TREE-RING-BASED GROWTH ANALYSIS FOR A SUGAR MAPLE STAND - RELATIONS TO LOCAL CLIMATE AND TRANSIENT SOIL PROPERTIES

Tree-ring-based growth analysis often suffers from lack of concurrent climate and soil data. This study used (i) regressions to adjust weather records for local conditions, (ii) climate-driven simulation models to simulate soil moisture and temperatures, and (iii) site-specific regression models to reconstruct ion concentrations in soil solution for the past 40 years. A standardized tree-ring index was used to measure tree radial growth. The study site was a sugar maple (Acer saccharum Marsh.) dominated deciduous stand in Ontario (Turkey Lakes). Based on reconstructed data, when only climate factors were used, 63% of the year-to-year variation in growth index was explained by (i) precipitation during the growing season, and (ii) air temperatures in midwinter, during the growing season, and prior to autumnal leaf fall. The proportion of explained variance was raised to 83% when (i) precipitation was replaced with soil water content, and (ii) soil solution nitrate concentrations in August and in the preceding recuperating season were incorporated. Hence, introducing transient soil properties into tree-ring based growth analysis may substantially reduce error variance; climatic effects on tree growth depend largely on specific, season-dependent responses of transient soil properties.