Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 366195
Title Water use of tree lines: importance of leaf area and micrometeorology in sub-humid Kenya
Author(s) Radersma, S.; Ong, C.K.; Coe, R.
Source Agroforestry Systems 66 (2006)3. - ISSN 0167-4366 - p. 179 - 189.
Department(s) PPO Arable Farming, Multifunctional Agriculture and Field Production of Vegetables
Sub-department of Soil Quality
Publication type Refereed Article in a scientific journal
Publication year 2006
Keyword(s) eucalyptus-grandis trees - pinus-radiata - soil-water - growth - transpiration - model - stand - evaporation - simulation - efficiency
Abstract In this research the relative importance of leaf area and microclimatic factors in determining water use of tree lines was examined in sub-humid Western Kenya. Measurements of tree water-use by a heat-balance technique, leaf area, bulk air saturation deficit, daily radiation, and soil water content were done in an experiment with tree lines within crop fields. The tree species were Eucalyptus grandis W. Hill ex Maiden, Grevillea robusta A. Cunn. and Cedrella serrata Royle, grown to produce poles on a phosphorus-fixing Oxisol/Ferralsol with (+P) or without (-P) phosphorus application. Doubling the leaf area of Cedrella and Grevillea doubled water use in a leaf area (LA) range of 1-11 m(2) per tree. The response of Eucalyptus water use (W) to increases in leaf area was slightly less marked, with W = LA(n), n <1. Transpiration rate per unit leaf area (Tr) was the other important determinant of water use, being affected by both tree species and phosphorus fertilization. A doubling of the saturation deficit (SD) halved the water use of all trees except for Cedrella +P, in which water use increased. A direct effect of soil water content on water use was only found in Grevillea -P, with a small increase (60%) as available water increased from 1.4 to 8.9% above wilting point (32%). This low direct response to soil water content is probably due to the extensive tree-root systems and the deep clayey soils supplying sufficient water to meet the evaporative demand. Indirect responses to soil water content via decreases in leaf area occurred in the dry season. The results showed that water use of tree lines was more determined by leaf area and transpiration rate per unit leaf area than by micro meteorological factors. The linear response of tree water use to leaf area, over a wide range leaf areas, is a specific characteristic of tree line configurations and distinguished them from forest stands. In tree lines light interception and canopy conductance increase with leaf area much more than a similar leaf area increase would have caused in a closed forest canopy.
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