Influences of Herbivory on Treeline Under Changing Climate

在北极和高山地区都存在着世界范围内的树线，许多树线已经被证明在短期和长期的气候变化中做出反应。 迄今为止，大多数树线研究都集中在树线位置的气候控制上。 然而，一些树线环境除了气候外，还可能受到食草动物的控制。 该研究项目的重点是芬诺斯堪的纳维亚的树木，这是驯鹿草食动物和秋季蛾的零星侵扰的影响。 驯鹿放牧是当地土著人民（萨米人）文化的重要组成部分。 本研究的目的是发现如何草食动物与气候变化的相互作用，影响树木的建立和生长在树线，从而有助于迁移潜力的一个主要的生态交错带（植被边界）。 这项研究将使用树木年代学方法，结合长期的高质量数据集的气候，驯鹿种群和秋季蛾爆发在北方瑞典。 主要的假设是，建立和树木生长的存在下，大型草食动物种群的负面影响。 将使用相关性分析、方差分析和协方差分析检验假设。 预计在超树线地带树木生长旺盛的时期，驯鹿数量较少，也没有蛾类爆发。 同样，当控制不同的气候时，当食草动物种群较低时，树木的生长将会很高。植被边界的动态因其与气候变异性的联系而引起广泛关注。 特别是树木交错带，受到了对气候变化影响感兴趣的科学家的极大关注。 这项研究将通过调查草食动物的影响，为树线动态科学做出重要贡献。 了解草食动物和气候的综合影响对于解释树线植被的变化至关重要。 林线交错带是一个模拟的交错带在各种环境中，因此，结果应该是广泛适用的。 此外，通过揭示驯鹿吃草对植被的影响，这项研究将为可持续驯鹿放牧做法的实施提供信息。 该项目将为研究生和本科生提供研究和教育机会。

Treelines exist world-wide in both Arctic and alpine locations, and many have been shown to respond to changes in climate over both short and long time spans. Most treeline research to date has focused on climatic controls of treeline location. Some treeline environments, however, are potentially controlled by herbivory in addition to climate. This research project focuses on Fennoscandian treelines, which are affected by reindeer herbivory and sporadic infestations of autumnal moths. Reindeer herding is an important part of the culture of the local indigenous people (Sami). The objective of this research is to discover how herbivory interacts with climatic variability to influence the establishment and growth of trees at treeline, and thereby contributes to the migration potential of a major ecotone (vegetation boundary). The research will be accomplished using dendrochronological methods combined with long-term high-quality datasets of climate, reindeer populations, and autumnal moth outbreaks in northern Sweden. The primary hypothesis is that establishment and tree growth are negatively affected by the presence of large herbivore populations. The hypothesis will be tested using correlation analysis, analysis of variance and analysis of covariance. It is expected that periods of abundant tree establishment in the supra-treeline zone correspond to periods with low reindeer populations and no moth outbreaks. Similarly, when controlled for varying climate, tree growth will be high when herbivore populations are low.The dynamics of vegetation boundaries are of broad interest because of their link to climatic variability. The treeline ecotone, in particular, has received much attention from scientists interested in the effects of climate change. This research will make a vital contribution to the science of treeline dynamics by investigating the influence of herbivory. Understanding the combined influences of both herbivory and climate are critical for interpreting changes in treeline vegetation. The treeline ecotone is an analog for ecotones in a wide variety of environments, and therefore the results should be broadly applicable. Moreover, by revealing the influence of reindeer browsing on vegetation, the research will inform the implementation of sustainable reindeer herding practices. The project will provide research and educational opportunities for graduate and undergraduate students.