THE EFFECTS OF ACACIA TORTILIS SUBSP. RADDIANA, SOIL TEXTURE AND SOIL DEPTH ON SOIL MICROBIAL AND BIOCHEMICAL CHARACTERISTICS IN ARID ZONES OF TUNISIA

The objectives of this study, conducted in Bou-Hedma National Park, were to quantify the effects of the dominant legume Acacia tortilis subsp. raddiana on soil properties. Three sites with differing soil texture were studied; the first with a gravelly-sand texture, the second with a sandy-loam texture and the third with a loam texture. At each study site, two subhabitats were distinguished, under Acacia canopies (canopied soil) and open areas (uncanopied soil). Soil organic carbon, microbial biomass and microbial coefficient were found to be significantly greater in canopied soil, compared with uncanopied soil. The lower metabolic quotient under this legume indicated a higher carbon use efficiency of microorganisms in soil. The enzyme activities (dehydrogenase, phosphatase and beta-glucosidase) expressing soil microbial activity were significantly higher under Acacia canopies. Therefore, A. raddiana planting can be considered an effective and applicable measure to restore vegetation and control desertification in arid regions. On account of the variability of soil texture in the park, three sites were studied: gravelly-sand, sandy-loam and loam soils. The highest microbial density and activity were registrated in sandy-loam soil. Microbial biomass and activity increased gradually and significantly to a maximum at 20-30 cm and subsequently decreased at 30-50 cm. The results allow us to conclude that soil texture and soil depth can play an important role in the extent of soil properties. Copyright (c) 2011 John Wiley & Sons, Ltd.