Macroinvertebrate collections following floods in Sycamore Creek, Arizona, USA 1985-1999

The primary objective of this project is to understand how long-term climate variability influences the structure and function of desert streams. Climate and hydrology are intimately linked in arid landscapes; for this reason, desert streams are particularly well suited for both observing and understanding the consequences of climate variability and directional change. Arid regions are characterized by high interannual variation in precipitation, and these climate patterns drive the overall disturbance regime (in terms of flooding and drying) and nutrient status of desert stream ecosystems. At long time scales, the number and size of floods in a given year or cluster of years dictate nutrient delivery to streams from the surrounding catchment, and also influence the biogeomorphic structure of the stream-riparian corridor. Embedded within this decadal-scale hydrologic regime, flash floods scour stream channels and initiate a series of rapid successional changes by benthic algae and macroinvertebrates at short time scales (i.e., within a year). An important goal of this research is to determine how recovery following discrete events is influenced by both stream nutrient status and channel structure and to thus better understand how long-term climate variability and change guide the interactions among slow (biogeomorphic change) and fast (post-flood succession) features and processes characteristic of desert stream ecosystems.本研究项目的核心目标，在于揭示长期气候变异性如何调控荒漠溪流（desert streams）的结构与功能。在干旱景观中，气候与水文过程紧密耦合；正因如此，荒漠溪流成为观测并解析气候变异性与方向性变化所产生影响的理想研究对象。干旱区域的降水具有显著的年际波动特征，这类气候格局主导了荒漠溪流生态系统的整体干扰制度（以洪水与干涸为表现形式）与营养状态。在长期时间尺度下，单一年份或连续数年的洪水数量与规模，既决定了周边集水区向溪流输送的营养物质总量，也会影响溪流-河岸带（stream-riparian corridor）的生物地貌结构。嵌入这十年尺度水文制度中的突发洪水（flash floods），会冲刷溪流河道，并在短时间尺度（即一年内）触发底栖藻类（benthic algae）与大型无脊椎动物（macroinvertebrates）的快速演替过程。本研究的另一重要目标，是明确离散扰动事件后的生态恢复过程如何受到溪流营养状态与河道结构的共同调控，并借此进一步阐明长期气候变异性与气候变化如何调控荒漠溪流生态系统中两类典型特征与过程的相互作用：一类是缓慢的生物地貌变化（biogeomorphic change），另一类是快速的洪水后演替（post-flood succession）。