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The depletion of root-available Ca in northern forest soils exposed to decades of increased acid deposition adversely affects forest health and productivity. Laboratory studies indicated the potential of wood-decay fungi to restore lost Ca. This study presents changes in concentration of Ca, Mg, and K in sapwood of red spruce (Picea rubens Sarg.), red maple (Acer rubrum L.), eastern hemlock (Tsuga canadensis (L.) Carriere), and paper birch (Betula papyrifera Marshall) during the decay process at two experimental forests for 12 years and to compare concentrations of exchangeable Ca, Mg, and Al in decayed wood residues at 10 and 12 years with those in the forest floor. Significant loss of mass indicated by decreasing wood density occurred after 2-8 years in conifers and after only 2 years in hardwoods. A significant gain in wood K was observed at 2 years followed by a significant loss at 8 years. A negligible gain in Ca concentration occurred at 2 years and a substantial gain at 8 years. Observed changes in Mg concentration were variable. No significant difference in exchangeable Ca concentration was observed between decayed wood residue of spruce and maple and the forest floor. However, decayed wood residue had a much lower Al concentration and molar Al/Ca ratio, a condition characteristic of sites with high root-available Ca. Resume: La diminution du Ca disponible pour les racines dans les sols des forets nordiques exposees a plusieurs decennies de depots acides accrus affecte la sante et la productivite de la foret. Des etudes en laboratoire ont montre que les champignons de carie du bois avaient la capacite de restaurer le Ca perdu. Cette etude presente l'evolution de la concentration de Ca, Mg et K dans le bois d'aubier de l'epinette rouge (Picea rubens Sarg.), de l'erable rouge (Acer rubrum L.), de la pruche du Canada (Tsuga canadensis (L.) Carriere) et du bouleau a papier (Betula papyrifera Marshall) durant le processus de decomposition dans deux forets experimentales pendant 12 ans et compare les concentrations de Ca, Mg et Al echangeables dans les debris ligneux apres 10 et 12 ans a celles qu'on retrouve dans la couverture morte. Une perte importante de masse, comme le revele la diminution de la densite du bois, est survenue apres 2 a 8 ans chez les coniferes et apres seulement deux ans chez les feuillus. Un gain important en K dans le bois a ete observe apres 2 ans suivi par une perte importante apres 8 ans. Un gain negligeable dans la concentration de Ca est survenu apres 2 ans suivi d'un gain substantiel apres 8 ans. Les changements observes dans la concentration de Mg etaient variables. Aucune difference significative n'a ete observee dans la concentration de Ca echangeable entre les debris ligneux caries d'epinette, d'erable et la couverture morte. Cependant, les debris ligneux caries avaient une concentration en Al et un rapport molaire Al/Ca beaucoup plus faibles, une situation caracteristique des stations ou la disponibilite de Ca pour les racines est elevee. [Traduit par la Redaction], Introduction Calcium is the fifth most abundant element in the earth's crust. Other than N, Ca is considered the most important essential mineral for managing plant diseases (Rahman and Punja [...]

Abstract: The decay of coarse woody debris is a key component in the formation of forest soil and in the biogeochemical cycles of Ca and Mg. We tracked changes in [...]