Dynamic lateral, vertical, and longitudinal hydrologic connectivity drive runoff and carbon export across watershed scales

Dynamic Connectivity in the Landscape
Chair: Adam Ward (Indiana University)
Connectivity between different locations on the landscape is defined by the movement of water, solutes, energy, and organisms. The magnitude and persistence of connections is critical to prediction of ecological functions, many of which are mediated by hydrological stores and fluxes. In this session we consider connectivity as a spatially and temporally variable process in catchments and river systems.

"Dynamic lateral, vertical, and longitudinal hydrologic connectivity drive runoff and carbon export across watershed scales"
Speaker: Margaret Zimmer (University of California Santa Cruz)

The influence of temporally dynamic lateral, vertical, and longitudinal connectivity of runoff source areas on hydrologic and biogeochemical fluxes across watershed scales is poorly understood. To address this, we monitored the timing, magnitude and chemical composition of precipitation, runoff, and runoff-generating flow paths in nested 3.3 and 48.4 ha watersheds (North Carolina, USA). These watersheds are comprised of ephemeral and intermittent runoff-producing headwaters and perennial runoff-producing lowlands. We monitored the active surface drainage network, which reflected connectivity to, and contributions from, runoff source areas that shifted within baseflow and stormflow conditions. The overall importance of deeper, baseflow-associated and shallower, stormflow-activated source area contributions varied across watershed scales and influenced dissolved organic carbon (DOC) export. The dominant temporal variability of in-stream DOC was driven by frequent event-based flushing of shallow soil zones and annual replenishment. Our findings suggest that hydro-biogeochemical signals at larger watershed outlets can be driven by the expansion, contraction, and connection of lateral, longitudinal, and vertical source areas that reflect distinct runoff generation processes.

景观动态连通性

主持人：Adam Ward（印第安纳大学）

景观中不同地点之间的连通性由水、溶质、能量和生物体的运动所定义。连接的强度和持久性对于预测生态功能至关重要，其中许多功能是通过水文储存和通量进行介导的。在本次会议中，我们将连通性视为一个在流域和河流系统中具有空间和时间变异性过程。

“动态的横向、垂直和纵向水文连通性驱动了流域尺度上的径流和碳输出”
演讲者：Margaret Zimmer（加州大学圣克鲁兹分校）

对于时变性的横向、垂直和纵向连通性对流域尺度上的水文和生物地球化学通量的影响，我们了解甚少。为了解决这一问题，我们在美国北卡罗来纳州嵌套的3.3和48.4公顷的流域中（包括暂时性和间歇性的径流产生源头以及永久性的径流产生低地）监测了降水、径流和径流产生路径的时间、强度和化学组成。我们监测了活跃的地面排水网络，它反映了在基流和暴雨流条件下，径流源头区域的连通性和贡献。在流域尺度上，更深层次的、与基流相关的和较浅的、由暴雨流激活的源头区域的总体贡献的重要性各异，并影响了溶解有机碳（DOC）的输出。河流中DOC的时空变异性主要由浅层土壤区的频繁事件性冲洗和年度补充所驱动。我们的研究结果指出，较大流域出口处的氢生物地球化学信号可能是由横向、纵向和垂直源头区域的扩张、收缩和连接所驱动，这些连接反映了不同的径流产生过程。