County-scale spatial distribution of soil enzyme activities and enzyme activity indices in agricultural land: implications for soil quality assessment.

Xiangping Tan,Baoni Xie,Junxing Wang,Wenxiang He,Gehong Wei,Xudong Wang

doi:10.1155/2014/535768

Abstract

Here the spatial distribution of soil enzymatic properties in agricultural land was evaluated on a county-wide (567 km2) scale in Changwu, Shaanxi Province, China. The spatial variations in activities of five hydrolytic enzymes were examined using geostatistical methods. The relationships between soil enzyme activities and other soil properties were evaluated using both an integrated total enzyme activity index (TEI) and the geometric mean of enzyme activities (GME). At the county scale, soil invertase, phosphatase, and catalase activities were moderately spatially correlated, whereas urease and dehydrogenase activities were weakly spatially correlated. Correlation analysis showed that both TEI and GME were better correlated with selected soil physicochemical properties than single enzyme activities. Multivariate regression analysis showed that soil OM content had the strongest positive effect while soil pH had a negative effect on the two enzyme activity indices. In addition, total phosphorous content had a positive effect on TEI and GME in orchard soils, whereas alkali-hydrolyzable nitrogen and available potassium contents, respectively, had negative and positive effects on these two enzyme indices in cropland soils. The results indicate that land use changes strongly affect soil enzyme activities in agricultural land, where TEI provides a sensitive biological indicator for soil quality.

Highlights

Soil is a natural resource playing key roles in organic matter (OM) decomposition, nutrient cycling, and water retention and release [1]
The activities of extracellular enzymes in soil vary significantly with seasons and geographical locations [14], as well as soil depth [15, 16]. Together these findings indicate that soil enzyme activities have broad-scale spatial variability depending on the environmental conditions
The soils were mostly fine in texture, with an average clay content of 33%

Summary

Introduction

Soil is a natural resource playing key roles in organic matter (OM) decomposition, nutrient cycling, and water retention and release [1]. Soils are subject to natural or environmental degradation, often accompanied by erosion and leaching. Degradation of soils occurs even without the intervention of human agricultural practices [2, 3], threatening this valuable resource. In arid and semiarid areas, needs to be preserved and improved for food security and environmental protection [4]. A variety of quantitative measures, including soil physicochemical properties indicative of the fundamental context of soil functions, have been extensively used to assess soil quality [5]. Most soil physicochemical properties change slowly in response to the environmental stress, with significant changes commonly detected only after many years. Soil biological properties are sensitive indicators for soil quality, which rapidly respond to minor environmental changes in the soil [6]

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Discussion

Conclusion