Chin J Plan Ecolo ›› 2016, Vol. 40 ›› Issue (4): 318-326.DOI: 10.17521/cjpe.2015.1080

• Research Articles • Previous Articles     Next Articles

Carbon density characteristics of sparse Ulmus pumila forest and Populus simonii plantation in Onqin Daga Sandy Land and their relationships with stand age

Wei ZHAO1,2, Zhong-Min HU1, Hao YANG1,*(), Lei-Ming ZHANG1, Qun GUO1, Zhi-Yan WU3, De-Yi LIU3, Sheng-Gong LI1   

  1. 1Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

    2University of Chinese Academy of Sciences, Beijing 100049, China
    and
    3Chifeng Academy of Forestry, Chifeng, Nei Mongol 024000, China
  • Received:2015-03-10 Accepted:2015-09-08 Online:2016-04-29 Published:2016-04-30
  • Contact: Hao YANG

Abstract:

Aims
Sparse Ulmus pumila forest is an intrazonal vegetation in Onqin Daga Sandy Land, while Populus simonii has been widely planted for windbreak and sand dune stabilization in the same region. Our objective was to compare the differences in carbon (C) density of these two forests and their relationships with stand age.
Methods
We measured the C content of tree organs (leaf, twig, stem, and root), herb layers (above ground vegetation and below ground root) and soil layers (up to 100 cm) in sparse Ulmus pumila forests and Populus simonii plantations of different stand ages, and then computed C density and their proportions in total ecosystem carbon density. In addition, we illustrated the variation in carbon density-stand age relationship for tree layer, soil layer and whole ecosystem. We finally estimated the C sequestration rates for these two forests by the space-for-time substitution approach.
Important findings
The average C contents of tree layer and soil layer for sparse Ulmus pumila forests were lower than those for Populus simonii plantations. The total C density of sparse Ulmus pumila forests was half of that of Populus simonii plantations. The carbon density of soil and tree layers accounted for more than 98% of ecosystem C density in the two forests. Irrespective of forest type, the C density ratios of soil to vegetation decreased with stand age. This ratio was 1.66 for sparse Ulmus pumila forests and 1.87 for Populus simonii plantations when they were over-matured. The C density of tree layer, soil layer, and total ecosystem in both forests increased along forest development. There were significantly positive correlations between tree layer’s C density and stand age in both forests and between the total ecosystem C density of sparse Ulmus pumila forests and stand age. The C sequestration rate of tree layer was 5-fold higher in Populus simonii plantation than in sparse Ulmus pumila forest. The ecosystem-level C sequestration rate was 0.81 Mg C·hm-2·a-1 for sparse Ulmus pumila forest and 5.35 Mg C·hm-2·a-1 for Populus simonii plantation. These findings have implications for C stock estimation of sandy land forest ecosystems and policy-making of ecological restoration and C sink enhancement in the studied area.

Key words: carbon content, carbon density, carbon sequestration rate, Populus simonii plantation, sparse Ulmus pumila forest, stand age