Resprouting is a common mechanism of persistence of woody species. After severe disturbances, when most of the above-ground biomass is destroyed, woody species with the ability to resprout quickly recover by producing new sprouts, whereas species without sprouting ability usually die and their further persistence depends solely on regeneration from seed. However, resprouting ability varies greatly even among good resprouters with some trees failing to resprout but the causes underlying this variation are poorly understood. We hypothesized that competition among trees influences both their sprouting ability and initial sprout growth because growth responses to competition are affected by pre-disturbance resource allocation within individual plants. In addition, we expected the effect of conspecific competition to be stronger than that of heterospecific competition, which would be also reflected in the effect of tree diversity, but the sizes and directions of the effects would vary with species identity. We tested these hypotheses using 2192 mapped trees of six species measured before and six years after harvest. Tree survival and growth was modelled as a function of tree size, identity, diversity and distance-dependent competition indices representing pre-harvest shading and crowding as well as post-harvest competition among resprouting trees.
Results/Conclusions
Our results showed that the likelihood of resprouting of a damaged tree is negatively affected by shading and positively affected by crowding but there was a significant variation in sizes of the effect among species. We also observed that within three years following the complete removal of above-ground biomass, resprouting trees began to compete intensively for resources but species identity did not affect it. However, most of the effects were driven by conspecific competition whereas heterospecific competition played only a minor role. Surprisingly, tree diversity had no significant effect. The present study demonstrated that competition had major effects on the sprouting behaviour of temperate trees. Interestingly, due to the strong positive effect of crowding on resprouting success, suppressed trees are more likely persist through severe disturbances than dominant trees, which also increases probability of the suppressed trees to become dominant in the newly establishing canopy. Because resprouting ability is almost universally driven by the level of resource storage in individual plants, competition is likely to affect sprouting in a variety of terrestrial ecosystems with woody vegetation.