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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 [...]

The reactive form of Aluminum (Al) is mobilized from the mineral soil to the forest-floor soil due to acid deposition. This reactive Al reduces the availability of Calcium (Ca) present in the forest-floor soil to the plants. The Ca uptake by plants decrease as a consequence. The decrease of exchangeable Ca in the upper soil horizon is not accompanied by a change in exchangeable H or soil pH. Dissolution of mineral Al or decomplexation of organic Al are not responsible for the loss of Ca since these does not occur from acid deposition.

The depletion of root-available calcium in northern forests 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 calcium to the rooting zone of trees. This study reports changes in concentrations of Ca, Mg, and K during decay of sapwood of spruce, maple, hemlock, and birch at two locations in northern New England, USA. Concentrations of exchangeable Ca, Mg, and Al in decayed wood residues after 10 and 12 years of ground contact were also compared. Significant loss of mass indicated by decreasing wood density occurred after two to eight years in conifers and after only two years in hardwoods. A significant gain in wood K was observed at two years, but the gain was not sustained. A significant gain in Ca concentration occurred by six years and that gain was sustained for 12 years. Concentrations of Mg varied. 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 molar Al/Ca ratio, a conditional characteristic of sites with high root-available Ca. [ABSTRACT FROM AUTHOR]

Dendrochemical and biochemical markers link stress in apparently healthy red spruce trees (Picea rubens) to acidic deposition. Acidic deposition to spruce forests of the northeastern USA increased sharply during the 1960s. Previous reports related visible damage of trees at high elevations to root and soil processes. In this report, dendrochemical and foliar biochemical markers indicate perturbations in biological processes in healthy red spruce trees across the northeastern USA. Previous research on the dendrochemistry of red spruce stemwood indicated that under uniform environmental conditions, stemwood concentrations of Ca and Mg decreased with increasing radial distance from the pith. For nine forest locations, frequency analysis shows that 28 and 52% of samples of red spruce stemwood formed in the 1960s are enriched in Ca and Mg, respectively, relative to wood formed prior to and after the 1960s. This enrichment in trees throughout the northeastern USA may be interpretable as a signal of increased availability of essential cations in forest soils. Such a temporary increase in the availability of Ca and Mg could be caused by cation mobilization, a consequence of increased acidic deposition. During cation mobilization,essential Ca and Mg as well as potentially harmful Al become more available for interaction with binding sites in the soil and absorbing roots. As conditions which favor cation mobilization continue, Ca andMg can be leached or displaced from the soil. A measure of the interaction between Ca and Al is the Al/Ca binding ratio (molar charge ratio of exchangeable Al to exchangeable Ca). As the Al/Ca binding ratioin the root zone increased from 0.3 to 1.9, the foliar concentrationof the biochemical stress marker putrescine also increased from 45 to 145 nm g-1. The correlation of the putrescine concentration to the Al/Ca binding ratio (adj. r2 = 0.68, P< 0.027) suggests that foliar stress may be linked to soil chemistry. [ABSTRACT FROM AUTHOR]