科尔沁沙地放牧干扰恢复过程中植被组成和生物结皮微生物数量的变化

通过对科尔沁沙地禁牧10年后自然恢复状况的调查和实验分析,得出以下结论:(1)不同放牧强度自然恢复过程中,样地维管植物明显呈现出由一年生植物组成向多年生植物组成过渡的特点,盖度表现为轻牧恢复区(L)、中牧恢复区(M)、重牧恢复区(H)的盖度显著高于对照恢复区(C)、未围封放牧区(N)(P＜0.05);各处理样地生物结皮中苔藓植物和藻类植物的组成变化不大,但盖度表现为:苔藓结皮 L＞M＞H＞C＞N 区,藻结皮C＞H＞M＞L＞N区.(2)围封各恢复区(L、M、H)和未围封放牧区(N)藓结皮的含水量、结皮厚度及有机质含量方面显著高于藻结皮的(P＜0.05),而pH值却低于藻结皮的.(3)围封各恢复区微生物的数量显著高于未围封放牧区的(P＜0.05),在围封各恢复区内不论是藻结皮还是藓结皮,细菌、自身固氮菌和放线菌的数量在中度放牧恢复区数值最大,重度放牧恢复区的数量最少,两者差异达到显著水平(P＜0.05).(4)藻结皮、藓结皮微生物数量都随土壤深度的增加而呈降低的趋势,0～3 cm层的与3～5、5～10、10～20 cm三层的有显著差异(P＜0.05),藓结皮层及下层土壤微生物的数量要明显高于藻结皮层及下层土壤的.

Vegetation Components and Microbe Quantity in Microbiotic Soil Crusts of the Grazing Land during Natural Restoration in Horqin Sand Land,Inner Mongolia

Vegetation and mocrobe in several grassland areas which had grazed at different grazing pressures for 5-years and then naturally recovered for 10-years in Horqin sand land were investigated and analyzed.The results are as follows.(1) The component characteristic of the vegetation type comes to be perennials from annual plants in this process of the natural restoration.The vascular plant coverage in the plots of L (light-grazing recovery plot),M (moderate-grazing recovery plot),and H (heavy-grazing recovery plot) is significantly higher than that in the plots of C (control recovery plot) and N (non-enclosed grazing plot) (P<0.05).Species of mosses and alga in mocrobiotic soil crusts of different plots are similar,but the coverage of mosses and alga had a big difference.For example,the coverage of mosses in the plots can be ranked in L>M>H>C>N,and the coverage of alga is C>H>M>L>N.(2) Water content,crust thickness and organic content in moss crusts are significantly higher than that in alga crusts(P＜0.05),but the pH value is lower than that of alga crusts.(3) Microbe quantity in microbiotic soil crusts in all enclosed plots is significantly higher than that in non-enclosed grazing plots (P＜0.05).The quantity of bacteria,nitrogen-fixing bacteria and actinomyces in mosses and alga crusts are highest in light or moderate grazing recovery plots,and are lowest in a high grazing recovery plot(P＜0.05).(4) Microbe quantity in mosses and alga crusts indicate a trend to reduce with the increase of soil depths.The microbe quantity in 0～3 cm soil layers has a significantly difference (P<0.05) with that in layers of 3～5,5～10,10～20 cm,respectively.Microbe quantity in mosses crusts and its lower soil layer are higher than that in alga crusts and its lower soil.