Subtropical Atlantic Forest Research Articles

Stand structure and Brazilian pine as key determinants of carbon stock in a subtropical Atlantic forest.

Understanding the drivers of variations in carbon stocks is essential for developing the effective management strategies that contribute to mitigating climate change. Although a positive relationship between biodiversity and the aboveground carbon (AGC) has been widely reported for various Brazilian forest types, representing a win-win scenario for climate change mitigation, this association has not been commonly found in Brazilian subtropical forests. Therefore, in the present study, we aimed to evaluate the effects of Araucaria angustifolia, stand structure and species diversity in shaping AGC stocks in Brazilian subtropical mixed forest. We hypothesized that the effects on the AGC of stand structure and diversity would be mediated by A. angustifolia. We also evaluated the expectation of higher carbon stocks in protected forest as a result of their positive correlation with biodiversity conservation. We found that stand structure, followed by A. angustifolia, played the most important role in shaping the AGC stock. Our hypothesis was partially confirmed, the indirect effects of A. angustifolia on stand structure being found to have shaped the AGC. Similarly, our expectation was partially supported, with the higher AGC in the protected area being related not to diversity, but rather to the presence of larger trees, denser stands, and a greater abundance of A. angustifolia. Although the win-win strategy between diversity conservation and carbon storage is not a peculiarity of Araucaria forests, we highlight the potential of these forests as a nature-based climate solution, maintaining high levels of carbon storage in harmony with the provision of keystone socio-economic resources.

Spatial patterns of damage and tree mortality in a selectively logged Atlantic Forest

Selective logging, a common disturbance in mixed-species and uneven-aged forests, can cause substantial collateral stand damage and tree mortality. Here we explore damage patterns and some mechanisms that increase post-harvest tree mortality in a selectively logged subtropical Atlantic Forest in Argentina. We investigate the spatial relations of felled and damaged trees through spatial point pattern analysis and evaluate the relationships between mortality and different endogenous (size - diameter at breast height: DBH; and wood density: WD) and exogenous (damage and neighboring basal area: NBA) factors. The permanent plots were logged in 1999, and the fates of all pre-logging live trees ≥10 cm DBH were evaluated 20 years later. Of the monitored 3973 trees, 381 with damaged concentrated within 10.5 m of felled tree stumps. Over the next twenty years mean mortality was higher and more variable for damaged than undamaged trees (47 % ± 10 % SE and 39 % ± 2 % SE, respectively), and the presence of damage interacted with the other analyzed factors. For undamaged trees, the probability of mortality declined with DBH and NBA but not with WD. For damaged trees, instead, the probability of mortality was related to an interaction between DBH, WD, and NBA. For damaged trees <30 cm DBH, mortality increased with WD and NBA, whereas for damaged trees ≥30 cm DBH, mortality peaked at both extremes of the WD range. For these large trees with low WD, the probability of mortality decreased with NBA, whereas for trees with high WD, the opposite was observed. Our findings suggest that selective logging affects the dynamics of forests by spatially concentrating damage and may alter subsequent tree deaths. This could have, long-term effects on forest structure. Increases in logging intensity would increase overall damage and spatially isolate trees (i.e., lower NBA), rendering them more vulnerable to wind damage and other external factors. Increased tree mortality will reduce forest carbon stocks and thereby jeopardize global efforts to mitigate climate change.

Ecological inferences in Orchidaceae species from the Brazilian subtropical Atlantic Forest based on morphological and functional anatomical traits

