Chin J Plant Ecol ›› 2021, Vol. 45 ›› Issue (4): 334-344.DOI: 10.17521/cjpe.2020.0277

• Research Articles • Previous Articles     Next Articles

Effects of nitrogen and phosphorus addition at early-spring and middle-summer on ecosystem carbon exchanges of a degraded community in Nei Mongol typical steppe

LÜ Ya-Xiang1,2, QI Zhi-Yan1,2, LIU Wei1, SUN Jia-Mei1,*(), PAN Qing-Min1,2   

  1. 1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    2University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2020-08-11 Accepted:2020-11-12 Online:2021-04-20 Published:2021-03-27
  • Contact: SUN Jia-Mei
  • Supported by:
    National Natural Science Foundation of China(31870517)


Aims Overgrazing induced reduction in supply of soil nutrients is a major mechanism leading to extensive grassland degradation in China. The capacity of carbon (C) sequestration was demoted in the degraded grassland ecosystems. However, it remains unclear whether the capacity of carbon sequestration in a degraded grassland can be restored by the supplement of nutrients to the soil. Net ecosystem CO2 exchange (NEE), ecosystem respiration (ER) and gross ecosystem productivity (GEP) are important parameters describing the processes of ecosystem carbon cycle. Nitrogen (N) and phosphorus (P) are two limiting nutrients in typical steppe in China. To date, how these two nutrients alone or in combination affect the three parameters of carbon cycle (i.e., NEE, ER and GEP) in a degraded steppe community, especially their interactive effect, is poorly understood.

Methods To address these scientific questions, we conducted a field experiment in a degraded typical steppe community. Four treatments of nutrient addition were implemented: no nutrient addition (CK, control), adding N alone (10.5 g·m-2, NH4NO3), adding P alone (7 g·m-2, KH2PO4), and adding two nutrients in combination. Two stages were selected for fertilization: early-spring (April 21) and middle-summer (July 15).

Important findings Neither N nor P alone had significant effect on NEE, ER and GEP when nutrients applied at early-spring (April 21) or middle-summer (July 15), while their combination significantly increased the values ofNEE and GEP. 2) N and P exhibited strong synergistic effect on NEE, GEPand ER when applied in combination at early-spring (April 21), while a consistent additive effect between the two nutrients on the three carbon exchange parameters was observed when applied at middle-summer (July 15). Our findings have implications for the restoration of degraded grasslands. To restore the capacity of carbon sequestration of the degraded typical steppe ecosystem, supplying N and P in combination is better than a single nutrient alone, and appling these nutrients at spring is better than at summer.

Key words: grassland ecosystem, fertilization in grassland, grassland restoration, carbon cycle, interaction between nitrogen and phosphorus