Endemic Avifauna in Caraga – the mining capital of Mindanao Island, Philippines: their preferred habitats and threats

Caraga Region comprises most of the Eastern Mindanao Biodiversity Corridor in the Philippines which is known to be the center of endemism. However, it is popularly known as the “Mining Hub” in Mindanao Island where there is obvious overlapping of mining concessions with the remaining blocks of tropical rainforests. Habitat preference of endemic avifauna and their threats are least studied in the region. Hence, in this study, habitat characteristics across habitat types and responses of endemic birds to habitat alterations were assessed in four selected mining areas (Masabong and Philsaga in Rosario and Bunawan, Agusan del Sur and Claver, Surigao del Norte) using Canonical Correspondence Analysis, survival envelope, niche position and niche width analyses. High suitability areas in Caraga that potentially harbor viable populations of endemic birds and suitable habitats for the key forest-dependent endemic birds across the landscape were also predicted using species distribution modeling. Among the four selected mine sites in Caraga, Masabong and Claver are good representation of forest ecosystem, while Bunawan and Philsaga are dominated by agro-forests and cultivated areas. A total of 47 endemic birds were encountered in four selected key mine areas of Caraga. Fifty of which are Philippine-endemics (four are near-threatened, three vulnerable and one endangered) and seven of them are Mindanao-endemics (one near-threatened and three vulnerable). Most of the endemic birds prefer advance secondary forests especially the threatened endemics. Some can tolerate regenerating forests but not in the non-forest habitat e.g. cultivation and open, degraded areas which implies sensitivity to forest fragmentation. Most of the predicted high conservation value areas for forest-dependent endemic birds are overlapping with mining concessions and expanding perennial crop plantations. Failure to do effective policy reform and law enforcement in regulating land-use changes in Caraga will most likely compromise the niche requirements of the endemic bird specialists.peerReviewe

Data from: Factors determining forest diversity and biomass on a tropical volcano, Mt. Rinjani, Lombok, Indonesia

Tropical volcanoes are an important but understudied ecosystem, and the relationships between plant species diversity and compositional change and elevation may differ from mountains created by uplift, because of their younger and more homogeneous soils. We sampled vegetation over an altitudinal gradient on Mt. Rinjani, Lombok, Indonesia. We modeled alpha- (plot) and beta- (among plot) diversity (Fisher’s alpha), compositional change, and biomass against elevation and selected covariates. We also examined community phylogenetic structure across the elevational gradient. We recorded 902 trees and shrubs among 92 species, and 67 species of ground-cover plants. For understorey, subcanopy and canopy plants, an increase in elevation was associated with a decline in alpha-diversity, whereas data for ground-cover plants suggested a hump-shaped pattern. Elevation was consistently the most important factor in determining alpha-diversity for all components. The alpha-diversity of ground-cover vegetation was also negatively correlated with leaf area index, which suggests low light conditions in the understorey may limit diversity at lower elevations. Beta-diversity increased with elevation for ground-cover plants and declined at higher elevations for other components of the vegetation. However, statistical power was low and we could not resolve the relative importance to beta-diversity of different factors. Multivariate GLMs of variation in community composition among plots explained 67.05%, 27.63%, 18.24%, and 19.80% of the variation (deviance) for ground-cover, understorey, subcanopy and canopy plants, respectively, and demonstrated that elevation was a consistently important factor in determining community composition. Above-ground biomass showed no significant pattern with elevation and was also not significantly associated with alpha-diversity. At lower elevations communities had a random phylogenetic structure, but from 1600 m communities were phylogenetically clustered. This suggests a greater role of environmental filtering at higher elevations, and thus provides a possible explanation for the observed decline in diversity with elevation

final Rscript Rinjani

R script for analyse

Factors Determining Forest Diversity and Biomass on a Tropical Volcano, Mt. Rinjani, Lombok, Indonesia

