Chin J Plan Ecolo ›› 2014, Vol. 38 ›› Issue (10): 1053-1063.doi: 10.3724/SP.J.1258.2014.00099

• Research Articles • Previous Articles     Next Articles

Effects of elevated CO2 concentration and nitrogen addition on soil carbon stability in southern subtropical experimental forest ecosystems

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

  1. 1South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;

    2University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2014-03-04 Revised:2014-07-11 Online:2014-10-22 Published:2014-10-01
  • Contact: LIU Ju-Xiu E-mail:ljxiu@scbg.ac.cn

Abstract:

Aims The influence of elevated atmospheric CO2 concentration and nitrogen (N) addition on soil carbon pool is one of the foci among international ecological research communities. The changes of soil carbon pool induced by atmospheric CO2 concentration and/or N deposition will lead to changes in atmospheric carbon pool and thus the global climate change. However, few studies have been carried out in the subtropical China. Our objective was to understand the effect of elevated CO2 concentration and N addition on soil carbon stability in south subtropical experimental forests.
Methods Experimental forest ecosystems were constructed in open top chambers. Six native tree species in southern China were planted in these experimental forest ecosystems. The species were exposed to elevated CO2 and N addition in the open top chambers beginning in May 2005. The four treatments were: elevated CO2 and high N addition (CN), elevated CO2 and ambient N deposition (CC), high N addition and ambient CO2 (NN), and ambient CO2 and ambient N deposition (CK). The elevated CO2 was (700 ± 20) μmol·mol–1. The total amount of added NH4NO3-N was 100 kg N·hm–2·a–1. In January 2010, soil samples were collected from the open top chambers and then relevant variables were measured.
Important findings Elevated CO2 concentration and N addition (CN) effectively increased the soil total organic carbon in different soil layers, among which the increases in the lower soil layers (5–60 cm) were statistically significant. Different components of the active organic carbon pool differed in the responses to treatments. The differences in microbial biomass carbon were significant in the 0–5 cm, 5–10 cm and 10–20 cm soil layers among the treatments, and the readily oxidized carbon showed significant responses to the elevated CO2 concentration and N addition treatments in the 10–20 cm and 20–40 cm soil layers, while there was no significant difference in the dissolved organic carbon among different treatments in all the soil layers. The responses of carbon in different aggregate fractions differed among the treatments. The carbon in the 250–2 000 μm aggregates was significantly different among treatments in the 20–40 cm and 40–60 cm soil layers. The carbon in the 53–250 μm aggregates was susceptible to treatments in the 40–60 cm soil layer as both the CC and NN treatments facilitated the chronic carbon accumulation in deeper soil layers, especially under the CN treatment. Carbon in the <53 μm fraction showed significant differences among treatments in deeper soil layers (10–20 cm, 20–40 cm and 40–60 cm). In conclusion, elevated CO2 concentration and N addition increased soil organic carbon in the experimental forest ecosystems, and facilitated the accumulation of carbon in micro-aggregates and silt-clay fraction in deep soil layers, thus strengthened the stability of soil organic carbon pool.

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