Carbon sequestration and biodiversity of re-growing miombo woodlands in Mozambique

Background

This study aims to determine how slash-and-burn agriculture impacts soil and vegetation carbon (C) stocks and biodiversity on an area of miombo woodland in Mozambique. The study hypothesized that C stocks in vegetation and soils of abandoned agricultural plots (machambas) would be lower than in woodland plots and that C stocks would accumulate more rapidly after abandonment in vegetation than in soils.

Conclusions & Takeaways

The study found that while C stocks in stems were lower in machambas than in woodlands, there was no significant difference in stem C stocks found between woodlands and on abandoned farmland 20-30 years old; however structural differences in stocking density were found with significantly higher stem numbers in machambas than woodland plots. Additionally, the re-growing machamba plots did not contain the defining miombo species found in woodlands. The findings showed no discernible increase in soil C stocks during machamba re-growth period suggesting the rate of accumulation of organic mater in these soils is very slow. Because woodland soil C stocks showed significant variation it is not clear if slash-and-burn reduces soil C stocks. Woodland soils were found to be capable of storing >100t C ha-1 whereas no abandoned machamba soil exceeded 74 t C ha-1. Because stem wood stock did not exceed 33 t C ha-1, the authors recommend management and further research focus on preserving and increasing C sequestration in soil. The authors hypothesize that the lack of C accumulation in soil stocks of machambas could be due to frequent fire disturbance or possibly termite activity.