Feedback of grazing on gross rates of N mineralization and inorganic N partitioning in steppe soils of Inner Mongolia
Feedback of grazing on gross rates of N mineralization and inorganic N partitioning in steppe soils of Inner Mongolia
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DOI：
10.1007/s11104-010-0575-z
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发表时间：
2011-03
期刊：
影响因子：
4.9
通讯作者：
Honghui Wu;M. Dannenmann;N. Fanselow;B. Wolf;Z. Yao;Xing Wu;N. Brüggemann;Xunhua Zheng;Xingguo H
中科院分区：
文献类型：
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作者：
Honghui Wu;M. Dannenmann;N. Fanselow;B. Wolf;Z. Yao;Xing Wu;N. Brüggemann;Xunhua Zheng;Xingguo H
植物-微生物相互作用是陆地生态系统地下氮素循环的重要调节因子。然而，这种相互作用大多被排除在研究总无机N通量和N向植物和微生物分配的实验装置中。有蹄类放牧很可能反馈土壤氮素通量，因此同时研究放牧对完整植物-土壤系统中植物和微生物N通量的影响具有特别重要的意义，在实验培养过程中植物-微生物相互作用持续存在。基于对完整植物-土壤整体的~(15)NH_4~+标记，研究了内蒙古草原不同载畜量(0、2.35、4.8和7.85 ha−1、放牧季节−1)对总N矿化速率和短期无机N在植物、微生物和土壤N库之间分配的反馈。结果表明，放牧对土壤总氮矿化的影响是不均匀的。在低放牧率下，总氮矿化有下降趋势，但随放牧压力的升高而增加。因此，在所调查的放牧强度中，放牧率与总氮矿化量之间没有显著的相关性。放牧降低了植物和微生物氮库中15N的回收率，但强烈促进了土壤中NO3-−的积累，从而对潜在的生态系统氮保持产生了负面影响。这似乎与放牧引起的易降解土壤碳有效性在放牧率增加时的下降密切相关。
Plant-microbe interactions are crucial regulators of belowground nitrogen cycling in terrestrial ecosystems. However, such interactions have mostly been excluded from experimental setups for the investigation of gross inorganic N fluxes and N partitioning to plants and microorganisms. Ungulate grazing is likely to feed back on soil N fluxes, and hence it is of special importance to simultaneously investigate grazing effects on both plant and microbial N fluxes in intact plant-soil systems, where plant-microbe interactions persist during the experimental incubation. Based on the homogenous15NH4+labelling of intact plant-soil monoliths we investigated how various stocking rates (0, 2.35, 4.8 and 7.85 sheep ha−1grazing season−1) in steppe of Inner Mongolia feedback on gross rates of N mineralization and short-term inorganic N partitioning between plant, microbial and soil N pools. Our results showed that the effect of grazing on gross N mineralization was non-uniform. At low stocking rate gross N mineralization tended to decrease but increased with higher grazing pressure. Hence, there was no significant correlation between stocking rate and gross N mineralization across the investigated grazing intensities. Grazing decreased15N recovery both in plant and microbial N pools but strongly promoted NO3−accumulation in the soil and thus negatively affected potential ecosystem N retention. This appeared to be closely related to the grazing-induced decline in easily degradable soil C availability at increasing stocking rate.