Living biomass of fallow areas under a REDD+ project in mountainous terrain of Northern Laos

ABSTRACT

There has been an expansion of the fallow areas in the mountainous terrain of Northern Laos, resulting in a significant effect on greenhouse gas emissions in the region. This study estimated living biomass of variously aged fallow areas (4–35 years old) in mountainous terrain. The living biomass of study sites, which was estimated by applying original allometric equations in each plant component, ranged from 49.4 to 390.1 Mg ha⁻¹. Using individual biomass data, we then developed a growth model based on a correlation between stand age (years after slash-and-burn) and living biomass in fallow areas >20 years old. The developed growth model was well fitted by a theoretical formula of Mitscherlich (Living biomass = 372.9 × [1 – 1.117 × exp(−0.05556 × stand age)]) (R² = 0.670). In addition, the area of each aged fallow area was estimated by analysis of time series of satellite imagery and change-detection analysis to detect past fire events (slash-and-burn). All of the living biomass of the fallow areas in each age were estimated using the developed model and were analyzed. The age-classed weighted mean value of living biomass in fallow areas was estimated as 111.4 Mg ha⁻¹. These results clarified that living biomass in fallow areas was dependent on age, and estimation methods including age data are essential for improving the estimation accuracy of forest carbon stocks in fallow areas during long-term Reducing Emissions from Deforestation and Forest Degradation projects in Northern Laos and surrounding regions.

KEYWORDS:

• Shifting cultivation
• carbon stock
• forest biomass dynamics
• growth model
• stand age

Acknowledgment

We received valuable comments from Mr. Issei Nonaka (Japan Forest Technology Association) and researchers at the National Agriculture and Forestry Research Institute, Laos.

Supplementary data

Supplementary data for this article can be accessed here.

Additional information

Funding

This study was supported by a project of the “Validation and Registration of the Project on REDD+ through Participatory Land and Forest Management for Avoiding Deforestation in Lao PDR (Japan International Cooperation Agency)” and a project of the “REDD+ project in Luang Prabang Province through controlling slash-and-burn (Ministry of the Environment, Japan)”.