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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.
... Savannas and grasslands are ancient ecosystems (originating 8-10 Mya) that support unique biodiversity (Bond & Parr, 2010;Murphy et al., 2016;Ratnam et al., 2011;Veldman et al., 2015a). The misconception that they are 'derived' from forests through deforestation and other land-use processes and are therefore somewhat "degraded" has resulted in mismanagement of their biodiversity, and conversion to other land uses such as agriculture and tree plantations (Bond & Parr, 2010;Murphy et al., 2016;Parr et al., 2014;Ratnam et al., 2016;Veldman et al., 2015a). ...
... Savannas and grasslands are ancient ecosystems (originating 8-10 Mya) that support unique biodiversity (Bond & Parr, 2010;Murphy et al., 2016;Ratnam et al., 2011;Veldman et al., 2015a). The misconception that they are 'derived' from forests through deforestation and other land-use processes and are therefore somewhat "degraded" has resulted in mismanagement of their biodiversity, and conversion to other land uses such as agriculture and tree plantations (Bond & Parr, 2010;Murphy et al., 2016;Parr et al., 2014;Ratnam et al., 2016;Veldman et al., 2015a). It is estimated that ~ 6.7 million km 2 of savanna, grassland and steppe habitats were converted to croplands between 1700 and 1992 (Ramankutty & Foley, 1999), with >80% of grassland and savanna habitats being converted to anthropogenic land uses by 2000 (Ellis et al., 2010;Ellis & Ramankutty, 2008). ...
... Species richness in tropical savannas and grasslands can be quite high, and in some cases comparable to forests , with the Neotropics and Afrotropics especially diverse . In forests much of the diversity resides in the tree layer, but grasses and forbs contribute substantially to plant species richness in tropical savannas and grasslands (Bond & Parr, 2010;Murphy et al., 2016;Ratnam et al., 2016;Sankaran, 2009). ...
... Recent rates of tropical savannah loss are among the highest of all ecosystem types (Hoekstra et al., 2005;Williams et al., 2020b), and their overall protection is disproportionately low . This is concerning as they are important components of global biodiversity (Baillie et al., 2004), and for people through the many ecosystem services they provide (Bond and Parr, 2010;Grace et al., 2006;Greiner et al., 2009;Kundhlande et al., 2000;Millennium Ecosystem Assessment, 2005b;Russell-Smith and Sangha, 2018). Rapid and severe biodiversity declines are being reported in tropical savannahs from every continent (Etter et al., 2017;Mustin et al., 2017;Mwangi and Ostrom, 2009;Vargas et al., 2015;Woinarski et al., 2011), yet there appears to be a large research bias towards understanding how biodiversity is being affected in other ecosystems (such as tropical forest), even though tropical savannahs are being impacted just as much, if not more, by a range of drivers and support outstanding values of biodiversity and ecosystem services ( Fig. 1) (Murphy et al., 2016). ...
... Tropical savannahs were once thought to be a form of degraded forests by many scientists (Pausas and Bond, 2019;Ratnam et al., 2011), but are now recognised as unique ecosystems (but see (Kumar et al., 2019)). They are comprised of a continuous layer of C4 grasses (C4 grasses refers to species that have additional steps in the photosynthetic cycle that make the photosynthetic pathways to capture carbon dioxide more suited to warmer conditions) inter-mixed with often thick-barked trees with an open canopy that is typically burnt frequently (Bond and Parr, 2010;Ratnam et al., 2011). They are broadly located in the tropics, found mainly in Africa, Australia and South America, and cover onesixth of Earth's land surface according to our definition (Fig. 2). ...
... Climate change can also affect the savannah environment via other biophysical pathways. While the growth of savannah grass types is stimulated by higher temperatures, higher concentrations of CO 2 favour woody vegetation (Bond and Parr, 2010), which may affect vegetation composition. Increasing fire frequencies may favour grasses over wooded vegetation; however, it is still unclear how these forces will change the boundaries of forest and savannah ecosystems across different regions (Staver et al., 2011). ...
All tropical savannahs are experiencing extensive transformation and degradation, yet conservation strategies do not adequately address threats to savannahs. Here, using a recently published ecosystem intactness metric, we assess the current condition of tropical savannahs across Earth, finding that <3 % remain highly intact. Moreover, their overall levels of protection are low, and of the protected savannahs, just 4 % can be considered highly intact while the majority (>60 %) are in poor condition. In order to address the clear mismatch between the decline in tropical savannah ecosystems’ condition and the response to manage and conserve them, we reviewed the current drivers that lead to tropical savannah degradation and identified conservation approaches being used to address them. Many successful conservation approaches address multiple drivers of change but are applied across small areas. We argue these approaches have the potential to be up-scaled through integrated land-use planning.
... Savannahs are defined by a continuous layer of C4 grasses and may have tree cover varying from 0-80% (Ratnam et al. 2011, Sankaran et al. 2005. They cover around 20% of the Earth's terrestrial surface and are a particularly prominent biome in tropical regions (Bond and Parr, 2010). Savannahs are home to assemblages of unique species and are also of significant economic and cultural value to human populations (Bond & Parr, 2010;Grace et al. 2006;Scholes & Archer, 1997). ...
... They cover around 20% of the Earth's terrestrial surface and are a particularly prominent biome in tropical regions (Bond and Parr, 2010). Savannahs are home to assemblages of unique species and are also of significant economic and cultural value to human populations (Bond & Parr, 2010;Grace et al. 2006;Scholes & Archer, 1997). ...
... In turn, herbivores can remove vegetation that would otherwise burn and thereby modify or prevent fire spread across the landscape . These interactions can create alternate stable states, with long grass areas which burn frequently but have low herbivory, and short grass areas which are attractive to herbivores but too short to burn (Archibald, 2008;Bond & Parr, 2010;. ...
Savannahs are consumer controlled systems where fire and herbivory maintain plant biomass below the level that is predicted by rainfall and temperature. Savannahs are globally important biomes, covering around 20% of our planet’s terrestrial surface and providing economic and cultural value, carbon sequestration, ecosystem services, and habitat for many unique species. Whilst both fire and herbivory consume plant biomass they vary in their mechanism, timing, geographic extent, frequency, and selectivity. Studying fire, herbivory and their effects can be challenging because both are multifaceted phenomena. They also interact and capable of both facilitating and inhibiting one another. However, understanding the patterns in fire and herbivory and the differences in how flora and fauna respond is vital to the successful management of savannah systems. Here we use both satellite data and field experiments to quantify the fire regime of the Serengeti-Mara ecosystem of southern Kenya and northern Tanzania and compare the effects of fire and herbivory on the ecology of the system. We describe the spatiotemporal patterns in the components of the Serengeti-Mara’s fire regime and show that rainfall is the primary driver of the variability we observe. We also observe a striking decline in the area burnt and the number of fires and attribute this to increasing livestock density. We use the high intensity and short duration of grazing by the wildebeest migration as an analogue to fire and compare the effects of the two disturbances on vegetation, resident mammalian herbivores, and invertebrates. We show that there are similar effects on grass structure but only fire increased grass quality and there were contrasting effects on forb communities. These differences in vegetation cascade to affect the distribution of resident mammalian herbivores. Long grass areas attracted bulk grazers such as zebra and buffalo whilst short grass areas were attractive to selective grazers such as wildebeest and Thompson’s gazelle. Not all of the species that were more abundant in short grass areas were attracted to high quality grazing, indicating that some species may select short grass areas for anti-predator rather than resource benefits. Finally, we show that fire and herbivory have contrasting direct and indirect effects on invertebrates, with responses varying based on taxa and ecological niche. Our results have important implications for the management of the Serengeti-Mara and our understanding of savannahs.
... Livestock production also centers in areas that were once (and sometimes still are) native grasslands. Grassy biomes harbor distinct and diverse sets of plants and animals that have adapted to these environments through millions of years of evolution (2). As the biodiversity and economic prominence of grassy biomes are increasingly being recognized, there is a demand for better understanding of their past and present function to inform policy and management. ...
... Grassy biomes thus emerged during the Cenozoic at different times in different places and, at least in part, for different reasons. Studies in modern grassy biomes suggest that aridity and rainfall seasonality, as well as fire and herbivory, could all favor grasses over trees (2), with even larger benefits at lower atmospheric CO 2 concentrations. The fossil record shows that many of these conditions did occur in the late Cenozoic. ...
... These moderately wet, or "mesic" grassy ecosystems are biogeographically distinct from semiarid ones, but both are evolutionarily ancient (1). Yet, whereas 5 As their antiquity is increasingly recognized, the ecological processes that promote mesic savanna stability have come into increasing focus (2). Fire likely plays an important role in stabilizing mesic savannas, excluding forests by preventing tree establishment or killing trees, thereby fa voring grasses. ...
Grassy biomes are >20 million years old but are undervalued and under threat today.
... Most plant diversity in grassy ecosystems is in herbaceous plants (vascular plants with non-woody stems) (Perez-Garcia & Meave, 2006), with forb diversity (flowering plants of self-supporting growth form, excluding graminoids) especially high, followed by graminoids-grasses, rushes, and sedges (Bond & Parr, 2010). ...
... Further, Murphy et al. (2016) found that there can be a higher diversity of mammalian megafauna in tropical grassy ecosystems than in forests of similar climate. Similarly, invertebrates may be of higher diversity in tropical grasslands than forests (Bond & Parr, 2010). Grassy biomes were formed by complex evolutionary and ecological interactions among plants and disturbance resulting in unique assemblages (Veldman et al., 2015) representing complex food webs and habitats (Anderson et al., 2016). ...
... The concept of grassy ecosystem as a successional stage preceding a forest climax is misleading, and the two are better viewed as alternate states maintained by disturbance-centred feedbacks (Bond & Parr, 2010), where across much of their range, forest and grassy biomes are bistable (Staver et al., 2011). The contrasting processes of disturbance and shade lead to divergent assemblages in grassy and forest ecosystems with few species common even in locally adjacent areas (Bond, 2016;Hoffmann et al., 2009), suggesting the integrity of grassy ecosystem plant diversity and ecosystem function is dependent on canopy openness (Bond, 2016;Lehmann & Parr, 2016). ...
Woody encroachment is ubiquitous in grassy ecosystems worldwide, but its global impacts on the diversity of herbaceous plants that characterise and define these ecosystems remain unquantified. The pervasiveness of encroachment is relatively easily observed via remote sensing, but its impacts on plant diversity and richness below the canopy can only be observed via field-based studies. Via a meta-analysis of 42 field studies across tropical to temperate grassy ecosystems, we quantified how encroachment altered herbaceous species richness, and the richness of forbs, C3 graminoids and C4 graminoids. Across studies, the natural logarithm of the response ratio (lnRR) of herbaceous species richness ranged from -3.33 to 0.34 with 87% of encroached ecosystems negatively impacted. Assessment of the extent of encroachment, duration of encroachment, mean annual rainfall, latitude, and continent demonstrated that only extent of encroachment had relevance in the data (univariate model including a random effect of study explained 45.4% of variance). The global weighted mean lnRR of species richness decreased from -0.245 at <33% of woody cover increase, to -0.562 at 33%-66%, and to -0.962 at >66%. Continued encroachment results in substantial loss of herbaceous diversity at medium and high extents, with a loss of richness that is not replaced. Although all functional groups are significantly negatively impacted by encroachment, forb richness is relatively more sensitive than graminoid richness, and C4 graminoid richness relatively more than C3 graminoid richness. Although no geographic or climatic correlates had relevance in the data, encroachment as an emergent product of global change coalesces to decrease ground layer light availability, lead to loss of fire and grazers, and alter hydrology and soils. Encroachment is accelerating and grassy ecosystems require urgent attention to determine critical woody cover thresholds that facilitate diverse and resilient grassy ecosystems.
