Intraspecific trait variability facilitates tree species persistence along riparian forest edges in Southern Amazonia.

Tropical forest fragmentation from agricultural expansion alters the microclimatic conditions of the remaining forests, with effects on vegetation structure and function. However, little is known about how the functional trait variability within and among tree species in fragmented landscapes influence and facilitate species' persistence in these new environmental conditions. Here, we assessed potential changes in tree species' functional traits in riparian forests within six riparian forests in cropland catchments (Cropland) and four riparian forests in forested catchments (Forest) in southern Amazonia. We sampled 12 common functional traits of 123 species across all sites: 64 common to both croplands and forests, 33 restricted to croplands, and 26 restricted to forests. We found that forest-restricted species had leaves that were thinner, larger, and with higher phosphorus (P) content, compared to cropland-restricted ones. Tree species common to both environments showed higher intraspecific variability in functional traits, with leaf thickness and leaf P concentration varying the most. Species turnover contributed more to differences between forest and cropland environments only for the stem-specific density trait. We conclude that the intraspecific variability of functional traits (leaf thickness, leaf P, and specific leaf area) facilitates species persistence in riparian forests occurring within catchments cleared for agricultural expansion in Amazonia.

Cerrado deforestation threatens regional climate and water availability for agriculture and ecosystems.

The Brazilian Cerrado is one of the most biodiverse savannas in the world, yet 46% of its original cover has been cleared to make way for crops and pastures. These extensive land-use transitions (LUTs) are expected to influence regional climate by reducing evapotranspiration (ET), increasing land surface temperature (LST), and ultimately reducing precipitation. Here, we quantify the impacts of LUTs on ET and LST in the Cerrado by combining MODIS satellite data with annual land use and land cover maps from 2006 to 2019. We performed regression analyses to quantify the effects of six common LUTs on ET and LST across the entire gradient of Cerrado landscapes. Results indicate that clearing forests for cropland or pasture increased average LST by ~3.5°C and reduced mean annual ET by 44% and 39%, respectively. Transitions from woody savannas to cropland or pasture increased average LST by 1.9°C and reduced mean annual ET by 27% and 21%, respectively. Converting native grasslands to cropland or pasture increased average LST by 0.9 and 0.6°C, respectively. Conversely, grassland-to-pasture transitions increased mean annual ET by 15%. To date, land changes have caused a 10% reduction in water recycled to the atmosphere annually and a 0.9°C increase in average LST across the biome, compared to the historic baseline under native vegetation. Global climate changes from increased atmospheric greenhouse gas concentrations will only exacerbate these effects. Considering potential future scenarios, we found that abandoning deforestation control policies or allowing legal deforestation to continue (at least 28.4 Mha) would further reduce yearly ET (by -9% and -3%, respectively) and increase average LST (by +0.7 and +0.3°C, respectively) by 2050. In contrast, policies encouraging zero deforestation and restoration of the 5.2 Mha of illegally deforested areas would partially offset the warming and drying impacts of land-use change.

O Cerrado brasileiro é uma das savanas mais biodiversas do mundo. Apesar disso, 46% da sua cobertura original foi desmatada para dar lugar a cultivos agrícolas e pastos. Estas extensas transições de uso do solo (LUT) têm o potencial de influenciar o clima regional, reduzindo a evapotranspiração (ET), aumentando a temperatura da superfície terrestre (LST) e por fim reduzindo a precipitação. O objetivo deste estudo foi quantificar os impactos de LUTs sobre ET e LST no Cerrado, combinando dados do satélite MODIS com mapas anuais de uso e cobertura do solo de 2006-2019. Foram realizadas análises de regressão para quantificar os efeitos de seis LUTs usuais sobre ET e LST, ao longo de todo o gradiente de paisagens do Cerrado. Os resultados indicaram que a retirada de florestas para dar lugar à agricultura ou pastagem aumentou a LST média em ~3.5°C e reduziu a ET média anual em 44% e 39%, respectivamente. Transições de formações savânicas para agricultura ou pastagem aumentaram a LST média em 1.9°C e reduziram a ET média anual em 27% e 21%, respectivamente. A conversão de campos nativos para agricultura ou pastagem aumentou a LST média em 0.9 e 0.6°C, respectivamente. Em contrapartida, transições de formações campestres nativas para pastagens aumentaram a ET média anual em 15%. Até o momento, as mudanças de uso do solo causaram redução de 10% da água reciclada para a atmosfera anualmente e aumento de 0.9°C da LST média ao longo do bioma, em comparação com a linha de base histórica sob vegetação nativa. As mudanças climáticas globais decorrentes do aumento das concentrações atmosféricas de gases do efeito estufa irão exacerbar esses efeitos. Considerando potenciais cenários futuros, observou-se que o abandono das políticas de controle do desmatamento ou o avanço do desmatamento legal (ao menos 28.4 Mha) reduziriam a ET anual (em −9% e −3%, respectivamente) e aumentariam a LST média (em +0.7 e +0.3ºC, respectivamente) até 2050. Por outro lado, políticas que promovam desmatamento zero e restauração dos 5.2 Mha de áreas ilegalmente desmatadas compensariam parte dos impactos de aquecimento e seca causados por alterações de uso do solo.

