The impact of deadwood in ecosystems is dependent on its longevity, as determined by decay rates controlled by decay agents. Despite the importance of macroclimate, significant variation of decay ...rates within a given macroclimatic envelope has been reported. Such variation may be driven by local‐scale microenvironmental conditions as regulated by the plant community structure as well as the presence of specific biotic and abiotic decay agents, decoupling the relation between macroclimate conditions and deadwood decay rates. In this study, we evaluated the relation between local‐scale variation in plant community structure with the decay rates of deadwood and the relative importance of biotic and abiotic decay agents in deadwood decay in Neotropical Cerrado. For this, we performed a wood mass loss experiment using Pinus taeda wood which was installed at three sites in three vegetation types differing in canopy cover—grasslands, savannas and woodlands; wood was divided into treatments according to deadwood exposure to decay agents—microorganism, termite and solar radiation. Across sites, we found termites and microbes decomposed wood twice as fast as microbes alone, while solar radiation was not a strong driver of deadwood decay in our sites. Additionally, local‐scale variation in plant community structure affected deadwood decay, as decay rates and frequency of wood blocks discovered by termites were lower in woodlands than in grasslands and savannas. Our study highlights the interactive effects of local‐scale variation in plant community structure and termites on deadwood turnover, mainly due to differences in termite foraging behaviour among vegetation types and highlights the key role of termites in deadwood decay throughout Neotropical savannas.
Restoration techniques tailored to grasslands are needed to improve the effectiveness of restoration in tropical landscapes. In this study, we investigated the joint effects of plant–soil legacies ...and soil inocula in native and invaded Cerrado grasslands to evaluate whether different microbial origins affect plant–soil feedbacks and the likelihood of restoration. Using two grass species, we measured aboveground biomass, and several plant traits over two growth cycles. Species responded differently to inocula and legacies. The legacy of the invasive Urochloa eminii and invaded soil inocula positively affected mycorrhizal colonization. The legacy of Diectomis fastigiata, a commonly used species in Cerrado restoration, resulted in a negative self‐feedback potentially limiting its effectiveness for restoration. The success of the invasive species was in part due to its broad ecological niche and its ability to cope with a broad range of soil conditions. Our research suggests soil inocula and legacies could be used to aid restoration efforts in the tropics, allowing restoration practitioners to stimulate the growth of species targeting functional traits for a given ecosystem.
Invasive species pose significant challenges to successful restoration efforts worldwide. A strategy to reduce invasions is to establish communities consisting of species with varied ecological ...strategies. These strategies typically align along the conservative and plant size axes, and more recently, along a below‐ground collaboration axis. However, we lack understanding of how the diverse ecological strategies of Cerrado grass species, their combinations and their interactions with soil conditions can mitigate invasions.
Here, we investigated how native grass communities composed by species with different ecological strategies affect the invasion success in two soil types of abandoned pastures in the Cerrado. Specifically, we tested the hypothesis that greater above‐ and below‐ground functional diversity reduces exotic species invasion. We also evaluated whether the isolated effects of native species on invasion were positive or negative.
We installed an experiment with species richness ranging from zero to eight native grass species. In November 2019, we sowed species combinations to create communities composed by species with different ecological strategies. We quantified the above‐ground biomass of exotic species as a measure of invasion. To characterize the species ecological strategies, we measured five functional traits.
Functional diversity of maximum height and specific root length (SRL) had the highest predictive power; however, the most parsimonious model included only SRL diversity, which represents the collaboration axis. Native above‐ground biomass was also negatively related to exotic species biomass. Furthermore, invasion was greater in less stressful soil conditions but did not interact with diversity. The effect of native species varied from facilitation to competition, with the annual fast‐growing native species favouring invasion.
Synthesis and applications. Our results show that greater functional diversity of combined above‐ and below‐ground traits reduces invasion success, shedding light on an underexplored role of specific root length diversity. The competitive and facilitative effects of different native species highlight the need for careful selection of the species to be used in restoration programmes. Furthermore, the absence of interaction between diversity and soil types highlights the need for an integrated management of the functional composition and edaphic factors to increase resistance to invasion in these Neotropical grass communities.
