Navegando por Assunto "Umidade do solo"

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Acesso aberto (Open Access)
Efluxo de CO2 do solo em sistemas de produção de palma de óleo na Amazônia Oriental
(Universidade Federal do Pará, 2017-02-21) COSTA, Alessa Nayhara Mendanha; VASCONCELOS, Steel Silva; http://lattes.cnpq.br/0719395243841543
Tropical forest areas play an important role in the global carbon cycle. However, anthropogenic disturbances have altered the structure of the ecosystem and consequently imply in the carbon budget. To evaluate how changes in land use influence the efflux of CO2 from the soil (the main pathway of CO2 displacement in soil to atmosphere), it is possible to understand how the different types of vegetation affect the CO2 efflux of the soil, evaluating the variables that contribute to this process. A greater understanding of this influence motivates the study in different ecosystems, which seek to identify and develop practices that increase carbon stock and nutrient cycling, such as agroforestry systems (SAFs). Due to the expressive expansion of the oil palm in the Amazon region, the objective of this research was to evaluate the effects of CO2 efflux from the soil, as well as its control variables, in two oil palm production systems (conventional palm oil production systems and agroforestry systems with oil palm). The research was developed in the municipality of Tomé-Açu in areas of family farming and production. Soil CO2 efflux, soil temperature and soil gravimetric moisture were evaluated between March 2016 and November 2016. The stocks of fine roots and litter in the systems were evaluated in the period of higher precipitation (May) and lower precipitation (October). Soil CO2 efflux was higher in successional forest areas, intermediate in oil palm agroforestry systems, and lower in conventional palm oil systems. The CO2 efflux of the soil is sensitive to the "conversion" of forest areas into oil palm crops. The "soil metabolism" in the more diversified oil palm (SAF) system is more similar to that of the more ecologically integrated system (secondary forest).
Acesso aberto (Open Access)
Fluxos de CO2 do solo na Floresta Nacional de Caxiuanã, Pará, durante o experimento ESECAFLOR/LBA
(2013-03) SILVA JUNIOR, João de Athaydes; COSTA, Antonio Carlos Lôla da; AZEVEDO, Pedro Vieira de; COSTA, Rafael Ferreira da; METCALFE, Daniel B.; GONÇALVES, Paulo Henrique Lopes; BRAGA, Alan Pantoja; MALHI, Yadvinder Singh; ARAGÃO, Luiz Eduardo Oliveira e Cruz de; MEIR, Patrick
The ESECAFLOR/LBA experiment was carried out at the Caxiuanã National Forest, Pará State, and this article intends to investigate the effect of hydrological stress on the total soil respiration. Two adjacent 1 hectare plots were defined in January 2002. One plot remained in its natural conditions and was used as a control (A), while in the exclusion plot (B) plastic cover panels were installed in order to drain about 70% of the total rainfall to outside of the plot. Accumulated monthly rainfall was recorded from 2005 January to December. During 2005 the rainfall over the ECFPn was 2,211.6 mm, or 9.96% above the mean of 2,011.2 mm. The average soil moisture was 15.6±9.2 and 9.5±3.4% in the plots A and B, respectively. The average soil temperature was 25.6±0.4 and 25.7±0.5 ºC, for the A and B plots, respectively. The average soil CO2 flux was 3.46±0.44 and 3.21±0.84 μmolCO2 m-2s-1 in the A and B plots, respectively. With the exclusion of part of rain in plot B, it had a reduction of 7.23% in the soil CO2 flux (0.25 μmolCO2 m-2s-1), 39.1% in the soil humidity (6.1p.p.), and an increase of 0.39% in the soil temperature (0.1ºC). The soil moisture in parcel B was lesser than in the parcel A, due to the exclusion system of rain. However at the beginning of the year, site B undergone some changes causing the measuring values to be about the same on both areas.
Acesso aberto (Open Access)
Frações de fósforo e simbiose micorrízica em floresta secundária em resposta a disponibilidade de água e nutrientes na Amazônia oriental
(Instituto Nacional de Pesquisas da Amazônia, 2015-09) MAIA, Rodrigo da Silva; VASCONCELOS, Steel Silva; CARVALHO, Claúdio José Reis de
The availability of soil nutrients (especially phosphorus) and soil water strongly influence mycorrhizal symbiosis in forest ecosystems. The aim of this study was to evaluate the impact of litter removal and increased soil moisture availability on the spore density and mycorrhizal colonization of apogeotropic and non-apogeotropic roots of a secondary forest stand in eastern Amazonia. We determined the percentage of mycorrhizal colonization of apogeotropic and non-apogeotropic (0-10 cm soil depth) fine roots (diameter ≤ 2 mm), spore density, glomalin concentration, and soil phosphorus availability. Litter removal did not reduce soil phosphorus availability. The spore density was not affected by litter removal. In general, the variables varied on a seasonal basis, except the mycorrizal colonization of non-apogetropic roots and glomalin concentration, but were not affected by irrigation. Mechanical damage to the apogeotropic root system, inherent to the fortnightly litter removal, may have contributed to decrease mycorrhizal colonization of both apogeotropic and non-apogeotropic roots and, consequently, soil glomalin. Our results suggest that the reduction of soil cover may have negative impact over the fungus-plant symbiosis.