The Latent Dirichlet Allocation model with covariates (LDAcov): A case study on the effect of fire on species composition in Amazonian forests.

Understanding and predicting the effect of global change phenomena on biodiversity is challenging given that biodiversity data are highly multivariate, containing information from tens to hundreds of species in any given location and time. The Latent Dirichlet Allocation (LDA) model has been recently proposed to decompose biodiversity data into latent communities. While LDA is a very useful exploratory tool and overcomes several limitations of earlier methods, it has limited inferential and predictive skill given that covariates cannot be included in the model. We introduce a modified LDA model (called LDAcov) which allows the incorporation of covariates, enabling inference on the drivers of change of latent communities, spatial interpolation of results, and prediction based on future environmental change scenarios. We show with simulated data that our approach to fitting LDAcov is able to estimate well the number of groups and all model parameters. We illustrate LDAcov using data from two experimental studies on the long-term effects of fire on southeastern Amazonian forests in Brazil. Our results reveal that repeated fires can have a strong impact on plant assemblages, particularly if fuel is allowed to build up between consecutive fires. The effect of fire is exacerbated as distance to the edge of the forest decreases, with small-sized species and species with thin bark being impacted the most. These results highlight the compounding impacts of multiple fire events and fragmentation, a scenario commonly found across the southern edge of Amazon. We believe that LDAcov will be of wide interest to scientists studying the effect of global change phenomena on biodiversity using high-dimensional datasets. Thus, we developed the R package LDAcov to enable the straightforward use of this model.

Prolonged tropical forest degradation due to compounding disturbances: Implications for CO2 and H2 O fluxes.

Drought, fire, and windstorms can interact to degrade tropical forests and the ecosystem services they provide, but how these forests recover after catastrophic disturbance events remains relatively unknown. Here, we analyze multi-year measurements of vegetation dynamics and function (fluxes of CO2 and H2 O) in forests recovering from 7 years of controlled burns, followed by wind disturbance. Located in southeast Amazonia, the experimental forest consists of three 50-ha plots burned annually, triennially, or not at all from 2004 to 2010. During the subsequent 6-year recovery period, postfire tree survivorship and biomass sharply declined, with aboveground C stocks decreasing by 70%-94% along forest edges (0-200 m into the forest) and 36%-40% in the forest interior. Vegetation regrowth in the forest understory triggered partial canopy closure (70%-80%) from 2010 to 2015. The composition and spatial distribution of grasses invading degraded forest evolved rapidly, likely because of the delayed mortality. Four years after the experimental fires ended (2014), the burned plots assimilated 36% less carbon than the Control, but net CO2 exchange and evapotranspiration (ET) had fully recovered 7 years after the experimental fires ended (2017). Carbon uptake recovery occurred largely in response to increased light-use efficiency and reduced postfire respiration, whereas increased water use associated with postfire growth of new recruits and remaining trees explained the recovery in ET. Although the effects of interacting disturbances (e.g., fires, forest fragmentation, and blowdown events) on mortality and biomass persist over many years, the rapid recovery of carbon and water fluxes can help stabilize local climate.

Evolutionary heritage influences Amazon tree ecology.

Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary diversity, ecosystem function and the response of tropical forests to global change.

Dinâmica da comunidade lenhosa de uma floresta de galeria na transição Cerrado-Floresta Amazônica no Leste de Mato Grosso, em um período de sete anos (1999 a 2006) / Woody community dynamics of a gallery forest in the transition Cerrado-Amazon Forest in Eastern Mato Grosso, over a seven year period (1999 to 2006)