Resumo
As espécies invasoras representam desafios significativos para os esforços de restauração bem‐sucedidos em todo o mundo. Uma estratégia para reduzir as invasões é estabelecer comunidades constituídas por espécies com estratégias ecológicas variadas. Essas estratégias normalmente se alinham ao longo dos eixos conservador e de tamanho da planta e, mais recentemente, ao longo de um eixo de colaboração subterrânea. No entanto, falta‐nos compreender como as diversas estratégias ecológicas das espécies de gramíneas do Cerrado, suas combinações e suas interações com as condições do solo podem mitigar as invasões.
Aqui, investigamos como comunidades de gramíneas nativas compostas por espécies com diferentes estratégias ecológicas afetam o sucesso da invasão em dois tipos de solo em uma pastagem abandonada no Cerrado. Especificamente, testamos a hipótese de que uma maior diversidade funcional acima e abaixo do solo reduz a invasão de espécies exóticas. Também avaliamos se os efeitos isolados das espécies nativas na invasão foram positivos ou negativos.
Instalamos um experimento com riqueza de espécies variando de zero a oito espécies de gramíneas nativas. Em novembro de 2019, semeamos combinações de espécies para criar comunidades compostas por espécies com diferentes estratégias ecológicas. Quantificamos a biomassa aérea de espécies exóticas como medida de invasão. Para caracterizar as estratégias ecológicas das espécies, medimos cinco características funcionais.
A diversidade funcional de altura máxima e comprimento específico de raiz (CER) teve o maior poder preditivo, porém, o modelo mais parcimonioso incluiu apenas a diversidade de CER, que está relacionado com o eixo de colaboração subterrânea. A biomassa nativa acima do solo também foi negativamente relacionada com a biomassa de espécies exóticas. Além disso, a invasão foi maior em condições de solo menos estressantes, mas não interagiu com a diversidade. O efeito das espécies nativas variou de facilitação a competição, com as espécies nativas anuais de rápido crescimento favorecendo o sucesso da invasão.
Síntese e aplicações. Nossos resultados mostram que uma maior diversidade funcional de características combinadas acima e abaixo do solo reduz o sucesso da invasão, lançando luz sobre um papel pouco explorado da diversidade de CER. Os efeitos competitivos e facilitadores de diferentes espécies nativas destacam a necessidade de uma seleção cuidadosa das espécies a serem utilizadas em programas de restauração. Além disso, a ausência de interação entre diversidade e tipos de solo destaca a necessidade de um manejo integrado da composição funcional e dos fatores edáficos para aumentar a resistência à invasão nessas comunidades gramíneas neotropicais.
Our results show that greater functional diversity of combined above‐ and below‐ground traits reduces invasion success, shedding light on an underexplored role of specific root length diversity. The competitive and facilitative effects of different native species highlight the need for careful selection of the species to be used in restoration programmes. Furthermore, the absence of interaction between diversity and soil types highlights the need for an integrated management of the functional composition and edaphic factors to increase resistance to invasion in these Neotropical grass communities.
Abstract
Droughts are predicted to increase in both frequency and intensity by the end of the 21st century, but ecosystem response is not expected to be uniform across landscapes. Here we assess the ...importance of the hill-to-valley hydrologic gradient in shaping vegetation embolism resistance under different rainfall regimes using hydraulic functional traits. We demonstrate that rainfall and hydrology modulate together the embolism resistance of tree species in different sites and topographic positions. Although buffered by stable access to groundwater, valley plants are intrinsically more vulnerable to drought-induced embolism than those on hills. In all study sites, the variability in resistance to embolism is higher on hills than on valleys, suggesting that the diversity of strategies to cope with drought is more important for tree communities on hills. When comparing our results with previously published data across the tropics, we show greater variability at the local scale than previously reported. Our results reinforce the urgent need to extend sampling efforts across rainfall regimes and topographic positions to improve the characterization of ecosystem resistance to drought at finer spatial scales.
Species loss leads to changes in ecosystem function and services, impacting human well‐being. Although biodiversity restoration is pivotal to circumvent this situation, the techniques for restoring ...old‐growth savannas are still limited and the restoration outcomes remain unpredictable. Here, we use a trait‐based approach to understand the functional outcomes of ecological restoration via direct seeding in a Brazilian savanna (cerrado, hereafter neotropical savanna). We compared the functional composition from woody and non‐woody component, total biomass, and biomass allocation of a restored relative to a degraded savanna (abandoned pasture) dominated by exotic grasses and a well‐preserved old‐growth native savanna. We found that the functional composition of restored communities was very similar to those dominated by exotic grasses, both characterized by a greater dominance of species with acquisitive traits, higher above‐ground biomass, and lower investment in root biomass. In contrast, the native vegetation exhibited a dominance of conservative traits and higher investment in belowground rather than aboveground biomass. Even though the acquisitive traits in the restored savanna allow a fast aboveground biomass accumulation and soil cover, the lower belowground biomass investment in the restored savanna may limit its resistance and resilience to droughts and fires. Our findings suggest that restoration efforts in neotropical savanna should focus on fostering the establishment of slow‐growing species to recover the ecosystem properties provided by the high biodiversity in neotropical savannas.
