Regeneration of native woody species following artificial gap formation in an early‐successional forest in New Zealand

Abstract

SummaryGap creation in recovering rainforests may reduce the intensity of competition and provide opportunities for later successional species to co‐occur with predominant earlier successional species. This study examined the potential of artificial gaps to facilitate the natural regeneration and establishment of woody species in dense regenerating stands of Kānuka (Kunzea robusta) that have developed following the removal of degrading factors especially clearing and grazing in many parts of New Zealand. Artificial gaps were created through selective felling of Kānuka canopy trees and the species composition, density, growth and survival of native woody species regenerating in the canopy gaps and under paired intact Kānuka canopies were monitored for 28 months. Gap creation resulted in a significant increase in the number of species and density of woody regeneration including a wider range of woody species, although no mature phase species (including podocarps) were found, potentially due to seed limitations. There was no significant effect detected with respect to the interaction of time and gap creation on species recruitment. Survival and growth of woody regeneration were significantly greater in canopy gaps than beneath the intact canopy despite the higher proportions of herbaceous ground vegetation and browsing incidence in gap treatments. The tendency of woody seedlings to grow taller in canopy gaps may have permitted them more rapid recovery from browsing. The duration of the study was too short to fully capture the potential of canopy intervention, but woody regeneration within the artificial gaps is likely to accelerate as the regeneration proceeds, especially if browsing is controlled, and the results presented here provide useful insight into the early stages of this process.