Ecological anatomy studies seek to link structural aspects to environmental pressures, improving knowledge about the occurrence and distribution of species. Orchidaceae is a group with high species richness and ecological diversity, well represented in the Brazilian Atlantic Forest, a biodiversity hotspot. The Iguaçu National Park (ParNa Iguaçu) is an important remnant of the southern Brazilian Atlantic Forest with a high richness of Orchidaceae. Given the family's diversity and the relevance of ecological anatomy studies for interpreting traits associated with the survival of plants in certain environments, we studied 38 species of Orchidaceae from ParNa Iguaçu, seeking to identify possible functional groups. For this, we surveyed 57 leaf morpho-anatomical characters and conducted histochemical and statistical tests. The morpho-anatomical traits group the species into two functional groups, with Cyclopogon congestus emerging isolated. In group A, xeromorphic morphoanatomical characters predominate, and group B combines members with meso/hygromorphic characteristics. We advocate the importance of understanding the ecological behavior of species, especially Orchidaceae, due to their important ecological role, in conservation actions in protected areas. Furthermore, our results highlight the morphological and anatomical diversity of the Orchidaceae found in ParNa Iguaçu, as well contributing to the development of better management practices for these plants, considering the threats posed by the opening of clearings and climate change.

Mixed effects of climate and species richness on aboveground carbon stock in subtropical Atlantic forests

Tropical forests are global biodiversity hotspots and are crucial in the global carbon (C) cycle. Understanding the drivers of aboveground carbon stock (AGC) in a heterogeneous and biodiverse system can shed light on the processes underlying the relationship between biodiversity and carbon accumulation. Here, we investigate how biodiversity, environment, and landscape structure affect AGC. We examined such associations in 349 plots comprising over 95,346 km2 the Atlantic Forest of southern Brazil, encompassing three forest types: Dense Ombrophylous Forest (DF), Mixed Ombrophylous Forest (MF), and Seasonal Deciduous Forest (SF). Each plot was described by environmental variables, landscape metrics, and biodiversity (species richness and functional diversity). We used diversity, environmental, and landscape variables to build generalized linear mixed models and understand which can affect the forest AGC. We found that species richness is associated positively with AGC in all forest types, combined and separately. Seasonal temperature and isothermality affect AGC in all forest types; additionally, stocks are positively influenced by annual precipitation in SF and isothermality in MF. Among landscape metrics, total fragment edge negatively affects carbon stocks in MF. Our results show the importance of species diversity for carbon stocks in subtropical forests. The climate effect was also relevant, showing the importance of these factors, especially in a world where climate change tends to affect forest stock capacity negatively.

Climate sensitive tree growth modelling of Myrocarpus frondosus in Southern Brazil using tree-ring time series and distributed generalized additive lag models

Abstract Climate change is expected to strongly affect the functioning of tropical and subtropical forest ecosystems around the globe, and tree-ring analysis is proving increasingly useful for understanding the changing dynamics in these environments. However, traditional dendroecological methods were not originally designed to jointly consider inter-annual and inter-tree variations, often assuming linear growth-climate relationships, and limiting the potential to address in-deep questions regarding the tree growth sensitivity to environmental drivers. In the present study, we applied a flexible generalized additive model to assess the climate-sensitivity of the species Myrocarpus frondosus Allemão growing in a subtropical Atlantic Forest (AF) site in southern Brazil. Tree-ring width time series from 117 stem cores together with monthly climate data of temperature and precipitation covering the period from 1968 to 2021 were used for model construction. The model was designed to simultaneously encompass detrending, to capture nonlinear effects of climate variables and their interactions and to predict mean tree-ring widths for the species. Based on a distributed lag model approach, we also tested the influence of different lengths of lagged climate series over the model accuracy. Both precipitation and temperature proved to be strong drivers of M. frondosus radial growth in the subtropical AF. An interaction effect between these regressor variables revealed a likely water stress scenario arising from warm and dry summer conditions, with strongly negative impacts for the species. Detrimental impacts on tree dormancy period can also be expected due to milder winters, with legacy effects on the radial increments across two subsequent years. In addition to monitoring, the approach applied here meets the needs for more robust predictions of the impacts of future climate conditions on species and communities, contributing to efforts aimed at the management and conservation in tropical and subtropical ecosystems, particularly in the AF.

