Shade effect on the productivity and structure of natural campos communities

Doctoral thesis abstract

Abstract

The characteristics of the forest plantations determine the dynamics of photosynthetically active radiation (PAR) under the tree canopy and its area of influence. The objective of this work was to study the effect of shade on the structure and biomass production of the natural grassland (CN), analyzing the relationships between the light environment on the vegetation cover of the understory (%), the species present and their photosynthetic metabolisms. In addition, the effect of artificial shade on the production, seasonal distribution of forage and structure of a CN were analyzed for three years. P. taeda and E. grandis exhibited a similar light environment, presenting the lowest levels of plant cover. E. globulus showed a more illuminated environment, generating better conditions for plant development. C4 species increase their coverage against increases in incident photosynthetically active radiation (PARi) levels and C3 species achieve the highest coverage at intermediate levels of light interception. The composition in summer and autumn tends to become homogeneous over the years, associating with summer perennial grasses (GPE), regardless of the level of interception of solar radiation (IRS). In winter and spring the cover evolves towards a greater association with winter perennial grasses (GPI) and winter annual grasses (GAI) in the levels of greater shade. The increase in IRS levels increased the production of CN. The effect of shade over time determined different seasonal responses in biomass production and composition of functional types of plants. The shade modifies the botanical composition, increasing the coverage of GPI, GAI and reducing the GPE. The shade level modifies the seasonal distribution of forage, smoothing the annual production curve.