<div><p>Tropical volcanoes are an important but understudied ecosystem, and the relationships between plant species diversity and compositional change and elevation may differ from mountains created by uplift, because of their younger and more homogeneous soils. We sampled vegetation over an altitudinal gradient on Mt. Rinjani, Lombok, Indonesia. We modeled alpha- (plot) and beta- (among plot) diversity (Fisher's alpha), compositional change, and biomass against elevation and selected covariates. We also examined community phylogenetic structure across the elevational gradient. We recorded 902 trees and shrubs among 92 species, and 67 species of ground-cover plants. For understorey, subcanopy and canopy plants, an increase in elevation was associated with a decline in alpha-diversity, whereas data for ground-cover plants suggested a hump-shaped pattern. Elevation was consistently the most important factor in determining alpha-diversity for all components. The alpha-diversity of ground-cover vegetation was also negatively correlated with leaf area index, which suggests low light conditions in the understorey may limit diversity at lower elevations. Beta-diversity increased with elevation for ground-cover plants and declined at higher elevations for other components of the vegetation. However, statistical power was low and we could not resolve the relative importance to beta-diversity of different factors. Multivariate GLMs of variation in community composition among plots explained 67.05%, 27.63%, 18.24%, and 19.80% of the variation (deviance) for ground-cover, understorey, subcanopy and canopy plants, respectively, and demonstrated that elevation was a consistently important factor in determining community composition. Above-ground biomass showed no significant pattern with elevation and was also not significantly associated with alpha-diversity. At lower elevations communities had a random phylogenetic structure, but from 1600 m communities were phylogenetically clustered. This suggests a greater role of environmental filtering at higher elevations, and thus provides a possible explanation for the observed decline in diversity with elevation.</p></div

Phylogenetic community structure among vegetation plots along an elevational gradient on Mount Rinjani, Indonesia.

<p>(MPD = mean phylogenetic distance (observed and expected±standard deviation); NRI = net relatedness index).</p

Map of the Island of Lombok and Mt. Rinjani, the study site, and the sample design.

<p>It was not possible to sample vegetation below 1000 m because of human disturbance and above 2000 m were fire-maintained grasslands. Access was only possible through using the main hiking trail on the north slope of the mountain.</p

Relationships between elevation and beta-diversity (among plots with elevation stations) for different components of vegetation on Mount Rinjani, Indonesia.

<p>(A) ground-cover plants (y = 6.92+2.06x), (B) understorey plants (y = 10-4.2x-4.04x², all stations 2200 m included), (C) subcanopy plants (y = 4.62-2.32x), (D) canopy plants. Solid lines indicate relationships including all elevation stations and the dashed lines indicate the relationships when the station at 2200 m (fire-maintained grassland) was omitted. Only relationships that were significant (<i>p</i><0.05) in univariate regression models are shown.</p

Relationships between elevation and slope, and between elevation and various components of forest structure on Mount Rinjani, Indonesia.

<p>A) slope, B) canopy height (y = 38.19+0.01x, R² = 0.21), C) LAI, D) basal area, E) tree density, where filled circles are for subcanopy trees (y-axis on left, y = 3.68+0.05x, R² = 0.25) and open circles are for canopy trees (y-axis on right, y = 12.39-0.48x-14.62x², R² = 0.33), and F) canopy openness. Solid lines indicate relationships including all elevation stations and the dashed lines indicate the relationships when the station at 2200 m (fire-maintained grassland) was omitted. Only significant (<i>p</i><0.05) relationships are shown. The non-zero woody biomass and canopy height for the grassland station (2200 m) are because there were small numbers of isolated trees.</p

Relationships between above ground biomass and (A) elevation (y = 18.81-11.35x-14.32 x², R² = 0.35, all stations 2200 m included), and (B) diversity (fisher's alpha) of subcanopy and canopy vegetation combined on Mount Rinjani, Indonesia.

<p>Solid lines indicate relationships including all elevation stations and the dashed lines indicate relationships when the station at 2200 m (fire-maintained grassland) was omitted. Only significant (<i>p</i><0.05) relationships are shown.</p

Summary of the relative importance of factors in determining alpha- and beta-diversity (Fisher's alpha) of vegetation along an elevational gradient on Mt Rinjani, Indonesia.

<p>Values were derived through a model averaging approach (<i>model.avg</i> function in MuMIn package). The variables included were slope, leaf area index and elevation and their interactive terms (2200 m station not included). For elevation we examined whether a linear or polynomial expression best fitted our data. Gr = ground-cover plants, Un = understory plants, Su = subcanopy plants, and Ca = canopy plants. Factors with parameters values that were significantly different from zero (p<0.05) are highlighted in bold.</p>*<p>denotes that the polynomial relationship of elevation was selected; anywhere else only linear relationship was selected.</p