Commonness as a reliable surrogacy strategy for the conservation planning of rare tree species in the subtropical Atlantic Forest

Commonness as a reliable surrogacy strategy for the conservation planning of rare tree species in the subtropical Atlantic Forest

Land management of formerly subtropical Atlantic Forest reduces soil carbon stocks and alters microbial community structure and function

Soil carbon (C) sequestration has been proposed as one means to mitigate the effects of climate change and to guarantee food safety. However, forest conversion to managed land uses can deplete soil C stocks and affect soil microbial communities, potentially impacting a wide range of ecosystem services. Our objective was to investigate the effect of forest conversion to intensive land uses on soil C dynamics and soil microbial community structure and function in the subtropical portion of the Atlantic Forest biome. We evaluated four land uses - forest fragment, grassland, and agriculture with five or fifty years of cultivation. We analyzed soil C pools, edaphic variables, and soil bacterial/archaeal (16S) and fungal (ITS) communities. Forest conversion to managed land uses reduced soil C stocks and altered soil microbial community structure, with implications for soil C dynamics. Bacterial/archaeal and fungal community composition were strongly correlated with pH, base saturation, and calcium (Ca) and magnesium (Mg) content. However, soil C pools were not associated with potential extracellular enzyme activity or microbial diversity. Finally, the fungal species Mortierella minutissima ASV_1 and several bacterial groups were positively correlated with soil C stocks, potentially representing indicators of soil C storage. Our study indicates that land use change affects the interplay between soil microbial communities and soil C pools, with consequences to soil C storage. Our findings may support the development of soil C enhancement programs within the Atlantic Forest biome.

Diversity, species coexistence and functional composition patterns in subtropical Atlantic Forests invaded by non‐native trees

Resumo Invasões biológicas são um grande desafio ambiental atualmente. Interações entre espécies invasoras e nativas podem moldar significativamente as estruturas da comunidade, influenciando a coexistência, diversidade e composição funcional das espécies. A Floresta Atlântica subtropical no sul do Brasil, um reconhecido hotspot de biodiversidade, oferece um cenário único para estudar essas interações, dada sua vulnerabilidade às invasões de árvores exóticas. Nosso estudo buscou elucidar os impactos dessas invasões neste ecossistema frágil, abordando questões‐chave: (1) Como os padrões de diversidade da comunidade arbórea são afetados pela abundância de espécies exóticas invasoras? (2) Quais são os padrões de coexistência entre árvores nativas e exóticas invasoras? (3) A composição funcional das florestas é alterada pela abundância de árvores invasoras? Para abordar essas questões, compilamos dados sobre a abundância e características funcionais de árvores nativas e invasoras. Determinamos os padrões de diversidade e composição funcional de parcelas com diferentes graus de invasão. Estes dados foram analisados usando Modelos Lineares Mistos Generalizados, Análise de Componentes Principais e um índice de coexistência. Em parcelas com maior abundância de árvores invasoras, houve uma diminuição significativa na riqueza taxonômica e funcional das espécies nativas. Além disso, observamos que árvores exóticas invasoras coexistiam com espécies nativas, e à medida que a abundância de árvores invasoras aumentava, a média ponderada da comunidade nativa (CWM) da área foliar e da área foliar específica diminuía. Em conclusão, nas áreas da Floresta Atlântica subtropical do sul do Brasil, nossos achados destacam que a abundância de árvores invasoras afeta adversamente a riqueza taxonômica e funcional das espécies nativas. Além disso, enquanto árvores exóticas invasoras foram encontradas coexistindo com espécies nativas, o aumento da abundância invasora correspondeu a uma redução na área foliar e na área foliar específica da comunidade nativa.

How do distinct facets of tree diversity and community assembly respond to environmental variables in the subtropical Atlantic Forest?

