Assessing land use/cover change in Costa Rica

The need for accurate estimates of forest cover and forest fragmentation is a critical issue for developing countries such as Costa Rica. Accurate estimates of forest cover can help in several sectors related to the environment and economic development. This dissertation focuses on providing an accurate and precise estimate of forest cover in Costa Rica. The year 1991 was used as a baseline. Landsat Thematic Mapper was the remote sensing sensor used in this analysis. This dissertation concludes that: (1) Twenty-nine percent ($\sim$1,400,000 ha) of the country was under primary forest (80% canopy closure) in 1991. Of the total forest cover, 71% is outside national parks and 29% is protected by the national parks. (2) Forest loss (for scene path 15/row 53) during five years period (1986-1991) was 224,970 ha, and it was estimated that the rate was $\sim$44,994 ha/yr. (3) Deforestation produced an increase in island fragments during the study period. Between 1986 and 1991, the total number of islands between three and 50 ha, and 50 and 100 ha increased by 524 and 45, respectively. Fifteen new islands with areas greater than 500 ha were created. (4) Results suggest that the extent of tropical deforestation go beyond estimations of total forest loss at the national level. The impacts at the national level have greater roots deeper roots when the data at the life zone level is considered. The results have important implication for biodiversity conservation and restoration, water resource management and climate change. The issue of partial sampling of remote sensing data base was also explored through this dissertation. Partial sampling is important for the definition of sound deforestation monitoring systems in tropical environments. A data set from the Brazilian Amazon was analyzed in order to understand how stratified sampling, using persistence, would improve estimates of tropical deforestation over random sampling. Results show that stratification based on persistence contributes to the reduction of error, regarding estimates of total deforestation, when contrasted against random sampling without stratification (FAO methodology). Results are important to future monitoring programs in Costa Rica and the Central American region

Local and Landscape Factors Determining Occurrence of Phyllostomid Bats in Tropical Secondary Forests

Neotropical forests are being increasingly replaced by a mosaic of patches of different successional stages, agricultural fields and pasture lands. Consequently, the identification of factors shaping the performance of taxa in anthropogenic landscapes is gaining importance, especially for taxa playing critical roles in ecosystem functioning. As phyllostomid bats provide important ecological services through seed dispersal, pollination and control of animal populations, in this study we assessed the relationships between phyllostomid occurrence and the variation in local and landscape level habitat attributes caused by disturbance. We mist-netted phyllostomids in 12 sites representing 4 successional stages of a tropical dry forest (initial, early, intermediate and late). We also quantitatively characterized the habitat attributes at the local (vegetation structure complexity) and the landscape level (forest cover, area and diversity of patches). Two focal scales were considered for landscape characterization: 500 and 1000 m. During 142 sampling nights, we captured 606 individuals representing 15 species and 4 broad guilds. Variation in phyllostomid assemblages, ensembles and populations was associated with variation in local and landscape habitat attributes, and this association was scale-dependent. Specifically, we found a marked guild-specific response, where the abundance of nectarivores tended to be negatively associated with the mean area of dry forest patches, while the abundance of frugivores was positively associated with the percentage of riparian forest. These results are explained by the prevalence of chiropterophilic species in the dry forest and of chiropterochorous species in the riparian forest. Our results indicate that different vegetation classes, as well as a multi-spatial scale approach must be considered for evaluating bat response to variation in landscape attributes. Moreover, for the long-term conservation of phyllostomids in anthropogenic landscapes, we must realize that the management of the habitat at the landscape level is as important as the conservation of particular forest fragments

Summary statistics of parameters at population, ensemble and assemblage-level.

<p>Parameters at population-level: capture rate (individuals/night) as indicator of species local abundance. Parameters at ensemble-level: rarified number of nectarivorous (S₈N) and frugivorous species (S₈F), capture rate of nectarivores (AbN) and frugivores (AbF). Parameters at assemblage-level: scores of the first (SC₁) and second (SC₂) ordination axis reflecting assemblage's dissimilarities in species composition and structure, rarified number of phyllostomid species (S₈P) and capture rate of phyllostomids (AbP). Mean: mean per site of the parameters at population, ensemble and assemblage-level. SD: standard deviation. Species in bold are those analyzed at the population-level. Species ensemble assignations are shown between parentheses: gleaning insectivores (GI), nectarivores (N), frugivores (F) and sanguivores (S). The number of sites sampled was 12 for all parameters except for three, which are marked with an asterisk. In these three parameters the site P1 was excluded from the analyses due to its low number of sampling nights.</p

Number of chiropterophylic and chiropterochoric species per plant family occurring in dry and riparian forest.

