Impacts of gap planting on soil density and erosion

Abstract

By 2016, there were 32.70 million ha of degraded forests in Indonesia. If it is not quickly rehabilitated, there will be land use changes and expansion of industrial forest plantation, which significantly affects its biodiversity and environmental. This research aims to study the impacts of the gap planting technique with red jabon on soil density and erosion. The research used: (1) the gap planting technique of red jabon with a proportion of the total gap area to the total natural forest area of 40%: 60%, planting distance of 4m x 5m, and the number of trees planted of 200 stems/ha, (2) Digital-Humboldt Static Cone Penetrometer to measure soil density, and (3) stick for soil erosion measurement. The results showed that gap planting with red jabon to rehabilitate degraded natural forests increased the soil density, but its value was categorized as a very loose soil class. On the other hand, the soil erosion in gap area was lower than in degraded natural forest area, because the condition of a part of the degraded forest was unvegetated land, and there were the wastes of branches, twigs, and leaves as well as grown grasses on the soil surface that hinder the soil erosion in the gap area. This research concluded, that the impact of the gap planting on soil density can be neglected, and the impact of the gap planting on soil erosion is positive. Further research on social-economic, biodiversity, effective and efficiency aspects of the gap planting technique for forest rehabilitation are needed before its implementation.