Effects of Habitat Conversion on Ant Functional Groups: A Global Review

Conversion of natural to anthropogenic environments affects biodiversity, and the understanding of these impacts may be improved by assessing how different functional groups respond to such land conversion. We studied land conversion impacts on ant functional groups, as ants are ecologically important and respond well to various environmental changes. We hypothesized that conversion of natural to anthropogenic environments modifies the composition of functional groups, fostering generalist and opportunistic groups over specialist ones, with more responses of this type in tropical than in temperate regions. We recovered 412 papers from ISI Web of Science, of which we selected 17 studies, published between 1993 and 2018, that addressed our study’s question. We assessed whether each functional group responded positively or negatively to conversion of natural habitat into anthropogenic land uses and used Monte Carlo tests to assess significance. Ants were affected by natural habitat conversion into monoculture and polyculture and by the conversion of savannas and of tropical and subtropical forests. Land conversion affected six of the 13 functional groups assessed here. In the temperate zone, cryptic species, predators, subordinate Camponotini, cold-climate specialists and tropical-climate specialists were impaired, whereas hot-climate specialists were favored. In the tropics, land conversion negatively impacted fungus-growers and predators. In both climatic zones, several functional groups, mainly those with broad ecological niches, did not respond to land conversion. Our results corroborate that land conversion effects vary among ant functional groups and indicate that the ant fauna of temperate ecosystems may be more susceptible than that of tropical regions

Multi-scale mammal responses to agroforestry landscapes in the Brazilian Atlantic Forest: The conservation value of forest and traditional shade plantations

The future of tropical forest biodiversity will largely depend on human-modified landscapes. We investigated how medium- to large-bodied mammals respond to factors at local (habitat type), intermediate (land use heterogeneity, forest cover and human population density) and large spatial scales (overall forest cover) in agroforestry landscapes. We surveyed mammals using camera traps in traditional cacao agroforests (cabrucas), intensified cacao agroforests, and forest remnants within two large Atlantic Forest landscapes of southern Bahia, Brazil, representing both high and low forest cover. At the local scale, habitat types differed in their potential to harbour mammal species, with forest remnants and cabrucas showing high conservation value, mainly under contexts of high forest cover, whereas intensified cacao agroforests contained less diversified species assemblages in both landscapes. At intermediate scales, species richness increased with increasing forest cover around forest remnants and intensified cacao agroforests, but the opposite was observed in cabrucas. The effects of human population density were ubiquitous but species-dependent. At the largest scale, species richness was higher in the most forested landscape, highlighting the imperative of maintaining forest remnants to retain forest-dwelling mammals in human-dominated landscapes. We claim that mammal conservation strategies require a multi-scale approach and that no single strategy is likely to maximize persistence of all species. Some species can routinely use traditional agroforests, and a large fraction of mammal diversity can be maintained even if high canopy-cover agroforestry dominates the landscape. Nevertheless, forest patches and highly forested landscapes are essential to ensure the persistence of forest-dwelling and game species

Relationships between portable chlorophyll meter estimates for the red mangrove tree (Rhizophora mangle L.)

Several ecosystem processes and services provided by mangrove trees, such as the regulation of biogeochemical cycles, biological control, soil retention and protection against erosion, and especially CO2 assimilation and carbon storage are related to the photosynthetic process (Donato et al. 2011; Schaeffer-Novelli et al., 2016; Santos et al., 2017). Photosynthesis is directly related to chlorophyll present in the leaves, and assessment of chlorophyll concentrations may be used as an indicator of a plants’ physiological condition. Decreases in leaf chlorophyll concentrations occur in plants exposed to environmental stress, including stress caused by heavy metals (Chandra & Kang, 2016), nutrient deficiency (Kalaji et al., 2017), and petroleum pollution (Arellano et al., 2017), among others. Thus, estimates of chlorophyll concentrations may provide information on plant and ecosystem function (Heenkenda et al., 2015; Pastor-Guzman et al., 2015)

Spatial patterns of structural diversity across the boreal forest-tundra ecotone in Churchill, Canada

Published versionVegetation structural diversity, also called structural complexity, has great effects on biodiversity and ecological processes, with higher biodiversity often observed in areas with higher structural diversity. As for other ecological variables, structural diversity is spatially heterogeneous. Thus, quantifying its spatial heterogeneity may provide clues to the spatial variation in ecological processes. We studied the spatial patterns of structural diversity in two different environments, tundra and forest-tundra ecotone, near Churchill, MB, Canada. We sampled vegetation and quantified five types of structural diversity (ground cover, herbaceous plants, woody plants, all live plants, and deadwood) along five transects, with lengths of 81-227 m, and used wavelet analysis to assess the scales of spatial pattern. We also assessed the effects of soil pH, microtopography, elevation, and distance from lakes on structural diversity. In general, structural diversity was spatially structured on a variety of scales, from 2 to 55 m, with larger scales being observed in the tundra than in the ecotone transects. In addition, structural diversity in the tundra was generally higher near lakes and in areas with a higher pH, whereas in the ecotone it increased mostly with increasing pH and microtopographic variation. Spatial heterogeneity is an important characteristic of the forest-tundra ecotone and even tundra areas that appear homogeneous are structurally diverse at a variety of scales

Patterns of shrub abundance and relationships with other plant types within the forest–tundra ecotone in northern Canada