Around 40% of the original Brazilian savanna territory is occupied by pastures dominated by fast‐growing exotic C4 grasses, which impact ecosystem nutrient cycling. The restoration of these areas ...depends on the re‐establishment of soil processes.
We assessed how restoration of abandoned pastures through direct seeding of native species and land‐management practices (burning and ploughing) affect soil nutrient cycling dynamics compared with native savannas. We compared the activity of soil enzymes related to carbon, nitrogen (N) and phosphorus (P) cycling as well as soil microbial biomass and soil chemical properties (pH and the concentration of N, P, potassium K and soil organic matter) among abandoned pastures, native savanna and restored areas.
Abandoned pastures had faster nutrient turnover than native savanna, dominated by slow‐growing native species. This pattern was evident from the overall higher biomass‐specific enzyme activities in abandoned pastures than in native savanna. Compared with native savanna, restored areas had similar levels of soil enzyme activities, but lower microbial biomass and soil organic matter. The low enzyme activity in restored areas was likely related to a reduced soil organic carbon concentration due to practices such as burning and ploughing, rather than the restoration of plant–soil feedback. The lower immobilization of nutrients in microbial biomass and lower retention of nutrients in restored areas, compared with native savanna, is expected to favour the re‐establishment of fast‐growing exotic species.
Synthesis and application. Despite reducing the resprouting and germination of exotic grasses and improving the establishment of native grasses in the short term, restoration practices have major impacts on the soil microbial community and soil fertility. The reduction of soil microbial biomass and organic matter content reduces the immobilization of soil nutrients and is expected to favour a fast nutrient turnover in the ecosystem. This may result in the re‐establishment of exotic grasses in the long term. Future efforts should focus on the recovery of soil organic matter content and the establishment of soil microbial communities similar to native ecosystems after the application of land‐management practices. Therefore, the restoration of abandoned pastures should consider a greater focus on restoring soil carbon and nutrient cycling
Despite reducing the resprouting and germination of exotic grasses and improving the establishment of native grasses in the short term, restoration practices have major impacts on the soil microbial community and soil fertility. The reduction of soil microbial biomass and organic matter content reduces the immobilization of soil nutrients and is expected to favour a fast nutrient turnover in the ecosystem. This may result in the re‐establishment of exotic grasses in the long term. Future efforts should focus on the recovery of soil organic matter content and the establishment of soil microbial communities similar to native ecosystems after the application of land‐management practices. Therefore, the restoration of abandoned pastures should consider a greater focus on restoring soil carbon and nutrient cycling.
Tropical savannas are known for the fire‐prone ecosystems, yet, riparian evergreen forests are another important landscape feature. These forests usually remain safe from wildfires in the wet ...riparian zones. With global changes, large wildfires are now more frequent in savanna landscapes, exposing riparian forests to unprecedented impact.
In 2017, a large wildfire spread across the Chapada dos Veadeiros National Park, an iconic UNESCO site in central Brazil, raising concerns about its impact on the fire‐sensitive ecosystems. By combining remote sensing analysis of Google Earth images (2003–2019) with detailed field information from 36 sites, we assessed wildfire impacts on riparian forests. For this, we measured the structure of trees, saplings and herbaceous plants, as well as topsoil variables.
Since 2003, all riparian forests had canopy cover above 90%, but after 2017, canopy cover dropped to 20% in some forests, indicating large variation in wildfire damage. A closer look in the field revealed that, on average, the wildfire killed 52% of adult trees and 87% of tree saplings in flooded forests. In non‐flooded forests, impacts on adult trees were negligible, but fire killed 75% of tree saplings. Opportunistic vines and the invasive grass Melinis minutiflora were already present in severely disturbed flooded forests. In all forests, impacts on many ecosystem variables were related to canopy damage, a variable measurable from satellite. Overall, seasonally flooded riparian forests were the most severely impacted, possibly due to the relatively thinner barks of their trees.
