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Beyond the forest edge: Ecology, diversity and conservation of the grassy biomes
Abstract
Forests and grassy vegetation (savannas and grasslands) are alternative ecosystem states in many tropical landscapes. Relative to forests the grassy ecosystems are poorly known and poorly conserved, partly because they were thought to be products of forest clearance. However many grasslands have proved to be ancient. Commensurate with their antiquity, grassy biomes have distinct suites of plant and animal species that contribute a large fraction of the diversity of forest–grassland mosaics. Grasslands differ strikingly from forests in their ecology and in the nature of threats to their future. Here we highlight the high biodiversity value of grassy biomes and, in contrast to tropical forests, we illustrate the importance of fire in maintaining these systems. We discuss the major threats to, and consequences for, biodiversity in these regions including land clearance and elevated CO2-driven forest expansion. Finally we focus on the difficulties of grassland restoration. A new approach to understanding and conserving grassy ecosystems, free from cultural prejudices of the past, is long overdue.
... Rangelands are among the most widespread nonforest ecosystems, hosting rich biodiversity, storing large amounts of carbon, and providing food for millions of people (Strömberg & Staver, 2022). They are also particularly vulnerable to degradation due to livestock overgrazing and anthropogenic fires (Bond & Parr, 2010;Strömberg & Staver, 2022). Despite the importance of rangelands and the strong land-use pressures they are exposed to, the patterns of rangeland degradation in-and outside protected areas are largely unknown. ...
... Land degradation affects over one third of the global land mass (FAO & ITPS, 2015) and is expected to further increase due to climate change and intensifying land use (Stanimirova et al., 2019). Rangelands, covering a quarter of Earth's surface and directly supporting over one billion people, are particularly affected by degradation (Bond & Parr, 2010;Strömberg & Staver, 2022). However, the effectiveness of protected areas in abating rangeland degradation remains unclear despite many protected areas in rangeland regions. ...
... Our third primary finding was that livestock grazing appears to be the likely cause for the low effectiveness of rangeland protected areas. Generally, livestock, occupying around 26% of the world's terrestrial area (Foley et al., 2011;Godde et al., 2018), is a major driver of habitat degradation (Bond & Parr, 2010). Our analyses showed a clear relationship between livestock presence and rangeland degradation, approximated by green vegetation loss inside protected areas, in line with other studies, especially in Azerbaijan (de Leeuw et al., 2019;Lewińska et al., 2021). ...
As land use intensifies globally, it increasingly exerts pressure on protected areas. Despite open, nonforested landscapes comprising up to 40% of protected areas globally, assessments have predominately focused on forests, overlooking the major pressures on rangelands from livestock overgrazing and land conversion. Across the southern Caucasus, a biodiversity hotspot extending over 5 countries, we conducted a broadscale assessment of the extent to which protected areas mitigate land‐use pressure on rangelands in them. Using satellite‐based indicators of rangeland vegetation greenness from 1988 to 2019, we assessed the effectiveness of 52 protected areas. This period encompassed the collapse of the Soviet Union, economic crises, armed conflicts, and a major expansion of the protected area network. We applied matching statistics combined with fixed‐effects panel regressions to quantify the effectiveness of protected areas in curbing degradation as indicated by green vegetation loss. Protected areas were, overall, largely ineffective. Green vegetation loss was higher inside than outside protected areas in most countries, except for Georgia and Turkey. Multiple‐use protected areas (IUCN categories IV–VI) were even more ineffective in reducing vegetation loss than strictly protected areas (I & II), highlighting the need for better aligning conservation and development targets in these areas. Mapping >10,000 livestock corrals from satellite images showed that protected areas with a relatively high density of livestock corrals had markedly high green vegetation loss. Ineffectiveness appeared driven by livestock overgrazing. Our key finding was that protected areas did not curb rangeland degradation in the Caucasus. This situation is likely emblematic of many regions worldwide, which highlights the need to incorporate degradation and nonforest ecosystems into effectiveness assessments.
... Exotic species are more likely to dominate communities than are native species and are likely to suppress and exclude shorter, less productive and less dominant species. This implies that RVI, as conceived, implemented and evaluated, is undesirable given the current value attached to biodiversity and ecosystem services, the recent emphasis on the origin and importance of grasslands in Southern Africa (Bond and Parr 2010;Strömberg and Staver 2022), the high proportion of irreversibly transformed grasslands (34%) and the poor protection status (2%) of grasslands in South Africa (Slooten et al. 2023). This, coupled with the lack of convincing data supporting economic sustainability, and the apparent low implementation of RVI, effectively condemns the application of RVI on natural, undisturbed veld in southern Africa. ...
... With increasing awareness of the importance of the ecology and diversity of grassy biomes (Bond and Parr 2010), conservation and restoration of grasslands is increasing in importance (Slooten et al. 2023). Carbutt and Kirkman (2022) outline a historical progression of grassland restoration from agricultural-centred pasture establishment to a more proactive biodiversity-centred approach, using native grasses and forbs as part of initiating regeneration processes. ...
... Dentre as características morfológicas que proporciona esta adaptação podem ser citadas a casca grossa das plantas que protegem suas estruturas internas, estruturas de armazenamento, frutos lenhosos que promovem a proteção das sementes, como também estratégias fenológicas e reprodutivas (Cirne;Miranda, 2008;Simon et al., 2009;Bond;Parr, 2010). ...
... Dentre as características morfológicas que proporciona esta adaptação podem ser citadas a casca grossa das plantas que protegem suas estruturas internas, estruturas de armazenamento, frutos lenhosos que promovem a proteção das sementes, como também estratégias fenológicas e reprodutivas (Cirne;Miranda, 2008;Simon et al., 2009;Bond;Parr, 2010). ...
O cerrado piauiense vem sofrendo com interferências antrópicas ao longo do tempo, ocorrendo modificações na sua vegetação nativa. Tornando necessários estudos, para demonstrar a gravidade de alguns impactos, para uma melhor tomada de decisão. O presente estudo tem como objetivo avaliar a composição e regeneração natural da vegetação do cerrado, após queimadas em dois ambientes na região sul do Piauí. A pesquisa foi realizada no município de Uruçuí-PI, avaliando duas áreas, uma em preservação e outra queimada. Nas áreas, duas parcelas foram dispostas aleatoriamente com dimensões de 5 m x 5 m (25 m²). As variáveis analisadas para estimar a regeneração foram composição florística, riqueza, altura de espécies, diâmetro do caule ao nível do solo, índice de diversidade de Shannon (H') e Índice de equabilidade de Pielou (J'). os dados obtidos foram submetidos à análise estatística descritiva, por meio do software Excel. Os resultados encontrados mostraram que na área preservada há uma ocorrência de regeneração sucessional mais avançada em relação à área queimada. a família mais representativa, foi a família Fabaceae. A área queimada apresentou menor riqueza, comparada à área preservada, contendo apenas 12 espécies no total da área amostrada. Espécies da família Poaceae apresentaram maior densidade na área queimada. Houve maior densidade de lianas e trepadeiras na área preservada. Mais de 50% das plantas nas duas áreas tinham alturas variando de 19 a 174,2 cm e diâmetros variando de 1,61 a 39 mm. A área com maior diversidade e distribuição de espécies foi a área preservada com H'=2,65 e J'=0,98. Ocorreu uma grande diferença na composição das árvores entre os dois ambientes. Portanto, conclui-se que a regeneração natural da área preservada é mais evidente, tornando perceptível a severidade do impacto do fogo em todas as variáveis analisadas.
... Conservation of native grasslands and savannas is of increasing concern as they are degraded and converted to other land uses throughout the world (Bond, 2016). Particularly vulnerable are native grassland and savanna ecosystems, referred to as "old-growth grasslands," characterized by long-lived perennial C 4 grasses and forbs that are fire dependent, have large root energy reserves, can resprout and flower quickly following fire, have nonpersistent seed banks, and are limited in capacity to recolonize soil through seed dispersal (Bond & Parr, 2010;Veldman et al., 2015). Such communities are managed to provide essential ecosystem services, including livestock forage, soil stability, and habitat for game species, to many human populations around the world (Dixon et al., 2022;Zhao et al., 2020). ...
... The results of this opportunistic case study contribute to the growing body of literature indicating the threat that intensive soil disturbance poses to old-growth grasslands and savannas worldwide. The life-history traits of plants associated with undisturbed pine savannas of the North American Coastal Plain, including those in our study, are characteristic of many native grasslands and savannas (Bond & Parr, 2010;Buisson et al., 2018;Ratnam et al., 2011;Veldman et al., 2015), suggesting that they too may show similar responses to mechanical disturbances, perhaps including those as narrow as the disk lines in our study. Such disturbances might be expected to cause shifts from endemic, perennial species characteristic of stable communities to geographically widespread, ruderal, and generalist species, followed by slow recovery even under appropriate fire regimes (Dixon et al., 2022). ...
Soil disturbance threatens native perennial grasslands and savannas worldwide, including pine savannas of the North American Coastal Plain. Disk harrows are used in the region to plow linear features for firebreaks to contain prescribed fires, to manage game and other wildlife, and to reduce wildfire hazard to protect forest resources. However, the long‐term response of vegetation to these disturbances has not been well investigated. Our aim was to compare vegetation changes over time (0–9 years) following repeated disturbance by disking and a single disturbance by disking for firebreaks with undisturbed vegetation within a native pine savanna. We hypothesized that (1) a single disking event has multiyear effects on plant species composition and abundance because of the loss of perennial, dispersal‐limited species, but that partial survival of propagules allows the recovery to be more complete than following repeated disturbance, and (2) post‐disturbance changes are determined by species' life‐history characteristics resulting in a successional trajectory toward the undisturbed community. We established 10 plots within a repeated‐disturbance firebreak and a single‐disturbance firebreak, and in undisturbed vegetation ( n = 30). We identified plant species within the plots six times over nine years, categorized plant species by life span, seed bank persistence, and dispersal mechanism, and assessed changes in the plant community using ordination. Changes in species composition in both repeated and single disturbance treatments showed a pattern consistent with succession toward the undisturbed plant community, but vegetation in neither disturbance treatment matched undisturbed treatment conditions within the nine years of study. Repeated‐disturbance plots progressed from a high occurrence of annuals to species with persistent seed banks and wind‐dispersed species. Single‐disturbance plots were more strongly associated with perennials, species lacking a persistent seed bank, and species dispersed by vertebrate consumption, but not to the same degree as undisturbed plots, although differences decreased slightly over time. Our results relating to narrow mechanical soil disturbances in pine savanna vegetation are consistent with studies concluding that similar but larger scale disturbances have long‐term degradational effects on the plant community. Therefore, conservation management plans should consider the possible negative long‐term effects of soil disturbance on native perennial herbaceous plant communities.
... Grasslands and savannas are the most threatened biomes globally (Hoekstra et al., 2005). Within these biomes, undisturbed montane grasslands are one of the most diverse and threatened ecosystem types (Bond and Parr, 2010;Veldman, 2016). While most montane grasslands did not experience the massive degree of transformation to agriculture that occurred in most of the lowerlying grasslands in the early 20 th century, many have been transformed more recently. ...
... Secondary grasslands in montane environments have rarely been studied (Bond and Parr, 2010). A few studies show a reduced diversity of herbaceous plants, particularly forbs, even decades after plantations are removed (Zaloumis and Bond, 2011;Zaloumis and Bond, 2016), consistent with secondary grasslands in general (Nerlekar and Veldman, 2020). ...
Grasslands are one of the most threatened terrestrial ecosystem types, and montane grasslands of particular conservation concern. Despite high rates of transformation in recent decades, croplands and plantations are being abandoned in parts of many countries, creating an opportunity for conservation of montane grasslands through restoration. We report on the changes in the cover of major vegetation types (indigenous forest, grassland, and plantations) between 1935 and 2022, in an area that was intensively afforested from 1930 to 1960 and abandoned in 2000. Montane grassland at the site declined from over 50% of all landcover to below 15%, but subsequently recovered to 30% within 20 years. Many former plantations developed into secondary grassland with estimated gamma plant species richness of 231 for herbaceous species and 45 for savanna species. These are high values considering the size of the study area (4000 ha), and comparable to estimates from primary grassland sites in the broader region. However, at the scale of 1 m2 sampling quadrats, richness in the secondary grasslands was below that recorded in the last remaining patches of primary grassland at the site (means of 2.6 versus 4.7 for graminoid species, and 1.9 versus 2.9 for forbs). Some of the former Eucalyptus plantations had transformed into novel savannas dominated by fire-tolerant, resprouting trees, and may require more active restoration. Secondary grasslands such as those reported on here could potentially make a significant contribution to the conservation of montane biodiversity over the coming decades, warranting further research (both socio-economic and ecological) on the factors that lead to abandonment and promote the emerge of secondary grasslands of high diversity.
