Stumping trials in British Columbia--organic matter removal and compaction effects on tree growth from seedlings to midrotation stands

There is considerable interest in understanding the repercussions of compaction and organic matter removal on soil quality and forest productivity. However, long-term field trials examining the effects of machinery and forest biomass removal on soil quality and stand regeneration are scarce. We present 20-31 years of tree growth results from four unique stump removal field trials. Each site had both treatments with varying amounts of organic matter removal (from tree stem harvesting to removal of tree stumps to loss of roots) and treatments with different levels of compaction due to site preparation machinery. Tree heights among the different treatments at midrotation were the same or taller than those with minimal organic matter removal and compaction. However, when stand development was evaluated using the quantity of tree volume for the given number of trees planted, treatment effects were clearly evident; tree volumes were significantly lower in compacted treatments, whereas organic matter removal did not appear to effect stand production. Although the sites were not directly comparable, when combined, the field trials provide insights to the possible implications of forest biomass harvesting on stand regeneration and overall forest soil quality. Key words: forest soil quality, compaction, organic matter removal, stumping, root rot. La comprehension des repercussions de la compaction et du prelevement de la matiere organique sur la qualite des sols et la productivite de la foret suscite un interet considerable. Cependant, il y a peu d'experiences a long terme sur le terrain qui portent sur les effets de la machinerie et du prelevement de la biomasse sur la qualite du sol et la regeneration des peuplements. Nous presentons des resultats de croissance des arbres provenant de quatre essais experimentaux particuliers 20 a 31 ans apres un dessouchage. Des traitements consistant a enlever differentes quantites de matiere organique (integrant successivement la recolte du tronc des arbres, le dessouchage et l'elimination des racines) ont ete appliques dans chacun des sites qui avaient aussi subis differents degres de compaction du sol par la machinerie utilisee pour la preparation du site. A mi-rotation la hauteur des arbres etait semblable dans les differents traitements ou plus grande que dans le traitement ou il y avait eu le minimum de prelevement de matiere organique et de compaction du sol. Cependant, lorsque le developpement du peuplement etait evalue en utilisant le volume des arbres pour un nombre donne d'arbres plantes, l'effet des traitements etait nettement visible : le volume des arbres etait significativement plus faible dans les traitements ou le sol avait ete compacte tandis que le prelevement de la matiere organique ne semblait pas avoir d'effet sur la production du peuplement. Bien que les sites ne soient pas directement comparables, lorsqu'ils sont combines les essais experimentaux donnent un apercu des consequences potentielles de la recolte de la biomasse forestiere sur la regeneration des peuplements et la qualite generale des sols forestiers. [Traduit par la Redaction] Mots-cles: qualite des sols forestiers, compaction, prelevement de la matiere organique, dessouchage, carie de racines.
1. Introduction Mechanization of the forest industry in North America increased through the 1940s, and this prompted a growing concern on the impacts of harvesting techniques on forest soil quality. [...]