Spatial distribution of late-successional coniferous species regeneration following disturbance in southwestern Quebec boreal forest

Remnant tree stands left intact following a disturbance constitute the sole seed banks available for regeneration of coniferous species that neither bear serotinous cones nor reproduce vegetatively. The success of regeneration of tree species on these disturbed sites is, therefore, dependent on the distance from potential seed sources. The regeneration of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss) and white cedar (Thuja occidentalis L.) was studied at two sites in Quebec's southwestern boreal forest in order to quantify the influence of remnant stands on spatial distribution of regeneration. The first site is located in an area that burned in 1944 while the second site is located in an area that was clear-cut in the mid-1980s. Canonical correspondence analyses were used to determine the respective contributions of environmental data and spatial variables to the pattern of spatial distribution of regeneration. The results reveal that distance from a remnant stand is the most important variable in explaining spatial distribution of regeneration when compared to environmental variables such as soil type, drainage, slope and altitude. The plots of regeneration density against distance from a remnant stand for both the burned site and logged site show that regeneration density decreases abruptly with distance from a remnant stand. Furthermore, spatial autocorrelation analyses (Moran's I) indicate that even small remnant zones can significantly influence the pattern of spatial distribution of regeneration for the three species studied. The results presented here suggest that where preestablished regeneration is not abundant enough, alternative silvicultural systems such as strip clear-cutting or seed-tree systems could be used instead of cuts with protection of regeneration and soils (CPRS). (C) 2001 Elsevier Science B.V. All rights reserved.