围栏对高寒草原优势物种氮吸收策略的影响  

Effects of fencing on the nitrogen uptake strategy of dominant species in an alpine steppe

作　　者：喻鳟善 索娜卓嘎 洪江涛[1,2] 庞博 王小丹[1,2] YU Zunshan;Suonazhuoga;HONG Jiangtao;PANG Bo;WANG Xiaodan(Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,Chengdu 610014,Sichuan,China;Xainza Alpine Steppe and Wetland Ecosystem Observation Station,Xainza 853100,Tibet,China;University of Chinese Academy of Sciences,Beijing 100049,China;Tibet Ecological Environment Monitoring Center,Lhasa 850000,Tibet,China)

机构地区：[1]中国科学院、水利部成都山地灾害与坏境研究所,四川成都610041 [2]申扎高寒草原与湿地生态系统观测试验站,西藏申扎853100 [3]中国科学院大学,北京100049 [4]西藏自治区生态环境监测中心,西藏拉萨850000

出　　处：《草业科学》2023年第4期864-873,共10页Pratacultural Science

基　　金：第二次青藏高原综合科学考察研究(2019QZKK0404);国家自然科学基金(41701343)。

摘　　要：围栏封育是促进退化高寒草地生态恢复和重建的重要工程措施。目前对围栏封育条件下高寒草地氮(N)营养特征的研究主要集中于土壤或植被独立的系统,仍缺乏土壤-植被N素传递和利用效率方面的报道。本研究以藏北高寒草原典型物种紫花针茅(Stipa purpurea)和昆仑蒿(Artemisia nanschanica)为研究对象,采用^(15)N稳定同位素示踪技术(^(15)N-NH_(4)^(+)和^(15)N-NO_(3)^(-)),分析围栏封育和自由放牧草地典型物种对不同形态N吸收速率、偏好策略及及其土壤剖面差异。结果表明:1)与自由放牧相比,围栏封育显著提升了紫花针茅在不同土层中的平均N吸收效率,其中,NH_(4)^(+)和NO_(3)^(-)吸收速率分别提高了4.78和9.34μg·(g·h)^(−1)。围栏封育提升了昆仑蒿NO_(3)^(-)吸收速率,但对NH_(4)^(+)吸收速率影响较为微弱。2)两种草地管理方式下,紫花针茅和昆仑蒿均偏好吸收NO_(3)^(-),表现出与土壤背景主导N形态相契合的特点。3)高寒草原典型物种表层根系N吸收速率高于深层根系,与根系生物量的土壤剖面分布格局基本一致。本研究揭示了草地生态工程对高寒典型物种N营养适应策略的影响,为后续退化高寒草地保护与恢复提供了科学依据。Fencing is an important grassland management method promoting ecological restoration and reconstruction of degraded alpine steppe.Current studies on the nitrogen(N)nutrient characteristics of fenced alpine steppes have mainly focused on soil-and vegetation-independent systems.However,there are few reports on nitrogen transfer and utilization efficiency in plants and soils as a whole.In this study,we used Stipa purpurea and Artemisia nanschanica in a fenced alpine steppe used for grazing on the northern Tibetan Plateau to investigate plant N uptake rates and preferential strategies for different chemical forms of N at varying soil depths,using an^(15)N stable isotope tracer technique(^(15)N-NH_(4)^(+)and^(15)N-NO_(3)^(-)).The key findings were as follows:1)Fencing significantly increased the average N uptake efficiency in S.purpurea in different soil layers,with NH_(4)^(+)and NO_(3)^(-)uptake rates increasing by 4.78 and 9.34μg·(g·h)^(−1),respectively,compared to the unfenced grazing steppe.Fencing also increased the NO_(3)^(-)uptake rate in A.nanschanica but had a weak effect on NH_(4)^(+)uptake rate.2)Under the two types of grassland management practices,both species showed a preference for NO_(3)^(-)uptake,which was consistent with the dominant N form of the soil background.3)The N uptake rate of surface roots of typical species growing in alpine grasslands was higher than that of deep roots,which was generally consistent with the spatial distribution of root biomass along the soil profile.This study reveals the effects of grassland management measures on the N adaptation strategies of typical alpine species,providing a scientific basis for subsequent conservation and restoration of degraded alpine steppe.

关 键 词：青藏高原 N吸收偏好 稳定同位素 15N示踪 草地管理方式 营养适应策略 土壤剖面差异 

分 类 号：S812[农业科学—草业科学]