Statistics, Mathematics, and Operations Research, Weyerhaeuser NR, Federal Way, Washington, United States of America.
PLoS One. 2012;7(8):e43290. doi: 10.1371/journal.pone.0043290. Epub 2012 Aug 15.
Managers of landscapes dedicated to forest commodity production require information about how practices influence biological diversity. Individual species and communities may be threatened if management practices truncate or simplify forest age classes that are essential for reproduction and survival. For instance, the degradation and loss of complex diverse forest in young age classes have been associated with declines in forest-associated Neotropical migrant bird populations in the Pacific Northwest, USA. These declines may be exacerbated by intensive forest management practices that reduce hardwood and broadleaf shrub cover in order to promote growth of economically valuable tree species in plantations.
We used a Bayesian hierarchical model to evaluate relationships between avian species richness and vegetation variables that reflect stand management intensity (primarily via herbicide application) on 212 tree plantations in the Coast Range, Oregon, USA. Specifically, we estimated the influence of broadleaf hardwood vegetation cover, which is reduced through herbicide applications, on bird species richness and individual species occupancy. Our model accounted for imperfect detection. We used average predictive comparisons to quantify the degree of association between vegetation variables and species richness. Both conifer and hardwood cover were positively associated with total species richness, suggesting that these components of forest stand composition may be important predictors of alpha diversity. Estimates of species richness were 35-80% lower when imperfect detection was ignored (depending on covariate values), a result that has critical implications for previous efforts that have examined relationships between forest composition and species richness.
Our results revealed that individual and community responses were positively associated with both conifer and hardwood cover. In our system, patterns of bird community assembly appear to be associated with stand management strategies that retain or increase hardwood vegetation while simultaneously regenerating the conifer cover in commercial tree plantations.
专门从事森林商品生产的景观管理者需要了解实践如何影响生物多样性。如果管理实践截断或简化了对繁殖和生存至关重要的森林年龄类群，那么个别物种和群落可能会受到威胁。例如，在太平洋西北地区，年轻龄级复杂多样森林的退化和丧失与森林相关的新热带候鸟种群的减少有关。这些下降可能会因密集的森林管理实践而加剧，这些实践减少了硬木和阔叶灌木的覆盖，以促进经济价值树种在人工林中的生长。
我们使用贝叶斯层次模型来评估鸟类物种丰富度与植被变量之间的关系，这些植被变量反映了俄勒冈州海岸山脉 212 个人工林的林分管理强度（主要通过使用除草剂）。具体来说，我们估计了阔叶硬木植被覆盖的影响，通过除草剂的应用来减少鸟类物种丰富度和个别物种的占有。我们的模型考虑了不完全检测。我们使用平均预测比较来量化植被变量与物种丰富度之间的关联程度。针叶树和硬木覆盖都与总物种丰富度呈正相关，这表明森林林分组成的这些组成部分可能是物种多样性的重要预测指标。当忽略不完全检测（取决于协变量值）时，估计的物种丰富度降低了 35-80%，这一结果对以前检查森林组成与物种丰富度之间关系的努力具有关键意义。
我们的结果表明，个体和群落的反应与针叶树和硬木覆盖都呈正相关。在我们的系统中，鸟类群落组装的模式似乎与保留或增加硬木植被的林分管理策略有关，同时在商业人工林中再生针叶树覆盖。
