Soil-vegetation relationships in hyperseasonal cerrado, seasonal cerrado, and wet grassland in Emas National Park (central Brazil)

In South America, the largest savanna region is the Brazilian cerrado, in which there are few areas that become waterlogged in the rainy season. However, we found a small cerrado area in which the soil is poorly drained and becomes waterlogged at the end of the rainy season, allowing the appearance of a hyperseasonal cerrado. We investigated the soil–vegetation relationships in three vegetation forms: hyperseasonal cerrado, seasonal cerrado, and wet grassland. We collected vegetation and soil samples in these three vegetation forms and submitted obtained data to a canonical correspondence analysis. Our results showed a distinction among hyperseasonal cerrado, seasonal cerrado and wet grassland, which presented different floristic compositions and species abundances. The edaphic variables best related to the hyperseasonal and seasonal cerrados were sand, base saturation, pH, and magnesium. The wet grassland was related to higher concentrations of clay, organic matter, aluminium saturation, aluminium, phosphorus, and potassium. Although it is not possible to infer causal relationships based on our results, we hypothesize that the duration of waterlogging in the hyperseasonal cerrado may not be long enough to alter most of its soil characteristics, such as organic matter, phosphorus, and potassium, but may be long enough to alter some, such as pH and base saturation, as the soils under both cerrados were more similar to one another than to the soil under the wet grassland. Since waterlogging may alter soil characteristics and since these characteristics were enough to explain the plant community variation, we may conclude that water excess—permanent or seasonal—is one of the main factors to distinguish the three vegetation forms, which presented different floristic compositions and species abundances.     

Native remnants can be sources of plants and topsoil to restore dry and wet cerrado grasslands

Neotropical grasslands have undergone intensive degradation by land conversion or biological invasion, but their restoration is still challenging. Here, we integrated two approaches to (1) assess the resilience of pristine dry and wet cerrado grasslands after removal of plants and topsoil and (2) evaluate the effectiveness of different treatments based on the material extracted from pristine grasslands to restore degraded dry and wet grasslands after pine invasion. We used old‐growth cerrado grasslands in southeastern Brazil as donor ecosystems and assessed their resilience after the removal of all plants and the upper 5‐cm soil layer. To restore both wet and dry grasslands, we tested topsoil translocation, plant transplantation, direct seeding, topsoil translocation + direct seeding, and needle layer removal. Both wet and dry grasslands were resilient to plants and topsoil removal, as evidenced by their fast recovery. The major mechanisms promoting resilience were seed germination in the wet grasslands and resprouting from underground organs in the dry grasslands. Transplantation was the most successful treatment to restore vegetation cover, species richness, and composition in both wet and dry grasslands, especially for herbaceous species. Restoration of the herbaceous layer of cerrado grasslands can be successful using natural ecosystems as donor sites without impairing their resilience in the studied scale. Improving the resilience of degraded dry and wet cerrado grasslands depends on reestablishing the condition to seed germination in the wet grasslands and reintroducing species with the ability to resprout after disturbance in the dry grasslands, attributes that explained the quick recovery of the donor ecosystems.     

Soil–vegetation relationships in cerrados under different fire frequencies

Fire is an important ecological factor that structures savannas, such as the cerrado, by selecting plant species and altering soil nutrient content. In Emas National Park, central Brazil, we compared soils under three different fire regimes and their relationship to the cerrado species they support. We collected 25 soil and vegetation samples at each site. We found differences in soil characteristics (p?<?0.05), with fertility and fire frequency positively related: in the annually burned site we found higher values of organic matter, nitrogen, and clay, whereas in the protected site we detected lower values of pH and higher values of aluminum. We also observed differences in plant community structure, with distinct floristic compositions in each site. Floristic composition was more related to sand proportion (intra-set correlation?=?0.834). Different fire frequencies increase environmental heterogeneity and beta diversity in the Brazilian cerrado.     

