Brazilian Atlantic Rainforest Remnants and Mycorrhizal Symbiosis - Implications for Reforestation. A case stduy in Sergipe, Northeast Brazil

Abstract

This work presents results of several aspects of the ecology of two Atlantic rainforest remnants in the Brazilian northeast region. The region is characterized by a marked rainfall seasonality, and therefore sampling was carried out in the two periods. Sampling was also carried out in the adjacent region of each fragment, occupied by coconut plantations in both sites. Aiming to investigate the potential of native mycorrhizal species on forest regeneration, the assessment of mycorrhizal symbiosis in roots of seedling and trees was performed, as well as the analysis of the spatial distribution of inoculum. Arbuscular mycorrhizal fungi (AMF) was dominant, but AMF inoculum was not excluded from the plantation plots. In fact, spore species richness was higher than in the forest plots. AMF spore species richness and root colonization levels were higher in the upper layers of the soil, similarly to the nutrient and root biomass. Seedling recruitment was lower in the plantation than in forest plots. Seedling root mycorrhizal colonization was spatially uneven. Analysis of seedling roots from four different native tree species revealed a variable pattern of root colonization. Some of these species presented high colonization levels by dark septate endophyte. The analysis of native tree roots revealed also that ectomycorrhizal inoculum, although rare, is present in these forests, as one of the selected species, Cocoloba rosea was ectomycorrhizal. Preliminary experiments intending to test the ability of native AMF inoculum in promoting seedling growth were performed with a native legume tree species, Bowdichia virgilioides. The positive effects of AMF inoculation on plant growth, even with native mixed inoculum, suggests native inoculum can be successfully used on restoration of these deforested regions. Moreover, the high AMF colonization of the pioneer species should be managed to maximize the effects of inoculation of B. virgilioides seedlings in field conditions.