Influence of freeze-thaw events on carbon dioxide emission from soils at different moisture and land use

Abstract

BackgroundThe repeated freeze-thaw events during cold season, freezing of soils in autumn and thawing in spring are typical for the tundra, boreal, and temperate soils. The thawing of soils during winter-summer transitions induces the release of decomposable organic carbon and acceleration of soil respiration. The winter-spring fluxes of CO2 from permanently and seasonally frozen soils are essential part of annual carbon budget varying from 5 to 50%. The mechanisms of the freeze-thaw activation are not absolutely clear and need clarifying. We investigated the effect of repeated freezing-thawing events on CO2 emission from intact arable and forest soils (Luvisols, loamy silt; Central Germany) at different moisture (65% and 100% of WHC).ResultsDue to the measurement of the CO2 flux in two hours intervals, the dynamics of CO2 emission during freezing-thawing events was described in a detailed way. At +10°C (initial level) in soils investigated, carbon dioxide emission varied between 7.4 to 43.8 mg C m-2h-1 depending on land use and moisture. CO2 flux from the totally frozen soil never reached zero and amounted to 5 to 20% of the initial level, indicating that microbial community was still active at -5°C. Significant burst of CO2 emission (1.2–1.7-fold increase depending on moisture and land use) was observed during thawing. There was close linear correlation between CO2 emission and soil temperature (R2 = 0.86–0.97, P < 0.001).ConclusionOur investigations showed that soil moisture and land use governed the initial rate of soil respiration, duration of freezing and thawing of soil, pattern of CO2 dynamics and extra CO2 fluxes. As a rule, the emissions of CO2 induced by freezing-thawing were more significant in dry soils and during the first freezing-thawing cycle (FTC). The acceleration of CO2 emission was caused by different processes: the liberation of nutrients upon the soil freezing, biological activity occurring in unfrozen water films, and respiration of cold-adapted microflora.

Effects of soil rewetting and thawing on soil gas fluxes: a review of current literature and suggestions for future research

“…Increased CO 2 flux after thawing has been observed in various terrestrial ecosystems, including forest (Wu et al, 2010a), alpine tundra (Brooks et al, 1997), and arctic heath (Elberling and Brandt, 2003), and in incubation experiments with soils from cropland (Kurganova et al, 2007), grassland (Wu et al, 2010b), forest (Goldberg et al, 2008), bog (Panikov and Dedysh, 2000), taiga and tundra (Schimel and Clein, 1996), and Antarctica (Zhu et al, 2009). Reported CO 2 flux increases after thawing can range up to 5000 % (Table 1, Fig.…”

“…The relative CO 2 flux increase following thawing in tundra (5530 %) is higher than those of cropland, forest, grassland other ecosystems (150-1630 %; Table 2). Such increases in CO 2 flux after seasonal thawing were important to the annual budget of CO 2 flux in arable soils (Priemé and Christensen, 2001;Kurganova et al, 2007), but did not affect the annual budget in some natural sites (Coxson and Cropland F: 100 ± 19 (9) * , F: 67 ± 3 (6) F: 487 ± 87 (3), F: 1008 ± 474 (5), -L: 1042 ± 503 (4) L: 68 600 ± 21 169 (7) L: 650 ± 250 (2) Desert F: 8425 ± 4625 (2) --F: 1187 ± 572 (4), F: 561 ± 182 (4), L: 2100 ± 1200 (2) L: 575 ± 85 (4) Forest F: 102 ± 26 (9), L: −538 ± 98 (3) F: 9787 ± 6528 (13) (5) L: 34 973 ± 20 571 (6) L: 2900 ± 1806 (7) Rice paddy -- Arctic heath…”

A Simple Temperature-Based Method to Estimate Heterogeneous Frozen Ground within a Distributed Watershed Model

“…Soil moisture is not considered when calculating the frost index, so it does not impact the initiation or duration of frozen ground. This limitation results from using a degree-day approach and may be important in some cases (Kurganova et al, 2007;Willis et al, 1961). Second, the modCFGI model should be tested further.…”

“…When is between these values, the ground could be 10 either frozen or thawed. It is worth noting that the does not depend on soil moisture, which is known to affect the initialization and depth of frozen ground (Kurganova et al, 2007;Willis et al, 1961).…”

“…This result highlights a deficiency in the modelling framework. Specifically, soil moisture should be considered for determining the initiation of frozen ground because wet soils have a higher specific heat capacity and require more energy to cool and freeze the soil (Kurganova et al, 2007). 5 …”