Water availability and forest growth in coarse-textured soils

Abstract

Huang, M., Barbour, S. L., Elshorbagy, A., Zettl, J. D. and Si, B. C. 2011. Water availability and forest growth in coarse-textured soils. Can. J. Soil Sci. 91: 199–210. A method of evaluating the influence of soil layering and climatic variability on plant available water for forest growth is presented. This method enables species-specific levels of maximum sustainable plant transpiration to be evaluated. A calibrated HYDRUS-1D model was used with a 60-yr meteorological record to simulate actual evapotransipration (ETa) of dominant tree species with different values of leaf area index (LAI) for three sites in northern Alberta. A probability distribution of ETa was developed for each case. The relationships between LAI, plant above-ground primary production (ANPP), and ETa were used to estimate the minimum water demand to support plant growth at specific sites. The developed frequency curves of ETa and the minimum water demand can be used to determine the maximum sustainable LAI and the risk associated with revegetating a particular site with a dominant tree species. The effect of different tree species on the minimum water demand and the maximum sustainable LAI was also illustrated. The results indicated that layering of coarse-textured soils can provide more plant available water and support a higher maximum sustainable LAI than homogeneous soils of a similar texture.

Inverse estimation of soil hydraulic properties and water repellency following artificially induced drought stress

“…The potential root water uptake was calculated taking into account seasonal dynamics of LAI and interception of the canopy at the forest sites (beech trees). A constant rooting depth (75 cm) with a root distribution adapted from Huang et al (2011) was assumed. Effective precipitation was further calculated by subtracting losses due to interception from gross precipitation.…”

Simulations of freshwater lens recharge and salt/freshwater interfaces using the HYDRUS and SWI2 packages for MODFLOW

“…Actual root water uptake, appearing as a source term in the Richards equation, is obtained by multiplying potential root water uptake using a stress response function, which in turn depends on the soil water pressure head. For our simulations we used a simplification of the well-known stress response function of Feddes et al (1978), as given by Huang et al (2011). Resulting values of root water uptake are either equal to or smaller than the potential root water uptake.…”

“…While both of these cases were significant simplifications of reality, they can be considered as indicators for the possible range of variability of recharge for a varying soil cover by vegetation. We assumed that the depth of the root zone was 2 m, with the root density distribution decreasing linearly from a maximum value at the soil surface to zero at a depth of 2 m. For the stress response function, which describes the reduction in water uptake due to decreasing pressure heads in unsaturated soil, we used the model of Huang et al (2011), which is a simplified version of the well-known formulation by Feddes et al (1978). In this approach, root water uptake is assumed to be maximum for pressure heads larger than h 1 (equal to -3 m in our study), zero for pressure heads less than the wilting point (assumed at h 2 = -150 m), and changing linearly for pressure heads between these two values.…”

Using Sap Flow Data to Parameterize the Feddes Water Stress Model for Norway Spruce

“…Huang et al [75] set h 3 to the root-zone h at a SWC of 27.5% of the SWC at field capacity. This corresponds to the mean critical SWC they reviewed from different studies on drought-stress in evergreen tree species.…”