<p>A: chiropterophylic species, B: chiropterochoric species. Dry and riparian forests arerepresented by white and black bars respectively. The entire species' checklist of the Chamela-Cuixmala region, as well as detailed information on how it was generated, appear in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035228#pone.0035228.s004" target="_blank">Table S3</a>.</p

Relationships between population, ensemble and assemblage-level parameters and the habitat attributes.

<p>Parameter at population-level: species abundance. Parameters at ensemble-level: rarified number of nectarivorous (S₈N) and frugivorous species (S₈F), abundance of nectarivores (AbN) and frugivores (AbF). Parameters at assemblage-level: scores of the first (SC₁) and second ordination axis (SC₂) reflecting assemblage dissimilarities in species composition and structure, rarified number of phyllostomid species (S₈P) and abundance of phyllostomids (AbP). Habitat attributes: vegetation structural complexity (V_struct), mean area of dry (DF_area) and riparian forest patches (RF_area), percentage of riparian forest cover (RF_%) and diversity of patch types (Div). Negative relationships are shown in parentheses.</p

Classified image showing sampling sites and concentric focal scales.

<p>Circles around sampling sites represent the focal scales of 500 and 1000 m radii. Successional stages: pasture (P), early (E), intermediate (I) and late (L). Dry forest is colored light gray, whereas small areas of riparian forest are colored dark gray. The polygon encloses the area of the Chamela-Cuixmala Biosphere Reserve.</p

Phyllostomid bat occurence in successional stages of neotropical dry forests

Tropical dry forests (TDFs) are highly endangered tropical ecosystems being replaced by a complex mosaic of patches of different successional stages, agricultural fields and pasturelands. In this context, it is urgent to understand how taxa playing critical ecosystem roles respond to habitat modification. Because Phyllostomid bats provide important ecosystem services (e.g. facilitate gene flow among plant populations and promote forest regeneration), in this study we aimed to identify potential patterns on their response to TDF transformation in sites representing four different successional stages (initial, early, intermediate and late) in three Neotropical regions: México, Venezuela and Brazil. We evaluated bat occurrence at the species, ensemble (abundance) and assemblage level (species richness and composition, guild composition). We also evaluated how bat occurrence was modulated by the marked seasonality of TDFs. In general, we found high seasonal and regional specificities in phyllostomid occurrence, driven by specificities at species and guild levels. For example, highest frugivore abundance occurred in the early stage of the moistest TDF, while highest nectarivore abundance occurred in the same stage of the driest TDF. The high regional specificity of phyllostomid responses could arise from: (1) the distinctive environmental conditions of each region, (2) the specific behavior and ecological requirements of the regional bat species, (3) the composition, structure and phenological patterns of plant assemblages in the different stages, and (4) the regional landscape composition and configuration. We conclude that, in tropical seasonal environments, it is imperative to perform long-term studies considering seasonal variations in environmental conditions and plant phenology, as well as the role of landscape attributes. This approach will allow us to identify potential patterns in bat responses to habitat modification, which constitute an invaluable tool for not only bat biodiversity conservation but also for the conservation of the key ecological processes they provide

Summary of the tests evaluating seasonal variation at the assemblage level.

<p>Study sites are the same as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084572#pone-0084572-g001" target="_blank">Fig. 1</a>. For tests based on randomizations (composition and abundance) the standardized effect size is provided (Z = (Observed value – Expected value)/StDev of expected values). The Z-score quantifies, in units of standard deviation, the position of the observed metric within the simulated distribution. Significant relationships (p-value ≤0.05) appear in bold and marginally significant relationships (0.05). Structure: result of the Kolmogorov-Smirnov test evaluating seasonal changes in bat assemblages regarding their structure (species rank distribution). Detailed information about these analyses are presented in the method section.</p

Species richness estimated with the first-order jackknife estimator, per site and per season.

<p>Study regions: Chamela Cuixmala Biosphere Reserve in Mexico (A), Unidad de Producción Socialista Agropecuaria Piñero in Venezuela (B), and Mata Seca State Park in Brazil (C). Sampling sites representing different successional stages are: pastures (from P1 to P3), early (from E1 to E3), intermediate (from I1 to I3) and late stage (from L1 to L3). Seasons: rainy season (triangles) and dry season (circles). Error bars represent the ±95% confidence intervals.</p