Patterns of taxonomic and functional diversity of termites along a tropical elevational gradient

Patterns of termite richness along elevation gradients may be related to different responses by termite functional groups to changes in environmental conditions. We investigated the distribution of termite species richness along an elevational gradient of cerrado and rupestrian grasslands in the Espinhaço Mountain Range, in Brazil. Fifty termite species were recorded, with the family Termitidae being dominant; 16 species are endemic to open areas of cerrado and 1 species, Cortaritermes rizzinii, is endemic and restricted to mountaintop grassland habitats. Termite richness declined with increasing elevation, with the main factors associated with the reduction being climactic (air temperature, air and soil humidity, and radiation) and vegetation variables. Different termite communities were found along the elevational gradient, which were also strongly influenced by changes in climate and vegetation. On the other hand, the same functional groups were present at the different elevations, although represented by different species.     

Taxonomic distinctness and diversity of a hyperseasonal savanna in central Brazil

Savannas are characterized by a sharp seasonality, in which the water shortage defines the community functioning. Hyperseasonal savannas, however, experience additionally waterlogging in the rainy season. Since waterlogging may cause local extinctions of intolerant species, we asked whether waterlogging constricts the phylogenetic structure of a hyperseasonal savanna. We studied a hyperseasonal cerrado, comparing it with a nearby seasonal cerrado, never waterlogged, in Emas National Park, central Brazil. In each vegetation form, we sampled all vascular plants by placing fifty 1-m² quadrats in five surveys. We compared the phylogenetic structure of both vegetation forms, calculating their taxonomic distinctness, taxonomic diversity, expected taxonomic distinctness, and species, genus, and family similarities. The taxonomic distinctness of both cerrados was similar and the values of similarities were high, but taxonomic diversity and expected taxonomic distinctness were lower in the hyperseasonal cerrado than in the seasonal one. Assuming that phenotypic attraction is the major process organizing local communities, the waterlogging in hyperseasonal cerrado assembles phylogenetically unrelated species that have converged on similar habitat use. As a consequence, the habitat use of hyperseasonal cerrado species is a trait widespread in the phylogeny of seasonal cerrado. Waterlogging constrains the phylogenetic structure of the hyperseasonal cerrado, especially by reducing species diversity. In more ecological terms, we can only fully assess the phylogenetic structure of a community if we consider the species abundance.     

Species Richness, Community Specialization and Soil-Vegetation Relationships of Managed Grasslands in a Geologically Heterogeneous Landscape

The increasing importance of the conservation value of managed grasslands has led to many studies exploring edaphic determinants of grassland biodiversity. Most studies, however, come either from very large areas, where biogeographical factors such as dispersal limitation may play a role, or from small, but ecologically rather uniform, regions. In addition, few studies further distinguish between plant specialists and generalists in the interpretation of the observed patterns. Here we studied species richness in semi-natural, managed grasslands in the Strá?ovské vrchy Mountains in the West Carpathians, Slovakia, where there is a matrix of different bedrocks (crystalline, sandstone, claystone, limestone) on a steep altitudinal gradient. In 89 vegetation plots we sampled the species composition of vascular plants and bryophytes and measured soil chemistry, slope angle, heat index, altitude and soil depth. We further applied Ellenberg indicator values and classified species into community specialists or generalists based on the analysis of a large phytosociological database. Using cluster analysis, we delimited five vegetation types that clearly differed in response to soil characteristics. Species richness varied between 19 and 64 species per 16?m². The main compositional gradient correlated with measured soil pH and calcium, but species richness was not significantly correlated with these factors. Soil available phosphorus was not associated with species composition as has been found elsewhere, but it did correlate negatively with species richness and the richness of specialists. Overall, species richness was largely driven by the number of specialists in the plot and particular vegetation types differed conspicuously in their number. We further found significant effects of iron, potassium and sodium on species richness, species composition and the representation of specialists and generalists. Our results provide new insights into the determinants of diversity in managed grasslands as well as to the theoretical species pool concept, explaining species richness variation along a pH gradient.     

Vegetation structure: Fine scale relationships with soil in a cerrado site

There is a lack of understanding on factors influencing the occurrence of high species heterogeneity at fine scale in the Brazilian cerrado. Soil is a major determinant of vegetation in the Brazilian cerrado and an important candidate to influence species distribution at fine scales, since soil features vary at very small distances, whereas many environmental variables are relatively homogeneous at such scale. We tested plant-soil relationships at fine scales in a cerrado site. We placed 100 contiguous 25 m² plots, where we identified all woody individuals and measured several soil features. We did partial redundancy analysis, controlling for spatial autocorrelation, to test for relationships between soil features and floristic composition. We also did multiple regressions or spatial autoregressive models to test for relationships between soil features and: (1) the abundance of the five most common species, (2) total abundance, (3) richness, (4) evenness, and (5) diversity. We found weak relationships between soil and floristic composition, richness, and total abundance, which, coupled with also weak relationship found in another study with plant available water, indicate there is no major environmental variable influencing vegetation at fine scales, but several of them interacting. Organic matter was positively related with the abundance of Myrsine umbellata and was negatively related to evenness. Although a causal relationship cannot be inferred with certainty, the dominance of Myrsine umbellata seems to be related to a positive feedback with soil.     