... Savanna ecosystems cover approximately 40% of Africa , and are characterised by the co-existence of a woody layer, dominated by trees and shrubs of 2 -15 m occurring at variable density, and an herbaceous layer dominated by C4 grasses (Knoop and Walker, 1985;Scholes and Archer, 1997). The structure, function and dynamics of savannas are largely influenced by fire Bond and Parr, 2010;. Consequently, fire affects nutrient cycling, grass productivity and tree recruitment to enable the coexistence of woody and herbaceous plants in savanna systems (Anderson et al., 2007;. ...
... Fire is able to modify the structure, function and dynamics of savanna-woodland ecosystems Bond & Parr, 2010;, and is therefore managed in protected areas to achieve conservation goals by promoting preferred elements of fire regimes (i.e. fire size, intensity, season and frequency) . ...
... In addition, fire frequency is able to modify the structure, function and dynamics of savanna-woodland ecosystems Bond & Parr, 2010; by, for example, increasing woody cover , promoting the regeneration of trees (Bond & Midgley, 2001;Prior et al., 2006), or ensuring the survival of tall trees . Therefore, the effect of fire frequency on vegetation composition and woody plant structure was assessed (Chapter 7) to further guide and refine fire management approaches and policies in MWR. ...
Fire is an important process that shapes the structure and functioning of African savanna ecosystems, and frequently occurs as either prescribed burns or unintentional wildfires in protected areas. Though the level of understanding of the ecological effects of fires has grown substantially over the past century, comprehensive information on the practical application of fire is still restricted, and management information is scattered. Similarly, an improved understanding of how fire affects African mammals is important for the management of both fire regimes and mammal populations. This is also the case in Majete Wildlife Reserve (MWR), Malawi, where a lack of understanding of the past occurrence, determinants, features and effects of prevailing fire regimes prevents the development of appropriate fire management policies. Two separate reviews were conducted to describe the approaches to, and goals of, fire management in African savanna protected areas, as well as the response of large (>5 kg) mammals to fire. For MWR, combinations of remote-sensing and on-the-ground surveys were used to develop a spatially-explicit dataset of the recent fire regime (2001-2019), and to classify, describe and map the woody plant communities present. Additionally, the effect of long-term fire frequencies on vegetation composition, woody plant structure, and large mammal assemblages were assessed, as well as the immediate post-fire habitat selection of large herbivores in a comparative burnt and unburnt landscape. For protected areas, fifteen distinct fire management practices, used to achieve 10 broad ecological (e.g. reversing woody encroachment) and non- ecological (e.g. protecting infrastructure) goals, were identified. Additionally, the responses of 51 mammal species to fire were identified, showing that body size was strongly correlated with fire response, with smaller grazers more likely to respond positively to fire than larger browsers. In MWR, it was found that frequent fires dominate the landscape, with ~57% of MWR burning at intervals of two years or less, and an additional ~30% burning at intervals of 3-5 years. A current mismatch between intended fire management goals and actual trends was also highlighted. Five distinct woody plant communities, two of which were subdivided into three sub-communities each, were recognised, along with 118 woody species identified. Fire frequency had little effect on woody plant community composition, but did affect grass species composition. Mammal species clearly selected for either frequently-burnt or infrequently-burnt areas. Clear selection for either burnt (e.g. impala and warthog) or unburnt (e.g. elephant and bushbuck) habitats, that were unrelated to the availability of above-ground herbaceous biomass, were also shown post-fire. This information is intended to provide a basis for improved fire management planning and policy development, as well as providing a baseline against which to monitor change. Managers should re-evaluate fire policies based on these findings, setting clearly defined targets for the different vegetation types, and introducing flexibility in fire regimes to accommodate natural variation. Establishing a mosaic of patches exposed to different fire frequencies, intensities, seasons and sizes will likely be needed to create a range of habitat types that would best allow for the persistence of all facets of biodiversity in MWR.
... Forbs are an important component of grassland ecosystems. Within temperate grasslands, they are a major contributor to biodiversity, and make up, by far, the highest proportion of plant species richness (Averett & Endress, 2022a;Bond & Parr, 2010). Forbs strongly influence a range of ecosystem functions (Gould et al., 2016;Tilman et al., 2001), contribute to the structural complexity of grasslands, and provide habitat and food resources (e.g., roots, leaves, nectar, fruit) for numerous invertebrate and vertebrate species (Andersen et al., 2019;Fortin et al., 2013;Haddad et al., 2009;Potts et al., 2009). ...
... Recognition that forbs are a major component of grassland species richness is widespread (Bond & Parr, 2010;Daubenmire, 1942). Yet, our research revealed that data from vegetation surveys conducted during the summer only capture a portion of perennial forbs, resulting in biased and inaccurate characterization of PNB plant assemblages. ...
Abstract Forbs are a culturally and ecologically important yet poorly studied component of the Pacific Northwest Bunchgrass (PNB) ecosystem of western North America. Because many PNB forbs emerge early in the spring and senesce at the onset of summer, typical vegetation surveys, which occur mid‐summer, likely underrepresent forbs. We evaluated how the timing of vegetation sampling affected estimates of perennial forb abundance, richness, and floral density, with a focus on species that are culturally significant to Indigenous people of the region. We sampled 29 plots three times: mid‐summer (July), as well as 7 (May) and 12 (April) weeks prior. Timing had large effects on estimates, with significant declines in forb richness (42%), cover (80%), and floral density (95%) between April and July. The density of Camassia quamash and Lomatium cous, two culturally important species, declined 91% and 96%, respectively, from April to July. Nearly 65% of forbs had documented uses by Plateau Tribes. The consequences of biased estimates are significant and (1) limit our understanding of fundamental ecological processes and interactions; (2) hinder effective conservation and management because we lack information on forb abundance, status, and trends, and (3) result in disproportionately negative impacts to Indigenous communities as many forbs are important for subsistence and ceremonial purposes. Vegetation sampling during the spring months coincident with peak forb abundance, in addition to summer sampling would provide more appropriate data with which to evaluate and characterize PNB vegetation dynamics and improve our understanding, management, and conservation of native forbs.
... The largest group were Hemicryptophytes, which are characterized by a remnant shoot system with leaves that lie relatively flat on the ground. This group is globally the largest of the five major plant life-forms, and therefore this high endemism among Hemicryptophytes in the LMEE was predictable, as the group is well-adapted to open grassy ecosystems (Bond and Parr, 2010). Cryptophytes made up the second largest group of endemics-specifically geophytes that exhibit periodic reduction of the complete shoot system to storage organs that are imbedded in the soil and exhibit fire-stimulated flowering (Lamont and Downes, 2011). ...
... Significantly, the exceptional endemism in the LMEE is driven by speciation in Grassland, most likely driven in response to herbivory, climate, and fire (Bond and Parr, 2010). This is significant-not because the value of Grassland for biodiversity is new knowledge in southern Africa-but because the finescale determination of endemism in an orographic context reveals (in the LMEE) to which extent this is true for southern African (montane) Grassland. ...
Climatic, edaphic, and topographic differences between mountains and surrounding lowlands result in mountains acting as terrestrial islands with high levels of endemic biota. Conservation of mountains is thus key to successful biodiversity conservation. The Limpopo–Mpumalanga–Eswatini Escarpment (LMEE) in South Africa and the Kingdom of Eswatini is one of the largest components of southern Africa’s Great Escarpment. Despite botanical collecting effort over 150 years, there has never been a holistic and comprehensive synthesis of plant endemics data for the LMEE. For the first time, we define the LMEE as an orographic entity, covering 53,594 km2; it forms a contiguous highland area from the Pongola River in the south, north to the Woodbush area, and includes rugged western Eswatini. Using exhaustive literature mining, coupled with combined decades of fieldwork by the authors, and up-to-date taxonomic assessments of the 46 undescribed species, we provide the first robust list of plant endemics for the LMEE. The LMEE has 496 endemic plant taxa, comprising 10.7% of the provisional flora (4,657 taxa). This is more than double the endemic plant taxa in the Drakensberg Mountain Centre (DCM), and may be the richest concentration of montane endemics in southern Africa outside of the Core Greater Cape Floristic Region. Grassland hosts the largest number of endemics (74.2%), followed by Savanna (26.6%), then Forest (7.7%). Most endemics of conservation concern occur in Grassland (68.4%), in which one is Extinct and two are Extinct in the Wild. Evolutionary partitioning between Grassland, Savanna and Forest is suggested by low introgression of Biomes at family and genus level, and by a dominance of life-forms adapted to open habitats. High threat statuses for Grassland endemics can be attributed to the historical transformation of almost 20% of Grassland to forestry pre-1990, and ongoing degradation of primary Grassland. With conservation area coverage only 11.1% of the LMEE, the exceptional richness of the endemic flora—combined with major conservation threats—suggest that the LMEE should become a major focus of conservation effort between South Africa and Eswatini as a matter of urgency.
... These ecosystems provide excellent habitats to the extant mammalian megafauna and support billions of people whose livelihood directly depend on these (Parr et al., 2014); besides, storing 15% of the carbon on land and contributing approximately 30% of the net primary productivity globally (Grace et al., 2006). Despite the critical role that these grasslands play, these ecosystems are poorly conserved (Bond and Parr, 2010). Historically, the conservation value of the grasslands is underappreciated; however, in recent times the importance of grasslands as biodiversity hotspots are recognized (Bond and Parr, 2010;Murphy et al., 2016). ...
... Despite the critical role that these grasslands play, these ecosystems are poorly conserved (Bond and Parr, 2010). Historically, the conservation value of the grasslands is underappreciated; however, in recent times the importance of grasslands as biodiversity hotspots are recognized (Bond and Parr, 2010;Murphy et al., 2016). ...
Research on control efficacy of Chromolaena odorata is rare worldwide. Given the species' impact on internationally recognized protected areas, such research is important. Management method to control invasion and promote grassland recovery is poorly studied, particularly of C. odorata. In the present study, we test the efficacies of different management methods- manual uprooting, cutting, and cutting and burning of C. odorata plants to restore native grassland habitat in the sub-Himalayan grassland ecosystem in Manas National Park. We conducted experiments in three 1-ha plots, each plot was subjected to different treatments, where we monitored the recovery of native grass species. Based on our experiment we found that the species richness, density and cover of native grasses increased significantly by the third year (t2) in the manually uprooted treatment site compared to other two treatments; while the density and cover of C. odorata decreased. Our data highlight the efficacy of the manual uprooting treatment in reviving the grassland habitat. It is an ecologically-effective strategy as it can restore the entire native grass-community if maintained and monitored for at least three to five years. However, we caution that manually uprooting the C. odorata and reviving natural grass-communities requires long-term investment of resources and time. With this tried and tested management methodwe have reduced invasion by approximately 95% in the selected prime grassland habitat of around 5 km² area in the central and eastern ranges of the Park in subsequent years. We have encouraged the use of C. odorata as natural dyeing agent among the local communities, as a complementary control action. The findings of the study will aid the forest managers to devise a comprehensive and pragmatic invasive species management plan in order to ensure long-term conservation of grassland habitat and its dependent species.
... The transition from a pristine to a promoted landscape [24] began with the arrival of the first humans in the region (Figure 7b). Anthropogenic fires were frequent starting from the early Holocene [108,109], which, added to wildlife grazing, caused changes in the physiognomy and composition of the vegetation, favouring grasses and herbs in the grasslands [110][111][112]. Hunting and gathering activities were favoured [113], and greater security was obtained in inhabited environments, among other benefits. ...
