Bruno H. P. Rosado

Fine root biomass and root length density in a lowland and a montane tropical rain forest, SP, Brazil

Raizes finas, <2 mm de diâmetro, sao as principais responsaveis pela absorcao de agua e nutrientes e, portanto, tem um papel central nos ciclos carbono, agua e nutrientes, desde o nivel da planta ate o ecossistemico. A densidade do comprimento radicular (DCR), a biomassa de raizes finas (BRF) e a distribuicao vertical de raizes finas (DVR) no perfil do solo tem sido utilizados como bons descritores da eficiencia no uso de recursos e de estocagem de carbono no solo. Ao longo de gradientes altitudinais, a diminuicao da temperatura e da radiacao solar (dependendo da frequencia de eventos de neblina) podem reduzir as taxas de decomposicao e disponibilidade de nutrientes, o que poderia estimular o aumento do investimento das raizes finas para maximizar a absorcao de agua e nutrientes. O presente estudo avaliou a variacao sazonal de parâmetros radiculares nas florestas ombrofilas densas de Terras Baixas (FODTB) e Montana (FODM) na Mata Atlântica. A hipotese foi a de que o investimento em BRF e DCR seria maior na FODM, o que poderia maximizar a eficiencia na absorcao de recursos. A BRF e a DCR foram maiores na FODM em ambas as estacoes, especialmente na profundidade de 0-5 cm. A BRF total nos primeiros 30 cm de solo na FODTB foi significativamente menor (334 g.m-2 na estacao seca e 219 g.m-2 na chuvosa) do que na FODM (875 e 451 g.m-2 nas estacoes seca e chuvosa, respectivamente). Na profundidade de 0-5 cm em ambas as altitudes, a DCR aumentou da estacao seca para chuvosa independentemente de variacoes na BRF. Apesar da relevância da BRF para descrever processos relacionados a dinâmica de carbono, a variacao da DCR entre estacoes, independente de variacoes na BRF, indica que a DCR e um melhor descritor para estudos caracterizando o potencial de absorcao de agua e nutrientes na Floresta Atlântica. As diferencas da DCR entre altitudes dentro do contexto de uso de recursos devem ser consideradas em estudos sobre estabelecimento, crescimento de plântulas e dinâmica de populacoes na Floresta Atlântica. No nivel ecossistemico, as variacoes sazonais da DCR podem aumentar nosso entendimento sobre o funcionamento da Floresta Atlântica em termos de fluxos biogeoquimicos em um possivel cenario de mudancas climaticas e ambientais.Fine roots, <2 mm in diameter, are responsible for water and nutrient uptake and therefore have a central role in carbon, nutrient and water cycling at the plant and ecosystem level. The root length density (RLD), fine root biomass (FRB) and vertical fine root distribution (VRD) in the soil profile have been used as good descriptors of resource-use efficiency and carbon storage in the soil. Along altitudinal gradients, decreases in temperature and radiation inputs (depending on the frequency of fog events) may reduce decomposition rates and nutrient availability what might stimulate plants to invest in fine roots, increasing acquisition of resources. We evaluated the seasonal variation of fine root parameters in a Lowland and Montane forest at the Atlantic Rain Forest. We hypothesized that, due to lower decomposition rates at the Montane site, the FRB and RLD at soil surface will be higher in this altitude, which can maximize the efficiency of resource absorption. FRB and RLD were higher in the Montane forest in both seasons, especially at the 0-5 layer. At the 0-5 soil layer in both sites, RLD increased from dry to wet season independently of variations in FRB. Total FRB in the top 30 cm of the soil at the Lowland site was significantly lower (334 g.m-2 in the dry season and 219 g.m-2 in the wet season) than at the Montane forest (875 and 451 g.m-2 in the dry and wet season, respectively). In conclusion, despite the relevance of FRB to describe processes related to carbon dynamics, the variation of RLD between seasons, independently of variations in FRB, indicates that RLD is a better descriptor for studies characterizing the potential of water and nutrient uptake at the Atlantic Rain Forest. The differences in RLD between altitudes within the context of resource use should be considered in studies about plant establishment, seedling growth and population dynamics at the Atlantic Rain Forest. At the ecosystem level, RLD and it seasonal variations may improve our understanding of the Atlantic rain forest functioning in terms of the biogeochemical fluxes in a possible scenario of climate change and environmental changes.

