Restauração florestal: semeadura direta e efeitos do uso de inoculantes no desenvolvimento de espécies arbóreas

Abstract

There is a large need for tropical forest restoration, however there are practical restrictions that limit its implantation in large-scale. To improve direct seedling efficiency as an alternative, we have tested whether the inoculation of the seeds with microorganisms would increase establishment and growth of native trees in a restoration area. We implemented a field experiment, in 900 m2 of a protected area destined to be restored. We applied four treatments, each with 15 plots of 15 m2. We used (1) the growth-promoter bacteria Azospirillum brasilense, (2) the antagonistic fungus Trichoderma harzianum, (3) both organisms and (4) no inoculation. The species used were: which were: J. cuspidifolia, A. colubrina, E. timbouva, M. peruiferum, P. dubium, P. nitens, C. speciosa, C. fissilis, B. riedelianum and S. lycocarpum, we measured the height, and diameter of every individual of the ten native tree species sown and used mixed models to test our hypothesis. We run the analysis considering (1) all individuals; (2) established community (individuals with > 50 cm height and >5 mm diameter at soil level); (3) per species, considering all individuals. There was no effect of inoculation in the establishment or growth of the entire community, including recently sprouted individuals. The established community had higher height after nine months, but no variation in the other attributes. Among the species, P. dubium, E. timbouva, C. speciosa and B. riedelianum showed greater development in at least one attribute, when the seeds were treated with both inoculants. Peltophorum dubium was the species that best responded to inoculation, showing and increase in the number os individuals (+30%), height (+25%) and diameter at soil level (+15%), compared to the treatment without inoculation (D). The selection of tree species that potentially respond to inoculation and the use of greater diversity of microorganisms should increase the viability and efficiency of the direct seeding technique. Inoculation of seeds of native trees with a diverse community of organisms is, therefore, a promising alternative to foster ecological restoration.