JOURNAL OF NATURAL RESOURCES ›› 2012, Vol. ›› Issue (10): 1696-1707.doi: 10.11849/zrzyxb.2012.10.008

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Clipping Alters the Response of Biomass Allocation Pattern under Nitrogen Addition in an Alpine Meadow on the Tibetan Plateau

ZONG Ning1,4, SHI Pei-li1, SONG Ming-hua2, LIN Lin3,4, MA Wei-ling1,4, JIANG Jing2,4, FU Gang1,4, HE Yong-tao1, ZHANG Xian-zhou1   

  1. 1. Lhasa National Ecological Research Station, Key Laboratory of Ecosystem Network Observation and Modelling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    2. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    3. Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, CAS, Lanzhou 730000, China;
    4. University of Chinese Academy of Sciences, Beijing100049, China
  • Received:2011-11-23 Revised:2012-04-26 Online:2012-10-20 Published:2012-10-20

Abstract: Growth of alpine plants is primarily limited by low available nitrogen in the soil. Both nitrogen addition and grazing affect soil nutrient availability and uptake of alpine plants, and consequently influence community productivity. To understand the effects of nitrogen addition and grazing on the ecosystem function, nitrogen addition experiment in combination with simulated grazing (clipping) has been conducted in an alpine ecosystem on the northern Tibetan Plateau since 2010. The levels of nitrogen addition in stimulated grazed (G+N) and non-grazed plots (NG+N) were controlled at 0 (N0), 10 (N10), 20 (N20) and 40 (N40) kg N穐m-2-1, respectively. Net nitrogen mineralization was measured by in-situ close-top incubation during the growing season in 2011. Nitrogen addition and clipping had different effects on the biomass allocation of alpine plants. Nitrogen addition mainly stimulated the above-ground productivity in non-grazed plots, but enhanced below-ground productivity in grazed plots. Although about 15%-20% of the above-ground biomass was removed by clipping, there is no difference of total biomass between grazed and non-grazed plots or even higher in grazed than non-grazed plots, owing to stimulating effects of nitrogen enrichment on the compensatory growth of alpine plants. Moreover, the different responses of biomass allocation to nitrogen addition and clipping were also reflected in the pattern closely related to soil nitrogen supply potential. Net nitrogen mineralization was negatively correlative with the above-ground biomass in non-grazed plots, but with below-ground biomass in grazed plots. It is indicated that alpine plants responded to soil nutrient and grazing by altering the allocation pattern of photosynthetic assimilates. The present study also suggested that in alpine meadow limited by available nutrient, nitrogen addition may stimulate compensatory growth of plants.

Key words: nitrogen addition, clipping, biomass allocation, soil nitrogen supply potential, alpine meadow

CLC Number: 

  • S812