O estudo foi realizado na floresta de galeria do Córrego Bacaba (14º 43' 12,2" S e 52º 21' 36,7" W), na transição Cerrado-Floresta Amazônica em Nova Xavantina, Mato Grosso. O objetivo foi avaliar e comparar a dinâmica da comunidade lenhosa de três porções da floresta localizadas em um gradiente topográfico (alto, meio e baixo) em um período de sete anos. O inventário consistiu de 141 parcelas permanentes de 10 × 10 m distribuídas nas três porções da floresta, onde foram medidos os indivíduos com CAP > 15 cm, em 1999 e 2006. Foram calculados os parâmetros de dinâmica e o incremento periódico anual (IPA), com base no número de indivíduos e na área basal. Nas três porções de floresta a mortalidade foi superior ao recrutamento. A porção do baixo foi a mais dinâmica, pois apresentou a maior taxa de mortalidade (6,84 por cento) e o maior recrutamento (4,73 por cento). A elevada dinâmica da floresta deve-se, provavelmente, ao estágio de sucessão intermediário no qual ela se encontra e às diferentes condições do ambiente conforme a topografia. Os valores do IPA de algumas espécies comuns às três porções de floresta permitiram confirmar que ocorrem diferenças no incremento de uma porção para outra, indicando que algumas espécies apresentam restrições e outras são beneficiadas para crescer em determinados ambientes. Por outro lado, algumas espécies apresentaram valores de IPA similares nas três porções da floresta, confirmando plasticidade às diferentes condições ambientais. As espécies estudadas apresentaram taxas distintas de recrutamento, mortalidade e incremento relacionadas aos grupos ecológicos e à localização topográfica. Sugere-se que o gradiente topográfico e a inundação sazonal contribuem para posicionar esta comunidade entre as florestas tropicais mais dinâmicas.

The study was carried out on the gallery forest of the Bacaba stream (14º 43' 12.2" S and 52º 21' 36.7" W), in the transition between Cerrado and Amazon Forest in Nova Xavantina, Mato Grosso State, Brazil. The objective was to evaluate and compare the dynamics of the woody community at three sections of the forest (upper, middle and lower) in a topographic gradient over a seven year period. The inventory consisted of 141 permanent plots (10 × 10 m) distributed in the three sections where all individuals > 15 cm girth at breast height were recorded in 1999 and 2006. Based in density and basal area, the Periodic Annual Increment (PAI) and dynamics parameters were calculated. In all forest sections the mortality was higher than recruitment. The lower section was the most dynamic, because presented the higher mortality (6.84 percent) and recruitment (4.73 percent) rates. The community was dynamic, probably due to its current intermediary successional stage and the different environmental conditions depending on the topography. The PAI values of the species in common with all sections confirm differences in increment, indicating that some have restrictions and others benefit to grow in certain environments. On the other hand, some species had similar PAI values in the three forest sections, confirming a plasticity to adapt to different environmental conditions. The species presented different recruitment, mortality and increment rates, related to the ecological groups and topographic position. We suggest that the topographic gradient and seasonal flooding contribute to include this community among the most dynamic tropical forests.

Dinâmica da comunidade lenhosa de um Cerrado Típico na região Nordeste do Estado de Mato Grosso, Brasil / Dynamics of the woody community of a typical cerrado in Northeastearn Mato Grosso, Brazil

O objetivo do trabalho foi analisar as mudanças na comunidade lenhosa em um período de quatro anos. Foram estabelecidas 50 parcelas permanentes de 10 × 10 m onde foram amostrados todos os indivíduos com diâmetro a 30 cm acima do solo (DAS 30 cm) > 5 cm em 2002 e em 2006. No inventário de janeiro de 2002, foram encontrados 945 indivíduos pertencentes a 77 espécies, 65 gêneros e 35 famílias ao passo que em janeiro de 2006 foram 1.106 indivíduos distribuídos em 80 espécies, 66 gêneros e 36 famílias. A diversidade de espécies e a estrutura diamétrica da comunidade não diferiram no período. As taxas de mortalidade (4,01 por cento ano-1) e de perda de área basal (0,68 por cento ano-1) foram compensadas pelas taxas de recrutamento (6,67 por cento ano-1) e de ganho de área basal (2,26 por cento ano-1), indicando a manutenção da comunidade como aparentemente estável. O incremento periódico anual (IPA) da comunidade foi de 0,31 cm ano-1, sendo superado pelo IPA de Euplassa inaequalis, Kielmeyera rubriflora e Byrsonima coccolobifolia (0,72, 0,49 e 0,47 cm ano-1, respectivamente), indicando o potencial de crescimento de tais espécies como importante para estratégias de recuperação de áreas degradadas. A ausência de fogo no período estudado pode ter sido o fator responsável pela dinâmica da vegetação do cerrado estudado, favorecendo o estabelecimento de algumas espécies lenhosas e proporcionando aumento em densidade e biomassa.

