| title: | Implication of environmental and plant hydraulic constraints in water relations and canopy structure of woody species |
|---|---|
| reg no: | ETF5296 |
| project type: | Estonian Science Foundation research grant |
| subject: |
1.14. Ecology 4.3. Sylviculture, Forestry |
| status: | completed |
| institution: | University of Tartu |
| head of project: | Arne Sellin |
| duration: | 01.01.2002 - 31.12.2005 |
| description: | The relationships between leaf performance within an individual crown and traits of the plant hydraulic architecture are still poorly understood. Both stomatal conductance and light-saturated photosynthetic capacity exhibit a declining trend with the decrease in light availability from the top to the bottom of the canopy, and it is generally accepted that leaf formation and branch growth at the base of the live crown are limited by low irradiance, i.e. by light competition. Therefore, death of lower branches and vertical crown recession are a common feature in trees of closed-canopy stands. We hypotesize that the leaves growing on lower long branches, characterized by small radial incre-ments and containing smaller vessels, could be hydraulically constrained, although this effect does not reflect in leaf water potentials. Differences in water supply between the leaves attached to upper and lower branches are probably offset by sensitive stomatal control over the transpirational water losses. Thus, we propose that survival of lower branches and the height of the bottom of the live crown and, consequently, the canopy thickness depend on trees' hydraulic properties. Plant water relations, hydraulic characteristics and canopy structure of woody species will be examined under natural conditions depending on light availability within a stand. We are going to verify an alternative mechanism to explain death of the lower branches and shift of the live crown base upward with stand deve-lopment. One shade tolerant (Picea abies (L.) Karst. or Tilia cordata Mill.) and intolerant species (Betula pendula Roth) will be chosen for sampling. The objectives of the project are to a) test the hypothesis that stomatal conductance at the base of the live crown is constrained not only by low light availability but also by inner hydraulic limitations; b) elucidate the contribution of different factors (sapwood cross-sectional area to leaf area ratio, specific conductivity of xylem) to putative hydraulic constraints; c) estimate the effects of environmental versus hydraulic factors on water relations of the species of different shade tolerance. |
| project group | ||||
|---|---|---|---|---|
| no | name | institution | position | |
| 1. | Priit Kupper | Estonian Agricul-tural University | ichthyopatholo-gist | |
| 2. | Marek Sammul | Estonian Agricul-tural University | elder laboratory assistant | |
| 3. | Arne Sellin | University of Tartu, Faculty of Biology and Geography | docent | |