Influência de atributos físicos e hídricos do solo na dinâmica do carbono orgânico sob diferentes coberturas vegetais na Amazônia central
In the present study, successive sampling of soil layers and soil solution were carried out, together with measurements of soil water contents, during 4 years, to evaluate the contents of carbon (C) and nutrients in soil. The study areas, representing four different vegetation cover, were: a) prima...
| Autor principal: | Marques, Jean Dalmo de Oliveira |
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| Grau: | Tese |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/12211 http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4799808U8 |
| Resumo: |
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In the present study, successive sampling of soil layers and soil solution were carried out, together with measurements of soil water contents, during 4 years, to evaluate the contents of
carbon (C) and nutrients in soil. The study areas, representing four different vegetation cover, were: a) primary forest (with plots on three distinct topographic positions: plateau, slope, and
valley); b) active old pasture; c) second growth; and, d) a 14-17 year old Agroforestry system (AFS). A total of 500 samples of bulk soil and soil solution was collected up to a 2-m depth, for analyzing C and nutrients. Soil profiles were excavated, one for each type of vegetation cover, and topographic position (in primary forest). Additionally, soil cores were taken around the soil profiles, at each stage of the study, to evaluate the degree of heterogeneity of the soil. Soil organic carbon (SOC) was fractionated in the samples taken form the depths 0-5 cm, 5-10 cm, 10-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, 80-100 cm, 100-160 cm, and 160-200 cm. The potential of carbon emission of the ground in each studied ecosystem was quantified, comparing the differences enters environments.Tests of water infiltration and soil permeability
were made for the surface layer, evaluating their interactions with the dissolved organic carbon (DOC). Soil physical attributes such as texture, bulk density, aggregate stability, and
macroporosity do intefere on the flow of soil carbon, favoring increases in the amounts and quality of soil C in case that they are not modified. There were spacial and temporal variations
in DOC between horizons, decreasing in depth, directly influenced by topographical variation and soil physical attributes. The precipitation events, infiltration rates and soil permeability can induce a fast movement of the water throughout the macropores surpassing the contact of
organic and inorganic solutes with the soil matrix, thus reducing the sorptive retention. The results demonstrated to greaters concentrations of COD in the following sequence: agroflorestry system (AFS) > second growth > forest > pasture, demonstrating the capacity of the SAF and second growth in recouping and/or send carbon in the solution of the ground. In
the surface of four studied environments, around 60% of present carbon is associated the fractions labeis of the ground, whereas in depth 70% of carbon is restrained in the heavy
fractions. The average of losses of total carbon in the lábil fraction in the pasture area when compared with the forest, second growth and AFS was of 38.82 Mgha-1 of C 39.54 Mgha-1 of C e 36.18 Mgha-1 of C, respectively; supposed that the conversion of forest for the establishment of AFS or second growth liberates little carbon for the atmosphere. In case of
land use changes in areas of primary forest, the ground of the plateau, slope and valley had emitted for the atmosphere, in the different fractions, around 112.71 Mgha-1 of C (FLL), 2.60
Mgha-1 of C (FLI), 28.34 Mgha-1 of C (sand), 56.17 Mgha-1 of C (clay) and 40.61 Mgha-1 of C (silte), potencializando 240.43 Mgha-1 of C. The high total stocks of soil C, especially in
shallow layers of valley forests, stresses the need of extreme precaution towards the conversion of tropical forests into other systems. Exposing this to the effects of deforestation,
besides the effect of climate changes can cause significant losses of this carbon stored in soil to the atmosphere. |