Warming effects on ecosystem carbon fluxes are modulated by plant functional types
Ji Chen1,2,3,4, Yiqi Luo4,5, Jianyang Xia6,7, Kevin R. Wilcox4, Junji Cao2,8*, Xuhui Zhou6,7*, Lifen Jiang4, Shuli Niu9, KaterinaY. Estera10, Rujin Huang2, Feng Wu2, Tafeng Hu2, Junyi Liang4, Zheng Shi4, Jianfen Guo11, Ruiwu Wang1*
1Center for Ecological and Environmental Sciences, Northwestern Polytechnical University, Xi’an 710072, China, 2State Key Laboratory of Loess and Quaternary Geology (SKLLQG), and Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China; 3University of Chinese Academy of Sciences, Beijing, 100049, China; 4Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA; 5Center for Earth System Science, Tsinghua University, Beijing, 100084, China; 6Tiantong National Field Observation Station for Forest Ecosystem, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, 200062, China; 7Center for Global Change and Ecological Forecasting, East China Normal University, Shanghai, 200062, China; 8Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an 710049, China; 9Synthesis Research Center of Chinese Ecosystem Research Network, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;10Department of Environmental Science, Policy and Management, University of California at Berkeley, Berkeley, California, 94720 U.S.A; 11College of Geographical Science, Fujian Normal University, Fuzhou 350007, China.
*Corresponding author:
Junji Cao, , Tel: +86-29-62336233, Fax: +86-29-62336234;
Xuhui Zhou, , Tel: +86-21-54341275, Fax: +86-21-54341275;
Ruiwu Wang, , Tel: +86-29-88460816, Fax: +86-29-62336234.
Supplementary tables and figures
Table S1 The effects of warming on relative coverage (RC), relative height (RH), relative abundance (RA), and importance values (IV) for each species.
Species / Life / PFTs / RC / RH / RA / IVControl / Warm / Control / Warm / Control / Warm / Control / Warm
Stipa capillataLinn / Per / Graminoid / 12.76±0.23 / 13.25±0.18 / 11.72±0.07 / 12.02±0.11* / 11.34±0.18 / 11.93±0.13* / 11.94±0.09 / 12.4±0.08**
Leymus secalinus / Per / Graminoid / 7.09±0.33 / 8.36±0.23* / 13.35±0.12 / 13.65±0.13 / 9.22±0.24 / 9.85±0.16* / 9.89±0.11 / 10.62±0.09**
Koeleria cristata / Per / Graminoid / 9.59±0.22 / 10.6±0.22* / 11.57±0.15 / 11.76±0.16 / 9.78±0.15 / 10.16±0.15 / 10.31±0.14 / 10.84±0.12*
Poa crymophila / Per / Graminoid / 9.48±0.18 / 10.31±0.24* / 9.82±0.09 / 10.18±0.11* / 11.11±0.12 / 11.46±0.09* / 10.14±0.08 / 10.65±0.09**
Kobresia humilis / Per / Graminoid / 12.53±0.23 / 12.99±0.27 / 6.34±0.11 / 6.72±0.09* / 11.13±0.18 / 11.98±0.15** / 10±0.11 / 10.56±0.12**
Carex humilis Leys / Per / Graminoid / 6.09±0.22 / 6.4±0.16 / 6.1±0.12 / 6.55±0.10* / 7.76±0.15 / 8.15±0.15 / 6.65±0.09 / 7.03±0.05**
Medicago ruthenica / Per / Legume / 10.04±0.21 / 11.32±0.23** / 3.86±0.19 / 4.33±0.19* / 9.02±0.13 / 9.29±0.12 / 7.64±0.09 / 8.32±0.08**
Astragalus floridus / Per / Legume / 7.46±0.25 / 8.24±0.20* / 4.75±0.1 / 5.34±0.09** / 9.12±0.11 / 8.91±0.12 / 7.11±0.09 / 7.5±0.08*
