Grazing exclusion may lead to biodiversity loss and homogenization of naturally heterogeneous and species-rich grassland ecosystems, and these effects may cascade to higher trophic levels and ...ecosystem properties. Although grazing exclusion has been studied elsewhere, the consequences of alleviating the disturbance regime in grassland ecosystems remain unclear. In this paper, we present results of the first five years of an experiment in native grasslands of southern Brazil. Using a randomized block experimental design, we examined the effects of three grazing treatments on plant and arthropod communities: (i) deferred grazing (i.e., intermittent grazing), (ii) grazing exclusion and (iii) a control under traditional continuous grazing, which were applied to 70 x 70 m experimental plots, in six regionally distributed blocks. We evaluated plant community responses regarding taxonomic and functional diversity (life-forms) in separate spatial components: alpha (1 x 1 m subplots), beta, and gamma (70 x 70 m plots), as well as the cascading effects on arthropod high-taxa. By estimating effect sizes (treatments vs. control) by bootstrap resampling, both deferred grazing and grazing exclusion mostly increased vegetation height, plant biomass and standing dead biomass. The effect of grazing exclusion on plant taxonomic diversity was negative. Conversely, deferred grazing increased plant taxonomic diversity, but both treatments reduced plant functional diversity. Reduced grazing pressure in both treatments promoted the break of dominance by prostrate species, followed by fast homogenization of vegetation structure towards dominance of ligneous and erect species. These changes in the plant community led to increases in high-taxa richness and abundance of vegetation-dwelling arthropod groups under both treatments, but had no detectable effects on epigeic arthropods. Our results indicate that decision-making regarding the conservation of southern Brazil grasslands should include both intensive and alleviated levels of grazing management, but not complete grazing exclusion, to maximize conservation results when considering plant and arthropod communities.
1. Habitat loss is one of the greatest threats to biodiversity, exerting negative effects on the ecological viability of natural vegetation remnants. The south Brazilian grasslands belong to one of ...the largest temperate grassland regions in the world, but have lost 50% of their natural extent in the past 35 years. To date, there is no empirical evidence for the effects of habitat loss on these grasslands' biological diversity, undermining their conservation. 2. Using data from a large-scale biodiversity survey, we asked if local plant communities respond to levels of habitat loss representative of the entire region (≤50%). Vegetation in grassland remnants was sampled in 24 landscapes at three localities each, using nine plots per locality. To investigate whether species losses were a consequence of stochastic or nonrandom local extinctions and whether plant communities became more homogenized, we evaluated species richness, beta-diversity components (spatial turnover and nestedness), and phylogenetic diversity, in respect to landscape change. In part of the landscapes, arthropods were sampled to investigate if loss of plant diversity had a cascading effect on other trophic levels. We evaluated generic richness of ants, an omnivore group with high levels of plant associations, in respect to a plant community's phylogenetic diversity. 3. Local plant communities in landscapes with less grassland cover had fewer species, less spatial turnover, increased nestedness and lower phylogenetic diversity. Our results suggest that the observed species loss can be linked to taxonomic homogenization and is nonrandom, decreasing evolutionary diversity within the community. Furthermore, ant richness declined by 50% in plant communities with the lowest phylogenetic diversity, suggesting that effects of habitat loss propagate to higher trophic levels. 4. Policy implications. We conclude that the biological diversity of south Brazilian grasslands, at the producer and consumer level, is at risk under the current rate of land-use conversion, even at habitat losses below 50%. To avoid substantial biodiversity loss, conservation and more restrictive policies for conversion of native grasslands to different land uses in South Brazil are urgently needed.
Brazil's neglected biome: The South Brazilian Campos Overbeck, Gerhard E.; Müller, Sandra C.; Fidelis, Alessandra ...
Perspectives in plant ecology, evolution and systematics,
12/2007, Volume:
9, Issue:
2
Journal Article
Peer reviewed
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.
Aims
We offer a first classification of South Brazilian grasslands (Campos Sulinos) based on quantitative vegetation data and describing grassland types in terms of dominant and indicator species.
...Location
South Brazilian grasslands (Paraná, Santa Catarina, Rio Grande do Sul states).
Methods
We described vegetation plots in 167 sampling units throughout the region using a stratified nested design, totalizing 1,502 1 m² quadrats. We classified vegetation using cluster analysis based on Bray–Curtis dissimilarities, establishing three vegetation types and ten subtypes. We conducted indicator species analysis within the resulting subtypes, and for all possible combinations of subtypes.
Results
In the cluster analyses, a clear separation of poorly drained grasslands from the drier sites appeared. Further, a clear distinction between grasslands in the South Brazilian highland region, situated in the Atlantic Forest biome, and the grasslands of the Pampa biome, to the south, emerged, reflecting climatic and management differences. Highland grasslands showed lower species cover dominance, while in the Pampa, Paspalum notatum clearly was the most important species and the abundance of exotic species was higher.