The objective of the study was to investigate changes in the woody plant community in a four-year period. It was established 50 permanent plots of 10 × 10 m and all individuals with diameter above ground 30 cm (DAG 30 cm) > 5 cm were sampled in 2002 and 2006. In the inventory of January 2002, were found 945 individuals belonging to 77 species, 65 genera and 35 families and in January 2006, were 1,106 individuals, 80 species, 66 genera and 36 families. Community species diversity and diameter structure did not change within the period. Mortality rates (4.01 percent year-1) and basal area losses (0.68 percent year-1) were offset by recruitment (6.67 percent year-1) and gain (2.26 percent year-1), indicating community maintenance as stable apparently. The periodic annual increment (PAI) of the community was 0.31 cm year-1, being overcome by the PAI of Euplassa inaequalis, Kielmeyera rubriflora and Byrsonima coccolobifolia (0.72, 0.49 and 0.47 cm year-1, respectively), indicating the growth potential of such species as important for recovery strategies on degraded areas. The absence of fire during the study period may have been the main factor behind the dynamics of the vegetation of the studied cerrado, favoring the establishment of some woody species and providing increase in density and biomass.

Estrutura e composição florística da vegetação lenhosa em cerrado rupestre na transição Cerrado-Floresta Amazônica, Mato Grosso, Brasil / Structure and floristic composition of woody vegetation in cerrado rupestre in the Cerrado-Amazonian Forest transition zone, Mato Grosso, Brazil

O objetivo desse estudo foi determinar a composição florística e a estrutura da vegetação lenhosa (incluindo monocotiledôneas e lianas) em cerrado rupestre na zona de transição Cerrado-Floresta Amazônica, no Parque do Bacaba, em Nova Xavantina, MT (14º 41' S e 52º 20' W) e compará-las com outros estudos de cerrado sentido restrito. Foram demarcadas aleatoriamente 10 parcelas de 20 × 50 m, nas quais foram medidos os indivíduos vivos e mortos em pé com diâmetro mínimo a 30 cm do solo (DAS) > 3 cm. O cerrado rupestre apresentou alta densidade (3.766 indivíduos vivos), riqueza florística (85 espécies, 67 gêneros e 34 famílias) e área basal (15,72 m²ha-1), e ainda elevado valor do índice de diversidade de espécies de Shannon-Wiener (H' = 3,47) e equabilidade de Pielou (J = 0,78) em relação às áreas comparadas. As espécies com maior valor de importância foram Erythroxylum suberosum, Qualea parviflora, Anacardium occidentale, Kielmeyera rubriflora e Vatairea macrocarpa. A maior similaridade florística entre comunidades de cerrado típico e rupestre localizadas em áreas com menores altitudes do leste mato-grossense sugere que nessa região a proximidade geográfica e a altitude exercem influência sobre a composição de espécies, independentemente do substrato. A comunidade apresentou distribuição de alturas unimodal, predominando indivíduos de porte arbustivo com altura < 3 m e DAS < 5 cm. É sugerido aqui que estudos florísticos e fitossociológicos realizados em cerrado rupestre empreguem DAS mínimo de 3 cm e incluam espécies de monocotiledôneas e de lianas para representar de maneira mais realística a riqueza e composição de espécies e a estrutura da vegetação. A elevada riqueza e diversidade de espécies registrada no presente estudo podem estar relacionadas à posição pré-Amazônica deste cerrado rupestre, enfatizando a importância da manutenção do Parque do Bacaba no sentido de garantir a proteção de sua diversidade biológica.

This study aimed to analyze the floristic composition and the structure of a savanna on rocky soil ("cerrado rupestre") woody vegetation (including monocots and lianas) in the Cerrado-Amazon Forest transition zone located at Parque Municipal do Bacaba, Nova Xavantina, State of Mato Grosso (14º 41' S and 52º 20' W), and compare it with other cerrado stricto sensu studies. Ten 20 × 50 m plots were randomly established, within which all live and dead woody plants with at least 3 cm of trunk diameter at 30 cm above ground level (DSH30 > 3 cm) were measured. The cerrado rupestre showed high density (3,766 live individuals), richness (85 species, 67 genera and 34 families) and basal area (15.72 m²ha-1), as well as high levels of Shannon-Wiener species diversity (H' = 3.47) and evenness (J = 0.78) indices. The most important species were Erythroxylum suberosum, Qualea parviflora, Anacardium occidentale, Kielmeyera rubriflora and Vatairea macrocarpa. The greatest floristic similarity found between typical cerrado and "cerrado rupestre" communities from lower altitude areas of Northeastern Mato Grosso suggest that, in this region, altitude and geographical distance influence the species composition, regardless of the substrate. The community presented unimodality in the heights distribution and is mostly compounded by shrubby individuals with height < 3 m and DSH < 5 cm. We suggest that floristic and phytosociological studies conducted in "cerrado rupestre" should adopt DSH > 3 cm and include monocot and liana species, so as to more realistically represent the vegetation richness, species composition and structure. The high species richness and diversity registered in this study might be related to this "cerrado rupestre" pre-Amazonian location, which emphasizes the importance of "Parque do Bacaba" maintenance as a guarantee of its biological diversity protection.