Are the cerrado and the seasonal forest woody floras assembled by different processes despite their spatial proximity?

Aims The Brazilian cerrado occupies land that could be occupied by seasonal forest, given current climatic conditions and their spatial proximity. Soil has been identified as one of the main determinants of cerrado and forest prevalence. We tested whether cerrado and seasonal forest woody floras were assembled by different processes. We postulated that soil nutrient availability would account for differences in the functional and phylogenetic structure of the cerrado and the seasonal forest.     

Status,future prospects,and management recommendations for alkaline fens in an agricultural landscape: A comprehensive survey

Due to agricultural intensification and cessation of traditional land use, alkaline fens of the Caricion davallianae alliance (EU-FFH 7230) are among the most endangered ecosystems in Europe. This study exhibits a vegetation analysis of these systems in Schleswig-Holstein (Northern Germany). We analyzed across three scales the effects of grazing and mowing on phytodiversity of core areas and recorded their adjacent vegetation to estimate the capability for habitat enlargement of fen species. Results revealed that species richness, evenness and number of endangered species varied insignificantly between mowing and grazing treatments, regardless of scale. The high proportion of fen species and Red-Book-listed species in core areas, along with a state-wide representation of only 2 ha of these vegetation types, underlines the need for further conservation measures. Floristic differences between grazed and mowed sites derived from the individual appearance of species within one treatment. Thus, to preserve the species pool of alkaline fens, both management strategies have to be considered. Moreover, as most small sedge reed species are low-productive and light-demanding, sufficient biomass removal of dominant tall-growing species is required. One cut per year in late summer, the traditional management, does not satisfy the requirements of target species, which is indicated by an increase of Phragmitetea species at larger plot sizes. Additionally, in grazed fens, vegetation adjacent to the core areas consisted mainly of more eutrophic wet grasslands, and, in mowed fens, mainly of reeds or woods. We recommend therefore several changes in current conservation measures that include an increase to two cuts per year in mowed fens, and stocking rates of at least 2 LU ha⁻¹ (summer grazing) or 0.7 LU ha⁻¹ (year-round grazing).     

Molecular phylogenetic diversity of bacteria associated with soil of the savanna-like Cerrado vegetation

The Brazilian savanna-like vegetation of Cerrado is rapidly being converted to pasture and agricultural fields. A 16S rDNA-based approach was taken to study the bacterial community associated with the soil of a native cerrado area (sensu stricto) and an area that has been converted to pasture. The bacterial group most abundantly identified in cerrado sensu stricto soil was the alpha-Proteobacteria while in cerrado converted to pasture the Actinobacteria were the most abundant. Rarefaction curves indicate that the species richness of cerrado sensu stricto is greater than that of cerrado converted to pasture. Furthermore, lineage-through-time plots show that the expected richness of species present in cerrado sensu stricto soil is approximately 10 times greater than that of cerrado converted to pasture.     

Brazil's neglected biome: The South Brazilian Campos

The South Brazilian grasslands occupy some 13.7 million ha and support very high levels of biodiversity. This paper reviews the current state of ecological knowledge on South Brazilian Campos and of threats and challenges associated with their conservation. The principal factors shaping grassland physiognomy and diversity are discussed, and information is presented on diversity of plant species; best estimates suggest that 3000–4000 phanerophytes occur in the South Brazilian grasslands.It is argued that, despite their high species richness, Campos vegetation is not adequately protected under current conservation policies. In the past three decades, approximately 25% of the grassland area has been lost due to land use changes, and this trend continues. However, representation of Campos grasslands in conservation units is extremely low (less than 0.5%), and the management in most of these is inadequate to preserve the grasslands, as grazing and fire are important factors for their persistence. In conclusion, the following urgent needs are identified: (1) to create more conservation units in different regions, including different grassland types throughout southern Brazil, (2) to develop proper management strategies where grasslands are subject to shrub encroachment and forest expansion, (3) to conduct research on biodiversity and ecological processes in the Campos region and (4) to raise public awareness of the value and vulnerability of this vegetation type.     

