Generally, the growth of all forests accelerate as canopies develop as in young forests and declines substantially soon after maximum leaf area is attained. The causes of this decline trend are multiple. However, age and size are normally coupled growth. Therefore, an experimental manipulation has been done to separate the effects of size from those of age by using traditional grafting techniques. Genetically identical grafted seedlings were produced from scions taken from trees of four different age classes ranged from 4 to 162 years. The aim of this study is to investigate the effects of tree age and tree size on growth, physiology and water use of two broadleaf species by conducting three major experiments. Growth characteristics such as relative growth rate and growth efficiency were measured together with leaf-level gas exchanges and sap flow studies. Comparisons were established among results observed in the field with the ones obtained in the grafted seedlings. The results showed that relative growth rate and growth efficiency decreased substantially with increase in age of donor trees in the field. In contrast, these parameters seemed almost constant on grafted seedlings which are scions taken from different meristematic ages did not show the age-related trend after they were grafted onto the rootstocks. Similar patterns were also observed in net photosynthesis from leaf-level gas exchange and sap-flow-based parameters in both species. In general, these results suggested that size limitation to water and nutrient transport to the top of the canopy is a primary cause that triggered the declination in production of photosynthate and reduced growth of the trees, and/or increase in maintenance respiration with increasing in tree size rather than controlled by meristematic age.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:640124 |
| Date | January 2006 |
| Creators | Abdul Hamid, Hazandy |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11231 |
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