To protect or to hide: Why not both? An investigation of fire-related strategies in Cerrado woody species

Two key strategies enable woody species persistence and survival in fire-prone ecosystems after fire: the aboveground protection of stems and buds by thick bark and the allocation of biomass belowground to specialized bud bearing storage organs - both strategies allowing plants to resprout new branches after the aboveground parts are damaged by fire. Here we investigate whether those two strategies can be combined with each other. We compared 24 woody species from the Cerrado (tropical savannas from Brazil) and analyzed their underground storage organs (USOs) in relation to their aboveground bark production and aerial bud protection - two key traits allowing species to first survive and then persist after fire - together with plant potential height. We then compared if bark growth rate, aerial bud protection and plant potential height are linked to the ecological function of the underground storage organs (on spot persistence vs clonal growth through lateral spreading). Species with woody rhizomes (capable of spreading laterally) better protected their aboveground stems with thicker bark when compared to species with xylopodium and root-crown organs (adapted for on spot basal resprouting). A clear division was found concerning how well species are protecting their aerial buds and the type of underground storage organ, with species spreading laterally displaying a greater aerial bud protec-tion. The results suggest that the presence of a specialized organ belowground does not appear to be mutually exclusive with producing thick bark on aboveground stems. It does exist, however, a different expression of bark production and aerial bud protection between species displaying lateral spread and those persisting on spot, suggesting the existence of a trade-off between above-and belowground strategies in species displaying on spot persistence. This highlights that Cerrado species can combine different fire-survival strategies, further ques-tioning which fire conditions promote each strategy and their combination and in which cases trade-offs occur. (AU)