Clark Joanna M, Lane Stuart N, Chapman Pippa J, Adamson John K
Earth and Biosphere Institute, School of Geography, University of Leeds, Woodhouse Lane, Leeds, UK.
Sci Total Environ. 2008 Oct 15;404(2-3):308-15. doi: 10.1016/j.scitotenv.2007.11.002. Epub 2008 Feb 20.
Hydrologic transport of dissolved organic carbon (DOC) from peat soils may differ to organo-mineral soils in how they responded to changes in flow, because of differences in soil profile and hydrology. In well-drained organo-mineral soils, low flow is through the lower mineral layer where DOC is absorbed and high flow is through the upper organic layer where DOC is produced. DOC concentrations in streams draining organo-mineral soils typically increase with flow. In saturated peat soils, both high and low flows are through an organic layer where DOC is produced. Therefore, DOC in stream water draining peat may not increase in response to changes in flow as there is no switch in flow path between a mineral and organic layer. To verify this, we conducted a high-resolution monitoring study of soil and stream water at an upland peat catchment in northern England. Our data showed a strong positive correlation between DOC concentrations at -1 and -5 cm depth and stream water, and weaker correlations between concentrations at -20 to -50 cm depth and stream water. Although near surface organic material appears to be the key source of stream water DOC in both peat and organo-mineral soils, we observed a negative correlation between stream flow and DOC concentrations instead of a positive correlation as DOC released from organic layers during low and high flow was diluted by rainfall. The differences in DOC transport processes between peat and organo-mineral soils have different implications for our understanding of long-term changes in DOC exports. While increased rainfall may cause an increase in DOC flux from peat due to an increase in water volume, it may cause a decrease in concentrations. This response is contrary to expected changes in DOC exports from organo-mineral soils, where increase rainfall is likely to result in an increase in flux and concentration.
由于土壤剖面和水文条件的差异，泥炭土中溶解有机碳（DOC）的水文传输在对流量变化的响应方式上可能与有机矿物土不同。在排水良好的有机矿物土中，低流量通过下层矿质层，DOC在该层被吸收，高流量通过上层有机层，DOC在该层产生。流经有机矿物土的溪流中DOC浓度通常随流量增加。在饱和泥炭土中，高流量和低流量都通过产生DOC的有机层。因此，流经泥炭的溪水中的DOC可能不会因流量变化而增加，因为在矿质层和有机层之间没有流量路径的切换。为了验证这一点，我们在英格兰北部的一个高地泥炭集水区进行了一项土壤和溪水的高分辨率监测研究。我们的数据显示，-1厘米和-5厘米深度处的DOC浓度与溪水之间存在很强的正相关，而-20厘米至-50厘米深度处的浓度与溪水之间的相关性较弱。尽管近地表有机物质似乎是泥炭土和有机矿物土中溪水DOC的关键来源，但我们观察到溪流流量与DOC浓度之间呈负相关，而不是正相关，因为在低流量和高流量期间从有机层释放的DOC被降雨稀释了。泥炭土和有机矿物土之间DOC传输过程的差异对我们理解DOC输出的长期变化有不同的影响。虽然降雨增加可能会因水量增加而导致泥炭中DOC通量增加，但可能会导致浓度降低。这种响应与有机矿物土中DOC输出的预期变化相反，在有机矿物土中，降雨增加可能会导致通量和浓度增加。
