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Universidad Nacional de La Plata (2016)

Diversidad microbiana y materia orgánica del suelo en sistemas silvopastoriles de la Región Chaqueña

Silberman, Juan Eduardo

Titre : Diversidad microbiana y materia orgánica del suelo en sistemas silvopastoriles de la Región Chaqueña

Auteur : Silberman, Juan Eduardo

Université de soutenance : Universidad Nacional de La Plata

Grade : Doctor en Ciencias Agrarias y Forestales 2016

Résumé partiel
Silvopastoral systems are promoted as an alternative to improve the sustainability of agricultural practices have multiple benefits including trees in agro-ecosystems. But existing information about the impact of SP on soil microbial communities are very little and limited to some regions of the world that difficult its generalization and has not been reported for the Chaco region. It is known that silvopastoral systems have great potential to increase carbon sequestration in the soil. However, the factors affecting the dynamics of soil carbon fractions at regional level remain uncleared. It is therefore essential to approach the study in order to be able to provide information for making decisions to make rational use of land resources in theChaco region. The consequences of the conversion of forests to silvopastoral systems are dependent on ecological conditions of each subregion. In the sub-humid sub-region, where the present better conditions in terms of content and quality of organic matter, the effects of the implementation of silvopastoral systems are almost imperceptible, except for the decrease in catabolic potential (AWCD) and diversity of fungi soil ( TRFLP- 18S). In contrast, in the semiarid subregion, they responded to multiple parameters use change use. This study shows that silvopastoral systems low intensity conserve or improves the physical and chemical properties of the soil, a fact that is attributable to the conservation of woody vegetation. Soil bacterial communities of forests of the two subregions show some degree of tolerance induced disturbance silvopastoral land use, as significant changes in its structure after a year, which is restored to five years. In contrast, communities of soil fungi are very sensitive to changes land use, which is attributable to the lower metabolic diversity compared with bacteria and therefore a greater sensibility to the quantity and quality of litter. Silvopastoral systems impact on soil functionality primarily in the catabolic potential and functional diversity, the effect is detected five years in the subhumid and a year in the semiarid site. Additionally, in the semiarid site, other functional parameters (respiration and dehydrogenase activity), are affected by the silvopastoral use after one year. However these parameters show a tendency to restoration five years suggesting that such incorporations are able to improve soil functionality. The coverage of the most dominant tree species Chaco forest (quebracho blanco, quebracho colorado and mistol) have a differential effect on soil carbon content (mistol> quebrachos) which might be related to the differential input of litter. In addition soil under the cover of different tree species has different microbial communities in their structure (DGGE) and functional diversity. Soil microbial communities under the cover of quebracho showed preference for polymers, which is related to the higher content of phenols and tannins in the leaves of this species


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