Minimum leaf water potential has been found to be rather constant in coniferous species over a range of environmental conditions and developmental stages. Such a functional homeostasis requires the balanced growth of transpiring foliage, absorbing roots and conductive sapwood, with profound implications for resource allocation, plant allometry and productivity. Although central to the maintenance of plant structure, the process of growth allocation is still poorly understood. The observation of a functional homeostasis in water transport has led to formulate a novel hypothesis of optimal plant growth under hydraulic constraints. The hypothesis has been tested against field and literature data of forest function and growth, choosing <I>Pinus sylvestris </I>as a model coniferous species. The newly developed hypothesis delineates a common framework that seems to explain conveniently changes in growth allocation both over the lifetime of the plant and in response to the environment, helping to explain the variability in forest growth observed at the regional scale as well as the age-related decline in forest productivity. A detailed process model of forest growth (HYDRALL) was developed, centered on the hypothesis of optimal carbon allocation under hydraulic constraints, and applied to the prediction of <I>P. sylvestris </I>growth patterns across Europe. The model was found to predict conveniently several of the growth patterns reported in the literature. Changes in carbon allocation were found to be most important under dry conditions. Information on root hydraulic characteristics under natural conditions is scarce. Part of the research effort was therefore devoted to the development of a new technique for the measurement of the hydraulic resistance of entire root systems of soil-grown plants, a parameter central to the newly developed model.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:657193 |
| Date | January 1999 |
| Creators | Magnani, Federico |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12544 |
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