Práticas silviculturais intensivas influenciam positivamente no estoque de carbono de florestas de restauração

Abstract

Forest restoration is emerging as a global strategy for mitigating critical environmental issues worldwide, such as environmental degradation and climate change. It then becomes a global strategy for mitigating these disturbances. Among several initiatives are the Bonn Challenge and the Paris agreement that promote the recovery of degraded areas. Knowledge of how the methods used for restoration and how silvicultural practices applied to each area influence the viability of projects is of great importance for decision makers. However, insights into these factors still remain incipient, therefore, the purpose of this study involves 20 years of evaluations of plantations under different forest restoration approaches. The objective of the work was to understand how silvicultural practices can maximize carbon stocks in restoration plantations. The experiment was conducted in an area of ~5 ha in Anhembi – SP following a three-way factorial design: model (A – proportion of pioneers/non-pioneers = 50/50 and B – proportion 67/33); spacing (1 – 3333 ind.ha-1 and 2 – 1666 ind.ha-1) and; forestry (U – traditional and X – intensive), thus totaling 8 treatments. 16 Inventories for data collection (diameter and height) were carried out over twenty years. The use of intensive forestry resulted in a 10% increase in survival (X – ~60%; U – ~50%) and an additional 8 Mg/ha to carbon stock over the entire experiment. This fact can be attributed to greater nutrient availability and less competition with invasive grasses. The higher planting density also resulted in greater carbon accumulation (>10 Mg/ha) due to the greater number of individuals. The model with the highest proportion of pioneers did not present a better result, on the contrary, at twenty years of age it presented lower carbon stocks (5Mg/ha), which may be correlated with the death of pioneers. As an example of the pioneers, we can mention Croton urucurana and Heliocarpus americana, which lost practically all their individuals. Considering all treatments, the best (A1X, B1X and A1U - ~57Mg/ha) accumulated almost twice as much carbon as the worst (A2U and B2U - ~30Mg/ha). In terms of implementation costs, all treatments showed the same efficiency, spending around US$140/Mg of stored carbon. Therefore, the recommendation to maximize carbon stock and survival in restoration projects is the use of intensive forestry, an equivalent proportion of pioneers and non-pioneers in addition to denser planting (when economically viable). Future research can expand the scope of this study by considering other carbon pools (soil, litter, regenerants and others) necessary to better understand the impact of each treatment.