Environment-driven spatial pattern of tamarind trees in riparian forests

Abstract

Domesticating indigenous agroforestry species is gaining interest as a potential option for conservation and production. Yet, spatial patterning of key species and how it is altered by environmental variations, which are important to design plantation schemes in forest and agroforestry systems, are still poorly documented. The pair-correlation function was used to assess spatial pattern of Tamarindus indica and its variation under contrasting environmental conditions (vegetation cover and soil degradation). Tamarind seeds being dispersed by zoochory and barochory, we hypothesized positive association within and among life stages (adults-adults, juveniles-juveniles, and adults- juveniles). Variations in environmental conditions did not significantly affect density and overall spatial pattern of either adult or juvenile trees. Adults and juveniles showed clumped patterns irrespective of environmental conditions. However, juveniles showed positive association with adults under low canopy cover and/or soil degradation, and independence from adults under dense canopy. This could be due to the shade intolerant status of this species and allelopathic effect of adults on juveniles under dense canopy. On the contrary, soil degradation favored attraction between adults and juveniles, presumably by inducing coppicing. Tamarind trees proved to withstand land degradation and could be used to restore degraded areas. To this end, we suggest introducing juveniles in patches of 40 m radius using a 10 m x 10 m planting grid, and at least 30 m from mature trees.