... Conversion of grasslands to agriculture and forestry is currently under debate because of water consumption (Jackson et al., 2005;Reichert et al., 2017Reichert et al., , 2021aReichert et al., , 2021bCavalli et al., 2020;Ferreto et al., 2021a), soil degradation (Ferreto et al., 2021b;Rodrigues et al., 2014Rodrigues et al., , 2018Reichert et al., 2016a,b;Valente et al., 2020Valente et al., , 2021Ebling et al., 2021;França et al., 2021;Santos and Reichert, 2022), and potential biodiversity loss (Overbeck et al., 2007(Overbeck et al., , 2013; Roesch et al., 2009;Bond and Parr, 2010;Parr, 2010, 2010;Redin et al., 2017). To respond to the loss of grasslands by conversion to other types of land use, nature conservation and land managers need to assess the restoration potential of abandoned areas and develop strategies to reestablish grasslands in these areas (Overbeck et al., 2013;Andrade et al., 2015;Koch et al., 2016). ...
... Conversion of grasslands to agriculture and forestry is currently under debate because of water consumption (Jackson et al., 2005;Reichert et al., 2017Reichert et al., , 2021aReichert et al., , 2021bCavalli et al., 2020;Ferreto et al., 2021a), soil degradation (Ferreto et al., 2021b;Rodrigues et al., 2014Rodrigues et al., , 2018Reichert et al., 2016a,b;Valente et al., 2020Valente et al., , 2021Ebling et al., 2021;França et al., 2021;Santos and Reichert, 2022), and potential biodiversity loss (Overbeck et al., 2007(Overbeck et al., , 2013; Roesch et al., 2009;Bond and Parr, 2010;Parr, 2010, 2010;Redin et al., 2017). To respond to the loss of grasslands by conversion to other types of land use, nature conservation and land managers need to assess the restoration potential of abandoned areas and develop strategies to reestablish grasslands in these areas (Overbeck et al., 2013;Andrade et al., 2015;Koch et al., 2016). ...
Edaphic influence on plant distribution is essential to community ecology studies, and for vegetation management and restoration in grasslands-forest ecosystems. Pampa biome is a subtropical grassland with high floristic diversity and with an important role in food production in South America, including tree plantations where recent changes in land use soil has been questioned about the impacts on water consumption, soil degradation and potential biodiversity loss. We assessed the relationship of soil physical, chemical and morphological properties with forest and grassland species occurrence, to improve our understanding of soil and landscapes with grasslands-forest mosaics, and contribute to ecological restoration in the biome. Soil physical and chemical
properties were determined in different toposequences localized in two forest farms in southern Brazil, both covered with grassland and native forest use. Natural fertility of the studied soils was highest in the lowlands, along with highest moisture and lowest toxic aluminum content. Soil saturated hydraulic conductivity was
highest in the summit and backslope soils, influenced by coarser fractions in the granulometry. Soil bulk density, total porosity, microporosity, macroporosity, saturated hydraulic conductivity field capacity, permanent wilting point and available water content, influenced by sand, silt and clay contents, varied among soils and landscape and contributed to vegetation diversity. Some of the plant species occupied specific soils and landscapes. The
greatest vegetation frequency was of grassland species (Poaceae and Asteraceae) in both study sites. Grasslandforest area has forest individuals in the middle of the grassland and riparian, while in grassland area the riparian vegetation is composed naturally by grassland. Forest fragments expanded in grassland-forest area during the 15 years prior to our study, but in the grassland area there were no changes in the phyto-physiognomy, demonstrating that the vegetation of grassland occurs naturally in the riparian environment. This study highlights that many of sites covered naturally by grassland, in the Pampa biome, should be protected from disruptive activities and/or recovered with species endemic to the ecosystem, without necessarily by forest enrichment as usually recommended for restoration activities.
... In extensive areas of the tropical region, the landscape assumes a mosaic configuration including scattered grasslands amidst savannas and forests ( Figure 1). According to Bond & Parr (2010), these grass-dominated biomes mirror forests. While forest plants thrive in shaded environments, grassland vegetation avoids shade. ...
... Unlike forests where fallen leaves decompose swiftly, dead matter in grasslands decomposes more gradually, often being consumed by fires. Moreover, fire inflicts structural damage in forest trees, but is essential for the maintenance of large areas of tropical savannas and grasslands (Bond & Parr, 2010). Consequently, upholding regional diversity in such formations requires conserving landscape heterogeneity. ...
Grassland ecosystems, characterized by open landscapes dominated by grasses, encompass diverse formations influenced by geological, climatic, and anthropogenic factors. These environments play a pivotal role in global biodiversity, carbon cycling, and ecosystem services. Due to the worldwide loss and degradation of these habitats, grassland birds are experiencing an unprecedented population decline. This work aims to supply an in-depth exploration of the conservation status of Cerrado grassland birds, including their population trends, protective measures, and primary threats within this bird group. Through an exhaustive literature review, conference of endangered species databases, and field data of grassland birds gathered by us, we compiled a comprehensive dataset detailing the trends, threats, and distribution of Cerrado grassland birds. The Cerrado, the world's largest savanna and Brazil's second-largest biome, accommodates 116 bird species specialized in grassland formations, including 13 endemics. Significantly, a notable proportion (26%) of endangered bird species in the Cerrado are strongly associated with grasslands. The primary threats faced by this group encompass habitat loss and degradation, the proliferation of exotic grass species, and the recurrent incidence of wildfires. Upon analyzing population trends, a concerning 37% of Cerrado grassland birds show declining numbers, with inadequate representation in existing protected areas. While grasslands hold global significance, conservation endeavors often give precedence to tropical forests. The preservation of central Brazil's grassland formations assumes utmost importance in safeguarding the abundant biodiversity of the Cerrado. These formations function as pivotal habitats for endangered and declining bird species, underscoring the pressing need to develop conservation strategies attuned to the unique challenges posed by grassland environments.
... The substantial contribution of forbs to total plant diversity in global grassy ecosystems is progressively being acknowledged (e.g., Bond & Parr 2010, Bråthen et al. 2021, Endress et al. 2022, although the exact proportion is yet to be quantified. Regional-scale floristic assessments of tropical grasslands reported that forbs (including geoxyles) account for over 50% of total plant species richness across continents, of which Asteraceae and Fabaceae represent the most dominant plant families across regions (Table 1). ...
Forbs are important contributors to species diversity and ecosystem functions in low-latitude grasslands, where they support diverse herbivore communities and millions of people. Native forb assemblages tolerate disturbances and physiological stressors (fire, herbivory, drought, and frost) that together have shaped their exceptional functional diversity. Yet, compared to trees and grasses, forbs have received much less attention in grassland studies until recently. Here, we review forb-centric literature to illustrate that land conversion and responsible management of fire and herbivory are crucial to maintaining forb diversity. Management practices promoting forb diversity offer (a) high-quality food items and medicinal resources that support rural livelihoods and animal diversity (from wild ungulates and livestock to fossorial rodents and insects), including their adaptive foraging patterns, and (b) carbon and nutrient inputs that regulate belowground processes. Improved understanding of the above- and belowground regeneration strategies of forbs is critical for restoration and conservation to secure their services in future old-growth tropical and subtropical grasslands.
... The substantial contribution of forbs to total plant diversity in global grassy ecosystems is progressively being acknowledged (e.g., Bond & Parr 2010, Bråthen et al. 2021, Endress et al. 2022, although the exact proportion is yet to be quantified. Regional-scale floristic assessments of tropical grasslands reported that forbs (including geoxyles) account for over 50% of total plant species richness across continents, of which Asteraceae and Fabaceae represent the most dominant plant families across regions (Table 1). ...
Forbs are important contributors to species diversity and ecosystem functions in low-latitude grasslands, where they support diverse herbivore communities and millions of people. Native forb assemblages tolerate disturbances and physiological stressors (fire, herbivory, drought, and frost) that together have shaped their exceptional functional diversity. Yet, compared to trees and grasses, forbs have received much less attention in grassland studies until recently. Here, we review forb-centric literature to illustrate that land conversion and responsible management of fire and herbivory are crucial to maintaining forb diversity. Management practices promoting forb diversity offer (a) high-quality food items and medicinal resources that support rural livelihoods and animal diversity (from wild ungulates and livestock to fossorial rodents and insects), including their adaptive foraging patterns, and (b) carbon and nutrient inputs that regulate belowground processes. Improved understanding of the above- and belowground regeneration strategies of forbs is critical for restoration and conservation to secure their services in future old-growth tropical and subtropical grasslands.
... The ecotone has a well-developed grass cover. The savanna is characterised by grasses and small trees that do not form a closed canopy and allow light to reach the grass layer (Bond and Parr 2010). The sand forest study area was protected from elephants (Loxodonta africana), while the ecotone and savanna study sites were accessible to elephants. ...
Spiders are the dominant representative of the top predator guild in many terrestrial ecosystems, but their diversity and distribution in forests in South Africa are still understudied. This study aimed to determine ground‐dwelling spider diversity, composition and distribution patterns in both sand forest and savanna (and their ecotone) using pitfall traps and to provide a spider species checklist for these three habitats in Phinda Private Game Reserve. A total of 410 individuals from 64 species and 21 families were recorded from the three habitat types. The Lycosidae family and Pardosa crassipalpis were the most dominant family and species. Spider abundances were similar between sand forest and the ecotone, but lower in savanna. However, species richness was similar across habitats. Spider species assemblages were similar between sand forest and the ecotone, but differed from the species assemblages in savanna. Spiders play an important role in food webs both below‐ and aboveground. Therefore, determining their diversity and distribution contributes to the overall understanding of the ecosystem in addition to promoting conservation efforts of key habitats such as the critically endangered sand forest.
... We initially posed three main questions for our comparison and analysis of the three maps-following the theoretical discussion in our introduction. A fourth question arose from the analyses of the three initial questions (Bond & Parr, 2010;Bowman et al., 2015;Power et al., 2017;Ratnam et al., 2011). The structure of the paper follows our four questions. ...
Forest and landscape restoration are increasingly popular nature‐based solutions to mitigate climate change and safeguard biodiversity. Restoration planning and monitoring implies that a reference ecosystem has been defined to which the restored site can be compared, but how to best select such reference? We tested three different potential natural vegetation (PNV) maps of the same areas in Kenya and Uganda for their utility as ecological references with independent data that were not used when those maps were made. These independent datasets included presence observations of woody species from 76 sites in forest reserves in Kenya and Uganda, and classification of surveyed species into a system that included “forest‐only” and “nonforest‐only” ecological types. Our tests show that (1) the three vegetation maps largely agree on the environmental envelopes/ranges within which forests occur. (2) There are large differences in how well the maps predict the presence of forest‐only species. (3) Two maps, based on empirical observations (V4A and White), predict forest types well, whereas the third, based on climate envelopes only (NS), performs poorly. (4) A large area in Uganda is potentially in one of two alternative stable states. We conclude that it is possible to evaluate the utility of PNV maps at a more detailed scale than the level of biome and ecoregion. This indicates that it is possible to map PNV at scales required for reference for restoration and management of forest vegetation. We recommend that empirically based maps of potential natural vegetation are used in restoration planning (biome and PNV maps based on climate envelopes alone may be unreliable tools) as a baseline model for predicting the distribution of reference ecosystems under current and future conditions. It could conveniently be done by deconstructing the existing biome maps, supported by rapid botanical surveys.
... Even when not suppressed, the savannas may be affected by fire and grazing 27,61 . The threats primarily arise from neglect and biases towards these ecosystems, often seen as successional stages of forests with low biodiversity and ecological significance [62][63][64] . However, the Amazonian savannas are old formations 65 and constitute vegetation islands (Supplementary Fig. 1) with distinct characteristics from the neighbor Brazilian Cerrado 7,66 . ...
The Brazilian Amazon Satellite Monitoring Program (PRODES Amazonia) tracks forest loss in the Brazilian Amazon but excludes about 6.6% ( ~ 280,000 km²) of non-forest vegetation (NF). Here we developed the PRODES NF system to address this gap by adapting the well-established methodology of PRODES Amazonia. Initial findings from PRODES NF show that the Brazilian Amazon lost 10.46% ( ~ 30,000 km²) of NF area, mainly in the last two decades, with the estates of Mato Grosso, Roraima, and Amapá being primary hotspots of losses. Savannas were the most affected (13.3% of their extent). NF loss strongly correlates (r = 0.87; p < 0.0001) with deforestation, suggesting a continuum of vegetation loss in the biome regardless of the predominant vegetation type. Combining data from PRODES Amazonia and PRODES NF reveals an official estimate of ~798,000 km² in total primary vegetation loss ( ~ 19% of the entire biome) in the Brazilian Amazon by 2022.
... Habitats with high precipitation seasonality and high fire frequency also are associated with high annual precipitation, which drives high fuel productivity, as shown by trends in data in this study. It also is worth mentioning that, while results were not significant, serotiny showed a trend toward occurring where there were lower temperatures and lower precipitation seasonality, which correspond to environments with less frequent crown fires, such as is common in boreal forests (Cardoso et al., 2008;Bond and Parr, 2010;Nguyen et al., 2019). In total, the results provide insights into biogeographic and habitat conditions of Pinus species and facilitate predicting how their habitat may vary under climate change, thus guiding the conservation of pines, such as prescribed fire regimes might be most appropriate for pines with specific fire-adapted traits and syndromes. ...
