Neotropical dry forest recovery and its impact on the avian community

• Author / Creator

  Hilje Rodriguez, Branko

• Neotropical dry forests are severely threatened by human activities such as agricultural expansion, tourism, cattle ranching, logging, and an increase in human settlements. However, despite these trends, some countries have experienced forest recovery. Costa Rica is a clear example of this process, and dry forests in the country have recovered more than 50 % of their area in the last 50 years as a result of changes in socio-economic and conservation policies. Costa Rica currently holds the largest protected remnant of dry forest in Central America. Despite this success, information on the recovery of the forest structure, vegetation species composition, and fauna of successional forests (e.g. forests that are recovering or have recovered from the effects of clear-cutting and burning) is lacking. This Dissertation assessed the recovery of Neotropical dry forests and its impact on the avian community. Species composition of the bird community was evaluated in forests at different stages of recovery following the abandonment of cattle ranching in the largest protected tropical dry forest remnant in Central America (at the Santa Rosa National Park, Costa Rica). Chapter 2 described and compared tree species diversity and composition in three different dry forest successional stages (e.g. early, intermediate, and late), as well as the breeding systems and pollination and dispersal syndromes for the species. Findings showed that monoecy (e.g. having unisexual reproductive flowers on a single plant) was the most common tree breeding system, so tree species do not depend on specific fauna pollinators. Insects were very important tree pollinators for all successional stages, but the wind is the most important pollination and dispersal agent in open sites in early successional stages where animals are scarce. In contrast, birds and mammals are important seed dispersers in the intermediate and late stages of dry forest succession. Chapter 3 evaluated the influence of liana abundance on the avian acoustic community in tropical dry forests. Results showed that the avian community increases in diversity when the number of lianas at a site increases, suggesting that lianas provide important resources for birds (e.g. food and structure for shelter, nesting and roosting). Even though lianas have been reported to have a negative effect on the reproduction of tropical canopy trees, and probably on the species composition of forest faunas, a positive
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  relationship between the occurrence of lianas and bird diversity was determined. This relationship is important in dry forests due to the role of birds as tree pollinators and seed dispersal agents in areas where lianas have become highly abundant. Chapter 4 assessed changes in bird species richness and community composition in dry forests at different ages of recovery since abandonment (e.g. 20, 30, 40, and 60 years old). A similar species richness and avian community composition were observed in forests of different ages (e.g. 20, 30, 40, and 60 years). This probably reflects (a) the similarities in the structural characteristics of forests of different ages, and (b) the high variation in forest structure within each age group. As a result, birds can find suitable habitats and other key resources such as perches, nesting material, and food from all the different forest sites that were studied. This highlights a rapid recovery of bird species composition in the TDFs studied, and information generated from this study can be considered in bird conservation efforts in Neotropical dry forests.

• Subjects / Keywords

  • dry forest
  • forest recovery
  • succession
  • lianas
  • birds
  • acoustics
  • tree pollination and dispersal syndromes

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3319SJ5N

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.