Factoring in canopy cover heterogeneity on evapotranspiration partitioning: Beyond big-leaf surface homogeneity assumptions

Excerpt

The vast majority of water on Earth's terrestrial surface is lost through evapotranspiration (ET; vaporization processes that include evaporation [E] of intercepted water, E from free-water surfaces, and transpiration [T] from vegetation [Savenije 2004]) (Jasechko et al. 2013). Management and conservation of water resources require explicit understanding of ET, particularly due to the potential for global change to alter water fluxes. Although mostly considered by its hydrological nature, ET is the result of a suite of both physical and biological processes interacting at multiple spatial and temporal scales (Jarvis 1995) and constitutes a key driver of ecosystem function via the effects of T on ecosystem water and energy balance, impacting productivity (Jackson et al. 2001).

During the twentieth century, important empirical and theoretical models that described ET based on its physical drivers—particularly relevant to agriculture and water resource management—as well as sophisticated measurement techniques relevant to local scales were developed (Shuttleworth 2007). Although vegetation is acknowledged to strongly influence ET, theories that explicitly considered vegetation applied generally to two extreme cases: bare or fully vegetated soil (Shuttleworth 2007; Caylor et al. 2005). Widely used empirical models for ET, mostly derived from the Penman-Montheith equation (Montheith 1965), use a simplifying assumption…