Modeling the effects of plant-interspace heterogeneity on water-energy balances in a semiarid ecosystem

• We modeled the water-energy balances of a semiarid ecosystem.
• The model integrated plant-interspace interactions with vertical exchange processes.
• The water-energy budgets differed strongly at the shrub cover and interspace.
• The plant-interspace interactions showed mixed effects on the water use of shrubs.

Close interactions of water-energy conditions at plant cover and interspace are so far largely overlooked in water-energy modeling for dryland ecosystems. This study focused on (i) introducing the plant-interspace heterogeneity into water-energy modeling for a dryland ecosystem, and (ii) investigating the influences of such heterogeneity on the ecosystem water-energy budgets. The plant-interspace heterogeneity was described using a two dimensional scheme. The soil-vegetation-atmosphere transportation processes were integrated with horizontal exchanges of water and energy. The model was parameterized and validated by field observations (Yanchi, China). The modeled sensible and latent heat fluxes were stronger at the shrub cover (SCA) compared to interspace, but soil surface was cooler. Moreover, the water-energy advections between the interspace and SCA showed mixed effects on the simulated water-energy budget of the ecosystem. The aboveground advections significantly enhanced the evapotranspiration rate at SCA. The root uptake and horizontal inflows from the interspace amounted to over 40% of the annual water loss from SCA, resulting in a tight water budget at ecosystem level. These results emphasized the necessity of considering the plant-scale heterogeneities and horizontal processes in estimating water-energy balances in such ecosystems. Our model can serve as a tool to simulate the water-energy dynamics in sparse-vegetated ecosystems regarding such interactions.