Trade-offs between the persistence of foliage and productivity in two<Emphasis Type="Italic"> Pinus</Emphasis> species |
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Authors: | C R Warren M A Adams |
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Institution: | (1) Department of Botany, University of Western Australia, Nedlands, WA 6907, Australia e-mail: cwarren@cyllene.uwa.edu.au Tel.: +61-89380-7924, Fax: +61-89380-7925, AU |
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Abstract: | We investigated interspecific variation in leaf lifespan (persistence) and consequent differences in leaf biochemistry, anatomy,
morphology, patterns of whole-tree carbon allocation and stand productivity. We tested the hypothesis that a species with
short-lived foliage, Pinus radiata D. Don (mean leaf lifespan 2.5 years), grows faster than P. pinaster Ait., a species with more persistent foliage (leaf lifespan 5.6 years), and that the faster growth rate of P. radiata is associated with a greater allocation of nitrogen and carbon to photosynthetic tissues across a range of scales. In fully
sunlit foliage, the proportion of leaf N in the major photosynthetic enzyme Rubisco (ribulose-1, 5-bisphosphate carboxylase) was greater in P. radiata than in P. pinaster, and, in mid-canopy foliage, the proportion of leaf N in thylakoid proteins was greater in P. radiata. A lesser proportion of needle cross-sectional area was occupied by structural tissue in P. radiata compared to P. pinaster. Foliage mass in stands of P. radiata was 9.7 t ha–1 compared with 18.2 t ha–1 in P. pinaster while leaf area index of both species was similar at 4.6 m2 m–2, owing to the compensating effect of differences in specific leaf area. Hence trade-offs between persistence and productivity
were apparent as interspecific differences in patterns of whole-tree carbon allocation, needle morphology, anatomy and biochemistry.
However, these interspecific differences did not translate into differences at the stand scale since rates of biomass accumulation
were similar in both species (P. radiata 6.9±0.9 kg year–1 tree–1; P. pinaster 7.4±0.9 kg year–1 tree–1). The similarities in performance at larger scales suggest that leaf area index (and radiation interception) determines growth
and productivity.
Received: 13 July 1999 / Accepted: 31 January 2000 |
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Keywords: | Pinus Leaf longevity Foliage productivity Nitrogen Specific leaf area |
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