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)或迅速恢复(恢复能力)在洪水中幸存下来。虽然对严重洪灾对河流生态系统的干扰已有较好的研究，但许多研究都有一个有限的干扰前系列数据来评估洪水的影响，很少从其演替发展的角度进行评估。这在一定程度上反映了对河流群落的最低限度的连续、按年监测，以衡量任何干扰影响。2005年11月21日至26日，一场强风和创纪录的降雨量的冬季风暴在阿拉斯加东南部造成了大范围的洪水、山体滑坡和风灾。朱诺、海恩斯和锡特卡市宣布了当地的灾难，并请求国家和公共援助以应对和恢复。阿拉斯加东南部冰川湾地区持续强降雨(不到72小时超过650毫米)，导致大范围洪水泛滥，多条河流受到极端干扰。与920 MM的年平均降雨量相比，这次地震的规模是显而易见的。在冰川湾，我们拥有长期的连续数据集(某些河流长达29年)，详细描述了冰川消退后河流群落的演变。该数据集为溪流无脊椎动物和鱼类的初级演替(随时间变化)提供了独特的见解。对于一条溪流(Wolf Point Creek；WPC)，自1977年以来已经收集了一条非常详细的群落变化轨迹，显示了这条溪流是如何从由几种摇蚊科主导的河流演变为最近(2005年)包含各种无脊椎动物(昆虫/非昆虫)和幼鲑鱼群落的河流。然而，在2006年6月初对冰川湾的短暂访问中，我们观察到许多溪流(包括WPC)受到洪水的严重影响，河道形态明显发生重大变化。这种干扰很可能对这些溪流的生物群落产生了重大影响。将通过四个主要途径进行研究：(1)洪水对不同年龄河流的河流栖息地和形态的影响；(2)洪水对狼点溪初级演替框架(无脊椎动物、鱼类)的影响调查；(3)洪水对不同年龄河流的影响调查，以提供不同演替发展阶段的河流如何对洪水作出反应的信息；(4)溪边河道实验，以研究抵抗/有韧性的无脊椎动物是否会改变河流生物群随后的演替轨迹。这项研究将评估这些主要洪水扰动对溪流无脊椎动物和鱼类的初级演替轨迹的影响，并确定持久的类群。我们尽快调查洪水对生物群落的影响是至关重要的，因为随着群落的恢复，重新殖民和演替可能会在整个夏天发生。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。洪水可能导致一些无脊椎动物物种从溪流中消失，而由于山脉和大冰原等扩散障碍的存在，这些物种可能需要很长时间才能恢复。结果将从群落持久性(存在/不存在的恒定性)和组成的稳定性(类群的相对丰度恒定)以及提供更多避难所的生境复杂性的分类群的抗性和复原性特征来解释。

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.