| Effect of land use on mineralization of soil carbon and nitrogen in semi-arid grasslands |
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| DOI：10.7606/j.issn.1000-7601.2017.05.11 |
| Key Words: semiarid loess region land use organic carbon mineralization N mineralization |
| Author Name | Affiliation | | DU Ning-ning | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China | | QIU Li-ping | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China | | ZHANG Xing-chang | State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China | | CHENG Ji-min | State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China |
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| Abstract: |
| To understand the effects of land use on the cycling of OC and N in soils of semiarid grassland, we analyzed the distribution and mineralization of OC and N in soils collected from grassland, cropland and shrub-land in Yunwu mountain natural grasslands. The results showed that averaged concentration of OC and N in soils decreased by 53% and 64% after conversion of grassland to cropland, and by 54% and 44% after conversion to shrub-land, respectively. The mineralization rate of OC declined with increasing of soil depth, with a range of 29%～46% decrease, while the proportion of mineralized OC increased with soil depth, with a range of 45%～67% increase. The conversion of grassland to cropland or shrubland significantly decreased OC mineralization rate but increased the proportion of mineralized OC. The decrease in OC mineralization rate declined, while increase of OC mineralization proportion increased with soil depth. The metrics of N mineralization declined with soil depth. For the 0～20 cm depth, the mineralization was characterized by the nitrification and immobilization of ammonium, and was dominated by nitrification. For the 40～80 cm depth, both nitrification and ammonification contributed to mineralization of N. The conversion of grassland to cropland or shrub-land decreased the metrics of N mineralization. For the top soils, these decreases were greater for the conversion of grassland to cropland, while for the deep soils, the decreases were greater for the conversion to shrub-land, when compared with each other. These results indicated that the cycling and availability of OC and N in grassland were significantly decreased after conversion of grassland to cropland or shrub-land in this semiarid region. Therefore, such land use changes should be avoided from the aspect of soil OC and N sequestration. |
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