Research ArticleCLIMATOLOGY

Water scaling of ecosystem carbon cycle feedback to climate warming

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Science Advances  21 Aug 2019:
Vol. 5, no. 8, eaav1131
DOI: 10.1126/sciadv.aav1131
  • Fig. 1 Conceptual diagram of warming effects on ecosystem C fluxes above and below the SWC optimum.

    The red arrows represent the directly positive warming effect on ecosystem C fluxes. The black arrows represent the effect of warming-induced changes in SWC on C fluxes, which is the indirect effect of warming. Below the SWC optimum, the warming-induced decrease in SWC reduces C fluxes; thus, the black arrow points downward along the SWC-C flux response curve. Above the SWC threshold, warming-induced water loss increases C fluxes; thus, the indirect warming effect enhances C fluxes, and the black arrow points upward along the SWC-C flux response curve. The blue dashed arrows represent the final change direction of C fluxes under the combination of both direct and indirect effects of warming. The photograph depicts our field experimental plots at the study site. (Photo credit: Q.Q., Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences).

  • Fig. 2 Response surfaces showing the relationships between ST and SWC versus GEP, ER, or NEP across plots and years.

    Observed values (black crosses) are the means of five replications of C fluxes, and modeled values (colored surfaces) are predictions from the models fitted with observations.

  • Fig. 3 Response surfaces showing the relationships between ST and SWC versus ecosystem C fluxes (i.e., GEP, ER, and NEP) across plots and years.

    Observed values (bubbles) are the means of each measurement of GEP, ER, and NEP. Modeled values (colored response surfaces with contour lines) are predictions from the models fitted with observations. The red arrows represent the effects of increasing temperature, and the black arrows indicate those of warming-induced decrease in SWC. The blue dashed arrows represent the potential changes of ecosystem C fluxes in combination of the two driving forces of changing ST and SWC.

  • Fig. 4 The simulated changes in GEP, ER, and NEP caused by warming-induced increasing ST (red line), warming-induced decrease in SWC (black line), and the combination effects of ST and SWC (ST + SWC, blue line) under two warming treatments (W1.5 and W2.5).

  • Fig. 5 Global synthesis of experimental warming-induced relative changes in NEP with ambient precipitation.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/8/eaav1131/DC1

    Table S1. Site information in global meta-analysis.

    Table S2. Effects of mean annual precipitation (MAP), mean annual temperature (MAT), experimental warming magnitude, duration, and their interactions on relative changes in NEP across global herbaceous ecosystems with a linear mixed-effect model.

    Table S3. Repeated-measures ANOVA results (F values) on the effects of warming (W), year (Y), and their interactions on GEP, ER, NEP, ST (Tsoil), and moisture (Msoil).

    Table S4. Repeated-measures ANOVA results (F values) on the effects of warming (W), measured time (T), and their interactions on GEP, ER, NEP, ST (Tsoil), and moisture (Msoil) in 2014–2016.

    Table S5. Comparison of the nonthreshold and threshold models based on the AIC for GEP, ER, and NEP.

    Table S6. Coefficients of threshold model (means and 95% confidence intervals) (Eq. 4).

    Fig. S1. Seasonal dynamics and means of ST and SWC at 10-cm depth under three warming treatments in 2014 to 2016.

    Fig. S2. Seasonal means of GEP, ER, and NEP under different warming treatments in 2014 to 2016.

    Fig. S3. Warming-induced changes in GEP, ER, and NEP within the year.

    Fig. S4. Relationships between ST and GEP, ER, or NEP across seasons and plots.

    Fig. S5. Relationships between warming-induced response ratio of ecosystem carbon fluxes with monthly precipitation.

    Fig. S6. The relationship between response ratio of monthly mean SWC and monthly precipitation in a precipitation gradient experiment at our study site from 2015 to 2016.

    Fig. S7. Relationships between the modeled and observed values of carbon fluxes with 1:1 line.

    Fig. S8. Relationships between SWC and ecosystem C fluxes within peak growing seasons (July and August).

    References (4165)

  • Supplementary Materials

    This PDF file includes:

    • Table S1. Site information in global meta-analysis.
    • Table S2. Effects of mean annual precipitation (MAP), mean annual temperature (MAT), experimental warming magnitude, duration, and their interactions on relative changes in NEP across global herbaceous ecosystems with a linear mixed-effect model.
    • Table S3. Repeated-measures ANOVA results (F values) on the effects of warming (W), year (Y), and their interactions on GEP, ER, NEP, ST (Tsoil), and moisture (Msoil).
    • Table S4. Repeated-measures ANOVA results (F values) on the effects of warming (W), measured time (T), and their interactions on GEP, ER, NEP, ST (Tsoil), and moisture (Msoil) in 2014–2016.
    • Table S5. Comparison of the nonthreshold and threshold models based on the AIC for GEP, ER, and NEP.
    • Table S6. Coefficients of threshold model (means and 95% confidence intervals) (Eq. 4).
    • Fig. S1. Seasonal dynamics and means of ST and SWC at 10-cm depth under three warming treatments in 2014 to 2016.
    • Fig. S2. Seasonal means of GEP, ER, and NEP under different warming treatments in 2014 to 2016.
    • Fig. S3. Warming-induced changes in GEP, ER, and NEP within the year.
    • Fig. S4. Relationships between ST and GEP, ER, or NEP across seasons and plots.
    • Fig. S5. Relationships between warming-induced response ratio of ecosystem carbon fluxes with monthly precipitation.
    • Fig. S6. The relationship between response ratio of monthly mean SWC and monthly precipitation in a precipitation gradient experiment at our study site from 2015 to 2016.
    • Fig. S7. Relationships between the modeled and observed values of carbon fluxes with 1:1 line.
    • Fig. S8. Relationships between SWC and ecosystem C fluxes within peak growing seasons (July and August).
    • References (4165)

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