Maxim
Shoshany

Water Use Efficiency (WUE) is a critical property linking climate conditions and productivity in Water Limited Ecosystems. The following new Pattern Water Use Efficiency (PWUE) parameterization extends the WUE concept from the leaf and Plant level to the areal level representing the effect of shrub patch patterns properties on water utilization by plants:
Where,
PWUE = Sc^{[1+ (1-Sc) 1/h Er]}

1. PWUE is directly proportional to Shrub cover; i.e., the amount of rain intercepted by the shrub area;
2. Edge effects represented by the Edge Ratio (Figure 1) at the soil shrub interface represent the decrease in the productive use of water due to heating from neighboring bare soil areas, while this effect is inversely related to the Shrub Cover and to the Shrubs’ Height (h).

Implementation of Cellular Automata simulation allowed assessment of PWUE change along full process cycles for different shrubs growth and spread strategies. Mutual relationships between shrubs growth strategies and Shrubs’ height on PWUE are inferred (Figure 2).

The following expression facilitated then estimation of Shrublands Biomass from PWUE using satellite data:

Shrublands’ Biomass = MAP x Sc^{[1+ (1-Sc) 0.65/NDVI Er]}

Where: MAP is the Mean Annual Precipitation, and where Shrubs’ Height (h ) was replaced by NDVI, and Biomass mapping based on this model using Landsat TM image of the Mediterranean to Arid Gradient in Central Israel was validated by comparison with estimations from allometric calculations as derived from high-resolution air-photographs (Figure 3).

References:

1. Shoshany, M., 2012a, The Rational Equation of Pattern, Precipitation and Biomass Relationships in semi-arid Shrublands, J. of Arid Environments. 78, 179-182
2. Shoshany, 2013, “Water Use Efficiency, patch pattern properties and biomass in shrublands across Mediterranean climatic gradient”. International Workshop on: Eco-hydrology of semi-arid environments http://www.geog.bgu.ac.il/eco-hyd/
3. Shohany, M., 2012, “Mapping Shrublands’ Biomass along climatic gradient with remote sensing methods representing Water Use Efficiency”. Int. Conference: Drylands, Deserts & Desertification, Sde Boqer, Israel.