Influence of the light environment on plant cover and photosynthetic metabolisms in understory communities

Abstract

The characteristics of forest plantations condition the dynamics of photosynthetically active radiation under the tree canopy and its area of influence, determining the development of understory communities. The purpose of this work was to study the relationships between the lighting environment and vegetation cover (%), the existing species and their photosynthetic metabolism. The study was performed in commercial forest plantations, along nine transects in a North-to-South direction that were located between rows, in alleys and natural grasslands, by placing 15 frames of 0.25 square meters every two meters in each one of them. The photosynthetically active radiation (PAR) value for each environment was recorded between 11 a.m. and 1 p.m. P. taeda and E. grandis displayed similar light interception while E. globulus provided a greater passage of PAR transmission into the forest floor, with favourable consequences to the development of the herbaceous structure community of the underbrush. C₄ species increased their coverage when faced with elevated PAR levels. On the contrary, C₃ species achieved greater coverage during intermediate levels of light interception. Higher levels of light interception indicate a lower coverage of the underbrush community, and the species with C₄ metabolic pathways were the most affected