Spatial controls on dissolved organic carbon in upland waters inferred from a simple statistical model
Spatial controls on dissolved organic carbon in upland waters inferred from a simple statistical model
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DOI：
10.1007/s10533-015-0071-x
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发表时间：
2015-02
期刊：
影响因子：
4
通讯作者：
D. Monteith;P. Henrys;C. Evans;I. Malcolm;E. Shilland;M. Pereira
中科院分区：
文献类型：
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作者：
D. Monteith;P. Henrys;C. Evans;I. Malcolm;E. Shilland;M. Pereira
在北半球许多工业化地区的高地地表水中，溶解有机碳（DOC）的浓度达到了人们记忆中最高的水平，引发了对其“自然性”的争论。由于对饮用水处理和供应的影响，人们越来越关注通过地方土地管理减轻影响的可能性，以及预测环境变化可能产生的影响。然而，对DOC生产的主要控制仍未解决，阻碍了为特定地点建立适当的参考水平。本文通过一个简单的多元逻辑回归模型，证明了英国高地流域长期平均DOC水平的空间变化是高度可预测的，该模型包括湿地土壤覆盖、降雨量、海拔、流域对酸化的敏感性和当前的酸沉降。DOC浓度与海拔高度呈负相关，对于有机-矿物土壤为主的集水区，这种负相关似乎可以用变化的净初级生产量和温度依赖分解的综合效应来解释。然而，对于湿地覆盖比例高的集水区，海拔高度的影响程度要大得多，这表明其他控制因素会影响这些地点，如湿土壤中碳的呼吸损失受阻和/或对低海拔地区水位下降的敏感性增加。该模型表明：(1)对酸敏感的有机-矿质土壤上硫沉降的持续减少，将推动DOC进一步显著增加；(2)考虑到观测到的高度-DOC关系的大小差异，泥炭为主土壤的集水区产生的DOC可能比以矿质土壤为主的集水区对气候变化更敏感。然而，由于机制尚不清楚，后者值得进一步调查。
Dissolved organic carbon (DOC) concentrations in upland surface waters in many northern hemisphere industrialised regions are at their highest in living memory, provoking debate over their “naturalness”. Because of the implications for drinking water treatment and supply there is increasing interest in the potential for mitigation through local land management, and for forecasting the likely impact of environmental change. However, the dominant controls on DOC production remain unresolved, hindering the establishment of appropriate reference levels for specific locations. Here we demonstrate that spatial variation in long-term average DOC levels draining upland UK catchments is highly predictable using a simple multiple logistic regression model comprising variables representing wetland soil cover, rainfall, altitude, catchment sensitivity to acidification and current acid deposition. A negative relationship was observed between DOC concentration and altitude that, for catchments dominated by organo-mineral soils, is plausibly explained by the combined effects of changing net primary production and temperature-dependent decomposition. However, the magnitude of the altitude effect was considerably greater for catchments with a high proportion of wetland cover, suggesting that additional controls influence these sites such as impeded respiratory loss of carbon in wet soils and/or an increased susceptibility to water level drawdown at lower altitudes. The model suggests (1) that continuing reductions in sulphur deposition on acid sensitive organo-mineral soils, will drive further significant increases in DOC and, (2) given the differences in the magnitude of the observed altitude-DOC relationships, that DOC production from catchments with peat-dominated soils may be more sensitive to climate change than those dominated by mineral soils. However, given that mechanisms remain unclear, the latter warrants further investigation.