Scaling habitat loss and fragmentation of old forests on bird communities in boreal landscapes

由于人类活动，世界各地的森林正在发生重大变化。在加拿大东部的北方森林，过去35年来木材采伐的向北扩展使年龄级分布从以前以成熟和老森林覆盖类型为主的矩阵转变为现在以年轻森林为主的矩阵。这代表了在整个全新世进化并经历了高度可用的封闭树冠和拱心石结构（如腐烂和死亡的树木）的生物的重大变化。老森林比例的减少特别影响了那些专门栖息于封闭树冠（开杯筑巢者）和腐烂和死亡树木（洞巢筑巢者）的物种。鸟类对旧森林覆盖丧失和破碎化的景观尺度敏感性通常在鸟类采样站附近（500米至2公里半径）进行评估。这些方法提供了在局部尺度上对物种反应的深刻认识。然而，它们在推断这种模式如何在整个森林马赛克的区域人口水平上转化方面是有限的。要做到这一点，就需要对生物群落进行大规模的鸟类调查。繁殖鸟类地图集（BBA）项目最近纳入了细粒度调查（点计数），现在为调查鸟类种群对大地理区域栖息地变化的反应提供了这样的机会。该方案以quacimbec的商业北方森林为尺度，测量了将森林年龄结构从老森林马赛克转变为年轻森林马赛克对鸟类群落反应的影响。我们将广泛（区域，BBA数据）和密集（本地，实地研究）的方法结合起来，对开杯和洞巢进行研究：1)评估区域尺度上旧森林的丧失和破碎化对敏感鸟类种群的影响；2)确定采伐景观的更新动态如何使旧森林鸟类群落具有复原力；3)衡量当地栖息地质量和原始森林连通性对鸟类筑巢和觅食生态的驱动作用。通过扩大鸟类种群和群落对原始森林损失和破碎化的响应，从局部到区域的影响，拟议的研究计划将有助于我们对人类改造景观中木材采伐制度对北方生物多样性的累积影响的理解取得突破性进展。除了传统的分类多样性外，利用性状为基础的方法（开杯巢和腔巢）将为确定北方鸟类群落功能多样性响应的关键栖息地驱动因素提供一个原始的视角。从保护规划的角度来看，拟议的研究将为制定加拿大北方森林政策提供创新的基于科学的指导方针，以更好地应对在快速变化的世界中保持生物多样性和可持续森林管理的长期挑战。

Forests worldwide are undergoing major changes as a result of human activity. In the eastern boreal forest of Canada, the northern expansion of timber harvesting in the last 35 years has shifted the age-class distribution from a matrix formerly dominated by mature and old forest cover types to a matrix that is now dominated by young forests. This represents a major change for organisms that evolved and experienced high availability of closed canopy and keystone structures such as decaying and dead trees throughout the Holocene. This reduced proportion of old forests specifically affects species that are specialised on closed canopy (open-cup nesters) and on decaying and dead trees (cavity nesters). Landscape-scale sensitivity of birds to loss and fragmentation of old forest cover has usually been assessed in the neighbourhood of bird sampling stations (500 m to 2-km radius). Such approaches provide insightful knowledge on species responses at local scales. They are, however, limited for extrapolating how such patterns translate at the level of regional populations, across the entire forest mosaic. To do so large-scale bird surveys over biomes are required. Breeding Bird Atlas (BBA) projects, which have recently incorporated fine-grain scale surveys (point counts), now provide such opportunities for investigating bird populations' responses to habitat changes over large geographic regions. This proposal measures at the scale of Québec's commercial boreal forest the effects of shifting the forest age structure from an old to a young forest mosaic on the response of bird communities. We combine extensive (regional, BBA data) and intensive (local, field studies) approaches on open-cup and cavity nesters to: 1) assess the regional-scale effects of loss and fragmentation of old forests on populations of sensitive birds; 2) determine how the dynamics of regeneration in harvested landscapes enables the resilience of old forest bird communities; 3) measure how local habitat quality and connectivity of old forests are drivers in bird species nesting and foraging ecology. By scaling-up the response of bird populations and communities to old forest loss and fragmentation from local to regional effects, the proposed research program will contribute to groundbreaking advances in our understanding of the cumulative effects of timber-harvesting regimes on boreal biodiversity in human-modified landscapes. The use of a trait-based approach (open-cup and cavity nesters) in addition to traditional taxonomic diversity will provide an original perspective to pinpoint critical habitat drivers to which the functional diversity of boreal bird communities responds. From a conservation planning perspective, the proposed research will produce innovative science-based guidelines for developing policies in the Canadian boreal forest that better meet the long-term challenges of maintaining biodiversity and sustainable forest management in a rapidly changing world.