... Thus, although savannas are often grouped with grasslands as "grassy biomes" (Bond & Parr, 2010), they should also be considered separately, given the importance of their overstory component. ...
Overstory trees serve multiple functions in grassy savannas. Past research has shown that understory species can vary along gradients of canopy cover and basal area in savannas. This variation is frequently associated with light availability but could also be related to other mechanisms, such as heterogeneity in soil and litter depth and fire intensity. Several savanna studies have found differences in understory plant functional groups within the local environment near trees versus away from them in canopy openings. Although small‐scale variation is known to be high in southeastern U.S. pine savannas, patterns in understory species diversity have not been examined at the scale of individual overstory pine trees in this system. We conducted an observational study of the relationship between understory plant communities and proximity to individual pine trees in xeric and mesic pine savannas in frequently burned sites (1–3 year intervals). We recorded the plant community composition in plots adjacent to tree boles (basal) or outside crown driplines (open). Within each environment, raw species richness was significantly greater in open locations, where light transmittance was greater. In contrast, rarified species richness did not differ. Multivariate analyses showed that community composition differed significantly between basal and open plots. One native, woody species in each environment, Serenoa repens (W. Bartram) Small in mesic and Diospyros virginiana L. in xeric, was more abundant in basal plots. In mesic environments, eight species had greater occurrence in open plots. In xeric environments, four understory forbs were more abundant in open plots. Our results support previous research indicating that individual pine trees are associated with significant variation in understory vegetation in pine savannas.
... Productivity and the mitigation of GHG should serve as guiding principles to prevent ecological issues such as increased emissions and soil C loss, as well as shortage or unaffordable prices of animal food products [30]. Tropical grasslands are renowned as biodiversity hotspots, hosting several endangered species and serving as a pillar for environmental preservation [32]. As previously mentioned, tropical grasses are frequently susceptible to quality oscillations due to climatic factors, especially during dry seasons, when the plant may exhibit reduced CP content and increased structural carbohydrates, resulting in diminished productivity and increased GHG emissions per unit of generated product (i.e., GHG emissions' intensity) [33,34]. ...
Citation: Krüger, A.M.; Lima, P.d.M.T.; Ovani, V.; Pérez-Marquéz, S.; Louvandini, H.; Abdalla, A.L. Ruminant Grazing Lands in the Tropics: Silvopastoral Systems and Tithonia diversifolia as Tools with Potential to Promote Sustainability. Abstract: Food security, sustainability of food production, and greenhouse gas (GHG) production of ruminant livestock are topics that generate scrutiny and debates worldwide. In a scenario of increasing human population and concerns with climate change, it is necessary to increase animal-derived food in sustainable operations. Grazing systems are crucial for ruminant production worldwide, and in the tropics, well-managed grasslands can provide sustainable intensification of this activity. In these regions, production often relies on grass monoculture managed extensively, a practice that commonly has led to the occurrence of degraded soils, limited animal productivity, and increased intensity of GHG emissions. Silvopastoralism is a practice that promotes several ecosystem services, showing potential to maintain soil quality while reducing the environmental impacts of ruminant production. These systems also have the potential to improve animal productive performance and reduce GHG emissions. The review was guided by a search in the Web of Science database using population terms and refined by document type (Article) and language (English OR Portuguese) following PRISMA protocol. Infographics were created using the Bibliometrix package in R software (version 4.3.2), and a specific topic on Tithonia diversifolia (Hemsl.) A. Gray was explored to demonstrate the importance of this forage resource for tropical silvopastoral systems and its potential contribution to food security. The T. diversifolia shrub is widely distributed in Latin America and tropical regions and presents several characteristics that make it a good option for silvopastoral systems. Focusing on the tropics, our objectives were to present one literature review addressing the role of grazing ruminant production towards the current climate change and food security challenges. Additionally, we aimed to explore the state of knowledge on silvopastoral systems and the use of T. diversifolia, presenting their potential to cope with this scenario of increased concerns with the sustainability of human activities.
... By grouping spatially distinct biological communities with different species compositions, biomes therefore attempt to make these communities uniform to provide some form of standardized comparison. For example, mapping biome distributions in conservation biology provides the basis for drawing the boundaries of endangered areas and habitats at a global scale in a standardized way (e.g., Bond & Parr, 2010;Brancalion et al., 2019;Dinerstein et al., 2017;Olson et al., 2001;Olson & Dinerstein, 1998). Another example pertains to the assessment of human land-use impacts on the biosphere, which includes the concept of anthropogenically defined biomes ("anthromes") (Dinerstein et al., 2017;Ellis & Ramankutty, 2008) that provides a means to compare human-modified systems across regions (Bodart et al., 2013;Ellis & Ramankutty, 2008;Loveland et al., 2000;Myneni et al., 1997). ...
Biomes are large‐scale ecosystems occupying large spaces. The biome concept should theoretically facilitate scientific synthesis of global‐scale studies of the past, present, and future biosphere. However, there is neither a consensus biome map nor universally accepted definition of terrestrial biomes, making joint interpretation and comparison of biome‐related studies difficult. “Desert,” “rainforest,” “tundra,” “grassland,” or “savanna,” while widely used terms in common language, have multiple definitions and no universally accepted spatial distribution. Fit‐for‐purpose classification schemes are necessary, so multiple biome‐mapping methods should for now co‐exist. In this review, we compare biome‐mapping methods, first conceptually, then quantitatively. To facilitate the description of the diversity of approaches, we group the extant diversity of past, present, and future global‐scale biome‐mapping methods into three main families that differ by the feature captured, the mapping technique, and the nature of observation used: (1) compilation biome maps from expert elicitation, (2) functional biome maps from vegetation physiognomy, and (3) simulated biome maps from vegetation modeling. We design a protocol to measure and quantify spatially the pairwise agreement between biome maps. We then illustrate the use of such a protocol with a real‐world application by investigating the potential ecological drivers of disagreement between four broadly used, modern global biome maps. In this example, we quantify that the strongest disagreement among biome maps generally occurs in landscapes altered by human activities and moderately covered by vegetation. Such disagreements are sources of bias when combining several biome classifications. When aiming to produce realistic biome maps, biases could be minimized by promoting schemes using observations rather than predictions, while simultaneously considering the effect of humans and other ecosystem engineers in the definition. Throughout this review, we provide comparison and decision tools to navigate the diversity of approaches to encourage a more effective use of the biome concept.
... Interestingly, we found that FD was comparable across both species' pools for Grassland vegetation and higher among the pool of available seed for Rainforest and vine thicket vegetation types ( Figure 4). However, these results should not overshadow the many complexities associated with the conservation and restoration of grassland (Bond & Parr, 2010;Buisson et al., 2022;Silveira et al., 2022;Török et al., 2021) or rainforest ecosystems (Doust et al., 2008;Kanowski, 2010;Pohlman et al., 2021). For Grasslands, our results may imply that there is less functional variation among grassland species compared with other vegetation types for the given traits studied (e.g. ...
Societal Impact Statement
Large quantities of diverse native seeds are required to scale up global restoration efforts. However, it remains unclear for many ecosystems how the diversity of available seed in commercial stocks reflects the composition of the ecosystems where vegetation is being remade. This study highlights existing shortfalls in the diversity of seed presently available for use in restoration and identifies gaps in the seed supply chain while providing a new method for optimising species selection given these constraints. This work underscores how improved collaboration between stakeholders is required to strengthen the seed supply chain and help remake functionally diverse vegetation.
Summary
Restoration using native seed is frequently implemented to restore degraded ecosystems. However, it remains unclear how constraints on the diversity of germplasm available for use in restoration may limit the recovery of both species and plant functional diversity.
Using a dataset of seed availability for Australia's major vegetation types, we explore variation in the diversity and breadth of functional traits (leaf mass per area, seed mass, plant height) for species where seed is available on commercial markets relative to unavailable. Using these data, we simulate theoretical seed mixes derived from two species pools: (1) constrained by the current market of commercially available seed, and (2) assuming all native species can be planted; then we compare differences in functional diversity (dispersion) as an exercise to explore possible limitations within the current seed supply.
Seed from only 12% of Australian plant species (2992 species) is presently available for immediate purchase. Seed was more frequently available for trees and shrubs than for understorey species. Available species were on average taller, with thicker, longer‐lived leaves than unavailable species. Overall, functional dispersion was lower for seed mixes generated using available seed compared with those drawn from all species.
Solutions are required to address seed shortfalls so that plantings are not only species rich but also functionally diverse. We develop two options: (1) quantifying and addressing gaps in the seed supply chain that currently limit the capacity for practitioners to restore diverse vegetation; and (2) applying a trait‐informed species‐selection method to plantings that maximises functional diversity using available seed.
... Although the reduction in vine coverage may be beneficial if vines are outcompeting forbs, understory trees often are the most important vegetation competing with herbaceous plants (Harrington andEdwards 1999, Whelan et al. 2018). Dormant-season fire tends to be less effective at reducing tree coverage compared to fire during various portions of the growing season (Bond and Parr 2010, Resop et al. 2023, Robertson and Hmielowski 2014. Thus, managers may consider using fire during other seasons if shifts in plant composition are desired. ...
Pinus spp. (pine) forests are common throughout the southeastern US, and many of these forests are managed to improve habitat for Odocoileus virginianus (White-tailed Deer) and Meleagris gallopavo (Wild Turkey). Previous studies have investigated the influence of forest management on deer and turkey habitat, but several aspects of understory vegetation response to management are not well understood. We measured understory composition and structure, overstory basal area, and deer-forage availability at 8 sites in summer 2020. Previous history of dormant-season fire increased grass and decreased vine coverage, but forb and understory tree coverage were not influenced. Vegetation providing visual obstruction for turkey nesting and deer fawning was correlated with increased coverage of semiwoody and woody plants. Forb coverage averaged 14% and was positively correlated with deer nutritional carrying capacity (NCC) using a 14% protein constraint. Conversely, NCC with a 6% protein constraint correlated with shrub and vine coverage. Sunlight available to the understory was most strongly influenced by hardwood overstory and midstory trees. Our results indicate that understory composition strongly influences forage and cover and that pine stands that are not intensively managed generally provided limited resources for deer and turkeys.
... As Ochre-breasted pipits live in grasslands that have been evolutionarily influenced by fire disturbance, such as the Cerrado (Lombardi 2017) and the South Brazilian Highland Grasslands (Beal-Neves et al. 2020;Chiarani et al. 2020), the species is supposed to exhibit some resilience within the range of natural variation in the fire regime, as expected for organisms associated with fire-prone environments (Cody 1985;Bond and Parr 2010;Durigan and Ratter 2016). However, the natural fire regime of grasslands has been greatly altered by humans, either by modifying its main aspects (intensity, severity, frequency and seasonality) or by its total suppression (Sodhi et al. 2011). ...
The Ochre-breasted pipit Anthus nattereri is a terrestrial bird
restricted to natural grasslands of south-eastern South America.
The species is globally Vulnerable to extinction and its natural
history is still poorly known. We investigated the breeding biology
of Ochre-breasted pipits, commenting on its habitat use and the
potential impacts of local grasslands management practices with
fire on the species’ conservation. Fieldwork took place mainly
between January and December 2016 in the Upper Rio Grande
Grasslands, south-eastern Brazil. Five nests of the species were
found between September and November, one of them recently
destroyed by fire. Nests were cup shaped and placed on the
ground, being built with dry grasses, resembling the pattern
documented for other species of Anthus. The eggs were covered
with brownish spots and dots to a variable extent and the back-
ground colour ranged from greyish white to brownish white. The
egg colour pattern also fell within the known range of variation for
congeneric species, as did the clutch size (two to three eggs)
observed in tropical species of Anthus. Ochre-breasted pipits
tended to occupy nesting sites with higher and denser grass
cover (eg small patches of vegetation that survived the last fire
event) when compared to non-nest sites located in adjacent
recently burned areas, which potentially suggests a preference
for such habitat attributes. Although the Ochre-breasted pipit is
relatively common in the study area, the highest temporal inci-
dence of fire coincides with its breeding season, which can directly
impact the local population through the burning of nests and the
elimination of suitable nesting sites. Thus, it is important to con-
duct long-term studies to evaluate the impact of different fire
regimes on the reproductive performance of Ochre-breasted
pipits, thus allowing the design of better ecosystem management
practices to guarantee its conservation.
... Cerrado is an important tropical grassy phytogeographic domain that harbors a unique biodiversity and provides significant ecological services to humankind (Bond and Parr, 2010;Overbeck et al., 2015;Parr et al., 2014). Despite its importance, this ecosystem have been neglected regarding conservation public policies and are facing considerable threats due to human disturbance (Klink and Machado, 2005;Overbeck et al., 2015). ...
