Nitrogen availability in a grazed semi-arid grassland is dominated by seasonal rainfall
Nitrogen availability in a grazed semi-arid grassland is dominated by seasonal rainfall
复制标题
放牧的半干旱草原的氮素可用性主要由季节性降雨量决定
DOI：
10.1007/s11104-010-0509-9
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发表时间：
2011-03-01
期刊：
影响因子：
4.9
通讯作者：
Brueck, Holger
中科院分区：
文献类型：
--
作者：
Giese, Marcus;Gao, Ying Zhi;Brueck, Holger
在半干旱草地生态系统中，土壤生物地球化学过程受季节和年际降雨变化和温度的控制，这可能超越了放牧动物对氮有效性和氮动态的长期影响。在一项为期三年（2004-2006）的内蒙古草原案例研究中，我们分析了三个不同放牧强度地点的时间集成（离子交换树脂）和瞬时（土壤矿物氮提取）无机氮有效性，并将这些数据与土壤含水量（SWC）、地上净初级生产力（ANPP）和植物氮吸收信息相结合。此外，还考虑了降雨和放牧对氮素有效度（NO3——N、NH4+-N）的影响。放牧对氮素有效性的影响较小。其中一个研究年份（2004年）显示放牧效应，未放牧地的树脂n有效性高于重度放牧地。无机氮有效性在最干旱年份（2005年）较低，在平均降雨量和分布有利年份（2004年）最高。总体而言，我们发现无机氮有效性与植物生产力和植物氮吸收量呈正相关。降雨对植物有效NO3——N和NH4+-N库也有控制作用；低SWC时，有效无机N形态以NH4+-N为主，有效NO3——N随SWC增加而增加。我们观察到氮的有效性和植物生产力在时间上是同步的。影响SWC的降雨变率和土地利用方式的增加可能会改变N有效性动态（以及N形态的关系），从而改变半干旱天然草地碳氮循环的重要过程。
In semi-arid grassland ecosystems, soil biogeochemical processes are controlled by seasonal and inter-annual rainfall variation and temperature, which may override the long-term impact of grazers on N availability and N dynamics. In a three-year (2004-2006) case study of an Inner Mongolian grassland, we analysed time-integrated (ion-exchange resins) and instantaneous (soil mineral N extractions) inorganic N availability at three sites of varying grazing intensities and combined these data with information on soil water content (SWC), aboveground net primary productivity (ANPP) and plant N uptake. Additionally, the effects of rainfall and grazing on N-form availability (NO3--N, NH4+-N) were considered. Grazing had less impact on N availability compared to seasonal and annual rainfall distribution. One of the three study years (2004) showed a grazing effect with higher resin-N availability at the ungrazed site compared to the heavily grazed site. Inorganic N availability was low in the driest year (2005) and highest in a year of average rainfall amount and favourable distribution (2004). In general, we found a positive relationship between inorganic N availability and both plant productivity and plant N uptake. Rainfall also controlled the plant available NO3--N and NH4+-N pools; NH4+-N dominated the available inorganic N-form in times of low SWC, while the available NO3--N increased with SWC. We observed N availability and plant productivity in a temporal synchronized pattern. Increased rainfall variability and land-use practices affecting SWC will likely alter N availability dynamics (and the relation of N-forms) and, therefore, important processes of semi-arid natural grassland carbon and N cycling.