One Sentence Summary: Empirical evidence from grasslands around the world demonstrates a humped-back relationship between plant species richness and biomass at the 1 m 2 plot scale.Abstract: One of the central problems of ecology is the prediction of species diversity. The humped-back model (HBM) suggests that plant diversity is highest at intermediate levels of productivity; at low productivity few species can tolerate the environmental stresses and at high productivity a small number of highly competitive species dominate. A recent study claims to have comprehensively refuted the HBM. Here we show, using the largest, most geographically diverse dataset ever compiled and specifically built for testing this model that if the conditions are met, namely a wide range in biomass at the 1 m 2 plot level and the inclusion of plant litter, the relationship between plant biomass and species richness is hump shaped, supporting the HBM. Our findings shed new light on the prediction of plant diversity in grasslands, which is crucial for supporting management practices for effective conservation of biodiversity. 4Main Text: The relationship between plant diversity and productivity is a topic of intense debate (1-6). The HBM states that plant species richness peaks at intermediate productivity, taking above-ground biomass as a proxy for annual net primary productivity (ANPP) (7-9). This diversity peak is driven by two opposing processes; in unproductive and disturbed ecosystems where there is low plant biomass, species richness is limited by either stress, such as insufficient water and mineral nutrients, or high levels of disturbance-induced removal of biomass, which few species are able to tolerate. In contrast, in the low disturbance and productive conditions that generate high plant biomass it is competitive exclusion by a small number of highly competitive species that is hypothesized to constrain species richness (7-9). Other mechanisms proposed to explain the unimodal relationship between species richness and productivity include disturbance (10), evolutionary history and dispersal limitation (11,12), and density limitation affected by plant size (13).Different case studies have supported or rejected the HBM, and three separate meta-analyses reached different conclusions (14). This inconsistency may indicate a lack of generality of the HBM, or it may reflect a sensitivity to study characteristics including the type(s) of plant communities considered, the taxonomic scope, the length of the gradient sampled, the spatial grain and extent of analyses (14,15), and the particular measure of net primary productivity (16). Although others would argue (6), we maintain that the question remains whether the HBM serves as a useful and general model for grassland ecosystem theory and management. 5 We quantified the form and strength of the richness-productivity relationship using novel data from a globally-coordinated (17), distributed, scale-standardized and consistently designed survey, in which plant richness and biomass were m...

Fire has played an important role in the plant dynamics and diversity of the Cerrado for millions of years. We evaluated fire behaviour in different fire seasons in areas of an open savanna, providing information for fire management plans. It has been hypothesised that early fires (May – end of the rainy season) will be less intense than those conducted in the middle and end of the dry season (July and October) owing to the amount of dead biomass accumulated. Therefore, we compared fire behaviour in early, mid- and late dry season, evaluating the main fire and environmental variables. Fire intensity was mainly influenced by the combination of dead fuel percentage and fuel load. Even though this combination was the best model to explain fire intensity variability, fire parameters (including fire intensity) did not differ between fire seasons. Flame height was best explained by dead fuel percentage + fuel moisture content, dead fuel percentage + fuel load and also by dead fuel percentage. Our study showed that, in areas with fire exclusion for 2 years, fire season did not influence fire parameters and fire behaviour and the main factors influencing fire intensity were the proportion of dead biomass and total fuel load.

Some invasive grasses have been reported to change fire behavior in invaded plant communities. Urochloa brizantha is an aggressive invasive grass in the Brazilian Cerrado, an ecosystem where fire is a common disturbance. We investigated the effects of U. brizantha on fire behavior in an open Cerrado physiognomy in Central Brazil. Using experimental burnings we compared fire behavior at both the community and the individual plant level in invaded (UJ) and non-invaded (NJ) areas burned in July. We also assessed the effect of fire season in invaded areas by comparing July (UJ) and October (UO) burnings. We evaluated the following variables: fuel load, fuel moisture, combustion efficiency, maximum fire temperature, flame height, and fire intensity. Additionally, we evaluated the temperatures reached under invasive and native grass tussocks in both seasons. Fuel load, combustion efficiency, and fire intensity were higher in NJ than in UJ, whilst flame height showed the opposite trend. Fuel amount and fire intensity were higher in October than in July. At the individual plant level, U. brizantha moisture was higher than that of native species, however, temperatures reaching C600°C at ground level were more frequent under U. brizantha tussocks than under native grasses. At the community level, the invasive grass modified fire behavior towards lower intensity, lower burning efficiency, and higher flame height. These results provide essential information for the planning of prescribed burnings in invaded Cerrado areas.

