Above and belowground functional trait response to biochar addition in seedlings of six tropical dry forest tree species

The addition of biochar as a soil amendment has great potential for ecological restoration and long-term carbon (C) storage. However, few studies have evaluated the functional trait responses of tree seedlings to increasing application rates of biochar and almost no information is available for tropical dry forests (TDF). Here, we conducted a greenhouse experiment to quantify effects of rates of biochar (0, 5, 10, 20, and 40 t/ha) on demographic and functional traits of six tree species used in TDF restoration programs. After 100 days of growth, we found no negative effects of biochar on seedling survival and only in two of the species the highest dose applied slightly reduced the final biomass. The addition of biochar increased leaf chlorophyll content (LCC) and specific leaf area (SLA) of all species. Greater variation in above-and below-ground trait responses to biochar was due more to inter-specific (52%) and intra-specific (36%) differences than main effects of biochar across species (11%), although we found that 81% of the variation in the LCC was due to the addition of biochar. We found a positive effect of biochar on morphological traits related to C gain and physiological tolerance to drought (higher dry mass content of root, leaf, and stem, LCC, SLA, and leaf area ratio). Therefore, we suggest that applications of biochar between 5 to 30 t/ha do not compromise the early growth of the seedlings of the studied species, and even may improve their growth capacity and drought resistance during their establishment in the field.