The Butia odorata palm grove in southeast Uruguay forms a particular landscape of the Pampa biome, which has been inhabited and transformed since the early Holocene. The forms and meanings of this contemporary landscape are the result of the historical interaction between culture and nature. The conservation of its natural and cultural heritage has been compromised by anthropic activities, leading to conservation proposals from different disciplinary perspectives that are partial and do not consider the landscape’s integrity. In this article, we propose a comprehensive approach, integrating the ecological, cultural and socioeconomic aspects through a historical look at the domestication process of this landscape. This approach is based on a transdisciplinary narrative aimed at generating a multidimensional and diachronic characterisation of the palm grove landscape on which to base a participatory definition of the most appropriate instrument for conservation through sustainable use.
... While in New Jersey (NJ) A. americanum is also associated with forests and woodlands, this species as well as D. variabilis can thrive in open habitats, such as meadows and ecotones [10]. These areas have higher temperatures and lower relative humidity than forests due to the lack of trees and leaf litter that buffer extreme temperature and moisture conditions in forested areas [14]. ...
People often use parks and other forested areas for outdoor activities such as hiking and walking their dogs. Areas of primary use are paths or grassy meadows on the edges of the forests that constitute transitional areas between different plant communities (aka ecotones). In this study, we monitored the seasonal dynamics of questing ticks in forest/meadow and forest/path ecotones in five areas in Middlesex County, New Jersey (NJ). We found anthropophilic species such as Ixodes scapularis, Amblyomma americanum, and Dermacentor variabilis coexisting with Haemaphysalis longicornis, an invasive tick species first detected in NJ in 2017. Surveillance was conducted weekly from March to November 2020, and collected ticks were identified. The most abundant tick species was H. longicornis (83%), followed by A. americanum (9%), I. scapularis (7%), and D. variabilis (<1%). The seasonal dynamics of A. americanum and I. scapularis in the ecotone were similar to previous surveys in forest habitats. The presence of anthropophilic ticks, particularly I. scapularis, suggests the need for specific control approaches to target these habitats. In addition, the extraordinarily high numbers of H. longicornis collected in ecotones (1.70 ticks/m2) and frequent reports of this species on dogs highlight the importance of monitoring its expansion due to its potential as a vector of animal and human diseases.
... Many of these grassland habitats in the Western Ghats are of primary origin and not a result of anthropogenic activities (Vasanthy, 1988;Sukumar et al., 1993). Unlike other forest ecosystems these grasslands are poorly conserved as they are thought to be the effects of forest clearance (Bond and Parr, 2010). Open areas of the Western Ghats in Maharashtra have limited soil cover that can only support grasslands under biotic pressures. ...
In the current era of modernisation and globalisation, the emerging economies like India are scaling up their growth and development at a rapid rate. This economic developmental phase has however side lined the biodiversity conservation priorities in a country like India where globally recognised biodiversity hotspots such as the Western Ghats harbour a variety of endemic, endangered and threatened floral and faunal species. A large segment of the landscape in the unprotected land in the Western Ghats faces a growing challenge for conserving biodiversity. The formally recognised protected areas are being conserved through various rules and regulations. The main concern today is conserving the various types of small and large biodiversity rich 'hotspecks' that are outside the protected area boundaries that are refugia for biodiversity and are being used as jump sites for movement by various faunal species. These hotspecks are present in a matrix of both natural and cultural landscapes.
... Tropical savannas and grasslands are present mainly in the southern hemisphere, covering approximately 20% of land on Earth (Huntley and Walker 1982), providing homes for millions of people and important ecosystem services at the global scale (Parr et al. 2014), but are also underrepresented in ecology scientific literature . The biodiversity of tropical savannas is high in the number of species and their uniqueness (Murphy et al. 2016), and because of the threats to their conservation (Parr et al. 2014), these ecosystems are recognized as globally endangered (Bond and Parr 2010) . Biological invasion is one of the main threats these ecosystems face (Milton 2004;Foxcroft et al. 2010). ...
The impacts of invasive alien species are determined by their abundance, a relationship that usually does not follow linear trends owing to the complexity of ecological interactions. Abundance-impact curves are essential for informing evidence-based management interventions because they can reveal how per-capita impact changes as the invader become more abundant. Across 12 invasion gradients occurring in two areas, we constructed abundance-impact curves for the invasive grass Urochloa decumbens in a tropical savanna (Cerrado). We used generalized additive models to assess how increases in the invader’s abundance influenced system properties from the microhabitat to ecosystem levels. At the microhabitat level, increasing invader abundance resulted in nonlinear effects on bare soil and illuminance but a linear reduction in temperature fluctuations. The specific leaf area of dominant plants linearly increased with invader abundance. We found higher per-capita effects of Urochloa decumbens on the native graminoid cover when the invader was at low levels of abundance. Conversely, the per-capita effects on native species richness were higher at moderate levels of invasion. These results indicate the immediate impacts of the invader on the abundance of functionally similar native grasses but greater impacts on species richness only at moderate levels of invasion. The total biomass increased through the invasion gradient. Despite these changes, the abundance of invasive species did not influence the ecosystem properties. Our findings support the functional redundancy between Urochloa decumbens and native dominant grasses; however, despite this similarity, Urochloa decumbens promotes negative impacts at the microhabitat, organism, and community levels.
... Finally, macro-scale analyses could entail intrinsic biases in the representation of key features or attributes. For example, certain historically overlooked biomes may continue to remain ignored 23 , habitats presumed to be 'unproductive' may not be prioritized (for example, grasslands 24 ), indices such as species richness, which ignore community composition, may discount rarity or endemism 25 , PAs or 'intact' wilderness areas may take precedence over heterogeneous multi-use conservation landscapes 26,27 and important dimensions, such as human populations, may be excluded altogether 28 . ...
... Finally, macro-scale analyses could entail intrinsic biases in the representation of key features or attributes. For example, certain historically overlooked biomes may continue to remain ignored 23 , habitats presumed to be 'unproductive' may not be prioritized (for example, grasslands 24 ), indices such as species richness, which ignore community composition, may discount rarity or endemism 25 , PAs or 'intact' wilderness areas may take precedence over heterogeneous multi-use conservation landscapes 26,27 and important dimensions, such as human populations, may be excluded altogether 28 . ...
Biodiversity conservation and human well-being are tightly interlinked. Yet, mismatches in the scale at which these two priority issues are planned and implemented have exacerbated biodiversity loss, erosion of ecosystem services and declining human quality of life. India houses the second largest human population on the planet, while < 5% of the country's land area is effectively protected for conservation. This warrants landscape-level conservation planning through a judicious mix of land-sharing and land-sparing approaches combined with the co-production of ecosystem services. Through a multifaceted assessment, we prioritize spatial extents of land parcels that, in the face of anthropogenic threats, can safeguard conservation landscapes across India's biogeographic zones. We found that only a fraction (~15%) of the priority areas identified here are encompassed under India's extant Protected Area network, and furthermore, that several landscapes of high importance were omitted from all previous global-scale assessments. We then examined the spatial congruence of priority areas with administrative units earmarked for economic development by the Indian government and propose management zoning through state-driven and participatory approaches. Our spatially explicit insights can help meet the twin goals of biodiversity conservation and sustainable development in India and other countries across the Global South.
... The conversion of grassy biomes into woody plantations has become an emerging global activity (Hoekstra et al. 2005;Bond & Parr 2010;Veldman et al. 2015a). Today, approximately 300 million hectares of the Earth's land surface are under tree monocultures (FAO 2021). ...
The replacement of grassy vegetation by tree monocultures has become an emerging global activity. In South America, about half a million hectares of new plantations are incorporated each year, typically conducted with fast-growing exotic species, like Pinus and Eucalyptus species. However, information about the potential for spontaneous recovery of these grasslands is almost nonexistent. We assessed the biotic and abiotic legacies left by a 7-year plantation of Pinus taeda on a natural temperate subhumid grassland of Uruguay. In a paired sampling design, comparing a clear-cut P. taeda plantation and a natural grassland, we analyzed the vegetation richness, cover and composition, the seed bank size and composition, and chemical soil parameters. Afforestation reduced species richness and vegetation cover by 30 and 58%, respectively. Also, species composition differed considerably between sites. Afforestation had a strong negative effect on grass species, excluding the shade-intolerant C4 grasses that dominate in the grassland. Seed-bank richness did not differ between sites, but the total seedling density was significantly higher in the plantation compared to the grassland (6,620 and 4,420 seeds/m2 , respectively), mainly due to the contribution of forbs. Only 30% of the seed bank species were shared between the two sites. In terms of soil chemical parameters, afforestation induced soil acidification (deviation by 0.15–0.20 pH units) and reduction in soil carbon and cation (Ca and K) concentrations (deviation by 30, 20, and 40%, respectively). Our study showed limited possibilities for passive restoration of a natural grassland of Uruguay after a Pinus afforestation event.
... Decades of research in tropical grasslands and savanna have focused on the recognition that fire and megafaunal herbivory are needed for their maintenance (Scholes and Archer, 1997;Hoffmann et al., 2003;Sankaran et al., 2008;Staver and Bond, 2014), particularly when rainfall is sufficient to support tree growth (Sankaran et al., 2005). As a result, grasslands and savanna are often considered to be anthropogenically derived through disturbance (e.g., fire) or degradation of forest ecosystems (Bond and Parr, 2010), and the loss of grasslands and savanna has not attracted the same level of concern as tropical deforestation. (Parr et al., 2014;Murphy et al., 2016). ...
The Terai-Duar Savanna and Grassland ecoregion (hereafter Terai), located at the base of the Himalayas in the Indian subcontinent, support diverse ecosystems with pure grasslands, savanna, and forests in varying proportions. There are indications that grasslands and savanna are being lost to woody encroachment across the ecoregion. A significant fraction of plant and animal taxa are endemic to grasslands, so the decline of grasslands is likely to impact biodiversity and ecosystem function. We assessed large-scale vegetation changes to Terai habitats over three decades (1989-2019) and quantified the role of environmental factors in driving the observed changes. Selecting eight large protected wildlife habitats (four each from India and Nepal), we performed supervised vegetation classification for three-time points. We then quantified grassland-woodland transitions and used Bayesian Conditional Autoregressive spatial models to test the influence of climatic, environmental, and anthropogenic factors on observed changes. Including the protected sites with substantial grassland areas, we found that the total extent of grasslands was 1417 km 2 (28 % of total area) in 1988-1989, which declined by 34.4 % to 923 km 2 in three decades, while woodland area increased by 8,7% from 3235 km 2 to 3516 km 2. Grasslands were also converted to cropland or inundated by flooding, but to a lesser extent. Dry season grass fire had the strongest influence on grassland persistence, followed by anthropogenic impacts. However, the eight sites differed with respect to the nature and extent of the changes in vegetation transitions, perhaps reflecting site differences in climatic conditions and anthropogenic influence.
... Tropical savannas have evolved along with fire for millions of years (Hardesty et al. 2005;Simon et al. 2009). Hence, the structure and biodiversity of these biomes are maintained by recurrent low-intensity fires at the end of the dry season (Bond and Parr 2010;Durigan 2020). However, in the last 50 years, anthropogenic activities have increased fire frequency and altered the timing of burning, leading to high-intensity, catastrophic wildfires in fire-dependent ecosystems (Legge et al. 2008). ...
