U. S. Geological Survey, New England Water Science Center, 196 Whitten Rd., Augusta, Maine 04330, USA.
U. S. Geological Survey, New England Water Science Center, 87 State Street, Montpelier, VT 05602, USA.
Sci Total Environ. 2022 Oct 20;844:156954. doi: 10.1016/j.scitotenv.2022.156954. Epub 2022 Jun 26.
The production, mobilization and fluvial transport of dissolved organic carbon (DOC) in temperate forests are important components of the carbon cycle that are influenced by ongoing changes in climate. Numerous studies have reported temporal trends in stream water DOC concentrations and have attributed changes in concentrations to climatic and hydrologic variables. Fewer studies have reported trends in concentration-discharge (C-Q) relations for DOC. The goal of this study was to detect and quantify changes in DOC concentration and slope of the C-Q relation from 1991 to 2018 in an intensively sampled forested research watershed in northern Vermont. Stream water DOC concentration and slope of the C-Q relation increased over time as did precipitation, stream discharge, and air temperature. The increases in DOC concentration and slope of the C-Q were substantially greater in the summer and fall (autumn) than in winter and spring. The largest increases in the magnitude of C-Q slopes occurred in the December, October and September. The increases in slope of the C-Q relation in summer and fall were larger for baseflow than for storm flow. The increases in DOC concentration and slope of the C-Q relation over time may be related to increasing temperature, longer growing seasons, and associated increases in production and microbial decomposition of soil organic matter that supplies DOC for mobilization to streams. The results suggest that in a changing climate, C-Q relations may not necessarily be stationary and therefore analyses that attempt to estimate future DOC concentrations and loads should consider potentially changing C-Q relations over time.
在温带森林中，溶解有机碳（DOC）的产生、迁移和河流输运是碳循环的重要组成部分，受气候变化的影响。许多研究报告了溪流水中 DOC 浓度的时间趋势，并将浓度变化归因于气候和水文变量。较少的研究报告了浓度-流量（C-Q）关系中 DOC 的趋势。本研究的目的是检测和量化 1991 年至 2018 年在佛蒙特州北部一个密集采样的森林研究流域中 DOC 浓度和 C-Q 关系斜率的变化。随着降水、河流流量和空气温度的增加，溪流水中的 DOC 浓度和 C-Q 关系的斜率也随之增加。DOC 浓度和 C-Q 关系斜率的增加在夏季和秋季（秋季）明显大于冬季和春季。C-Q 斜率幅度的最大增加发生在 12 月、10 月和 9 月。夏季和秋季基流的 C-Q 关系斜率增加大于暴雨流。随着时间的推移，DOC 浓度和 C-Q 关系斜率的增加可能与温度升高、生长季节延长以及与土壤有机质生产和微生物分解相关的增加有关，这些有机质为向溪流输送的迁移提供了 DOC。研究结果表明，在气候变化的情况下，C-Q 关系不一定是固定的，因此试图估计未来 DOC 浓度和负荷的分析应考虑随时间变化的潜在变化的 C-Q 关系。
