Comportamento ecofisiológico de espécies nativas conduzidas sob diferentes níveis de sombreamento no sul do Brasil

Abstract

Deforestation in South America, especially in the Atlantic Forest, highlights the need for recovery projects. Identifying native species that can grow in certain environmental conditions helps to restore these environments. Successful establishment is linked to species survival and growth, which are influenced by the efficient use of essential resources such as water, light and nutrients. The aim of this research was to investigate the effects of shading on the survival and morphophysiological characteristics of native species, as well as to select the best planting conditions for restoration in southern Brazil. The study was divided into two chapters. Chapter I investigated the morphophysiological changes that occur in young Casearia sylvestris plants during the initial acclimatization process to natural irradiation. This experiment used young plants of the species in pots, and was conducted in a completely randomized design with three treatments: high, moderate and low irradiance. As a result, it was found that the species shows greater growth and survival, as well as better initial performance under greater light availability, and does not tolerate high shading. The variables with the highest plasticity index and which contributed most to the acclimatization process were the physiological characteristics. The aim of Chapter II was to investigate the effects of different levels of shading on the morphophysiological characteristics of the tree species Luehea divaricata, Allophylus edulis, Cupania vernalis and Myrcianthes pungens, indicating the most appropriate planting conditions for restoration practices in the extreme south of Brazil's Atlantic Forest. To this end, these species were planted in the field. The design used was randomized blocks (4) with four treatments: Full sun (PS); 18 % shading (S18); 50 % shading (S50) and 70 % shading (S70). L. divaricata showed high survival at all shading levels, greater biomass accumulation in S18 and high photosynthetic rates in PS and S18, without photoinhibitory effects, and could be part of the planting as a "filler species" as well as a "diversity species". A. edulis needs greater shading (between 18 % and 70 %), especially in the first year of planting, to avoid photoinhibitory effects and increase survival, and can be included in forest restoration programs as an enrichment species or as a "diversity species". C. vernalis and M. pungens showed high mortality in the PS planting (over 90 %) and in the other treatments, S18, S50 and S70, between 60 and 70 % mortality, so they should be introduced later, playing a role in enriching the area.