Ecosystem type differences in nitrogen process rates and controls in the riparian zone of a montane landscape
Ecosystem type differences in nitrogen process rates and controls in the riparian zone of a montane landscape
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DOI：
10.1016/j.foreco.2005.10.001
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发表时间：
2006-02
影响因子：
3.7
通讯作者：
Amy Merrill;T. Benning
中科院分区：
文献类型：
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作者：
Amy Merrill;T. Benning
在过去的100年里，世界水生生态系统的氮(N)投入有所增加。众所周知，河岸地带和其他湿地在进入湖泊和溪流之前，会从地下水和地表水中去除氮。然而，河岸湿地对水质的影响已被证明在不同的地点有很大的不同。河岸带N动态景观变化的来源一直没有得到很好的记录，也很少被量化。在太浩湖流域(LTB)内，我们假设河岸N动态的差异与生态系统类型的差异相关。为了验证这一假设，我们在太浩湖的一条支流上随机选择了20个地块，每个地块有5种生态系统类型。在整个无雪季节，我们测量了每个地块的土壤氮素转化和地下水化学。结果表明，不同生态系统类型间的反硝化潜力、净矿化量、净硝化作用和地下水养分通量存在显著差异。这些结果表明，将河岸带划分为生态系统类型可能有助于预测河岸水质影响的景观差异。我们还利用在每个研究地点收集的数据，测试了预期直接和间接控制河岸N处理速率的因素。通过相关分析和多元回归分析发现，不同生态系统类型的氮素处理速率与不同控制因子的相关性最强。不同生态系统类型之间直接和间接控制因素的差异表明，通过将河岸带分层为生态系统类型，而不是将其视为分水岭的单一、同质部分，可能是最准确地建立河岸过程的机械性、地貌模型。
Nitrogen (N) inputs to the world's aquatic ecosystems have increased over the past 100 years. Riparian zones and other wetlands are known to remove N from ground and surface waters before they enter lakes and streams. However, the effect of riparian wetlands on water quality has been shown to differ dramatically among sites. Sources of landscape variation in riparian N dynamics have been poorly documented and rarely quantified. Within the Lake Tahoe Basin (LTB), we hypothesized that differences in riparian N dynamics correlate to differences in ecosystem type. To test this hypothesis, we randomly selected 20 plots, four each of five ecosystem types, along a tributary to Lake Tahoe. Throughout the snow-free season, we measured soil N transformations and groundwater chemistry in each plot. We found significant differences in denitrification potential, net mineralization, net nitrification and groundwater nutrient flux among different ecosystem types. These results suggest that classification of riparian zones into ecosystem types might be useful in predicting landscape differences in riparian water quality effects. We also tested for factors expected to directly and indirectly control riparian N process rates using data collected at each study site. Using correlation and multiple regression analysis, we found that N process rates were most highly correlated with different control factors according to ecosystem type. Differences in direct and indirect control factors among ecosystem types indicate that construction of mechanistic, landscape models of riparian processes might be most accurately done by stratifying the riparian zone into ecosystem types rather than by viewing it as a single, homogeneous part of the watershed.