Chin J Plant Ecol ›› 2011, Vol. 35 ›› Issue (4): 411-421.DOI: 10.3724/SP.J.1258.2011.00411

• Research Articles • Previous Articles     Next Articles

Use of storage water in Larix principis-ruprechtii and its response to soil water content and potential evapotranspiration: a modeling analysis

SUN Lin, XIONG Wei, GUAN Wei, WANG Yan-Hui*(), XU Li-Hong   

  1. Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Key Laboratory of Forest Ecology and Environmental Sciences of State Forestry Administration, Beijing 100091, China
  • Received:2010-11-12 Accepted:2011-01-04 Online:2011-11-12 Published:2011-04-13
  • Contact: WANG Yan-Hui

Abstract:

Aims Water stored in the secondary xylem of the sapwood of large trees is not only a source for transpiration, but also may help avoid xylem cavitation and subsequent failure of water transfer in xylem. Our objective was to study the dynamics of tree water storage and use in order to understand the response mechanism of trees to water stress.
Methods A model simulating the diurnal pattern of water transfer within stems was designed. It combines a non-steady-state hydraulic model with a transpiration model that was based upon the Penman-Monteith equation and a Jarvis-type representation of the stomatal resistance including xylem conduct water potential (ψhx), vapor pressure deficit (Ds) and photosynthetically active radiation (IP). The combined model simulates the diurnal variation of water uptake, storage flow and transpiration rate directly from environmental variables. We simulated the sap flow of Larix principis-ruprechtii, which is planted in Diediegou catchments on the north sides of the Liupan Mountains, and analyzed the relationship between storage water use and environmental factors.
Important findings The hydraulic model accurately simulated diurnal patterns of measured sap flow under microclimatic conditions; the coefficient of determination (R2) between observed and simulated sap flow velocity in calibration sets was 0.91 (n = 2 532). On a typical sunny day, the highest rate of storage water use started at about 9:00 AM, decreased to zero at noon and turned to recharge throughout the afternoon until midnight. The daily storage water use varied between 0.04 and 0.58 mm·d-1 and was positively related to transpiration. Storage water provided 25.5% of transpiration water. When potential evapotranspiration (ETp) was < 4.9 mm·d-1, daily storage water use (DJz) was positively related to ETp. DJz linearly increased with ETp as ETp increased, but decreased correspondingly when ETp was >4.9 mmd-1. There was no significant relationship between DJz and soil water potential (p > 0.05), but the maximum DJz was positively related to soil water potential (R2= 0.79). Therefore, ETp is the primary driving factor of water storage use, and soil water potential is the limiting factor.

Key words: Larix principis-ruprechtii, sap flow, stem water transfer model, tree water storage