Pre-disturbance tree size, sprouting vigour and competition drive the survival and growth of resprouting trees

Forest trees of many species are able to recover from logging and other severe disturbances by resprouting. Due to rapid growth, sprouts often form a significant part of forest regeneration and are also a key component of coppice forests. However, there is a large variation in both resprouting success and sprout growth whose drivers are still poorly understood in forest trees. Here, we test the hypothesis that pre-disturbance tree size and competition not only influence resprouting success and initial sprout growth (i.e., resprouting vigour) but also, together with sprout competition and resprouting vigour, drive long-term growth and survival of resprouting trees. To test it, we analysed data on 2236 trees of four common temperate European broadleaved species collected in a fenced 4 ha-experimental plot before and for seven years after harvesting. The plot was divided into 16 subplots with different densities of residual trees left, ranging from 0 to 200 tree per ha. The great majority of the logged trees recovered and were alive at the end of the study. Both pre-harvest tree size and competition affected resprouting success, but the direction of these effects varied with species. In all species, sprout growth increased with pre-harvest tree size and with resprouting vigour but declined with post-harvest competition from nearby resprouting and uncut trees. The overall faster sprout growth in originally larger trees suggests that dominant canopy trees are likely to restore their dominance in the new canopy after disturbances, thus ensuring long-term persistence and seed production. The decline in sprout growth due to intense competition among resprouting trees indicates that early thinning could enhance sprout performance and it could also be used to suppress undesired species.