High nitrous oxide (N2O) emission potential has been identified in hemiboreal forest on drained Histosols. However, the environmental factors regulating the emissions were unclear. To investigate the importance of different factors on the N2O emission, a modeling approach was accomplished, using CoupModel with Monti-Carlo based multi-criteria calibration method. The model was made to represent a forest on drained peat soil in south-west Sweden where data of fluxes combined with soil properties and plant conditions were used. The model outcome was consistent with measurements of abiotic (soil temperature, net radiation, groundwater level and soil moisture) and biotic responses (net ecosystem exchange and soil respiration). Both dynamics and magnitude of N2O emissions were well simulated compared to measurements (8.7 ± 2.1 kg N/ha/year). The performance indicators for an ensemble of accepted simulations of N2O emission dynamics and magnitudes were correlated to calibrated parameters related to soil anaerobic fraction and atmospheric nitrogen deposition (correlation coefficient, r ≥ 0.4). A weak correlation with N2O emission dynamics was also found for biotic responses (r ≥ 0.3). However, the ME of simulated and measured N2O emissions was better correlated to the ME of soil moisture (r = -0.6), and also to the ME of both the soil temperature (r = 0.53) and groundwater level (r = -0.7). Groundwater level (range from -0.8 m to -0.13 m) was identified as the most important environmental factor regulating the N2O emissions for present forest soil. Profile analysis indicated that N2O was mainly produced in the deeper layers (≥ 0.35 m) of the soil profile. The optimum soil moisture for N2O production was around 70%.

Made available in DSpace on 2014-06-11T19:28:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-21Bitstream added on 2014-06-13T20:37:33Z : No. of bitstreams: 1 teixeira_lg_me_jabo.pdf: 3324980 bytes, checksum: c588c0fe971e863b13d299ae775c6afb (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Usina São Martinho / O preparo do solo tem sido apontado como uma das práticas que causam perda adicional de carbono do solo para a atmosfera na forma de CO2, o principal gás do efeito estufa ampliado. Neste trabalho são estudados alguns aspectos da emissão de CO2 do solo de áreas agrícolas na região de Jaboticabal, SP, Brasil. Os experimentos foram realizados em duas áreas onde estudou-se o efeito do preparo do solo com arado de disco seguido de grade niveladora (convencional), escarificador de arrasto conjugado com rolo destorroador (reduzido) e enxada rotativa sobre as emissões de CO2 do solo. No experimento conduzido com a enxada rotativa, foi considerada sua aplicação sobre parcela com e sem palha de cana-de-açúcar, sendo o efeito da presença ou não de palha na superfície do solo sobre as emissões de CO2 também investigada. Já no experimento que contemplou o preparo convencional e reduzido as emissões totais indicaram que o sistema de preparo arado de disco seguido de grande niveladora foi o mais impactante, resultando em uma perda de carbono do solo próxima a 71 g m-2 (260 g CO2 m-2) em 2 semanas. Com relação à influência da palha sobre as emissões após preparo, essas foram significativas aumentando a emissão em 36% acima daquela da parcela após preparo sem palha. Os resultados apresentaram, invariavelmente, uma queda da emissão de CO2 do solo ao longo do tempo após preparo, que foi melhor modelada em um dos experimentos a partir de uma função exponencial decrescente no tempo somente, enquanto no outro experimento por uma função combinada, exponencial decrescente no tempo e dependência linear com temperatura e umidade do solo, foi a que melhor ajustou-se as variações temporais da emissão após preparo / Soil tillage has been presented as one of the practices responsible for the additional release of carbon from soil to atmosphere as CO2, the major gas of the enhanced greenhouse effect. This work investigates several aspects of soil CO2 emission in agricultural areas in Jaboticabal region, São Paulo State, Brazil. The experiments were conducted in two fields, where the effect on soil CO2 emissions was studied for tillage employing disk plow followed by offset disk harrow, chisel plow followed by clod break roller and rotary tillage. In the rotary tillage experiment, plots with and without sugarcane trash on the surface were considered, being