Physiology and growth of advance Picea rubens and Abies balsamea regeneration following different canopy openings

Abstract

We examined the ecophysiology and growth of 0.3-1.3 m tall advance red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea [L.] Mill.) regeneration during a 5-year period following the application of different harvest types producing three sizes of canopy openings: (i) small gaps (<100 m(2) in area; SMA) created by partial uniform single-tree harvest; (ii) irregular gaps of intermediate size (100-300 m(2); INT) created by group-selection harvest (removal of groups of trees, mainly balsam fir, with uniform partial removal between groups); and (iii) large circular gaps (700 m(2); LAR) created by patch-selection harvest (removal of trees in 30-m diameter circular areas with uniform partial removal between gaps). An unharvested control (CON) was monitored for comparison. At the ecophysiological level, we mainly found differences in light-saturated photosynthesis of red spruce and specific leaf area of balsam fir among treatments. Consequently, we observed good height growth of both species in CON and INT, but fir surpassed spruce in SMA and LAR. Results suggest that intermediate 100-300 m(2) irregular openings create microenvironmental conditions that may promote short-term ecophysiology and growth of red spruce, allowing the species to compete with balsam fir advance regeneration. Finally, results observed for spruce in large 700-m(2) openings confirm its inability to grow as rapidly as fir in comparable open conditions.

Gap closure process by lateral extension growth of canopy trees and its effect on woody species regeneration in a temperate secondary forest, Northeast China

“…Franco and Prunus lusitanica L. in the laurel forest of Tenerife, Canary Islands, and pointed out that regeneration in gaps with size less than 100 m 2 was insignificantly different from regeneration below the canopy. Middle gaps sometimes acted as "optimal size range" for species regeneration (Dumais and Prévost 2014). For example, after 5-year study, Dumais and Prévost (2014) claimed that 100-300 m 2 canopy gaps provided favorable micro-environmental conditions which promoted the growth of red spruce (Picea rubens Sarg.).…”

“…Middle gaps sometimes acted as "optimal size range" for species regeneration (Dumais and Prévost 2014). For example, after 5-year study, Dumais and Prévost (2014) claimed that 100-300 m 2 canopy gaps provided favorable micro-environmental conditions which promoted the growth of red spruce (Picea rubens Sarg.). However, Arevalo and Fernandez-Palacios (2007) argued that gaps between 100 and 300 m 2 inhibited the regeneration, because increased light intensity was insufficient for light-demanding species, but superfluous for shade-tolerant species.…”

“…However, the regeneration in small gaps may eventually fail without addition gap disturbance. Considering the sample size of large gaps (2 repetitions), middle gaps (4 repetitions) and small gaps (6 repetitions) in our study, it may be acceptable in experiments of artificial gaps (Dumais and Prévost 2014). On one hand, we had to be subject to the conservation policy of natural forests, which strictly limited the cutting area.…”

Mixedwood silviculture in North America: the science and art of managing for complex, multi-species temperate forests

“…In eastern hemlock -hardwood stands of the Great Lakes region, for example, Webster and Lorimer (2005) observed that canopy gaps 200 to 1000 m 2 were effective for maintaining species with a range of shade tolerances, with mid-tolerant species such as yellow birch favored in gaps > 250 m 2 . In spruce -hardwoods, Raymond et al (2018) found that 100-250 m 2 gaps had higher densities of yellow birch than red spruce reproduction, though Dumais and Prévost (2014) observed favorable growth of red spruce in openings of that size. Regardless of opening size, carefully selected trees can be retained within gaps for seed, growing stock, or biodiversity conservation (Carter et al 2017;Kern et al 2017;Knapp et al 2019).…”

Conifer regeneration in managed temperate mixedwood stands: the balance between release and competition

“…There is some evidence to suggest gap size may have important impacts on species diversity and seedling growth (Coates and Burton 1997). Though recent research efforts into mixedwood forest silviculture will help us improve practices (Bataineh et al 2013;Hébert et al 2013;Dumais and Prévost 2014), much knowledge remains to be acquired to better understand this complex ecosystem. Long-term studies (C10 years) are especially important because short-term (2-3 years) results do not always reflect longterm stand development due to species specific survival and growth patterns.…”