Direct and indirect effects of climate on bird abundance along elevation gradients in the Northern Appalachian mountains

Abstract

Aim:The stratification of organisms along elevational gradients is widely reported, with montane communities characterized by species occurring in relatively small and isolated populations; these species are of considerable interest to ecologists and conservationists. This stratification is generally attributed to climatic zonation. Evidence that species are shifting upward in elevation has fuelled speculation that species are tracking their climatic niches in response to climate change. Uncertainty regarding the degree to which climate directly influences species abundance versus the degree to which climate has an indirect influence via vegetation represents a key impediment to understanding the ecology of montane species; here, we evaluate these direct and indirect effects. Location: White Mountains, New Hampshire, USA. Methods: We used N-mixture models to correct for imperfect detection of species, principal component analysis to represent gradients in vegetation structure and composition and structural equation models to assign variation to the direct and indirect effects of climate upon birds.Results: Analysis of 13 species revealed that climate exerts direct influences on bird abundance and indirect influences mediated by vegetation composition and structure. All species exhibited indirect effects of climate via forest habitat, with 77% exhibiting both direct and indirect effects and 53% exhibiting stronger indirect effects. Main conclusions:We provide insight into the mechanistic pathways of how climate influences the distribution of species along elevational gradients, underscoring the complex vulnerability of species to climate change. Our results reveal that the majority of species experience both direct and indirect effects of climate, implying that forests play a key role in mediating climate effects. For species that are primarily influenced by climate directly, typical climate envelope models may continue to be informative, but for the majority of the species included in this study, we show that distribution models should also include measures of habitat. K E Y W O R D S climate change, climate effects, montane bird abundance, spruce-fir ecosystems, structural equation modelling | 1671 DUCLOS et aL.

Elevation patterns and critical environmental drivers of the taxonomic, functional, and phylogenetic diversity of small mammals in a karst mountain area

“…Our results partially support this hypothesis: NPP, a productive energy parameter, exhibited a strong positive relationship with TD for all groups, and AP was positively related to TD for most of the groups (all species, broad‐range species, and Rodentia species). Changes in precipitation patterns provide a chance for high‐elevation species to expand their population (Duclos, DeLuca, & King, 2019). The negative effects of precipitation that we found for narrow‐range species and Eulipotyphla species are in concordance with the findings of previous studies showing that heavy rain events may have negative effects on many taxa (Aizen et al 2003) potentially because of associated foraging restrictions (Boyle, Norris, & Guglielmo, 2010).…”

Interactive range‐limit theory (iRLT): An extension for predicting range shifts

“…growth rates) along range limits. Modelling frameworks that allow for the inclusion of correlated direct and indirect predictors, like structural equation modelling (Joseph, Preston, & Johnson, ), provide a promising avenue (see for example Duclos, DeLuca, & King, ). Future research could prioritize large‐scale observational studies that collect data on direct and indirect effects at the same spatial and temporal scale, as well as extend beyond the range of the focal species to identify limiting factors (Louthan et al, ; Westoby et al, ).…”

Interrelationship between Environmental Drivers and Avian Biodiversity in a Mediterranean Like Natura 2000 Wetland and Implications for Conservation Management <sup>†</sup>

“…Climate change is also being assessed that it will exacerbate the loss of species, in particular species of limited range climate and ecological requirements and limited migration possibilities (IPCC 2007) [20]. Moreover, alterations in climate may also affect biodiversity in an indirect way, changing ecosystems and habitat characteristics in an accelerating way and thus modifying the behavior, distribution range and population dynamics of avian assemblages [21]. To the best of our knowledge no detailed study has been conducted in wetland area of Northern Greece to determine the particular association of avian biodiversity with microclimate.…”