Acta Geographica Sinica ›› 2004, Vol. 59 ›› Issue (1): 33-39.doi: 10.11821/xb200401004

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Water, Heat and CO2 Transfer over a Salinized Desert in the Arid Area

LI Yan1, WANG Qinxue2, MA Jian1, WATANABE Masataka2, ZHANG Xiaolei1   

  1. 1. Fukang Station of Desert Ecology, Xinjiang Institute of Ecology and Geography, CAS, Urumqi 830011, China;
    2. National Institute for Environmental Studies, Tsukuba 305-8506, Japan
  • Received:2003-09-25 Revised:2003-11-22 Online:2004-01-25 Published:2010-09-09
  • Supported by:

    Integrated Environmental Monitoring Subproject, the Asia-Pacific Environmental Innovation Strategy Project; Knowledge Innovation Project of CAS, No.KZCX3-SW-326

Abstract:

An eddy-covariance system and a micrometeorological station were installed at south periphery of Gurbantonggut Desert in April of 2002. Evaluation of the data showed that the measurements of sensible heat (H), latent heat (LE) and CO2 fluxes were reliable. However, a special phenomenon was revealed from detailed analysis on the diurnal and seasonal changes of the fluxes: when LE fluxes signified a strong water shortage and hence severe water stress should have been applied on the plants, CO2 fluxes indicated that the photosynthesis of the plant community was not affected. This was obviously against generally-accepted theory on plant-water relations. No concrete evidence available so far can explain this phenomenon, but we may speculate that local shrub plant might not benefit from the rainfall. Being a salinized desert, its upper soil layer contains high salt content. Thus shrub roots could not develop and survive at upper layer of the soil. On the contrary, roots might develop mainly at deep soil layers near the groundwater table. Therefore, whether rainfall wetted the upper soil layer or not, plant water condition was not affected, but the evapotranspiration (LE) was. The measured change of LE fluxes mainly came from evaporation of soil surface and CO2 fluxes were mainly determined by plant photosynthesis. Since the former is mainly influenced by soil water condition near soil surface and the latter determined by soil water condition near the groundwater table, it is just reasonable that the two aspects are not correlated. Thus, the phenomena reported here occurred under the combined local climatic, botanical and soil conditions and it is not really against the principle of plant-water relations in general.

Key words: desert, sensible heat, latent heat, net photosynthesis, groundwater table, Junggar