Synthesis and applications. Our findings reveal how riparian forests embedded in tropical savanna landscapes are in danger from large wildfires. The destruction of some forests has opened space for new plant species that may propel a shift to an alternative ecosystem state. Riparian forests are habitat of large savanna animals and their loss could affect entire trophic networks. Managing wildfires and invasive grasses locally is probably the best strategy to maintain riparian forests resilient. As wildfire regimes intensify in tropical savanna landscapes, our findings stress the need for an integrated management that considers riparian forests as a vulnerable element of the system.
Our findings reveal how riparian forests embedded in tropical savanna landscapes are in danger from large wildfires. The destruction of some forests has opened space for new plant species that may propel a shift to an alternative ecosystem state. Riparian forests are habitat of large savanna animals and their loss could affect entire trophic networks. Managing wildfires and invasive grasses locally is probably the best strategy to maintain riparian forests resilient. As wildfire regimes intensify in tropical savanna landscapes, our findings stress the need for an integrated management that considers riparian forests as a vulnerable element of the system.
Droughts are predicted to increase in both frequency and intensity by the end of the 21st century, but ecosystem response is not expected to be uniform across landscapes. Here we assess the ...importance of the hill-to-valley hydrologic gradient in shaping vegetation embolism resistance under different rainfall regimes using hydraulic functional traits. We demonstrate that rainfall and hydrology modulate together the embolism resistance of tree species in different sites and topographic positions. Although buffered by stable access to groundwater, valley plants are intrinsically more vulnerable to drought-induced embolism than those on hills. In all study sites, the variability in resistance to embolism is higher on hills than on valleys, suggesting that the diversity of strategies to cope with drought is more important for tree communities on hills. When comparing our results with previously published data across the tropics, we show greater variability at the local scale than previously reported. Our results reinforce the urgent need to extend sampling efforts across rainfall regimes and topographic positions to improve the characterization of ecosystem resistance to drought at finer spatial scales.
Cerrado’s campo sujo areas have been one of the main focuses of anthropic occupation in the Chapada dos Veadeiros region, Brazil’s Central Plateau, as they are easily accessible flattened areas with ...less dense vegetation. They are usually associated with wetlands representing excellent water reservoirs and groundwater recharge zones. The environmental characterization and analysis of water level variation are essential to investigate the impacts of human occupation. Hydrogeophysics represents one of the main subsurface research tools due to its easy application and efficiency in identifying the water level, with emphasis on Ground-penetrating radar (GPR), and electrical resistivity tomography (ERT). An analysis of GPR sections with 200, 400, and 900 MHz frequency antennas associated with the resistivity model was carried out to identify structures, and map the groundwater level. The overlapping data compose a hydrogeophysical model with good correlation to direct measurements of water level in a monitoring well, and soil horizons mapped in a trench. The GPR proved to be efficient in mapping the water level, mainly about to the survey with a 400 MHz antenna, shown as a horizontal reflector associated with attenuation portions of the reflection signal, registering in profile the lowering of the water level from 1.68 m in May to 3.35 m in August. The resistivity model showed a good correlation with the variations between the mapped soil horizons. The analysis shows that constructing a hydrogeophysical model is an excellent alternative for identifying the water level, and characterizing the shallow subsurface by applying non-invasive techniques. The study area represents a preserved area of campo sujo, and the research data can be used for comparison with future surveys, in addition to representing a base hydrogeophysics methodology that showed promising results for the physiographic characteristics of the area, which can be replicated in regions of similar geoenvironmental aspects.
•Lemierre syndrome is a rare complication of oropharyngeal infection.•The present report is the first report of Lemierre syndrome in a post–liver transplant patient.•Few studies reporting the ...occurrence of Lemierre syndrome in immunosuppressed patients as a result of visceral transplantation were identified.
Lemierre syndrome is a rare complication of oropharyngeal infection, especially acute pharyngotonsillitis, associated with septicemia and thrombophlebitis of the internal jugular vein (IJV). We present the case of a 52-year-old patient who underwent liver transplantation and returned with symptoms of pain, redness and left cervical bulging 1 month after surgery. After investigation, the diagnosis of septic thrombophlebitis of the IJV was made. The patient responded well to treatment with antibiotic therapy and full anticoagulation. To the best of our knowledge, the present report is the first report of Lemierre syndrome in a post–liver transplant patient.
