The absorbed CO2 in the Litsea-Cassava agroforestry model varies from 25 to 84 tons per hectare and provides a profit to small farmers ranging from VND 9 to 30 million per hectare, representing 20% of the total product value of Litsea and cassava. This was the major finding of the recently completed research project of the Vietnam Network for Agroforestry Education (VNAFE) on “CO2 Sequestration Estimation for the Litsea-Cassava Agroforestry Model in Mang Yang District, Gia Lai Province in the Central Highlands of Vietnam. “
The research was aimed at (a) constructing a model for biomass estimation and CO2 sequestration potential of Litsea glutinosa, and (b) defining the amount of absorbed CO2 and its environmental values in the Litsea–Cassava agroforestry model. Litsea is an indigenous, multi-purpose, green broadleaved species found mostly in semi-deciduous forest in the Central Highlands of Vietnam. Most of its biomass (stem, bark, leaves, and branches) can be used or sold in the market to produce different products. Litsea is usually planted in agroforestry models together with annual crops such as cassava, rice, and coffee.
Other findings of the research are as follows:
(a) In order to obtain effective productivity, Litsea should be harvested after ten years. At present, farmers are harvesting Litsea at between 4-6 years. It is not advisable to harvest Litsea within this period because this is when strong growth occurs.
(b) The stored carbon and CO2 sequestration in the Litsea-Cassava agroforestry model can be estimated in three ways:
1. Based on the rate (%) of stored carbon compared to the dry biomass of the four components of tree: stem (47.7%), bark (45.4%), leaves (48.7%) and branches (47.6%), with carbon per hectare calculated based on tree density. Although this method gave the highest accuracy, it was, however, costly.
2. Based on a model that estimates the carbon stored in the mean tree: C/tree = f(Dg), with carbon per hectare calculated based on tree density. This method had a relative error of 3.2%.
3. Based on a model that estimated the carbon per hectare: C/ha = f(No of shoots/stump, N/ha, Dg). This method gave a relative error of 2.7%.
(c) The Litsea-Cassava agroforestry model in the second and the third periods should leave 2 to 3 Litsea shoots per stump. This will result in the greatest production of biomass and CO2 concentration, with the possibility of optimal CO2 absorption from 3 to 84 tons, increasing with age.
The research was conducted by a team of faculty members and students from the Tay Nguyen University (TNU) in partnership with the staff of the People’s Committee and Department of Agricultural and Rural Development of Mang Yang District. The team was led by Dr. Bao Huy, Head of TNU’s Department of Forest Resources & Environment Management and VNAFE Chair. The Swedish International Development Cooperation Agency (Sida) through SEANAFE funded the project.
For details of the research results, please visit: Web Site: http://www.socialforestry.org.vn