Prolonged summer droughts retard soil N processing and stabilization in organo-mineral fractions
Prolonged summer droughts retard soil N processing and stabilization in organo-mineral fractions
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DOI：
10.1016/j.soilbio.2013.10.003
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发表时间：
2014-01-01
影响因子：
9.7
通讯作者：
Koegel-Knabner, Ingrid
中科院分区：
文献类型：
--
作者：
Bimueller, Carolin;Dannenmann, Michael;Koegel-Knabner, Ingrid
由于中欧的气候变化，预计夏季将出现长期干旱。由此导致的土壤水分有效性降低可能导致土壤过程速率的改变，如土壤有机质组分之间的氮分配和土壤内部的稳定。为了研究气候变化引起的干旱对土壤有机质组分氮分布和氮稳定的影响，我们进行了时空气候变化实验。我们从德国南部一个西北暴露的山坡转移了一个完整的Rendzic Leptosol的植物微生物中生态系统，该斜坡具有凉爽潮湿的小气候，穿过狭窄的山谷，西南暴露的山坡具有温暖干燥的小气候，这反映了预测的未来气候条件。在同一原始区域内，对朝西北的斜坡也进行了控制转移。我们将使用硝酸铵的均匀N-15标记方法与物理分馏程序和化学土壤提取方案相结合。我们的目的是跟踪N-15在不同土壤有机质组分中的分配，即轻组分、有机矿物组分和可提取土壤组分，包括微生物生物量、铵态氮、硝酸盐和溶解有机氮。在不到一个生长季节的时间里，我们观察到与夏季干燥条件相关的不同土壤组分之间无机N-15的分配发生了变化，干旱条件下氮周转减弱，因此相对不稳定的轻质组分中N-15浓度显著升高。我们将这种效应归因于矿化固定周转的减速。我们得出结论，长时间的夏季干旱可能会改变稳定动力学，因为微生物的不活动可能会减少氮向稳定途径的转移。有机-矿物组合的迟滞稳定增加了极端降雨事件中氮损失的风险，根据中欧未来气候变化情景预测，极端降雨事件在21世纪将增加(C) 2013 Elsevier Ltd.。版权所有。
Prolonged summer droughts are projected to occur as a consequence of climate change in Central Europe. The resulting reduced soil water availability may lead to alterations in rates of soil processes such as nitrogen partitioning among soil organic matter fractions and stabilization within soil. To study the effect of climate change-induced drought on (1) the distribution of nitrogen among soil organic matter fractions and (2) nitrogen stabilization, we performed a space-for-time climate change experiment. We transferred intact plant soil microbe mesocosms of a Rendzic Leptosol with a young beech tree from a slope with northwestern exposure in southern Germany characterized by a cool-moist microclimate across a narrow valley to a slope with southwestern exposure with a warm-dry microclimate, which reflects projected future climatic conditions. A control transfer was also done on the northwest-facing slope within the same area of origin. We combined a homogenous N-15 labeling approach using ammonium nitrate with a physical fractionation procedure and chemical soil extraction protocols. Our aim was to follow the partitioning of N-15 in different soil organic matter fractions, i.e. light fractions, organo-mineral fractions, and extractable soil fractions including microbial biomass, ammonium, nitrate, and dissolved organic nitrogen. Within less than one growing season, we observed a modified partitioning of recently applied inorganic N-15 between different soil fractions in relation to drier summer conditions, with attenuated nitrogen turnover under drought and consequently significantly higher N-15 concentrations in the relatively labile light fractions. We ascribed this effect to a decelerated mineralization immobilization turnover. We conclude that prolonged summer droughts may alter the stabilization dynamics because the induced inactivity of microorganisms may reduce the transfer of nitrogen to stabilization pathways. A retarded stabilization in organo-mineral associations enhances the risk of nitrogen losses during extreme rainfall events, which are projected to increase in the 21st century predicted by future climate change scenarios for Central Europe (C) 2013 Elsevier Ltd. All rights reserved.