Collaborative Research: Using Demographic Techniques to Test for the Signatures of Environmental Change

评估当前或未来气候变化对环境的真正重要性的一个主要困难是缺乏来自过去的充分监测数据。特别是，用于推断气候变化后果的大多数方法依赖于过去的数据来确定正常或基线条件。在这里提出的工作中，开发了一种技术来绕过这个问题，而是依赖于当前人口规模或年龄结构与当前人口统计学预测之间的比较，以在缺乏过去数据的情况下测试当地或全球环境变化对生态影响的证据。在本研究中，我们将对一种环缘高山垫层植物——青松（Silene acaulis）的种群结构和种群数量进行定量分析。这项工作将在阿拉斯加中南部进行。这个地区在过去的三十年里经历了气温的快速上升。在阿拉斯加弗兰格尔山脉的野外地点，将收集两种类型的数据：1)单个植物的生长、繁殖和存活的人口统计数据；2)几个不同种群中植物的大小频率。通过比较观察到的大小频率与使用当前人口统计学数据的随机计算机模型预测的大小频率，将测试关于Silene人口统计学如何由于环境变化而发生变化的具体假设（例如，早期融雪和较高的夏季温度是否导致幼苗吸收减少，但成虫生长速度增加？）。为了证实由我们的模型确定的最可能的人口对过去气候变化的反应，还将进行额外的实验来修改季节长度和温度，以便直接评估气候变化对人口表现的影响。这些实验将符合国际冻土带实验（ITEX，一个由北极和高山全球变化研究人员组成的国际联盟）的标准协议，从而使结果能够与气候变化影响的环环评估联系起来。通过提供一种方法来回顾环境变化对人口水平的影响，这项工作将扩大用于检测过去变化对生物影响的方法工具箱，并为确定正在进行的气候变化的影响是否会在未来加速提供基线。

Morris/Doak 9806818 A major difficulty in assessing the real environmental importance of ongoing or future climate change is the lack of adequate monitoring data from the past. In particular, most methods used to infer the consequences of climate change rely upon past data to determine normal or baseline conditions. In the work proposed here, a technique is developed that circumvents this problem, relying instead on a comparison between current population size or age structures and those predicted by current demography to test for evidence of the ecological effects of local or global environmental change, in the absence of past data.. In the proposed work, the demography and population structure of Silene acaulis, a circumboreal alpine cushion plant, will be quantified. The work will be conducted in southcentral Alaska,. an area that has undergone rapid increases in temperature over the last three decades. At the field sites in Alaska's Wrangell Mountains, two types of data will be collected: 1) demographic measures of the growth, reproduction, and survival of individual plants; and 2) the size frequencies of plants in several distinct populations. By comparing the observed size frequencies to those predicted by stochastic computer models using the data on current demographic rates, specific hypotheses about how Silene demography may have changed due to environmental alteration will be tested (for examples, has earlier snowmelt and higher summer temperatures led to decreased seedling recruitment but an increase in the growth rates of adults?). In order to corroborate the most likely population responses to past climate changes identified by our models, additional experiments will be also be conducted to modify season length and temperature in order to directly assess the effects of climatic changes on demographic performance. These experiments will conform to the standard protocols of the International Tundra Experiment (ITEX, an international consortium of arctic and alpine global change researchers), thus allowing the results to be linked to a circumboreal assessment of climate change effects. By providing a method to look retrospectively at the population-level effects of environmental change, the work proposed will both expand the toolbox of methodologies available for detecting biotic effects of past changes and provide a baseline for determining whether effects of ongoing climate changes will accelerate in the future.