Chin J Plant Ecol ›› 2012, Vol. 36 ›› Issue (7): 618-628.DOI: 10.3724/SP.J.1258.2012.00618

Special Issue: 稳定同位素生态学

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Water sources of shrubs grown in the northern Ningxia Plain of China characterized by shallow groundwater table

ZHU Lin1,2,*(), XU Xing1, MAO Gui-Lian3   

  1. 1Key Laboratory for Restoration and Reconstruction of Degraded Ecosystem in North-western China, Ministry of Education, Ningxia University, Yinchuan 750021, China
    2State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Water and Soil Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China
    3Life Science College, Ningxia University,Yinchuan 750021, China
  • Published:2012-07-10
  • Contact: ZHU Lin


Aims Shallow groundwater table is the main cause of salinization in the northern Ningxia Plain of China. The uptake of groundwater by halophytes can lower the groundwater table and reduce the demand for irrigation. Our objective was to investigate the potential water sources (different soil profile and groundwater) of four shrubs, i.e., twenty-year-old Tamarix ramosissima and three-year-old T. ramosissima, Lycium barbarum and Atriplex canescens.

Method Stable18O and D isotope compositions (δ18O and δD) of different potential water sources and xylem water were analyzed before and after irrigation. The IsoSource mode was used to calculate the probable contribution of different water sources to the total plant water uptake. The photosynthetic gas exchange parameters, contents of salt and water and pH in 0-200 cm soil profile were also determined.

Important findings Soil water δ 18O and δD in different depths differed consistently. The soil water δ 18O and δD values decreased with depth. More negative soil water δ 18O and δD values were recorded after irrigation. There were significant effects of evaporation and irrigation on soil water δ 18O and δD values. δ 18O and δD values of twenty-year-old T. ramosissima were lower than that of the three-year-old shrubs. Before irrigation, the three-year-old T. ramosissima, L. barbarum and A. canescens mainly tapped water in the upper soil layer (70.1%, 52.3% and 48.9%); highest groundwater uptake rate (21.5%) was observed for twenty-year-old T. ramosissima. After irrigation, higher water uptake rates from 80-140 cm soil profile were recorded for three-year-old T. ramosissima (59.5%) and L. barbarum (58.8%). Highest groundwater uptake rate was found for twenty-year-old T. ramosissima (18.3%). Before irrigation, the net photosynthetic rate, stomatal conductance and transpiration rate of twenty-year-old T. ramosissima were higher than those of other shrubs. Highest net photosynthetic rate were observed for three-year-old A. canescens after irrigation. Irrigation had significant effects on net photosynthetic rate and stomatal conductance of three-year-old T. ramosissima and L. barbarum. The intrinsic water use efficiency of three-year-old A. canescens was higher than other shrubs. These results suggested that different shrubs have different water use strategies, which is presumably related to species and age of shrubs. Young T. ramosissima mainly extracted soil water from upper un-saturated profile based on its strong tolerance to drought, and it switched its water use to middle soil profile after irrigation. Mature T. ramosissima turned out to bephreatophytic with growth being heavily dependent on groundwater and deep soil water and unresponsive to irrigation.

Key words: groundwater utilization, Ningxia Plain, saline-alkali land, shrub, stable hydrogen and oxygen isotope