Article

Photosynthetica

, Volume 36, Issue 4, pp 575-586

First online:

A Cost-Benefit Analysis of Leaves of Eight Australian Savanna Tree Species of Differing Leaf Life-Span

  • D. EamusAffiliated withSchool of Biological and Environmental Sciences, Northern Territory UniversityNTU, CRC for Sustainable Development of Tropical Savannas
  • , B. MyersAffiliated withSchool of Biological and Environmental Sciences, Northern Territory University
  • , G. Duff
  • , R. WilliamsAffiliated withNTU, CRC for Sustainable Development of Tropical SavannasCSIRO, Tropical Ecosystems Research Centre, Division of Wildlife and Ecology

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Abstract

Cost-benefit analysis of foliar construction and maintenance costs and of carbon assimilation of leaves of differing life-span were conducted using two evergreen, three semi-deciduous, and three deciduous tree species of savannas of north Australia. Rates of radiant-energy-saturated CO2 assimilation (P max) and dark respiration were measured and leaves were analysed for total nitrogen, fat, and ash concentrations, and for heat of combustion. Specific leaf area, and leaf N and ash contents were significantly lower in longer-lived leaves (evergreen) than shorter-lived leaves (deciduous) species. Leaves of evergreen species also had significantly higher heat of combustion and lower crude fat content than leaves of deciduous species. On a leaf area basis, P max was highest in leaves of evergreen species, but on a leaf dry mass basis it was highest in leaves of deciduous species. P max and total Kieldahl N content were linearly correlated across all eight species, and foliar N content was higher in leaves of deciduous than evergreen species. Leaf construction cost was significantly higher and maintenance costs were lower for leaves of evergreen than deciduous species. Maintenance and construction costs were linearly related to each other across all species. Leaves of evergreen species had a higher cost-benefit ratio compared to leaves of deciduous species but with longer lived leaves, the payback interval was longer in evergreen than deciduous species. These results support the hypotheses that longer lived leaves are more expensive to construct than short-lived leaves, and that a higher investment of N into short-lived leaves occurs which supports a higher P max over a shorter payback interval.

ash deciduous and evergreen trees fat Heat of combustion maintenance and construction costs nitrogen content photosyntethic rate specific leaf area