Greenhouse gas emissions and carbon stock changes in rubber tree plantations in Thailand from 1990 to 2004

Rubber trees provide a variety of raw materials to manufacturing industries. Evaluating the environmental impacts throughout the life cycle of the trees is therefore important. In this study, the carbon stock and greenhouse gas emission profile throughout the complete cropping cycle of rubber plantations was estimated. The amount of biomass carbon stocks per hectare were estimated using a logistic growth model, expressed as 142.47/(1 + 13.31e−0.19t), where t is rubber age. Using this model, we found that carbon stocks in rubber tree plantations were continuously increasing until the rubber trees reached an age of 22–25 years. On average, the carbon stock in the 25 years of a rubber tree biomass was about 128.4 t C ha−1. Although the carbon stock in latex also increased in a similar way to that of rubber trees, it was much less than that in the biomass of the rubber trees. Based on calculations involving Thailandʹs total rubber planting area (with various ages of rubber trees), the yearly average carbon stock change was the net increase of 1.71 Mt C y−1. On the other hand the yearly average greenhouse gas emission from cultivation of rubber tree was 0.32 Mt C-e y−1. Compared to the increment of biomass carbon, the carbon emissions from rubber cultivation activities, mainly from fertilizer and herbicide application, were relatively small.