Foreseeing faunal responses to fire is a challenging issue, due to the context-dependent effects of fire. Although previous studies have registered declines in the abundance of vertebrates, particularly small mammals, following changes in fire regimes,
the mechanisms driving these changes are still poorly understood. Hence, we investigated the effects of a severe fire on the
abundance, survival, and body condition of a semelparous didelphid (Gracilinanus agilis) inhabiting one of the largest Cerrado remnants in the Triangulo Mineiro region. Using a before–after approach, G. agilis individuals were monitored from
2011 to 2016 through monthly live-trapping sessions. Gracilinanus agilis population followed repeated oscillations every
year, with marked declines in abundance after the mating season, irrespective of the 2014´s fire. Although fire reduced population size, it did not lead to a precipitous decline in G. agilis abundance. Survival rates were not affected by fire; instead were
determined by the sex and breeding status of individuals. The fire caused a decrease only in female body condition, which
resulted in a reduced length of the breeding season and a lower number of juveniles following the disturbance. Our results
support the contention that fire affects small mammals indirectly, mainly through its effects on recruitment. The observed
weak fire effects on the population level seem to be associated with the less sensitive dynamics of fast-living species. Hence,
we emphasize the need to investigate the mechanisms driving faunal responses to fire, especially considering the recent
changes in fire regimes and the role of life histories on species responses.
... Historically, the SGP was primarily grassland and open savanna, maintained by the endogenous processes of fire and herbivory (e.g. Bison; Bond and Parr, 2010). Since the late 1800s, the European settlement brought changes to the landscape. ...
Woody plant encroachment has been long observed in the southern Great Plains (SGP) of the United States. However, our understanding of its spatiotemporal variability, which is the basis for informed and targeted management strategy, is still poor. This study investigates the encroachment of evergreen forest, which is the most important encroachment component in the SGP. A validated evergreen forest map of the SGP (30 m resolution , for the time period 2015 to 2017) from our previous study was utilized (referred to as evergreen_base). Sample plots of evergreen forest (as of 2017) were collected across the study area, based on which a threshold of winter season (January and February) mean normalized difference vegetation index (NDVI winter) was derived for each of the 5 sub-regions, using Landsat 7 surface reflectance data from 2015 to 2017. Then a NDVI winter layer was created for each year within the four time periods of 1985-with winter season surface reflectance data from Landsat 4, 5, and 7. By applying the sub-region specific NDVI winter thresholds to the annual NDVI winter layers and the evergreen_base, a SGP evergreen forest map was generated for each of those years. The annual evergreen forest maps within each time period were composited into one. According to the resulting four composite evergreen forest maps, mean annual encroachment rate (km 2 /year) was calculated at sub-region and ecoregion scales, over each of the three temporal stages respectively. To understand the spatiotemporal variability of the encroachment, the encroachment rate at each temporal stage was related to the corresponding initial evergreen forest area, mean annual precipitation (MAP), and mean annual burned area (MABA) through linear regression and pairwise comparison. Results suggest that most of the ecoregions have seen a slowing trend of evergreen forest encroachment since 1990. The temporal trend of encroachment rate tends to be consistent with that of MAP, but opposite to that of MABA. The spatial variability of the encroachment rate among ecoregions can be largely (>68%) explained by initial evergreen forest area but shows no significant relationship with MAP or MABA. These findings provide pertinent guidance for the combat of woody plant encroachment in the SGP under the context of climate change.
... of the global grassland cover has already been lost(Bond and Parr 2010). My results add to these statistics; open savanna was amongst the most threatened habitats in the study area with a higher level of fragmentation relative to the other habitat types. ...
Following a ‘competitive release’ triggered by removal or extinction of large carnivores, meso-carnivores experience an increase in their population size and expand their distribution extents. In many systems, multiple meso-carnivores may simultaneously experience such a release, inducing alterations in their interspecific interactions. These processes may become more complex in human-use landscapes. While proximity to humans provides food provisioning opportunities, they also expose meso-carnivores to competition and predation by free-ranging dogs. Such interactions may further intensify in resource-restricted environments characterized by extreme climatic conditions and limited resource availability. In this study, I assessed the status of the habitats available to meso-carnivores and examined their spatial and temporal responses to each other, and to
anthropogenic factors in a large carnivore compromised, human-use semi-arid landscape. The study was conducted in an 800 km2 area in mainland Kutch, Gujarat. Meso-carnivore detection/non-detection data was collected using a combination of camera trap and indirect sign surveys following an occupancy framework. These were used to model patterns of habitat use and interspecific interactions against both ecological and anthropogenic covariates. Relative to the other habitats in the landscape, open savanna was the most fragmented. Out of the four focal species, open savanna was also the optimal habitat for golden jackal and Indian fox. The species showed both interspecific spatial avoidance (golden jackal–Indian fox and jungle cat–Indian fox) and spatio-temporal association (golden jackal–jungle cat and Indian fox–desert cat). Except for the species pair, Indian fox–desert cat, there was no effect of free-ranging dogs on either the presence of or the co-occurrence between the meso-carnivores. Whereas, the HI (a combined index of the impacts of settlements, roads and wind turbines) had a negative effect on the presence of two species (golden jackal and Indian fox) and the co-occurrence between five of the six species pairs. The results reconfirm the vulnerability of open savannas and highlights their importance to meso-carnivores. However, human impacts in these habitats are rising owing to their mis-categorisation as ‘wastelands’ in Indian land-use policy. The resultant human-induced spatial partitioning between species with similar habitat associations may lead to enhanced competition for limited space. Partitioning in time may not be feasible as the species are already restricted to
nocturnality, and a reduced activity period may entail greater bio-energetic costs in a resource-restricted landscape. This could potentially lead to loss of sensitive species and simplification of the meso-carnivore community in the long-term. Considered together, findings from this study offer insights on how conservation interventions need to consider species-specific responses and the complex interplay amongst species in multi-carnivore systems in shared landscapes.
... The decrease in grassland area coincides with what happened in other grasslands around the world (Bond and Parr, 2010;Lark et al., 2015;Neke and Du Plessis, 2004;Veldman et al., 2015) and alerts about the conservation status of this biome, often forgotten in the conservation agenda (Hoekstra et al., 2005;Overbeck et al., 2007;Silveira et al., 2020;Watson et al., 2016). According to Oyarzabal et al. (2020) there are 99 protected areas in RPG, which cover between 3.7% and 6.8% of the biome extent, depending on the considered regional limits. ...
The Río de la Plata Grasslands (RPG) region is the largest area of the temperate humid and sub-humid grasslands biome in South America and one of the largest in the world. The region is located on fertile soils, generally very suitable for agricultural development, so it is undergoing an intense land cover change process. Our knowledge of these changes remains incomplete. Most regional-scale studies have been conducted over specific periods, limited subsets of the RGP, coarse resolution and, in general, used land cover classes that are not readily compatible. In this work we described and analyzed the land cover changes in the entire RPG region for the first two decades of the 21st century, especially those related to grasslands loss. We generated annual land cover maps with 30-meter resolution that discriminate between 8 categories: native woody formation, forest plantation, swampy areas and flooded grassland, grassland, farming, non-vegetated area, water and non-observed. The map series was evaluated for the years 2001 and 2018 using a completely independent dataset, selected by stratified randomized sampling. Overall accuracy was 73.5% and 77.8% for 2001 and 2018, respectively, with user and producer accuracies that varied between classes and years. In 20 years, RPG region lost, at least, 2.4 million ha of grassland (9% of the remaining grassland area in 2001). Most of these losses are concentrated in Brazil and Uruguay and are associated with new agricultural or forestry areas that increased by 5% and 100%, respectively. Our maps allow a comprehensive understanding of the transformation processes that RPG are undergoing and provide the context on which to explore a large set of hypotheses related to ecosystem structure and functioning. It will also contribute to improving decision-making at both the regional and national levels.
... Open tropical biomes span over a fifth of global landcover, comprising ecosystems where the climate is wet and warm enough to support forests but instead supports grasslands, shrublands, open woodlands, and savannas (Bond, 2019). By contrast, closed biomes, which receive substantially more academic attention (Bond & Parr, 2010), comprise the forested ecosystems of the world. These varied biomes represent distinct functional environments. ...
Ziziphus (Rhamnaceae) is a widely distributed genus across the Australasian and African tropics with unusual diversity in habit, and many species of significance to people. Here, we quantify the environmental limits of Ziziphus species and examine inter‐specific relationships among functional traits, environment, biome, and range size. We developed a curated geolocation database for Ziziphus and used it to examine the environmental limits of the genus relative to temperature, rainfall, and seasonality. To assess the relationship between biome and habit, permutational analysis of variance was used, while hierarchical clustering was used to determine whether habit, leaves, and fruit traits were related to biome. For 40 species with adequate geolocation data, range size was calculated to assess its relationship with habit, biomes, and cultivation. Finally, niche identity tests were used to determine niche equivalency among cultivated and non‐cultivated species. Liana species are restricted to closed forests and the geoxylic habit is found only in open grasslands. Further, habit is significantly associated with range size, with trees having on average larger range sizes than shrubs, lianas, and geoxyles, but biome was not correlated with range size. Cultivated species have ranges ~10 times that of non‐cultivated tree species and with significantly different and broader environmental niches. The unusually wide distribution of Ziziphus can be explained by its diversity of habits associated with different biomes spanning continents. This, along with the usage of many Ziziphus species by people for their fruits, expands the range and environmental occupation of the genus. We quantified the environmental limits of Ziziphus species and examined inter‐specific relationships among functional traits, environment, biome and range size. The unusually wide distribution of Ziziphus can be explained by its diversity of habits associated with different biomes spanning continents. This, along with the usage of many Ziziphus species by people for their fruits, expands the range and environmental occupation of the genus.
... Evergreen forests typically provide shaded, mesic conditions, structural complexity, and environments with few or no frosts (Duker et al. 2015;Lusk and Laughlin 2017;Charles-Dominique et al. 2018). In contrast, open or non-forest environments have one or a combination of drought, frosts, fire and low shade (Bond and Parr 2010;Heenan and McGlone 2013;Charles-Dominique et al. 2018). ...
Diversification of woody plant lineages in New Zealand has unfolded in complex physiographic, climatic, and environmental contexts. Many tree and shrub lineages have existed in New Zealand since the late Cenozoic when Forest was the dominant biome, subsequently diversifying (or continuing to diversify) during the Pliocene/Pleistocene as Open (below treeline) and Alpine biomes emerged. We examine the links between biomes occupied, traits, and diversification. In particular, whether traits are phylogenetically conserved or ecologically constrained and their relationship to biomes occupied. We focus on Melicytus, Myrsine and Pseudopanax which occur across Forest, Open, and Alpine biomes. Our approach combines measured traits and modelled niche traits of extant species to examine the importance of biome occupancy and biome shifts on trait evolution in these lineages. Our results demonstrate trait values are filtered by biomes in these lineages and can predict biomes occupied. However, few biome shifts were associated with trait evolution, typically only biome shifts into extreme environments (Alpine) involved trait innovations. In addition to biomes, trait evolution can also be influenced by species age, trait lability and broad climatic change. Integrating functional traits in a phylogenetic framework can identify how evolutionary and ecological features create modern biogeographic patterns in New Zealand.
... Lastly, our study only included forested ecosystems. However, much of the world's biodiversity exists in a non-forested environment, and these habitats are also under anthropogenic pressure (Bond and Parr, 2010;Dou et al., 2018;Strassburg et al., 2017). ...