... Threats to TGB are not only due to different degradation pressures but also because of historical misunderstandings, undervaluation and insufficient knowledge and protection (Parr et al., 2014;Pausas & Bond, 2019;Pilon et al., 2023;Silveira et al., 2022;Tölgyesi et al., 2022). Despite covering nearly 40% of the land (Dinerstein et al., 2017), a restoration policy, science and practice framework for TGB is still in their infancy (Silveira et al., 2022) given that clear definitions of reference ecosystems have emerged only recently (Bond & Parr, 2010;Veldman et al., 2015). For example, despite the long history of TGB degradation, the first field TGB restoration experiment (Lovera & Cuenca, 1996) was published nearly a century after Warming's (1895) seminal plant ecology book based on Neotropical savannas ( Figure 1). ...
Scientists and policymakers are becoming aware of the pressing need to restore tropical grassy biomes (TGB), which are home to unique biodiversity and provide essential ecosystem services to hundreds of millions of people. TGB face increasing threats, including forest‐ and tree‐centric restoration approaches that promote their degradation and we still lack a systematic assessment of where and how TGB restoration research has been done to guide policy and practice.
We synthesized knowledge on field restoration experiments by conducting a systematic literature review to map TGB restoration field studies, examine the association of restoration techniques and degradation sources and investigate the diversity of indicators used to monitor restoration outcomes.
TGB restoration was concentrated at Brazilian and Australian savannas, with large blindspots in Asia, Africa and northern and western South America. Studies were largely context‐dependent, with an inconsistent usage of restoration techniques to different sources of degradation. Less than half of the indicators evaluated were monitored consistently through time, often using a low‐dimensional approach related to ecosystem functioning. Few studies manipulated fire, herbivores and soils, the key drivers for the re‐establishment of TGB dynamics. Unfortunately, many studies lacked negative (degraded ecosystems), positive (reference ecosystems) controls, or both, impairing attempts to robustly determine restoration outcomes.
Our overview of field research on TGB restoration highlights that research needs improvement to refine our ability to assess, plan, implement and monitor restoration. Severe issues with experimental designs and data reporting are identified as barriers to find generality and upscale TGB restoration to meet the goals of the UN Decade on Ecosystem Restoration.
Synthesis and applications. Our synthesis calls for enhanced field experiments, transparent data reporting and quantitative syntheses to guide large‐scale TGB restoration. The overall lack of knowledge on improving resilience and measuring outcomes hampers meaningful comparisons between studies and hinders synthetic views essential for determining appropriate restoration techniques for different degradation sources and suitable monitoring indicators. To overcome the scarcity of reliable and transparent data supporting TGB restoration, we propose a simple checklist for minimum research reporting information and more complete multilingual standardized guidelines.
... Grasses are integral parts of vegetated landscapes forming the foundation of countless terrestrial ecosystems, including agricultural landscapes upon which human life depends, and are overrepresented as nonnative invasive species globally (Bond and Parr 2010;Linder et al. 2018;Strömberg and Staver 2022). Investigating dispersion and establishment patterns for introduced grasses over large timescales is therefore essential for understanding how human-mediated grass introductions have and continue to cause vast changes in the composition of floras worldwide (Westphal et al. 2008;Seebens et al. 2015;Strömberg and Staver 2022). ...
Premise of research. Little is known about the establishment success of grasses after their introduction into new areas. Using herbarium data, we investigated temporospatial patterns in the survival, establishment, and spread of grasses introduced to eastern North America through solid ballast deposition from the pre-twentieth-century shipping trade.
Methodology. We identified 95 grass species introduced to New Jersey via ballast deposition and used 2729 digitized and georeferenced plant specimens from 63 herbaria to quantify their establishment and dispersion. Anselin Local Moran’s I measure of local spatial autocorrelation revealed the earliest and most recent areas of invasion by ballast grasses irrespective of collection intensity. Species’ native ranges were used to evaluate the differential establishment and dispersion of species from different biogeographic realms.
Pivotal results. Of all the species (95), 51% did not survive after ballast deposition ended (waifs), 8% died out shortly thereafter (short-term), and 41% became established in New Jersey.Of the established species,41% are widespread (established-widespread), and 59% are still primarily found near shipping ports and railroads (established–limited spread). These species are mostly native to the Palearctic (77%; 44%to the Mediterranean and 33%to northern Europe), followed by the Neotropics (11%), the Afrotropics (10%), and the southeastern United States (4%). The establishment proportion for species native to more than one biogeographic region (72%) was four times greater than that for species native to a single region (18%). Additionally, 95% of established species, including all established-widespread species, are native to the Eastern Hemisphere.
Conclusions. We present the first analysis of the establishment proportion for a large set of grasses introduced through a single vector to a single area.We show the impact of biogeographic origin on the establishment proportion of introduced grasses and highlight the utility of herbarium collections for studying nonnative species’ history.
Keywords: establishment rates, grasses (Poaceae), herbarium collections, invasion biology, nonnative plants, transatlantic trade.
... In the early-fire treatment, although the number of species was more variable among plots (Q1 = 3, Q3 = 9), the range in plot-level richness was broadest (0-18) and there was a high diversity of dicots and non-graminoid monocots present in individual plots. In contrast to the no-fire treatment, the application of frequent fire facilitated increased richness, with a diversity of ground layer species benefitting from disturbance and/or open canopy, as observed in savannas worldwide (Peterson and Reich, 2008;Bond and Parr, 2010;Pinheiro et al., 2016). Given that pyrodiversity is not linearly correlated with biodiversity benefits, some fire patterns might be of higher conservation importance (Parr and Andersen, 2006). ...
Background and Aims
Little is known about the response of ground layer plant communities to fire in Miombo ecosystems, which is a global blind spot of ecological understanding. We aimed: (1) to assess the impact of three experimentally imposed fire treatments on ground layer species composition and compare it with patterns observed for trees; and (2) to analyse the effect of fire treatments on species richness to assess how responses differ among plant functional groups.
Methods
At a 60-year-long fire experiment in Zambia, we quantified the richness and diversity of ground layer plants in terms of taxa and functional groups across three experimental fire treatments of late dry-season fire, early dry-season fire and fire exclusion. Data were collected in five repeat surveys from the onset of the wet season to the early dry season.
Key Results
Of the 140 ground layer species recorded across the three treatments, fire-maintained treatments contributed most of the richness and diversity, with the least number of unique species found in the no-fire treatment. The early-fire treatment was more similar in composition to the no-fire treatment than to the late-fire treatment. C4 grass and geoxyle richness were highest in the late-fire treatment, and there were no shared sedge species between the late-fire and other treatments. At a plot level, the average richness in the late-fire treatment was twice that of the fire exclusion treatment.
Conclusions
Heterogeneity in fire seasonality and intensity supports diversity of a unique flora by providing a diversity of local environments. African ecosystems face rapid expansion of land- and fire-management schemes for carbon offsetting and sequestration. We demonstrate that analyses of the impacts of such schemes predicated on the tree flora alone are highly likely to underestimate impacts on biodiversity. A research priority must be a new understanding of the Miombo ground layer flora integrated into policy and land management.
... However, they are rarely mentioned in the Florida and the southeastern coastal plain literature (Abrahamson et al. 2021;Noss 2018;Peet et al. 2018). Many global studies (Bond and Parr 2010;Pennington and Hughes 2014;Gomes et al. 2019Gomes et al. , 2021Lamont et al. 2017;Meller et al. 2021Meller et al. , 2022Corkalo 2023;Rickenback 2022) provide phylogenetic evidence for fire adaptation in geoxyles (Simon et al. 2009;Simon and Pennington 2012;Maurin et al. 2014). Their aerial stems are highly susceptible to annual or biennial fires, while their wellprotected extensive belowground suffrutices with carbohydrate reserves afford rapid resprouting from bud banks (Fig. 7) . ...
Fire-adaptive traits in plants of tropical and subtropical grassy ecosystems have been the subject of considerable global research, but only recently studied in pyrogenic Florida subtropical grasslands. Plant growth forms, belowground organs, and post-fire recovery strategies were studied for 198 grassland specialists in peninsular Florida. Community types (dry-mesic, mesic, wet-mesic, and wet) were sampled with 1m ² plots along the edaphic-hydrologic gradient and the association between these variables and fire-related plant traits was tested using fourth-corner analysis. Caulescent herbs (43), cespitose graminoids (27), and rosette herbs (31) are the most common growth forms among species sampled. Plants with epigeogenous and hypogeogenous rhizomes dominate the sample plots, including matrix graminoids, shrub geoxyles, and an acaulescent rhizomatous fire-resilient palm ( Serenoa repens ). Most species (163; 82%) exhibit resprouting, including 30 facultative resprouters and 133 obligate resprouters. All woody rhizomatous species are obligate resprouters, and 35 ephemeral herbaceous species are obligate reseeders. Community type was a better predictor of species abundances than hydrology, however, hydrology was significantly associated with species traits measured, particularly rhizome texture, with woody rhizomes prevalent in all but the wet sites. Belowground organs (xylopodia, geoxylic suffructices) and growth form were associated with frequent fire and phylogeny, suggesting fire regime as a driver of community phylogenetic diversity. Persistence, rapid resilience and co-occurrence of geoxyles align Florida subtropical grasslands with other global geoxyle grasslands. The old-growth, pyrogenic grassy ecosystems of peninsular Florida are the center of geoxyle diversification on the southeastern US coastal plain.
... Grasslands have historically been neglected regarding their biological diversity as a priority for conservation when compared to forest ecosystems. Grasslands are easier to convert into monocultures than forests but grassland fragmentation does not have the same public censorship as forest deforestation (Bond & Parr, 2010;Overbeck et al., 2015). Therefore, new research on anurans should be developed as they are important in assessing the real impact of habitat loss and fragmentation of open areas in anuran communities and may help in the conservation of the South Brazilian grasslands' biodiversity. ...
Most species-rich communities consist of a limited number of common species and many rare species. This widespread ecological pattern can arise due to the predominance of either niche-based or neutral-based processes in community structuring. We tested two hypotheses related to this pattern for an anuran metacommunity composed of 35 species distributed in 187 ponds in the South Brazilian grasslands: (1) for common species, niche processes should prevail over neutral ones because common species evolved under a wider range of ecological filters than rare species; (2) for rare species, neutral processes should prevail because rare species are more prone to ecological drift and dispersion limitation. We found that the densities of both common (i.e., the 25% higher density ones) and rare (i.e., the 75% lower density ones) species depended mostly on pond structure and land use, indicating a similar response to niche-based processes in both groups of species. The importance of pond descriptors and type of land use, however, differed between the two groups, confirming that common and rare species represent ecologically distinct groups within the metacommunity. In addition, neutral processes—related to dispersion limitation or not—influenced both species groups, but the spatial filters selected explained a smaller portion of the variation in species densities compared to environmental descriptors. Our findings showcase the prevalence of niche processes in structuring communities of common and rare species of anurans in subtropical grasslands and indicate the variables of pond structure and land use that are relevant to guide conservation practices for the metacommunity of anurans in the South Brazilian grasslands.
... Grasslands with restricted distributions are found in montane regions across the tropics (Buytaert et al. 2011;Dixon et al. 2014), where they often form a mosaic with tropical montane forests (Kessler 2000;Burgess et al. 2007;Bond and Parr 2010). These tropical montane grasslands often host unique species assemblages and endemic taxa, and are critical for the conservation of montane biodiversity (Buytaert et al. 2011;Burgess et al. 2007;Sankaran 2009). ...
South India’s Western Ghats are a global biodiversity hotspot and an area of conservation concern with numerous endemic species. There is an urgent need for accurate threat assessments for these species, including the Nilgiri Pipit (Anthus nilghiriensis). The Nilgiri pipit is endemic to the montane grasslands of the Western Ghats, and has experienced recent rapid habitat declines. Here, we characterize the climatic niche of this species using environmental niche modelling, and use these models to estimate its range and threat status. Using the Maxent modelling algorithm and presence data from surveys by expert observers, we find that the Nilgiri Pipit is strongly sensitive to higher temperatures. We project the best-performing models to the last glacial maximum and find evidence that the species had a considerably larger range under that climatic regime. We estimate that the extent of suitable available habitat is no more than 436 km2 even using the most conservative threshold. Based on this result, and the documented decline in and fragmentation of its habitat, we recommend that the species be uplisted to “endangered” on the IUCN Red List, from its current status of “vulnerable”. Finally, we compare these results to models based on identically processed eBird data, and find that eBird data produce larger estimates of suitable habitat: we, therefore, recommend caution in the interpretation of environmental niche models based on eBird data.
... Crinum bulbispermum was chosen for this study because it is widespread in the Highveld of South Africa. It is a bulbous geophyte that lies dormant over winter, surviving with a large (up to 9 kg) underground storage organ which is protected from frost, drought, grazing, and fire [60,61]. Moreover, it has the added advantage of being a carbon sequester, considering its large underground storage organ, and its contracting roots prevent soil erosion [60]. ...
