喀斯特山区土地利用方式转变对土壤酶活性及其化学计量特征的影响

Abstract

土地利用变化引起的土壤理化性质改变会显著影响土壤碳氮磷养分含量及其化学计量特征，然而由于不同研究区域环境异性较大，土壤胞外酶活性及其化学计量特征与各土壤因子间的协同变化规律仍不明确。以喀斯特山区7种典型土地利用方式（马尾松林地、柏树林地、灌木林地、梯田菜地、梯田撂荒地、坡面撂荒地和坡耕地）为研究对象，采用时空互代法研究土地利用方式转变过程中6种土壤胞外酶活性（β-1，4-葡萄糖苷酶、β-1，4-木糖苷酶、纤维素二糖水解酶、β-1，4-N-乙酰葡萄糖苷酶、亮氨酸氨基肽酶和酸性磷酸酶）及其化学计量特征的变化规律，并分析它们与土壤理化因子之间的关系。结果表明坡耕地转变土地利用方式后，土壤养分状况和酶活性得到明显改善，并且土壤微生物通过调节酶的表达和活性提高了磷素的有效性，促进了土壤养分的平衡。总体来看，坡耕地转马尾松和柏树林地后土壤质量改善的效果更加显著，但加剧了土壤磷素的限制。此外，土壤全氮含量、C∶N、N∶P和pH是土壤酶活性变化的主要驱动因素，土壤酶活性与养分含量具有趋同性且受土壤pH的调控。因此，喀斯特地区马尾松和柏树人工林的经营管理过程中应考虑磷素的投入以缓解人工林生态系统的磷限制。;Changes of soil physicochemical properties caused by land use conversion will significantly affect the content of nutrients (carbon, nitrogen and phosphorus) in soil and its stoichiometric characteristics. However, it is still unclear about the synergistic change between soil extracellular enzyme activity as well as its stoichiometric characteristics and soil factors due to the large environmental difference in different study areas. In this study, 7 kinds of typical land use types (Pinus massoniana land, Platycladus orientalis land, shrub land, terrace of vegetable field, terrace of abandoned land, sloped abandoned land, and sloped farmland) were selected as research objects in karst mountainous area. Taking the existing sloped farmland as the reference substance, the variation of 6 kinds of extracellular enzyme activity and its stoichiometric characteristics (β-1,4-glucosidase, cellobiohydrolase, β-1,4-xylosidase, β-1,4-N-acetylglucosaminidase, leucine aminopeptidase and acid phosphatase) were compared before and after the change of land use types using the spatio-temporal contrast method, and the relationship between them and soil physical and chemical factors were also analyzed. The results showed that soil nutrient status and enzyme activity were significantly improved after the conversion of land use type from sloped farmland to other, which not only significantly increased the nutrient content but also promoted the soil nutrient balance, because soil microorganism regulated the expression and activity of enzymes and the availability of phosphorus was greatly improved. In general, land use conversion from the sloped farmland to Pinus massoniana land and Platycladus orientalis land showed similar and best effect of soil quality improvement, whereas it also increased the restriction of soil phosphorus. In addition, soil total nitrogen content, C:N, N:P and pH value were the main factors driving the change of soil extracellular enzyme activity. The change of soil enzyme activity was consistent with that of nutrient content, and was regulated by the power of hydrogen. Therefore, the phosphorus input should be considered in the management of Pinus massoniana and Platycladus orientalis forest land in karst areas for alleviating the phosphorus restriction of artificial forest ecosystem.