Incorporating Plant Hydraulics Into Phenological Modeling

Abstract:

Vegetation phenology is well studied in systems where temperature is the primary driver of change, such as temperate and boreal ecosystems. In order to accurately model phenology in water-limited systems it is necessary to consider the role of water stress on mediating phenology. While it is possible to use proxies for water stress, such as vapor pressure deficit (VPD), it is preferable to have a more direct link to the effects of water stress on plant physiology. One possible approach is to incorporate the physiological responses of plants to water stress into phenological models.  The goal of this study is to examine the use of plant hydraulics to help predict phenology instead of using only meteorological variables. We used an ecosystem process model that incorporates plant hydraulics, the Terrestrial Regional Ecosystem Exchange Simulator (TREES), in order to model plant phenology based on hydraulic stress. Phenology submodels implemented within TREES included both those driven purely from environmental variables as well those modulated by plant hydraulics. Results showed that the use of plant hydraulics to predict phenology, instead of using VPD as a proxy of plant water stress, performed favorably in comparison to models driven by meteorological variables alone. The need for better representation of moisture stress on phenology was particularly apparent in water-limited systems and the inclusion of plant hydraulics into phenology models improved the predictions in these systems.

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