Establishing Protected areas (PAs) could displace or cause ‘leakage’ of deforestation into adjacent areas. Such leakage would potentially offset PAs' conservation effort by jeopardizing forest conservation goals and impeding financial mechanisms such as Reducing Emissions from Deforestation and forest Degradation - REDD+. Here we investigate forest loss inside PAs' borders and whether leakage occurred following the establishment of new PAs (n = 425) within the Amazon and the Atlantic forests in Brazil between 2004 and 2017. We applied a Before-After-Control-Intervention statistical design with a matching approach to evaluate deforestation leakage from PAs' establishment using a spatial (inside and outside PAs)– temporal (before and after PA establishment) measure of deforestation rates. We also used “Random Forest” to investigate the drivers of the effect of PAs' establishment on their surrounding areas. We found that when PAs' establishment led to reducing deforestation inside their boundaries, their surrounding also experienced a reduction in deforestation (“blockage”). Similarly, when PAs' establishment could not reduce deforestation inside their boundaries, their surroundings also experienced increased deforestation. Such a pattern was most common for Indigenous territories, especially in the deforestation arch in the Amazon. However, we did not find significant evidence for leakage as PAs' surroundings with a significant increase in deforestation were associated with PAs unable to significantly reduce deforestation within their boundaries. Therefore, “leakage” should not limit the establishment of new PAs. Instead, greater investments into reinforcement are needed for existing PAs, with high priority given to Indigenous Territories.
... Chibilyov, 2002;Pfadenhauer & Klötzli, 2014;Wesche et al., 2016;Erd} os et al., 2018a;Wagner et al., 2020). Indeed, around the globe there are many examples of how climate constrains tree growth: arctic and alpine timberlines develop due to low temperature and arid timberlines are the result of low moisture availability (Stevens & Fox, 1991;Breshears, 2006;Bond, 2019). Consistent with these patterns, at the southern edge of the temperate forests of Eurasia, increasing climatic harshness deriving from decreasing precipitation and increasing annual temperature range (increasingly hot summers but still cold winters) plays a major role in constraining forest growth (Walter & Breckle, 1989;Schultz, 2005). ...
Recent advances in ecology and biogeography demonstrate the importance of fire and large herbivores – and challenge the primacy of climate – to our understanding of the distribution, stability, and antiquity of forests and grasslands. Among grassland ecologists, particularly those working in savannas of the seasonally dry tropics, an emerging fire–herbivore paradigm is generally accepted to explain grass dominance in climates and on soils that would otherwise permit development of closed‐canopy forests. By contrast, adherents of the climate–soil paradigm, particularly foresters working in the humid tropics or temperate latitudes, tend to view fire and herbivores as disturbances, often human‐caused, which damage forests and reset succession. Towards integration of these two paradigms, we developed a series of conceptual models to explain the existence of an extensive temperate forest–grassland mosaic that occurs within a 4.7 million km2 belt spanning from central Europe through eastern Asia. The Eurasian forest‐steppe is reminiscent of many regions globally where forests and grasslands occur side‐by‐side with stark boundaries. Our conceptual models illustrate that if mean climate was the only factor, forests should dominate in humid continental regions and grasslands should prevail in semi‐arid regions, but that extensive mosaics would not occur. By contrast, conceptual models that also integrate climate variability, soils, topography, herbivores, and fire depict how these factors collectively expand suitable conditions for forests and grasslands, such that grasslands may occur in more humid regions and forests in more arid regions than predicted by mean climate alone. Furthermore, boundaries between forests and grasslands are reinforced by vegetation–fire, vegetation–herbivore, and vegetation–microclimate feedbacks, which limit tree establishment in grasslands and promote tree survival in forests. Such feedbacks suggest that forests and grasslands of the Eurasian forest‐steppe are governed by ecological dynamics that are similar to those hypothesised to maintain boundaries between tropical forests and savannas. Unfortunately, the grasslands of the Eurasian forest‐steppe are sometimes misinterpreted as deforested or otherwise degraded vegetation. In fact, the grasslands of this region provide valuable ecosystem services, support a high diversity of plants and animals, and offer critical habitat for endangered large herbivores. We suggest that a better understanding of the fundamental ecological controls that permit forest–grassland coexistence could help us prioritise conservation and restoration of the Eurasian forest‐steppe for biodiversity, climate adaptation, and pastoral livelihoods. Currently, these goals are being undermined by tree‐planting campaigns that view the open grasslands as opportunities for afforestation. Improved understanding of the interactive roles of climate variability, soils, topography, fire, and herbivores will help scientists and policymakers recognise the antiquity of the grasslands of the Eurasian forest‐steppe.
... while benefiting from carbon credits set up through international financial instruments [1]. The effects of fire on the savannah have given rise to a large number of studies [13][14][15][16]. However, little is known about its consequences on carbon sequestration. ...
... In the present study, rainfall in the preceding year was below average and about average during the experiment. During wetter conditions, perennial grasses are known to have a competitive advantage over smaller-statured forb species for resources such as water, light and nutrients (Bond and Parr 2010;Coller et al. 2013). The competitive effects of increased grass growth with average rainfall is a potential explanation for the decline in the number of ramets in unburnt plots at the start of the experiment compared with the previous year. ...
Context Many grassland forb populations have greatly diminished because their habitat coincides with prime agricultural land and remnants lack appropriate disturbance regimes. Aim The aim of the current study is to examine the survivorship, vegetative recruitment, biomass and sexual reproduction of S. papaverifolium in response to burning in one of a few natural surviving populations in Queensland. Methods We monitored the survivorship, vegetative recruitment, and reproduction of a rare native forb, Solanum papaverifolium, within a randomised replicated experiment by using 14 circular plots measuring 12.56 m2 (2 m radius). Key results Plant survival rate after 5 months was greater in the burnt plots (56%) than the unburnt plots (44%). Vegetative recruitment from suckers in the burnt plots was almost twice that in the unburnt plots. The probability of flowering was also enhanced by burning. Fruit set in new recruits was higher in the burnt plots (20%) than in the unburnt plots (5%). Whereas fruiting did not occur in unburnt plots for surviving plants that flowered, only 1% fruited in the burnt plots. Seedling production was not observed. Conclusion Previous studies have demonstrated that the subtropical grassland flora in the study region is unaffected by burning, whereas the present study suggests that some grassland species respond positively to burning. Implications Although fire increased flowering in this species, suggesting that fire may be a useful tool to stimulate sexual reproduction, ongoing research is required to understand the precise factors that promote flowering after burning and the barriers to seedling reproduction.
... Future conservation, management and restoration of this tropical montane forest system must thus separately target the upper and lower elevation sholas to conserve the entirety of its biodiversity. The high spatial variation in phylogenetic diversity found in this study corroborates the ancient nature of these forestgrassland mosaics [73] and supports the crucial role of microclimatic refuges in upper montane habitats [74]. Area under tropical evergreen forest decreases significantly above 2000 m elevation in the Western Ghats [75], making large (greater than 50 ha) shola patches rare above 2000 m. ...
Frost and freezing temperatures have posed an obstacle to tropical woody evergreen plants over evolutionary time scales. Thus, along tropical elevation gradients, frost may influence woody plant community structure by filtering out lowland tropical clades and allowing extra-tropical lineages to establish at higher elevations. Here we assess the extent to which frost and freezing temperatures influence the taxonomic and phylogenetic structure of naturally patchy evergreen forests (locally known as shola ) along a mid-upper montane elevation gradient in the Western Ghats, India. Specifically, we examine the role of large-scale macroclimate and factors affecting local microclimates, including shola patch size and distance from shola edge, in driving shola metacommunity structure. We find that the shola metacommunity shows phylogenetic overdispersion with elevation, with greater representation of extra-tropical lineages above 2000 m, and marked turnover in taxonomic composition of shola woody communities near the frost-affected forest edge above 2000 m, from those below 2000 m. Both minimum winter temperature and patch size were equally important in determining metacommunity structure, with plots inside very large sholas dominated by older tropical lineages, with many endemics. Phylogenetic overdispersion in the upper montane shola metacommunity thus resulted from tropical lineages persisting in the interiors of large closed frost-free sholas, where their regeneration niche has been preserved over time.
... In addition, C. pruskiana was collected a few times, and luckily for its conservation, 50% of specimens were collected in Campos do Jordão State Park, one protected area. Despite this, agriculture, urbanization, and forestry are threats to this species as it occurs in grasslands (Bond and Parr 2010;Andrade et al. 2016). So, C. pruskiana is informally considered Critically Endangered (CE). ...
— We herein present nomenclatural and taxonomic novelties in Calea sect. Meyeria from Brazil. Calea pruskiana is a new species related to C. triantha and can be distinguished by the acute or cuneate, rarely attenuate leaf apex (vs. obtuse), slightly branched capitulescence (vs. profusely branched), and ray florets 18‐21.7 mm long (vs. 9.2‐15.3 mm). Calea hispida f. subintegerrima is lectotypified, recombined, and elevated to species level as Calea subintegerrima , which also resembles C. triantha , however differs from it by the usually glabrous abaxial leaf surface (vs. usually hispid), glandular-punctate peduncle (vs. glands absent), and cypselae with hirsute ribs (vs. pilose ribs). These species are described and illustrated, their geographic distributions are mapped, and their taxonomic affinities are discussed. Furthermore, a new terminology is proposed to describe more accurately the pappus scale size variation according to the relative length of the scales and the occurrence of combinations of pappus scales of different lengths in the same capitulum.
... However, forbs are important for grassland structure and function. Forbs contribute the majority of floral species and functional richness in grasslands (Bond & Parr, 2010;Bråthen et al., 2021;Siebert & Dreber, 2019), influence nutrient and water cycling dynamics (Gould et al., 2016;Tilman et al., 2001), alter soil physical characteristics (Gould et al., 2016), provide important habitat and food resources for vertebrates and invertebrates (Andersen et al., 2018;Haddad et al., 2009;Potts et al., 2009), and are important sources of food and medicine for indigenous people globally (Carbutt et al., 2016;Moerman, 1998;Siebert & Dreber, 2019). Conservation of forbs has been identified as a priority for restoration and protection of the important ecosystem services that grasslands provide (Bråthen et al., 2021;Sheley et al., 2006;Siebert & Dreber, 2019). ...
Grasslands are among the most threatened and least protected terrestrial biome. Grassland forbs: (1) account for most of the floral diversity; (2) are not well studied because they have been overshadowed by grass-centered research; and (3) have been a major source for biodiversity loss. The Pacific Northwest Bunchgrass Prairie (PNB) of North America is one of the most endangered grasslands on earth. Knowledge of vegetation community dynamics in the PNB is based primarily on bunchgrasses. There is a paucity of information related to the PNB's diverse native perennial forbs (hereafter “forbs”). Consequently, PNB forb community patterns and dynamics are largely unknown. We describe forb community structure and its relationship to environmental factors and phenology. We sampled 29 plots in the Starkey Experimental Forest and Range, northeastern Oregon, at three different times during 2016 (April; May; July). Nonmetric multidimensional scaling (NMS) indicated that the dominant gradient in forb composition was related (R2 = 0.66) to slope and soil P and K, contrasting flat, poorly drained soils (scabflats) at one end with steep, well-drained soils at the other end. The secondary gradient (R2 = 0.16) contrasted deeper, finer textured soils at one end with shallow, rocky soils at the other. Forb richness decreased by ~40% from April to July. NMS and Indicator Species Analysis (ISA) showed that most forbs had affinities toward spring. Ubiquitous forbs (e.g., Triteleia grandiflora, Camassia quamash) were sparse to absent by July. Contradictory to general descriptions of the PNB, forb cover and richness in drought-prone sites were comparable to mesic sites when spring data were considered. Our findings suggest that PNB grasslands contain diverse forb communities that are structured primarily by water drainage and soil depth. Conventional sampling concomitant with peak grass biomass is insufficient to characterize PNB forb communities, particularly for scabflats and the most drought-prone soils.
