关键词: 高寒半干旱沙地, 固沙植物, 土壤水分, 季节变化, 垂直分布, 青海湖

Abstract:

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.

Key words: alpine semi-arid sandy land, sand-fixing plants, soil moisture, seasonal variation, vertical change, Qinghai Lake