Interspecific variation in the size-dependent resprouting ability of temperate woody species and its adaptive significance

Summary Resprouting of woody species after above-ground damage may help plants to persist longer at a given site and quickly reoccupy disturbed sites, thereby strongly influencing forest dynamics. Resprouting has been discussed from two adaptation perspectives: recovery from damage by catastrophic disturbance and survival in frequently disturbed shaded understorey. However, few studies have comprehensively dealt with both adaptation types to understand resprouting strategies. To understand the adaptive significance of resprouting, we assessed the size dependence of resprouting ability after stem clipping for 24 deciduous broad-leaved species, including shrubs, sub-canopy and canopy trees, in a cool-temperate forest in Japan. The community assembly includes species adapted to past catastrophic disturbances (e.g. fire, logging) and to stable forest with intermittent treefall (currently the dominant disturbance). We correlated resprouting ability with life-history strategies based on demographic parameters and plant functional traits, such as leaf mass per area (LMA), leaf toughness and wood density. All the studied species could resprout in juveniles, and resprouting ability increased as stump size increased. Most sub-canopy and canopy trees lost their ability to resprout after attaining a particular stump size, whereas shrub species retained the ability to resprout throughout their lifetimes. The relative growth rate, LMA and foliar nitrogen did not greatly influence the resprouting ability of a species. In contrast, species with smaller maximum size, lower leaf toughness and lower wood density had better juvenile resprouting ability. This better resprouting ability may have evolved because these characteristics make them more vulnerable to shaded understorey. However, species with larger maximum size and lower leaf toughness retained their ability to resprout to a larger size. Synthesis. A better resprouting ability is related to the ability to survive frequent disturbances, in juveniles, which are characteristics of both forest understorey and frequent fire or drought. To retain resprouting ability until grown seems to be an adaptation to survive infrequent large disturbances. Light-demanding species, which generally have better resprouting ability than shade-tolerants both in juveniles and adults, are adapted to disturbances of various scale and frequency; however, shade-tolerants could survive well in the understorey due to a combination of stronger physical defences and resprouting ability.