Sensitivity study of the influence of changes in canopy characteristics on evaporation loss and soil moisture using a sparse vegetation model

Abstract

It is found that soil surface evaporation from moist soils is an important component of the total evaporative loss in very sparse canopies [LAI (leaf area index) below 0.5]. With LAI values below ca 0.5, and moist soils, canopy stomatal controls are not strongly influencing total evaporative loss. In contrast, there is a tendency for 10-day average transpiration loss to become constant with increasing LAI for LAI values above ca 2. The model is also used for sensitivity studies on the influence of small changes in bracken canopy characteristics (bulk canopy resistance, LAI and height) on evaporative loss and soil moisture. It is found that the percentage change in transpiration loss is always less than the percentage change in canopy characteristics. This is particularly so in the case of bulk canopy resistance. Year-to-year variations in weather inputs are likely to swamp small changes in canopy characteristics due to either long-term climatic changes or errors in field parameterizations. -from Author