Plant species diversity in remnant grasslands on arable soils in the cropping Pampa

In order to provide a baseline for management decisions, we evaluated vegetation heterogeneity among 38 remnant grasslands located on high agronomic potential soils along a five degree-east–west transect in the cropping Pampa. This extensive region has been cultivated for well over a century, small-scale traditional forms of agriculture were progressively replaced with large-scale industrial forms and its cropped area has more than doubled in the last 25 years, threatening the maintenance of biodiversity associated to productive soils. We characterized the diversity of this grassland patches, identified its main environmental drivers and searched for factors that favor their invasion by exotic plant species. Vegetation samples were analysed through Canonical Correspondence Analysis, proportional distribution of functional groups was compared and regression models were estimated to identify variables associated with exotic species importance. Water availability, determined by climate and soil characteristics, was the main driving factor of floristic heterogeneity in these grasslands. Exotic richness, mostly of Eurasian species, increases toward the east, related to proximity to the entrance port. The functional group of C₄ native grasses seems to be responsible for biotic resistance to invasion. More than 80% of the species recorded during the first vegetation registers in 1930 are still present, while the number of exotics was seven-fold increased. Despite covering small areas as isolated stands, these are hot spots of native biodiversity and must be the object of increasing attention for conservation and restoration in order to protect the biodiversity of an extensive agricultural landscape.     

Using phenological cameras to track the green up in a cerrado savanna and its on-the-ground validation

Plant phenology has gained new importance in the context of global change research, stimulating the development of novel technologies for phenological observations. Regular digital cameras have been effectively used as three-channel imaging sensors, providing measures of leaf color change or phenological shifts in plants. We monitored a species rich Brazilian cerrado savanna to assess the reliability of digital images to detect leaf-changing patterns. Analysis was conducted by extracting color information from selected parts of the image named regions of interest (ROIs). We aimed to answer the following questions: (i) Do digital cameras capture leaf changes in cerrado savanna vegetation? (ii) Can we detect differences in phenological changes among species crowns and the cerrado community? (iii) Is the greening pattern detected for each species by digital camera validated by our on-the-ground leafing phenology (direct observation of tree leaf changes)? We analyzed daily sequences of five images per hour, taken from 6:00 to 18:00 h, recorded during the cerrado main leaf flushing season. We defined 24 ROIs in the original digital image, including total or partial regions and crowns of six plant species. Our results indicated that: (i) for the studied period, single plant species ROIs were more sensitive to changes in relative green values than the community ROIs, (ii) three leaf strategies could be depicted from the species' ROI patterns of green color change, and (iii) the greening patterns and leaf functional groups were validated by our on-the-ground phenology. We concluded that digital cameras are reliable tools to monitor high diverse tropical seasonal vegetation and it is sensitive to inter-species differences of leafing patterns.     

Mammalian Densities in a Neotropical Wetland Subject to Extreme Climatic Events

Effective management and conservation of an ecosystem requires information on species assemblages as well as reliable estimates of population sizes to plan, implement and evaluate management strategies. The Brazilian Pantanal is one of the world's largest freshwater wetlands and considered a priority landscape for wildlife conservation. It is subject to pluri-annual extreme dry and wet periods, which cause extreme flood and drought events, which strongly affect wildlife. Using the line-transect method, this study examined the distribution of densities and metabolic biomass of medium- to large-sized nonvolant mammals in forest, cerrado and floodplain landscapes, in an area with low anthropogenic influence, in the central area of the Brazilian Pantanal during a prolonged drought. Comparisons with a previous survey conducted during years of average rainfall in part of the study area suggest that population fluctuations of certain species are closely associated with water due to the drought. Results from this study showed that mammal assemblages varied between landscapes. Forested landscapes have the highest densities of mammals and are the most important in terms of relative energy consumption. In addition, at the time of the study, frugivores were found to have higher energy consumption than browser/grazers across the three landscapes; most fruits are produced in forested areas stressing their importance. By converting forested landscapes into grasslands, the intensification of ranching practices seriously threatens biodiversity and ecological processes in the region.     

