Light regimes (potossyntetic active radiation-PAR) and its effect at the biomass and the net primary productivity of Atlantic Forest species in different restoration models

Abstract

Among the ecosystems of tropical and subtropical forests, the Atlantic Forest is one of the most affected by land use change, remaining only 7.26% of its original vegetation cover. Currently, Atlantic Forest restoration has driven an increasing importance. Several public and private programs to promote this activity aim at aggregating values, particularly carbon sequestration. One question which remains open is the way the canopy species composition may affect the phothosintetic active radiation (PAR)avaiability in the system, thus altering the productivity and biomass accumulated above and beneath the soil, including the natural regeneration. This study aims at determining the light regimes (PAR) of different Atlantic Forest (seasonal semideciduous forest)restoration systems implanted 11 years ago, and the way they affect tree biomass (above and below ground) and net primary productivity of planted native species as well as the natural regeneration. The experimental areas are located at Botucatu, São Paulo, in two sites which soils are Red Nitosoil and a Red-Yellow Argisoil. Three treatments are being tested: T1=control; T2= Direct seeding with only 2 fast-growing tree species, both deciduous; T3 = high diversity mix planting (more than 30 species,some deciduous). The photosynthetic active radiation (PAR) will be monitored in each experimental area and treatment during five consecutive days four times in the year, and the values will be compared to the ones obtained in the FCA meteorological station.The leaf area index will also be estimated for each treatment.For the analysis of the tree biomass, 3 individuals from 20 species will be felled down and the roots will be unburied. The total phytomass of each individual will be determined by the sum of the biomass aboveground (leaves, twigs, branches and trunk) and belowground (roots). The net primary productivity will be estimated for each species, plot, block, treatment and experimental area, considering the 6-month stock for a period of 24 months. The seedling density, richness and phytomass of wood species natural regeneration will be evaluated in 4 sub-plots within each plot. Data will be submitted to analysis of variance and multivariate analysis. (AU)