Sap flow velocity of deciduous broad-leaved trees in urban area and its dependence on environmental factors

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Other Title
  • 都市内緑地における落葉広葉樹の樹液流速とその環境要素への依存性

Abstract

To examine the dependence of sap flow velocity (SFV) on the environmental variables in an urban wooded area, diurnal and seasonal variations in SFV of deciduous broad-leaved trees (Quercus acutissima Carruthers) and meteorological and soil parameters were measured from April to November 2009 in Minami-osawa campus, Tokyo metropolitan university. The SFV values were determined by a Granier method. On a sunny day, SFV increased rapidly in the morning and decreased rapidly in the evening, but it was relatively stable at midday. On cloudy and rainy days, the SFV values followed the changes in global solar radiation and vapor pressure deficit. The result of lag correlation analysis for all of the study period indicated that the diurnal variation in SFV was highly related to solar radiation with a time lag of 1-2 h and moderately related to vapor pressure deficit and air temperature without a time lag. Seasonally, the daily values of SFV fluctuated sharply depending on the weather conditions. SFV on sunny days increased during April and May, and reached its maximum value in June, and decreased rapidly in November. The seasonal variation in SFV was strongly affected by daily solar radiation and daily vapor pressure deficit, and the relationship between SFV and solar radiation were well expressed by a rectangular hyperbolic function. But data of April and May indicated a significantly low value relative to other months. These results suggest that seasonal change in the SFV may depend on not only meteorological parameters but also the phenological stage of the tree. The SFV residuals of the solar radiation model did not show strong correlation with vapor pressure deficit, air temperature, wind speed, or soil water content. The daily values of SFV depended on the meteorological parameters especially on cloudy days and rainy days. In addition, it was shown that SFV without data of vegetative stage and exfoliation stage clearly depends on meteorological parameters.

Journal

  • Climate in Biosphere

    Climate in Biosphere 11 (0), 31-40, 2011

    The Society of Agricultural Meteorology of Japan

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