Ancient grasslands are lost through transformation to agriculture, mining, and urban expansion. Land-use change leads to ecosystem degradation and a subsequent loss of biodiversity. Globally, degraded grasslands have become a priority for restoration efforts to recover lost ecosystem services. Although the ecological and social benefits of woody species and grasses are well documented, limited research has considered the use of forbs for restoration purposes despite their benefits (e.g., C sequestration and medicinal uses). The aim of this study was to determine if Crinum bulbispermum (Burm.f.) Milne-Redh. & Schweick., a medicinal geophyte, could form part of restoration initiatives to restore mine soils in grasslands of the South African Highveld. A pot experiment was conducted to assess the performance of C. bulbispermum in a random design, with three soil treatments varying in level of degradation and metal contamination. The plants were monitored for 12 months, and the morphological characters were measured monthly to assess performance and survival. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the soil and plant tissue concentration of potentially toxic metals. The results indicated that mine tailings negatively affected the growth and development of C. bulbispermum. Although the survival rates indicated that it could survive on tailings, its below-par productivity indicated that the species is not ideal for restoration purposes unless the tailings are ameliorated with topsoil. Although there was root accumulation of metals (Co, Cd, Cu, Mo, and Zn), there was no translocation to the bulbs and leaves, which makes C. bulbispermum suitable for medicinal use even when grown on metal-enriched soil. This species may not be viable for phytoremediation but is a contender to be used in phytostabilization due to its ecological advantages and the fact that it does not accumulate or store metals. These findings underscore the importance of considering geophytes in grassland restoration strategies, expanding their ecological and societal benefits beyond conventional approaches.
... In contrast, single-species forestry plantations, especially of exotic species that are managed to maximise C gain and wood production, could reduce natural habitat, contribute to habitat fragmentation and accelerate species loss. Natural grasslands for example, have been extensively converted to croplands, pastures, agroforestry and production forestry such that much of the remaining natural grasslands are now threatened (Bond and Parr, 2010). Because of their perceived low commercial and ecological value relative to forests (Tölgyesi et al., 2021), low-productivity grasslands are prime targets for afforestation, thereby contributing to further grassland loss (Parr et al., 2014). ...
... The forest-savanna mosaics, as their name suggests, occur at the mesic limits of the savanna biome where savannas transition into closed-canopy forests. The savannas at these regions are densely wooded and structurally begin to approach the appearance of slightly open forests, but grasses are still dominant in the understorey (Bond and Parr, 2010;Ratnam et al., 2011). ...
... The geographic distribution of available barcodes depicts a paucity of bat and bird barcodes from many countries along the northern bounds of the Afrotropical realm, as well as from most of Angola and Somalia (Fig. 1). There is also notable under-representation of DNA barcodes from the most extensive Afrotropical biome, tropical and subtropical grasslands and savanna (Fig. 1), despite increasing biodiversity surveying of these ecosystems (Bond and Parr 2010;Huntley et al. 2019a;Petermann and Buzhdygan 2021). Sampling is highly clustered in the montane grassland biome of South Africa, and discontinuously within the moist broadleaf forests from Kenya through Central Africa to Sierra Leone. ...
Cryptic species present a challenge for conservation, as species diversity may remain undetected. In zoological research, DNA barcoding of the mitochondrial cytochrome c oxidase subunit I (COI) has become a useful heuristic tool for aiding species resolution and informing species discovery. Despite concerted efforts to genetically barcode bats and birds, comprehensive assessments have yet to be undertaken across the Afrotropics. We retrieved available DNA barcodes of native breeding Afrotropical bat and bird species. Using Bayesian phylogenetic modelling, we assessed DNA barcode performance at species identification, and sought to detect notable intraspecific clade partitioning hinting at cryptic speciation. Available DNA barcodes represent only 42.3% and 23.6% of the relevant bat and bird species diversity, respectively, with only 18.7% of bat species and 7.2% of bird species having geographically spread records. DNA barcodes afforded greater taxonomic resolution of Afrotropical bird species than of bats (96.8% vs. 84.0%), with bats having a higher proportion of species non-monophyly (25.5% vs. 4.8%). Well-supported (≥ 95% posterior probability) clade partitioning was inferable from twenty-one bat species and fifteen bird species, and a further single under-sampled bat species and fifteen such bird species showed deep (> 2.0%) intraspecific divergences. These phylogenetic signatures allude to cryptic speciation within these volant taxa, and serve to prompt more comprehensive assessments of Afrotropical fauna. These findings also indirectly affirm the importance of paleoclimatic refugia to endemic vertebrate diversity. The current taxonomic status of birds is better supported by this molecular evidence than that of bats.
... These land-use changes impact biodiversity (Overbeck et al., 2007(Overbeck et al., , 2013Roesch et al., 2009;Bond and Parr, 2010;Bolzan et al., 2016;Redin et al., 2017), plant water availability and river flow in watersheds Ferreto et al., 2021a, b), and soil degradation (Rodrigues et al., 2014(Rodrigues et al., , 2018Reichert et al., 2016;Valente et al., 2020Valente et al., , 2021Ebling et al., 2021). Another possible factor that contributes to the degradation of the Pampa is the lack of preservation and preservation consistent with the grassy characteristics of the biome. ...
Pampa biome vegetation is characterized by extensive areas of native grassland, interspersed with forests close to water courses. An understanding is been searched on how grassland and forest dynamics to contribute for the conservation and management practices suitable for the biome. The objective of this study was to asses if landscape-soil-pollen relationships are determinant of grassland-forest mosaics, by analyzing summit, footslope
and toeslope positions in the landscape, in the Campanha region of the Pampa biome. We collected 32 samples in three soil profiles in topossequence under natural grassland of the Pampa biome, in southern Brazil. These samples were treated following standard methodology used in palynology studies. The pollen percentage diagrams were generated to represent the identified pollen set, while cluster analysis was used to define the paleoecological zones. The results found were supported by radiocarbon dating (age of subsurface soil varying from 3,460 to 4,090 calibrated years before present), and particle-size analysis. The paleoecological zones, for each soil profile, indicate a predominance of grassland vegetation, especially Poaceae pollen, whereas Fabaceae and Piper were predominant in forest sites. The pollen set obtained in the three soil profiles indicates hegemony of the sites, even under climatic conditions of increased moisture. Rare pollen grains from forest taxa suggests
that trees and shrubs existed in isolated form. The presence of bryophyte spores and taxa associated with soil wetness indicates that the region was once dominated by extensive wetlands and moist landscapes. Our findings enhance the comprehension of the Pampa flora, and are applicable in restoration of degraded areas. The preservation of pollen grains in soil profiles shows the potential of minerals soils to reconstitute Pampa biome vegetation, representing a site for palynological research advance, and demonstrate grassland formations maintain their supremacy even under unfavorable climatic conditions. Thus, this study expands the frontier of palynological work, encompassing new sites and new opportunities to evaluate land use/land cover changes.
... Savanna ecosystems harbor high plant biodiversity (Bond & Parr, 2010;Myers et al., 2000;Nerlekar et al., 2022) and provide critical ecosystem services, such as palatable plant biomass for grazing herbivores (Solbrig et al., 2013;Staver & Hempson, 2020). Fires in savanna ecosystems date back to the Late Glacial and Holocene periods (Kellman, 1975;Riedel et al., 2021) and are major factors influencing their diversity and composition (Bessie & Johnson, 1995;Bond & van Wilgen, 2012). ...
Human activities in mesic savanna ecosystems have resulted in plant communities that are heavily dominated by fire‐tolerant grass species, are less diverse, and offer fewer ecosystem services such as palatable plant biomass. Experimental studies manipulating fire and grass presence have mostly been conducted in ecosystems invaded by exotic grass species. However, these experiments are also relevant to ecosystems that have become dominated by native grass species due to changes in human activities. Our study compared three different management treatments in the Eastern Ghats of India, where mesic savanna ecosystems are highly dominated by the unpalatable native Cymbopogon grasses, specifically: (1) control (both Cymbopogon grasses and fire are present), (2) fire exclusion, and (3) manual removal of Cymbopogon grasses and fire exclusion. We found that both grass removal and fire exclusion were necessary to significantly increase palatable herbaceous plant biomass and species diversity, and that species diversity responses were only significant at larger spatial grains of investigation. High site‐to‐site variation in the grass removal and fire exclusion treatment prevented us from detecting significant differences in species composition across treatments, even though particular palatable grass species benefited from the treatment. Our study is in line with research from other mesic savanna systems showing that fire management alone is not sufficient to transition ecosystems to a desired or historical state. We demonstrate how normally costly management practices, such as manual removal of dominant grasses, can be reasonably achieved through collaboration between scientists, community governed village institutions, and government and nongovernment agencies in socioecological systems.
... The evolution of savanna ecosystems began in the Miocene or early Pliocene some 8-5 Mya (Cerling et al., 1998). This long evolutionary history of grassy ecosystems has resulted in high levels of plant diversity in savannas and grasslands (Bond & Parr, 2010;Veldman, 2016). ...
Woody plant encroachment (WPE) is a global trend that occurs in many biomes, including savannas, and accelerates with fire suppression. Since WPE can result in increased storage of soil organic carbon (SOC), fire management, which may include fire suppression, can improve ecosystem carbon (C) sequestration in savannas.
At our study site in Kruger National Park, South Africa, we used a long‐term (~70 year) fire experiment to study the drivers and consequences of changes in woody cover (trees and shrubs) on SOC sequestration. We surveyed four fire manipulation treatments, replicated at eight locations within the park: annual high‐intensity burns, triennial high (dry season) and low‐intensity (wet season) burns, and fire exclusion, to capture the range of fire management scenarios under consideration. The changes in woody cover were calculated over a period similar to the experiment's duration (~80 years) using aerial photographs (1944–2018). Soils were analysed to 30 cm depth for SOC and δ¹³C, under and away from the tree canopy to isolate local‐ and landscape‐level effects of WPE on SOC.
The largest increases in woody cover occurred with fire exclusion. We found that plots with higher increases in woody cover also had higher SOC. However, trees were not the only contributor to SOC gains, sustained high inputs of C4‐derived C (grasses), even under canopies in fire suppression plots, contributed significantly to SOC. We observed little difference in SOC sequestration between cooler triennial (wet season) burns and fire suppression.
Synthesis. Grass input to soil organic carbon (SOC) remained high across the full range of woody cover created by varying burning regimes. The total SOC stocks stored from tree input only matched grass‐derived SOC stocks after almost 70 years of fire exclusion. Our results point to C4 grasses as a resilient contributor to SOC under altered fire regimes and further challenge the assumption that increasing tree cover, either through afforestation schemes or fire suppression, will result in large gains in C sequestration in savanna soils, even after 70 years.
... In areas where these conversions occurred, many of the remaining are of low quality with limited recoverability . Grassland conservation and restoration are legally mandated in many countries and international standards have been developed (McDonald et al., 2019), yet these actions remain undervalued and underfunded (Bond and Parr, 2010;Török et al., 2021;Tölgyesi et al., 2022a). Recent biodiversity research demonstrates that many of the plant species that have decreased in abundance in the last century require grassy biomes (Jandt et al., 2022), underlining the contribution of grasslands to maintaining healthy food webs and ecosystems. ...
Grasslands are ubiquitous globally, and their conservation and restoration are critical to combat both the biodiversity and climate crises. There is increasing interest in implementing effective multifunctional grassland restoration to restore biodiversity concomitant with above- and belowground carbon sequestration, delivery of carbon credits and/or integration with land dedicated to solar panels. Other common multifunctional restoration considerations include improved forage value, erosion control, water management, pollinator services, and wildlife habitat provisioning. In addition, many grasslands are global biodiversity hotspots. Nonetheless, relative to their impact, and as compared to forests, the importance of preservation, conservation, and restoration of grasslands has been widely overlooked due to their subtle physiognomy and underappreciated contributions to human and planetary well-being. Ultimately, the global success of carbon sequestration will depend on more complete and effective grassland ecosystem restoration. In this review, supported by examples from across the Western world, we call for more strenuous and unified development of best practices for grassland restoration in three areas of concern: initial site conditions and site preparation; implementation of restoration measures and management; and social context and sustainability. For each area, we identify the primary challenges to grassland restoration and highlight case studies with proven results to derive successful and generalizable solutions.
... wildl ife.org). Tropical montane grasslands hold significant biodiversity, with endemic species that are unique to this biome (Bond & Parr, 2010). Like other tropical montane ecosystems, the grasslands are experiencing high levels of landscape modification from human activities, as these open areas with stable rains are conducive to conversion to agricultural fields and tree plantations (Arasumani et al., 2018;Farley, 2007;Hermann et al., 2016). ...
