摘要
水分条件是限制干旱半干旱地区植物生长重要的生态因子,为了揭示青海湖流域典型生态系统下芨芨草植物的水分利用来源及其如何响应水分条件的变化,选择了自然和干旱控制条件下芨芨草植物,通过测定芨芨草植物茎水和各潜在水源(土壤水、地下水及降水)中δD、δ^(18)O组成,并利用直接比较分析法和多源混合模型计算芨芨草植物对土壤水的利用比例。研究结果表明:表层土壤水分和土壤水中δD、δ^(18)O值表征出较大波动范围,其直接受降水和蒸发作用影响,土壤蒸发线的斜率和截距明显小于大气水线斜率和截距,表明土壤水中同位素组成经历了强烈的蒸发分馏过程,而芨芨草茎水中δD、δ^(18)O值都集中分布土壤水蒸发线附近,说明芨芨草根系主要利用不同深度的土壤水。自然条件下芨芨草在生长季初期(6月)利用表层土壤水(0—10cm,45.1%),8—9月份大降水事件影响土壤含水量和同位素组成,降水入渗深度较深且芨芨草根系对土壤水分吸收的比例相差不大,表明根系在土壤含水量较高时均能吸水不同深度土壤水。在干旱控制条件下芨芨草在7月初主要利用表层土壤水(0-30cm),随着表层土壤水分的减少,根系吸收深度转向较深土壤层,而灌溉后表层土壤水分明显增加,其吸收深度又转向表层,表明芨芨草根系吸收深度能敏感地响应土壤水分的变化。另外还发现芨芨草在生长季内并未直接利用地下水。
Water availability is a key ecological factor for plant growth in arid and semi-arid regions. We identified the characteristics of water-uptake patterns by Achnatherum splendens and how it responds to changes in water conditions in typical steppe ecosystem （Lake Qinghai watershed）. We analyzed stable isotopes of plant stem water and potential water sources including soil water, groundwater, and precipitation via direct comparison with differences among potential water sources and a multi-source mixing model calculating the plant-use proportions from diverse soil depths under natural and drought treatment areas. The results showed that there were large fluctuations in the soil moisture and the isotopic contents （δD） of soil water in the surface soil layers, directly influenced by precipitation and evaporation. The slope and intercept of the evaporative soil water line were evidently smaller than those of the meteoric water line, indicating that the isotopic contents from soil water experienced stronger evaporation fractionation processes. The isotopic contents （δD and δ80） of the stem were scattered along the soil evaporative water line indicating that the possible water sources were extracted from diverse soil water depths. A. splendens absorbed mainly surface soil water （the proportion from 0-10cm was 45. 1% in June） at the early growth stage. Large precipitation events significantly affected the soil water content and isotopic contents and infiltrated into deep soil layers. Differences in plant water use proportions were minimal during August and September, which revealed that the roots of A. splendens extracted water from various depths when soil water availability was high. Under the drought treatment conditions, A. splendens used mostly surface soil water （0-30 cm） in early July. The absorption water depth shifted to deep soil layers when the surface soil water became drier. However, the absorption depth again shifted from deep to surface soil layers when surface soil moisture sharply increased after irrigation. Groundwater was not a main water source for A. splendens during the entire growing season.
出处
《生态学报》
CAS
CSCD
北大核心
2015年第24期8174-8183,共10页
Acta Ecologica Sinica
基金
国家自然科学基金重点项目(41130640)
长江学者和创新团队计划(IRT1108)
中央高校基本科研业务费专项资助
关键词
氢氧稳定同位素
降水
土壤水
芨芨草
水分利用来源
青海湖流域
stable isotopes
precipitation
soil water
Achnatherum splendens
water-use sources
Lake Qinghai watershed