Free-feeding insect herbivores along environmental gradients in Serra do Cipó: basis for a management plan

The distribution of free-feeding insect herbivores in Brazilian savanna was studied in the National Park of Serra do Cipó. Insect samples were obtained with sweep nets across cerrado (savanna), rupestrian field and altitudinal grassland vegetation from 800 to 1500 m above sea level. We found a low species richness in xeric and mesic habitats during both wet and dry seasons. Sap-sucking insects were the most abundant guild (53.4%) with Cicadellidae the most abundant family (27.2%). The hypothesis that taxon richness of free-feeding insects decreases with increasing altitude was supported in xeric habitats during the wet season only, mainly as a function of mountain summit effect. There was a decrease of 65% in the number of families occurring at 1400 and 1500 m compared with lower elevations. The exclusion of sites of rupestrian vegetation at mid-elevations from the analysis increased significantly the proportion of variance explained by the model. An examination of taxon distribution using canonical variate analysis supported this result. The hypothesis that mesic habitats are richer in species of free-feeding insect herbivores than are xeric habitats was not supported. The data indicate that plant sclerophylly may exert a strong negative influence on insect species richness, and that variation due to particular characteristics of each site strongly affected the studied guilds. The present results should inform conservation strategies for the National Park Management Plan, which is currently being developed. © Rapid Science Ltd. 1998     

Effects of different fencing regimes on community structure of degraded desert grasslands on Mu Us desert,China

Grazing is one of the major anthropogenic driving factors influencing community structure and ecological function of grasslands. Fencing has been proved to be one of the main measures for rehabilitating degraded grasslands in northwestern China. However, data from combined empirical studies on the effects of different management regimes in desert grasslands are lacking. So we selected long‐term fencing (fenced since 1991), mid‐term fencing and seasonal fencing (fenced since 2002), and adjacent free‐grazing grasslands to investigate vegetation and soil properties on southwest Mu Us desert. Our results showed that fencing increased plant cover, height, aboveground biomass (AGB) of different plant life‐form groups, Shannon–Wiener diversity index, Evenness index, Simpson index, total soil nitrogen, total soil phosphorus, and soil organic matter, but decreased plant density, species richness, Richness index, soil bulk density, water content, and pH. However, 22–24 years of long‐term complete fencing might cause redegradation of vegetation and soil nutrients, characterized by the reduction of some vegetation properties, biodiversity, total AGB, and some soil properties. Seasonal fencing with 11–13 year was more beneficial to vegetation restoration than that with completely fencing measures. Our study suggests that appropriate artificial disturbances, such as seasonal fencing (winter grazing and summer fencing), should be used after long‐term fencing in order to maintain grassland productivity and biodiversity. These findings will help to provide theoretical support for vegetation restoration and sustainable management in grassland under grazing prohibition at Mu Us desert.     

Spatial patterns along an elevation gradient in high altitude grasslands,Brazil

The Brazilian high altitude grasslands are important biodiversity centers that contribute to human well‐being far outside their boundaries. They host many vulnerable species that may go locally extinct as a result of small changes in the environment. Performing studies on local species distribution is important to guide biodiversity conservation in these areas. This study aimed to characterize a high altitude grassland plant community along an elevation gradient in southeastern Brazil. Simple logistic regression, chi‐squared tests and indicator species analysis were performed to investigate respectively whether: 1) the occurrence of botanical families was related to the altitude; 2) the richness and abundance of life forms varied along the gradient and 3) there were populations associated with specific altitudinal belts. Rubiaceae and Polygalaceae had higher occurrence probability at higher altitudes. Hemicryptophytes and chamaephytes seem to be the most favored life forms under local extreme conditions such as low temperatures and drought. The vegetation spectra varied significantly along the gradient, highlighting the major role of the turnover of habitats on a local scale for the underlying patterns of species distribution. Upper elevations encompassed a high number of indicator species, and further analyses of indicator species of high altitude grasslands will provide clues about adaptability of local species, important to consider in ecosystem management and conservation.     

