Long-term outcome of precommercial thinning on floristic diversity in north western New Brunswick, Canada

Abstract

The Green River spacing trials were established between 1959 and 1961 to study the long-term growth and development of balsam fir (Abies balsamea (L.) Mill.) and red spruce (Picea rubens Sarg.) in response to precommercial thinning (PCT). Three nominal spacings (1.2 m, 1.8 m, 2.4 m) and an unthinned control were applied in a randomized complete block design with 5 replicates to regenerating stands, an average of 8 years after harvest. Our study examines floristic diversity associated with these treatments approximately four decades later. Floristic diversity was assessed with several alpha diversity indices as well as multivariate analysis to compare community composition. Specific a-priori contrasts compared plant diversity among a) control and average of the wider spacings (1.8 m and 2.4 m), b) control and the narrowest spacing (1.2 m), and c) the narrowest spacing and the widest spacing. Our results indicate that there were no appreciable differences among the treatments across all measures of plant diversity investigated. As such, we conclude that the forest understory, as represented by the unthinned plots, was analogous in the thinned plots at time of stand maturity. Vegetation response to PCT treatments is inconsistent in the published literature, but this can be attributed to differences in thinning intensities, recovery age or the type of forest ecosystem studied. We conclude that PCT is a variable silvicultural tool that could be used to attain both economic productivity and biodiversity conservation goals

A Checklist of the Marchantiophyta and Anthocerotophyta of New Brunswick, Canada

“…; found on rocks and humus of Northumberland, Restigouche, Victoria, and Charlotte counties; rare, possibly restricted, but also under-collected; 5 total records, with 1 at NBM and others at CANM and YU. Belland (1992), Clay and Richards (1996), Schuster (1969), Cole et al (2008), Fenton and Frego (2005).…”

“…Found on rotting wood and humus in shady forest sites of Albert, Charlotte, Gloucester, Kent, Kings, Madawaska, Northumberland, Restigouche, Saint John, Victoria, Westmorland, and York counties; widespread and frequent, but small and under-reported (only 9 primary taxon records at NBM, but 67 as associate taxa), often mixed with other species; 83 total records, with 76 at NBM and others at CINC, FH, NY, and NYS; Belland (1992), Clay and Richards (1996), Cole et al (2008), Fenton and Frego (2005).…”

“…Nees Found on rotting logs or tree bases in shady forests of all counties; widespread and common, often growing intermixed with other liverworts; 49 total records, with 40 at NBM and others at CANM, FH, NY, UBC, and YU; Cole et al (2008), Fenton and Frego (2005), Schuster (1969).…”

“…Grolle Found exclusively on decaying logs, in deciduous or mixed forests of Kings, Madawaska, Saint John, and Victoria counties; uncommon, possibly under-collected and under-reported; 4 total records, with 2 at NBM and 2 at UNBSJ; Cole et al (2008). …”

Legacy effects of precommercial thinning on the natural regeneration of next rotation balsam fir stands in eastern Canada

“…Because of its impacts on stand structure, density, crown development and light regime in the understory, PCT has the potential to influence vegetation, woody debris and regeneration. Precommercial thinning can indeed modify the composition and abundance of understory vegetation (Lindgren et al 2006), although effects can be modest in mature stands and vary over time because of residual tree growth (Hale 2003;Cole et al 2008Cole et al , 2010 and self-thinning . Moreover, the increasing presence of coarse woody debris (CWD) post-harvest (Fraver et al 2002), which can be affected by initial stocking (Sturtevant et al 1997) and wood utilization, may affect regeneration as CWD create physical barriers that limit access to space and light, thereby reducing soil temperature and its fluctuation (Trottier-Picard et al 2014).…”