This study assessed the impact of altitude, precipitation, and soil conditions on species richness (SR), phylogenetic diversity (PD), and functional diversity (FD) standardized effect sizes in subtropical Brazilian Atlantic Forest tree communities. We considered specific trait information (FDs) for FD, reflecting recent adaptive evolution, contrasting with deeper phylogenetic constraints in FD. Three functional traits (leaf area-LA, wood density-WD, and seed mass-SM) were examined for their response to these gradients. Generalized least squares models with environmental variables as predictors and diversity metrics as response variables were used, and a fourth-corner correlation test explored trait-environmental relationships. SR decreased with altitude, while PD increased, indicating niche convergence at higher altitudes. Leaf area and seed mass diversity also decreased with altitude. For LA, both FD and FDs were significant, reflecting filtering processes influenced by phylogenetic inheritance and recent trait evolution. For SM, only the specific trait structure responded to altitude. LA and SM showed significant trait-environmental relationships, with smaller-leaved and lighter-seeded species dominant at higher altitudes. Soil gradients affect diversity. Fertile soils have a wider range of LA, indicating coexistence of species with different nutrient acquisition strategies. WD variation is lower for FDs. SM diversity has different relationships with soil fertility for FDs and FD, suggesting phylogeny influences trait variation. Soil pH influences WD and LA under acidic soils, with deeper phylogenetic constraints (FD). Environmental factors impact tree communities, with evidence of trait variation constraints driven by conditions and resources. Subtropical Atlantic forests' tree assemblies are mainly influenced by altitude, pH, and soil fertility, selecting fewer species and narrower trait spectra under specific conditions (e.g., higher altitudes, pH). Functional diversity patterns reflect both phylogenetic and recent evolution constraints, with varying strength across traits and conditions. These findings highlight the intricate processes shaping long-lived species assembly across diverse environments in the Southern Brazilian Atlantic Forest.

Field studies in small streams of the Atlantic Forest of southern subtropical Brazil reveal two new interstitial microcambevine catfishes of the genus Listrura (Siluriformes: Trichomycteridae)

ABSTRACT A great diversity of small fish species inhabiting shallow aquatic biotopes of the South American Atlantic Forest have been reported in recent years, but records of interstitial catfishes of the genus Listrura for the southern subtropical Brazilian region are still rare. During field inventories in this region, two new species were collected, which are herein described. The new species are distinguished from congeners by a combination of morphological characters, including caudal peduncle morphology, number of vertebrae, relative position of fins, and bone morphology. The findings here described indicate that the scarcity of records of Listrura for the subtropical Atlantic Forest is probably due to the absence of collecting efforts in specialised biotopes, since species of Listrura are leaf litter dwellers. Both new species are probably more closely related to L. depinnai than to other congeners as all three uniquely possess an expanded skin fold supporting the procurrent caudal-fin rays, making the caudal peduncle deeper than the body region anterior to the dorsal and anal fins. However, only one of the new species shares with L. depinnai the presence of a process on the dorsal surface of the autopalatine articular facet for the mesethmoid, a condition not occurring in any other congener. The two new species are easily distinguished from L. depinnai by the absence of a dorsal fin in the latter species. http://www.zoobank.org/urn:lsid:zoobank.org:pub:F68F2A3E-B5F7-418E-BFA6-EA6752BAB543 http://www.zoobank.org/urn:lsid:zoobank.org:pub:F703D95A-0F7E-4261-8B97-5EAAAD9BD698

Climatic triggers of the phenophases of Elaphoglossum macrophyllum in Southern Brazil

Abstract Although ferns have a prominent floristic position with their richness center in Atlantic Forest in Brazil, the effect of climate on their phenophases is still poorly known. This group shows different phenological patterns due to the great latitudinal extent, the strong climatic seasonality of this forest, and the leaf dimorphism found in some species. In this scenario, we evaluated the phenological events of Elaphoglossum macrophyllum and related them to climatic factors. Fertility, leaf renewal, and leaf senescence in E. macrophyllum were analyzed based on the monthly survey of 152 plants growing for two years in the subtropical Atlantic Forest, Brazil. The three analyzed phenophases showed the same intra-annual pattern regarding continuity, regularity, and seasonality along the two years, revealing a phenological pattern for the specie. The generalized additive models for location, scale, and shape (GAMLSS) indicated that photoperiod was the most important trigger for fertility and leaf renewal. Temperature, as an important phenology modulator, was related to leaf renewal and senescence. Our data indicate that E. macrophyllum, an endangered species in southern Brazil, withstands the consequences of seasonal climatic variations without the individual mortality, total leaf shedding, or fertility loss.

