Navegando por Autor "Rodrigues, Alice Cristina"

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On multiple drivers predicting ecosystem functioning in a tropical forest
(Universidade Federal de Viçosa, 2022-08-24) Rodrigues, Alice Cristina; Neri, Andreza Viana; http://lattes.cnpq.br/8619146758702716
Understand the relative contribution of different factors that can determine the structure and diversity of forest communities along environmental gradients and secondary succession time has been a relevant theme in contemporary ecology. Recently the impact of these environmental factors (e.g., soils, topography, and climate) on biodiversity-ecosystem function relationship has gained importance in understanding tropical forests. Topographic and edaphic gradients together with climate can influence the distribution of functional traits, and consequently, ecosystem functioning. The study of the secondary succession of tropical forests with an approach based on the relation of functional traits and environmental factors has allowed elucidating emerging patterns of the ecosystem processes, mainly of the production and storage of biomass. Thus, the community weighted mean (CWM) are the diversity metrics to test effects on aboveground biomass. This research will assess how abiotic factors and biotic factors affect the assembly of tree communities and the ecosystem functioning of the forest Atlantic in southeastern Brazil. For this, we will analyze how species richness, composition and dominance can change through edaphic-topographic-climatic gradients and time of succession in permanent plots. For this, the following hypotheses will be tested: (1) The edaphic-topographic factors and the time of succession affect the richness, composition and dominance of the species in terms of their contribution to an ecosystem process (2) the variability climate over time of succession has implications for the classification of leaf phenology groups of tree communities. Finally, (3) we propose that AGB increases with time of succession, but changes depending on environmental variability (soil and topography), and that the variation in biomass can be explained by the functional traits of the species through functional dominance (CWM) in secondary forest communities. To answer these questions, we selected three areas with different topographic conditions located in a fragment in the secondary regeneration stage in Viçosa, MG, Brazil. Each area has permanent plots of 1 ha covering a topographic gradient from the valleys to the plateau. Each permanent plot has 100 subplots of 10m x 10m. Totaling two hectares of forest and 200 subplots. In each subplot, all individuals of the living arboreal species with stem circumference showed a height of 10 cm or greater and a height of 130 cm. For each subplot, three topographic variables (elevation, slope and convexity) were measured and calculated using a total station with the aid of an engineer and surface soil samples with a depth of 0 to 10 cm to determine physical and chemical parameters. The aboveground biomass was calculated for each tree individual sampled in the subplots by an allometric equation. We selected different types of functional traits such as leaf phenology, wood density and tree diameter. Multivariate regression analyzes were performed to classify habitat types according to topographic variables and species composition. In addition, we constructed a series of models to explain the effect of potential predictor variables on the response of species richness, species composition, and ecosystem functioning. We also used machine learning to classify leaf phenology groups under the effect of environmental variables. Our study demonstrated that topographic variability, mainly elevation and convexity, determine soil fertility. These results advance our understanding that context-dependent conditions based on topography and soil properties have a high variability at a fine-scale. Furthermore, we found that different topographic conditions and successional timing affect community composition, richness, abundance and proportion of carbon-dominant species over time. We found that different topographic conditions and stand age change community composition, richness, abundance, and carbon dominant species along the late-secondary stage. This study advances our understanding of the mechanisms that drive carbon stock in tropical forests and supports the ‘mass ratio’ hypothesis. We observe that evergreen species show higher richness; meanwhile the deciduous species has a greater contribution to aboveground carbon stock. Thus, the leaf phenology groups can affect the relationships between species richness and aboveground carbon stock. For example, deciduous species are key to maintaining higher carbon stock with smaller numbers of species; meanwhile evergreen species are important to maintain a higher species richness. Thus, we presumed that the leaf phenology group's distribution could be responsible for the cobenefits (positive aboveground carbon stock and species richness relationship) in tropical forests. Using random forest, it was observed that the most influential predictor in the classification of functional groups was topography and soil properties. We emphasize that the information generated in this research can be important for the planning of forest restoration activities (passive and active) based on the high variability of environmental variables on a local scale. We also emphasize the relevance of the functional traits approach to understanding the functioning, conservation and management of tropical forests. Keywords: Biotic and abiotic factors. Cobenefits. Functional diversity. Topographical heterogeneity. Assembly community. Machine learning.
Phylogenetic structure is determined by patch size in rock outcrop vegetation on an inselberg in the northern Amazon region
(Acta Amazonica, 2018-07) Villa, Pedro Manuel; Gastauer, Markus; Martins, Sebastião Venâncio; Carrión, Juan Fernando; Campos, Prímula Viana; Heringer, Gustavo; Meira-Neto, João Augusto Alves; Rodrigues, Alice Cristina
Although inselbergs from around the world are iconic ecosystems, little is known on the underlying mechanisms of community assembly, especially in their characteristic patchy outcrop vegetation. Environmental constraints are expected to cause phylogenetic clustering when ecological niches are conserved within evolutionary lineages. We tested whether vegetation patches from rock outcrops of the Piedra La Tortuga Natural Monument, in the northern Amazon region, are phylogenetically clustered, indicating that environmental filtering is the dominant driver of community assemblage therein. We classified all patches according to their size as very small (< 1 m 2 ), small (1-4 m 2 ), medium-sized (4-8 m 2 ), and large patches (8-15 m 2 ). From each class, we randomly selected 10 patches, totalizing 40 patches covering 226 m 2 . All individuals found in the 40 isolated patches were identified to the species level. We also correlated measurements of phylogenetic community structure with patch size. We found that species from patches are restricted to the clades monocots, fabids, malvids, and lamiids. We conclude that vegetation in this rock outcrop is phylogenetically clustered. Furthermore, we found that phylogenetic turnover between pairs of patches increases with patch size, which is consistent with a scenario of higher environmental stress in smaller patches. Further research is necessary to identify nurse species in inselberg vegetation, which is pivotal for conservation and restoration of this particular ecosystem.
