Microbiological indicators of soil quality and degradation following conversion of native forests to continuous croplands |
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| Institution: | 1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, PR China;2. College of Forestry, Northwest A&F University, PR China;3. Chair of Soil Ecology, Technical University of Munich, Germany;4. Faculty of Organic Agricultural Sciences, Department of Soil Biology and Plant Nutrition, University of Kassel, Witzenhausen, Germany;5. Environmental Monitoring Station, Ding Xi, Gan Su Province, China;1. Department of Soil Science of Temperate Ecosystems, University of Göttingen, Germany, Büsgen-Institute, Büsgenweg 2, 37077 Göttingen, Germany;2. Department of Range and Wildlife Sciences, South Eastern Kenya University, Kenya, P.O. BOX 170-90200, Kitui, Kenya;3. Department of Agricultural Soil Science, University of Göttingen, Germany, Institute of Soil Science, Büsgenweg 2, 37077 Göttingen, Germany;4. Institute of Environmental Sciences, Kazan Federal University, Kremlevskaya, 18, 420049 Kazan, Russia |
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| Abstract: | Deforestation resulting from forest conversion to agricultural land use is an important issue worldwide. This phenomenon is known to influence the activity and size of soil microbial community due to changes in environmental conditions with subsequent losses of soil organic matter (SOM) and soil quality degradation. The objective of this study was to investigate the relationship between soil organic carbon (SOC) losses and enzyme activities following land use conversion from native forests to continuous croplands. The amount of soil microbial biomass carbon (SMBC) and the activity of five soil enzymes (i.e., urease, invertase, alkaline phosphatase, acid phosphatase and arylsulfatase) were measured in croplands derived from forests and adjacent natural forests all on similar soil type at Gorgan site located in Northeast Iran. The content of SMBC decreased (47–83%) with deforestation at both soil sampling depths (0–20 and 20–40 cm). With the exception of phosphatases, the absolute activities of soil enzymes (activity on a soil mass basis) tended to decrease significantly (15–35%) with continuous cultivation. However, the specific enzyme activities expressed either per unit of SOC or SMBC tended to increase (about 1.5–5.5 times) with conversion of forestlands to croplands. The significant positive correlation between enzyme activity per SMBC and C turnover rate may imply that a faster C cycle and loss due to deforestation is related to a greater enzymatic activity by a smaller size of microbial biomass in cropland soils. In brief, the specific activities of soil enzymes could be used to reveal SOM losses and soil degradation in natural forest ecosystems, and to identify changes in soil quality and fertility following deforestation. Changes or improvements in soil management such as cessation of cultivation or implementing agricultural practices that stop or minimize soil disturbance are most likely needed to stop further soil degradation, restore soil quality and rebuild SOC stocks to offset CO2 emissions in these ecosystems. |
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| Keywords: | Cultivation Deforestation Microbial activity Microbial biomass Enzyme specific activity C loss |
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