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Factors modulating cottongrass seedling growth stimulation to enhanced nitrogen and carbon dioxide: compensatory tradeoffs in leaf dynamics and allocation to meet potassium-limited growth
Auteur(s)
Siegenthaler, Andy
Buttler, Alexandre
Grosvernier, Philippe
Nilsson, Mats B.
In
Oecologia, 2013/171/2/557-570
Résumé
<i>Eriophorum vaginatum</i> is a characteristic species of northern peatlands and a keystone plant for cutover bog restoration. Understanding the factors affecting <i>E. vaginatum</i> seedling establishment (i.e. growth dynamics and allocation) under global change has practical implications for the management of abandoned mined bogs and restoration of their C-sequestration function. We studied the responses of leaf dynamics, above- and belowground biomass production of establishing seedlings to elevated CO<sub>2</sub> and N. We hypothesised that nutrient factors such as limitation shifts or dilutions would modulate growth stimulation. Ele vated CO<sub>2</sub> did not affect biomass, but increased the number of young leaves in spring (+400 %), and the plant vitality (i.e. number of green leaves/total number of leaves) (+3 %), both of which were negatively correlated to [K<sup>+</sup>] in surface porewater, suggesting a K-limited production of young leaves. Nutrient ratios in green leaves indicated either N and K co-limitation or K limitation. N addition enhanced the number of tillers (+38 %), green leaves (+18 %), aboveground and belowground biomass (+99, +61 %), leaf mass-to-length ratio (+28 %), and reduced the leaf turnover (−32 %). N addition enhanced N availability and decreased [K<sup>+</sup>] in spring surface porewater. Increased tiller and leaf production in July were associated with a doubling in [K<sup>+</sup>] in surface porewater suggesting that under enhanced N production is K driven. Both experiments illustrate the importance of tradeoffs in <i>E. vaginatum</i> growth between: (1) producing tillers and generating new leaves, (2) maintaining adult leaves and initiating new ones, and (3) investing in basal parts (corms) for storage or in root growth for greater K uptake. The K concentration in surface porewater is thus the single most important factor controlling the growth of <i>E. vaginatum</i> seedlings in the regeneration of selected cutover bogs.
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journal article
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