Euridice Leyequien, Jose Luis Hernandez-Stefanoni, Waldemar Santamarla-Rivero, Juan Manuel Dupuy-Rada, and Juan Bautista Chable-Santos
Abstract Previous studies have emphasized the importance of including not only the potential and costs of different land use/land cover alternatives on carbon sequestration but that also there is a need to study the impact of the resulting land cover changes on biodiversity. Tropical forests are undergoing rapid transformation as the result of human activities, which have created more than 600 million ha of secondary vegetation. In particular, tropical dry forests (TDF) are under great pressure caused by conversion to agriculture and other land uses, resulting in a heterogeneous landscape mosaic of secondary forest in different stages of succession or small forest remnants embedded in a matrix of agriculture. Changes in the landscape mosaic affect patterns of animal species abundance and distribution and, consequently, influence community composition. Despite the prevalence of succes – sional forests, few studies have examined their influence on higher trophic levels such as bird communities. The aim of this study was to examine the relative influence of successional age, vegetation structure, and landscape structure on bird guild composition in a TDF region in the Yucatan Peninsula, an important area for migratory birds characterized by high avian endemism. Species composition of different bird feeding guilds was calculated for 274 plots of bird point counts, and vegetation structure was obtained from a vegetation survey in the same plots. We used a land cover thematic map, derived from a supervised classification of SPOT5 satellite imagery, to calculate landscape pattern metrics. Species composition of birds was related to structure of vegetation, landscape metrics of patch types, and principal coordinates of neighbor matrices (PCNM) variables using canonical correspondence analysis (CCA). Overall, bird feeding guilds were
E. Leyequien (*) • J. L. Hernandez-Stefanoni • W. Santamana-Rivero • J. M. Dupuy-Rada Centro de Investigation Cientifica de Yucatan, Mexico e-mail: leyequien@cicy. mx
J. B. Chable-Santos
Universidad Autonoma de Yucatan, Mexico
N. Nakagoshi and J. A. Mabuhay (eds.), Designing Low Carbon Societies in Landscapes, Ecological Research Monographs, DOI 10.1007/978-4-431-54819-5_11, © Springer Japan 2014
influenced by stand age, vegetation structure, and spatial structure of sampled data, and marginally by landscape composition and configuration, but varied in their response and susceptibility to habitat changes. Sound conservation and management should take into account forest specialist species, which require pristine or late secondary forests to persist, and should consider a possible decline in species that may occur in secondary forests but would otherwise use mature forests, as well as declines in species which may feed in a variety of habitats but may not necessarily reproduce in all habitat types.
Keywords Dry tropical forest • Feeding guilds • Mexico • Neotropical birds • Secondary forests • Yucatan Peninsula
Old-growth forests throughout the tropics are increasingly reduced, fragmented, and degraded. Second-growth forests are increasing in extent and in importance for conservation and the provision of resources such as carbon and ecosystem services (Wright 2005). Previous studies have emphasized the importance not only of including the potential and costs of different land use/land cover alternatives on carbon sequestration but that also there is a need to study the impact of the resulting land cover changes on biodiversity (Mathews et al. 2002; Witt et al. 2011). A more comprehensive analysis of carbon sequestration by secondary forests in tropical dry forests would consider not only predictable profits but also the additional environmental benefits and costs associated with secondary forests.
Secondary forests are increasing in area around the world, and specifically in the tropics there is a high conversion rate from primary to secondary forests after abandonment of agriculture (Wright 2005). These forests are important for local, regional, and global processes, from the regulation of global carbon cycles (Achard et al. 2002) to the maintenance of species diversity (Brown and Lugo 1990). Particularly, tropical secondary forests are important in the conservation of animal species, particularly under conditions suitable for forest recovery (Dunn 2004). In tropical America there is an estimated area of 38 million hectares of secondary forests (ITTO 2002), where slash-and-burn shifting cultivation is one of the most widespread practices contributing to the conversion of natural forests to secondary forests (Raman et al. 1998). Tropical dry forests (TDF) in particular are among the most extensive land cover types in the tropics and the most threatened ecosystems in tropical America (Sanchez-Azofeifa et al. 2005; Quesada et al. 2009; Portillo – Quintero and Sanchez-Azofeifa 2010). Depending on their intensity, human activities produce a mosaic of secondary forest in different stages of succession or result in small forest remnants embedded in a matrix of agriculture or pasturelands.
Birds are widely known taxa with a large amount of available ecological information (Dunning 1992; Bird Life International 2011) and are commonly used in – conservation assessment and monitoring (Furness and Greenwood 1993; Mayer and Cameron 2003). Several studies have demonstrated that bird community structure in tropical rainforests is influenced by the changes in vegetation structure associated with succession (Raman et al. 1998; Raman and Sukumar 2002). In contrast and compared to other ecosystems, there is little ecological research on successional changes in bird communities in TDF (Leyequien et al., unpublished data). Moreover, successional vegetation patterns in TDF differ from those in humid forests in terms of species diversity, stem density, and convergence of plant species composition toward mature forest species (Lebrija-Trejos et al. 2008).
The rate at which animal communities recover during forest succession depends on landscape composition and configuration, which reflect habitat loss and fragmentation (Leyequien et al. 2010). In tropical forests, habitat loss and fragmentation affect bird communities through a decrease of suitable habitat and its degradation, the separation of habitat fragments by an anthropogenic matrix (e. g., croplands, pasturelands, urban areas), and by increasing edge effects (Arriaga – Weiss et al. 2008).
Feeding guilds are important to understand changes in animal community structure and functioning following a disturbance (Gray et al. 2007), such as the conversion of mature forests to agriculture and the subsequent forest succession after abandonment. There is evidence that different bird feeding guilds have dissimilar resilience to habitat disturbance (May 1982; Pearman 2002; Dunn 2004; Gray et al. 2007), and forest insectivores are especially at risk (Canaday 1996; Ford et al. 2001) because of their high sensitivity to habitat disturbance and fragmentation (Sekercioglu et al. 2002). For example, many bark insectivores are forest dependent and/or specialists in their foraging strategy (e. g., army ant-following species such as Dendrocincla, or feeding often at bromeliads such as Xiphorhynchus); although other bark insectivores are facultative feeders, as are woodpeckers, the majority need large trees for foraging and are not present in heavily deforested areas (Neotropical Birds Online 2011).
In Mexico, only 27 % of TDF remains undamaged, and the most extensive contiguous areas of TDF occur in the Yucatan Peninsula, where natural and human disturbances have produced an intricate landscape mosaic. Despite the prevalence of successional forests, few studies have examined their influence on higher trophic levels such as bird communities. The Yucatan Peninsula is a region of high avian endemism as well as an important area for migratory birds. This study examined the relative influence of successional age, vegetation structure, and landscape structure on bird guild composition in a TDF region in the Yucatan Peninsula, and thus under different potential carbon sequestration scenarios. We put a special emphasis on bark insectivores as they are a group vulnerable to habitat degradation.