Conclusions
Our study provides the first classification of South Brazilian grasslands based on quantitative vegetation data recorded in a standardized sampling design. The data support the division of grasslands into the main phytogeographic units of the region (Brazilian biome classification). Grasslands in these two regions also differ in terms of species dominance pattern (higher dominance in Pampa grasslands, likely also due to higher grazing levels) and in terms of conservation state (low presence of exotic species in highland grasslands). Our results are important for conservation policies, which can now consider the presence of different grassland types in different region, but more data will be necessary for a more detailed classification that considers different abiotic features in more detail.
Subtropical mesic to poorly drained grassland communities from South Brazil were classified for the first time based on quantitative data. Three vegetation types and ten subtypes corresponding to the mesic grasslands in the highland region and the mesic and humid grasslands in the Pampa biome were found. Grassland subtypes differ in terms of species dominance pattern and conservation state.
Abstract
Rhynchospora is one of the most species-rich genera of Cyperaceae, comprising c. 400 species in 28 sections. Rhyncospora section Tenues is one of the largest sections and one of the most ...problematic. Because it is morphologically similar to sections Laevinuces, Luzuliformes and Spermodontes, the characters traditionally used to distinguish section Tenues cannot be reliably used to place species into one of these four sections. These four sections are included in the Psilocarya group of Rhynchospora subgenus Rhynchospora with sections Psilocarya and Dichromena. Previous molecular studies of Rhynchospora indicate that species of the Psilocarya group form a clade and are sister to at least some species of the sections being studied here. Since only 11 of the estimated 41 species in these four sections were included in earlier phylogenetic studies, the relationships among these sections remain unclear. To elucidate these relationships, we conducted a molecular phylogenetic analysis for Rhynchospora, based on plastid trnL-F and nuclear ETS and ITS markers, emphasizing species in these four sections. Results show that sections Laevinuces, Spermodontes and Tenues are individually not monophyletic but, grouped together, form a well-supported clade, Rhynchospora section Tenues s.l. Rhynchospora section Luzuliformes is monophyletic but is not a sister clade of section Tenues.
The level of endemism at a site may indicate species richness of the site. Nevertheless, assessing endemism levels in taxonomic groups such as plants may be difficult because the species richness of ...plants is high relative to species richness of other taxonomic groups (e.g., vertebrates). A major problem in determining whether plant species are endemic is the lack of standardization of the geographic extent of endemism: species are considered endemic to, for example, countries, continents, or states. We compiled a history of the concept of endemism as it applies to plants. The application of the concept to geographic distribution dates from the 19th century, when European explorers discovered many taxa exclusive to regions outside Europe. Two types of endemism, paleoendemism and neoendemism, were then acknowledged, according to evolutionary age, and these categories are still in use. In the 20th century, most of the research on endemism focused on explaining range restriction on the basis of cytological data, edaphic and geological factors, and phylogeny. This research led to a vast number of concepts, of which only edaphic endemism remains relatively well accepted. More recently, researchers suggest that competition may determine endemism in some cases. We suggest that plants be labeled as endemic only if their distribution occurs in a distinct ecological unit, such as a biome. On the basis of a literature review of the factors that cause range restriction, we categorized endemic taxa as paleoendemic, neoendemic, edaphically endemic, or suppressed endemic. For example, Schlechtendalia luzulifolia, is a rare forb that is a paleoendemic species of the granite and sandstone-based grasslands of the Pampa. Levels of endemism in southern Brazilian grasslands are poorly known. We emphasize the importance of recognizing these grasslands as a single transnational biome so that levels of endemism of species therein can be assessed correctly. El nivel de endemismo de un sitio puede indicar la riqueza de especies del sitio. Sin embargo, la evaluación de niveles de endemismo en grupos taxonómicos como las plantas puede ser difícil porque la riqueza de especies de plantas es alta en relación con la riqueza de especies de otros grupos taxonómicos (e.g., vertebrados). Un problema importante para determinar si las plantas son endémicas es la falta de estandarización de la extensión geográfica del endemismo: por ejemplo, las especies son consideradas endémicas de países, continentes o estados. Compilamos una historia del concepto de endemismo aplicado a plantas. La aplicación del concepto a la distribución geográfica data del siglo 19, cuando exploradores europeos descubrieron muchos taxa exclusivos de regiones fuera de Europa. Se reconocían dos tipos de endemismo, paleonedemismo y neoendemismo, de acuerdo con la edad evolutiva, y estas categorías aun son utilizadas. En el siglo 20, la mayor parte de la investigación sobre endemismo se enfocó en la explicación de la restricción de rango de distribución con base en datos citológicos, factores edáficos y geológicos y filogenia. Esta investigación condujo a un vasto número de conceptos, de los cuales solo el endemismo edáfico permanece relativamente bien aceptado. Más recientemente, los investigadores sugieren que la competencia puede determinar el endemismo en algunos casos. Sugerimos que las plantas deben ser consideradas endémicas solo si su distribución ocurre en una unidad ecológica diferente, como un bioma. Con base en la revisión de literatura sobre los factores que causan la restricción de rango, clasificamos a los taxa endémicos como paleoendémico, neoendémico, endémica edáfica o endémica suprimida. Por ejemplo, Schlechtendalia luzulifolia una hierba rara que es una especie paleoendémica de los pastizales basados en granito y caliza de la Pampa. Los niveles de endemismo en los pastizales del sur de Brasil no son bien conocidos. Enfatizamos la importancia de reconocer a estos pastizales como un solo bioma transnacional para que los niveles de endemismo puedan ser evaluados correctamente.
