Chin J Plant Ecol ›› 2020, Vol. 44 ›› Issue (9): 973-985.DOI: 10.17521/cjpe.2020.0203

• Research Articles • Previous Articles     Next Articles

Characteristics of soil carbon and nitrogen contents and enzyme activities in sub-alpine secondary forests with different successional stages in Western Sichuan, China

HU Zong-Da1,*(), LIU Shi-Rong3, LUO Ming-Xia1, HU Jing4, LIU Xing-Liang2, LI Ya-Fei1, YU Hao1, OU Ding-Hua1   

  1. 1College of Resources, Sichuan Agricultural University, Chengdu 611130, China
    2Ecological Restoration and Conservation on Forest and Wetland Key Laboratory of Sichuan Province, Sichuan Academy of Forestry, Chengdu 610081, China
    3Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China
    4College of Resources and Environment, Hunan Agricultural University, Changsha 410128, China
  • Received:2020-06-19 Revised:2020-08-06 Online:2020-09-20 Published:2020-09-03
  • Contact: HU Zong-Da
  • Supported by:
    Supported by Forest and Wetland Ecological Restoration and Conservation of Open Project from Key Laboratory of Sichuan Province(2019KFKT03);the National Key R&D Program of China(2017YFC0505004);the Environmental Governance and Ecological Protection Major Project of Sichuan Province(2018SZDZX0031)


Aims Regeneration of sub-alpine forests have an capacity to sequester carbon and nitrogen. Our objectives were to quantify variations of soil organic carbon and nitrogen content and enzyme activities at different successional stages of natural secondary forests, and to better understand the underlying mechanisms of carbon and nitrogen sequestration in these sub-alpine forests.
Methods We used the space-for-time substitution method and selected four sub-alpine forests in Miyaluo forest of Western Sichuan, China. The secondary forests were at different successional stages with natural regeneration on cutting-blanks in 1960s (60-NSF), 1970s (70-NSF) and 1980s (80-NSF), and the Abies faxoniana primary forest was used as control (CK). The soil samples were taken from 0 to 20 cm depths in each forest in late July, 2019, and were transferred to the laboratory. Soil organic carbon (SOC), soil total nitrogen (TN), dissolved organic carbon (DOC) and nitrogen (DON), light fraction organic carbon (LFOC) content and soil enzyme activities were measured. The activities of five soil extracellular enzymes related to soil carbon and nitrogen cycling were determined to explain their relationships with soil physico-chemical properties.
Important findings The contents of topsoil SOC, DOC, LFOC decreased with succession stage, whereas TN and DON were all in the order of 60-NSF < 80-NSF < 70-NSF, although 80-NSF and 70-NSF exhibited no significant difference. The topsoil organic carbon and nitrogen and their active fractions contents in natural secondary forests were lower than those in the primary forest, while no significant difference in DOC and DON contents was observed between 80-NSF and CK. The activities of soil β-4-glucosidase (βG), β-4-N-acetylglucosa- minidase (NAG) and polyphenol oxidase (PHO) in CK were significantly higher than those in natural secondary forests, whereas soil cellulose hydrolysis (CBH) and phenol oxidase (PEO) activities had no significant difference between secondary forests and CK. Activities of βG and CBH in 60-NSF were significantly lower than those in 70-NSF and 80-NSF, but activities of NAG in 80-NSF were significantly higher than those in 60-NSFand 70-NSF. There was no significant difference in PEO activities among different types of forest. Both Pearson correlation analysis and redundancy analysis showed that soil enzyme activities were significantly correlated with soil TN, LFOC and DOC contents. TN content explained 65.4% of the variations in enzyme activity, which implied that change in soil nitrogen content might affect C-related hydrolytic enzyme activities (e.g. βG, CBH and NAG). Meanwhile soil microorganisms prefer to use readily decomposable carbon and nitrogen. Therefore, activities of some soil enzymes such as βG, CBH and NAG in natural secondary forests decreased due to the declines in soil TN, LFOC and DOC contents. We conclude that soil enzyme activities could be more favorable to C and N cycling in the Abies faxoniana primary forest than in the secondary forest at the early-successional stages (<60 a) in high-altitude sub-alpine forest ecosystems in Western Sichuan, China.

Key words: soil organic carbon, soil total nitrogen, enzyme activity, succession stage, natural secondary forest, soil carbon cycle, soil nitrogen cycle