Reforestation of riparian fragments and its influence on the forest structure and carbon sequestration.

Abstract

In recent decades, the role played by planted forests in carbon sequestration has been an essential ecosystem service for maintaining the quality of life on the planet. In this study we compared the carbon stocks in soil, litter and aboveground tree biomass in four riparian reforested strips in the surroundings of the State Hydroelectric Power Plant (UHE) of Volta Grande at Minas Gerais, Brazil. The objectives are 1) to evaluate if and how much these new riparian stripes were able to change C stocks in comparison with baseline of neighboring sugarcane with reference areas and 2) to determine if the forest structure of restored strips of riparian forest, of the Volta Grande Reservoir, will change in terms of age and width since restoration. For this we asked the hypothesis that 1) older and narrower strips will present higher C stocks than younger and larger ones and 2) the structure of the vegetation will be different regarding age and size of the riparian stripes. The planted forest strips ranged from 30 to 100 m wide and 10 to 20 years old. Despite this, no significant differences (p < 0.5) were found in C stocks among areas. Carbon stock in trees was 86tMgC.ha-1 on average. Litter carbon stocks varied from 4.15 to 6.59 MgC.ha-1 and in the soil (0-30 cm), the values were about 31 MgC.ha-1 . Litter carbon stock was only significantly higher in narrower strips at (p<0.1) probably due to an edge effect. The new riparian reforested areas increased C stocks by 40% in the first decade compared to the baseline of the agricultural surrounding environments. This result corroborates other studies and encourages the restoration of riparian zones as an efficient and rapid mechanism for C sequestration, in addition to countless other ecosystem services. The work was carried out in four actively restored sites and one passively restored riparian stripes, around the Volta Grande Hydroelectric Reservoir (UHE-Volta Grande). We found that the five studied areas different regarding the structure of the restored riparian stripes while the PCA axes explained 63% of the variation with 26.48% in axes one and 37.11 in axes two are influenced by the age and width of the riparian strips. Based on the result obtained, the forest structure of the riparian stripes influenced the response variables at different rates and also the forest structures are influenced by the age and width of the riparian strips. Riparian buffer restorations are used as management tools to produce favorable water quality impacts, moreover among the many benefits riparian buffers may provide, their application as instruments for water quality restoration rests on a relatively firm foundation of research.