Tree species and size influence soil water partitioning in coffee agroforestry

Abstract

Complementary use of resources is considered a strong driver of enhanced performance in mixed-species assemblages. In income-producing agroforestry systems, economically valuable species will ideally benefit from resource partitioning. In agroforests in southern India, we assessed soil water uptake depths of coffee and different shade tree species at the end of the dry season, when water availability is regarded critical. Water isotopes ratios (δD and δ18O) from soil and plant samples were analyzed and an isotope mixing model was applied. Results suggest that coffee plants drew water mainly from the top soil (56% from 0 to 20 cm), and to a lower extent from the subsoil. Jackfruit trees had very similar uptake patterns, which suggest competition. Mango trees showed reverse patterns of water uptake with soil depth, i.e. drew more than 75% from the subsoil, which suggests spatial complementarity to coffee. Within and across shade tree species, soil water uptake from the top soil increased with increasing diameter. We suggest that shade tree species choice and diameter regulation are viable options in management for soil water use complementarity.