Human modification of the environment has drastically changed ecosystems around the globe. While forest‐loss (deforestation) has been well studied for its effects on ecosystems, afforestation also has major impacts. The Udzungwa Plateau in Tanzania is naturally a mix of forests and grasslands. However, non‐native pine plantations have recently increased in the area displacing the native grasslands of the montane plateau. In this study, we explored the effects of land use change on amphibian communities by comparing amphibian surveys before non‐native plantations were introduced (~2000) and after (2017–2019). To put these amphibian surveys into wider context across the plateau and to distinguish local population loss compared to plateau‐wide extinctions, we sample diversity at new sampling locations and locations with multiple surveys through time. We then assessed landscape change through remotely sensed data and ground surveys. Amphibian encounter surveys found approximately the same species diversity across all sampling locations, but local extinctions appear likely. Remaining amphibians appear to be limited to small refugia in non‐pine wetlands. Approximately half (45%) of the species found have limited distributional ranges (<72,000 km ² ) and are described as habitat specialists by the IUCN Red List. Monitoring pine plantation growth using remote sensing techniques suggested only limited extensions of plantations between 2000 through to 2013–2016, but ground surveys found small pines (<3 years old) throughout almost all areas identified as grasslands on satellite imagery. Our study highlights the plight of this narrowing biome on the African continent and calls for more research on the impact of non‐native plantations on natural communities.
Abstract in Swahili is available with online material.
... During a fire event, bark notably prevents the heat from killing the cambium and inducing xylem deformation (Gashaw et al., 2002;Hacke et al., 2001;Lawes et al., 2013Lawes et al., , 2011Michaletz et al., 2012); it also protects buds located below its surface allowing future resprouting (Bond and Midgley, 2001;Burrows, 2002;Charles-Dominique et al., 2015;Chiminazzo et al., 2021). In ecosystems with fires fueled by grasses (e.g., savannas), fires are of low intensity and high frequency (Archibald et al., 2018;Bond and Parr, 2010). Hence, in savannas, the main survival strategy of woody species is to produce and accumulate bark fast enough (without bark shedding) before the next fire event to protect their aboveground parts, instead of accumulating a large amount of bark over a long period (Charles-Dominique et al., 2017). ...
Forbs (“wildflowers”) are important contributors to grassland biodiversity and services, but they are vulnerable to environmental changes that affect their coexistence with grasses. In a factorial experiment at 94 sites on 6 continents, we tested the global generality of several broad predictions arising from previous studies: (1) Forb cover and richness decline under nutrient enrichment, particularly nitrogen enrichment, which benefits grasses at the expense of forbs. (2) Forb cover and richness increase under herbivory by large mammals, especially when nutrients are enriched. (3) Forb richness and cover are less affected by nutrient enrichment and herbivory in more arid climates, because water limitation reduces the impacts of competition with grasses. We found strong evidence for the first, partial support for the second, and no support for the third prediction. Forb richness and cover are reduced by nutrient addition, with nitrogen having the greatest effect; forb cover is enhanced by large mammal herbivory, although only under conditions of nutrient enrichment and high herbivore intensity; and forb richness is lower in more arid sites, but is not affected by consistent climate-nutrient or climate-herbivory interactions. We also found that nitrogen enrichment disproportionately affects forbs in certain families (Asteraceae, Fabaceae). Our results underscore that anthropogenic nitrogen addition is a major threat to grassland forbs and the ecosystem services they support, but grazing under high herbivore intensity can offset these nutrient effects.
Prescribed burning is frequently used in savanna vegetation in Australia and worldwide. In north‐east Queensland savanna burning has been proposed for the control of woody weeds including Cryptostegia grandiflora (rubbervine), an invasive shrub/vine of riparian savanna. However, burning as a management tool can have non‐target impacts on ecosystems, particularly where associated with additional invasive species, such as the exotic stoloniferous grass species Bothriochloa pertusa (Indian couch). For this reason, an experiment was established to test for non‐target impacts of prescribed burning on herbaceous vegetation. The experiment consisted of wet and dry season burning, and single and double burning treatments during a 4 year study. Annual herbaceous surveys were conducted, both before treatments applied, and then annually. We addressed alternative hypotheses, that (i) burning would exacerbate grazing impacts resulting in negative outcomes for native herbaceous vegetation, or alternatively (ii) burning would be neutral or beneficial to native herbaceous assemblages due to savanna co‐evolution with fire. Burning treatments resulted in subtle but beneficial responses for native herbaceous vegetation. Native legume biomass, percent composition and percent frequency, and forb species richness, increased 4–5 months following wet season burning with above average rainfall. There was a delayed (8–18 months) positive response of burning (both wet and dry season) in percent composition of native grazing sensitive perennial grasses. There was a slight short‐term decline in introduced perennial grass percent composition and biomass following treatment. Results were consistent with predominantly positive or neutral responses to prescribed burning. There was no evidence to support the hypothesis that invaded native savanna herbaceous assemblages declined with burning treatment applications. These results are discussed in relation to other savanna studies in northern Australia and to the role of fire in the maintenance of herbaceous vegetation in savanna biomes.
Fire plays a key role in grasslands, determining the distribution and evolution of species and boundaries with neighboring ecosystems. Evidence of community-wide responses to fire is largely based on taxonomic and functional descriptors, while the phylogenetic dimension is overlooked. Here we evaluated how the taxonomic and phylogenetic structure of grassland plant communities responded to a time since fire (TSF) gradient. We sampled 12 communities in Southern Brazil under varying TSF and calculated taxonomic species richness (S) and dominance (D), phylogenetic diversity (PD), and mean phylogenetic distances (MPD). We used Structural Equation Models to test the relationships between the environmental gradient and community descriptors. Communities with longer TSF presented higher PD and MPD but lower species richness and increased taxonomic dominance. These sites were dominated by monocots, specifically C4 grasses, but also presented exclusive clades, whereas recently-burned sites presented lower taxonomic dominance and more species distributed in a wider variety of clades. Our results indicate that these scenarios are interchangeable and dependent on fire management. Fire adaptation was not constrained by phylogenetic relatedness, contrasting with previous findings for tropical savannahs and indicating that temperate and tropical non-forest ecosystems from South America respond differently to fire, possibly due to different evolutionary histories.
Feral hogs (Sus scrofa) are invasive, ecosystem engineers and a novel disturbance to rare, fire-dependent, herbaceous wetland ecosystems in Florida, USA. Their feeding activity uproots vegetation, altering plant composition and continuity. Hog rooting can also create linked disturbance by ingesting vegetation critical for fire spread. Herbaceous communities are vulnerable to shrub encroachment when fire return intervals are increased. We examined the impact of hog rooting intensity (% uprooted vegetation) on the resilience of herbaceous, seepage wetland vegetation cover and composition and the effect of hog rooting on fire spread. We hypothesized that (1) vegetation cover and composition would reflect initial intensity of hog rooting and remain altered with and without additional rooting, and (2) reduction of foliar cover by feral hog rooting would reduce fire spread. Total foliar cover, functional group cover, richness, and cover of plant genera were estimated in plots subjected to three intensity levels of hog rooting then appraised inside and outside of exclosures for 7 years. Spatial data was collected to compare areas with and without damage from hogs to areas burned by prescribed fires from 2010–2013. Total foliar cover was reduced for 5 years with high intensity hog rooting compared to no-low intensity rooting. Cover of a keystone, bunchgrass species was reduced with high intensity hog rooting. With repeated rooting, total and graminoid foliar cover were reduced outside exclosures. Fire spread was significantly reduced in areas of hog rooting. These findings have broader implications for conservation of other fire-maintained herbaceous communities impacted by nonindigenous feral hogs.
Radical and quick transformations towards sustainability will be fundamental to achieving a more sustainable future. However, deliberate interventions to reconfigure systems will result in winners and losers, with the potential for greater or lesser equity and justice outcomes. Positive tipping points (PTPs) have been proposed as interventions in complex systems with the aim to (a) reduce the likelihood of negative Earth system tipping points and/or (b) increase the likelihood of achieving just social foundations. However, many narratives around PTPs often do not take into account the entire spectrum of impacts the proposed alternatives could have or still rely on narratives that maintain current unsustainable behaviours and marginalize many people (i.e. do not take “b” into account). One such example is the move from petrol-based to electric vehicles. An energy transition that remains based on natural resource inputs from the Global South must be unpacked with an equity and justice lens to understand the true cost of this transition. There are two arguments why a critical engagement with these and other similar proposals needs to be made. First, the idea of transitioning through a substitution (e.g. of fuel) while maintaining the system structure (e.g. of private vehicles) may not necessarily be conceived as the kind of radical transformation being called for by global scientific bodies like the Intergovernmental Panel on Climate Change (IPCC) and Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). Second, and probably more importantly, the question of positive for whom, positive where, and positive how must be considered. In this paper, we unpack these narratives using a critical decolonial view from the south and outline their implications for the concept of tipping points.
Arid grasslands worldwide are transitioning to scrublands due to shrub encroachment, resulting in habitats with varying shrub cover. Shrubs play a crucial role in grassland ecosystems, offering trade-offs to rodents in terms of visibility, shelter, and food availability, thereby affecting their occurrence and distribution. This study explores the link between habitat characteristics and rodent activity and density, focusing on shrub presence. In the Tirunelveli district of southern India, we measured rodent density and activity across three grassland types with increasing shrub presence. Our findings reveal species-specific responses to shrub density. The Soft-furred rat (Millardia meltada) dominated, showing adaptability to different shrub levels, while the black rat (Rattus Rattus) was least represented. Fine-scale analysis indicates a positive association between shrub presence and rodent captures. Grassland obligate species like the Indian gerbil (Tatera indica) exhibited reduced activity in densely shrubbed sites, whereas semi-arboreal species like the Indian palm squirrel (Funumbulus palmarum) showed increased activity. This study underscores the importance of considering habitat structure in grassland ecosystem management for the conservation of rodent diversity and ecosystem health.
Woody encroachment (WE) and agricultural expansion are widespread in tropical savannas, where they threaten biodiversity and ecosystem function. In Africa's largest savanna, the miombo woodlands, cropland expansion is expected to cause extensive habitat loss over the next 30 years. Meanwhile, widespread WE is altering the remaining untransformed vegetation. Quantifying the extent of both processes in the Angolan miombo woodlands (~570,000 km ² ) has been challenging due to limited infrastructure, a history of conflict, and widespread landmines. Here, we analyze spectral satellite imagery to investigate the extent of WE and cropland expansion in the Angolan miombo woodlands since 1990. We asses WE using two complementary metrics: multi‐decade canopy greenness trends and conversion from grassland to woodland. We also examine whether WE trends are driven by landscape fragmentation and decreasing fire frequency. We found that from 1990 to 2020, 34.1% of the Angolan miombo woodlands experienced significant WE or was converted to cropland, while open grassy vegetation declined by 62%. WE advanced rapidly even in areas experiencing extraordinarily high burn frequencies and was not adequately explained by changing temperature or precipitation. WE was concentrated far from the agricultural frontier, in remote areas with low population densities. These results challenge the hypothesis that human‐altered fire regimes are the primary driver of WE in mesic savannas. The results will help decision‐makers conserve the miombo woodlands' biodiversity and ecosystem services, by highlighting that strategies to slow habitat loss must address WE and cropland expansion together.
Background and aims
In many systems, postfire vegetation recovery is characterised by temporal changes in plant species composition and richness. We attribute this to changes in resource availability with time since fire, with the magnitude of species turnover determined by the degree of resource limitation. Here we test the hypothesis that postfire species turnover in South African fynbos heathland is powered by fire-modulated changes in nutrient availability, with the magnitude of turnover in nutrient-constrained fynbos being greater than in fertile renosterveld shrubland. We also test the hypothesis that floristic overlaps between fynbos and renosterveld are attributable nutritional augmentation of fynbos soils immediately after fire.
Methods
We use vegetation survey data from two sites on the Cape Peninsula to compare changes in species richness and composition with time since fire.
Key results
Whereas fynbos communities display a clear decline in species richness with time since fire, no such decline is apparent in renosterveld. In fynbos, declining species richness is associated with declines in the richness of plant families having high foliar concentrations of nitrogen, phosphorus, and potassium, and possessing attributes which are nutritionally costly. By contrast, families which dominate late-succession fynbos possess adaptations for the acquisition and retention of sparse nutrients. At the family level, recently burnt fynbos is compositionally more similar to renosterveld than is mature fynbos.
Conclusions
Our data suggest that nutritionally driven species turnover contributes significantly to fynbos community richness. We propose that the extremely low baseline fertility of fynbos soils serves to lengthen the nutritional resource axis along which species can differentiate and coexist, thereby providing the opportunity for low-nutrient extremophiles to coexist spatially with more fertile adapted species. This mechanism has the potential to operate in any resource-constrained system in which episodic disturbance affects resource availability.
Brazil’s natural environments include a considerable cover of grasslands and savannas that have high and unique biodiversity. The South Brazilian grassland region (or Campos Sulinos, in portuguese) has received somewhat more attention in science over the past two decades, but remains neglected in conservation. This is especially true for the grasslands themselves that dominate natural landscapes in the Campos Sulinos region and that are currently suffering fast land use change. Clearly, the high biodiversity of South Brazilian grasslands and the important ecosystem services that they provide are not sufficiently considered in conservation politics nor in the public debate. This introductory chapter of the book ‘The South Brazilian grasslands: ecology and conservation of the Campos Sulinos’ presents a short guide through the terminology used for the region and its grasslands, summarizes tendencies of land use change and their consequences, and then provides a short overview of the key content of the different chapters of the book. The Chapter ends with brief comments on research and conservation needs. The future of the Campos Sulinos depends on halting the loss of grassland areas and implementing effective conservation methods.
