Germination and establishment of natural red spruce (Picea rubens) seedlings in silvicultural gaps of different sizes

Abstract

Red spruce (Picea rubens Sarg.) is difficult to regenerate from natural seeding following silvicultural treatment. In order to study its germination and establishment, we monitored the dynamics of new seedlings over 10 years in silvicultural gaps of different sizes (small: < 100 m 2 , medium: 100-300 m 2 , large: > 700 m 2 ). Seedling density was higher in small gaps but survival rate did not exceed 40%, leaving few live seedlings after 10 years (< 200 ha -1 ). Mounds were the best microtopography for seedlings. Our results confirm the important role of decaying wood and moss for understory germination and establishment. Decaying wood was important for the establishment in large gaps while humus was more favourable in medium gaps. In small gaps, germinants and established seedlings were found as much on moss as humus and decaying wood. However, low observed densities suggest that planting in small or medium gaps should be explored for accelerating species renewal, especially if advance regeneration is deficient.Keywords: Decaying wood, microsites, natural regeneration, red spruce (Picea rubens), seedbeds, silvicultural gaps. RÉSUMÉL' épinette rouge (Picea rubens Sarg.) est difficile à régénérer par ensemencement naturel après une intervention sylvicole. Pour étudier sa germination et son établissement, nous avons suivi durant 10 ans la dynamique des nouveaux semis dans des trouées sylvicoles de différentes tailles (petites : < 100 m 2 , moyennes : 100-300 m 2 , grandes : > 700 m 2 ). La densité de semis a été plus élevée dans les petites trouées, mais le taux de survie n'a pas dépassé 40 %, laissant peu de semis vivants après 10 ans (< 200 ha -1 ). Les buttes ont été la meilleure microtopographie pour les semis. Nos résultats confirment le rôle important du bois en décomposition et de la mousse pour la germination et l' établissement sous couvert. Le bois pourri s' est avéré important pour l' établissement dans les grandes trouées, alors que l'humus a été plus favorable dans les moyennes trouées. Dans les petites trouées, les germinants et les semis établis se trouvaient autant sur de la mousse que sur de l'humus ou du bois pourri. Cependant, les faibles densités observées suggèrent que la plantation dans de petites ou moyennes trouées soit une avenue à explorer afin d'accélérer le renouvellement de l' espèce, d'autant plus si la régénération préétablie est déficiente. Mots-clés :Bois en décomposition, épinette rouge (Picea rubens), lits de germination, microsites, régénération naturelle, trouées sylvicoles.

Physical Properties of Seeds of Eleven Spruce Species

“…Young spruce shoots are abundant in vitamin C, and they are a popular folk remedy for coughs, colds, respiratory ailments, and pain. Spruce oil has antibacterial and antifungal properties [16][17][18][19][20]. In survival situations, spruce needles can be directly consumed or boiled into tea.…”

“…Spruce needles, young twigs, and essential oils are used to brew spruce beer. Spruce seeds and young plants are readily consumed by various forest animals, which often cause substantial damage to spruce stands [16][17][18][19][20].…”

Characterizing Red Spruce (Picea rubens Sarg.) Advanced Reproduction in an High Elevation Stand in West Virginia

“…Lhotka et al (2018), examined the effects of gap size on species composition and volume increases over fifty years in oak stands and found that species diversity and growth were significantly reduced in light limited small gaps (200 m 2 ). The effects of gap size on regeneration species composition, survival, light availability, seedling density, and growth responses are well documented (Brokaw, 1985;Dumais and Prevost, 2016;Nakashizuka, 1984;Qinghong and Hytteborn, 1991;Rentch et al, 2016;Wu et al, 1999). Changes in irradiance have large impacts on seedling development and growth (Gilbert et al 2001;Denslow 1987).…”

“…This would suggest that competition may be greater in larger gaps or gap centers, where canopy openings permit more direct light to hit the forest floor (Brokaw and Busing, 2000;Diaci et al, 2012;Dumais and Prevost, 2016;Vilhar et al, 2014). In some studies however, established shade-tolerant seedlings can respond to the light regime change and grow into the canopy (Wu et al 1999;Yamamoto 2000;Couwenberghe et al 2010;Copenheaver et al 2014).…”

“…Some research suggests spruce restoration may be attainable through active management practices that simulate natural canopy disturbance, but that gap size or overstory density dictates regeneration success. Smaller openings (<100 m 2 ) which increase light availability while retaining some shade from the overstory have been shown effective in maintaining seedling survival (Dumais and Prevost, 2016). Growth simulations suggest hardwood basal area reductions of 50%, could double red spruce basal area in as little as 20 years .…”