... The mountain meadows in Romania are an extraordinary source of biodiversity in Europe [1]. The diversity of biomes is the key to the stability and maintenance of the entire grassland ecosystem [2]. Both above-and below-ground biodiversity are closely linked and are influenced by a cumulative effect of biotic and abiotic factors [3]. ...
Long-term fertilization targets mycorrhizal fungi adapted to symbiotic exchange of nutrients, thus restricting their colonization potential and re-orienting the colonization strategies. The MycoPatt tool has a high applicability in quantifying the symbiotic process with the identification of mycorrhizal indices and projection of mycorrhizal patterns. Organic treatments increase the symbiotic process, visible in values of colonization frequency and intensity, with about 6% more than the native status of colonization. At the opposite pole, organic-mineral treatments decrease the colonization parameters by up to half of the organic treatment. All of the colonization parameters show significant correlations, except for the arbuscules/vesicle ratio (0.03). All the applied treatments, except for the organic one, record multiple root segments with a colonization degree lower than 10%. The application of treatments changes the strategy of native colonization from a transfer (40%) and storage (37%) to a predominant storage (50%) for organic treatment, and are mainly proliferative between 38–50% in mixed and mineral treatments. The high amount of mineral components increases also the presence of resistance conditions strategies. The use of mycorrhizal pattern maps, with the inclusion of colonization strategies, presents an important direction in understanding the evolution of mutual relations, and to explore in-depth the efficiency of the whole symbiotic process.
... Far less recognized is that one third of the country supports ecosystems that are not humid tropical forests, including the xeric forest-woodlands of the Caatinga (Moro et al., 2016) and extensive grasslands and savannas . In this paper, we focus on Brazil's underappreciated savannas and grasslands, which we collectively referr to as 'grassy ecosystems', because they are dominated by grasses and grass-like plants (Bond and Parr, 2010). ...
In Brazil, the country with the highest plant species richness in the world, biodiverse savannas and grasslands – i.e., grassy ecosystems, which occupy 27% of the country – have historically been neglected in conservation and scientific treatments. Reasons for this neglect include misconceptions about the characteristics and dynamics of these ecosystems, as well as inconsistent or regionally restricted terminology that impeded a more adequate communication about Brazil's savannas and grasslands, both within the country and internationally. Toward improved communication and recognition of Brazil’s diversity of ecosystems, we present the key drivers that control the main types of grassy ecosystems across Brazil (including in regions of the country where forests dominate). In doing so, we synthesize the main features of each grassy ecosystem in terms of physiognomy and ecological dynamics (e.g., relationships with herbivores and fire). We propose a terminology both for major grassland regions and for regionally relevant vegetation physiognomies. We also discuss terms associated with human land management and restoration of grassy ecosystems. Finally, we suggest key research needs to advance our understanding of the ecology and conservation values of Brazil’s grassy ecosystems. We expect that a common and shared terminology and understanding, as proposed here, will stimulate more integrative research that will be fundamental to developing improved conservation and restoration strategies.
... The occurrence of fire is determined to a large degree by the flammability of vegetation Boer, De Dios, Stefaniak, & Bradstock, 2019;Bradstock, 2010), which is the capacity of different plants and its components to burn and sustain a flame after encountering an ignition source (Anderson, 1970;Pausas, Keeley, & Schwilk, 2017). The most fire-prone ecosystems globally are tropical savannas (Bond & Van Wilgen, 1996;Simpson et al., 2016), covering about 20% of the Earth's land surface, due to the combination of highly seasonal rainfall and a continuous herbaceous layer that is typically dominated by C 4 grasses (Bond & Parr, 2010;Parr, Lehmann, Bond, Hoffmann, & Andersen, 2014;Scholes & Archer, 1997). The combination of seasonal drought and high herbaceous biomass ensures an annual availability of fuel for fire, and the continuous nature of the herbaceous layer promotes fire spread (Archibald, Lehmann, Gómez-Dans, & Bradstock, 2013;Linder, Lehmann, Archibald, Osborne, & Richardson, 2018). ...
The herbaceous layer is the dominant fuel for fire in tropical savannas, the world's most fire‐prone biome. However, little is known about variation in flammability among different growth forms, as well as how flammability varies seasonally. Here, we describe such variation in Brazilian Cerrado, the world's most phytodiverse tropical savanna. We measured three components of flammability (maximum burning temperature, burning rate, and burnt biomass) and morphophysiological traits (dead biomass percentage, moisture content, and specific leaf area) of five species of each of grasses, forbs, and shrubs throughout the wet and dry season. We found that grasses were the most flammable growth form and that their flammability was highest in the middle of the dry season when the percentage of dead biomass was highest (60%), and moisture content was low (25%). Flammability did not vary across seasons for either forbs or shrubs. Dead biomass, moisture content, and specific leaf area were all strongly correlated with flammability. These findings explain the dominant role played by grasses as drivers of flammability in tropical savannas, and they improve our understanding of how savanna flammability varies across space and time depending on the composition of the grass layer and its level of seasonal curing. This enables a better prediction of fire spread and behavior in different savanna types based on grass‐layer composition. Grasses are the most flammable growth form and their flammability vary between wet and dry season. Shrubs and forbs does not vary their flammability across seasons. Such findings explain the dominant role played by grasses and how savanna flammability vary across space and time.
... However, most of these studies did not look at forb diversity, a part of the vegetation typically neglected in savanna studies (Siebert and Dreber 2019). Studies on savanna forb diversity and its relationship to fire are limited; this is perhaps due to a lack of plant surveys or lack of data collection in all seasons, particularly postfire when many forbs emerge (Bond and Parr 2010). Although fire has been shown to structure the savanna woody vegetation including recurrent fires creating cooler fire regimes which favour increased tree growth (Walters 2012), and the savanna flora is different from other Gabonese savannas ), fire's relation to the floral diversity remains unstudied. ...
Background and aims – Old-growth savannas in Africa are impacted by fire, have endemic and geoxylic suffrutices, and are understudied. This paper explores the Parc National des Plateaux Batéké (PNPB) in Gabon and the impact of fire on its flora to understand if it is an old-growth savanna. It presents 1) a vascular plant checklist, including endemic species and geoxylic suffrutices and 2) an analysis of the impact of fire on the savanna herbaceous flora, followed by recommendations for fire management to promote plant diversity.
Material and methods – 1,914 botanical collections from 2001–2019 collected by the authors and others were extracted from two herbaria databases in 2021 to create the checklist. The impact of fire was explored through a three season plot-based inventory of plant species (notably forbs and geoxylic suffrutices) in five annually, dry-season burned study areas located at 600 m in elevation. A two-factor ANOVA was conducted across two burn treatments and three season treatments.
Key results – The area has a vascular flora of 615 taxa. Seven species are endemic to the Plateaux Batéké forest-savanna mosaic. Seventeen species are fire-dependent geoxylic suffrutices, attesting to the ancient origins of these savannas. Burning promotes fire-dependent species.
Conclusion – The PNPB aims to create a culturally-adapted fire management plan. The combination of customary fire and fire-adapted species in the savanna creates a unique ancient forest-savanna mosaic in Central Africa that merits protection while recognising the role that the Batéké-Alima people have in shaping and governing this landscape.
... Fire is an ecologically important disturbance for many grassdominated vegetation types (Andersen et al., 2003;Bond and Keeley, 2005;Bowman et al., 2009). Globally, woody plants are reported to be expanding into grassy communities, especially in high rainfall, humid regions, such as on the margins of rainforest (Bond and Parr, 2010;Staver et al., 2011;Graw et al., 2016;Stevens et al., 2017). This has been linked to reduced fire occurrence and elevated atmospheric CO 2 (Bond and Midgley, 2000;Harrington and Sanderson, 1994;Crowley and Garnett, 1998;Higgins et al., 2000Higgins et al., , 2007Bond and Keeley, 2005;Gooden et al., 2009;Tng et al., 2012). ...
Fire plays an important role in maintaining grassy forests, and reduced fire frequency has been linked to encroachment of woody plants into grassy forests and woodlands globally. In Australia a range of threatened animals, including the northern population of the endangered eastern bristlebird (Dasyornis brachypterus), are dependent on grassy forests. We examined this issue by collating three decades of detailed monitoring and fire data for 43 current and historically-occupied bristlebird sites, and examined the relationships among fire history, bristlebird occupancy and habitat patch size/condition. Habitat patch size declined by over 50% between 1980 and 2009 due to woody plant encroachment. Bristlebird occupancy was associated with reduced habitat loss and time since fire, while reduced fire frequency was the main predictor of decline in grassy cover, a critical habitat element for bristlebirds. Our models suggested habitat loss was strongly influenced by fire history, particularly fire frequency, with reduced habitat loss associated with more-frequent burning. Native grass cover can return quickly, and remained high until 5–10 years post-fire; densest grass cover was found at sites with fire intervals of between 3.5 and 7 years. Active fire management, including regular ecological burning, is imperative for conservation of the eastern bristlebird and other threatened fauna that depend on these grassy forests. The massive changes in global patterns of fire currently occurring, and the threat this poses to biodiversity, make understanding the nuances of fire ecology, including the role of fire frequency, essential to improving conservation management.
... Fire is able to modify the structure, function and dynamics of savannah-woodland ecosystems (Bond & Archibald, 2003;Bond & Parr, 2010;Scholes & Walker, 1993) and is therefore managed in protected areas to achieve conservation goals by promoting preferred elements of fire regimes (i.e. fire size, intensity, season and frequency) (Nieman et al., 2021a). ...
Fire frequency affects vegetation structure and composition in savannah‐ woodlands, with the potential indirect consequence of affecting the habitat choice and space use of large mammals. Understanding these responses can assist with the development of appropriate fire management policies to conserve co‐existing species with different habitat requirements. In a natural experiment in Majete Wildlife Reserve, Malawi, we compared vegetation composition, woody plant structure and large (>5 kg) mammal assemblages on 10 frequently and 10 infrequently burnt 30‐ha plots, that had fire return intervals of <2.5 and >6 years, respectively, between 2001 and 2019. Fire frequency had little effect on woody plant composition, but did affect grass species composition. Frequent burning reduced mean tree height from 4 to 3 m, woody plant cover from 59% to 35%, and resulted in the dominance of short‐statured, less‐palatable grasses. Many mammal species showed clear preferences for either frequently burnt (e.g. buffalo, zebra, kudu, impala and sable) or infrequently burnt (e.g. nyala, bush pig, baboon, common duiker and vervet monkey) areas, while others (e.g. elephants and black rhinoceros) were not selective. We conclude that establishing a mosaic of patches exposed to different fire frequencies would allow for the persistence of all mammal species in the area by creating an optimal range of habitat types. La fréquence des incendies affecte la structure et la composition de la végétation dans les savanes boisées,avec la conséquence indirecte potentielle d'affecter les choix d’habitat et d'utilisation de l'espacedes grands mammifères. La compréhension de ces réponses peut aider le développement de politiques de gestion des incendies appropriées pour la conservation des espèces cohabitantes ayant des exigences différentes en matière d'habitat. Dans le cadre d’une étude réalisée dans la réserve naturelle de Majete, au Malawi, nous avons comparé la composition de la végétation, la structure des plantes ligneuses et les groupements de grandsde grands mammifères (>5 kg) sur 10 parcelles de 30 ha brûlées fréquemment et 10 parcelles brûlées rarement avec des intervalles de retour du feu<2,5 et >6 ans, respectivement entre 2001 et 2019. Alors que la fréquence des feux affecte peu la composition des plantes ligneuses, son effet sur la composition des espèces herbacées est considérable. Les brûlis fréquents ont réduit la hauteur moyenne des arbres de 4 à 3 m, la couverture des plantes ligneuses de 59 % à 35 % et le nombre d'espèces d'herbacés de 59% à 35%. Ils ont aussi entraîné la dominance d’espèces herbacéesmoins appétissantes et de petite taille. De nombreuses espèces de mammifères ont montré une nette préférence pour les zones fréquemment brûlées (par exemple, le buffle, le zèbre, le koudou, l'impala et la zibeline) ou peu brûlées (par exemple, le nyala, le cochon de brousse, le babouin, le Céphalophe commun et singe vervet), tandis que d'autres (par ex.les éléphants et les rhinocéros noirs) ne montrent pas de préférence. Nous concluons que l'établissement d'unemosaïque de parcelles exposées à différentes fréquences de feu permettrait la persistance de toutes les espèces de mammifères dans la région en créant une gamme optimale de types d'habitats.
