植物生态学报 ›› 2014, Vol. 38 ›› Issue (11): 1226-1240.DOI: 10.3724/SP.J.1258.2014.00118

所属专题: 稳定同位素生态学

• 研究论文 • 上一篇    下一篇

宁夏盐池不同坡位旱地紫苜蓿水分来源

朱林1,*(),祁亚淑2,许兴1   

  1. 1 宁夏大学西北土地退化与生态系统恢复国家重点实验室培育基地, 银川 750021
    2 宁夏大学农学院, 银川 750021
  • 收稿日期:2014-04-18 接受日期:2014-08-25 出版日期:2014-04-18 发布日期:2014-11-17
  • 通讯作者: 朱林
  • 基金资助:
    国家重点基础研究发展计划(2012-CB723206);国家自然科学基金(31160478)

Water sources of Medicago sativa grown in different slope positions in Yanchi County of Ningxia

ZHU Lin1,*(),QI Ya-Shu2,XU Xing1   

  1. 1 State Key Laboratory Breeding Base of Land Degradation and Ecological Restoration of Northwestern China, Ningxia University, Yinchuan 750021, China
    2 Agricultural College, Ningxia University, Yinchuan 750021, China
  • Received:2014-04-18 Accepted:2014-08-25 Online:2014-04-18 Published:2014-11-17
  • Contact: ZHU Lin

摘要:

紫苜蓿(Medicago sativa)是一种经济和生态价值较高的优良牧草, 但其耗水量大, 在西北半干旱地区仅靠天然降水难以满足紫苜蓿的正常生长发育。宁夏盐池北部地处毛乌素沙地南缘, 地下水埋深较浅, 地下水有可能成为紫苜蓿的潜在水源, 弥补天然降水的不足。本试验在地势平坦的缓坡丘陵梁地和丘间低地, 选择8年生旱地紫苜蓿试验地作为研究对象, 采用稳定同位素技术, 研究了不同海拔的4个坡位(海拔自低到高分别为: 坡1、坡2、坡3和坡4)紫苜蓿的水分来源及其生长生理表现。结果表明: 坡位对0-300 cm土壤剖面含水量有显著影响, 海拔最低的坡1土壤含水量最高。土壤水和植物茎秆水δ 18O-δD坐标点大部分位于中国西北地区地方大气降水线(LMWL)的右侧, 说明植物利用的水源氢氧同位素组成受到蒸发的影响而发生了富集作用。0-450 cm土壤剖面水δ 18O值随着海拔高度的增加而增大。同一坡位土壤水δ 18O值随着土壤深度的增加逐渐下降。深层土壤水δ 18O值与地下水δ 18O相近, 说明地下水通过土壤毛细管上升而补充其上层土壤水分。0-40 cm土壤水δ 18O值随季节波动较大, 270 cm以下土壤水δ 18O值较为稳定。4、7、8月份坡1紫苜蓿茎秆水δ 18O值显著低于其他3个坡位(p < 0.001)。在4、6、7三个月, 坡位1紫苜蓿对深层土壤水(270 cm以下)的利用率最高。而在8月份, 坡1、坡3、坡4紫苜蓿主要利用150-270 cm、270-450 cm土层土壤水以及地下水, 坡2对表层(0-20 cm)土壤水利用率最高。坡1紫苜蓿的产量、整株Δ 13C值及气孔导度显著高于其他3个坡位。本研究表明: 在平均年降水量只有280 mm的西北半干旱地区种植旱地紫苜蓿要尽量选择地势较低的滩地, 使其能够利用到埋深较浅地下水, 以满足植物生长发育的需要并取得较好的生态和经济效益。

关键词: 旱地紫苜蓿, 地下水利用, 植物水分来源, 稳定氢氧同位素

Abstract: Aims Alfalfa (Medicago sativa) is considered as an elite forage with high economic and ecological values. In semi-arid areas of Northwest China, the low rainfall is far from satisfying water demand of alfalfa. The northern part of Yanchi County is adjacent to Mu Us desert and has a shallow groundwater table. In this area, groundwater could be the potential water sources for growing alfalfa. Our objective was to investigate the growth performance and potential water sources of alfalfa grown in four slope positions with different altitudes in the bottomland of northern Yanchi County. Method Stable 18O and D isotope compositions (δ 18O and δD) of different water sources and xylem water were analyzed in April, June, July and August 2013. IsoSource was used to calculate the probable contribution of different water sources to the total plant water uptake. Stomatal conductance, carbon isotope discrimination (Δ 13C) of whole plant, soil volumetric water content in the 0-300 cm soil profile were also determined. Important findings Slope position had a significant effect on water content in the 0-300 cm soil profile. Highest soil water content was found in the slope position of lowest altitude. The δ 18O-δD coordinates of soil water and plant stem xylem water were distributed on the right of Northwest China local meteoric water line (LMWL), indicating that oxygen and hydrogen isotopic compositions in the water sources of alfalfa were subjected to enrichment due to evaporation. The δ 18O values of soil water in the 0-450 cm profile increased with altitude. Soil water δ 18O values decreased with the depth of soil profile for a given slope position. Soil water δ 18O values in deep profile were similar to those in groundwater, implying that groundwater would move to the upper soil layer via soil capillary. Seasonal fluctuation was observed in soil water δ 18O in the 0-40 cm profile, while soil water δ 18O in profile below 270 cm was stable seasonally. Plant stem xylem water δ 18O value was significantly lower (p < 0.001) in the slope position 1 than in other three slope positions in April, July and August. Highest water utilization rate from deep soil profile (below 270 cm) was recorded for alfalfa grown in the slope position 1 in April, June and July. In August, alfalfa grown in the slope positions 1, 3 and 4 mainly used soil water in the 150-270 cm and 270-450 cm profiles and groundwater; highest dependence on soil water in the shallow profile (0-20 cm) was found in alfalfa grown in the slope position 2. Higher yield, whole plant Δ 13C value and stomatal conductance were observed in alfalfa grown in the slope position 1 than in other three slope positions. These results suggest that bottomland with lower altitude and shallow groundwater table should be adopted when planting alfalfa without irrigation in the semi-arid areas of Northwest China where average annual rainfall is around 280 mm. Thus, groundwater could contribute to better growth performance of alfalfa, leading to higher ecological and economic returns.

Key words: dry-land alfalfa, groundwater utilization, plant water source, stable oxygen and hydrogen isotopes