Fire is a structuring factor of terrestrial ecosystems, such as the Brazilian Cerrado. But little is known about the patterns and adequate fire regularity in the various phytophysiognomies of this biome. Thus, we hypothesized that the control of fires at the Serra das Araras Ecological Station alters the small mammals’ assemblages, with the presence of more forest species. Thus, this work aims to evaluate the structure of the assemblages of small non-volant mammals of the SAES, after a period of 17 years without fire occurrence. Between October 2016 and June 2017, 24 sites in the Cerrado. The sampling effort was 13,960 traps per night of conventional Sherman and Tomahawk traps. Our results were compared with data sampled in 1999 and 2000, a period in which there was no fire control. 21 species of small mammals were recorded, of which 12 species of rodents and nine of marsupials. Our results show most species common to forest and savannah environments, differing from the pattern of other studies, in which they present a set of species restricted to forest environments, another set restricted to savannah environments, and few shared species. When comparing the current study and that of the year 1999/2000, species typical of savannah environments have been replaced by forest species. In this sense, it is possible to assume that the absence of fire is restructuring the small mammal assemblages at Serra das Araras Ecological Station.
Societal Impact Statement
Madagascar is famous for its unique forests and their fauna. Most of the island is covered by flammable grassy ecosystems long considered to be of human origin and threatening the remaining forests. Yet new studies show that many plants and animals of the grassy systems are unique to Madagascar and restricted to these open habitats. Open grassy ecosystems have markedly different management requirements from forests and bring different contributions to society. We argue that the grassy ecosystems can benefit Madagascar if understood and managed wisely using expanded knowledge bases that also include collaboration with locals.
Summary
Until recently, nearly all research and interests in Madagascar focused on forested habitats. To help place Madagascar's grassy ecosystems in context, we provide a summary of the origin, development, and evolution of open tropical, C4 grassy ecosystems elsewhere, especially those from Africa; we summarize similarities and differences with the distribution of C3 and C4 grasses in the Malagasy landscape, their plant traits, and inferences on the evolutionary legacy of grasses. We also discuss the animal communities that use and have coevolved in these grassy systems; to help resolve controversies over the pre‐settlement extent of grassy ecosystems, we suggest a variety of complementary geochemical, palaeobotanical, and molecular genetic tools that have been effectively used elsewhere to untangle forest/grassy ecosystem mosaics and the ecological and evolutionary processes that influence them. Many of these tools can and should be employed in Madagascar to fully understand the spatio‐temporal dynamics of open, grassy, and closed forest systems across the island; as regards conservation, we discuss the ecosystem services provided by grassy systems, which are too often ignored in general, not only as a biome, vis‐à‐vis forests, but also for their global importance as a carbon sink and role they play in water management and providing goods to local villagers. We conclude by outlining the necessary research to better manage open ecosystems across Madagascar without threatening endangered forest ecosystems.
Whereas the Coastal Plain of the southeastern United States historically experienced fire primarily during the mid‐summer lightning season, managers today typically apply prescribed fire during the late winter or early spring months. The ecological implications of this discrepancy remain poorly understood, especially with regard to pollinators and their interactions with flowers. In a replicated field experiment, we compared the abundance and richness of bees and bee–flower interactions among pine savanna plots in Florida that were burned either during the winter, spring, summer, or fall. We netted 92 bee species from 77 species of flowers, representing 435 unique bee–flower interactions in total. When analyzing the results from each month separately, we detected significant short‐term reductions in the number of bees and bee–flower interactions following fires regardless of season. Although bee abundance and richness did not differ over the entire season, bee–flower interaction richness was significantly higher overall in spring and summer plots than in fall plots and the composition of both bees and bee–flower interactions differed significantly among treatments. Several bee–flower interactions were significantly associated with one or more of the treatments. Some of these associations could be attributed to differences in flowering phenology among treatments. Taken together, our findings suggest that season of fire has modest but potentially important implications for interactions between bees and flowers in southeastern pine ecosystems. Because most flowering plants within our study region are pollinated by a variety of bees and other insects, and most bees endemic to the region are polylectic, season of fire may not be very important to either group overall. However, the timing of fire may be more important to particular species including certain flower specialists and fire‐sensitive taxa such as butterflies. Future research targeting such species would be of interest.
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Fire can affect ecological communities by direct elimination of organisms or through changes in resource availability, leading to diminished, increased, or unchanged richness. Termite generic richness (= number of genera) as well as termite abundance (= number of records per genus) are shown to not change following fire in a savanna-like ecosystem ('Cerrado') in central Brazil. Since fire is a natural recurrent event (i.e., predictable) in this ecosystem, it seems plausible that termites would have evolved mechanisms to cope with such a disturbance. Such mechanisms would include (i) inhabiting hard, protective, clay nests; (ii) temporary migration into adjacent less affected nearby, satellite, mounds; and (iii) absence of strict dietary specialization, coupled with low levels of competition, allowing niche overlap thereby minimizing adverse effects due to temporary reduction in food availability.
The Cerrado, which includes both forest and savanna habitats, is the second largest South American biome, and among the most threatened on the continent.
We censused butterfly assemblages of the Western Ghats of India in 15 localities and 8 vegetation types during 67 transects, each 600 m long, and traversed in one hour. The natural vegetation types had relatively high diversities compared to human impacted vegetation types such as scrub/savanna and grasslands. The home gardens and paddy fields had very distinctive species composition, coupled with very low levels of beta diversity. Their constituent species were more widespread. Comparison of these patterns with those found amongst trees and birds reported in similar studies threw up interesting parallels as well as contrasts. Species dissimilarity in evergreen vegetation types was high for trees and butterflies, but low for birds. Bird and butterfly assemblages in monoculture tree plantations had low species richness, less distinctiveness and high levels of dissimilarity, being comprised of rather widespread species. However, on the whole there was little relation between taxonomic groups and vegetation types across diversity parameters. There could be important implications of these patterns of diversity dispersion and their co-variation across taxonomic groups for assigning conservation priorities. We emphasize the need for classifying the landscape, both natural and manmade, on the basis of structural vegetation types, followed by stratified sampling of multiple groups of organisms for monitoring the status of and designing conservation strategy for biodiversity.
Fungus-growing ants (tribe Attini) are characteristic elements of the New World fauna. However, there is little information on the patterns of diversity, abundance, and distribution of attine species in their native ecosystems, especially for the so-called "lower" genera of the tribe. A survey of attine ant nests (excluding Atta Fabricus, 1804 and Acromyrmex Mayr, 1865) was conducted in a variety of savanna and forest habitats of the Cerrado biome near Uberlândia, Brazil. In total, 314 nests from 21 species of nine genera were found. Trachymyrmex Forel, 1893 was the most diverse genus with 10 species. Eighteen species were found in the savannas, including Mycetagroicus cerradensis Brandão & Mayhé-Nunes, 2001, a species from a recently-described genus of Attini, whereas in the forests only 12 species were found. Forest and savannas support relatively distinct faunas, each with a number of unique species; the species present in the forest habitats did not represent a nested subset of the species found in the savannas. Furthermore, although many species were common to both types of vegetation, their abundances were quite different. The density of attine nests is relatively high at some sites, exceeding an estimated 4,000 nests per hectare. In this sense, attine ants can be regarded as prevalent invertebrate taxa in the Brazilian Cerrado.
The montane (shola) grasslands of Western Ghats, South India are a component of a landscape mosaic including the better-studied shola forests. The conservation of the grasslands depends upon understanding their ecology. This review compiles available information and aims to evaluate the conservation potential of these grasslands. Most studies on these grasslands are descriptive in nature. There is little information regarding habitat heterogeneity, landscape configuration, natural disturbance, grazing and productivity in maintaining the grasslands. Succession is poorly understood because of the short-term nature of most studies. Human activities have historically influenced these grasslands and will continue to do so in more intensive manner. Threats to these grasslands include habitat loss, fragmentation, fires, and invasive species.
Although it is well known that fire can exert strong control on stand structure, composition, and dynamics in savannas and woodlands, the relationship between fire frequency and stand structure has been characterized in few of the world's savanna and woodland ecosystems. To address this issue in temperate oak-dominated ecosystems, we studied the effects of fire frequency on stand structure and dynamics in oak savanna and woodland stands that had been burned 0-26 times in 32 yr, in the Anoka Sand Plain region of Minnesota (USA). Seedling densities declined with increasing fire frequency, but differentially, for northern pin oak (Quercus ellipsoidalis), black cherry (Prunus serotina), serviceberry (Amelanchier sp.), and red maple (Acer rubrum). Bur oak (Q. macrocarpa) seedling density was not sensitive to fire frequency. Frequent burning (at least three fires per decade) prevented development of a sapling layer and canopy ingrowth. Low-frequency burning (fewer than two fires per decade) produced stands with dense sapling thickets. Reductions in overstory density and basal area from 1984 to 1995 were observed for all stands burned two or more times during that period. Basal area declined by 4-7% per year, and density declined by 6-8% per year in stands burned four or more times. Mortality rates in burned stands were higher for northern pin oak (50%) than for bur oak (8%). Northern pin oak mortality was highest for small trees (
Between 8 and 6 million years ago, there was a global increase in the biomass of plants using C 4 photosynthesis as indicated by changes in the carbon isotope ratios of fossil tooth enamel in Asia, Africa, North America and South America. This abrupt and widespread increase in C 4 biomass may be related to a decrease in atmospheric CO 2 concentrations below a threshold that favoured C 3-photosynthesizing plants. The change occurred earlier at lower latitudes, as the threshold for C 3 photosynthesis is higher at warmer temperatures.
Fire is an important ecological factor in Cerrado vegetation of Central Brazil. The effect of fire on the abundance of large mammalian herbivores was studied at Reserva Xavante do Rio das Mortes, a 32 9000 ha cerrado Reserve in Mato Grosso, Brazil. Track counts were used to compare the abundance of tapir, marsh deer and pampas deer along 7 burned and 7 unburned transects on 7 occasions between August 1995 and August 1996. The number of tracks in burned and unburned areas did not have significant differences. Mammal herbivores use burned areas probably because of renewed food resources. Fire management is recommended at Reserva Xavante do Rio das Mortes.
▪ Abstract Savannas occur where trees and grasses interact to create a biome that is neither grassland nor forest. Woody and gramineous plants interact by many mechanisms, some negative (competition) and some positive (facilitation). The strength and sign of the interaction varies in both time and space, allowing a rich array of possible outcomes but no universal predictive model. Simple models of coexistence of trees and grasses, based on separation in rooting depth, are theoretically and experimentally inadequate. Explanation of the widely observed increase in tree biomass following introduction of commercial ranching into savannas requires inclusion of interactions among browsers, grazers, and fires, and their effects on tree recruitment. Prediction of the consequences of manipulating tree biomass through clearing further requires an understanding of how trees modify light, water, and nutrient environments of grasses. Understanding the nature of coexistence between trees and grass, which under other ci...
The ecology of clonal species has rarely been studied in savannas. Dichrostachys cinerea, a common invasive shrub in southern African savannas, forms root suckers. This paper examines the effect of disturbance type and frequency on this form of clonal spread. Small plants were excavated (n = 370) at 11 sites exposed to different fire frequencies and grazing intensities and classified were as either seedlings or root suckers. Most of the plants (55%) were found to be root suckers. There was no significant effect of disturbance type and frequency on 'seedling' establishment from seeds versus root suckers. Even when burnt annually, D. cinerea continued to form root suckers. The combination of establishment from seeds and spread by root suckers makes this species a formidable native invasive woody shrub.
We investigated bird communities in Mato Grosso do Sul, central Brazil, from July 1994 to December 1996. We sampled birds with mist nets in 14 study sites, including native (cerrado, cerradão and gallery forest) and exotic (Eucalyptus) vegetation. Ninety-nine species from 21 families were represented in 1306 captures, including Antilophia galeata, endemic to cerrado region. Tyrannidae (24 species) and Emberizidae (18 species) were the most well-represented families. Cluster analyses arranged the study sites in four main groups (cerrados and cerradões, cerrados sensu stricto, Eucalyptus plantations, and "forest" habitats). Cerrados shared more species with cerradões than with gallery forests and Eucalyptus plantations. Of 41 species with six or more captures, only two were restricted to one habitat, 13 occurred in two habitats, 17 used three habitats, and 9 were found in all four habitats. Eight species were captured more often in the wet season. Thirty-four species were considered residents. Leaf-insectivores (20.2%) and omnivores (16.2%) were the most abundant guilds; insectivores dominated all four habitats and accounted for 53.5% of all captured species. Birds in Cerrado need a mosaic of habitats, and an opportunity to move among them is a crucial premise for maintaining bird populations.
