Effects of Robinia pseudoacacia L. on two apulian soils

The marginal lands of Apulia region are reforested using preferentially pioneer species such as Pinus spp., Cupressus spp. and Robinia pseudoacacia L. or black locust. The aim of the study was to evaluate the effects of black locust in two reforested apulian soils and compare them to the ones of pasture soils close to the robiniets. In addition, the impacts of a Cupressus arizonica E. Greene reforestation on soil fertility has been investigated for establishing any differences with the black locust one. Black locust enriched soils with organic matter and nitrogen with respect to the corresponding pastures. However, in comparison with the cypress soils, the C and N soil enrichment was lower. That could be the result of i) different litter deposition of cypress vs. black locust; ii) drought stress of the Mediterranean basin with respect to the black locust endemic zones; iii) absence of specific symbionts of Robinia pseudoacacia L. The higher carbon content observed in the cypress soils induced a statistically greater microbial community represented by the microbial biomass carbon and the dissolved organic carbon and, although not statistically significant, the soils covered by conifer showed numerically higher concentration of ß-glucosidase, phosphatase, urease and dehydrogenase. The microbial biomass, organic matter and soil enzyme activities are some of most well known soil quality indicators (Gil-Sotres et al. 2005). Therefore, in Apulia region and in natural conditions, cypress reforestation ameliorated the soil conditions with respect to the black locust.