Black spruce growth response to varying levels of biomass harvest intensity across a range of soil types: 15-year results

Abstract

With a growing interest in the diversification (e.g., bioenergy, biochemicals) of the forest industry beyond the traditional product streams, concerns that higher harvest utilization levels may compromise site productivity have been heightened. This study reports on 15-year tree growth responses to varying levels of biomass removals conducted on four soil types: loamy tills, outwash sands, wet mineral, and peatlands. Experimental harvest treatments included stem-only, full-tree, full-tree chipping (a full-tree harvest with the roadside material chipped and returned to the site), and full-tree + bladed (a full-tree harvest followed by forest floor removal). Results indicated no significant effect on height growth on the loamy tills, a significant decline for the blading treatment on the sandy soils, and an increase when the blading treatment was applied to the peatland sites. At the stand level, better planted seedling survival and higher recruitment of naturals on the more extreme removal treatment (forest floor removal on sandy sites) tended to nullify any negative impacts identified in the individual-tree growth measurements. The more than doubling of the slash loading on the stem-only treatment plots compared with the full-tree plots did not result in differences in tree productivity levels between these two operational treatments. The stands, however, were just approaching crown closure by year 15, suggesting that ongoing monitoring will be required to confirm that the growth trajectories for the various harvest treatment -soil type combinations can be maintained.Résumé : Dans la mesure où l'industrie forestière est de plus en plus intéressée à diversifier ses activités (p. ex., bioénergie et produits biochimiques) au-delà de sa gamme traditionnelle de produits, les craintes que l'utilisation plus complète de la forêt compromette la productivité des stations augmentent. Cette étude rend compte des réactions en croissance des arbres, après 15 ans, à différents degrés de prélèvement de la biomasse sur quatre types de sol : till loameux, sable fluvio-glaciaire, sol minéral humide et tourbières. Les traitements expérimentaux d'exploitation incluaient tronc entier, arbre entier, copeaux d'arbres entiers (récolte d'arbres entiers mis en copeaux en bordure de route et redistribués sur le site), arbre entier + lame bineuse (récolte d'arbres entiers et enlèvement de la couverture morte). Les résultats ne révèlent aucun effet significatif sur la croissance en hauteur sur le till loameux, mais il y a une diminution importante avec le traitement arbre entier + lame bineuse sur les sols sablonneux et une augmentation avec le même traitement dans les tourbières. À l'échelle du peuplement, une meilleure survie des semis plantés et plus de recrues d'origine naturelle dans le traitement où l'enlèvement de la biomasse était le plus prononcé (enlèvement de la couverture morte sur les sols sablonneux) avaient tendance à annuler tous les impacts négatifs identifiés dans les mesures de croissance d'arbres individuels. Dans le trai...

Effects of Biomass Removal Levels on Soil Carbon and Nutrient Reserves in Conifer‐Dominated, Coarse‐Textured Sites in Northern Ontario: 20‐Year Results

“…7), black spruce only on loamy sand sites (Fig. 8), consistent with tree and stand growth metrics reported on at earlier stages of development (Morris, 2013; Fleming et al 2014). At this stage of stand development (i.e., entering the crown closure phase), this growth reduction may largely be due to a moisture limitation on these sandy sites, as opposed to a nutrient limitation.…”

“…Trials included three levels of biomass removal: stem only, full‐tree, and full‐tree plus forest floor removal. The resulting installations now form an integral part of the North American Long‐term Soil Productivity (LTSP) network (Powers et al, 2005), with data contributing to broad LTSP synthesis efforts examining early tree growth response (Fleming et al, 2006; Ponder et al, 2012), as well as to regional species‐specific growth responses (black spruce [Morris, 2013]; jack pine [Fleming et al, 2014]).…”

Effectsof biomass harvest intensity and soil disturbance on jack pine stand productivity: 15-year results

“…Whereas broad-scale forest-floor removal may moderate microclimatic conditions and increase stand growth during the initial establishment phase, subsequent growth on less fertile soils is often compromised by nutrient limitations (Mendham et al 2003;Boateng et al 2006). Nevertheless, such responses are site dependent and vary with additional factors such as plantedtree survival and natural regeneration, as evidenced by the LTSP aspen and black spruce trials (Voldseth et al 2011;Morris et al 2014).…”

“…Reductions in planted-tree productivity following WT vs. SO harvesting have been demonstrated in several ecosystems at similar stages of stand development (Egnell and Leijon 1999;Smith et al 2000;Mason et al 2012), although this is by no means universal as evidenced across the LTSP (Ponder et al 2012;Morris et al 2014) or the related CIFOR network (Nambiar and Kallio 2008).…”

The influence of coarse woody debris on soil carbon and nutrient pools 15 years after clearcut harvesting in black spruce—dominated stands in northwestern Ontario, Canada

“…From a forest management perspective, guidelines need to recognize this important feature/contribution made by CWD in the harvested landscape. For example, when comparing slash retention between stem only (SO) harvests (all crown and stem tops retained on site) versus full-tree (FT) harvests (entire aboveground portion of the harvested tree is removed and processed at roadside) on these study sites, slash retention was more than double in the SO harvest treatments (a difference of 16 Mg ha -1 ) (Morris, Kwiaton & Duckert, 2014). Others have reported even greater differences between SO and FT harvests for different forest types/conditions (Egnell & Valinger, 2003: 26 Mg ha -1 ; Wei et al, 2012: 23.1 Mg ha -1 ; Maier et al, 2012: 25 Mg ha -1 ; Kabzems, 2012: 37 Mg ha -1 ).…”