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.
Disturbances induce changes on habitat proprieties that may filter organism's functional traits thereby shaping the structure and interactions of many trophic levels. We tested if communities of ...predators with foraging traits dependent on habitat structure respond to environmental change through cascades affecting the functional traits of plants. We monitored the response of spider and plant communities to fire in South Brazilian Grasslands using pairs of burned and unburned plots. Spiders were determined to the family level and described in feeding behavioral and morphological traits measured on each individual. Life form and morphological traits were recorded for plant species. One month after fire the abundance of vegetation hunters and the mean size of the chelicera increased due to the presence of suitable feeding sites in the regrowing vegetation, but irregular web builders decreased due to the absence of microhabitats and dense foliage into which they build their webs. Six months after fire rosette-form plants with broader leaves increased, creating a favourable habitat for orb web builders which became more abundant, while graminoids and tall plants were reduced, resulting in a decrease of proper shelters and microclimate in soil surface to ground hunters which became less abundant. Hence, fire triggered changes in vegetation structure that lead both to trait-convergence and trait-divergence assembly patterns of spiders along gradients of plant biomass and functional diversity. Spider individuals occurring in more functionally diverse plant communities were more diverse in their traits probably because increased possibility of resource exploitation, following the habitat heterogeneity hypothesis. Finally, as an indication of resilience, after twelve months spider communities did not differ from those of unburned plots. Our findings show that functional traits provide a mechanistic understanding of the response of communities to environmental change, especially when more than one trophic level is considered.
Questions: Functional redundancy in assemblages may insure ecosystem processes after perturbation, potentially causing temporary or permanent local species extinctions. Yet, functional redundancy has ...only been inferred by indirect evidence or measured by methods that may not be the most appropriate. Here, we apply an existing method to measure functional redundancy, which is the fraction of species diversity not expressed by functional diversity, to assess whether functional redundancy affects community resilience after disturbance. Location: Subtropical grassland, south Brazil (30°05′46″S, 51°40′37″W). Method: Species traits and community composition were assessed in quadrats before grazing and after community recovery. Grazing intensity (G) was measured in each quadrat. We used traits linked to grazing intensity to define functional redundancy (FR) as the difference of Gini–Simpson index of species diversity (D) and Rao's quadratic entropy (Q). Also, with the same traits, we defined community functional stability (S) as the similarity between trait-based community composition before grazing and 47 and 180 d after grazing ending. Using path analysis we assessed different postulated causal models linking functional diversity (Q), functional redundancy (FR), grazing intensity (G) and community-weighted mean traits to community stability (S) under grazing. Results: Path analysis revealed the most valid causal model FR → S ← G, with a significant positive path coefficient for FR → S and a marginally significant negative one for S ← G. Since FR and G were independent in their covariation and in their effects on S, the model discriminated community resistance to grazing (the effect of G on S) from community resilience after grazing caused by functional redundancy (indicated by the effect of FR on S). Conclusion: We show that expressing functional redundancy mathematically is a useful tool for testing causal models linking diversity to community stability. The results support the conclusion that functional redundancy enhanced community resilience, therefore corroborating the insurance hypothesis.
Question
What conditions drive trait divergence during community assembly through environmental filtering, and why are some communities more trait‐diverse than others?
Methods
An individual‐based, ...stochastic, spatially explicit metacommunity simulation model produced data on species traits, spatially autocorrelated, nested, feedback‐generated environmental factors, and resulting community composition. I quantified environmentally driven alpha trait divergence using the correlation r(RE) to measure the relationship between Rao functional diversity and environmental factors. Environmentally driven beta trait divergence was assessed through the correlation r(VE), involving environmental factors and the squared residuals (V) of a second‐order polynomial regression of community‐weighted means on environmental factors (E). Permutation tests, assuming independence between traits and species composition, were used to establish the significance of r(RE) and r(VE). Additionally, the method was applied to grassland and soil data collected in plots across southern Brazil. Both simulated and real data were analysed at two spatial resolutions.
