Plant and Soil

, Volume 416, Issue 1–2, pp 515–525

Responses of root exudation and nutrient cycling to grazing intensities and recovery practices in an alpine meadow: An implication for pasture management

Regular Article

Abstract

Background and aims

The rhizosphere priming effect is caused by root carbon (C) exudation into the rhizosphere; the role of this effect in nutrient cycling and ecosystem recovery of natural grasslands as affected by different grazing intensities is still unknown. The objective of the present study was to investigate the relationships among root C exudation, rhizospheric microbial activity, and their influences on plant nutrient uptake during grazing and recovery periods.

Methods

Field experiments were conducted in the Hongyuan Alpine Meadow to measure root exudation rate and nutrient cycling processes of the dominant species Elymus nutans. Three grazing intensities (an ungrazed control, moderate grazing and heavy grazing) were introduced for two months, following which all treatments received a recovery practice (no grazing for 21 days).

Results

Heavy grazing significantly decreased root exudation rate, soil nitrogen (N) mineralization rate, β-1,4-glucosidase (BG) activity, and foliar C concentration, while moderate grazing had no influence on these parameters compared to the control. After the 21 days of recovery, all these parameters, except N mineralization rate and foliar C concentrations in the heavy grazing treatment, returned to similar levels as in the control, whereas root exudation rate and BG activity rose to even higher levels. Meanwhile, moderate grazing significantly promoted root exudation rate, soil inorganic N concentration, net soil N mineralization rate, and β-N-acetylglucosaminidase (NAG) activity during the recovery stage as compared to the control. Foliar quality was also improved by the recovery practice, indicating that the high availability of N and P is a consequence of the positive root–microbe feedback and will ultimately benefit grazers.

Conclusions

The flush of labile C released to the rhizosphere by grazed plants stimulated extracellular enzyme activities, enhanced soil N mineralization, and increased plant nutrient uptake. These results imply that reasonable (i.e. moderate) grazing followed by a recovery practice can effectively restore and strengthen grassland vegetation, and contribute to the sustainable use of alpine meadows such as Hongyuan.

Keywords

Grazing intensities Microbial activity Nitrogen mineralization Recovery Root exudation 

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Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  • Geng Sun
    • 1
  • Xia Zhu-Barker
    • 2
  • Dongming Chen
    • 1
  • Lin Liu
    • 3
  • Nannan Zhang
    • 1
  • Changguang Shi
    • 1
  • Liping He
    • 4
  • Yanbao Lei
    • 5
  1. 1.CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of BiologyChinese Academy of SciencesChengduChina
  2. 2.Department of Land, Air & Water ResourcesUniversity of CaliforniaDavisUSA
  3. 3.College of Animal Science and TechnologySichuan Agricultural UniversityChengduChina
  4. 4.Yunnan Academy of Forestry SciencesKunmingChina
  5. 5.CAS Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengduChina

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