1. 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. 2. 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. 3. 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.
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.
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.
1. Around 40% of the original Brazilian savanna territory is occupied by pastures dominated by fast-growing exotic C 4 grasses, which impact ecosystem nutrient cycling. The restoration of these areas depends on the re-establishment of soil processes.2. 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.3. 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
Gramíneas invasoras introduzidas para pastagem são um grande desafio para conservação e restauração do Cerrado. Este grupo é constituído principalmente por espécies de rápido crescimento e estratégias aquisitivas que se desenvolvem rapidamente em solos ricos em nutrientes. A modificação do solo do Cerrado, retirando suas características típicas de baixo pH e baixa disponibilidade nutricional, facilita a invasão. Por isso, alterações nas condições edáficas de áreas degradadas, buscando tornar o solo mais próximo do solo nativo do Cerrado, podem contribuir para o sucesso de plantas nativas. Dessa forma, buscamos responder como a acidificação do solo altera o desenvolvimento de umas gramínea invasora e uma nativa. Para isso, semeamos as espécies em solo acidificado por sulfato ferroso e avaliamos a biomassa aérea e área específica foliar das espécies após três meses de crescimento. Observamos que a acidificação teve um maior efeito na redução do crescimento da gramínea nativa devido ao fato desta ser uma espécie de estratégia aquisitiva, diferentemente de outras espécies nativas abundantes no Cerrado.
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