植物生态学报 ›› 2018, Vol. 42 ›› Issue (1): 95-104.DOI: 10.17521/cjpe.2017.0100

• 研究论文 • 上一篇    下一篇

高寒草原土壤交换性盐基离子对氮添加的响应: 以紫花针茅草原为例

秦书琪1,2,房凯1,2,王冠钦1,2,彭云峰1,张典业1,2,李飞1,2,周国英3,杨元合1,2,*()   

  1. 1 中国科学院植物研究所植被与环境变化国家重点实验室, 北京 100093
    2 中国科学院大学, 北京 100049
    3 中国科学院西北高原生物研究所藏药研究重点实验室, 西宁 810008
  • 出版日期:2018-01-20 发布日期:2018-03-08
  • 通讯作者: 杨元合
  • 基金资助:
    国家自然科学基金(41371213)

Responses of exchangeable base cations to continuously increasing nitrogen addition in alpine steppe: A case study of Stipa purpurea steppe

QIN Shu-Qi1,2,FANG Kai1,2,WANG Guan-Qin1,2,PENG Yun-Feng1,ZHANG Dian-Ye1,2,LI Fei1,2,ZHOU Guo-Ying3,YANG Yuan-He1,2,*()   

  1. 1 State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China

    2 University of Chinese Academy of Sciences, Beijing 100049, China

    3 Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810008, China
  • Online:2018-01-20 Published:2018-03-08
  • Contact: Yuan-He YANG
  • Supported by:
    Supported by the National Natural Science Foundation of China(41371213)

摘要:

土壤交换性盐基离子(Ca 2+、Mg 2+、K +、Na +)在维持土壤养分与缓冲土壤酸化中起着重要作用, 了解其对氮添加的响应有助于准确评估氮沉降背景下生态系统结构与功能的动态变化。然而, 目前关于土壤交换性盐基离子对氮添加响应的相关研究主要集中在酸性土中。鉴于目前在碱性土中研究相对较少的现状, 该研究以青藏高原高寒草原为研究对象, 依托氮添加控制实验平台, 通过连续3年(2014-2016)的测定, 考察了8个不同施氮水平(0、1、2、4、8、16、24、32 g·m -2·a -1)下土壤交换性盐基离子含量变化及其可能原因。结果显示: 随着施氮量的增加, 土壤交换性盐基离子, 尤其是Mg 2+与Na +含量显著降低。并且, 盐基离子含量与植物地上生物量显著负相关(p < 0.05), 说明氮添加通过促进植物生长, 加速植物对盐基离子的吸收, 进而导致土壤中盐基离子含量降低。此外, 盐基离子含量也与土壤无机氮含量呈显著负相关(p < 0.05)关系, 说明施氮还通过提高土壤中无机氮含量进而导致更多NH4 +与土壤吸附的盐基离子交换, 同时加剧NO3 -淋溶, 带走等电荷阳离子。需要指出的是, 虽然连续施氮导致土壤pH值下降, 但该土壤目前仍处于碳酸盐缓冲阶段, 说明通常在酸性土中报道的“因缓冲土壤酸化引起的盐基离子损失机制”在碱性土中并不成立。这些结果意味着持续的氮输入会造成碱性土中盐基离子损失, 进而影响土壤缓冲能力与植被生产力, 未来草原生态系统管理中应重视这一问题。

关键词: 交换性盐基离子, 氮沉降, 碱性土, 植物吸收, 缓冲阶段

Abstract:

Aims Soil exchangeable base cations (BCs) play important roles in keeping soil nutrient and buffering soil acidification, which may be disturbed by anthropogenic nitrogen (N) input. Considering relatively limited evidence from alkaline soils, this study was designed to explore the effects of N addition on soil exchangeable BCs in a typical alpine steppe on the Qinghai-Xizang Plateau.

Methods From May 2013, eight levels of N addition (0, 1, 2, 4, 8, 16, 24, 32 g·m -2·a -1) in the form of NH4NO3 were added in the alpine steppe, where soil is alkaline. During the following three years (2014-2016), we collected soil samples in mid-August in each year. By measuring the concentrations of exchangeable BCs, we examined their changes along the N addition gradient. We also explored the relationships between BCs and other plant and soil properties.

Important findings Continuous N addition resulted in significant loss of exchangeable BCs, especially Mg 2+ in all three years and Na +in two years. The concentrations of BCs were found to be negatively related to above-ground biomass and the concentration of soil inorganic N (p < 0.05). These results indicated that increase in N availability stimulated plant growth, which in turn led to more uptake of BCs by plants. Moreover, enhanced NO3 - leaching resulted in the loss of BCs due to the charge balance in soil solution. In addition, increased NH4 + displaced BCs binding to soil surface and made them easy to be leached out of soils. Different from acid soils, soil acidification caused by N deposition in alkaline soils is mainly buffered by calcium carbonate, having less effect on BCs. Our results suggest that N addition results in the loss of exchangeable BCs in alkaline soils, leading to poor buffering capacity and decreased plant productivity over long time period, which needs to be considered during grassland management in the future.

Key words: exchangeable base cations, nitrogen deposition, alkaline soil, plant uptake, buffering phase