Filling a void: Analysis of early tropical soil and vegetative recovery under leguminous, post-coal mine reforestation plantations in East Kalimantan, Indonesia

BACKGROUND

Surface mining is a common practice for obtaining coal, the world’s leading energy source. Surface mining removes vegetation, soil, and rocks to extract resources. In Indonesia, the world’s fifth largest coal producer, coal mining companies are required to rehabilitate mined sites. Companies typically plant exotic legume tree species because they quickly achieve canopy closure, limit invasive weeds, improve soil nitrogen, and create a light environment that helps with the recruitment of woody plants. This article looks to see whether natural forest succession occurs under leguminous plantations at rehabilitated coal mines in East Kalimantan, Indonesia. 

RESEARCH GOALS & METHODS

The authors used a space-for-time sampling design to measure how vegetation communities and soils changed over time. The study looked at three different age classes of plantations of exotic legumes, such as Acacia mangium and Paraserianthes falcataria, on reclaimed coal mining sites. The study tested for improvements in soil nutrients and pH levels over time and whether vegetation dynamics showed a trajectory toward recovered native forest structure and composition underneath the exotic plantings.

CONCLUSIONS AND TAKEAWAYS

Based on this study, planting exotic legumes alone is insufficient to restore native forests in former mine sites. Although the results showed that legumes could establish on reclaimed mine sites, the recruitment of woody plants was limited to a highly narrow guild. Using synthesized fertilizer or organic soil amendments such as compost and wood chips can improve soil fertility. In addition, applying lime to soils can reduce acidity, reduce heavy metal toxicity, and increase the survival rate of plantings.