Liming and wood-ash addition have long been used to attenuate the effects of acidic deposition on forest soils with the goal of promoting tree growth. We performed quantitative meta-analyses of treatment studies from managed forest ecosystems to assess general tendencies of effects of treatment on seven selected measures of performance thought to reasonably reflect the effects of Ca-addition treatment. We retrieved over 350 independent trials from 110 peer-reviewed liming and wood-ash addition studies that were integrated to determine soil pH, base saturation (BS), tree foliar Ca concentration, tree growth, ectomychorrhizae root colonization, soil C-to-N ratio, and microbial indices. The results were quantified through three separate metaanalysis effect size metrics: unweighted relative values and two weighted metrics, Hedges' d and ln R. A surprising number of treatment trials (22%-85%) reported no significant effect, and soil pH and foliar Ca appeared more responsive to liming than to wood-ash addition, whereas BS and tree growth appeared more responsive to wood-ash addition. For six of the seven parameters, estimated mean effect sizes were similar in magnitude and positive in direction for all three meta-analysis metrics. Regression tree optimal models explained 38% of the variation in pH, 47% of the variation in BS, 51% of the variation in foliar Ca concentration, and 26% of the variation in tree growth. The largest predictors of effect size, within our selected group, were as follows: soil type for pH; soil type, trial duration in years, and species (hardwood or softwood) for BS; treatment dose and type for foliar Ca concentration; and trial duration, initial soil pH, and tree species for tree growth. This analysis shows that Ca additions are not universally beneficial and provides insight into when Ca additions to forest soils are likely to be most effective.Résumé : Le chaulage et l'ajout de cendre de bois sont utilisés depuis longtemps pour atténuer les effets des dépôts acides sur les sols forestiers dans le but de promouvoir la croissance des arbres. Nous avons réalisé des méta-analyses quantitatives des essais de traitement dans des écosystèmes forestiers aménagés dans le but d'évaluer les tendances générales des effets des traitements sur un choix de sept mesures de performance qui devraient raisonnablement refléter les effets d'un apport de Ca. Nous avons retrouvé plus de 350 essais indépendants provenant de 110 études portant sur le chaulage et l'ajout de cendre de bois révisées par les pairs. Ces essais ont été intégrés pour déterminer : le pH du sol, la saturation en bases (SB), la concentration du Ca foliaire des arbres, la croissance des arbres, la colonisation des racines par les ectomycorhizes, le rapport C à N du sol et des indices microbiens. Les résultats ont été quantifiés à l'aide de trois métriques distinctes des méta-analyses ayant trait à l'ampleur de l'effet : les valeurs relatives non pondérées et deux métriques pondérées, d de Hedges et lnR. Un nombre surprenant d'essais de traiteme...

No abstract