生态恢复背景下黄土高原东部地区典型植物用水策略

Typical plant water use strategies in the eastern part of the Loess Plateau under the background of ecological restoration

水分是干旱半干旱地区限制植物生长的关键因子,研究不同类型植物在不同水分条件下的用水策略已成为黄土高原地区生态保护和植被恢复的关键。通过对黄土高原东部典型生态恢复植物、粮食作物的植物水分及其潜在利用水源的稳定同位素的采集及分析测试,借助贝叶斯混合模型,本研究定量分析阶地平原(RVP)、土石山地(EMR)、丘陵沟壑区塬面(LH)及丘陵沟壑区沟谷(LG)四种地貌类型下的典型植物水分利用策略。结果表明:①区域土壤含水量(SWC)及土壤水稳定同位素呈现出显著时空异质性,土石山地土壤水氢氧同位素值波动最大,塬面SWC及土壤水氢氧稳定同位素值较稳定。②刺槐(Robinia pseudoacacia)和圆柏(Juniperus chinensis)的木质部水稳定同位素值的季节差异显著,两个树种均在4月份波动大、12月份波动较小;苹果树(Malus pumila)和梨树(Pyrus spp.)的木质部水稳定同位素组成的季节差异较小;野艾蒿(Artemisia lavandulifolia)的水稳定同位素值4月份和12月份在塬面较为富集,6月份和9月份在沟谷较为富集;冬小麦(Triticum aestivum)较之夏玉米(Zea mays)具有更大的植物水同位素值波动范围。③春夏两季,EMR地区的刺槐和圆柏主要利用0~20 cm土层土壤水,而LH地区和LG地区的刺槐和圆柏主要利用降水;秋冬季节,四种地貌类型下的刺槐和圆柏对深层土壤水的利用比重均有所增加。④表层土壤水是野艾蒿的主要植物水分来源,浅层土壤水为冬小麦越冬期和返青期以及夏玉米出苗期与成熟期的主要利用水源。本研究结果对黄土高原东部地区水资源的高效利用及植被恢复具有理论指导意义。

Water is an important limiting factor for plant growth in arid and semi-arid areas,and studying the water-use strategies of different types of plants under different water conditions has become a key to ecological protection and vegetation restoration in the Chinese Loess Plateau region.Through the systematic collection and analysis of stable isotopes of typical ecological restoration plants,food crops and water sources with potential water sources of regional plants in the eastern part of the Loess Plateau,this study used the Bayesian mixing model MixSIAR to quantitatively study the water-use strategies of typical plants under four geomorphic types river valley plain region(RVP),rocky mountain region(EMR),loess hilly region(LH)and loess gully region(LG).The results show that:(1)Significant spatial and temporal heterogeneity was observed in regional soil water content and soil water stable isotopes,with larger fluctuations in soil water isotope values appearing in the EMR region,the relatively stable soil water content and the smallest vertical difference of stable isotopic value of hydrogen and oxygen in soil water observed in the LH landscape.(2)The xylem water stable isotopes of Robinia pseudoacacia and Juniperus chinensis displayed obvious seasonal fluctuations,both tree species fluctuated greatly in April and less in December,whereas Malus pumila and Pyrus spp.had weak seasonal variability.The water isotopes of Artemisia lavandulifolia was enriched in the LH in April and December,and enriched in the gully in June and September.For crops,the range of the water isotopes for T.aestivum was larger than that of Z.mays.(3)In spring and summer,R.Pseudoacacia and J.chinensis mainly use 0-20 cm soil layer in the ERM region,and mainly use precipitation in the LH and LG region,whereas deep layers soil water becomes the main source in the four landform types during the winter.(4)A.Lavandulifolia mainly uses surface soil water,and the proportion of deep soil water utilization increases after September,representing strong ecological plasticity in its water-use strategy.Surface soil water was the main water source for T.aestivum during the overwintering and reviving periods,and Z.mays utilized the largest proportion of surface soil water during the seeding and maturation stages.In summary,the results of this study have important implications for sustainable vegetation protection and the optimal allocation of water resources in the study area.