Soil N transformations and its controlling factors in temperate grasslands in China: A study from ¹⁵N tracing experiment to literature synthesis

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• 作者：Jing Wang ; Liang Wang ; Xiaojuan Feng ; Huifeng Hu ; Zucong Cai ; Christoph Müller ; Jinbo Zhang
• 刊名：Journal of Geophysical Research: Biogeosciences
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：121
• 期：12
• 页码：2949-2959
• 全文大小：1.3MB
• ISSN：2169-8961

文摘

Temperate grasslands in arid and semiarid regions cover about 40% of the total land area in China. So far, only a few studies have studied the N transformations in these important ecosystems. In the present study, soil gross N transformation rates in Inner Mongolia temperate grasslands in China were determined using a ¹⁵N tracing experiment and combined with a literature synthesis to identify the soil N transformation characteristics and their controlling factors in a global perspective. Our results showed that the rates of gross N mineralization and immobilization NH₄⁺ were significantly lower, while autotrophic nitrification rates were significantly higher in Chinese temperate grassland soils compared to other regions in the world. In particular, the primary mineral N consumption processes, i.e., immobilization of NO₃⁻ and NH₄⁺, and dissimilatory nitrate reduction to ammonium, were on average much lower in temperate grassland soils in China, compared to other temperate grassland regions. The reduced heterotrophic activity and microbial growth associated with lower soil organic carbon and arid climate (e.g., mean annual precipitation) were identified as the main factors regulating soil N cycling in the studied regions in China. To restrict NO₃⁻ accumulation and associated high risks of N losses in these arid and semiarid ecosystems in China, it is important to develop the regimes of soil organic C and water management that promote the retention of N in these grassland ecosystems.