Chin J Plant Ecol ›› 2018, Vol. 42 ›› Issue (2): 195-201.DOI: 10.17521/cjpe.2017.0082

• Research Articles • Previous Articles     Next Articles

Estimating whole-tree water use of Picea crassifolia based on heat ratio method

YANG Jun-Jun1,*(),FENG Jian-Min1,HE Zhi-Bin2   

  1. 1College of Resource & Environment and Historical Culture, Xianyang Normal University, Xianyang, Shaanxi 712000, China;

    2Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
  • Online:2018-02-20 Published:2018-04-16
  • Contact: Jun-Jun YANG
  • Supported by:
    Supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(2014BAL01B03);the National Natural Science Foundation of China(41522102);the Shaanxi Province Key Science and Technology Innovation Team Project(2016KCT-23)

Abstract:

Aims Accurate estimation of forest transpiration in the upper reach of the watershed is vital to the management of water resources in arid region. The objective of this study was to provide a systematic method for calculating the forest evapotranspiration at different scales.

Methods In this study we measured the whole-tree transpiration using the heat ratio method technology and estimated the stand- and catchment-transpiration employing the upscaling methods.

Important findings The main results and conclusions were as follows: First, the diameter at breast height (DBH) exhibited significant correlations with sapwood area, and the correlation was characterized by the exponential function (R2=0.94,p<0.001).Second, in the weighted calculation of sap-flux measurements based on two-point thermocouples and sapwood area of Picea crassifolia,the correction coefficient between the true value and the observation value was 1.09. Third, when calculating sap-fluxes based on the average-sap-flux and total sapwood area of stand-transpiration, ignoring sap-flux velocity heterogeneities of trees led to transpiration rates being overestimated or underestimated by nearly one third; Fourth, the stand-transpiration estimation method based on the relationship between DBH and sap-flux can give a more reasonable prediction ofPicea crassifolia transpiration. The results indicated that the probe-based sap-flux measuring technology would perform well for the transpiration scaling-up calculation at the catchment with only one single tree species, and the calculation methodology can be applied to other watersheds.

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Key words: transpiration, upscaling, heat ratio method, Picea crassifolia