Seqüestro de carbono e alterações bioquímicas da matéria orgânica de solos cultivados com eucalipto / Carbon sequestration and biochemical changes in organic matter of soils cultivated with eucalyptus

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The maintenance of soil organic matter (SOM) in commercial plantations of eucalyptus depends on the adoption of appropriate crop and soil management. Changes in inventories of C and the quality of the MOS caused by the use and soil management can be identified by quantifying the stocks of C in forest compartments (soil and plant) over time of cultivation, and the presence of biochemical compounds (bioindicators) derived from plant and microbial activity. This study aimed to evaluate changes in the storage of C in the soil and in plants during a rotation (seven years) of eucalyptus, conducted by coppicing and new planting (reform) wealso assessed the changes caused by the cultivation of eucalyptus compared under conventional management with that under fertirrigated system, long rotation eucalyptus (24 years), pasture, acacia and native forest on the levels of phenols derived from lignin, carbohydrates and amino sugars, the stage of decomposition of SOM, and the contribution of compounds of microbial origin for SOM in coastal plain soils of northern Espírito Santo state, Brasil. The results showed that the cultivation of eucalyptus through coppicing had the largest stock (192 t ha-1) and increment (36 t ha-1 in seven years) of C in the ecosystem (plant + litter + soil) after seven years of cultivation, followed by more productive clones in the reform system. The largest increases in C stocks were due to higher productivity, storage of C in the SOM and roots of plants. The greater apport of dry matter of litter, water and nutrients in the fertirrigated system favored the increase of organic C, total N, total carbohydrates, lignin, amino sugars in the soil, indicating greater microbial activity in the soil, of eucalyptus under the fertirrigated as compared to that under the conventional system. Also, it was noticed the wideming of the there is the extension of the relationship of amino glucosamine / muramic acid ratis in the soil of eucalyptus under system fertirrigated and in that under acacia cultivation, indicating greater contribution of fungi and other microorganisms, producers of glucosamine (actinomycetes) for the formation of the SOM. In soils under such (fertirrigated eucalyptus and acacia), the increased fungal activity can encourage aggregation of soil particles with organic compounds and increase the mean residence time of C in soil. The rotation of eucalyptus crops with acacia and the increase in the rotation length of eucalyptus favored the narrowing of the lignin / N and C / N ratios of the litter, increased the contents of lignin, carbohydrates and amino sugars of microbial origin. It was also found that the soil under eucalyptus there is more direct contribution of compounds of plant origin for the organic matter than those of microbial origin as compared to the soils under native forest, acacia and pasture. The acid / aldehyde ratio of phenols derived from lignin in the soil under short rotation eucalyptus in is lower, indicating that the SOM is in a less advanced stage of decomposition than that in soils under acacia plantation and native forest.

ASSUNTO(S)

matéria orgânica eucalyptus eucalipto aminoaçúcares amino sugars acacia ciencia do solo organic matter acácia

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