Indicadores de qualidade do solo e sistema de plantio adensado em área degradada na Amazônia

Abstract

Soil degradation results in the loss of organic matter and compaction, making the assessment of soil health through quality indicators essential for monitoring and adapting management practices in degraded areas. Furthermore, seeking new planting strategies for forest restoration is important so that areas that have suffered some type of degradation can be restored. In this context, the objectives of this study were: 1. To compare soil quality in forest areas and different topographies of a pasture area. 2. To analyze the survival and growth of tree species. 3. To evaluate the effect of grafting on C. sanguinolentum planted in spaced groups. The research was conducted at the Environmental Studies Center (CEA), located in the municipality of Vitória do Xingu, PA, in the Volta Grande do Xingu region. Soil samples were collected from the forest area and at three different altitude ranges (120-130 m, 130-140 m, and 140-150 m) in the degraded area to determine physical and chemical attributes, in addition to calculating the Soil Structural Quality Index (IQES). The dense planting technique consisted of the distribution of 30 groups located on three different topographies (120, 130, and 140 m). Each group was composed of 13 seedlings of forest species representing different successional stages, with the climax species C. sanguinolentum positioned in the center. In each altitude range, five grafted and five non-grafted individuals of C. sanguinolentum were planted in the center of the groups, and monitored over a six-month period. The soil analysis identified significant differences in physical and chemical parameters between forest areas and pasture areas, highlighting the impact of management practices in degraded areas. The forest areas exhibited better physical soil quality compared to the degraded areas. In the forest, there were higher concentrations of organic carbon, available phosphorus, and potassium, as well as a more acidic pH due to the accumulation of organic matter. On the other hand, the degraded altitude ranges showed a tendency toward soil compaction. In the dense planting, the mortality rate was 7.69%, with the species S. mombin and G. americana showing no mortality. S. mombin had the highest growth in height (75.87%) and diameter (168.25%). The species C. sanguinolentum showed better performance in diameter among the non-grafted seedlings, with mortality occurring only in the grafted seedlings. Seedling growth was influenced by altitude, with better diameter and height development of the studied species in the lower altitude area. The soil analysis results demonstrated that native vegetation contributes to the improvement of soil quality and maintains positive ecological processes, while inappropriate practices harm the soil's ecological functionality. Dense planting, in general, proved to be an effective strategy for ecological restoration, thus promoting ecosystem functionality and contributing to the advancement of ecological succession in degraded areas.