The Brazilian Cerrado Vegetation and Threats to its Biodiversity

The Brazilian cerrado (savanna) biome covers 2 million km²representing23% of the area of the country. It is an ancient biome withrich biodiversity, estimated at 160000 species of plants, fungiand animals. There are about 800 species of trees and largeshrubs in the savanna vegetation and several times that numberof ground species (herbs and subshrubs). When the flora of galleryforests, mesophytic forests and other habitats occurring inthe biome are included, the total number of vascular plant speciesis estimated to reach about 10000. During the last 25 yearsmodern agriculture has been developed in the cerrado to producesoya, maize, rice, etc and enormous numbers of cattle are raisedin planted pastures. Charcoal production for the Brazilian steelindustry also causes great destruction of the cerrado. By 1994an estimated 695000 km²of cerrado (representing 35% of its area)had been converted to ‘anthropic landscape’. Thiscompares to the destruction of about 400000 km²of BrazilianAmazonian forest representing 12 or 13% of the area of thisbiome. Conservation initiatives are now desperately needed.Only 1.5% of the cerrado biome is preserved as Federal Reservesand this area needs to be at least tripled. Surveys of the vascularflora aimed at discovering biogeographic patterns are now inprogress with the objective of choosing representative areasand biodiversity ‘hot spots’ for conservation. Brazil; cerrado; biodiversity; conservation     

Exploring effective conservation networks based on multi-scale planning unit analysis. A case study of the Balsas sub-basin,Maranhão State,Brazil

Nature conservation and restoration activities require delineation of effective conservation networks. This paper presents a methodology which allows a quick evaluation of different planning options for extensive areas. We analyzed the spatial structure of remaining patches of the natural Cerrado vegetation in the Balsás sub-basin, South of Maranhão State of Brazil (about 25,590 km²) in order to understand how the remaining habitats are distributed and spatially configured. Conservation area network scenarios are based on hexagonal cells, referred to as analysis unit (AU) cells. A multi-scale analysis of 10,000 ha and 50,000 ha AU cells was set up to represent local and regional scales, respectively. For each AU at both local and regional scales we computed landscape metrics of native vegetation: NATIVE VEGETATION COVER: percentage of native vegetation cover; (NV-NP): number of patches; (NV-MSI): mean shape index. Subsequently, five different conservation and restoration strategies were defined: (a) only enforce nature conservation within legally established units; (b) target nature conservation only within the local AU landscape; (c) target regional management by combining neighboring AU; (d) management of both local landscape and region; (e) protect the legal conservation areas and promote local and regional conservation. We also generated scenarios of habitat capacity for mammals and matched these results with the different vegetation conservation scenarios. Results indicate that only 12% of the study area is well conserved and that 43% of the region is in a very critical condition. The percentage of AU cells where native vegetation conservation actions are required differ for the five conservation strategies: These results allow policy makers and other stakeholders to target the locations and extent of conservation units required. We suggest that about 45% of the sub-basin could be managed at local, regional or both scales. Regarding a mammal species diversity scenario an even higher percentage of the average habitat capacity of the selected species occurs in open cerrado and valleys areas that coincide with critical areas. The proposed multi-scale analysis unit cell approach can support the planning process of extensive areas as necessary in Brazil.     

The root to shoot ratio of trees from open- and closed-canopy cerrado in south-eastern Brazil

Background: The Brazilian savanna, or Cerrado, has been described as an ‘upside-down forest’, with higher below-ground than above-ground biomass. The cerrado vegetation, ranging from open grasslands to forests, comprises a wide range of ecological conditions and plant biomass.

Aims: To determine if and how root:shoot ratio in 102 trees differed between open- (cerrado sensu stricto) and closed-canopy cerrado (cerradão) within the same region in south-eastern Brazil.

Methods: Differences in root:shoot ratios and environmental conditions between the two cerrado types were examined, by uprooting and weighing trees from different species and functional groups.

Results: Root:shoot ratio was higher in the open than in the closed cerrado, especially among deciduous species. Root:shoot ratio in the open cerrado was lower than reported for the same cerrado type in central Brazil. Soil fertility did not differ between cerrado types, but soil water was lower and light availability was higher in the open cerrado.

Conclusions: The lower root:shoot ratio in closed than in open cerrado is probably a response to lower light and higher soil water availability, and/or to less frequent fires. Estimates of above-ground carbon storage alone significantly underestimate the carbon stock in open relative to closed cerrado.