Fisioecologia comparativa de gramí­neas nativas e invasoras em duas fitofisionomias de um fragmento de cerrado

Abstract

KAYANO, G.M. Comparative physioecology of native and invasive grasses in two distinct cerrado formations. 2018. Dissertação (Mestrado) -Instituto de Biociências, Universidade de São Paulo, SP. Invasions by African grasses constitutes one of the greatest threats to the biological and functional diversity of the cerrado savannas. A central question to understand plant invasions is how species originating from systems with distinct selective pressures are able to acquire and utilize resources in their new environments. The objective of this study was to compare native and invasive grasses with respect to their light and water use patterns in two sites with differing canopy tree cover along an invasion gradient in a cerrado area in the Juquery State Park, SP.The effect of the canopy tree cover on the grass individuals was investigated through sampling in the cerrado physiognomies of 'campo sujo' (tree cover absent) and 'campo cerrado' (tree cover present). The hypothesis that invaders outperform natives under the presence of canopy tree cover in terms of resource-use was tested through field measurements of traits related to light interception capacity and to the performance in light and water use associated with carbon gain potentials. Invasive African grasses showed distinct patterns of crown architecture and leaf structure when compared to natives. Invaders showed a greater degree of leaf overlapping in the crown. Invaders leaves were thinner, relatively more planophile, and showed smaller leaf dry mass per area ratios. The presence of canopy tree cover favored the invaders photochemical electron transport while disfavored natives. The main differences concerning native and invaders gas-exchange dynamics were observed on a leaf dry mass basis. The relation between patterns of leaf tissue investment and photosynthetic potentials could imply in contrasting responses of native and invasive grasses to the irradiance regime in differing cerrado vegetation types.