Thinning and nitrogen fertilization effects on soil and tree water stress in a Douglas-fir stand

1986 ◽  
Vol 16 (6) ◽  
pp. 1334-1338 ◽  
Author(s):  
H. Brix ◽  
A. K. Mitchell
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Nitrogen Fertilization ◽  
Soil Water Potential ◽  
Early Morning ◽  
Douglas Fir ◽  
Fertilization Effect ◽  
Use Efficiency ◽  
Soil Water Conditions ◽  
Fertilization Effects

Soil and tree water potentials were studied over a 10-year period in a Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand that was treated when 24 years old with different thinning and nitrogen fertilization regimes. Throughout the 10-year period, thinning increased the soil water potential during the dry summer periods (July–September) by as much as 1 MPa both with and without fertilization. Fertilization effect on soil water potential was slight and only apparent in the latter part of the study in spite of large increases in leaf area (50% after 7 years) possibly because of better stomatal control of water loss. Fertilization increased water use efficiency. The favorable soil water conditions produced by thinning led to improved shoot water potential only during predawn and early morning. Removal of understory in a thinned and fertilized plot did not affect soil or shoot water potential.

Needle water potential and soil-to-foliage flow resistance during soil drying: a comparison of Douglas-fir, western hemlock, and mountain hemlock

1985 ◽  
Vol 15 (1) ◽  
pp. 185-188 ◽  
Author(s):  
T. M. Ballard ◽  
M. G. Dosskey
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Flow ◽  
Flow Resistance ◽  
Soil Water Potential ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Soil Drying ◽  
Experimental Conditions ◽  
Needle Water Potential

Needle water potential in western and mountain hemlock falls as the soil dries, but under our experimental conditions, it remained stable in Douglas-fir. Resistance to water flow from soil to foliage is higher for the hemlocks and increases more steeply as the soil dries. These findings physically account for the observation that water uptake is reduced relatively more for the hemlocks than for Douglas-fir, as soil water potential declines.

Soil and plant resistance effects on transpirational and leaf water responses by groundnut to soil water potential

Soil Research ◽  
1981 ◽  
Vol 19 (1) ◽  
pp. 51 ◽  
Author(s):  
RP Samui ◽  
S Kar
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Uptake ◽  
Plant Resistance ◽  
Sandy Loam ◽  
Soil Water Potential ◽  
Leaf Water ◽  
Arachis Hypogea ◽  
Water Potentials ◽  
Soil Water Conditions

The phasic and diurnal leaf water potential (�L) and transpirational responses to soil water potential by groundnut (Arachis hypogea L.) were investigated under controlled soil water conditions in a glasshouse. Three different soil water potentials (�s) in the tensiometric ranges were maintained in a lateritic sandy loam soil (Oxisol) during the seedling (S1), branching (S2) and peg formation (S3) stages of groundnut. Measured values of �s, �L rooting density, soil capillary conductivity and transpiration rate were used to calculate the soil and plant resistances to water uptake by the plant. The soil and plant resistances to water uptake by the groundnut plant increased appreciably as the soil water potential decreased from -0.11 to -0.70 bar. Plant resistance (Rp) was two to three orders of magnitude higher than soil resistance (Rs). Rs decreased with growth of the plant, whereas Rp increased, especially at -0.7 bar �s, Decreases in transpiration at �s lower than -0.33 bar were closely associated with the increases in the plant and soil resistances, and with lower leaf water potentials.

Effects of salal understory removal on photosynthetic rate and stomatal conductance of young Douglas-fir trees

1986 ◽  
Vol 16 (1) ◽  
pp. 90-97 ◽  
Author(s):  
D. T. Price ◽  
T. A. Black ◽  
F. M. Kelliher
Keyword(s):  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential ◽  
Vapour Pressure Deficit ◽  
Basal Area ◽  
Douglas Fir ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Data Set

The effects of salal (Gaultheriashallon Pursh.) understory removal on the growth of thinned 32-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees were determined in a stand subject to growing season soil water deficits. Four pairs of similar trees were selected and the understory was completely removed from around one of each pair, the root zones of which were both isolated using plastic sheeting buried to bedrock. Photosynthesis, stomatal conductance, soil water potential and canopy microclimate were measured intensively in one pair on 4 clear days during an extended dry period in June 1982. Basal area increment of the four pairs of trees was measured over three growing seasons. To determine the effect of soil water potential on tree photosynthesis, the same variables were intensively measured over 3 consecutive days in late August 1982 for another tree initially subjected to a soil water potential of approximately −1.6 MPa, but irrigated to approximately −0.02 MPa between the 1st and 2nd days. Solar irradiance decreased markedly between the 2nd and 3rd days, thereby creating a unique data set. Findings were as follows: (i) removal of understory significantly increased rates of photosynthesis in the trees, both diurnally and seasonally, (ii) photosynthesis was not generally limited by stomatal conductance unless vapour pressure deficit was high and photon flux density was saturating, and (iii) tree growth response to salal removal was due to higher soil water potential, which increased both photosynthetic capacity and stomatal conductance.

Effect of Soil Water Potential of Two Soils on Soybean Emergence 1

1979 ◽  
Vol 71 (6) ◽  
pp. 980-982 ◽  
Author(s):  
L. G. Heatherly ◽  
W. J. Russell
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Soil Water Potential
Sign in / Sign up

Export Citation Format

Share Document