Interactive effect of water and nutrient on survival and growth of tree seedlings of four dry tropical tree species under grass competition

The increasingly degrading dry tropical forests due to anthropogenic perturbations may further show significant species and individual loss under changing climate condition. It is attributed to the later effect on soil water and nutrient availability, which may variably change the competitive ability, and thus survival of tree species seedlings. Currently, determining the response of tree species seedlings to environmental changes in dry tropical ecosystem is a key challenge. Therefore, understanding of factors, which govern the seedling characteristics, are necessary for maintenance and regeneration of these forests. Here, we aim to examine that how nutrient, water and grass interactively affect the tree seedling survival and growth of four dry tropical species viz., Ziziphus mauritiana and Terminalia arjuna (nonleguminous), and Acacia nilotica and Acacia catechu (leguminous). These four species were subjected to eight different combinations of treatments based on water availability, nutrient supplementation and grass competition. Their responses in terms of survival and growth parameters (i.e. height, circumference, aboveground dry weight, number of leaves, leaf area and relative growth rate) were recorded in each combination. It was observed that water and nutrient interactively affected the seedling growth significantly. Under all treatment combinations, leguminous species exhibited higher survival than non-leguminous species, however, a reverse trend was observed for seedlings growth parameters. Presence of grass had significant negative effect on seedling growth in all treatment combinations; however nonleguminous species showed more pronounced effect than leguminous species. We observed a considerable variation in the seedlings growth response of different tree species to the variation in growth conditions in dry tropical environment. The study provides a mechanistic insight about the change in forest community structure with the environmental changes, which would help in devising some management strategies to conserve and restore the dry tropical forest.