不同固定程度沙地油蒿根系与土壤水分特征研究

Correlations Between Distribution Characteristics of Artemisia ordosica Root System and Soil Moisture Under Different Fixation Stage of Sand Dunes

水分是干旱、半干旱地区生态系统中最重要的限制因子,而根系是植物吸收水分的重要器官。为研究不同固定程度沙地油蒿根系与土壤水分特征,分别选取毛乌素沙地固定、半固定和流动沙地上的油蒿植株,采用分层取土的方法调查不同类型沙地上的油蒿根系分布特征,同时用TDR测定相应层次土壤水分。结果表明:固定、半固定和流动沙地油蒿根系均以粗根最多,中粗根次之,细根最少,且随着土层深度的增加,3种级别的根量均呈指数状递减;固定、半固定和流动沙地0～40 cm范围内细根所占比重分别为:79.11%、74.71%和53.23%,固定和半固定沙地油蒿植株主要利用0～40 cm范围内的土壤水分,而流动沙地油蒿植株能更多地利用40 cm以下土壤水分。从流动沙地到固定沙地,植被盖度不断增加,植被对土壤水分的消耗也逐渐加大,同时由于地表发育的生物结皮具有阻碍降水入渗的作用,造成固定沙地土壤水分不断恶化,久之将造成固定沙地油蒿群落的衰退。

Water is the most important limiting factor to the arid and semi-arid ecosystems, while the root sys- tem is the most important organ for plants to uptake soil moisture. In order to analyze the correlations between the distribution characteristics of Artemisia ordosica roots and soil moisture in different site conditions with different sand faxing status, A. ordosica plants were respectively selected from the fixed, semi-fixed and drifting sand-dunes for the study in Mu Us sandy land. The distribution features of A. ordosica root systems on different plots were observed by sample collection at different soil depth, and the corresponding soil moisture was measured with TDR by layers. The results showed that the A. ordosica root systems contained most of coarse roots at the three types of sand-dunes, followed by medium sized roots and with the least fine roots, and the biomass of the three kinds of roots was all de- creased with the increment of soil depth in exponential way. The proportion of fine roots collected at 0 -40 cmdepth in the fixed, semi-fixed and drifting sand-dune areas was 79.11%, 74.71% and 53.23%, respectively. A. ordosica plants grown in the fixed and semi-fixed sand-dunes mainly utilized the soil moisture at 0 -40 cm depth, whereas the A. ordosica plants grown in the drifting sand-dune could use more soil moisture below 40 cm in depth. Along with the gradual increase of vegetation coverage from the drifting sand-dunes to fixed sand-dune types, more soil moisture was consumed. Meanwhile, the development of biological soil crusts on the surface of fixed sand- dunes impeded the infiltration of precipitation, which led to the deterioration of soil moisture in the fixed sand- dunes, which would finally cause the recession of A. ordosica in the fixed sand-dunes in a long time run.