Rhynchospora sect. Luzuliformis is one of the 28 sections of the genus proposed by Kükenthal, the last taxonomist to have studied the section. It has three species and two varieties, and most species ...are found in open areas of the southern grasslands of South America. Species were studied in the field and in herbaria, and literature was reviewed. As main results we highlight the new specific status and new name, Rhynchospora boeckeleriana, the designation of two neotypes and three lectotypes, and a new record for Brazil, R. praecincta. Full descriptions of the four species are provided, as well as a key to distinguish the species of section Luzuliformes.
Intra- and interspecific trait variation express the response of plants dealing with different environmental conditions. We measured root and leaf traits on 14 species of calcareous grasslands in a ...restoration experiment. We aimed at identifying intraspecific differences in biomass allocation and functional plant traits under contrasting soil conditions by comparing plants growing in ancient grassland and two restored grasslands on ex-arable land, one of them with topsoil removal. Relative importance of trait variation within and among species, and among site was assessed by variance partitioning. Interspecific variation was more important than intraspecific variation, but the contribution of the latter to total variation was considerable, especially for specific leaf area. Changes in soil properties due to topsoil removal resulted in lower values of plant height, specific leaf area and specific root length compared to the control (ancient grassland). Soil fertility found in the treatment without top soil removal did not affect plant plasticity compared to the control. The study species showed two allocation strategies in relation to resource stress, while the responses of individual traits to the soil treatments were consistent across species. We conclude that caution must be taken when using mean trait values for plastic species or when working with environmental gradients.
Intra- und interspezifische Variation von Pflanzeneigenschaften (‚plant traits‘) ist Ausdruck der Reaktion von Pflanzenarten auf unterschiedliche Standortverhältnisse. Kontrastierende Standortbedingungen eines Renaturierungsexperimentes bildeten einen geeigneten Rahmen für eine Untersuchung der Wurzel- und Blatteigenschaften von 14 Kalkmagerrasenarten. Die Studie fokussierte auf Unterschiede in der Biomasse-Allokation und ausgewählten Pflanzenmerkmalen zwischen Individuen, die auf einem erhaltenen (historischen) Kalkmagerrasen wuchsen, und solchen auf zwei renaturierten Flächen (mit oder ohne Oberbodenabtrag) mit Acker als Vornutzung. Untersucht wurde die relative Variation der Pflanzeneigenschaften zwischen Individuen, Arten und Untersuchungsflächen. Die interspezifische Variation war stärker als die intraspezische, besonders bei der spezifischen Blattfläche. Oberbodenabtrag führte zu geringerer Pflanzenhöhe, und niedrigeren Werten für spezifische Blattfläche und spezifische Wurzellänge verglichen mit dem historischen Magerrasen. Die höheren Nährstoffgehalte der Ackerflächen ohne Bodenabtrag beeinflussten die Plastizität der Pflanzenarten nicht. Die Magerrasenarten zeigten zwei unterschiedliche Allokationsstrategien als Reaktion auf ungünstige Bodenverhältnisse, während die Veränderungen der einzelnen Pflanzeneigenschaften bei allen Arten ähnlich ausfielen. Die Ergebnisse legen nahe, dass die Verwendung von gemittelten Werten von Pflanzeneigenschaften bei plastischen Arten entlang von Umweltgradienten problematisch ist.
Land degradation is a complex concept that integrates different aspects, including changes in soil conditions, biodiversity, productivity and socio-economic implications, compared to a reference ...state. We propose a new conceptual framework to analyze degradation stages and restoration thresholds in species-rich natural grasslands. The framework integrates different degradation stages with their respective thresholds and describes key processes of land-use change that lead to certain stages and thresholds. Specifically, we discuss two scenarios of grassland degradation, i.e. unsuitable grassland management and complete change of land use, sometimes followed by spontaneous recovery. We illustrate the framework with the case of south Brazilian grasslands, which are rich in biodiversity, but suffer from a series of degradation processes and are poorly considered from a conservation perspective. The conceptual framework can be applied by studies on degradation and restorability of tropical and subtropical grasslands after changes in management or transition to other land use; it will facilitate decisions on alternative management and conservation.
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