Abstract
BackgroundAlthough semi-arid and arid regions account for about 40% of terrestrial surface of the Earth and contain approximately 10% of the global soil organic carbon stock, our understanding of soil organic carbon dynamics in these regions is limited.Methodology/Principal FindingsA field experiment was conducted to compare soil organic carbon dynamics between a perennial grass community dominated by Cleistogenes squarrosa and an adjacent shrub community co-dominated by Reaumuria soongorica and Haloxylon ammodendron, two typical plant life forms in arid ecosystems of saline-alkaline arid regions in northwestern China during the growing season 2010. We found that both fine root biomass and necromass in two life forms varied greatly during the growing season. Annual fine root production in the perennial grasses was 45.6% significantly higher than in the shrubs, and fine root turnover rates were 2.52 and 2.17 yr−1 for the perennial grasses and the shrubs, respectively. Floor mass was significantly higher in the perennial grasses than in the shrubs due to the decomposition rate of leaf litter in the perennial grasses was 61.8% lower than in the shrubs even though no significance was detected in litterfall production. Soil microbial biomass and activity demonstrated a strong seasonal variation with larger values in May and September and minimum values in the dry month of July. Observed higher soil organic carbon stocks in the perennial grasses (1.32 Kg C m−2) than in the shrubs (1.12 Kg C m−2) might be attributed to both greater inputs of poor quality litter that is relatively resistant to decay and the lower ability of microorganism to decompose these organic matter.Conclusions/SignificanceOur results suggest that the perennial grasses might accumulate more soil organic carbon with time than the shrubs because of larger amounts of inputs from litter and slower return of carbon through decomposition.
Highlights
Soil carbon pool, as the major part of the terrestrial carbon reservoir, plays a critical, yet poorly understood role in the global carbon cycle [1]
Semi-arid and arid regions, which are sensitive to global change, account for about 40% of the terrestrial surface of Earth [3,4] and contain approximately 10% of the global soil organic carbon stock [5]
The vertical distribution of fine root biomass significantly increased with soil depths in the perennial grasses, while in the shrubs fine root biomass was highest in 10–20 cm of the soil profile in the growing season (Fig. 2a, c)
Summary
As the major part of the terrestrial carbon reservoir, plays a critical, yet poorly understood role in the global carbon cycle [1]. The study of soil carbon dynamics is crucial to our ability to understand the global carbon cycle and its response to future global change [2]. Semi-arid and arid regions, which are sensitive to global change, account for about 40% of the terrestrial surface of Earth [3,4] and contain approximately 10% of the global soil organic carbon stock [5]. Fine root production contributes to about 33% of annual net primary productivity and its turnover directly impacts the biogeochemical cycle and sequestration of carbon [7,8]. Semi-arid and arid regions account for about 40% of terrestrial surface of the Earth and contain approximately 10% of the global soil organic carbon stock, our understanding of soil organic carbon dynamics in these regions is limited
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