Crescimento de três espécies arbóreas frutíferas sob competição em área de restauração florestal

Abstract

The restoration of ecosystems faces challenges due to the lack of incentives for rural landowners in the context of reconstituting the Legal Reserve and Permanent Preservation Areas, mainly because of the high implementation costs involved in active restoration. In addition to this lack of incentive, there is a knowledge gap in the silviculture of native species that needs to be filled given the extensive existing biodiversity. It is known that, for fruiting to occur, the plant requires specific conditions, such as sunlight exposure, minimal competition for resources, and proper management. These conditions ensure that the tree will have vegetative growth considered normal and a consequent accumulation of reserves that will be directed towards fruiting. Without the accumulation of reserves, the plant does not enter the fruiting process or does not produce sufficiently. Therefore, this study aims to analyze the growth pattern of three fruit species under competition in a forest restoration area. The experiment is located in the municipality of Ijaci (MG), since 2018, and consists of an area for reconstituting the Legal Reserve. The area covers a total of 3,19 ha, where 41 tree species for timber and non-timber use, both pioneer and non-pioneer, were planted in a spacing of 4,5 m² (3 x 1,5 m). The fruit species of interest are Bixaorellana, Psidiumguajava, and Schinusterebinthifolia. The planting was monitored over time, with four evaluations in the total area, measuring the diameter at breast height (DBH) and height (Ht) of all individuals. Additionally, in the first three evaluations, the canopy areas of 11 species with the highest density in the area were measured. After data collection, descriptive statistics were performed on the obtained information to create growth curves, test and adjust eight hypsometric models, and analyze the competition between the target species and neighboring trees, using distance-independent indices, Basal Area Larger (BAL), and Glover and Hool Index (IGH). Moreover, illustrations were generated from the canopy data, simulating canopy closure and allowing for inferences regarding light incidence on the plants. The average DBH (cm) and Ht (m) recorded five years after implementation were 4,6 cm and 4,8 m for B. orellana, 3,4 cm and 4,4 m for P. guajava, and 6,4 cm and 7,5 m for S. terebinthifolia, respectively. The hypsometric model that best fit to predict Ht was the generic model with the inclusion of the age variable, for B. orellana and P. guajava. None of the tested models were effective in estimating Ht based on DBH and age for S. terebinthifolia. It was confirmed that the species are under the effect of competition, especially by verifying the strong correlation between the BAL and IGH indices with the current annual increment of Ht for S. terebinthifolia. In conclusion, it was evidenced that the forest dynamics in the restoration area can affect the morphological attributes of the fruit species of interest, which consequently will have drawbacks for the fruiting process.