Longer Leaf Life Span Research Articles

This study compared how two tree species with different leaf life-spans differ in their adaptations to low nutrient availability in a Wisconsin bog. Seasonal patterns of foliar nutrient concentration, nutrient resorption, leaching loss to simulated rainfall, and growth efficiency were determined for Larix laricina and Picea mariana during 1983 and 1984. Concentrations of foliar nitrogen and phosphorus in Larix leaves increased slightly during summer; this was followed by strong autumnal resorption. Calcium concentration of Larix leaves increased throughout the entire life-span of the leaves. Concentrations of nitrogen and phosphorus were highest in new (age-class 0) Picea leaves and declined with each successive leaf age-class, whereas calcium leaves increased in older leaf age-classes. Winter–spring resorption of nitrogen and phosphorus occurred from all age-classes of Picea leaves; this was followed by a summer increase in foliar nutrient concentrations. Resorption of nitrogen was greater in Larix than in Picea. There were no significant differences in phosphorus resorption or nutrient growth efficiencies between species. Foliar nutrient losses to leaching by artificial rainwater were less than 1% of the total foliar nutrient content. As there was no significant difference in the relative growth rates or growth efficiencies between the two species, the persistence of deciduous Larix in nutrient-poor bogs among species with longer leaf life-spans might be linked to its greater nitrogen conservation.

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