Herbivory and leaf expansion of Cyathea phalerata Mart. (Cyatheaceae) in subtropical Atlantic Forest, southern Brazil.

Herbivory is an interaction with great impact on plant communities since relationships between herbivores and plants are fundamental to the distribution and abundance of species over time and space. The aim of this study was to monitor the rate of leaf expansion in the tree fern Cyathea phalerata and evaluate the damage caused by herbivores to leaves of different ages and whether such damage is related to temperature and precipitation. The study was performed in a subtropical Atlantic Forest fragment located in the municipality of Caraá, in the northeast hillside of Rio Grande do Sul state, in southern Brazil. We monitored 24 mature individuals of C. phalerata with croziers in a population of approximately 50 plants. Leaf expansion rate, percentage of damaged leaves and leaf blade consumption rate by herbivory were calculated. Monthly means for temperature and accumulated rainfall were calculated from daily data. Croziers of C. phalerata were found to expand rapidly during the first and second months after emergence (3.98 cm day-1; 2.91 cm day-1, respectively). Damage caused by herbivory was observed in all of the monitored leaves, but none of the plants experienced complete defoliation. The highest percentage (57%) of damaged leaves was recorded at 60 days of monitoring, and also the highest monthly consumption rate of the blade (6.04%) occurred with young, newly-expanded leaves, while this rate remained between 1.50 and 2.21% for mature leaves. Rates of monthly leaf consumption and damaged leaves showed positive and strong relationship with each other and with temperature. The rapid leaf expansion observed for C. phalerata can be considered a phenological strategy to reduce damage to young leaves by shortening the developmental period and accelerating the increase of defenses in mature leaves.

Computer-aided classification of successional stage in subtropical Atlantic Forest: a proposal based on fuzzy artificial intelligence

Due to the continuous variability of the forest regeneration process, patterns of indicator variables with membership in more than one successional stage may occur, making the classification of such stages a challenging and complex task. This study aims at presenting a comparative analysis of artificial intelligence methods as an alternative for computer-aided classification of successional stages in subtropical Atlantic Forest. As a research hypothesis, the authors consider that a fuzzy inference system should provide the best performance due to its ability to deal with uncertainties inherent to complex processes. The analyses were carried out using a database of the forest inventory of Santa Catarina, Southern Brazil. The data are composed of 177 sampling units of subtropical Atlantic Forest (mixed ombrophilous forest), characterized according to eighth indicator variables verified from the field by experts. This database was employed to train several machine learning methods under a tenfold cross-validation process. The overall accuracy (θ) and kappa coefficient were used to compare the performance between FIS and neural networks, classifier committees and support vector machine. Then, to verify if the classification by the FIS differed from the one performed by experts, the Kappa index and a statistical significance analysis by Pearson's [Formula: see text] test were determined. The hypotheses were verified with two-way tests at a significance level (α) 0.05, for a test power (1-β) 0.8 and minimum expected effect size between medium (ρ = 0.3). Statistical significance tests confirmed the hypothesis that FIS achieved the highest performance, with θ = 98.3% and a kappa value equal to 0.93 (almost perfect agreement) and showed no significant difference ([Formula: see text] = 0.047, p = 0.976) in comparison with the classification by experts. The use of FIS represents a promising alternative as a tool applicable for computer-aided classification of successional stages in subtropical Atlantic Forest. The results and conclusions should substantially impact the guidelines and decision-making process for deforestation authorizations and applicable compensation measures, which are based on the forest succession stage.

