Department of Physical Geography and Ecosystem Science, Lund University, Lund, Skåne, Sweden.
GIS Centre, Lund University, Lund, Skåne, Sweden.
PLoS One. 2018 Jul 6;13(7):e0199608. doi: 10.1371/journal.pone.0199608. eCollection 2018.
Climate change projections show that temperature and precipitation increases can alter the exchange of greenhouse gases between the atmosphere and high latitude landscapes, including their freshwaters. Dissolved organic carbon (DOC) plays an important role in greenhouse gas emissions, but the impact of catchment productivity on DOC release to subarctic waters remains poorly known, especially at regional scales. We test the hypothesis that increased terrestrial productivity, as indicated by the normalized difference vegetation index (NDVI), generates higher stream DOC concentrations in the Stordalen catchment in subarctic Sweden. Furthermore, we aimed to determine the degree to which other generic catchment properties (elevation, slope) explain DOC concentration, and whether or not land cover variables representing the local vegetation type (e.g., mire, forest) need to be included to obtain adequate predictive models for DOC delivered into rivers. We show that the land cover type, especially the proportion of mire, played a dominant role in the catchment's release of DOC, while NDVI, slope, and elevation were supporting predictor variables. The NDVI as a single predictor showed weak and inconsistent relationships to DOC concentrations in recipient waters, yet NDVI was a significant positive regulator of DOC in multiple regression models that included land cover variables. Our study illustrates that vegetation type exerts primary control in DOC regulation in Stordalen, while productivity (NDVI) is of secondary importance. Thus, predictive multiple linear regression models for DOC can be utilized combining these different types of explanatory variables.
气候变化预测表明，温度和降水的增加会改变大气与高纬度景观（包括其淡水）之间温室气体的交换。溶解有机碳（DOC）在温室气体排放中起着重要作用，但流域生产力对亚北极水域 DOC 释放的影响仍知之甚少，特别是在区域尺度上。我们检验了以下假设，即在亚北极瑞典的 Stordalen 流域，归一化差异植被指数（NDVI）指示的陆地生产力增加会导致溪流中更高的 DOC 浓度。此外，我们旨在确定其他通用流域属性（海拔、坡度）在多大程度上解释了 DOC 浓度，以及是否需要包含代表当地植被类型的土地覆盖变量（例如，沼泽、森林），以获得对输送到河流中的 DOC 进行充分预测的模型。我们表明，土地覆盖类型，特别是沼泽的比例，在流域释放 DOC 方面起着主导作用，而 NDVI、坡度和海拔则是支持性的预测变量。NDVI 作为单一预测因子与受纳水体中 DOC 浓度的关系微弱且不一致，但在包括土地覆盖变量的多元回归模型中，NDVI 是 DOC 的重要正向调节剂。我们的研究表明，在 Stordalen，植被类型对 DOC 调节具有主要控制作用，而生产力（NDVI）则是次要的。因此，可以利用这些不同类型的解释变量来组合使用预测多元线性回归模型。