the effect of the presence of crop residues on soil CO2 emission also evaluated. In the experiment comparing conventional and reduced tillage, total emissions indicated that the conventional tillage (disk plow followed by offset disk harrow) was the most impacting tillage system, resulting in a total carbon emission of 71 grams m-2 (260 g CO2 m-2) in 2 weeks after tillage. Concerning the influence of sugarcane trash on emissions after tillage, emissions were significant, increasing 36% over the plot without residues of the crop. In all cases, results consistently showed a decrease in soil CO2 emission in time after tillage, which was best modeled by an exponential decay in time after tillage only, for one of the experiments, while a combined function of exponential decay in time and linear dependence on temperature and soil moisture, in the other experiment, was the best for fitting the temporal variation of emission after tillage

Resumo: O preparo do solo tem sido apontado como uma das práticas que causam perda adicional de carbono do solo para a atmosfera na forma de CO2, o principal gás do efeito estufa ampliado. Neste trabalho são estudados alguns aspectos da emissão de CO2 do solo de áreas agrícolas na região de Jaboticabal, SP, Brasil. Os experimentos foram realizados em duas áreas onde estudou-se o efeito do preparo do solo com arado de disco seguido de grade niveladora (convencional), escarificador de arrasto conjugado com rolo destorroador (reduzido) e enxada rotativa sobre as emissões de CO2 do solo. No experimento conduzido com a enxada rotativa, foi considerada sua aplicação sobre parcela com e sem palha de cana-de-açúcar, sendo o efeito da presença ou não de palha na superfície do solo sobre as emissões de CO2 também investigada. Já no experimento que contemplou o preparo convencional e reduzido as emissões totais indicaram que o sistema de preparo arado de disco seguido de grande niveladora foi o mais impactante, resultando em uma perda de carbono do solo próxima a 71 g m-2 (260 g CO2 m-2) em 2 semanas. Com relação à influência da palha sobre as emissões após preparo, essas foram significativas aumentando a emissão em 36% acima daquela da parcela após preparo sem palha. Os resultados apresentaram, invariavelmente, uma queda da emissão de CO2 do solo ao longo do tempo após preparo, que foi melhor modelada em um dos experimentos a partir de uma função exponencial decrescente no tempo somente, enquanto no outro experimento por uma função combinada, exponencial decrescente no tempo e dependência linear com temperatura e umidade do solo, foi a que melhor ajustou-se as variações temporais da emissão após preparo / Abstract: Soil tillage has been presented as one of the practices responsible for the additional release of carbon from soil to atmosphere as CO2, the major gas of the enhanced greenhouse effect. This work investigates several aspects of soil CO2 emission in agricultural areas in Jaboticabal region, São Paulo State, Brazil. The experiments were conducted in two fields, where the effect on soil CO2 emissions was studied for tillage employing disk plow followed by offset disk harrow, chisel plow followed by clod break roller and rotary tillage. In the rotary tillage experiment, plots with and without sugarcane trash on the surface were considered, being the effect of the presence of crop residues on soil CO2 emission also evaluated. In the experiment comparing conventional and reduced tillage, total emissions indicated that the conventional tillage (disk plow followed by offset disk harrow) was the most impacting tillage system, resulting in a total carbon emission of 71 grams m-2 (260 g CO2 m-2) in 2 weeks after tillage. Concerning the influence of sugarcane trash on emissions after tillage, emissions were significant, increasing 36% over the plot without residues of the crop. In all cases, results consistently showed a decrease in soil CO2 emission in time after tillage, which was best modeled by an exponential decay in time after tillage only, for one of the experiments, while a combined function of exponential decay in time and linear dependence on temperature and soil moisture, in the other experiment, was the best for fitting the temporal variation of emission after tillage / Orientador: Newton La Scala Júnior / Coorientador: Afonso Lopes / Banca: José Marques Júnior / Banca: Maurício dos Santos Simões / Mestre