Acesso aberto (Open Access)
Refinamento da representação de raízes no modelo de biosfera SiB2 em área de floresta na Amazônia
(Universidade Federal do Pará, 2008) OLIVEIRA, Livia da Silva; CÂNDIDO, Luiz Antonio; http://lattes.cnpq.br/7705103746743754; CATTANIO, José Henrique; http://lattes.cnpq.br/1518769773387350
The objective of this research was to study the sensitivity of the surface flows and soil hydrology in relation to the representation and distribution of roots in the biosfera model for upland forest in the “Amazônia”. The purpose was to evaluate the impact on the representativeness of the energy surface flows, considering the Amazon region seasonality supported by intensive measures carried through in a biological reserve (Biological Reserve in “Cuieiras” River, near Manaus). Eight simulations were conducted with the model of biosphere SiB2 (Simple Biosphere Model - version 2), where each simulation scenario represented a different scenery of roots distribution in a 4.0 m depth, divided in three layers: 0.5 m , 1.5 m and 2.0 m. The roots were distributed favoring the root’s concentration in the surface layer, after that, the intermediate layer and, finally, a concentration of roots below 2.0 m deep. The simulations were conducted for the period of 2003 to 2006, emphasizing the year of 2005 to evaluate the effect of the roots representation in the energy flows (latent heat - LE and sensitive heat - H) and carbon dioxide flow (F_CO2). From the integrated analysis of simulated flows with observational data, measured in the experimental site, was possible to perceive that a reduction in the rainfall for the year of 2005, although to have been lesser in the central part of the Amazon, led the decline in soil moisture, showing that the forest passed for a considerable period of water stress. The model represented the available energy with values very close to those observed, varying seasonally in agreement with the data measured in 2005. However, LE is overestimated during the rainy season, but it shows together with the CO2 flow, the reduction with soil moisture in the dry season period, while H is overestimated by 20 W.m-2 during all the simulated period. These results show that, apparently, the consideration of surface roots are more appropriate for regions with short dry season, as characterized the study area, and deep roots should promote the modeling of the processes of the surface areas with more pronounced dry season. With the results showing that it has necessity to get more information of soil physical properties, appropriate to the region conditions, so that other refinements are effective in distinguishing the behavior of tropical forests under different regimes of water availability in the soil.
Acesso aberto (Open Access)
Variação temporal do efluxo de CO2do solo em sistemas agroflorestais com palma de óleo na Amazônia Oriental
(Instituto Nacional de Pesquisas da Amazônia, 2016-03) SILVA, Carolina Melo da; VASCONCELOS, Steel Silva; OLIVEIRA JUNIOR, Moisés Cordeiro Mourão de; KATO, Osvaldo Ryohei; SILVA JUNIOR, Alberto Cruz da; CASTELLANI, Débora Cristina
The soil carbon dioxide (CO2) efflux dynamics and its controlling factors of Amazonian agroforestry systems are poorly understood. The objective of this study was to evaluate the temporal variation of soil CO2 efflux in oil palm-based agroforestry systems and the relation between efflux and biotic (microbial and total soil carbon, microbial respiration, fine roots, individual components of agroforestry systems (AFS)) and abiotic factors (soil moisture and temperature). The measurements were taken during the less rainy (December 2010) and rainy (May 2011) periods. The soil CO2 efflux was highest during the rainy season, probably due to increased microbial activity influenced by climatic factors coupled with biotic factors. The soil CO2 efflux correlated positively with soil moisture and microbial biomass carbon and negatively with soil temperature and metabolic quotient, but these correlations were weak. The soil CO2 efflux was sensitive to the type of agroforestry system and to rainfall seasonality.
Acesso aberto (Open Access)
Variação temporal do efluxo de dióxido de carbono CO² do solo em sistemas agroflorestais com palma de óleo (Elaeis guineensis) na Amazônia Oriental
(Universidade Federal do Pará, 2013-09-20) SILVA, Carolina Melo da; VASCONCELOS, Steel Silva; http://lattes.cnpq.br/0719395243841543
The Amazon region has been subjected to continuous deforestation and expansion of land use for the implementation of activities such as cattle ranching, logging, agriculture, mining and urbanization. The burning and decomposition of forest biomass releases gases that contribute to global warming, such as carbon dioxide (CO2). In this context, there is interest in assessing the dynamics of soil CO2 efflux in the Amazon, especially in oil palm (Elaeis guineensis) agroforestry systems, due to the current large expansion of this crop in the state of Pará, which has become one of the largest producers of the country. This study aimed to investigate the dynamics of soil CO2 efflux in palm oil cultivation in agroforestry systems in the Amazon considering temporal and biotic and abiotic factors that directly influence this process. We quantified biotic factors: microbial biomass, total soil carbon, soil basal respiration, fine root and soil zone of influence of planted species, and abiotic factors: moisture and soil temperature, in two oil palm-based agroforestry systems (adubadeiras and biodiverso systems), during the dry and rainy periods. The results showed that the highest soil CO2 efflux occurred during the rainy season, probably due to increased microbial activity during this period influenced by climatic factors coupled with biotic factors. The biodiverso system showed higher soil efflux than the fertilizer adubadeiras system, probably due to increase biological activity in former system. The soil CO2 efflux showed no strong correlation with the tested variables. It was concluded that the soil CO2 efflux was influenced by rainfall seasonality only. The fact that the systems were be too young (~3 yr-old) may represent the main factor for a lack of stronger relationship of soil CO2 efflux and the variables analyzed.