)ofthe land surface in SouthAmerica,Africa,and Asia.Most people know these savannasbecause oftheir unique assemblages ofabundant and exquisitewildlife;however,they have only recently begun to receive thekind ofattention from a conservation viewpoint that hasbeen given to tropical rain forests (Myers et al.2000).Thelargest,richest,and possibly most threatened tropical sa-vanna in the world is the Cerrado,a large region that occu-pies the center ofSouth America.In an effort to identify theworld’s most important biodiversity hotspots,Myers andcolleagues (2000) ranked the Cerrado among the 25 most im-portant terrestrial hotspots.It is the only region on their listdominated by tropical savannas.The biodiversity ofthe Cer-rado is impressive;in an area of1.86 million km
Community structure, macrohabitat selection, and patterns of species co-occurrence were examined during a 14-month study of small mammals in the Cerrado Province of central Brazil. Data were collected from mark-recapture grids in brejo and gallery forest, and from live-trapping and specimen collection in all habitat types within cerrado (campo limpo, campo sujo, cerrado [s.s.], cerradão, brejo, valley-side wet campo, and gallery forest). Gallery forest supported the highest species richness, most complex vertical distribution of species, highest level of trophic diversity, and highest macroniche diversity. Degree of habitat selection varied widely. All habitat types supported both rodents and marsupials, although marsupials tended to be much less common in the grasslands (campos) than in woodlands (cerrado) and forests (cerradão, gallery forest). Some species, such as Didelphis albiventris, occurred in all habitat types, while others were much more restricted. Oryzomys bicolor, for example, ocur-red only in gallery forest. No habitat type had a completely distinct fauna: overlap in species composition always occurred with at least one other habitat type. Because of the great variability of habitats, and the fact that subsets of the mammal fauna were frequently habitat specific, the overall species richness of any portion of mixed cerrado vegetation is remarkably high.
In mixed tropical landscapes, savanna and rain-forest vegetation often support contrasting biotas, and this is the case for ant communities in tropical Australia. Such a contrast is especially pronounced in monsoonal north-western Australia, where boundaries between rain forest and savanna are often extremely abrupt. However, in the humid tropics of north-eastern Queensland there is often an extended gradient between rain forest and savanna through eucalypt-dominated tall open forest. It is not known if ant community structure varies continuously along this gradient, or, if there is a major disjunction, where it occurs. We address this issue by sampling ants at ten sites distributed along a 6-km environmental gradient from rain forest to savanna, encompassing the crest and slopes of Mt. Lewis in North Queensland. Sampling was conducted using ground and baited arboreal pitfall traps, and yielded a total of 95 ant species. Mean trap species richness was identical in rain forest and rain-forest regrowth, somewhat higher in tall open forest, and twice as high again in savanna woodland. The great majority (78%) of the 58 species from savanna woodland were recorded only in this habitat type. MDS ordination of sites based on ant species composition showed a continuum from rain forest through rain-forest regrowth to tall open forest, and then a discontinuity between these habitat types and savanna woodland. These findings indicate that the contrast between rain forest and savanna ant communities in tropical Australia is an extreme manifestation of a broader forest-savanna disjunction.
Soybeans represent a recent and powerful threat to tropical biodiversity in Brazil. Developing effective strategies to contain and minimize the environmental impact of soybean cultivation requires understanding of both the forces that drive the soybean advance and the many ways that soybeans and their associated infrastructure catalyse destructive processes. The present paper presents an up-to-date review of the advance of soybeans in Brazil, its environmental and social costs and implications for development policy. Soybeans are driven by global market forces, making them different from many of the land-use changes that have dominated the scene in Brazil so far, particularly in Amazonia. Soybeans are much more damaging than other crops because they justify massive transportation infrastructure projects that unleash a chain of events leading to destruction of natural habitats over wide areas in addition to what is directly cultivated for soybeans. The capacity of global markets to absorb additional production represents the most likely limit to the spread of soybeans, although Brazil may someday come to see the need for discouraging rather than subsidizing this crop because many of its effects are unfavourable to national interests, including severe concentration of land tenure and income, expulsion of population to Amazonian frontier, and gold-mining, as well as urban areas, and the opportunity cost of substantial drains on government resources. The multiple impacts of soybean expansion on biodiversity and other development considerations have several implications for policy: (1) protected areas need to be created in advance of soybean frontiers, (2) elimination of the many subsidies that speed soybean expansion beyond what would occur otherwise from market forces is to be encouraged, (3) studies to assess the costs of social and environmental impacts associated with soybean expansion are urgently required, and (4) the environmental-impact regulatory system requires strengthening, including mechanisms for commitments not to implant specific infrastructure projects that are judged to have excessive impacts.
Fire is a key ecological process in several biomes worldwide. Although many conservation agencies have the protection of biodiversity as at least one of their major goals, information on the effects of fire on fauna in these biomes is fragmentary. Here we provide an overview of the published research undertaken to date on the effects of fire on fauna using examples from Southern Africa. We found that few studies have examined the effects of fire on amphibians or reptiles, and work on invertebrates is likewise sparse. The majority of studies that have been published are observational reports, and few experimental studies have been undertaken using an experimental fire regime, or over appropriately long time intervals. Replication was often not reported and where this was done, it was generally inadequate. The majority of the studies failed to report the area over which the studies were undertaken and sampling unit size was often not reported. Despite the importance of fire duration, ignition method, season and time of day of fire, few studies investigated these variables. We conclude that at present the information on the effects of fire on fauna in Southern Africa is fragmentary and, consequently, informed management decisions regarding the consequences of burning policies on the conservation of biodiversity both within and outside protected areas are problematic. We recommend that future studies, both in Southern Africa and elsewhere, be based on a suite of large-scale and experimental approaches (the latter firmly grounded in the principles of sound experimental design), use non-classical statistics to explore the effects of large-scale or unreplicated fires, and where possible include baseline information such as that gathered in fragmentation experiments.
The Cerrado biome of central Brazil comprises one of the most biologically diverse savannas in the world. Modern agricultural practices have led to a large-scale conversion of the region for high-yield grain production. This paper presents a preliminary analysis of among-site variation in bird species richness and turnover. Species lists for six sites ranged from 202 to 263 species per site, with the Jaccard similarity index varying from 0.326 to 0.611. All six site lists added up to 519 species, more than 50 percent of which occurred at only one or two sites. Most among-site turnover was associated with forest and aquatic faunas. Savanna and other open habitats also had substantial turnover, however, with similarity indices in the range of 0.434 to 0.734. Eighteen endemic species were recorded; those at risk were associated primarily with open grasslands. The high avian diversity and substantial human impact in this region indicate that the Cerrado should be a major priority for conservation action.
The Amazon Forest and the Cerrado of central Brazil share an extensive zone of integration. Each of these major ecosystems remains poorly studied; however, the composition of communities at the: contact zone is even less well described. Small mammals were sampled during a ten-week period in a zone of contact between Amazonian forest and Cerrado. The vegetation in the area was a complex mixture of tropical and semi-deciduous forest, and grassland and savanna woodland formations. Mammals were marked and recaptured on 0.25- to 0.5-km transects and vouchers were collected. A total of 19 species was caught (13 rodents and 6 marsupials) in 4621 crap nights. Transitions from one vegetation type to another were abrupt with ecotones frequently ( 5 m in width. The highest alpha -diversity was 7 species in cerrado. Ten of the 19 species were restricted to one habitat and 6 were restricted to two habitats. Three generalist grassland species occurred in more than Mo habitats, all variations of savanna. These data support other research indicating high habitat specificity of vertebrates and plants in the Brazilian savannas. The diversity of habitats within reserves in tropical grasslands must be given consideration in the design of protected areas in order to maximize the conservation of mammalian biodiversity.
Grass species of the conservation areas of the Natal Drakensberg are divided into two ecological groups. Decreaser species are those which decrease with over- or under-utilization, while increaser I species are those which increase with under-utilization. The effect of intensity and height of shading on decreaser species (Themeda triandra, Heteropogon contortus and Trachypogon spicatus) and increaser species (Tristachya leucothrix, Harpochloa falx and Alloteropsis semialata) was determined in potted plant trials. Results of this study support the hypothesis that decreaser species were more sensitive to low light intensities (30% full sunlight) than increaser species. These two species groups did not, however, differ in their response to height of shading. The results suggest that different fire regimes resulting in changes in canopy cover and light quality are important mechanisms in regulating tiller initiation in perennial grasses.
A yearly global fire history is a prerequisite for quantifying the contribution of previous fires to the past and present global carbon budget. Vegetation fires can have both direct (combustion) and long-term indirect effects on the carbon cycle. Every fire influences the ecosystem carbon budget for many years, as a consequence of internal reorganization, decomposition of dead biomass, and regrowth. We used a two-step process to estimate these effects. First we synthesized the available data available for the 1980s or 1990s to produce a global fire map. For regions with no data, we developed estimates based on vegetation type and history. Second, we then worked backwards to reconstruct the fire history. This reconstruction was based on published data when available. Where it was not, we extrapolated from land use practices, qualitative reports and local studies, such as tree ring analysis. The resulting product is intended as a first approximation for questions about consequences of historical changes in fire for the global carbon budget. We estimate that an average of 608 Mha yr(-1) burned (not including agricultural fires) at the end of the 20th century. 86% of this occurred in tropical savannas. Fires in forests with higher carbon stocks consumed 70.7 Mha yr(-1) at the beginning of the century, mostly in the boreal and temperate forests of the Northern Hemisphere. This decreased to 15.2 Mha yr(-1) in the 1960s as a consequence of fire suppression policies and the development of efficient fire fighting equipment. Since then, fires in temperate and boreal forests have decreased to 11.2 Mha yr(-1). At the same time, burned areas increased exponentially in tropical forests, reaching 54 Mha yr(-1) in the 1990s, reflecting the use of fire in deforestation for expansion of agriculture. There is some evidence for an increase in area burned in temperate and boreal forests in the closing years of the 20th century.
In the broad sense, the cerrado may be considered part of a large ecocline, occurring in Brazil under a single, tropical, seasonal climate (climate zone II of Walter 1970) and determined primarily by gradients of soil fertility and the incidence of fire. In fact, the cerrado represents the final portion of the transition from eutrophic tropical seasonal forest to a pedo- and peinobiome of tropical moist savanna and grassland (Fig. 1).
Although it is well known that fire can exert strong control on stand structure, composition, and dynamics in savannas and woodlands, the relationship between fire frequency and stand structure has been characterized in few of the world's savanna and woodland ecosystems. To address this issue in temperate oak-dominated ecosystems, we studied the effects of fire frequency on stand structure and dynamics in oak savanna and woodland stands that had been burned 0-26 times in 32 yr, in the Anoka Sand Plain region of Minnesota (USA). Seedling densities declined with increasing fire frequency, but differentially, for northern pin oak (Quercus ellipsoidalis), black cherry (Prunus serotina), serviceberry (Amelanchier sp.), and red maple (Acer rubrum). Bur oak (Q. macrocarpa) seedling density was not sensitive to fire frequency. Frequent burning (at least three fires per decade) prevented development of a sapling layer and canopy ingrowth. Low-frequency burning (fewer than two fires per decade) produced stands with dense sapling thickets. Reductions in overstory density and basal area from 1984 to 1995 were observed for all stands burned two or more times during that period. Basal area declined by 4-7% per year, and density declined by 6-8% per year in stands burned four or more times. Mortality rates in burned stands were higher for northern pin oak (50%) than for bur oak (8%). Northern pin oak mortality was highest for small trees (< 20 cm dbh) and lowest for mature trees (30-40 cm dbh); mortality increased with fire frequency. Bur oak mortality declined with increasing fire frequency. Attempts to preserve and maintain savannas as a viable ecosystem type in this region will require a long-term commitment to restoration-based management, with prescribed fire as a central tool. Burn frequency treatments with four or more fires per decade produce similar reductions in stem density and stand basal area but may lead to unsustainable oak tree populations. Within this general range, fire frequencies at a decadal scale should be chosen to address other management objectives, including suppressing shrubs and promoting increased cover of grasses and other herbaceous species. Fire management with a long-term view may also require periodic respites to allow for new cohorts of mature oak trees.
In tropical West Africa, distribution patterns of forest islands in savannas are influenced by fires which occur regularly in the grass stratum. Along continuous forest-savanna transects in the Comoe National Park, the change in the amount and composition of non-woody phytomass was investigated from savanna to forest interior. This was correlated with the cover of vegetation strata above, soil depth, and the occurrence of seasonal surface fires. Phytomass mainly consisted of leaf litter in the forests (about 400 g m(-2) at the end of the rainy season, and about 600 g m(-2) at the end of the dry season) and of grasses in the savanna (about 900 g m(-2)). Low grass biomass appeared to be primarily the result of suppression by competing woody species and not of shallow soil. The occurrence of early dry-season fires seemed to be determined mainly by the amount of grass biomass as fuel because fires occurred in almost all savanna plots while forest sites remained unaffected. However, late dry-season fires will encounter higher amounts of leaf litter raising fire probability in forests. Due to the importance of the amount of combustible phytomass, fire probability and intensity might increase with annual precipitation in both savanna and forest.
The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of
this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied.
Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional
clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity.
Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest
into scrub or savanna.