干旱区生态环境知识资源中心

Nutrient availability of plants varies according to different processes governed by soil biota. In agroecosystems, human intervention may affect soil biota and therefore: it has a crucial impact on system productivity and its maintenance. Based on the above information, we assumed that sequencing bacterial functional diversity in agrosystems will be affected by plant growing stages and human activity (agricultural practice). During the study period, soil samples comprising five cores (5 cm diameter) from upper (0 to 10 cm) and deeper (10 to 20 cm) layers were collected individually from a potato field and from a control site with zero input treatment. Soil moisture, total organic carbon and bacterial functional diversity were assessed. The results obtained from the field and laboratory studies demonstrate differences between growing stages. The percentage of soil moisture content ranged between 10-12% during the study period, independent of depth, location (treatment and control) and growth stage, whereas total organic carbon (TOC) oscillated between 0.15-0.35%. Soil microbial biomass (SMB) measured in the upper layer (0 to 10 cm) increased from values of 100 mug C.g(-1) soil before planting to 190 mug C.g(-1) soil after yield harvesting, and in the deep soil layer (10 to 20 cm) a mean value of 80 mug C.g(-1) soil was obtained. Bacterial functional diversity (BFD) was evaluated using the Biolog method. Values of Shannon diversity H’ = 16.10(-2) obtained in the upper layer during the pre-planting stage decreased to H’ = 5.10(-2) after planting. At the deep layer (10 to 20 cm), similar trends to those measured in the upper layer (0 to 10 cm) were obtained, except during the harvesting and post-harvesting seasons, when maximal values of H’ = 30.10(-2) were detected. In this context, we tried to comprehend the dynamics of microbial community and the diversity of bacterial populations participating in key soil processes of agroecosystems. (C) 2001 Editions scientifiques et medicales Elsevier SAS.