s water content decreased with soil’s depth for P. sylvestris and P. sylvestris, while it showed no noticeable change with H. rhamnoides and A. sylvestris up to 120 cm in depth. A varying soil’s water content was observed with S. cheilophila in different geomorphological positions and soil layers, which showed that no obvious change on the windward, lowering of the chest and increasing of the leeward. The soil’s moisture content distribution with different vegetation restoration measures in alpine semi-arid sandy land was affected by precipitation, soil distribution, species type, plant root distribution, and dunes’ micro-topography.