古尔班通古特沙漠生物结皮小尺度分异的环境特征

Eco-environment Change of Biological Crusts on Longitudinal Dune Surface in Gurbantunggut Desert

古尔班通古特沙漠广泛存在的生物结皮，对地貌部位有极强的选择性分布，其实质是生物对环境条件综合适应的一种生态表现。2002年3～11月在个体沙丘表面初步开展了生物结皮类型小尺度环境分异规律研究。结果表明：苔藓结皮、地衣结皮和藻类结皮依次分布于垄间、沙垄两坡中部和坡上部，从垄间往垄顶，生物结皮盖度逐渐减小，厚度变薄，抗压性减弱。苔藓结皮分布区的物质组成以细沙和极细沙为主，春季表层土壤水分在5％以上，短命植物广泛发育，基质稳定；坡中部的地衣结皮分布区以细沙为主，春季表层土壤水分在4％左右，短命植物亦有广泛分布，地表受风沙活动影响较小；沙垄上部和顶部的藻类结皮分布区，是沙垄表面活动性最强和土壤水分最差的区域，物质组成以中沙为主，高等植物中自梭梭为优势种，可见藻结皮是三类结皮中最能适应恶劣环境的生物结皮类型。

Gurbantunggut Desert, the largest fixed and semi-fixed desert in China, are mostly covered by well-developed biological crust. The distribution of biological crusts has selective characteristics at different positions on sand dune surface. The species composition, thickness and compression strength vary with different types of biological crust. Such selective distribution of biological crusts and their eco-environmental condition on longitudinal dune surface were studied in 2002. The results showed that moss crusts mainly distributed in the interdune area, where sand surface was stable and the dominant grain size were fine and extra-fine sands. The soil moisture could reach 5 % in early spring and ephemeral plants grew well. Lichen crusts mainly distributed from lower to middle slopes, where the dominant grain size was fine sands. The soil moisture in spring was about 4 % and also possessed rich ephemeral plants. Algae crusts occurred from upper slope to the top of dune, where the sand surface was active and the soil moisture content was the lowest, which indicated that Algae crust is the most adaptable species to rigorous habitats.