Published VersionThroughout the forest–tundra ecotone where trees and tall shrubs are becoming more abundant, knowledge of associations between shrubs and surrounding vegetation could inform predictions of their changing relationships. We assessed shrubs in 1 m × 1 m contiguous quadrats along two ∼450 m transects across tundra and ecotone landscapes near Churchill, Canada to determine patterns in relation to lakeshore edges, soil pH, microtopography, and other plant groups. We used wavelet analysis to assess patterns and generalized least squares for relationships with environmental variables. Shrubs were taller and more diverse at edges, particularly in tundra. The ecotone was more complex than tundra with greater variation in tall shrub and tree cover, shrub height, and microtopography. Shrub richness was positively correlated with microtopography but exhibited no relationship with pH. Bivariate relationships of shrubs with other plant groups varied for different scales. In tundra, shrub richness was negatively correlated with graminoids, forbs, and moss, but positively correlated with lichens within 1 m; opposite relationships were found at 4–60 m scales. Relationships in the ecotone were reversed and more complex at different scales. As trees encroach in the tundra, the spatial pattern of shrubs will become more complex at a variety of scales, likely with cascading effects on other plant types

Berry phase in magnetic systems with point perturbations

We study a two-dimensional charged particle interacting with a magnetic field, in general non-homogeneous, perpendicular to the plane, a confining potential, and a point interaction. If the latter moves adiabatically along a loop the state corresponding to an isolated eigenvalue acquires a Berry phase. We derive an expression for it and evaluate it in several examples such as a homogeneous field, a magnetic whisker, a particle confined at a ring or in quantum dots, a parabolic and a zero-range one. We also discuss the behavior of the lowest Landau level in this setting obtaining an explicit example of the Wilczek-Zee phase for an infinitely degenerated eigenvalue.Comment: LaTeX, 26 page

The role of edge contrast and forest structure in edge influence: vegetation and microclimate at edges in the Brazilian cerrado

Accepted VersionThe effect of the adjacent non-forested environment on the forest near the edge, edge influence (EI), is an important impact in fragmented landscapes and is believed to vary with factors such as forest structure and edge contrast. In order to improve our understanding of the factors governing the variability in EI, we studied microclimate and vegetation at cerrado edges surrounded by variable land uses in southeastern Brazil, a system with both forest and savanna fragments. We determined the significance, magnitude and distance of EI on microclimate, vegetation structure and grass biomass which we measured along five transects perpendicular to fourteen edges in forest or savanna next to different land uses. We introduce a quantitative measure of edge contrast that considers land uses at different distances from the same edge (e.g., a firebreak between a forest edge and a plantation) and verified whether edge contrast is correlated with EI in this system. Notwithstanding the large variation in EI among variables and study sites, there were some similarities in the patterns of EI between forest and savanna edges. Edge contrast was successfully quantified by our measure but was only correlated with EI on moisture and grass biomass. Our results point to the high variability in EI within a region. Our quantitative measure of edge contrast may be useful in explaining variability in EI. However, much unexplained variation remains in the highly fragmented cerrado system which is affected by EI in both forest and savanna fragments

Avaliação in situ do aporte de alimento nas diferentes zonas de uma caverna: estudo de caso e recomendações metodológicas

Due to the absence of light, cave environments are devoid of photosynthesizing organisms, and depend on the input of food from above ground. We compared the quantity of food available in the different zones of two caves in Serra da Canastra, MG. The amount of plant debris was highest in the entrance zone, intermediate in the twilight zone, and minimal in the dark zone. Guano was practically absent from the entrance zone, but did not present any clear pattern between the twilight and the dark zones. Therefore, plant debris seem to be more important in the entrance zone, and guano in deeper zones. We conclude with some methodological recommendations related to the quantification of food input and to statistical inference.Devido à ausência de luz, ambientes cavernícolas são desprovidos de organismos fotossintetizantes, e dependem do aporte de alimento a partir do meio epígeo. Nós comparamos a quantidade de alimento disponível nas diferentes zonas de duas cavernas na região da Serra da Canastra, MG. A quantidade de detritos vegetais era máxima na zona de entrada, intermediária na zona de penumbra, e mínima na zona afótica. O guano esteve praticamente ausente na zona de entrada, mas sem apresentar padrões claros entre as zonas de penumbra e afótica. Assim, os detritos vegetais parecem ser mais importantes na zona de entrada, e o guano em zonas mais profundas. Concluímos o artigo com algumas recomendações metodológicas relacionadas à quantificação do aporte e à inferência estatística

Spatial pattern of invasive and native graminoids in the Brazilian cerrado

Accepted versionInvasive grasses are an important threat in tropical savannas and grasslands and may be affected by natural and anthropogenic features of the environment. They may affect native species at a variety of scales, but a spatially-explicit assessment of their effects is lacking. We studied the spatial pattern of native and invasive graminoids in Brazilian cerrado in southeastern Brazil and assessed the effects of vegetation type, elevation and edges. We sampled native grasses, native sedges, and two invasive grass species (Urochloa decumbens and Melinis minutiflora) along three 301 to 1334 m-long transects encompassing grassland, forest, and savanna. We used wavelet transforms, generalized additive models, and null model simulations for analysis. Invasive grasses were mostly found in open vegetation. Neither native nor invasive species were consistently affected by elevation or edges. Much of the spatial variation could be explained by small-scale autocorrelation, but M. minutiflora had a more heterogeneous pattern than U. decumbens. Invasive grasses were negatively related to native ones at a variety of scales, from 1 to 66 m, and we observed both positive and negative relations between the two invasive species, with positive ones a finer scales. We hypothesize that spatial pattern characteristics of different invasive species may be related to their invasion potential