You are here

Harvard Forest >

Harvard Forest Symposium Abstract 2019

  • Title: Deciduous larch at the southern edge of Siberian boreal zone response to climate—Part Ⅱ: patterns and partitioning of transpiration and evapotranspiration
  • Primary Author: JiaLin Liu (Harvard University)
  • Additional Authors: J. William Munger (Harvard University)
  • Abstract:

    Precipitation as the total incoming water for ecosystems is a key factor affecting the land-atmosphere hydrological processes. Phenology as plant functional traits on long-term evolution to the local climate will respond also to the alteration of ecosystem water availability. However, it is still unclear how precipitation forcing and phenology respondence will regulate patterns and partitioning of water fluxes in the forest ecosystem, particularly the Siberian larch boreal forests. Two-years field observations on transpiration and evapotranspiration (ET) of this unique ecosystem is conducted near the southern edge of Siberia. Over half magnitude of ecosystem transpiration fluxes are contributed by dominant larches, and the rest is almost equally shared by intermediate and suppressed trees. ET is primarily occupied by the transpiration, where transpiration/ET is 84% in the regular (precipitation) year and 66% in the wetter (precipitation anomaly) year. In the two years, occurrences of precipitation reduce transpiration demands of trees but promoting the evaporation process. This phenomenon will be even more evident in the wetter year. Boreal larches thus extend their growing season length as a strategy to maintain ecosystem water sustainability under the over-wetting conditions. Water exchanges during leaf full-expansion phenophase determine their annual patterns and partitioning. While the frozen surface soil layer and vapor pressure deficit gradient from soil to air influence time-series patterns and proportion in ET of evaporation, particularly during leaf-dormant and leaf-onset phenophase. Extrapolations of ET over time and space can be predicted roughly by the satellite solar-induced chlorophyll fluorescence (SIF), since SIF shows its close correlations with both tower and satellite-derived ET. This study highlights the vastly-distributed but rarely-studied boreal laches may play much more significant roles in the water cycling of boreal zones and imparts knowledge about how boreal-arctic ecosystems will respond under the rapidly changing climate.

  • Research Category: Forest-Atmosphere Exchange