Bird species richness in High-Andean forest fragments: habitat quality and topography matter

Constance Fastré,Diederik Strubbe,Hannes Ledegen,Jennifer R.A Cahill,José A Balderrama,Mauricio Torrico Orellana,Erik Matthysen

doi:10.26496/bjz.2020.76

Abstract

Montane forests worldwide are known centers of endemism and biodiversity but are highly threatened by fragmentation processes. Using data collected in 15 Polylepis forest remnants covering 2000 hectares, we investigated how bird species richness and bird community composition, particularly for species of conservation concern, are influenced by habitat quality and topography in the Tunari National Park in the High Andes of Bolivia. Bird species richness was highest in topographically complex, low-elevation Polylepis patches located in areas with a high potential to retain rainwater. Bird communities differed strongly between Polylepis lanata and P. subtusalbida remnants, each supporting different threatened and endemic species. Within the P. subtusalbida forest, high-elevation fragments characterized by high amounts of sunlight and low anthropogenic disturbance were more likely to contain threatened species. Surprisingly, we found no effect of fragment size on the diversity or composition of bird communities or the presence of bird species of conservation concern. The presence of exotic plantations (Pinus and/or Eucalyptus spp.) in or outside forest remnants was negatively associated with the number of bird species as well as with occurrence of the endangered Cochabamba-mountain finch (Compsospiza garleppi). To support the different communities found in Polylepis forests, these results suggest that conservation efforts should be directed towards both forest types (P. subtusalbida and P. lanata) present in the area. For an efficient management of avian diversity, exotic plantations should be established away from native remnants while existing patches should be managed to maintain or increase habitat quality. Finally, the importance of local topography in determining avian species richness and community composition in forest fragments, mainly through topographic controls on moisture distribution and the amount of sunlight received by the fragments, should be considered when planning conservation and reforestation schemes.

Highlights

Montane forests worldwide are important centers of biodiversity and endemism and provide numerous ecosystem services as they help to retain water, stabilize soils, store carbon and increase soil fertility (Aubad et al 2010)
Using data collected in 15 Polylepis forest remnants covering 2000 hectares, we investigated how bird species richness and bird community composition, for species of conservation concern, are influenced by habitat quality and topography in the Tunari National Park in the High Andes of Bolivia
Polylepis forest remnants of the Tunari National Park constitute an important habitat for Andean bird conservation as they harbor 144 different species, including numerous endemic and/or threatened species (Table S2)

Summary

Introduction

Montane forests worldwide are important centers of biodiversity and endemism and provide numerous ecosystem services as they help to retain water, stabilize soils, store carbon and increase soil fertility (Aubad et al 2010). Due to extensive historical and ongoing anthropogenic activities, less than 10% of the original Polylepis forest cover is estimated to remain, making it one of the most endangered forested ecosystems in the world (WCMC 2004) This degradation is mainly caused by slash-and-burn agriculture techniques, cattle overgrazing, firewood collection and the replacement of native forests by exotic plantations (Fjeldså & Kessler 1996; Hensen 2002; Balderrama 2006; Gareca et al 2007, 2010; Hensen et al 2012). There is a strong debate as to what extent their patchy distribution is natural (Gosling et al 2009; Williams et al 2011) or caused by anthropogenic activities, but evidence points to human-induced pressures leading to extensive habitat loss and increased isolation over time (Fjeldså & Kessler 1996; Cierjacks et al 2007; Torres et al 2008; Toivonen et al 2011; Alinari et al 2015)

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Results

Conclusion