... The high productivity in the wet season of mesic savannas promotes a period of intense grass growth, followed by the dry season that lowers biomass moisture creating a high fuel load (Higgins et al., 2000;Scheiter et al., 2012;February et al., 2013). Fires are likely to be the primary ecological process constraining woody biomass in savannas (Bond & Midgley, 2003;Van Wilgen et al., 2003;Bond & Parr, 2010;Hoffman et al., 2014). Fire varies in intensity and frequency, but at 1000 -1500 mm it can occur at intervals as short as 1-3 years (Bond & Midgley, 2001;Meyer et al., 2005;Higgins et al., 2007). ...
The genera Vachellia and Senegalia, of the family Fabaceae, with most species in these genera able to biologically able to fix nitrogen, play a major role in structuring southern African savannas and determining their productivity. The biogeography of Vachellia and Senegalia shows that they dominate African savannas in regions of water stress, high herbivory by browsing mammals (e.g., giraffe) and relatively fertile soils. The characteristic discontinuous tree cover of savanna ecosystems suggests that a complex set of environmental factors such as drought, herbivory, and fire limit tree establishment during early demographic stages (seedling survival). Most species in these two genera have a capacity to biologically fix nitrogen via mutualism with rhizobial bacteria. These bacteria are free living in the soil and infect roots to form root nodules, where N2 is converted into plant useable NH4 that is used in growth. However, little is known under what environmental circumstances these plants fix nitrogen. A new understanding of how water stress and herbivory influence the growth and N2 fixation dynamics of seedlings and saplings can provide knowledge needed to help reconcile the dynamics of savanna vegetation at wider scales.
Here, I aimed to determine the effects of water availability and herbivory on nodule development in Vachellia and Senegalia during early life stages and examine links to plant performance. To investigate these relationships I worked on two experiments. First, I conducted a glasshouse experiment examining the relationship between nodulation and water availability in seedlings (Chapter 2). Second, I worked on a 30 month field experiment that enabled me to examine questions around an interaction between nodulation and herbivory (Chapter 3).
In the glasshouse experiment I investigated the effects of water availability on growth (height, root: shoot ratio, biomass) and nodulation in Vachellia sieberiana and Vachellia erioloba seedlings over a four month period (Chapter 2). The seedlings were watered at either 4%, 8% or 16% soil moisture and were harvested at month intervals (2 months – Harvest 1, 3 months – Harvest 2, or 4 months – Harvest 3) to track nodule and biomass development. V. erioloba did not nodulate and was unaffected by changes in soil moisture and V. sieberiana seedlings nodulated under all soil moisture treatments. V. sieberiana seedlings grown in the driest conditions (4%) had the lowest nodule count likely as a lack of soil moisture immobilises rhizobia were the tallest plants. However, the nodules of V. sieberiana grown in 4% SMC had the largest biomass. Seedlings grown in 16% had the highest nodule count, and the lowest biomass. However, V. sieberiana grown in 8% soil moisture had the highest rate of biological nitrogen fixation (BNF) likely to be a product of N demand, coupled with optimal conditions for the rhizobia living in the soil. It was clear that age mattered, and plants that were three months old or more nodulated more prolifically, supporting previous research. I conclude that N2 fixation is energy expensive to plant therefore will only be invoked if the benefits outweigh the costs, but due to the complexity of the relationship and the many influencing factors there is an optimal stress level. This optimal stress level is where N2 fixation is required due to disturbed conditions, but the disturbance cannot be so great that it hinders the rhizobia bacteria, limiting nodule development. Furthermore, the ability to nodulate under disturbed conditions has created a niche for V. sieberiana allowing it to take advantage of stress that may weaken surrounding vegetation.
In my third chapter, I investigated how browsing herbivory of seedlings impacts above and below ground biomass and nodulation in Vachellia sieberiana, Vachellia exuvialis, and Senegalia nigrescens saplings. My study was part of a larger experiment located at the Wits Rural Facility, South Africa examining plant survival. My study species were germinated from seed and subsequently exposed clipped to mimic browsing at 3 months, 4 months, or 4 months old, with control plots not clipped. Plants were grown for two growing seasons and I harvested them at 30 months of age. Plants of V. sieberiana exposed to herbivory had a lower biomass than control plants. In contrast, the biomass of V. exuvialis was unaffected by herbivory when clipped at three or four months of age. S. nigrescens clipped at three months of age were able to recover lost above ground biomass. For all three species nodulation was stimulated when clipping took place at three months old or greater. I suggest that nodulation and consequent fixation enables woody legumes to compensate for the effects of herbivory facilitating plant establishment and enabling plants to escape the “browse” trap.
Overall, I found evidence that an ability to nodulate and fix nitrogen provides species of Vachellia and Senegalia the opportunity to compensate for tissue loss and damage as a result of stress and disturbance during juvenile life stages. However, among the species studied here, there is wide variation in the functional traits and responses of individual species, likely due to the wide range of environmental niches occupied by the species of these genera. To date, little work has been undertaken examining nodulation in savanna woody legumes in response to stress and disturbance. While it had previously been shown that nodulation enabled young plants from Vachellia to compete with grasses during establishment, my data demonstrate for the first time that browsing herbivory can also induce nodulation. Future work should expand experiments to a wider array of species from these genera in order to determine the degree to which species responses to herbivory and water stress can be generalised. Nodulation enables Vachellia and Senegalia seedlings to survive at the critical and vulnerable stage of development following germination.
Disturbance-dependent grasslands, often associated with hydromorphological and fire dynamics, are threatened, especially in subtropical climates. In the Nepalese and Indian Terai Arc Landscape at the foot of the Himalayas, natural and cultural grasslands serve a viable role for greater one-horned rhinoceros (Rhinoceros unicornis) and for grazers that form prey of the Royal Bengal tiger (Panthera tigris). The grasslands are vulnerable to encroachment of forest. We aimed to establish the effects of environmental drivers, in particular river discharge, river channel dynamics, precipitation and forest fires, on the spatio-temporal dynamics of these grasslands. The study area is the floodplain of the eastern branch of the Karnali River and adjacent western part of Bardia National Park. We created annual time series (1993–2019) of land cover with the use of field data, remotely sensed LANDSAT imagery and a supervised classification model. Additionally, we analysed the pattern of grassland patches and aerial photographs of 1964. Between 1964 and 2019, grassland patches decreased in abundance and size due to encroachment of forest. Outside the floodplain, conversion of grassland to bare substrate coincides with extreme precipitation events. Within the floodplain, conversion of grassland to bare substrate correlates with the magnitude of the annual peak discharge of the bifurcated Karnali River. Since 2009, however, this correlation is absent due to a shift of the main discharge channel to the western branch of the Karnali River. Consequently, alluvial tall grasslands (Saccharum spontaneum dominant) have vastly expanded between 2009 and 2019. Because the hydromorphological processes in the floodplain have become more static, other sources of disturbances – local flooding of ephemeral streams, anthropogenic maintenance, grazing and fires – are more paramount to prevent encroachment of grasslands. Altogether, our findings underscore that a change in the environmental drivers impact the surface area and heterogeneity of grassland patches in the landscape, which can lead to cascading effects for the grassland-dependent megafauna.
Cryptic species present a challenge for conservation, as undetected diversity may be lost. DNA barcoding of the mitochondrial cytochrome c oxidase subunit I (COI) has become a useful heuristic tool for delimiting species boundaries and detecting cryptic speciation across different animal taxa. 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 bat and bird species naturally breeding within the Afrotropics. Using Bayesian phylogenetic modelling, we assessed DNA barcode performance at species identification, and to detect instances of non-monophyly (indicating potential 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 geographic coverage. DNA barcodes afforded greater taxonomic resolution of Afrotropical bird species than of bats (96.8 % vs 84.0 %), with the bats reporting a higher species non-monophyly (25.5 % vs 4.8 %). Twenty-one bat species and fifteen bird species exhibited well-supported phylogenetic complexity. Additionally, deep intraspecific divergences (>2.0 %) were observed in one bat species and fifteen bird species. These instances of non-monophyly and deep intraspecific divergences may represent cryptic speciation within these volant taxa, suggesting greater hidden diversity of more sedentary African fauna. They also highlight the importance of areas such as the Congo-Guinean lowland forests to endemic vertebrate diversity. The current taxonomic status of birds is better supported by this molecular evidence than that of bats.
Although savanna woody encroachment has become a global phenomenon, relatively little is known about its effects on multiple dimensions and levels of savanna biodiversity. Using a combination of field surveys, a species‐level phylogeny, and functional metrics drawn from a morphological dataset, we evaluated how the progressive increase in tree cover in a fire‐suppressed savanna landscape affects the taxonomic, functional, and phylogenetic diversity of neotropical ant communities, at both the alpha and beta levels. Ants were sampled along an extensive tree cover gradient, ranging from open savannas to forests established in former savanna areas. Variation in tree cover had a significant influence on all facets of diversity at the beta level, whereas at the alpha level tree cover variation affected the taxonomic and functional but not the phylogenetic diversity of the ant communities. In general, ant community responses to variation in tree cover were largely non‐linear as differences in taxonomic alpha diversity and in the taxonomic, functional, and phylogenetic composition of the sampled communities were often much stronger at the savanna/forest transition than at any other part of the gradient. This indicates that savanna ant communities switch rapidly to an alternative state once the savanna turns into forest. Ant communities in the newly formed forest areas lacked many of the species typical of the savanna habitats, suggesting that the maintenance of a fire suppression policy is likely to result in a decrease in ant diversity and in the homogenisation of the ant fauna at the landscape scale. Variation in tree cover, resulting from woody encroachment in a fire‐suppressed savanna landscape, affected the taxonomic and functional but not the phylogenetic alpha diversity of ant communities. Dissimilarities in taxonomic, functional, and phylogenetic composition were greater at the savanna/forest transition than at any other part of the tree cover gradient. This indicates that savanna ant communities switch rapidly to an alternative state once the savanna turns into forest. Savanna woody encroachment represents a threat to open‐habitat ant specialists.
The extensive coastal forests in eastern southern Africa persist as a putative alternative stable state in an open ecosystem mosaic that includes grassland and savanna. We examine two current hypotheses of the state-transition origins of these forests: (1) facilitation—where light-demanding pioneer cohorts facilitate establishment by species that tolerate shade and whose functional traits align with forest; and (2) nucleation—where tree species of savanna origin establish on fire refugia in grassland, and where forest develops from the coalescence of these bush-clumps. We compared tree species diversity and composition on old-lands colonized by the savanna pioneer Vachellia kosiensis, with bush-clumps established on old-lands and on untransformed grassland, to determine their resemblance to intact coastal forest. The facilitation pathway in V. kosiensis woodland comprised impoverished tree assemblages differing markedly in richness, diversity, and composition from the nucleation pathway. By contrast, the bush-clump nucleation pathway comprised random assemblages of savanna species. Overlap in savanna tree composition between the bush-clump pathway and forest was notable. A suite of functional traits related to growth, reproduction and dispersal revealed that the life histories of most coastal forest tree species (~ 88%, n = 83 species) correspond with those expected from savanna. A combination of shade intolerance, multi-stemmed architecture, and growth form plasticity indicate species origins and persistence under frequent fire and variable light regimes typical of savanna environments. While these coastal woody formations satisfy the structural definition of forest, their constituents are clearly derived from savanna and questions the efficacy of their management as successional forest.