Aim: Fire is a natural disturbance in many ecosystems throughout the world where plant populations can persist by the resprouting of individuals and/or by recruiting from seeds. We evaluated the post-fire regeneration response for 41 coexisting species, including grasses, forbs, and shrubs, from an open Cerrado community (campo sujo) in Central Brazil. Location: The study was conducted at the Reserva Natural Serra do Tombador (RNST) in Central Brazil. The vegetation of the study area is characterized by a continuous herbaceous layer dominated by grasses and scattered shrubs, which produces fine fuel loads that can burn frequently. Methods: We examined both resprouting ability after experimental fires, accounting for bud location, and seed response to heat shocks caused by fire, where seeds were subjected to heat shocks of 100°C for one and three minutes, 200°C for one minute, and a control (untreated seeds). Results: All species were able to resprout (R+) after fire, mainly from buds located in underground structures, but also from aerial and basal buds. Seeds of most species tolerated heat shocks of 100°C for one and three minutes, but heat treatments of 200°C decreased seed viability of nearly 50% of species. Seven species, all of which had dormant seeds, showed heat-stimulated germination. In sum, 81% of the community was classified as R+PT (resprouters with heat-tolerant propagules) and 17% was R+PS (resprouters with heat-stimulated propagules). The remaining 2% (one species) was classified as R+P−, showing heat-sensitive seeds. Conclusions: Resprouting is the main post-fire regeneration strategy in Cerrado open savannas, while fire-stimulated germination, although possible, is less common in comparison to the frequency in other fire-prone ecosystems. However, in Cerrado open savannas, heat tolerance is an important trait that enables germination when favorable conditions arise.

Information from a field perspective on temperature thresholds related to physical dormancy (PY) alleviation and seed resistance to high temperatures of fire is crucial to disentangle fire- and non-fire-related germination cues. We investigated seed germination and survival of four leguminous species from a frequently burned open Neotropical savanna in Central Brazil. Three field experiments were conducted according to seed location in/on the soil: (1) fire effects on exposed seeds; (2) fire effects on buried seeds; and (3) effects of temperature fluctuations on exposed seeds in gaps and shaded microsites in vegetation. After field treatments, seeds were tested for germination in the laboratory, together with the control (non-treated seeds). Fire effects on exposed seeds decreased viability in all species. However, germination of buried Mimosa leiocephala seeds was enhanced by fire in an increased fuel load treatment, in which we doubled the amount of above-ground biomass. Germination of two species (M. leiocephala and Harpalyce brasiliana) was enhanced with temperature fluctuation in gaps, but this condition also decreased seed viability. Our main conclusions are: (1) most seeds died when exposed directly to fire; (2) PY could be alleviated during hotter fires when seeds were buried in the soil; and (3) daily temperature fluctuations in gaps also broke PY of seeds on the soil surface, so many seeds could be recruited or die before being incorporated into the soil seed banks. Thus seed dormancy-break and germination of legumes from Cerrado open savannas seem to be driven by both fire and temperature fluctuations.

Seed germination in many species from fi re-prone ecosystems may be triggered by heat shock and/or temperature fl uctuation, and how species respond to such fi re-related cues is important to understand post-fi re regeneration strategies. Th us, we tested how heat shock and daily temperature fl uctuations aff ect the germination of four species from fi re-prone ecosystems; two from the Cerrado and two from the Mediterranean Basin. Seeds of all four species were subjected to four treatments: Fire (F), temperature fl uctuations (TF), fi re+temperature fl uctuations (F+TF) and control (C). After treatments, seeds were put to germinate for 60 days at 25ºC (dark). Responses diff ered according to species and native ecosystem. Germination percentage for the Cerrado species did not increase with any of the treatments, while germination of one Mediterranean species increased with all treatments and the other only with treatments that included fi re. Although the Cerrado species did not respond to the treatments used in this study, their seeds survived the exposure to heat shock, which suggests they possess tolerance to fi re. Fire frequency in the Cerrado is higher than that in Mediterranean ecosystems, thus traits related to fi re-resistance would be more advantageous than traits related to post-fi re recruitment, which are widespread among Mediterranean species.

Pág. 19, linha 9-acrescentar: essa espécie provavelmente chegou ao Parque Estadual do Juquery por disseminação das pastagens do entorno.

Given the current global environmental crisis, restoring degraded ecosystems stands out among the nature-based solutions to mitigate climate change, reestablish ecosystem services, and maintain biodiversity and human well-being. The high biodiversity of the Atlantic Forest (AF) and its severe degradation turned it into a "restoration hotspot." We performed a bibliometric analysis of the research on restoration of the Brazilian AF to identify thematic trends, potential gaps, as well as networks and benefits of collaboration. We also explored the spatial distribution of degradation, restoration science, and practice within the AF. We analyzed 932 articles on the issue from the Web of Science platform . Publications abruptly increased in the last 15 years, first by Brazilian groups and later in collaboration with foreign groups. International collaboration increased the probability of highly cited articles. Topics addressed have changed greatly in their relative position over time, likely due to scientific advances refuting theories or invalidating failed techniques. Natural regeneration was the main trending topic, while forest succession was the main emerging topic, and ecosystem services appeared as a trending topic. Research and restoration initiatives were both unevenly distributed throughout the AF region, with the southeastern region of Brazil standing out (60% of publications). The percentage of the original AF undergoing restoration is very low in all regions, regardless of scientific publications or AF extent remaining. The knowledge gaps pointed-climate change and functional traits-should drive priorities for research funding, aiming to provide robust evidence to support decision-making processes as well as restoration practices.