Blog Posts

Thank you Hans. Indeed, leaving tree leaves on the ground could contribute to reduce erosion. Letting the understorey vegetation naturally re-growing is another one. In the studied teak tree plantations, most farmers intentionally kept the soil bare under mature teak trees by recurrent burning of the understorey. According to surveys, this practice resulted from a mix of beliefs and practical considerations. i) Farmers generally considered that understorey vegetation competed with teak trees in accessing soil water and nutrients. Thus, they believed that burning this understorey vegetation improved teak trees' access to resources even though teak trees were known to explore and exploit deep soil layers much more thoroughly than understorey species. ii) When clearing plots to grow annual crops, farmers usually poorly controlled the spread of fire into adjacent teak tree plantations; since adult teak trees are fire-resistant, this represented a convenient and effortless way of suppressing understorey vegetation in teak tree plantations. iii) The absence of understorey vegetation in teak tree plantations also improved access to and circulation within plantations, which was a desirable feature for many farmers for maintenance and exploitation purposes (NTFP harvesting, pruning, thinning, etc).

One attractive solution to control erosion is to introduce understorey cash crops to the tree plantations. Interspersing teak trees with understorey crops promotes rainwater infiltration into the soil, which reduced soil surface erosion. At the same time, the soil enrichment with organic material improves its water holding capacity, thus enabling plant development during the dry season. Depending on local soil and climate conditions, several species could be cropped under teak trees with potential economic returns: galangal, ginger, broom grass, cardamom, or natural grass…