Habitat associations of saplings and adults in an old-growth temperate forest in the Changbai mountains, northeastern China

Species-habitat association analysis is useful to detect spatial arrangement of individual plants, to discover rules about the distribution of species and to generate hypotheses about the possible underlying process controlling observed structures. Quantifying methods were used to classify habitats in terms of topographical variables in a mixed temperate broad-leaved Korean pine forest of the Changbai mountains in northeastern China. All of the 625 20 m × 20 m quadrats of the plot could be unambiguously assigned to one of three habitat categories （low-plateau, high-plateau and slope）. Torus-translation tests were used to estimate species-habitat associations. Many species are clearly distributed in a biased fashion with respect to habitats. Fifteen （55.6%） out of 27 species showed strong positive or negative association with specific habitats. We compared species-habitat associations at the sapling and adult stages. Adjusted density values indicated few species exhibit extremely strong habitat associations. Only 9 out of 26 species had adjusted densities 〉 3 in the habitat for which they had strong positive affinity. Few species show the same associations at the small tree and large tree stages. Only 3 out of 22 occurring associations with a specific habitat appeared to have a consistent habitat association at the two stages. These results suggest that species-habitat associations exist in the 25-ha plot of the temperate forest of the Chang- bai mountains. Owing to limitations in our statistical methodology, we partly underestimated associations by ignoring rare species. Regeneration niches can contribute to co-existence, but regeneration niches due to habitat associations play a limited role in species co-existence, since most species show a similar trend in habitat associations at the sapling and adult stages. We should pay more attention to shifts in habitat associations, i.e. niche shifts at different stages of existence.

Fine-scale habitat differentiation shapes the composition, structure and aboveground biomass but not species richness of a tropical Atlantic forest

Evaluating the influences of fine-scale habitat heterogeneity on the composition,diversity,structure and functioning of forests is critical to understand how tropical forests will respond to climate change and devise forest management strategies that will enhance biodiversity conservation and aboveground biomass stock.Here,we hypothesized that topographic and soil factors determine fine-scale habitat differentiation,which in turn shape community composition,species richness,structure and aboveground biomass at the local scale in tropical forests.To test this hypothesis,we selected two areas(each 100×100 m)with contrasting fine-scale topographic conditions where all trees,palms and lianas with a diameter at breast height ≥ 10 cm were tagged and identified to species.In each selected area,100 subplots of 10×10 m were established.We mainly found that higher topographic variability caused higher habitat differentiation with changes in species composition and community structure,but did not change species richness.Our habitat-scale analyses indicated that,in the less heterogeneous area,the distribution of species was more uniform along a fine-scale topographical gradient with no variation in convexity,which induced changes in structure and aboveground biomass,but not in species richness.The nonsignificant relationship between species richness and aboveground biomass may be attributable to species redundancy or functional dominance.This study suggests that environmental filtering is a fundamental process for shaping community assembly and forest functioning along a local topographical gradient in tropical forests.

Waterbirds in the Wetlands of Casiguran, Aurora, Philippines

The wetlands of Casiguran, Aurora, Philippines are primarily the source of livelihood for most of the coastal communities of the area. However, this also serves as a feeding ground for many of the migratory and resident waterbirds. There are waterbird species occurring in the area that need protection but only a few studies of these species exist. This study was conducted from February to March 2019 to census and identify the water birds present in the study site, determine the conservation status and index of abundance of identified waterbirds, and describe their habitat association. Based on the result, 18 waterbird species in five families were present in the area. Family Ardeidae had six representative species, Family Charadriidae had five representative species, Family Scolopacidae had five representative species while only one species represents the Family Anatidae and Family Rallidae. Two waterbird species observed (Anas luzonica and Egretta eulophotes) were listed by the International Union for Conservation of Nature (IUCN) as vulnerable and another species (Numerius madagascariensis) was listed as endangered. In terms of abundance, Intermediate Egret (Egretta intermedia) was revealed as the most abundant (94.68%) among waterbirds. Different waterbird species prefer specific habitats. Some usually frequent freshwater and saltwater habitats, including mangroves, open sea, and watercourses inside forests while some were observed in mudflats, and rice fields during the survey.

Habitat specialization and phylogenetic structure of tree species in a coastal Brazilian white-sand forest

Aims The coastal Brazilian rainforest on white-sand(restinga)ranks among the most fragmented forest types in the tropics,owing to both the patchy distribution of sandy soils and widespread coastal development activities.Here we study the environmental and evolutionary determinants of a forest tree assemblage at a single restinga forest in Southeastern Brazil.We also explore the ability of competing hypotheses to explain the maintenance of species diversity in this forest type,which includes contrasting extremes of edaphic conditions associated with flooding stress.Methods The study was conducted in a white-sand forest permanent plot of 10.24 ha on the coastal plain of Southeastern Brazil.This plot was divided into 256 quadrats of 20×20 m,which were classified into two main edaphic habitats(flooded and drained).Trees with a diameter≥1 cm at breast height were identified.We assembled DNA sequence data for each of the 116 morphospecies recognized using two chloroplast markers(rbcL and matK).A phylogenetic tree was obtained using the maximum likelihood method,and a phylogenetic distance matrix was produced from an ultrametric tree.We analyzed similarity in floristic composition and structure between habitats and related them to cross-plot distances using permutation procedures.Null model torus shift simulations were performed to obtain a statistical significance level for habitat association for each species.The phylogenetic structure for the two habitats and for each 20×20 m quadrat was calculated using the mean phylogenetic distance weighted by species abundance and checked for significance using the standardized effect size generated by 5000 randomizations of phylogenetic tip labels.Important Findings Our results indicate that partitioning among edaphic habitats is important for explaining species distributions and coexistence in restinga forests.Species distributions within the plot were found to be non-random:there was greater floristic similarity within than between habitats,and>40%of the more abundant species were positively or negatively associated with at least one habitat.Patterns of habitat association were not independent of phylogenetic relatedness:the community was overdispersed with respect to space and habitat type.Closely related species tended to occur in different habitats,while neighboring trees tended to belong to more distantly related species.We conclude that habitat specialization is important for the coexistence of species in restinga forests and that habitat heterogeneity is therefore an essential factor in explaining the maintenance of diversity of this unique but fragile and threatened type of forest.