Chin J Plant Ecol ›› 2021, Vol. 45 ›› Issue (1): 13-22.DOI: 10.17521/cjpe.2020.0185

• Research Articles • Previous Articles     Next Articles

Effects of nitrogen addition and planting density on the growth and biological nitrogen fixation of Lespedeza davurica

WANG Yin-Liu1,2, GENG Qian-Qian1,2, HUANG Jian-Hui1,2,*(), WANG Chang-Hui1, LI Lei1,2, HASI Muqier1,2, NIU Guo-Xiang1,2   

  1. 1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    2College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2020-06-11 Accepted:2020-11-30 Online:2021-01-20 Published:2021-02-07
  • Contact: HUANG Jian-Hui
  • Supported by:
    National Natural Science Foundation of China(31670483)


Aims Nitrogen (N) supply and planting density are two important factors influencing plant growth. Legumes are important to ecosystem N input because of their capacity of biological N2 fixation (BNF). Increasing atmospheric N deposition may promote the growth of leguminous plants, but it may also inhibit strongly their BNF capacity. Planting density can also influence the growth and BNF capacity of legumes due to intraspecific competition. However, few studies up to date have focused on the effects of N fertilization and planting density on the growth and BNF capacity of legumes. In this study, we aimed to explore the potentially interactive effects of N fertilization and planting density on the growth and BNF capacity of Lespedeza davurica, a leguminous plant species which is widely distributed throughout the northern China grasslands.
Methods A pot experiment was conducted in a greenhouse. The experiment contained four levels of N addition (0, 5, 10, 20 g·m-2·a-1) by NH4NO3fertilizer and three levels of planting densities (1, 3, 6 Ind.·pot-1, i.e. 32, 96, 192 Ind.·m-2).
Important findings 1) Our results showed that both N addition and planting density could impact the biomass production ofL. davurica. N addition increased plant leaf carbon (C) and N contents and leaf-level net photosynthetic rate. Besides, N addition also stimulated the plant growth at both pot and individual levels, and the yield reached maximum at N addition of 10 g·m-2·a-1. Increasing planting density decreased leaf C and N contents, leaf-level net photosynthetic rate, and individual growth, but increased total biomass in each pot. 2) Nitrogen addition reduced the capacity of BNF of L. davurica, while increasing planting density could weaken this suppression effect to some extent. The combination of N addition of 10 g·m-2·a-1 and planting density of 3 Ind.·pot-1 or N addition of 10 g·m-2·a-1 and planting density of 6 Ind.·pot-1 could maximize the effects of N application on individual yield and the effects of increasing planting density on the alleviation of BNF suppression. Nitrogen addition suppressed the BNF of L. davurica through reducing plant investment to nodulation and nodule biomass production. The intraspecific competition and resource limitation caused by increasing planting density led to improvement in the investment to nodulation and nodule growth. 3) Structural equation model analyses showed that N addition and planting density combined explained variations in the plant biomass and nodule production either directly or indirectly by 64% and 42%, respectively. The results indicate that it is important to optimize the amount of fertilizer application and appropriate planting density when considering plantation and management of artificial and degraded grasslands.

Key words: N addition, planting density, biomass, nodule biomass, investment to nodulation, biological nitrogen fixation