Doctorado en Biología Vegetal, Instituto de Biologia da Universidade Estadual de Campinas
Resumen
To enhance the natural regeneration of intensely anthropic forests, artificial enrichment proposes the introduction of plant species of different growth forms, absent in the area at present. Current knowledge about the initial establishment of species for enrichment still lacks studies, since the tolerance of each plant to the forest environment is extremely variable due to its self-ecology and interspecific interaction. In addition, the high cost of planting rustified seedlings tends to make the enrichment projects unviable. However, few studies evaluate the cost and effectiveness of enrichment with the use of different sizes of propagules of the same species. In order to advance the knowledge about artificial enrichment, in this study we try to answer the following questions: I. Different species of diversity present adequate performance (initial survival and growth) in different forest environments? II. Which method of enrichment (direct seeding, small and large seedlings) has a balance between cost and effectiveness? Thus, in Chapter 1 of this thesis, we evaluated the initial survival and growth of five species: Byrsonima sericea DC. (murici), Euterpe edulis Mart. (palmito-juçara), Lecythis pisonis Cambess. (sapucaia), Psidium cattleianum Sabine (araca), Parkia pendula (Willd.) Benth. ex. Walp. (visgueiro), using rustified seedlings in two forests: degraded natural forests and forest undergoing restoration, with the hypothesis that the structure of forest environments influences the initial establishment of diverse species, being favored in degraded natural forests. Our results demonstrated that the variations of the forest environment influenced the performance of the populations, especially B. sericea, E. edulis, and P. pendula, in natural forest. Contrary to expectations, the forest under restoration provides 17 times more chance of survival than the natural forests. For the species with high mortality of this study, we suggest to increase the number of individuals in the planting and to evaluate the need for replanting in the rainy season. In Chapter 2 we evaluated the balance between cost and effectiveness of enrichment, assuming that the use of smaller propagules results in low final survival, thus making the final cost higher than large seedlings. We selected six species of diversity: Allagoptera caudescens (Mart.) Kuntze (buri), B. sericea, E. edulis, L. pisonis, P. cattleianum, and P. pendula. We tested three sizes of seedlings: viable seeds, small and large seedlings. The results show that a large molt is three times more likely to survive in forests under forest undergoing restoration, compared to other sizes. The total cost of sowing was 42% lower than the small seedlings and 62% than large seedlings. For small seedlings, the total cost was 34% smaller than large seedlings. Working hours represent 58% of the final value. In this study, direct sowing enrichment was inefficient for most species, comparing with the final survival of the other methods. For small seedlings, the balance between cost and effectiveness was in species with greater accumulation of reserves in the seed. We suggest the association of two or more methods as a more effective artificial enrichment strategy and the presence of three or more pairs of leaves for the removal of small seedlings from the nursery.