Carbon dioxide emission derived from soil organic matter decomposition and root respiration in Japanese forests under different ecological conditions

Abstract

Soil chambers with 3 types of soil treatment were used to analyze the environmental factors controlling carbon dioxide (CO₂) emission in forest soils of Japan and to separately determine CO₂ emission from root respiration, microbial decomposition of organic matter in the O layer and in the mineral soil layers. Soil chambers were installed at the Kyoto, Miyazu-Oak, Miyazu-Cedar, Miyazu-Beech and Nobeyama sites; the sites differed from each other in soil temperature, vegetation and parent materials. The soil treatments applied at each of the 5 sites were as follows: (1) control plot, (2) O- plot with removal of the O layer, (3) root- plot with the suppression of root respiration by inserting the chambers to a depth of 20 cm and sealing the bottom. The CO₂ emission levels at all sites were significantly correlated with soil temperature, but not with soil moisture levels. The annual rates of soil organic matter decomposition simulated based on the automatically recorded soil temperature were 5.1, 4.0, 5.2, 5.5 and 3.4 Mg C ha⁻¹ at the Kyoto, Miyazu-Oak, Miyazu-Cedar, Miyazu-Beech and Nobeyama sites, respectively. These rates were influenced by soil temperature, litter fall rates and the carbon stocks. In contrast, the ratio of the annual rate of root respiration to the annual rate of soil respiration decreased as soil temperature decreased. Based on the carbon budget, the Miyazu-Cedar and Nobeyama sites appeared to have lost their soil carbon stock. For more accurate analysis, methods for the direct measurement of the input rate of root litter should be developed.

Key words:

• carbon stock
• forest ecosystem
• root respiration
• soil organic matter decomposition
• soil respiration

ACKNOWLEDGMENTS

A part of this study was funded by a Grant-in-Aid for Scientific Research (A) from the Japan Society for the Promotion of Science, “Establishment of a carbon budget model of the soil ecosystem for the control of global warming.” The authors also thank the Yoshida Shrine, the Kinki and Chugoku Regional Forest Office of the Ministry of Agriculture, Forestry and Fisheries of Japan, and the Yatsugatake University Forest of the Tsukuba University for allowing them to conduct studies at the experimental sites.

Notes

Present addresses: Tsukishima Kikai Company, 2-17-5 Tsukuda, Chuo, Tokyo 104-0051, Japan

Tsukuba Botanical Garden, National Science Museum, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan