Forest Management and Tree-Ring Isotopes

Abstract

AbstractForest management can be improved by the mechanistic understanding that tree-ring stable isotopes provide. Key management tools include genetic selection, competing vegetation control, thinning, and fertilization. These tools frequently change environmental conditions and physiological processes, such as photosynthesis, stomatal conductance, water uptake, and nitrogen cycling, which may leave isotopic signatures in tree-rings, providing detailed responses to management over decadal time periods. While data sets remain small, some trends have emerged from previous forest management studies using stable isotopes. Genotype selection sometimes shows isotopic evidence of maladaptation, especially in the presence of climate change. Competition control and thinning have different isotopic reactions depending on the dryness of the site; they generally obtain different responses depending on whether competition is primarily for aboveground (light) or belowground (water and nutrient) resources. Fertilization responses recorded in tree rings appear to be driven by initial increases in photosynthesis, and later by increases in leaf area index. Tree-ring isotopic applications can provide key insights to a much broader range of silvicultural objectives than included here, and we encourage their application in large-scale silvicultural experiments to reduce uncertainties and explain mechanisms of response. In future work, we suggest that management studies wishing to utilize tree-ring stable isotopic analysis include key ancillary measurements, especially leaf nitrogen concentrations, leaf-area index, xylemwater sources, and canopy temperature, to help support interpretation of the isotopic data.