荒漠区生物土壤结皮对土壤酶活性的影响

EFFECTS OF BIOLOGICAL SOIL CRUSTS ON SOIL ENZYME ACTIVITIES IN DESERT AREA

在干旱的沙漠生态系统中，生物土壤结皮对于沙丘的固定和土壤生物的维持起着相当重要的作用。土壤酶活性能敏感地指示土壤的恢复程度，是衡量沙区生态恢复与健康的重要生物学属性，而目前关于生物土壤结皮与土壤酶活性的关系研究很少。为探明生物土壤结皮对土壤酶活性的影响，以腾格里沙漠东南缘的人工植被固沙区生物土壤结皮覆盖的沙丘土壤为研究对象，根据固沙时间的不同将样地分为4个不同的区进行采样（57、49、32和22a固沙区），以流沙区（0a）和红卫天然植被区（〉100a）为对照。研究表明：人工植被固沙区的藻．地衣结皮和藓类结皮均可显著提高土壤碱性磷酸酶、蛋白酶和纤维素酶的活性（P〈0．05）；结皮类型显著影响土壤酶的活性，发育晚期的藓类结皮下土壤碱性磷酸酶、蛋白酶和纤维素酶的活性显著高于发育早期的藻一地衣结皮下土壤酶的活性（P〈0．05）；固沙年限显著影响土壤碱性磷酸酶、蛋白酶和纤维素酶的活性，且与这三种土壤酶活性均存在显著的线性正相关关系（P〈0．05）；目前，生物土壤结皮可显著提高0～20cm土层碱性磷酸酶、蛋白酶和纤维素酶的活性（P〈0．05），且这种影响随土层的增加而减弱。而且，生物土壤结皮下土壤碱性磷酸酶、蛋白酶和纤维素酶的活性表现明显的季节变化，表现为夏季〉秋季〉春季和冬季。腾格里沙漠东南缘的人工植被固沙区生物土壤结皮的存在与演替提高了土壤酶的活性，生物土壤结皮有利于该区土壤及其相应生态系统的恢复。

Biological soil crusts （BSCs） play an important role in fixation of sand dunes and maintenance of soil biota in arid desert ecosystems. Soil enzyme activities could be used as significant bioindicators of extent of soil restoration and important biological indices in evaluating ecological restoration and health in sandy areas. However, so far little has been reported on relationship between BSCs and soil enzyme activities. To understand how BSCs affect soil enzyme activities, sand dune soil under BSCs in the artificially revegetated areas at the southeastern edge of the Tengger Desert, China was taken as object of this study. Four sample lots different in sand-fixing history （57, 49, 32 and 22 a, respectively） were set for soil sampling, and a tract of mobile sand dunes （0 a） and a tract of natural vegetation land （ 〉100 a） in Hongweiof Shapotou were set as control. Results show that cyanobacteria-lichen and moss crusts could significantly increase activities of soil alkaline phosphatase, protease and cellulase in the artificial revegetation sand fixing areas （p 〈 0.05 ） . Type of crust significantly affected soil enzyme activities. The effects of moss crusts, typical of the late stage development of BSCs on activities of soil alkaline phosphatase, protease and cellulase were much higher than cyanobacteria-lichen crusts, typical of the early stage development of BSCs （p 〈 0.05 ） . Sand-fixing history also significantly affected activities of the soil enzymes, displaying a positive linear relationship with activities of the soil enzymes （p 〈 0.05 ） . BSCs significantly enhanced activities of the soil enzymes in the 0 ~ 20 cm soil layer （p 〈 0.05 ） and the effects weakened with increasing soil depth. Moreover, activities of the soil enzymes under the crusts varied with the season, following an order of summer 〉 autumn 〉 spring and winter. Therefore, apparently, the presence and succession of BSCs increases activities of the soil enzymes. The findings indicate that BSCs are beneficial to restoration of soil and corresponding ecological systems in the artificially revegetated desert areas at the southeastern edge of the Tengger Desert.