What climate actions are proposed for land-based mitigation and adaptation in Africa? What evidence supports or refutes these actions in Africa? This technical report provide answers to these questions. In this report, we reviewed several case studies to evaluate available evidence for all the major land-based climate actions. Case studies are selected for all the major land-based biomes of Africa (mangroves, forest, grassy ecosystems, and deserts) and land use types (conservation, agriculture, and urban). Climate change mitigation and adaptation actions considered include all emission reduction (ER) (ecosystem conservation and sustainable agriculture) and carbon-dioxide removal (CDR) (ecosystem management, ecosystem restoration, and agroforestry) pathways. The report particularly highlight and examine evidence across Africa’s grassy ecosystems, identifying leading case studies on climate change adaptation and mitigation. In addition, non-ecosystem-based climate actions, such as urban and desert-based climate interventions, were examined.
Understanding and mapping anthropogenic threats on species distributions is a crucial task in conservation science to identify priority areas and propose appropriate conservation strategies. Yet, there is a big challenge to quantify how these threats are associated with species distribution patterns at multiple temporal scales. For birds, existing national and global analyses have mostly focused on forest specialists and they tend to consider only one time period. Here, we evaluated spatial and temporal changes in human footprint within the distributions of Colombian birds from 1970 to 2018, and projected them into 2030. We show that widespread increases in human footprint were common within the distribution of terrestrial birds. Endemic and threatened birds have been disproportionately affected by past increases in human footprint within their distribution, and this trend will continue into the future. Several areas harboring high diversity of forest-specialists remained relatively intact up to 2018. However, our predictions show significantly higher and faster (>2% annual change) levels of transformation within these areas by 2030. Importantly, our results suggest that non-forest birds could be experiencing habitat quality declines that are just as significant as those shown for forest birds. Our results show that mitigating negative anthropogenic effects on bird habitats in Colombia requires an array of conservation strategies that range from strict habitat protection to mixed management. These analyses can serve as inputs in conservation decision tools that consider spatiotemporal variation of anthropic threats under multiple scenarios of change.
Global wind-energy development has increased exponentially in recent decades and is expected to double in capacity in Canada by 2040. Wind-farm development has significant implications for wildlife, particularly for raptors, where injury or death from turbine strikes and other cumulative effects are well documented. Minimizing conflict is important for species at risk, such as the Ferruginous Hawk (Buteo regalis), because negative impacts from wind farms may hinder conservation and recovery actions. Understanding Ferruginous Hawk habitat selection is needed to assess the potential spatial overlap with wind-farm development and make spatially explicit predictions of conflict risk. Our objectives were (1) to develop a predictive map of habitat selection by Ferruginous Hawks at the home-range scale; and (2) to identify areas of high and low potential conflict with current and future wind-energy developments, by overlaying predictive habitat maps with wind potential within the Canadian Ferruginous Hawk range. We showed that landscape composition and configuration, current industrial development, soil characteristics, and seasonal climate influenced Ferruginous Hawk home-range habitat selection. Our risk analyses identified areas at medium to very high risk of conflict with wind energy, but also large areas with low wind-energy development potential and high conservation value that would be valuable for species conservation and management. Importantly, how wind potential is measured has a strong influence on the level of risk. Our habitat model and risk assessment do not replace ground assessments, but can be used during the pre-development phase to proactively site new wind farms away from potential risk for Ferruginous Hawks.
The challenge of addressing climate change in Africa cannot be overestimated. It will require a substantial transformation of the present economic development model and multi-stakeholder partnerships to mitigate and adapt effectively to its impacts in Africa. Researchers increasingly suggest that climate change has intensified the frequency of droughts, floods, and other environmental disasters across sub-Saharan Africa. In response to the resulting array of climate induced challenges, various stakeholders are working collectively to build climate resilience in rural and urban communities and trans-continentally. This paper examines key climate resilience-building projects that have been implemented across sub-Saharan Africa through multi-stakeholder partnerships. It uses a vulnerabilities assessment approach to examine the strategic value of these projects in managing the mitigation of climate shocks and long-term environmental changes. There are still many challenges to building climate resilience in the region, but through multi-stakeholder partnerships, sub-Saharan African nations are expanding their capacity to pool resources and build collective action aimed at financing and scaling up innovative climate solutions. This paper concludes that multi-stakeholder partnerships are increasingly being utilized for pooling the economic and technical resources needed to finance and scale up innovative climate resilience projects in developing countries in Africa.
Introduction
Evolutionary traits acquired in response to one type of disturbance will potentially confer resilience to other disturbances that have similar environmental impacts, even if the biota has no evolutionary history of such disturbances. In grassy ecosystems the environmental impacts of grazing have important similarities to those of fire through the removal of grass biomass, and we hypothesise that high resilience to frequent fire confers high resilience to grazing.
Aims
We test this hypothesis by investigating the resilience of highly fire-resilient ant communities to grazing in a mesic Australian savanna, which has not historically experienced such high levels of mammalian grazing.
Methods
We sampled ants using pitfall traps at Annaburroo Station in the Australian seasonal tropics using ten plot triplets, with each triplet representing no, low and heavy grazing. Grazing has had a major impact on the basal area of perennial grasses and the cover of bare ground. We considered large (> 4 mm) ants only, which tend to be particularly sensitive to disturbance.
Results
We recorded 28 species of ‘large’ ants from 14 genera. Neither ant species richness nor overall composition varied significantly with grazing, and only one of the eight most common species responded to grazing.
Discussion
Ant communities at Annaburoo Station are highly resilient to livestock grazing. The limited number of relevant studies suggest that ant communities in Australian savannas more generally have higher resilience than those in southern rangelands where fire frequency is relatively low. This supports our hypothesis that an evolutionary history of frequent fire confers resilience to grazing. Many more studies are required, but we suggest that resilience to grazing might be related more to evolutionary history in relation to fire, a more pervasive remover of plant biomass globally, than to grazing.
Implications for insect conservation
Grazing by cattle is the dominant land-use in Australian savannas and the Australian savanna ant fauna is one of the richest on Earth; our findings of high resilience is therefore good news for insect conservation. Such good news is likely to have wide applicability to other fire-prone grassy ecosystems subject to livestock grazing.
Forest–savanna mosaics exist across all major tropical regions. Yet, the influence of environmental factors on the distribution of these mosaics is not well explored, limiting our understanding of the environmental constraints on savannas especially in Southeast Asia, where most savannas exist in mosaics. Despite clear structural and functional characteristics indicative of savannas, most SE Asian savannas continue to be classified as forest. This designation is problematic because SE Asian savannas are threatened by both fragmentation and forest‐centric management practices. By studying forest–savanna mosaics across SE Asia, we aimed to parse out how landscape mosaics of forest and savanna may be constrained by fire, climate and soil characteristics. We used remotely sensed data to characterize the distribution of tree cover and forest–savanna mosaics. Using regression models, we quantified the relative effects of precipitation, fire frequency, seasonality and soil characteristics on average tree cover and landscape patchiness. We found that low tree cover, indicative of savannas, occurs in drier, seasonal subregions that experience frequent fire. Further, our results demonstrate that fire and precipitation strongly shape landscape patchiness. Landscapes were patchiest in subregions with low precipitation and intermediate fire frequency. These results demonstrate that the environmental factors important in delineating the distribution of savannas globally shape the distribution of tree cover and landscape patchiness across SE Asia. Fire especially drives patterns of tree cover across scales. In a region where fire suppression is a common management strategy, our results suggest that further research studying vegetation response to fire and fire suppression is needed to improve management and conservation of these mosaic landscapes. More broadly, this work demonstrates a useful approach for studying the environmental drivers that influence the distribution of forest–savanna mosaics.
Grasslands have been subject to contraction and fragmentation processes worldwide, mainly due to their transformation into commercial tree plantations and agricultural lands. Identifying the remaining grasslands areas and the drivers of its fragmentation constitute an important step towards their appreciation, conservation and sustainability monitoring. The Eastern Plains of Uruguay constitute a region of recognized national and international conservation importance, but rice cultivation has spread extensively over the last 60 years, resulting in a strong transformation of its natural biomes. Our objectives were to map natural grasslands remnants in this complex landscape characterized by a high presence of different post-agricultural stages of vegetation; to quantify grassland fragmentation and its spatial variability in the landscape; and to identify the main drivers of the fragmentation process. We intersected a current supervised classification of the Eastern Plains of Uruguay (743,600 ha) with a mask of croplands from the previous ten years to discriminate grasslands remnants. We quantified the landscape fragmentation and described the relative contribution of different biophysical and anthropogenic factors in grasslands spatial configuration. Our results showed that natural grassland currently occupies only 21% of the Eastern Plains surface and it is in an advanced stage of fragmentation, comparable to that of the most historically transformed regions of the Rio de la Plata Grasslands. A few variables that determine the expansion of agriculture (large cadastral parcels size, high road network density and low topographical variation) drive the fragmentation process, relegating grassland to places with unfavorable characteristics for the development of rice cultivation.
Increases of air temperature due to global warming suggest that plants could be exposed to temperatures above their optimum range for performing specific physiological functions in the future. Declines in carbon exchange rates would lead to significant decreases in species performance, particularly in those lacking traits associated to heat tolerance. Savannas and semi-deciduous forests are ecosystems with high biological diversity, scattered throughout the Neotropical landscape, and very dynamic areas controlled by species traits. Significant increases in air temperatures can affect such areas if plant species of these forests lack heat tolerance. We performed heat tolerance assays to obtain T50 values of the photosystem II (PSII) of 30 Neotropical tree species from a savanna (15 species) and a semi-deciduous forest (15 species). Our goal was to test whether the typical savanna species are more heat-tolerant than semi-deciduous forest species. We also assessed if T50 was correlated with leaf morphological traits such as specific leaf area and leaf thickness. We found savanna tree leaves with lower specific leaf area, higher thickness, and higher T50 values than semi-deciduous forest plants (49.36 °C vs. 47.65 °C, respectively). Specific leaf area was negatively correlated to T50 values. Our findings suggest that semi-deciduous forest species would be more affected by temperature increases than savanna species. Whereas species traits play an important role in the dynamics of forest–savanna areas, savanna species would be favored under warmer temperatures.
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.
We investigated the relative influences of vegetation cover, invertebrate biomass as an index of food availability and the short-term effects of fires on the spatial variation in densities of the rodent Bolomys
lasiurus in an Amazonian savanna. Densities were evaluated in 31 plots of 4 ha distributed over an area of approximately 10×10 km. The cover of the tall grass (Trachypogon
plumosus), short grass (Paspalum
carinatum), shrubs and the extent of fire did not explain the variance in densities of Bolomys
lasiurus. Food availability alone explained about 53% of the variance in B.
lasiurus densities, and there was no significant relationship between insect abundance and vegetation structure. Fires had little short-term impact on the density of Bolomys
lasiurus in the area we studied. As the species appears to respond principally to food availability, habitat suitability models based on easily recorded vegetation-structure variables, or the frequency of disturbance by fire, may not be effective in predicting the distribution of the species within savannas.
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.
