The influence of major FLOOD disturbance on River EcoSystem Evolution Trajectories in recently deglaciated terrain (FLOODRESET)

影响河流生态系统的主要因素之一是干扰，特别是与洪水有关的干扰。洪水维持了生态系统的多样性，并重新分配了河流中的能量、养分、沉积物和生物群。河流的生物群（如无脊椎动物和鱼类）可以通过抵抗干扰（抵抗力）或迅速恢复（复原力）而在洪水中幸存下来。虽然对严重洪水对河流生态系统的干扰已经有了比较充分的研究，但许多研究只有有限的干扰前系列数据来评估洪水影响，很少考虑其演替发展。这在一定程度上反映了对河流群落进行连续的、按年的监测以衡量任何干扰影响的最小程度。2005年11月21日至26日，一场强烈的冬季风暴伴随着大风和创纪录的降雨，在阿拉斯加东南部造成了广泛的洪水、山体滑坡和风力破坏。朱诺市、海恩斯市和锡特卡市发布了当地的灾难声明，并请求州政府和公众协助应对和恢复。阿拉斯加东南部的冰川湾地区出现了持续的强降雨（在不到72小时内超过650毫米），导致大规模洪水和许多河流受到极端干扰。与年平均降雨量920毫米相比，这一事件的规模显而易见。在冰川湾，我们持有长期连续的数据集（一些河流长达29年），详细描述了冰川退缩后河流群落的演变。该数据集为研究河流无脊椎动物和鱼类的主要演替（随时间变化）提供了独特的见解。其中一条小溪（Wolf Point Creek； WPC）自1977年以来已经形成了非常详细的群落变化轨迹，显示了这条小溪是如何从一个由少数Chironomidae物种主导的河流进化到最近（2005年）一个包含多种无脊椎动物（昆虫/非昆虫）和幼年鲑鱼的群落的。然而，在2006年6月初对冰川湾的短暂访问中，我们观察到许多河流（包括WPC）受到洪水的严重影响，河道形态发生了明显的重大变化。这种干扰很可能对这些溪流的生物群落产生了重大影响。主要研究方向为：(1)洪水对不同年龄河流栖息地和形态的影响；(2)洪水对Wolf Point Creek主要演替框架（无脊椎动物、鱼类）的影响；(3)洪水对不同年龄河流的影响，以提供不同演替发展阶段的河流如何响应洪水的信息；(4)通过河道边实验，研究抗/弹性无脊椎动物是否会改变河流生物群落的后续演替轨迹。本研究将评估这些主要洪水干扰对河流无脊椎动物和鱼类的主要演替轨迹的影响，并确定持久的分类群。至关重要的是，我们要尽快调查洪水对生物群落的影响，因为随着群落的恢复，整个夏天可能会发生重新定植和演替。我们的目标是评估未来13个月的复苏轨迹，以确定是否会完全复苏。由于洪水，一些无脊椎动物可能已经从河流中消失了，由于存在山脉和大片冰原等分散障碍，这些物种可能需要很长时间才能回归。研究结果将从群落持久性（存在/缺失的恒常性）和组成稳定性（分类群相对丰度的恒常性）两个方面来解释，即赋予分类群抵抗力和恢复力的特征以及提供更多避难所的栖息地复杂性。

One of the major factors influencing river ecosystems is disturbance, particularly that related to flooding. Floods maintain ecosystem diversity and redistribute energy, nutrients, sediment and biota in rivers. The biota of rivers (e.g. invertebrates and fish) may survive floods either by withstanding the disturbance (resistance) or recovering rapidly (resilience). Although disturbance to river ecosystems due to severe flooding have been relatively well studied, many studies have a restricted pre-disturbance series of data against which to evaluate flood effects and rarely in terms of their successional development. This in part reflects minimal continuous, year-on-year monitoring of stream communities against which to measure any disturbance effects. Between November 21 and 26 of 2005, a strong winter storm with high winds and record rainfall caused widespread flooding, landslides, and wind damage in southeast Alaska. The cities of Juneau, Haines, and Sitka made local disaster declarations and requested state and public assistance for response and recovery. Continuous heavy rainfall (over 650mm in less than 72 hours) occurred over a region called Glacier Bay in southeast Alaska, leading to large scale flooding and extreme disturbance to many rivers. The size of this event is evident when compared against an average annual rainfall of 920mm. In Glacier Bay, we hold long-term continuous data sets (up to 29 years for some streams) detailing stream community evolution following glacial retreat. This data set has provided unique insights into primary succession (change over time) of stream invertebrates and fish. For one stream (Wolf Point Creek; WPC) a highly detailed trajectory of community change has been assembled since 1977, showing how the stream has evolved from one dominated by a few species of Chironomidae to one more recently (2005) containing a diverse community of invertebrates (insects/non-insects) and juvenile salmonids. However, during a brief visit to Glacier Bay at the beginning of June 2006 we observed that many of the streams (including WPC) had been severely affected by floods with major changes in channel morphology evident. This disturbance is likely to have had a major effect on the biological communities of these streams. Four major avenues of research will be followed: (1) the effect of the flooding on the stream habitat and morphology across streams of different ages, (2) an investigation of the effect of the flooding on the primary successional framework (invertebrates, fish) in Wolf Point Creek, (3) an investigation into the effects of the flooding on streams of different ages to provide information on how streams at different stages of successional development respond to flooding, and; (4) a stream side channel experiment to examine if resistant/resilient invertebrates modify the subsequent successional trajectory of stream biota. This study will assess the effects of these major flood disturbances on the primary succession trajectories of stream invertebrates and fish and identify persistent taxa. It is critical that we investigate as soon as possible the effect of the flood on the biotic communities because recolonisation and succession will potentially occur throughout this summer as communities recover. We aim to assess the recovery trajectory over the next 13 months to determine if full recovery occurs. It is probable that some invertebrate species have been lost from streams due to the flood, and these may take a long time to return due to the presence of dispersal barriers such as mountains and large icefields. The results will be in interpreted in terms of community persistence (constancy of presence/absence) and compositional stability (constancy of relative abundance of taxa) traits of the taxa that confer resistance and resilience and of habitat complexity providing the potential for more refugia.