Predictive sampling effort and species-area relationship models for estimating richness in fragmented landscapes (original) (raw)
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Forest Ecology and Management, 2022
Anthropogenic disturbance has dramatically degraded and reduced the extension of the temperate rainforests of southern South America, negatively affecting forest animals that depend on habitat attributes at local and landscape scales. We conducted a multi-scale assessment (from 1 to 4000 m) to understand better how local and landscape attributes influence forest animal abundance in an anthropogenic disturbance gradient. We selected five forest-dependent animal species to assess the effects of habitat alteration: an arboreal marsupial (Dromiciops gliroides) and four forest birds (Pteroptochos tarnii, Scytalopus magellanicus, Scelorchilus rubecula, and Sylviortho- rhynchus desmursii). We recorded forest animal abundances in four different habitat types (old-growth native, secondary, and logged native forests and forestry plantations). We measured local attributes in the field and characterized landscape attributes remotely. We evaluated marsupial abundance using camera traps and forest bird abundance using point counts, which were analyzed with Generalized Linear Mixed Models. Locally, canopy cover positively predicted marsupial abundance, while the number of fallen logs positively predicted bird abundance. At the landscape scale, native forest cover positively affected marsupial abundance, with significant effects at all levels. Conversely, plantation cover negatively affected forest bird abundance, while landscape heterogeneity negatively affected both groups. Our results showed that the abundance of the forest animals assessed here depends on multi-scale determinants. At the local scale, we advise greater canopy cover and maintaining woody debris. On the landscape scale, maintaining native forest cover should prioritize biodiversity management in the southern South America temperate forests. It is also crucial to control the expansion of forest plantations and reduce forest fragmentation to guarantee the persistence of forest-dependent species.
Patterns of small mammal diversity in fragments of subtropical Interior Atlantic Forest in eastern Paraguay, 2014
The deforestation of eastern Paraguay is a relatively recent phenomenon, starting as early as the 1940s. Assuming that larger forest fragments retain mechanisms and patterns of biodiversity resembling the original forests, understanding these patterns is valuable for comparative, management, and conservation purposes. In this study, I document diversity patterns in four of the largest reserves of subtropical rainforest in eastern Paraguay as part of a 3-year field study. Forty grids, totaling 31,600 trap nights per reserve, resulted in 19 captured species. Spearman correlations were used to understand effects of distance to edge, and various diversity metrics and multivariate analyses were implemented to compare assemblages between remnants. Trapping revealed an increase in biodiversity toward forest edges. Medium-sized remnants showed the highest diversity (D) and evenness (J). Statistically significant differences were found between and among forest fragments. Given that biodiversity includes both richness and abundances, high biodiversity metrics are not the best indicator for ecosystem “ health, ” as population explosions closer to edges result in greater biodiversity. More edge, more biodiversity. Thus, more emphasis needs to be given to understanding the natural history of native fauna and common assemblage patterns when addressing conservation and management strategies.
An empirical investigation of why species-area relationships overestimate species losses
It is generally assumed that, when natural habitat is converted to human-dominated land cover, such habitat is “lost” to its native species. Most literature assumes that species richness should vary as a function of remaining natural area, following the well-known species-area relationship (i.e. Classic-SAR). However, Classic-SARs have consistently over-estimated species losses resulting from conversion of natural forested land cover to human-dominated landscapes. Moreover, richness is sometimes a peaked function of remaining natural habitat. Recent studies propose modified SAR models based on species’ utilization of multiple habitat types, yet none fully explains a peaked species-area relationship. Here we evaluate the responses of total avian richness, forest bird richness, and open-habitat bird richness to remaining natural land cover within 991 quadrats, each 100 km2, across southern Ontario, Canada. Total bird species richness peaks at roughly 50% natural land cover. Richness of forest birds varies as a classic power function of forested area. In contrast, richness of birds that prefer open habitats does not increase monotonically with either natural- or human-dominated land cover. Richness of open-habitat species can be predicted when we partition human-dominated land cover into an “available human-dominated” component and “lost” habitat. Distinguishing three land cover types (natural, available human-dominated, and lost) can thus permit accurate predictions of species richness in landscapes with differing levels of natural habitat conversion.