Tree plantations are integral for meeting society’s demand for wood products and are increasing in total area worldwide. It is therefore critical to understand how plantations affect native biodiversity. Our aim was to examine the degree to which plantations affect biodiversity by 1) quantifying songbird abundance across a gradient in forest stand age (stand initiation through canopy closure), 2) estimating the duration of early seral habitat, and 3) testing if forest structural and compositional elements prolong habitat availability. This approach is equivalent to the modeling of wood ‘yield curves’ common in forest management but applied to a biodiversity indicator.

We used a chronosequence sampling design to survey songbirds and vegetation in 283 plantations aged 0–30 years in the Oregon Coast Range, USA. Stands were randomly selected within age strata and surveys were temporally replicated in order to use N-mixture models to estimate abundance after accounting for imperfect detection. The Coast Range is considered one of the most productive forest regions in the world and plantations occur on over 50% of the forested land base. Our chronosequence encompasses the assumed age of canopy closure, which we anticipated to be the point at which early seral biodiversity declines.

We detected 5074 birds of 71 species during the 2018 and 2019 breeding seasons. Canopy closure occurred approximately 12 years following clearcut harvest and replanting. We found that bird abundance changed dynamically during this short early seral stage. Twenty species peaked in abundance either very early in stand development or with the approximate timing of canopy closure, and then subsequently declined to low levels by the end of the 30-year chronosequence. The estimated abundance of 3 species increased following canopy closure. We also found, contrary to our hypothesis, that the amount of broadleaf cover increased habitat longevity for only one species – Wilson’s warbler.

To our knowledge, our study provides the first quantitative estimates for how bird species abundances change throughout the entire early seral stage in tree plantations in western North America – information that can be used to assess tradeoffs between timber production and biodiversity. We found that the duration of early seral habitat in plantations is short and generally cannot be ameliorated by managing for higher levels of broadleaf cover. This finding has important implications for early seral species in the rapidly shifting mosaic of tree plantation landscapes.

人工林是满足社会对木制品需求不可或缺的部分，并且在全球范围内的种植面积正在增加。因此，了解人工林如何影响本地生物多样性至关重要。我们的目的是通过以下方法来检查人工林对生物多样性的影响程度：1）在林分年龄的梯度范围内量化鸣鸟的丰度（通过冠层关闭进行林分萌生），2）估算早期的串行栖息地的持续时间，以及3）测试森林结构是否和组成元素延长了生境的可用性。这种方法等效于对森林管理中常见的木材“产量曲线”进行建模，但适用于生物多样性指标。

我们使用时间序列采样设计来调查美国俄勒冈海岸山脉283个年龄在0至30岁的人工林中的鸣禽和植被。在年龄层中随机选择林分，临时复制调查，以便在考虑不完善的检测后使用N-混合模型来估计丰度。沿海山脉被认为是世界上生产力最高的森林地区之一，人工林分布在超过50％的林地上。我们的时间序列涵盖了冠层封闭的假定年龄，我们预计这是早期血清生物多样性下降的时间点。

在2018年和2019年的繁殖季节，我们检测到71种动物的5074羽鸟类。采伐和重新种植后约12年，天篷关闭。我们发现，在这个短暂的早期串行阶段，鸟类的丰度发生了动态变化。20种物种在林分发育的早期或与树冠关闭的大致时机就达到高峰，然后在30年的时序序列结束时降到低水平。冠层关闭后，估计的3种物种的丰度增加了。与我们的假设相反，我们还发现，阔叶植物的覆盖量增加了仅一种物种（威尔逊的莺）的栖息地寿命。

据我们所知，我们的研究首次定量评估了北美西部树木种植园整个鸟类早期的鸟类物种丰度如何变化，这些信息可用于评估木材产量与生物多样性之间的权衡。我们发现人工林中早期血清生境的持续时间很短，并且通常无法通过管理较高水平的阔叶覆盖率来改善。这一发现对早期人工林物种在迅速变化的人工林景观中具有重要意义。