The relationship of tropical bird communities to tree species composition and vegetation structure along an Andean elevational gradient

Abstract

Aim Understanding patterns of species turnover along environmental gradients and their consistency across taxonomic groups is central to the study of biodiversity. We may expect congruence in diversity patterns across groups whose ranges could be influenced by species interactions. We explore associations between bird and vegetation communities in the tropical Andes to determine whether patterns of species richness and turnover in birds and trees are congruent with elevation, and whether tree species composition, vegetation structure, elevation, or a combination of these best predicts bird species composition. Location A forested 2600‐m elevational gradient on the eastern slope of the Peruvian Andes. Methods Bird surveys and vegetation measurements were conducted at 172 points, and a subset of these were spatially matched with fourteen 1‐ha tree inventory plots. Diversity patterns were described for trees, birds, and avian foraging guilds. We used dissimilarity matrices to examine patterns of turnover and nestedness. Turnover of birds and trees was examined by comparing compositional change of adjacent plots along the gradient. Multiple regression on distance matrices was employed to determine contributions of tree species composition, vegetation structure and elevation to explaining variation in bird species composition. Results Species richness was higher for trees than for birds, and whereas diversity in both taxa decreased with elevation, tree richness showed a low‐elevation plateau before declining at higher elevations. Tree species had narrower distributions compared to birds, but patterns of turnover were largely congruent between taxa. Nestedness contributed much less to dissimilarity than turnover, although birds showed higher nestedness, particularly at high elevations. Tree species composition, elevation and vegetation structure were all important predictors of bird species composition; the best model explained 78% of bird dissimilarity across plots. Tree species composition was always included in the best models, for all birds and foraging guilds. Main conclusions Our assessment of Andean bird and vegetation communities suggests strong correspondence, perhaps due to direct interactions or similar underlying drivers. We hypothesize that with climate change, range shifts in these groups may not occur independently. Rather, birds may have delayed upslope shifts or may be limited to high‐elevation patches where appropriate vegetation communities exist.

Shifts in resident bird communities associated with cloud forest patch size in Central Veracruz, Mexico

“…Although there may be high species turnover rates in cloud forests (Jankowski et al 2013), we found an important variation in community composition for the largest fragment size category that was caused by changes in the abundance of forest understory and endemic species. Our results show that differences recorded in this study were mainly caused by the reduced numbers of forest-dependent understory insectivores in smaller forest fragments, possibly because of a greater influence of border effects (Banks-Leite et al 2010) and the associated structural changes in vegetation in smaller fragments that benefit the presence of omnivore species (Jankowski et al 2013). …”

Producing Diversity: Agroforests Sustain Avian Richness and Abundance in India's Western Ghats

“…Anand et al (2010) in their meta-analysis of 35 studies examining 14 taxonomic groups found that forest cover was a major influence on vertebrates in human-modified landscapes of the Ghats. Clough et al (2009) found that higher bird species richness in Indonesian cacao plantations was associated with tree density and Janowski et al (2012) found that tree species composition to influence bird species richness in the Andes. Bhagwat et al (2005) have demonstrated that tree cover may reduce the influence of patch area or isolation on species richness and have a buffering impact on biodiversity loss within human-cultivated landscapes in the Western Ghats.…”

“…This sets the background for further analyses of bird-habitat relationships at multiple spatial scales, particularly of species that are of ecological and conservation importance. Opportunities for future research include comparisons of multiple land uses with protected reserves, as well as examining spatial dynamics (such as local extinction, colonization, turnover and change in occupancy) over time (Janowski et al, 2012;Irizarry et al, 2016). This requires establishing long-term monitoring studies of bird communities in the region.…”

Seasonal production, allocation and cycling of carbon in two mid-elevation tropical montane forest plots in the Peruvian Andes

“…This suggests that a distinct ecological transition occurs between 1500 and 1750 m. Recent publications from the Kosñipata elevation transect (including these two plots) present evidence of a step change in below-ground (Girardin et al 2013a) and above-ground (C. Girardin 2013, pers comm. ) productivity at the base of the cloud immersion zone, with significantly lower productivity rates and a sharp decline in tree biodiversity (Jankowski et al 2012) in plots located within the cloud immersion zone. As a probable increase in cloud immersion frequency at SPD 1750 is the main difference between the two sites, we conclude that the distinct ecological difference between these plots is likely to be related to the cloud immersion zone rather than the linear change in temperature with increasing elevation.…”