Plant drought tolerance trait is the key parameter in improving the modeling of terrestrial transpiration in arid and semi-arid regions

The prediction of precipitation depends on accurate modeling of terrestrial transpiration. In recent decades, the trait-based plant hydraulic stress scheme has been developed in land surface models, in order to better predict the hydraulic constraint on terrestrial transpiration. However, the role that each plant functional trait plays in the modeling of transpiration remains unknown. The importance of different plant functional traits for modeled transpiration needs to be addressed. Here, the Morris sensitivity analysis method was implemented in the Common Land Model with the plant hydraulic stress scheme (CoLM-PHS). Traits related to drought tolerance (P-50), stomata, and photosynthesis were screened as the most critical from all 17 plant traits. Among 12 FLUXNET sites, the importance of P-50, measured by normalized sensitivity scores, increased towards lower precipitation, whereas the importance of stomatal traits and photosynthetic traits decreased towards drier climate conditions. P-50 was more important than stomatal traits and photosynthetic traits in arid or semi-arid sites, which implies that hydraulic safety strategies are more crucial than plant growth strategies when plants frequently experience drought. Large variation in drought tolerance traits further proved the coexistence of multiple plant strategies of hydraulic safety. Ignoring the variation in drought tolerance traits may potentially bias the modeling of transpiration. More measurements of drought tolerance traits are therefore necessary to help better represent the diversity of plant hydraulic functions.