Living on the edge: The use of fruit‐feeding butterflies to evaluate edge effect on subtropical assemblages

AbstractThis study evaluated how the edge effect influences the structuration of fruit‐feeding butterfly assemblages in swamp forest fragments of the subtropical Atlantic Forest, Southern Brazil. Sampling was carried out twice in 10 fragments using baited traps placed in sampling units both at the forest edge and 50 m within the forest interior, with the habitats being defined by a set of environmental variables. Richness and abundance were higher for edge habitats with an effect of temperature depending on humidity and luminosity. The subfamily/tribe composition of fruit‐feeding butterflies was segregated between edge and interior and was predicted by wind speed and the interaction between humidity and luminosity. Fifty meters within the forest interior is not sufficient to cause homogenization of butterfly composition between the edge and interior of swamp forest fragments, indicating distinct assemblages in each habitat. The interior harboured forest‐loving butterfly groups while the edge harboured generalist sun‐loving and common butterflies associated with disturbed areas, suggesting resistance to the effects of habitat fragmentation. We highlight the importance of using fruit‐feeding butterfly groups, instead of species, to evaluate edge effects. We also suggest that a heterogeneous matrix with native habitats and distinct semi‐natural land‐use systems be maintained to manage subtropical areas by increasing connectivity within the landscape. Considering the impacts that the Atlantic Forest suffers, increased knowledge of modifications caused at small and regional scales is crucial for the maintenance of ecological processes and represents a tool for conservation planning and environmental agendas.

Prioritization of key indicators for the classification of successional stages in regenerating subtropical Atlantic forest, Southern Brazil: a proposal based on multivariate order statistics

Prioritization of key indicators for the classification of successional stages in regenerating subtropical Atlantic forest, Southern Brazil: a proposal based on multivariate order statistics

Effects of a native bamboo species on tree regeneration diversity of a subtropical Atlantic forest

The presence of native bamboo species is considered a factor that affects the dynamics of plant communities in tropical and subtropical forests. In southern Brazil, Merostachys skvortzovii is a long-lasting species (reproductive cycles of 32 years) highly dominant in disturbed areas, causing structural changes in the tree community. In this work, we assessed changes in regeneration communities in 11 years after a reproductive event of M. skvortzvii. We asked if canopy openness and time after bamboo reproduction affect taxonomic and functional diversities of regeneration communities. We installed 20 permanent plots were randomly distributed in the continuous canopy (CC) and open canopy (OC), measured bamboo culms density, and surveyed the regeneration community over the period 2008–2017, and used a generalized linear model to explore the effects of the environment and presence of bamboos on the diversity of regeneration community. We observed an increase in abundance, species richness, and beta diversity over time after the reproductive event, but the time did not affect the Shannon-Wiener index. The canopy opening positively affected the individual abundance species richness, beta diversity, Functional richness (FRic), Functional evenness (FEve) and Functional dispersion (FDis). Also, we found an effect of the canopy opening on the functional attributes positively affecting specific leaf area (SLA) and negatively affecting leaf mass area (LMA) and Leaf carbon content (LCC). We concluded that, despite the intense colonization after the reproduction, the bamboo population follows a decreasing dynamic without negative effects on the regeneration of subtropical forest species, which are more affected by the dynamics of the gaps than bamboo presence. These results show that the subtropical Atlantic Forest regeneration community can restructure itself in the understory without the need for bamboo management.

Edge effect on vascular epiphytes in a subtropical Atlantic Forest fragment

Epiphytes are efficient indicators of environmental quality. The Atlantic Forest is a hotspot for epiphyte richness; however, it is experiencing one of the highest rates of degradation, exposing epiphytes to edge effects. This study aimed to evaluate the floristic composition and richness of vascular epiphytes and their relationship with phorophyte features and microenvironmental variables at the edge and in the interior of a subtropical Atlantic Forest fragment in Brazil. Twenty-five trees were analyzed, respectively, at the edge and in the interior of the fragment. Height and diameter of phorophytes, temperature, relative air humidity, photosynthetically active radiation and canopy opening were measured. A total of 41 epiphytic species were recorded, 40 occurring in the interior and 23 at the edge. Orchidaceae, Bromeliaceae, and Polypodiaceae were the richest families, representing 75% of all species. The average number of species per tree in the interior was twice that for the edge. Pleopeltis pleopeltifolia, Microgramma squamulosa, M. vacciniifolia and Rhipsalis teres concentrated great biomass in both environments, with twice as much in the interior. Epiphyte richness and biomass was lower on thinner trees with more open canopies at the edge. Our results indicate that the forest interior is more beneficial for epiphytes, which are sensitive to environmental changes caused by the edge effect. The contrast between the epiphytic communities of the edge and the interior reveals the need to increase richness and abundance of native trees and prevent cattle grazing, the planting of exotic species and more human settlements in the habitat matrix.

