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农田灌溉排水对古尔班通古特沙漠南缘荒漠植物氮素利用的影响
王斌
学位类型硕士
导师马健
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业环境工程
关键词灌溉排水 荒漠植物 氮素来源 氮同位素 地下水
摘要氮素是荒漠生态系统仅次于水分的一个限制因子。人类活动,诸如氮肥的使用及氮氧化物的排放等,显著改变了全球N循环,几乎使所有生态系统氮素输入增加。农田生态系统,施入的氮肥,除被作物吸收利用外,有相当数量残留于土壤中。灌溉或强降雨易造成农田氮素的淋失,使地下水中硝态氮(NO3--N)升高。为探讨绿洲农田灌溉排水,被淋失的氮素是否影响荒漠植物氮素的利用。本研究以被绿洲农田中的原生荒漠,绿洲荒漠过渡带及远离农田的荒漠为研究区,选择3种不同生活型的荒漠植物梭梭(Haloxylon ammodendron)、多枝柽柳 (Tamarix ramosissima)、散枝猪毛菜(Salsola brachiata)、尖喙牻牛儿苗(Erodium oxyrrhynchum)、小花荆芥(Nepeta micrantha)和齿稃草(Schismus arabicus)为研究对象,研究了农田土壤及荒漠梭梭和多枝柽柳冠下土壤TN、15N自然丰度值(δ15N)的分布特征,农田、荒漠地下水中NO3--N的变化规律,以及3种不同生活型的荒漠植物叶片δ15N的分布特征。 结果表明:(1) 农田土壤TN在深层剖面(200~300cm)有积累,农田地下水NO3--N浓度明显高于荒漠,且在荒漠区由边缘向荒漠腹地逐渐递减。(2) 农田及梭梭和多枝柽柳冠下土壤整个剖面δ15N平均值大小依次为:荒漠>荒漠边缘>原生荒漠>农田,其变化与土壤TN变化相反。距农田越近,土壤垂直剖面δ15N变化越小,可能说明农田灌溉侧渗或地下水对土壤δ15N分布有影响。梭梭和多枝柽柳冠下表层土壤δ15N无显著差异,深层土壤δ15N存在显著差异。距农田越近,深层土壤δ15N越低,可能说明深层土壤δ15N受地下水中NO3--N的影响,并且从荒漠边缘到荒漠腹地,土壤δ15N受地下水NO3--N的影响程度逐渐降低。(3) 多枝柽柳δ15N值显著小于梭梭、散枝猪毛菜、齿稃草、尖喙牻牛儿苗和小花荆芥的δ15N值(p<0.05),多枝柽柳和梭梭δ15N与土壤TN含量和土壤含水量显著负相关(p<0.05)。可能说明多枝柽柳氮素利用直接受农田灌溉排水影响,梭梭氮素利用间接受农田灌溉排水影响,散枝猪毛菜、齿稃草、尖喙牻牛儿苗和小花荆芥氮素利用基本不受农田灌溉排水影响。 本研究表明,在绿洲荒漠过渡带,农田灌溉排水可能影响深根系荒漠植物氮素的利用。随着农田氮素投入的不断增加,灌溉排水导致荒漠地下水NO3--N浓度不断升高,地下水可能会成为荒漠植物重要的氮源,这将会改变绿洲荒漠过渡带物种组成,提高荒漠生态系统生产力。通过本研究使我们更好理解,绿洲农田灌溉排水对荒漠植物水分、养分利用的影响,并对绿洲荒漠过渡带可能出现的生态演变提供理论支持。
其他摘要Nitrogen is the second limiting factor in desert ecosystem after water. Attributed to Human activities, such as the utilization of nitrogen fertilizer and nitrogen oxide emissions, So significant changes have taken place in the global N cycle that almost all the ecosystem N input increased. Agricultural nitrogen fertilizer, except those absorbed by crops, had quite a number of residues in the soil. Attributed to the irrigation or heavy rains, much nitrogen was leached and made the concentration of NO3--N in groundwater was increased. To investigate whether the leached Nitrogen could affect nitrogen utilization of desert plants after irrigation and drainage in desert oasis ecotone, the experiments were carried out in these plots including the desert Surrounded by farmland, the oasis desert ecotone and the desert away farmland. Three kinds of desert plants with different life forms, Haloxylon ammodendron, Tamarix ramosissima, Salsola brachiata, Erodium oxyrrhynchum, Nepeta micrantha and Schismus arabicus were choosed, to study concentration variations of NO3--N of groundwater in desert oasis ecotone, vertical distributions of TN and δ15N of farmland soil and desert soil of H. ammodendron and T. ramosissima, and δ15N values of different desert plants. The experiment revealed that: (1) The farmland soil TN was accumulated in deep profiles (200~300cm), NO3--N concentrations of groundwater in farmland were significant higher than desert, and gradually decreased from the desert edge to the hinterland. (2) The soil δ15N value in desert was largest, ecotone second, followed by native desert and farmland was minimum, and they in whole profiles had a negative change with TN content. The closer the farmland, the smaller the varations of δ15N values in vertical profile, which may indicated farmland lateral seepage or groundwater had an impact on soil δ15N values. Besides, there were no significant differences of surface soil δ15N values of H. ammodendron and T. ramosissima in different plots, but the deeper soil δ15N values. The closer the farmland, the lower the deep soil δ15N values that implyed the deep soil δ15N values may be affected by NO3--N in groundwater, and agricultural irrigation had an indirect impact on deep soil δ15N values, it also suggested the impact gradually reduced from the edge to the hinterland. (3) The δ15N value of T. ramosissima was significant smaller than H. ammodendron, Salsola brachiata, Erodium oxyrrhynchum, Nepeta micrantha and Schismus arabicus (p<0.05), the δ15N values of T. ramosissima and H. ammodendron had a significant negative correlation with soil moisture and TN content (p<0.05), which may indicate T. ramosissima nitrogen utilization directly affected by agricultural irrigation and H. ammodendron indirectly affected, but Salsola brachiata, Erodium oxyrrhynchum, Nepeta micrantha, Schismus arabicus nitrogen utilization largely unaffected by agricultural irrigation. In conclusion,in the desert oasis ecotone, the agricultural irrigation likely had an impact on the nitrogen utilization of desert plants with deep roots. So with increasing of nitrogen input and rising of NO3--N concentrations in groundwater caused by agricultural irrigation, the groundwater may become an important nitrogen source, which could change the oasis desert ecotone species composition and improve primary productivity in desert ecosystem. These find may improve our understanding of the impact of agricultural irrigation on the nitrogen and water utilization of desert plants. Additionally, the study may provide some theoretical support for the possible ecological evolution in the desert oasis ecotone.
学科领域环境工程
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14670
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
王斌. 农田灌溉排水对古尔班通古特沙漠南缘荒漠植物氮素利用的影响[D]. 北京. 中国科学院大学,2015.
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