Differential survival and growth of stumps in 14 woody species after conservation thinning in mixed oak-rich temperate forests

Abstract

Many trees sprout after cutting and other disturbances, and individuals may persist for a long time. In 25 forests in Sweden subjected to thinning for biodiversity values, we tested whether survival and growth of sprouts are related to stump diameter. Stem diameters vary under conservation thinning and earlier work had indicated high survival of stumps of small diameter. We also tested whether a continuum of responses in sprouting existed among the 14 species, as predicted by earlier work. We cut on average 26 % of the basal area (mean basal area 28 m2/ha) and analysed 1,044 stumps (diameters 10–76 cm). The response of the species after 9 years ranged along a continuum from weak to strong sprouting. Survival was highest for Corylus avellena (95 % of cut individuals survived) and Tilia cordata (85 %), then decreased as follows; Crataegus spp. > Alnus glutinosa > Prunus avium > Fraxinus excelsior > Quercus robur/Q. petraea > Salix caprea > Sorbus aucuparia > Acer platanoides > Betula pendula, to Betula pubescens (8 %) and Fagus sylvatica (8 %). Within species, stump survival was unrelated to stump diameter. Mean maximal sprout height of surviving stumps varied from about 1 to 4 m among the species after 9 years. Sprout height was unrelated to stump diameter. Stump survival (%) and mean sprout height were positively correlated across species. In conclusion, stem diameter had no effect on sprouting, but the 14 species could be clearly ranked in regrowth. Our results are useful in planning thinning of mixed forests for biodiversity conservation, for biomass harvest, or combined purposes.