Chin J Plan Ecolo ›› 2015, Vol. 39 ›› Issue (10): 950-961.DOI: 10.17521/cjpe.2015.0092

• Orginal Article • Previous Articles     Next Articles

Effects of the level and regime of nitrogen addition on seedling growth of four major tree species in subtropical China

LIU Shuang-E1,2, LI Yi-Yong1,2, FANG Xiong1,2, HUANG Wen-Juan1, LONG Feng-Ling1,2, LIU Ju-Xiu1,*()   

  1. 1South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China
    2University of Chinese Academy of Sciences, Beijing 100049, China
  • Online:2015-10-01 Published:2015-10-24
  • Contact: Ju-Xiu LIU
  • About author:

    # Co-first authors

Abstract: <i>Aims</i>

Numerous studies have been carried out concerning the effects of atmospheric nitrogen (N) deposition on forest ecosystems. However, most of previous experiments were conducted by adding N fertilizer to the surface soil directly. Realistically simulated canopy N deposition and comparison of the effects of soil N addition and canopy N addition on ecosystems were rare. Our purpose is to better understand the effects of two N addition regimes at different N addition levels on seeding growth in major tree species of subtropical China.


A 2-year pot experiment was conducted, with seedlings of four species (Ormosia pinnata, Acacia mangium, Schima superba, Pinus massoniana) grown in pots subjected to treatments of three levels (ambient, medium, and high) and two regimes (in soil vs. on canopy) of N addition, specifically including S-CK (ambient N addition in soil), S-MN (medium N addition in soil), S-HN (high N addition in soil), C-CK (ambient N addition on canopy), C-MN (medium N addition on canopy), and C-HN (high N addition on canopy). The total amounts of added N in the three N levels were 5.6, 15.6 and 20.6 g·m-2·a-1, respectively. Tree basal diameter and tree height were measured in June and December 2012, and November 2013. All trees were harvested in November 2013, and then the biomass was calculated according to the dry-mass of roots, shoots and leaves; the root-shoot ratios were calculated.

<i>Important findings</i>

N treatments affected seeding growth, along with significant interactive effects among N addition level, N addition regime and species. Compared to CK, S-MN stimulated the biomass in seedlings of A. mangium and S. superba, but decreased the tree height and biomass in seedlings of P. massoniana; C-MN increased the biomass in seedlings of A. mangium; S-HN promoted the biomass in seedlings of A. mangium, but significantly decreased the biomass, basal diameter and tree height in seedlings of P. massoniana (p < 0.01); C-HN led to the greater growth in seedlings of A. mangium, S. superba and P. massoniana (p < 0.01). N addition responses were dependent upon plant species: while seedlings in O. pinnata and A. mangium grew faster than S. superba and P. massoniana under all N treatments, the differences in the growth of S. superba and P. massoniana seedlings between the two N addition regimes were more pronounced than in O. pinnata and A. mangium seedlings. We concluded that legumes (O. pinnata and A. mangium) grew faster than non-legumes (S. superba). And growth stimulation in broadleaved trees (O. pinnata, A. mangium, and S. superba) by N addition was significantly greater than in coniferous trees (P. massoniana). Our findings suggest that the relatively high and chronic atmospheric N deposition in subtropical forest ecosystems may lead to changes in species composition.

Key words: biomass, high N addition levels, legumes, N addition on the canopy