Changes in plant functional traits and water use in Atlantic rainforest: evidence of conservative water use in spatio-temporal scales

Key messageRelationship between sap flow and functional traits changes with altitude and changes in water availability can impose a conservative water use in woody species of tropical rainforest.AbstractUsing a trait-based approach, we have identified that tropical trees are vulnerable to decreases in water availability, especially in montane areas, where higher radiation and vapor pressure deficits lead to higher water loss from trees. Changes to functional traits are useful descriptors of the response of species to variation in resource availability and environmental conditions. However, how these trait-environment relationships change with altitude remains unclear. We investigated changes in xylem sap flow along an altitudinal variation and evaluated the contribution of morphological traits to total plant water use. We hypothesize that (1) at the Montane forest, plant species will show a more conservative water use and (2) seasonally, there will be a much greater increase in conservative water use during the dry season at the Lowland site, since the climate conditions in the Montane site impose constraints to water use throughout the year. Remarkably, although water is assumed to be a non-limiting resource for Atlantic rainforest in general, we observed ecophysiological adjustments for more conservative water use in Montane forest. Our findings demonstrate that changes to water supply and demand as determined by rainfall, VPD and soil water storage can impose restrictions to water loss which differ across spatio-temporal scales. We suggest that the next steps for research in Montane forest should focus on traits related to hydraulic failure and carbon starvation to address the question whether the higher conservative water use observed at the Montane Forest translates into a higher or lower susceptibility to intensification of drought which might arise due to climate change.

Application of MALDI-MS analysis of Rainforest chemodiversity: a keystone for biodiversity conservation and sustainable use

Brazil hosts the largest proportion of global biodiversity and has demonstrated its commitment in conservation and sustainable use being a key negotiator of the Nagoya Protocol. The “Convention on Biological Diversity” (CBD) calls for actions to reduce extinction rates, something that according with different theories is of fundamental importance for the survival of life on Earth. Contrary to its position in the CBD meetings, Brazil approved a new Forest Code that will result in escalating deforestation, increasing the urgency to demonstrate the value of native species. Extractive-based activities of forest inhabitants are basically economical prospective activities upon the forest richness whose act harmfully against the environment. For centuries, such activity resulted in low profits, triggering a perverse logic that profit increase is necessarily linked to extraction increase. In the last decades, new strategies, as for instance the Sustainable Development Reserve Mamiraua, are showing that forest preservation can also be profitable. Considering the new paradigm of green economy, which now surrounds all this tensioned discussion, we are bringing to the eyesight of policy-makers results on biodiversity conservation research: combining floristic and chemodiversity surveys, using fast high throughput mass spectrometry screening (HT-MSS), to screen forest leaves for economically valued natural products. Matrix-assisted laser desorption/ionization (MALDI) ionizationbased machines are well known by their ability to furnish fast data and can be an important tool for HT-MSS. One of the aims of a long-term ongoing BIOTA/FAPESP research project at the Serra do Mar State Park is to understand ecophysiological traits of leaves, and MALDI-MS was an alternative to identify alkaloids as one of the nitrogen sink. Regarding the following main points: (1) analysis of plant attributed nitrogen fixation and (2) profitable policies for biodiversity conservation, we suggest the screening for alkaloids to be carried out using the leaves of the trees that are top ranked in population density lists within the forest sociology. In order to reach these aims, a set larger than 500 samples was screened for the occurrence of alkaloids and botanical identification. Classical chemical procedures were also applied to validate the results (Dragendorff, Mayer and Wagner assays). In this letter, we provide the first HT MALDI-MS and MALDI-MS/MS forest screening method to provide added value to local specimens of plants. Ionic liquid was used to get around known ionization problems of small molecules (< 1200Da) by avoiding isobaric ions formation by the matrix. Although, LC-ESI-MS is the common technique to screen small molecules, it is highly time consuming, since in six days, only 50 samples can be analyzed. Therefore, our strategy is based on the ability of MALDI to quickly screen a very large number of samples using an ionic liquid as matrix. Using this approach, we can screen up to 200 samples within a 3 h time-frame.

Retain or repel? Droplet volume does matter when measuring leaf wetness traits

BACKGROUND AND AIMS Leaf wetness is an important characteristic linked to a plants strategies for water acquisition, use and redistribution. A trade-off between leaf water retention (LWR) and hydrophobicity (LWH) may be expected, since a higher LWH/lower LWR may enhance photosynthesis, while the opposite combination may increase the leaf water uptake (LWU). However, the validation of the ecological meaning of both traits and the influence of droplet volume when measuring them have been largely neglected. METHODS To address these questions, LWR and LWH of 14 species were measured using droplets of between 5 and 50 μL. Furthermore, the ability of those species to perform LWU was evaluated through leaf submergence in water. The droplet-volume effect on absolute values and on species ranking for LWR and LWH was tested, as well as the influence of water droplet volume on the relationship between leaf wetness traits and LWU. KEY RESULTS Variations in droplet volume significantly affected the absolute values and the species ranking for both LWR and LWH. The expected negative correlation between leaf wetness traits was not observed, and they were not validated as a proxy for LWU. CONCLUSIONS The water droplet volume does matter when measuring leaf wetness traits. Therefore, it is necessary to standardize the methodological approach used to measure them. The use of a standard 5 μL droplet for LWH and a 50 μL droplet for LWR is proposed. It is cautioned that the validation of both traits is also needed before using them as proxies to describe responses and effects in functional approaches.