Results
Significant r(VE) correlations were frequent with factor interactions incorporated in community assembly simulations, while r(VE) correlations mostly remained within expected Type I error range when factor interactions were absent. r(VE) was stronger than r(RE) at a finer spatial resolution and weaker than r(RE) when smaller community units were combined into larger units. r(VE) for specific leaf area (SLA) was related to soil variables, likely due to their interacting effects with total vegetation cover. When small plots were aggregated into larger units, r(VE) became non‐significant, while r(RE) increased.
Conclusions
Environmentally driven trait divergence emerges during community assembly due to interactions between factors affecting the selection of individuals based on their traits. When the effects of these factors are spatially nested, including hidden, feedback‐generated ones, trait divergence arises at the beta or alpha dimension, depending on the scale of the community units. This suggests that plant‐to‐plant positive or negative interactions, which can feedback on environmental factors and generate heterogeneity, do not necessarily lead to trait divergence if these factors do not interact.
I investigate why some communities are more trait‐diverse than others along environmental gradients. Trait divergence emerges in simulated community assembly when filtering factors interact with each other and are spatially nested, including hidden, feedback‐generated ones. This implies that plant‐to‐plant interactions, providing feedback on environmental factors and creating heterogeneity, may not necessarily induce such environmentally driven trait divergence unless these factors interact.
Araucaria angustifolia (Bertol.) Kuntze is an indigenous conifer tree restricted to the southern region of South America that plays a key role in the dynamics of regional ecosystems where forest ...expansion over grasslands has been observed. Here, we evaluate the changes in intrinsic water use efficiency (iWUE) and basal area increment (BAI) of this species in response to atmospheric CO₂, temperature and precipitation over the last century. Our investigation is based on tree-rings taken from trees located in forest and grassland sites in southern Brazil. Differences in carbon isotopic composition (δ¹³C), ¹³CO₂ discrimination (Δ¹³C) and intracellular carbon concentration (Ci) are also reported. Our results indicate an age effect on Δ¹³C in forest trees during the first decades of growth. This age effect is not linked to an initial BAI suppression, suggesting the previous existence of nonforested vegetation in the forest sites. After maturity all trees show similar temporal trends in carbon isotope-derived variables and increasing iWUE, however, absolute values are significantly different between forest and grassland sites. The iWUE is higher in forest trees, indicating greater water competition or nutritional availability, relative to grassland, or both. BAI is also higher in forest trees, but it is not linked with iWUE or atmospheric CO₂. Nevertheless, in both forest and grassland sites A. angustifolia has had growth limitations corresponding to low precipitation and high temperatures observed in the 1940s.
Why Brazil needs its Legal Reserves Metzger, Jean Paul; Bustamante, Mercedes M.C.; Ferreira, Joice ...
Perspectives in ecology and conservation,
July-September 2019, 2019-07-00, 2019-07-01, Volume:
17, Issue:
3
Journal Article
Peer reviewed
Open access
Display omitted
•Legal Reserves represent almost one third of all remaining native vegetation in Brazil.•There is no solid argument, evidence or theory that support that Legal Reserve extinction will ...favor Brazil development.•The extinction of Legal Reserves will lead to a huge increase in native vegetation loss, with blatant negative consequences on biodiversity and ecosystem services provision.•Legal Reserves are a key-component for effective and less expensive nature-based solutions.•Legal Reserves should be considered as assets for the development of Brazil rather than liabilities.
