Effect of plant species on P cycle-related microorganisms associated with litter decomposition and P soil availability: implications for agroforestry management

Cutting dry deciduous forest (preserved site) for wood supply in semi-arid Brazil has led to invasion of a pioneer shrub vegetation called “Carrasco” (disturbed site), which inhibits the sprouting of native species. A land restoration project was undertaken in a cleared Carrasco area where a mixed plantation of native species and Eucalyptus spp. (experimental site) was established to preserve the forest and ensure wood supply for the local population. We considered phosphorus as a limiting soil nutrient to plant growth, and we addressed the roles of litter decomposition and microbial activity on phosphorus release in the disturbed, preserved and experimental sites. The phosphorus released from leaf litter was affected by the vegetation type, which favored specific soil microbial populations during decomposition. The Carrasco vegetation predominantly favored arbuscular mycorrhizal fungi (AMF), as shown by root colonization in the litter bags; the Eucalyptus plants favored AMF and ectomycorrhizal fungi (EM), as well as phosphate solubilizing microorganisms (PSM), and the intercropping system favored AMF and PSM groups. In contrast, the preserved site favored the PSM population. High phosphatase activity was found in the preserved and experimental sites in contrast to the Carrasco soil. Principal component analysis showed that AMF root colonization and phosphatase activity were the main parameters influencing the increase in soil phosphorus. Based on the above results, rehabilitation appeared to be underway in the experimental site, since the samples were more similar to the preserved site than to the disturbed site. This effect was attributed to Eucalyptus camaldulensis that promote the establishment of all phosphorus cycle-related microorganisms (AMF, EM and PSF). E. camaldulensis associated with mycorrhizal fungi and PSM are recommended for inclusion in agroforestry systems.