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Temperature response of soil respiration in a Chinese pine plantation: hysteresis and seasonal vs. diel Q10.

Jia X, Zha T, Wu B, Zhang Y, Chen W, Wang X, Yu H, He G - PLoS ONE (2013)

Bottom Line: Progress on these issues will contribute to reduced uncertainties in carbon cycle modeling.The hysteresis may be associated with the confounding effects of microbial population dynamics and/or litter input.In addition, daily Q10 decreased with increasing Ts , which may contribute feedback to the climate system under global warming scenarios.

View Article: PubMed Central - PubMed

Affiliation: School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.

ABSTRACT
Although the temperature response of soil respiration (Rs ) has been studied extensively, several issues remain unresolved, including hysteresis in the Rs -temperature relationship and differences in the long- vs. short-term Rs sensitivity to temperature. Progress on these issues will contribute to reduced uncertainties in carbon cycle modeling. We monitored soil CO2 efflux with an automated chamber system in a Pinus tabulaeformis plantation near Beijing throughout 2011. Soil temperature at 10-cm depth (Ts ) exerted a strong control over Rs , with the annual temperature sensitivity (Q10) and basal rate at 10°C (Rs10) being 2.76 and 1.40 µmol m(-2) s(-1), respectively. Both Rs and short-term (i.e., daily) estimates of Rs10 showed pronounced seasonal hysteresis with respect to Ts , with the efflux in the second half of the year being larger than that early in the season for a given temperature. The hysteresis may be associated with the confounding effects of microbial population dynamics and/or litter input. As a result, all of the applied regression models failed to yield unbiased estimates of Rs over the entire annual cycle. Lags between Rs and Ts were observed at the diel scale in the early and late growing season, but not in summer. The seasonality in these lags may be due to the use of a single Ts measurement depth, which failed to represent seasonal changes in the depth of CO2 production. Daily estimates of Q10 averaged 2.04, smaller than the value obtained from the seasonal relationship. In addition, daily Q10 decreased with increasing Ts , which may contribute feedback to the climate system under global warming scenarios. The use of a fixed, universal Q10 is considered adequate when modeling annual carbon budgets across large spatial extents. In contrast, a seasonally-varying, environmentally-controlled Q10 should be used when short-term accuracy is required.

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Relationships between daily mean soil respiration (Rs) and soil temperature (Ts).Ts was monitored at 10-cm depth. Open circles are from January to June; closed circles are from July to December. The solid lines are fitted by a Q10 model; the dashed lines are fitted by a logistic model. Rs is significantly different between the first and second half of the year when the F-test gives P<0.05.
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pone-0057858-g002: Relationships between daily mean soil respiration (Rs) and soil temperature (Ts).Ts was monitored at 10-cm depth. Open circles are from January to June; closed circles are from July to December. The solid lines are fitted by a Q10 model; the dashed lines are fitted by a logistic model. Rs is significantly different between the first and second half of the year when the F-test gives P<0.05.

Mentions: All four models of the seasonal Rs–Ts relationship performed well (Table 1). The three-parameter logistic model performed slightly better than the others, with consistently higher R2 and lower RMSE. However, the annual model fits were unable to capture the pronounced seasonal hysteresis that was evident in the daily data, with Rs in the second half of the season being larger than that in the first half at a given Ts (Fig. 2). Significant seasonal hysteresis in the Rs–Ts relationship was observed for all sampling locations (and also for the spatial averages), with greater magnitudes for locations #1–3 than #4–5 (Fig. 2). As a result, the most commonly cited Q10 model and the best-fit logistic model both failed to yield unbiased Rs estimates over the entire annual cycle. The Q10 model captured daily Rs in autumn well, but overestimated Rs in spring (Fig. 3A). In contrast, the logistic model underestimated daily Rs in late autumn (Fig. 3B). The Rs_modeled vs. Rs_measured regression line significantly deviated from the 1 1 line according to the 95% CI for the slopes and intercepts (Fig. 3D, E). The estimation was greatly improved by fitting the Q10 model separately for each month (Fig. 3C). Monthly estimation enhanced the R2 of the Rs_modeled vs. Rs_measured relationship, reduced the RMSE, and made the relationship closer to the 1 1 line (Fig. 3F). Temperature normalized Rs (RsN, the ratio of observed to modeled values) for both the annual best-fit logistic model and monthly Q10 models were independent of VWC (results not shown).


Temperature response of soil respiration in a Chinese pine plantation: hysteresis and seasonal vs. diel Q10.

