Hot spots and hot moments of carbon and nitrogen dynamics in a semiarid riparian zone
Hot spots and hot moments of carbon and nitrogen dynamics in a semiarid riparian zone
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DOI：
10.1029/2007jg000588
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发表时间：
2008-03
影响因子：
--
通讯作者：
T. Harms;N. Grimm
中科院分区：
文献类型：
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作者：
T. Harms;N. Grimm
[1]河岸生态系统的特点是在物理和生物属性的时空异质性，与营养循环的后果。我们调查了碳（C）和氮（N）循环过程的水文地貌模板在圣佩德罗河，亚利桑那州，一个大的（集水面积约11,500平方公里），自由流动，半干旱河流的河岸带的响应。在一年的时间内，我们记录了土壤，浅层地下水，和流营养化学的空间和时间模式，以及在土壤的表面（0-17厘米）和季节性饱和区（ROSS）的N-转化过程的速率。一个炎热的时刻，氮的保留和去除表明在夏季季风季节的微生物过程的速率升高。与此同时，RoSS表层土壤和土壤的土壤微生物量均观察到碳含量升高。土壤微生物的C-使用配置文件的分析，再加上在流和浅层地下水化学的趋势，进一步表明，这一热点的N去除是由新的可用的，不稳定的有机材料。在空间背景下，斑块在土壤资源，微生物生物量，和潜在的反硝化作用的微地形变化最好的解释;低海拔景观位置的热点资源的可用性和微生物活性。垂直异质性也对应于影响氮转化率的因素的变化。有机质是一个更频繁的显着因素，解释氮转化率在ROSS土壤，而土壤含水量往往是更重要的表层土壤。总之，这些模式表明，了解水文地貌模板上的点，在空间和时间上，将水和不稳定的有机物聚集在一起，将导致更大的预测能力，在半干旱河流河岸走廊的C和N循环。
[1] Riparian ecosystems are characterized by spatial and temporal heterogeneity in physical and biological attributes, with consequences for nutrient cycling. We investigated the responses of carbon (C) and nitrogen (N) cycling processes to the hydrogeomorphic template in the riparian zone of the San Pedro River, Arizona, a large (catchment area ∼11,500 km2), free-flowing, semiarid river. Over an annual period we documented spatial and temporal patterns in soil, shallow groundwater, and stream nutrient chemistry as well as rates of N-transforming processes in soils of the surface (0–17 cm) and region of seasonal saturation (RoSS). A hot moment of N retention and removal was indicated by elevated rates of microbial processes during the summer monsoon season. At the same time, elevated C was observed in soil microbial biomass for both surface soils and soils in the RoSS. Analyses of C-use profiles for soil microbes, coupled with trends in stream and shallow-groundwater chemistry, further suggest that this hot moment of N removal was fueled by newly available, labile organic material. In a spatial context, patchiness in soil resources, microbial biomass, and potential denitrification were best explained by variation in microtopography; low-elevation landscape positions were hot spots of resource availability and microbial activity. Vertical heterogeneity also corresponded with variation in the factors influencing N transformation rates. Organic matter was more frequently a significant factor explaining N transformation rates in RoSS soils whereas soil water content was more often important in surface soils. Together, these patterns suggest that understanding the points on the hydrogeomorphic template, both in space and in time, that bring together water and labile organic matter will lead to greater predictive capability regarding C and N cycling in semiarid river-riparian corridors.