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.本项目的核心目标在于阐明长期气候变率（climate variability）对荒漠溪流（desert streams）结构与功能的影响机制。在干旱景观（arid landscapes）中，气候与水文（hydrology）存在紧密的耦合关系；正因如此，荒漠溪流成为观测与解析气候变率及方向性变化所引发后果的理想研究对象。干旱区域的典型特征为降水年际变率显著，此类气候格局主导了荒漠溪流生态系统的整体干扰制度（disturbance regime，以洪水与干涸为核心表现形式）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频次与规模，决定了周边集水区（catchment）向溪流输送的营养物总量，同时也会塑造溪流-河岸带（stream-riparian corridor）的生物地貌（biogeomorphic）结构。嵌入这十年尺度的水文格局之中，山洪（flash floods）会冲刷河道，并在短时间尺度（即一年以内）触发底栖藻类（benthic algae）与大型无脊椎动物（macroinvertebrates）的一系列快速演替变化（successional changes）。本研究的一项重要目标是厘清离散扰动后的恢复过程如何受到溪流营养状态与河道结构的共同调控，进而更好地理解长期气候变率与气候变化如何调节荒漠溪流生态系统所特有的慢速过程（生物地貌变化）与快速过程（洪水后演替）及其各要素间的相互作用。