On the relative importance of CSR ecological strategies and integrative traits to explain species dominance at local scales

Summary Identifying ecological strategies based on functional traits has been one of the main focuses of studies on plant community assembly. Recently, an important and timely tool, “StrateFy”, has been proposed for detecting plant strategies across the globe according to the CSR scheme. The CSR scheme is undeniably efficient across scales, and distinct CSR strategies among species have been proposed to explain differing degrees of dominance among species. However, in a previous study we showed that dominance ranking of woody species in a resource-poor habitat (coastal sandy plain) was not explained by morphological traits commonly measured in functional approaches (such as those used to estimate CSR strategies), but by integrative traits (i.e. traits that are the result of different combinations of functional traits) more related to plant performance. Here, we used CSR analysis and StrateFy on a dataset collected on a coastal sandy plain to test the hypothesis that the dominance ranking would be compatible with the CSR strategies; i.e., that dominant species would show a greater proportion of the stress-tolerance (S%) strategy than subordinate species. Contrary to our hypothesis, all species exhibited an S/CS strategy, and the most-dominant species had neither similar values nor the highest S%. The inability of CSR analysis (as applied using StrateFy) to predict dominance ranking suggests that it can explain relative dominance when different strategies co-occur, but not in cases where dominant and subordinate plants share the same strategy. We argue that the relative importance of CSR and integrative traits for describing dominance ranking may depend on how CSR strategies are filtered in each environment. In environments where only a narrow range of strategy classes are viable, integrative traits may be more important for explaining variation in degrees of dominance. Thus, the ability of a given species to achieve dominance may depend on integrative traits resulting from multiple trait arrays, not necessarily captured by the SLA, LDMC and LA measurements that are used to calculate the relative proportions of strategies in StrateFy. This article is protected by copyright. All rights reserved.

A matter of scale and traits: a comment on ‘On the need for phylogenetic “corrections” in functional trait-based approaches’ by de Bello et al. (2015)

A recent paper by de Bello et al. (2015) reviewed the problems of imposing phylogenetic corrections in functional ecology irrespective of the research question. Although we agree with them, we do believe that the scenarios where phylogenetic corrections would be unnecessary deserve a specific look on two aspects: scale and traits. Our intention is to show that the decision to use phylogenetic corrections is not that straightforward and that a more integrative approach yields a bigger picture of processes shaping communities. Firstly, patterns at local scales may depend on regional-scale processes, which are described by biogeographical processes and thus phylogeny. Secondly, de Bello et al. suggested that if traits are conserved, phylogeny may be used as a proxy for unmeasured traits; however, the importance of phylogenetic signals of traits must be taken into account when these vary across a spectrum rather than presenting a dichotomy between conserved and convergent traits. Additionally, there may be overdispersed and underdispersed patterns of traits within the same species pool, further reinforcing that using phylogeny for unmeasured traits might lead to inaccurate predictions. Depending on the question, as discussed by de Bello et al. (2015), evaluating changes in functional trait values along environmental gradients does not preclude the use of phylogenetic corrections. However, previous studies have demonstrated that combined approaches are beneficial in reaching a more accurate precise picture of processes shaping communities species responses.

Revisiting the hypothesis for increasing liana abundance in seasonal forests: a theoretical review

BackgroundA decade ago, to address the question, “Why are lianas most abundant in seasonal tropical forests across the globe?”, the Mechanistic Explanation of Liana Global Abundance (MELGA) relied on the assumption that lianas have deeper roots than trees and are able to tap water from relatively deeper soil layers, giving them a competitive advantage during drought.ScopeWe assess whether the assumption that lianas have deep roots is corroborated by the literature. We accessed the initial MELGA paper and evaluated all papers citing it. To date, we found that two papers tested the MELGA, and only one corroborated it.ConclusionsDeeper roots in lianas are not the single mechanism explaining liana success, due to limited empirical support. Instead, we propose that while liana success in seasonal forests may relate to deep roots for some species, it should not be viewed as the exclusive result of a single trait but as the possible result of multiple traits such as hydraulic redistribution, multifocal growing, drought resilience, higher water storage capacity, and acquisitive resource syndrome. Additional hypotheses should be evaluated along with predicted changes in plant community structure. These hypotheses should stimulate research on the mechanisms driving liana success in tropical forests.