『Abstract
We review measured rates of soil respiration from terrestrial
and wetland ecosystems to define the annual global CO2
flux from soils, to identify uncertainties in the global flux
estimate, and to investigate the influences of temperature, precipitation,
and vegetation on soil respiration rates. The annual global CO2 flux from soils is estimated to average (±S.D.)
68±4 PgC/yr, based on extrapolations from biome land areas. Relatively
few measurements of soil respiration exist from arid, semi-arid,
and tropical regions; these regions should be priorities for additional
research. On a global scale, soil respiration rates are positively
correlated with mean annual air temperatures and mean annual precipitation.
There is a close correlation between mean annual net primary productivity
(NPP) of different vegetation biomes and their mean annual soil
respiration rates, with soil respiration averaging 24％ higher
than mean annual NPP. This difference represents a minimum estimate
of the contribution of root respiration to the total soil CO2 efflux. estimates of soil C turnover rates range
from 500 years in tundra and peaty wetlands to 10 years in tropical
savannas. we also evaluate the potential impacts of human activities
on soil respiration rates, with particular focus on land use changes,
soil fertilization, irrigation and drainage, and climate changes.
The impacts of human activities on soil respiration rates are
poorly documented, and vary among sites. Of particular importance
are potential changes in temperatures and precipitation. Based
on a review of in situ measurements, the Q10
value for total soil respiration has a median value of 2.4. Increased
soil respiration with global warming is likely to provide a positive
feedback to the greenhouse effect.』
1. Introduction
2. Soil respiration as an ecosystem process
3. Global patterns of soil respiration
3.1. Selection of data
3.2. Soil respiration in major vegetation biomes
3.3. Climatic controls over soil respiration
3.4. Global soil respiration
4. Soil carbon turnover
5. Human impacts on soil respiration rates
5.1. Land use changes
5.2. Fertilization
5.3. Irrigation and drainage
5.4. Temperature changes
6. Summary and conclusions
7. Acknowledgments
Appendix. Annual soil respiration rates (gC・m-2・yr-1)
in the world's major terrestrial biomes
References