Avian Species Richness in Relation to Intensive Forest Management Practices in Early Seral Tree Plantations

Abstract

BackgroundManagers 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.Methodology and Principal FindingsWe 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.Conclusion and SignificanceOur 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.

Assembly dynamics of a forest bird community depend on disturbance intensity and foraging guild

“…We expect this dynamic to persist as additional species, unobserved to this point, will occupy harvest stands as the conifer crop matures and habitat diversity increases (Ellis & Betts ; Jones et al . ).…”

“…Given that the moderate treatment is analogous, in terms of herbicide application and subsequent vegetation control, to silvicultural activities common to private ownerships globally (and replicates a prescription applied to millions of hectares in the Pacific Northwest, USA), our results indicate that trade‐offs between timber growth and avian diversity may be less severe than expected from shorter term studies (Jones et al . ; Betts et al . ).…”

Explaining the birds and the bees: deriving habitat restoration targets from multi‐species occupancy models

“…Advancements in multi-species occupancy modeling (MSOM; Iknayan et al 2014) provide a promising tool for identifying desired postrestoration habitat conditions based on the needs of broad taxonomic groups or guilds of species (White et al 2013), including species that are rarely observed. Most MSOM-based prescriptions for management or restoration have addressed a single, broad group such as birds (Russell et al 2009, Zipkin et al 2010, Jones et al 2012, White et al 2013 or mammalian carnivores (Burton et al 2012, Van der Weyde et al 2018). However, just as individual species respond to management in diverse ways, so do broad taxonomic groups (Chaudhary et al 2016).…”

Guidelines for a priori grouping of species in hierarchical community models

“…A major benefit of shrinkage is the ability to estimate parameters for species that are rarely detected and would otherwise not be estimable or would be too imprecise for meaningful inference (K ery and . Multispecies hierarchical models have subsequently been used to address community-level responses to environmental factors (Zipkin et al 2009;Burton et al 2012;Jones et al 2012) and management activities (Russell et al 2009;Zipkin et al 2010;Giovanini et al 2013;Hunt et al 2013) as well as understanding individual species-level responses to landscape/habitat features (Tingley and Beissinger 2013) and management or conservation actions (Grant et al 2013;Sauer et al 2013). The approach is also particularly useful for rare or infrequently detected species (White et al 2013).…”