Brazil's environmental legislation obliges private properties to retain a fixed proportion of their total area with native vegetation, the so-called “Legal Reserves”. Those areas represent practically one third of the country's native vegetation and are well known for their role in biodiversity protection and in the provisioning of a wide range of ecosystem services for landowners and society. Despite their relevance, this instrument has been criticized by part of the agribusiness sector and its representatives in the Brazilian Congress. The Legal Reserve requirement is said to be too restrictive and to impede the full expansion of agricultural activities, and thus to be detrimental for the development of the country. Here, we critically analyze the arguments employed in the justification of a recently proposed bill that aims to completely extinguish Legal Reserves. We demonstrate that the arguments used are mostly unsupported by data, evidence or theory, besides being based on illogical reasoning. Further, we synthesize the principal benefits of Legal Reserves, including health and economic benefits, and emphasize the importance of these reserves for water, energy, food, and climate securities, in addition to their primary function of assisting in the maintenance of biodiversity in agricultural landscapes. We also highlight that Legal Reserves are a key-component for effective and less expensive nature-based solutions, and thus should be considered as assets for the development of Brazil rather than liabilities. Based on available sound scientific evidence and agreement on their relevance, we strongly oppose any attempt to extinguish or weaken the maintenance of Brazil's Legal Reserves.
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.
SYNCSA is an R package for the analysis of metacommunities based on functional traits and phylogeny of the community components. It offers tools to calculate several matrix correlations that express ...trait-convergence assembly patterns, trait-divergence assembly patterns and phylogenetic signal in functional traits at the species pool level and at the metacommunity level.
SYNCSA is a package for the R environment, under a GPL-2 open-source license and freely available on CRAN official web server for R (http://cran.r-project.org).
vanderleidebastiani@yahoo.com.br.
The identification of a reduced dimensional representation of the data is among the main issues of exploratory multidimensional data analysis and several solutions had been proposed in the literature ...according to the method. Principal Component Analysis (PCA) is the method that has received the largest attention thus far and several identification methods—the so-called stopping rules—have been proposed, giving very different results in practice, and some comparative study has been carried out. Some inconsistencies in the previous studies led us to try to fix the distinction between signal from noise in PCA—and its limits—and propose a new testing method. This consists in the production of simulated data according to a predefined eigenvalues structure, including zero-eigenvalues. From random populations built according to several such structures, reduced-size samples were extracted and to them different levels of random normal noise were added. This controlled introduction of noise allows a clear distinction between expected signal and noise, the latter relegated to the non-zero eigenvalues in the samples corresponding to zero ones in the population. With this new method, we tested the performance of ten different stopping rules. Of every method, for every structure and every noise, both power (the ability to correctly identify the expected dimension) and type-I error (the detection of a dimension composed only by noise) have been measured, by counting the relative frequencies in which the smallest non-zero eigenvalue in the population was recognized as signal in the samples and that in which the largest zero-eigenvalue was recognized as noise, respectively. This way, the behaviour of the examined methods is clear and their comparison/evaluation is possible. The reported results show that both the generalization of the Bartlett’s test by Rencher and the Bootstrap method by Pillar result much better than all others: both are accounted for reasonable power, decreasing with noise, and very good type-I error. Thus, more than the others, these methods deserve being adopted.
Due to massive energetic investments in woody support structures, trees are subject to unique physiological, mechanical, and ecological pressures not experienced by herbaceous plants. Despite a ...wealth of studies exploring trait relationships across the entire plant kingdom, the dominant traits underpinning these unique aspects of tree form and function remain unclear. Here, by considering 18 functional traits, encompassing leaf, seed, bark, wood, crown, and root characteristics, we quantify the multidimensional relationships in tree trait expression. We find that nearly half of trait variation is captured by two axes: one reflecting leaf economics, the other reflecting tree size and competition for light. Yet these orthogonal axes reveal strong environmental convergence, exhibiting correlated responses to temperature, moisture, and elevation. By subsequently exploring multidimensional trait relationships, we show that the full dimensionality of trait space is captured by eight distinct clusters, each reflecting a unique aspect of tree form and function. Collectively, this work identifies a core set of traits needed to quantify global patterns in functional biodiversity, and it contributes to our fundamental understanding of the functioning of forests worldwide.
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