Traços funcionais como preditores da similaridade funcional entre sub-bosques de florestas estacionais semideciduais: subsídios para a conservação destes ecossistemas

Abstract

CHAPTER 1: The understory environmental variables guide to a very specific flora to this stratum, and thus a distinct functional structure from the rest of the community. This study evaluated the floristic diversity, leaf phenology and dispersal of tree species in nine understories of semideciduous forests in different stages of disturbances. Was tested the hypothesis that environmental changes of this stratum, with the increase in disturbance intensity, directly affects the floristic diversity and understory functional structure. Phytosociological parameters were evaluated to species and families of each understory and to all nine understory altogether. Floristic similarity was evaluated between the nine understories, and among understories under the same disturbance intensity. The leaf phenology and dispersal syndrome of species were compared between the understory and the upper strata in each area and among the nine understories. Myrtaceae, Rubiaceae, Celastraceae, and Meliaceae Siparunaceae were the five most important families. The five most representative species were Cheiloclinium cognatum, Cordieria sessilis Siparuna guianensis, Siphoneugena densiflora and Trichilia catigua. The floristic similarity revealed a higher floristic similarity between the understory under the same disturbance intensity. Some species and families were indicative of disturbance to the understory. Comparisons about leaf phenology and dispersion syndrome demonstrated a very low proportion of deciduous and anemochoric species in the understory compared to the upper layers. Was observed a significant increase in deciduous species proportion to the more disturbed forests but not to the anemochory. Even with very distinct floristic diversity, was possible to establish functional patterns to leaf phenology and dispersal syndrome to the understory, and then can be use as a parameter in the classification of successional stages of seasonal forests. CHAPTER 2: The understory of forests is a shaded environment, with species which have functional traits that increase carbon net gain in photosynthesis under low light intensity. The light available raise in the understory, related to disturbance intensity, causes changes in functional leaf traits and tree architecture, related to the capture and light use to understory species. It is also expected that distinct disturbance in understory, favors species groups with different functional characteristics. This study evaluated the intensity of disturbance influence on functional leaf traits (leaf area, dry matter content and specific leaf area), the canopy architecture and wood density of understory species to nine forests. It was also evaluated the leaves functional traits variability into inter / intraspecific levels, and species distinction based on functional traits. The understory functional diversity was estimated based in indices of richness, evenness and functional divergence and species specific leaf area. The results showed that the leaf traits variability were concentrated in the interspecific level, and then has great importance in the species functional differentiation. The increase of disturbance intensity in the understory favored species with higher specific leaf area, contrary to many studies that observed a reduction of this trait with disturbance increase. The differences in relative densities of functionally similar species under different disturbance stages of allowed to establish a model of succession to the understory of seasonal forests. The results also showed that understory with low floristic similarity were functionally very similar. The functional diversity indices established relationships between functional diversity and the conservation state of understory too. The wide variation in species functional traits allowed to identify different strategies of light use and absorption to the understory and thus may explain the high coexistence of species in the understory.