Evaluating Trade-Offs between Using Regional and Site-Specific Allometric Models to Predict Growing Stock Volume of Subtropical Atlantic Forests

Abstract Choosing models to predict volume for individual trees is a relevant step in estimating growing stock volume. When large-area estimates are needed, models should ideally be constructed based on observations acquired across the population. However, due to multiple constraints, models are often constructed using samples collected at one or in a few sites. Therefore, this study aimed to evaluate trade-offs between using models based on a regional dataset (RD) and a model based on a local dataset (LD) and to assess the effects of such models on large-scale estimates of stem volume (V) per unit area. Regional and local V datasets and inventory data acquired throughout the subtropical Brazilian Atlantic Forest were employed. When used to predict V for trees of the RD (n = 1,192), the local model (LM), based on 419 tree observations, presented a mean systematic percentage error (MSPE) of +11%. In turn, when the regional model (RM) (n = 1,192) was used to predict V for trees of the LD (n = 419), it yielded an MSPE of –3%. The estimated mean V ha–1 using the LM was 9.4% greater than the estimated mean using the RM. Moreover, less precise estimates were attained using the LM.

Selective logging of a subtropical forest: Long-term impacts on stand structure, timber volumes, and biomass stocks

Long-term studies are key to understanding the dynamics of managed forests, especially as related to timber supplies. We evaluated 20 years of recovery of pre-harvest structure, biomass, and timber stocks of a Subtropical Atlantic Forest in Argentina subjected to either conventional selective logging (CL = ∼15 m3 ha−1) or reduced-impact logging (RIL = ∼11 m3 ha−1); we also monitored the dynamics of interspersed plots of unlogged forest (Control). All trees ≥10 cm DBH were measured before and at variable intervals for 20 years post-logging; the results are presented for all stems and for only those of species that provide commercial timber. After logging, basal areas and volume of all stems increased two-times faster after CL than after RIL, whereas biomass increments were similar between logged treatments. In contrast, commercial timber tree stocking did not recover regardless of the harvesting system applied. Mortality rates were high in both CL and RIL plots but also in unlogged Control plots (1.6–3.6 % year−1). The failure of timber stocks to recover was apparently due to high tree mortality rates coupled with the proliferation of understory bamboos. Alternative silvicultural methods are clearly needed to avoid degrading the remaining species-rich Subtropical Atlantic Forest.

Correlation of variations in species abundance of Atlantic forests regenerating on abandoned pastures with different environmental and spatial variables

The conversion of native forests into pastures is still a common practice in Brazil. Abandoned pastures have great potential for natural regeneration and therefore could play an important role in meeting the enormous demand for forest restoration. Few studies, however, have investigated the extent to which spatially-structured environmental variables and community structure are correlated with the variation in species abundance of regenerating forests on abandoned pastures. Therefore, we aimed to determine whether environmental and spatial variables were capable of explaining the variation in abundance of woody species on abandoned pastures in the subtropical Atlantic Forest. We systematically distributed 45 sample plots with size and inclusion criteria that changed according to the vegetation layer in three different abandoned pastures. In general, most of the variation in species abundance that our models were able to explain was correlated with spatially-unstructured physical-chemical soil properties. A smaller part of the variation was correlated with spatially-structured soil variables and topography-related variables. An even smaller portion of the variation was spatially-structured but was not correlated with spatially-structured environmental variables. Therefore, our results suggest that the variation in species abundance of regenerating subtropical Atlantic forests on abandoned pastures is more closely related to niche-based processes mediated by environmental variables than to stochastic spatial processes.