降尘、凋落物和生物接种对沙地土壤结皮形成的影响

土壤生物结皮广泛存在于干旱、半干旱地区,特别是沙漠地区。为了了解沙漠地区生物结皮的形成机制,2007年在科尔沁沙地对流沙进行了田间模拟降尘、添加凋落物和结皮生物接种的试验,研究了几种外界物质输入对沙漠结皮特性的影响。得到如下结果:降尘可以明显促进沙地土壤结皮的形成,但结皮盖度和厚度的增加与降尘量的多少并不存在线性关系,而是非线性关系。少量凋落物(100 g m-2)的存在可以增强降尘对结皮发育的促进作用,但输入较多的凋落物(250 g m-2)反而会抑制降尘的作用。结皮接种可以明显增强降尘对结皮形成的促进作用,其中干旱环境中接种地衣结皮的效果较好,在湿润环境中接种苔癣结皮的效果较好。结皮盖度对外来物质的输入较为敏感,结皮厚度随外来物质种类和数量的增加而变化较小。与光照、干旱环境相比,遮荫、湿润环境更有利于沙地结皮的形成和提高降尘等外来物质输入的效果。

Effects of falling dusk, litter and bio-inoculation on development of soil crust in desert

Soil bio-crust exists widely in semiarid and arid regions throughout the world, specially in desert area. An experiment on effects of simulated falling dust, litter and bio-inoculation on formation of soil crust in desert was carried out in 2006 in Horqin Sand Land to understand mechanism of soil crust formation in desert. Results show that (1) the falling dust obviously promoted development of soil crust, but no linear relationship was observed between the coverage and thickness of soil crust and amount of falling dust; (2) when little (100 g m-2) in amount, litter enhanced the effect of falling dust on development of soil crust, but reversely inhibited the effect, when it was more; (3) bio-inoculation significantly enhanced the effect, particularly the inoculation of lichen in arid environment, and of moss in relatively humid environment; (4) crust coverage was sensitive to input of extragenous substances, while crust thickness did not vary much with change in kind and amount of the input and (5) compared with illuminated and arid environment, shaded and wet environment was more conducive to development of soil crust and enhancement of the effects of inputs on crust formation.