Structural diversity across transitions in heterogeneous landscapes

相邻植物群落之间的过渡或边界是可能容纳更大多样性的景观的重要特征。与人类活动造成的森林边缘相比，对天然森林边缘的研究较少，但更为复杂。研究人员一直致力于发展一种过渡理论，但许多元素仍然缺失，包括一个可以预测不同类型边缘的植被模式的模型，以及对森林景观中边缘的理解。在我的研究中，我使用了一种方法，将对天然林边缘植被的关注与对整个景观中植被模式的更广泛探索相结合。我追求新的方法，包括测量结构多样性，它结合了不同结构元素（树木、枯树、原木）和植被类型（高灌木、苔藓、地衣）的数量和丰度。我预计过渡区在景观上具有最高的结构多样性，因为它们：1)包含来自两个群落的结构元素，2)由于湖泊边缘的洪水和火场边缘的燃烧等干扰而经历更多的树木死亡，以及3)受到边缘增加的光和风的影响，导致结构变化（树木再生时更多的原木和树苗）。景观结构多样性的变化可能影响火灾模式、动物运动和小型生物栖息地的可利用性。我的长期目标是：A)预测不同森林中不同类型边缘的植被模式；B)确定森林景观跨过渡的结构多样性模式。我和我的学生将追求三个短期目标：1)我们将比较沿海森林边缘的植被结构模式。我们将估算过渡带的宽度，我们将把它与与海洋的距离、海拔和邻近的荒地（无树植被）的宽度联系起来。2)我们将从四种不同的景观中确定结构多样性的过渡模式：新斯科舍省西南部的湿地-森林和砍伐森林过渡，以及布雷顿角的云杉budworm干扰地区-森林和荒地-森林过渡。我们将使用长样带和空间分析来比较景观过渡部分和非过渡部分之间的结构多样性。3)比较不同结构多样性水平下景观过渡时期的植被。目标1的结果将有助于我开发一个预测模型的长期目标，这是一个在保护、气候变化研究和景观生态学中有用的工具。估算和预测过渡宽度对于了解不同管理活动对保护的影响和预测气候变化的影响具有重要意义。结构多样性有可能成为促进不同物种景观比较的重要工具，特别是在植物物种多样性普遍较低的加拿大。绘制结构多样性景观格局将有助于评估用于火灾管理的燃料可用性和用于保护的生境可用性。这些知识将极大地推动景观生态学领域的发展，该领域目前缺乏关于自然边缘的具体信息。加拿大将受益于更好地了解其森林的景观格局和过程，特别是因为它与可持续森林管理和气候变化有关。

Transitions or boundaries between adjacent plant communities are important features of landscapes that might harbour greater diversity. Natural forest edges are less studied than those created by human activity but are more complex. Researchers have been working towards developing a theory of transitions, but many elements are still missing including a model that can predict patterns of vegetation across different types of edges as well as an understanding of edges within forested landscapes. I use an approach in my research which combines a focus on vegetation across natural forest edges with a more extensive exploration of vegetation patterns across the landscape. I pursue new methods including measuring structural diversity which combines the number and abundance of different structural elements (trees, dead trees, logs) and types of vegetation (tall shrubs, moss, lichens). I expect transitions to have the highest structural diversity on the landscape because they: 1) contain structural elements from both communities, 2) experience more tree mortality from disturbance such as flooding at lake edges and burning at fire edges, and 3) are influenced by increased light and wind at edges which result in changes in structure (more logs and saplings as trees regenerate). Variation in structural diversity across landscapes could affect patterns of fire, animal movement and habitat availability for smaller organisms. My long term objectives are: A) to predict patterns of vegetation across different types of edges in different forests; and B) to determine patterns of structural diversity across transitions in forested landscapes. My students and I will pursue three short-term objectives: 1) We will compare the patterns of vegetation structure at coastal forest edges. We will estimate the width of the transition zone which we will relate to distance from the ocean, elevation and width of adjacent barrens (treeless vegetation). 2) We will determine patterns of structural diversity across transitions from four different landscapes: wetland-forest and clearcut-forest transitions in southwestern Nova Scotia, and spruce budworm disturbed area-forest and barrens-forest transitions in Cape Breton. We will use long transects and spatial analysis to compare structural diversity between transition and non-transition parts of the landscape. 3) We will compare vegetation at landscape transitions with different levels of structural diversity. Results from objective 1 will contribute towards my long-term goal of developing a predictive model, a useful tool in conservation, climate change research and landscape ecology. Estimating and predicting transition widths is important for understanding effects of different management activities for conservation and for predicting effects of climate change. Structural diversity has the potential to become an important tool to facilitate comparisons among landscapes with different species, particularly in Canada where plant species diversity is generally low. Mapping landscape patterns of structural diversity would be helpful for assessing fuel availability for fire management and habitat availability for conservation. This knowledge will greatly advance the field of landscape ecology which currently lacks specific information on natural edges. Canada will benefit from a greater understanding of landscape patterns and processes in its forests, especially as it relates to sustainable forest management and climate change.