Effects of elevated CO2 on growth and carbon/nutrient balance in the deciduous woody shrub Lindera benzoin (L.) Blume (Lauraceae)

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Abstract
We examined the effects of elevated CO2 on growth and carbon/nutrient balance in a natural population of the deciduous temperate zone shrub Lindera benzoin. Our data concern whole plant, leaf, and stem growth for the first two seasons of a long-term field experiment in which CO2 levels were manipulated in situ. In addition to growth parameters, we evaluated changes in leaf and stem chemistry, including total nitrogen, nonstructural carbohydrates, and total phenolics. Over the course of this study, L. benzoin appeared to respond to elevated CO2 primarily by physiological and biochemical changes, with only a slight enhancement in aboveground growth (ramet height). Positive effects on aboveground growth were primarily evident in young (nonreproductive) ramets. Our results suggest that nitrogen limitation may have constrained plants to allocate carbohydrates produced in response to elevated CO2 primarily to storage and belowground growth, and perhaps to increased secondary chemical production, rather than to increased stem and leaf growth. We discuss our results in terms of changes in carbon/nutrient balance induced by elevated CO2, and provide predictions for future changes in this system based upon constraints imposed by intrinsic and extrinsic factors and their potential effects on the reallocation of stored reserves.