Navegando por Autor "Silva, Emily Ane Dionizio da"
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Item Influence of climate, fire and phosphorus in the dynamics of vegetation in the Amazon-Cerrado border simulated with INLAND model(Universidade Federal de Viçosa, 2015-02-12) Silva, Emily Ane Dionizio da; Costa, Marcos Heil; http://lattes.cnpq.br/5616171526303170Studies to assess the main factors responsible for the dynamics of vegetation in the Amazon such as climate and / or deforestation suggest the possibility of the Amazon rainforest may not resist a potencial change in rainfall patterns, and be converted to an ecosystem of more sparse vegetation like savanna, which gave rise to the term “Amazon Savannization”. Some of these initial studies, however, used only future climate scenarios, neglecting in their majority the fire effects and especially the effect of nutrient limitation on vegetation dynamics. Recently, in the context of climate modeling, advancements have been made in an attempt to build models that incorporate the nutritional restriction effect and the fire to assess and measure their effects on vegetation at a large scale. In this work, the main objective was to evaluate the isolated and combined effects of climate (inter annual variability and CO2), fire (F) and nutritional limitation by phosphorus (P) using the dynamic vegetation model INLAND in the transition between forest-Cerrado. The INLAND model is the first Brazilian model to simulate the vegetation dynamics incorporating these factors. The INLAND characterizes the vegetation through plant functional types, which combined differently give rise to biomes. The nutritional limitation is established through a linear function of the total phosphorus content in the soil and the maximum carboxylation capacity of Rubisco enzyme (Vmax). The Rubisco is the main enzyme responsible for regulating carboxylation rates in plants with the C3 photosynthetic mechanism type acting directly on net primary productivity (NPP) and the increase of biomass. Two regional the datasets of Vmax to be used as input data of the simulations, based on regional (PR) (field measurements) and global data (PG) of total P content in the soil. In the design of numerical experiment, 24 simulations were performed for different combinations of climate factors, P, F and CO2 were obtained. To validate the simulations, regional datasets of dry season leaf area index (LAI), and biomass were compared against simulated values by the INLAND model. The results showed that isolation, the effect of fire on the NPP in the Cerrado is positive and higher than the effects of nutritional restriction, contrary to what happens in the Amazon biome where the P acts to reduce the NPP. The CO2 when evaluated in combination with the effects of fire acted as an attenuator increasing the NPP in the transition region. With respect to the climate, the use of inter-annual variability improved representation of biomass and LAI simulated by INLAND. The LAI and biomass simulated values showed good correlation with Amazon-Cerrado observed gradient. The best representation of the vegetation composition by INLAND was found when the effects of PG+F+CO2 were combined.Item Land use change, soil physical properties and carbon stocks at a sandy soil domain of a Cerrado agriculture frontier(Universidade Federal de Viçosa, 2019-03-19) Silva, Emily Ane Dionizio daThe rapid expansion of agriculture in the Brazilian Cerrado has raised concerns about water resources conservation and about greenhouse gases emissions. The largest and most dynamic agricultural frontier of the country known as MATOPIBA is located in this biome, also the largest producer of cotton, the Western Bahia. In order to evaluate how the land use changes affect the physical and hydraulic soil properties and carbon emissions in this region, this study collected data on physical soil properties and carbon stocks for different land use, land cover types, and developed an historical reconstruction of spatial patterns of carbon stocks during the 1990-2018 period. There are seven main conclusions in this thesis: First, intensive soil use increases soil compaction and reduces the saturated hydraulic conductivity (water infiltration velocity) of the soil. Analysis of physical and hydraulic properties indicate that soils under intensive use (Irrigated Agriculture, Rainfed Agriculture and Pasture) present higher density and lower saturated hydraulic conductivity than soils under natural vegetation (Forest Formations and native Cerrado). Second, intensive land use can increase the occurrence of surface runoff events. Although soils of Western Bahia present high infiltration capacity, its intensive use decreases this capacity and increases the chances of erosion. For rainfall with intensity of 50 mm hour-1, surface runoff is expected in 62% of Irrigated areas, 41% of Pasture areas, 29% of Rainfed Agriculture areas, 15% of Forest areas and 5% of the Cerrado areas visited. For rainfall with intensity of 100 mm hour-1, it is expected that surface runoff will occur in 95% of Irrigated areas, 73% of Pasture areas, 62% of Rainfed Agriculture areas, 20% of Forest areas and 32% of Cerrado areas visited. Absence of runoff should occur only in cases of rainfall intensity of less than 10 mm hour -1 or less. Third, it is extremely likely that the replacement of Forest Formations by Pasture implies in a reduction of SCS100 by 37.3% (p-value = 0.031), and it is very likely that the replacement of Forest Formations by Rainfed Agriculture reduces SCS100 by 30.3% (p-value = 0.053). Fourth, it is likely that conversion of savanna formations to Rainfed Agriculture or Pasture decreases SCS100 by 18.2%(p-value = 0.269) and 26.4% (p-value = 0155). Fifth, it is more likely than not that the conversion of Forest Formations to Irrigated Agriculture reduces SCS100, and that conversion of Cerrado Formations to Irrigated Agriculture increases the SCS 100 by 11.1% (p-value = 0.455). Sixth, it is extremely likely that the conversion of Pasture (p-value = 0.022) or Rainfed Agriculture (p-value = 0.034) to Irrigated Agriculture increases SCS100 . Finally, it was estimated that, historically, Western Bahia lost 7.74% of the total carbon stock, with a decrease from 112 Tg-C in 1990 to 103 Tg-C in 2018. Despite the limitations and uncertainties associated with our results, it is possible to conclude that the impacts of land use change are a reality on the agricultural frontier of the Cerrado and there is an urgent need to monitor how these changes occur over time. A temporal monitoring of these effects is crucial to identify management practices and the time scale needed to change the carbon loss trend, contributing to the development of effective gas emission mitigation strategies and the development of sustainable agriculture in the region.