基于土壤微生物生物量碳和酶活性指标的土壤肥力质量评价初探

Soil quality assessment based on soil microbial biomass carbon and soil enzyme activities

土壤质量评价是分析土壤管理措施对土壤质量影响的最重要的手段。以松嫩平原草地为对象,分析玉米地、苜蓿地、自然恢复草地、羊草地和羊草割草地5种利用方式短期(4年)内土壤微生物生物量碳含量以及过氧化氢酶、脲酶、蔗糖酶和碱性磷酸酶活性的变化,采用土壤质量指数法对不同土地利用方式下的土壤肥力质量进行定量评价,探讨基于土壤微生物生物量碳和酶活性指标的土壤肥力质量变化的原因。结果表明,土地利用方式对土壤微生物生物量碳含量、脲酶活性和蔗糖酶活性具有极显著(P<0.01)的影响,而对过氧化氢酶活性和碱性磷酸酶活性没有显著影响。草地恢复明显提高了土壤微生物生物量碳的含量与土壤酶的活性,其中蔗糖酶活性增加幅度最大,4种草地利用方式的敏感性指数均大于1.94,响应最敏感,而过氧化氢酶活性的增加幅度最小,4种草地利用方式的敏感性指数均小于1.13,响应最差。苜蓿地、自然恢复草地、羊草地和羊草割草地中分别有4个、3个、2个和1个土壤微生物指标的敏感性指数大于1.5,研究区内种植苜蓿对土壤微生物指标的改善作用最大。线性与非线性土壤质量指数间具有极显著的正相关关系,表明它们均能准确的反映出土地利用变化对土壤肥力质量的影响。草地恢复显著提高了研究区内的土壤肥力质量,其中苜蓿地的土壤质量指数最高,其线性和非线性土壤质量指数分别为0.89和0.60,自然恢复草地、羊草割草地和羊草地次之,玉米地最低,其线性和非线性土壤质量指数仅为0.55和0.30。研究表明,在松嫩平原土壤条件较差的地区种植苜蓿可能是改善土壤肥力质量最佳的利用方式之一。

Soil quality evaluation is one of most important approach to analyze the effects of soil management practices on soil quality. Using data from a short-term land use experiment （four years） in the Songnen Plain, this study investigated the effect of five land use types including cropland, restored grassland, Leymus chinensis grassland and Leymus chinensis grassland for mowing and Alfalfa forage land on the changes of soil microbial biomass carbon （MBC） and four enzyme activities （catalase, urease, alkaline phosphatase and invertase）. Additionally, the soil qualities under different land uses were evaluated using the soil quality index. Results showed that land use treatments had a significant effect on the soil MBC and activities of urease and invertase, whereas no significant differences were found for the activities of catalase and alkaline phosphatase. Grassland colonization significantly increased the soil MBC and soil enzyme activities. Soil invertase activity was the most sensitive indicator to land uses with a sensitivity index greater than 1.94, while soil catalase activity was the least sensitive indicator to land use types with a sensitivity index less than 1.13. Numbers of sensitive index larger than 1.50 at Alfalfa forage land, restored grassland, Lyemus chinensis grassland and Lyemus chinensis grassland for mowing were 4, 3, 2 and 1, respectively, indicating the improvement of alfalfa planting on soil microbial indicators was better than other land use treatments. All the two soil quality indices based on linear and non-linear scoring method can accurately reflect the effect of land uses on changes of soil quality due to the significant positive correlation between the two indices. Conversion from cropland to grassland significantly improved the soil quality in the study area. Soil quality index in the Alfalfa forage land was the highest with a value of 0.89 for linear scoring function and 0.60 for non-linear scoring function, followed by the restored grassland, Leymus chinensis grassland and Leymus chinensis grassland for mowing, and the land use type of cropland has the lowest soil quality index with a value of 0.55 for linear scoring function and 0.30 for non-linear scoring function. Our results indicated that the alfalfa plantation may be a good land use practice for poor soils in the study area.