Geography, College of Life and Environmental Sciences, Amory Building, Rennes Drive, Exeter, Devon EX4 4RJ, United Kingdom.
Sci Total Environ. 2014 Apr 1;476-477:643-56. doi: 10.1016/j.scitotenv.2014.01.057. Epub 2014 Feb 4.
The export of total organic carbon (particulate and dissolved) from terrestrial to aquatic ecosystems has important implications for water quality and the global carbon cycle. However, most research to date has focused on DOC losses from either forested or peaty catchments, with only limited studies examining the controls and rates of total fluvial carbon losses from agricultural catchments, particularly during storm events. This study examined the controls and fluxes of total suspended sediment (SS), total particulate (TPC) and dissolved organic carbon (DOC) from two adjacent catchments with contrasting intensive agricultural and semi-natural land-use. Data from 35 individual storm events showed that the agricultural catchment exported significantly higher SS concentrations on a storm-by-storm basis than the semi-natural catchment, with peak discharge exerting a greater control over SS, TPC and DOC concentrations. Baseflow DOC concentrations in the agricultural catchment were significantly higher. DOC quality monitored during one simultaneous rainfall event differed between the two study catchments, with more humic, higher molecular weight compounds prevailing in the agricultural catchment and lower molecular weight compounds prevailing in the semi-natural catchment. During an eight month period for which a comparable continuous turbidity record was available, the estimated SS yields from the agricultural catchment were higher than from the semi-natural catchment. Further, the agricultural catchment exported proportionally more TPC and a comparable amount of DOC, despite a lower total soil carbon pool. These results suggest that altered hydrological and biogeochemical processes within the agricultural catchment, including accelerated soil erosion and soil organic matter turnover, contributed to an enhanced fluvial SS and carbon export. Thus, we argue that enhancing semi-natural vegetation within intensively farmed catchments could reduce sediment and carbon losses from these areas and increase their resilience to more extreme hydrological events, anticipated as a result of climate change.
从陆地生态系统向水生生态系统输出的总有机碳（颗粒态和溶解态）对水质和全球碳循环有重要影响。然而，迄今为止，大多数研究都集中在森林或泥炭地流域的 DOC 损失上，只有有限的研究考察了农业流域总河流碳损失的控制因素和速率，特别是在风暴事件期间。本研究考察了两个相邻流域的总悬浮物（SS）、总颗粒态（TPC）和溶解有机碳（DOC）的控制因素和通量，这两个流域具有不同的集约化农业和半自然土地利用。来自 35 个单独风暴事件的数据表明，农业流域的 SS 浓度在风暴基础上明显高于半自然流域，峰值流量对 SS、TPC 和 DOC 浓度的控制作用更大。农业流域的基流 DOC 浓度明显较高。在一次同时降雨事件中监测到的 DOC 质量在两个研究流域之间存在差异，农业流域中存在更多的腐殖质、高分子量化合物，而半自然流域中则存在更多的低分子量化合物。在可以获得可比连续浊度记录的八个月期间，农业流域的 SS 产率高于半自然流域。此外，尽管农业流域的总土壤碳库较低，但该流域输出的 TPC 比例更高，DOC 量相当。这些结果表明，农业流域内改变的水文和生物地球化学过程，包括加速土壤侵蚀和土壤有机质周转，导致了增强的河流 SS 和碳输出。因此，我们认为，在集约化耕作的流域中增加半自然植被可以减少这些地区的泥沙和碳损失，并提高它们对气候变化预期的更极端水文事件的恢复力。
