The influence of soil rutting severity on regeneration potential and seedling performance for black spruce-dominated peatlands

Abstract

. 2009. The influence of soil rutting severity on regeneration potential and seedling performance for black spruce-dominated peatlands. Can. J. Soil Sci. 89: 57Á66. Excessive rutting continues to be recorded in post-harvest compliance inspections in black spruce peatlands across Ontario. These qualitative, visual assessments, however, cannot provide the necessary data to determine a site disturbance threshold that is linked to poor regeneration and seedling growth. In an attempt to provide this quantitative link, harvested black spruce [Picea mariana (Mill.) B.S.P.] peatland sites were surveyed and divided into severely rutted (non-compliant), moderately rutted, and non-rutted (compliant) blocks. In 1995In , 2001In , and 2006, each block was assessed for areal extent of rutting, number of plantable spots, moisture status, planting medium, competition level, stand density, species composition, and black spruce seedling survival and growth. Black spruce seedling survival in the severely-rutted block was significantly lower when compared with either the moderately rutted or the non-rutted blocks. A derived seedling survival model identified moisture class as having the largest influence on the probability of seedling survival. In terms of seedling growth, however, it was the non-rutted blocks that had the poorest performance. Based on a canonical discriminant analysis (CDA), competition factors, particularly ericaceous shrub cover, were the most important microsite factors influencing black spruce seedling growth. Overall, the moderately rutted block generated conditions that resulted in high conifer recruitment and good seedling survival and growth. Although the inference space of the study is small, the results suggest that black spruce peatland sites may benefit from a moderate level of site disturbance caused during harvest operations.Key words: Rutting severity, black spruce peatlands, survival, growth, microsite assessment Morris, D. M., Mackereth, R. W., Duckert, D. R. et Hoepting, M. K. 2009. L'intensite´de l'ornie´rage et son incidence sur le potentiel de re´ge´ne´ration et la performance des plantules dans les tourbie`res a`e´pinette noire. Can. J. Soil Sci. 89: 57Á66. Dans les tourbie`res a`e´pinette noire de l'Ontario, les inspections de conformite´effectue´es apre`s la re´colte continuent de re´ve´ler un ornie´rage excessif. Ces e´valuations qualitatives, reposant sur un examen visuel, ne fournissent toutefois pas les donne´es essentielles qui permettraient d'e´tablir le degre´de perturbation a`partir duquel la foreˆt se re´ge´ne`re mal ou les plantules s'e´tablissent difficilement. Afin de combler cette lacune quantitative, les auteurs ont inspecte´des tourbie`res d'e´pinette noire [Picea mariana (Mill.) B.S.P.] apre`s leur exploitation et les ont se´pare´es en blocs selon l'ornie´rage (ornie´rage e´leve´ou nonconforme, ornie´rage mode´re´et aucun ornie´rage ou conformes). Chaque bloc a e´te´e´value´en 1995, 2001 et 2006 pour e´tablir l'ampleur de l'ornie´rage a`vol d'oiseau, le nombre de sites susc...

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

“…It is possible that without the ameliorating (compensating) effect of the fine litter (i.e., needles) decomposition and accompanying nutrient release associated with the SO treatment (Symonds et al 2013), N immobilization by the coarse logging debris (i.e., chips or solid wood), and their associated high C:N ratios (chips, 200:1; solid wood, 300:1; unpublished data), may have lowered N availability, in turn, contributing to these growth declines on the CH and FT treatments (Wiebe et al 2012). The slight improvement in height growth exhibited on the FTB treatment on the peatland sites is in all likelihood due to the elimination of the dense ericaceous shrub layer, shown to inhibit black spruce growth (Fenton et al 2005;Lavoie et al 2007;Morris et al 2009), and the exposure of richer (Om/Oh horizons) peat layers (Lafleur et al 2011). Although not significant, the positive effect of blading (FTB treatment) on the wet mineral sites was also evident (Fig.…”

“…Although this soil type can be extremely productive, it has been identified as being highly sensitive to harvesting due to its susceptibility to physical site damage through rutting, soil compaction, and disruption of hydrologic function (Archibald et al 1997;Morris 1997;Curran et al 2005). In turn, this harvest-related physical site damage has been shown to significantly reduce black spruce survival and early growth (Fenton et al 2005;Morris et al 2009). …”

Contrasting effects of season and method of harvest on soil properties and the growth of black spruce regeneration in the boreal forested peatlands of eastern Canada

“…More importantly, SCC produced soil conditions favourable to tree growth in greater abundance, producing overall stand growing conditions that were comparable to high-severity soil burns. The concern that greater soil damage by rutting during summer operations (Morris et al 2009) could decrease site productivity in organic soils was not verified one or two decades following harvest. These results therefore suggest that SCC reproduces to some extent the effects of high-severity soil burns (i.e.…”