不同生境对人工结皮发育及表土氮、磷含量及其代谢酶活性的影响

土壤生物结皮对于改善荒漠地区的生态环境和土壤的增肥改良具有重要作用.本研究以库布齐沙漠固定沙丘(迎风坡、坡顶、背风坡和丘间地)披碱草和沙蒿群落下长期发育(8年生)的人工藻结皮为研究对象,测定不同生境下人工结皮对表层土壤氮、磷元素含量以及相关土壤酶活性的影响.结果表明,在不同立地条件下,沙丘顶部结皮叶绿素a和土壤可溶磷含量最高,分别为4.24 mg/g和2.926 mg/kg.丘间地结皮层土壤碱性磷酸酶活性、总磷含量及脲酶活性为最高,迎风坡结皮生物量和土壤碱解氮、速效磷含量以及土壤酶活性明显高于背风坡结皮层土壤.在相同立地条件下,披碱草下结皮生物量、碱解氮、速效磷含量和脲酶及碱性磷酸酶活性显著高于沙蒿下的结皮土壤.本研究表明生境的差异性导致人工结皮发育程度不同,进而对表土氮、磷含量及其代谢酶产生不同影响,人工生物结皮的发育程度与表土氮磷素含量及其代谢酶活性之间存在显著相关性.不同植被群落对生物结皮发育具有不同的作用,披碱草对人工生物结皮影响的正效应高于沙蒿.

Effects of Different Habitats on Artificial Crust Development and Surface Soil Nitrogen, Phosphorus Contents and Enzymes Activities

Biological soil crusts play significant roles in improving soil nutrients and ecological environment in arid and semi-arid area. To understand the effects of habitat diversity on the crust and surface soil, eight-year-old man-made algal crusts in Hopq Desert under Elymus dahuricus and Artemisia desterorum vegetation communities at four different topographical conditions: windward, peak, leeward and slack of the sand dune, were studied. The results showed that the crust biomass and soil available phosphorus were highest at the peak of the dune, reached to 4.24 mg/g and 2.926 mg/kg respectively, while total phosphorus and the activities of phosphatase and urease were highest at the dune slack. The crust biomass, soil available nitrogen, available phosphorus and the soil enzyme activity in the soil at the windward of the dunes were higher than those of the leeward obviously. At at the same topographical condition, the crust biomass, available nitrogen, available phosphorus, and the activities of phosphatase and urease in the surface soil under the Elymus dahuricus community were all higher than those of the Artemisia desterorum. The results indicated that the developing degree of the cultured algal crust had significant correlation with the surface soil nitrogen, phosphorus and soil enzyme activities. The habitat diversities resulted in different effects of the biological soil crust on the contents of nitrogen, phosphorus and the activities of soil enzymes, and different vegetation communities above the biological soil crusts produced different effects on the crust, generally the effects of the Elymus dahuricus community were higher than those of the Artemisia desterorum.