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Revista chilena de historia natural

Print version ISSN 0716-078X

Abstract

LUSK, CHRISTOPHER H.. Leaf life spans of some conifers of the temperate forests of South America. Rev. chil. hist. nat. [online]. 2001, vol.74, n.3, pp.711-718. ISSN 0716-078X.  http://dx.doi.org/10.4067/S0716-078X2001000300017.

Interspecific variation in leaf life span has wide-ranging implications for plant species sorting on resource availability gradients, and for ecosystem processes such as nutrient cycling. Very little is known about leaf life spans of evergreen trees in the temperate forests of South America. Leaf life spans were estimated by static demographic methods, and associated leaf traits measured, for four conifers of this region. It was expected that leaf life span variation would correlate negatively with soil fertility of habitats normally occupied by each species. This prediction was upheld by the data. The mean leaf life span determined for Araucaria araucana (24 years) is among the highest figures reported for any plant species. This extreme leaf longevity was associated with very robust construction (high leaf mass per unit area) and very low nitrogen content. These aspects of the ecology of A. araucana may affect its fitness in two ways. Firstly, slow foliage turnover will reduce its annual nutrient requirements for crown maintenance, a trait that is thought to be crucial for survival on nutrient-poor sites. Secondly, the low decomposability of A. araucana leaf litter is likely to cause nutrient immobilisation, possibly favouring site retention by A. araucana in the face of competition from faster-growing but more nutrient-demanding species. Interspecific variation in leaf life span appeared to be systematically related to variation in leaf mass per unit area (LMA) and leaf nitrogen, in agreement with a large body of evidence that leaf evolution is constrained by a trade-off between trait combinations which optimise carbon gain and growth in resource-rich habitats, and those which favour persistence in chronically adverse environments

Keywords : Araucaria araucana; leaf longevity; leaf nitrogen; Podocarpus; resource gradients; specific leaf area.

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