Phytosociology of weeds after potato cultivation (Solanum tuberosum L.) in the Venezuelan andes:an agroecological approach
(Tropical and Subtropical Agroecosystems, 2017-05-30) Villa, Pedro Manuel; Rodrigues, Alice Cristina; Márquez, Nelson; Rodrigues, Alisson Lopes; Martins, Sebastião Venâncio
Weeds represent one problem for potato cultivation in the Venezuelan Andes; however ecological studies to improve their management are limited. This study has aimed to carry out a phytosociological survey of weed community after potato cultivation in Mérida, Mérida state, Venezuela. The experiment was carried out under a completely randomized design with 20 plots (2x2 m). The weeds surveys were conducted at two month intervals, randomly selecting five plots per session during June 2006 and February 2007, to 60 days after cultivation (DDC), 120, 180, and 240 DDC. The phytosociological survey was performed involving identification and quantification of numbers of individuals the weeds in each plot. After were estimated of phytosociological parameters such as density, frequency, abundance to calculate the importance value index. A multivariate non-metric multidimensional scaling (NMDS) was performed using species abundances; also was used the unweighted pair group method with arithmetic mean (UPGMA) with presence absence data. Seventeen families, 32 genera and 35 species of weeds were identified, with the Asteraceae, Fabaceae and Poaceae families showed higher importance within the community. The most important species in the all stages were Pennisetum clandestinum, Paspalum decumbens, Desmodium adscendens, Aldama dentata, Borreria laevis, and Jaegeria hirta. Significant differences in phytosociological parameters were observed among weed species at each stage and among the different stages after potato cultivation.
Topography drive species diversity, structure and ecosystem function in tropical Atlantic forest
(Universidade Federal de Viçosa, 2018-02-20) Rodrigues, Alice Cristina; Neri, Andreza Viana; http://lattes.cnpq.br/8619146758702716
The Brazilian Atlantic forest is considered one the most important centers of diversity of vascular plants in the world providing various ecosystem services. Nevertheless, the region is also one of the most threatened tropical forests in the world, due mainly to habitat fragmentation. Comprehending the role played by environmental drivers, such as topographic variables that determine the community assembly and ecosystem functioning of tropical forests is fundamental to establishing conservation and management strategies. Nevertheless, research that study the relationship of these drivers on the biodiversity, structure and ecosystem function of Atlantic Forest tree communities remains scarce. The objective of this research was to evaluate the relative contribution of topographic drivers on forest attributes and ecosystem functioning . The study was conducted in a seasonal semi deciduous Atlantic forest fragment (at Viçosa municipality, Minas Gerais state, Brazil. We selected two sampling areas with contrasting topographic conditions (a Southeast area and a Northeast area one). Each area (100 × 100 m) was sub-divided into 100 plots of 10 × 10 m a total 200 plots (2 ha). From each plot, all trees having diameter at breast height ≥ 3.2 cm were sampled and identified to the species level. In each plot we measured three topographic variables (slope, elevation, and convexity) using a Total Station and measure the soil physicochemical properties. We performed multivariate regression tree (MRT) analysis to classify habitat types according to topographic variables and species composition. We estimated the maximum number of species required accounting for 50% of stem abundance and biomass in each area and we considered as ‘biomass hyperdominants’ and ‘stem hyperdominants’ the species that accumulated 50% of the total biomass and stems, respectively. The two study areas showed significant differences in spatial distribution of topographical variables. According to the MRT, the Southeast area was topographically less heterogeneous whith five habitat types, whereas the Northeast area was topographically more heterogeneous with seven habitas types. All species richness indices differed significantly between areas, but only in Southeast area did they also differ between habitat types. Species richness in the Northeast area is 48% higher than that of Southeast area. Structural attributes and AGB did not show differences between areas. However when analyzed at the area scale, basal area, tree height and AGB showed significant differences between low valleys and high plateaus in the Southeast area. The number of stem hyperdominants varied significantly between areas. In the Southeast area, only two species accounted for 50% of the number of stems hyperdominants, while in the Northeast area 10 species accounted for 50% of stems hyperdominants. In the Southeast area, only two species were classified as biomass hyperdominants, in the Northeast area, on the other hand, five species accumulated 50% of the AGB. Our results showed that the diversity and distribution pattern of hyperdominant species were significantly correlated with topography in both areas, and that the structural and AGB attributes vary in the topographic gradient of the Southeast area . We presume that the relative functional contributions of species may substantially vary from one species to another, regardless of their abundance. Thereby, some particularly abundant species may not in fact contribute substantially to ecosystem processes. The variation of forest attributes among habitats is probably due to the heterogeneous distribution of resources such as water and nutrients because of the great difference in elevation between the extremes of the topographic. This fact can also be correlated with the existence of a marked fine-scale edaphic gradient in soil parameters among habitats in the Southeast area. In addition, species redundancy may explain the weak relation between richness and AGB found in our study . We conclude that topography is an important driver that determines the structure, diversity and ecosystem functioning . Our study is of great importance in the analysis of impacts on tropical forests on a local scale with global repercussions, which favors the establishment of basic criteria for conservation and management.