摘要
为深入了解青藏高原东北部高寒森林小流域的氮循环过程,2022年4~9月,以青藏高原河湟谷地大通和湟源两处高寒森林站点的穿透水、土壤水和地表径流为研究对象,监测其可溶性无机氮(DIN)的浓度和通量,并利用稳定同位素技术分析硝酸盐(NO_(3)^(-))的氮氧(N、O)同位素沿水文路径(穿透水-土壤水-地表径流)的分布特征.结果表明,大通和湟源高寒森林的平均氮沉降(3.60kg/(hm^(2)·a))高于青藏高原地区的平均氮沉降(2.94kg/(hm^(2)·a)),并且湟源高寒森林氮沉降(4.17kg/(hm^(2)·a))高于大通高寒森林氮沉降(3.02kg/(hm^(2)·a)).两处高寒森林小流域土壤水中NO_(3)^(-)的平均浓度为5.78mg/L,其δ^(18)O-NO_(3)^(-)平均值((-1.54±9.77)‰)低于穿透水中δ^(18)O-NO_(3)^(-)的平均值((74.2±0.01)‰),表明高寒森林土壤中发生了硝化作用.利用端元混合模型计算发现土壤的硝化作用贡献了土壤水中90%以上的NO_(3)^(-),其余约10%则来源于大气沉降.两处高寒森林地表径流中NO_(3)^(-)的平均浓度为5.73mg/L,其δ^(18)O-NO_(3)^(-)和δ^(15)N-NO_(3)^(-)沿1:2的增长趋势富集,表明地表径流中存在反硝化过程.青藏高原高寒森林中的δ^(15)N-NO_(3)^(-)和δ^(18)O-NO_(3)^(-)沿穿透水-土壤水-地表径流均呈现先减小后增大的趋势.
To deeply understand the nitrogen cycling process in alpine forest small watersheds in the northeast of the Tibetan Plateau,the throughfall,soil water and surface runoff at two alpine forest sites in Datong and Huangyuan in the Hehuang Valley in the Tibetan Plateau were studied from April to September 2022.The concentration and flux of dissolved inorganic nitrogen(DIN)were monitored,and the distribution characteristics of nitrogen and oxygen(N and O)isotopes of nitrate(NO_(3)^(-))along the hydrological path(from throughfall to soil water and then to surface runoff)was analyzed via stable isotope technology.The results showed that the average nitrogen deposition in Datong and Huangyuan(3.60kg/(hm^(2)·a))was higher than that in the Tibetan Plateau(2.94kg/(hm^(2)·a)),and the nitrogen deposition in Huangyuan(4.17kg/(hm^(2)·a))was higher than that in Datong(3.02kg/(hm^(2)·a)).The average concentration of NO_(3)^(-)in soil water at the two alpine forest small watersheds was 5.78mg/L.The averageδ^(18)O-NO_(3)^(-)((-1.54±9.77)‰)in soil water was lower than that in throughfall((74.2±0.01)‰),indicating that nitrification occurred in alpine forest soil.Over 90%of the NO_(3)^(-)in soil water was from soil nitrification using the end member model analysis,and the remaining approximately 10%might be came from atmospheric deposition.The average concentration of NO_(3)^(-)in surface runoff at the two alpine forest small watersheds was 5.73mg/L.Theδ^(18)O-NO_(3)^(-)andδ^(15)N-NO_(3)^(-)in surface runoff were enriched along the growth trend of 1:2,indicating that a denitrification process occurred in surface runoff.Theδ^(15)N-NO_(3)^(-)andδ^(18)O-NO_(3)^(-)in the Tibetan Plateau alpine forests decreased from throughfall to soil water,and then increased from soil water to surface runoff.
作者
韩怡蒙
周剑兴
夏凡
李秉珍
谢丹妮
HAN Yi-meng;ZHOU Jian-xing;XIA Fan;LI Bing-zhen;XIE Dan-ni(School of Land Engineering,Chang’an University,Xi’an 710054,China)
出处
《中国环境科学》
北大核心
2025年第2期935-942,共8页
China Environmental Science
基金
国家自然科学基金资助项目(42303061)。
关键词
青藏高原
氮沉降
硝酸盐
氮氧同位素
高寒森林
Tibetan Plateau
nitrogen deposition
nitrate
nitrogen and oxygen isotopes
alpine forest
作者简介
责任作者:谢丹妮,讲师,dannixie@chd.edu.cn;韩怡蒙(2002-),女,河南洛阳人,长安大学硕士研究生,主要研究氮的生物地球化学循环.发表论文1篇.2023135018@chd.edu.cn.