Jia X, Zha T, Wu B, Zhang Y, Chen W, Wang X, Yu H, He G - PLoS ONE (2013)

Relationships between daily mean soil respiration (Rs) and soil temperature (Ts).Ts was monitored at 10-cm depth. Open circles are from January to June; closed circles are from July to December. The solid lines are fitted by a Q10 model; the dashed lines are fitted by a logistic model. Rs is significantly different between the first and second half of the year when the F-test gives P<0.05.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585128&req=5

pone-0057858-g002: Relationships between daily mean soil respiration (Rs) and soil temperature (Ts).Ts was monitored at 10-cm depth. Open circles are from January to June; closed circles are from July to December. The solid lines are fitted by a Q10 model; the dashed lines are fitted by a logistic model. Rs is significantly different between the first and second half of the year when the F-test gives P<0.05.
Mentions: All four models of the seasonal Rs–Ts relationship performed well (Table 1). The three-parameter logistic model performed slightly better than the others, with consistently higher R2 and lower RMSE. However, the annual model fits were unable to capture the pronounced seasonal hysteresis that was evident in the daily data, with Rs in the second half of the season being larger than that in the first half at a given Ts (Fig. 2). Significant seasonal hysteresis in the Rs–Ts relationship was observed for all sampling locations (and also for the spatial averages), with greater magnitudes for locations #1–3 than #4–5 (Fig. 2). As a result, the most commonly cited Q10 model and the best-fit logistic model both failed to yield unbiased Rs estimates over the entire annual cycle. The Q10 model captured daily Rs in autumn well, but overestimated Rs in spring (Fig. 3A). In contrast, the logistic model underestimated daily Rs in late autumn (Fig. 3B). The Rs_modeled vs. Rs_measured regression line significantly deviated from the 1 1 line according to the 95% CI for the slopes and intercepts (Fig. 3D, E). The estimation was greatly improved by fitting the Q10 model separately for each month (Fig. 3C). Monthly estimation enhanced the R2 of the Rs_modeled vs. Rs_measured relationship, reduced the RMSE, and made the relationship closer to the 1 1 line (Fig. 3F). Temperature normalized Rs (RsN, the ratio of observed to modeled values) for both the annual best-fit logistic model and monthly Q10 models were independent of VWC (results not shown).

Bottom Line: Progress on these issues will contribute to reduced uncertainties in carbon cycle modeling.The hysteresis may be associated with the confounding effects of microbial population dynamics and/or litter input.In addition, daily Q10 decreased with increasing Ts , which may contribute feedback to the climate system under global warming scenarios.

View Article: PubMed Central - PubMed

Affiliation: School of Soil and Water Conservation, Beijing Forestry University, Beijing, China.

ABSTRACT
Although the temperature response of soil respiration (Rs ) has been studied extensively, several issues remain unresolved, including hysteresis in the Rs -temperature relationship and differences in the long- vs. short-term Rs sensitivity to temperature. Progress on these issues will contribute to reduced uncertainties in carbon cycle modeling. We monitored soil CO2 efflux with an automated chamber system in a Pinus tabulaeformis plantation near Beijing throughout 2011. Soil temperature at 10-cm depth (Ts ) exerted a strong control over Rs , with the annual temperature sensitivity (Q10) and basal rate at 10°C (Rs10) being 2.76 and 1.40 µmol m(-2) s(-1), respectively. Both Rs and short-term (i.e., daily) estimates of Rs10 showed pronounced seasonal hysteresis with respect to Ts , with the efflux in the second half of the year being larger than that early in the season for a given temperature. The hysteresis may be associated with the confounding effects of microbial population dynamics and/or litter input. As a result, all of the applied regression models failed to yield unbiased estimates of Rs over the entire annual cycle. Lags between Rs and Ts were observed at the diel scale in the early and late growing season, but not in summer. The seasonality in these lags may be due to the use of a single Ts measurement depth, which failed to represent seasonal changes in the depth of CO2 production. Daily estimates of Q10 averaged 2.04, smaller than the value obtained from the seasonal relationship. In addition, daily Q10 decreased with increasing Ts , which may contribute feedback to the climate system under global warming scenarios. The use of a fixed, universal Q10 is considered adequate when modeling annual carbon budgets across large spatial extents. In contrast, a seasonally-varying, environmentally-controlled Q10 should be used when short-term accuracy is required.

Show MeSH
Related in: MedlinePlus