Cumulative effects of natural and human disturbances on ecological networks of cavity nesters in managed boreal landscapes

自然和人为干扰对管理北方景观中洞穴筑巢者生态网络的累积影响

• 批准号: RGPIN-2014-05879
• 负责人: Drapeau, Pierre
• 金额: $ 2.48万
• 依托单位: Université du Québec à Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=649584
• 关键词: Cumulative; effects; natural; human; disturbances

In the eastern Canadian boreal forest, natural disturbance regimes under wildfires with moderate fire cycles (100-200 years) historically generated an age structure of forest stands made up of early post-fire landscapes embedded in a matrix dominated by a high proportion of mature to old-growth forest cover types. Such disturbance regimes are recognized as important determinants of forest biodiversity, particularly for organisms that evolved under a high availability of senescent and dead trees in both old forest and post-fire stands. It is now well documented that even-aged management is shifting this land base into a much younger mosaic of forest cover types, inducing large-scale changes that considerably reduce the natural proportion of older forests and, hence, the amount and spatial distribution of decaying wood, a key habitat attribute for biodiversity in the boreal ecosystem. In addition, natural disturbances (wildfires, insect outbreaks and windthrows) still occur in the boreal forest. Cumulative effects of logging and natural disturbances in the managed boreal ecosystem are thus rapidly changing forest conditions for species associated with large decaying trees. *Birds using tree cavities represent a demanding group of species in terms of habitat attributes requirements (decaying wood) and are thus highly sensitive to forest management. Among these species, woodpeckers are of particular interest considering their keystone role (main cavity producers) for cavity nesting bird communities in Canada's boreal forests. At the landscape level, the change in the availability of decaying wood may modify the ecological networks of cavity producers (woodpeckers) and secondary users (owls, ducks, passerines and mammals), and thus, the functional diversity in old forest patches across managed boreal lands. Increased knowledge of demographic responses of bird cavity-nesters and the ecological networks (nest webs) that they generate in this new environment is thus critical in the overall assessment of the sustainability of boreal old forest bird communities. *In this proposal we (1) measure the nest web structure of cavity nesting bird communities and reproductive activity of keystone species (woodpeckers) within managed landscapes, (2) assess the functional role of old forest habitats, in particular linear strips (riparian buffers and cutblock separators) which make up an important proportion of remnant old forests for both cavity-nesting birds and other old forest bird associates, and (3) evaluate at the landscape level the persistence of the cavity-nesting bird community in old remnant habitats of managed forests. This research will draw on intensive work on nest web structure and fitness components of keystone cavity-producers conducted at a local scale in permanent plots (10-40 ha) (Objective 1) that will be linked with a more extensive regional investigation (Objectives 2 and 3) on occupancy and persistence of cavity nesters in managed boreal forest landscapes to assess how fine-grained patterns and processes at local scales translate into more generalized patterns at regional scales. *By measuring how ecological networks of cavity-nesting birds respond to forest cover changes, the main innovation of this research program is to shift from a taxonomic to a functional diversity perspective whereas our work will focus on how ecological relationships among the cavity-nesting community are affected by changing forest conditions. This will directly contribute to our long term objective which is to develop conservation targets of old forest habitat that can be set for not only maintaining species in managed forests but foremost the underlying functioning of bird communities, using the cavity-nesting community as a model.

在加拿大东部的北方森林中，中等火灾周期（100-200年）野火下的自然干扰制度历史上产生了一种林分年龄结构，该结构由早期火灾后景观组成，嵌入以高比例的成熟到老年森林覆盖类型为主的矩阵中。这种干扰制度被认为是森林生物多样性的重要决定因素，特别是对于在老森林和火灾后林中大量衰老和死树下进化的生物体。现在有充分证据表明，同龄管理正在将这片土地基础转变为更年轻的森林覆盖类型镶嵌体，从而引发大规模变化，大大减少了古老森林的自然比例，从而减少了腐烂木材的数量和空间分布，而腐烂木材是北方生态系统生物多样性的一个关键栖息地属性。此外，北方森林中仍然会发生自然干扰（野火、昆虫爆发和风吹）。因此，在管理的北方生态系统中，伐木和自然干扰的累积影响正在迅速改变与大型腐烂树木相关的物种的森林条件。 *使用树洞的鸟类代表了对栖息地属性要求（腐烂木材）要求很高的物种，因此对森林管理高度敏感。在这些物种中，啄木鸟尤其令人感兴趣，因为它们在加拿大北方森林的洞穴筑巢鸟类群落中发挥着关键作用（主要的洞穴生产者）。在景观层面，腐烂木材可用性的变化可能会改变空洞生产者（啄木鸟）和次要使用者（猫头鹰、鸭子、雀形目动物和哺乳动物）的生态网络，从而改变管理的北方土地上旧森林斑块的功能多样性。因此，增加对鸟类空巢鸟类的人口反应及其在这种新环境中产生的生态网络（巢网）的了解对于全面评估北方古老森林鸟类群落的可持续性至关重要。 *在本提案中，我们（1）测量管理景观中洞穴筑巢鸟类群落的巢网结构和关键物种（啄木鸟）的繁殖活动，（2）评估古老森林栖息地的功能作用，特别是线性带（河岸缓冲区和切割块分隔物），它们构成了洞穴筑巢鸟类和其他古老森林鸟类的残余古老森林的重要比例，以及（3）评估 景观水平 管理森林的旧残余栖息地中空巢鸟类群落的持续存在。这项研究将利用在永久性地块（10-40公顷）（目标1）的局部范围内对基石空洞生产者的巢网结构和适应性组成进行的深入研究，该研究将与对管理的北方森林景观中空洞筑巢者的占用和持久性进行更广泛的区域调查（目标2和3）相结合，以评估当地规模的细粒度模式和过程如何转化为更普遍的模式 区域尺度。 *通过测量空巢鸟类的生态网络如何响应森林覆盖变化，该研究项目的主要创新之处在于从分类学角度转向功能多样性视角，而我们的工作将重点研究空巢群落之间的生态关系如何受到森林条件变化的影响。这将直接有助于我们的长期目标，即制定旧森林栖息地的保护目标，该目标不仅可以维持管理森林中的物种，而且最重要的是以空巢群落为模型，维持鸟类群落的基本功能。