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Universidade Federal de Pernambuco (UFPE) 2013

Impacto do desmatamento da Caatinga sobre a comunidade microbiana do solo

Pereira, Vera Lúcia

Titre : Impacto do desmatamento da Caatinga sobre a comunidade microbiana do solo

Auteur : Pereira, Vera Lúcia

Université de soutenance : Universidade Federal de Pernambuco (UFPE)

Grade : Mestre em Biologia de Fungos 2013

The semiarid region of northeastern Brazil is occupied by a varied vegetation physiognomy, adapted to arid conditions, called caatinga. The Caatinga has gradually been impacted by deforestation and misuse of natural resources. Deforestation and fires are still common practices in land preparation for agriculture, which contribute to destabilizing the climate, decrease soil quality and affect the maintenance of the populations present. Although a large amount of work have been reported on monitoring of soil quality involving several environmental scenarios and management, little emphasis is given to land degradation in drylands. Whereas the action of micro-organisms in the soil can contribute to edaphic quality, we aimed to compare microbial activity in soils under native savanna and after deforestation. Soil samples were taken in the area under native caatinga (T0), and 60 (T1), 106 (T2) and 160 (T3) days of deforestation in the municipality of Petrolina, Pernambuco. Several variables were evaluated : enzymatic activity, microbial biomass carbon, microbial respiration, metabolic quotient, ergosterol content in soil and the microbial community structure by DGGE. The microbial biomass carbon (MBC) presented higher mean T3 and acid phosphatase was significantly higher at T0. With the result of the multivariate analysis three groups were formed involving the sampling periods. The first was formed by native caatinga (T0), the second for T1 and T2, and T3 was also separated. Most of data variability between sampling times was positively correlated with soil microbial biomass and activity of acid phosphatase. Positive correlation was also observed for edaphic basal respiration, ergosterol content and the activity of βglucosidase. The physical and chemical soil variables like temperature, CTC, humidity, Na, Al, K and Mg contributed to the separation of the sampling times. Humidity was crucial for the separation of T3. Soil temperature, CTC, and edaphic nutrients K and Mg influenced the formation of the group consisting of T1 and T2. The two samples taken after caatinga clearing showed similarity forming one group, however, after 160 of deforestation, the area showed differences to all sampled times, a fact attributed the better conditions offered by soil moisture due to rain. In conclusion, soil moisture is more determining to edaphic microbial activity than caatinga deforestation

Mots Clés : Deforestation, Microbial activity, Soil enzymes, Caatinga, Ergosterol, DGGE


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