Heteropappus altaicus / Per / Forb / 4.42±0.1 / 4.19±0.12 / 6.34±0.14 / 6.05±0.12 / 4.56±0.13 / 4.25±0.13 / 5.1±0.06 / 4.83±0.06*
Artemisia scoparia / Per / Forb / 4.34±0.2 / 3.57±0.13* / 6.05±0.17 / 5.56±0.17* / 2.56±0.11 / 2.64±0.11 / 4.32±0.09 / 3.92±0.08*
Stellera chamaejasme / Per / Forb / 2.33±0.15 / 1.71±0.11* / 5.03±0.14 / 4.56±0.13* / 1.82±0.15 / 1.43±0.05* / 3.06±0.08 / 2.56±0.07**
Taraxacum mongolicum / Per / Forb / 2.91±0.17 / 2.05±0.09** / 4.28±0.24 / 3.84±0.2 / 2.3±0.12 / 1.63±0.06** / 3.16±0.08 / 2.51±0.07**
Potentilla multicaulis / Ann / Forb / 4.49±0.21 / 2.65±0.14** / 4.18±0.13 / 3.76±0.12* / 2.81±0.09 / 2.32±0.07** / 3.83±0.09 / 2.91±0.06**
Bupleurum marginatum / Ann / Forb / 3.33±0.17 / 2.34±0.16** / 4.34±0.11 / 3.62±0.11** / 2.74±0.15 / 2.14±0.14* / 3.47±0.09 / 2.7±0.08**
Gentiana scabra / Ann / Forb / 3.16±0.23 / 2.03±0.14** / 2.29±0.11 / 2.04±0.1 / 4.75±0.18 / 3.86±0.14** / 3.4±0.08 / 2.65±0.07**
Note: Per:perennial; Ann: annual; PFTs: plant functional types; RC: relative coverage; RH: relative height; RA: relative abundance; IV: importance value. IV was calculated as the average value of RC, RH and RA. ** indicates significant difference at p0.01, and * indicates significant difference at p0.05.
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Table S2.Regression equationsfor estimating aboveground net primary productivity.
PFT1 / Regression model2 / R2 / FGraminoids / Y=13.737+1.476C+2.641H / 0.921 / 295.732**
Legumes / Y=-12.472+1.493C+4.497H / 0.966 / 727.133**
Forbs / Y=-0.411+2.876C+1.302H / 0.689 / 56.604**
AGB / Y=-26.236+2.242C+7.216H / 0.947 / 454.701**
1PFT stands for plant functional type.
2C: coverage; H: height; Y: plant biomass
**: significant at p < 0.01.
Table S3 Results (F values) of two way ANOVA analysis of the effects of warming (W), year (Y), and their interactive (W×Y) effects on seasonal variations of gross primary productivity, ecosystem respiration andnet ecosystem exchange. **indicates significant difference at p 0.01, *indicates significant difference at p < 0.05.Data were averaged for each month over the three warming years.
May / June / July / August / September / OctoberGross primary productivity
W / 30.546** / 21.051** / 10.019* / 22.753** / 14.224* / 14.075*
Y / 19.565** / 26.077** / 9.027* / 61.252** / 9.904* / 1.4
W×Y / 1.504 / 1.11 / 0.56 / 4.309* / 0.127 / 0.061
Ecosystem respiration
W / 2.227 / 3.346 / 1.902 / 4.524* / 2.156* / 6.236*
Y / 2.036 / 34.551** / 32.232** / 88.121** / 4.235* / 17.277**
W×Y / 0.175 / 1.272 / 2.051 / 0.767 / 0.289 / 0.904
Net ecosystem exchange
W / 25.259** / 15.072** / 6.980* / 22.652** / 11.484* / 13.133*
Y / 29.869** / 44.959** / 18.726** / 140.132** / 6.994* / 1.594
W×Y / 1.071 / 1.152 / 0.955 / 3.124 / 0.142 / 0.036
Figure S1 Daily precipitation (a) and air temperature (b) at the experimental site from 2011 to 2013.
Figure S2 Warming-induced increases in gross primary productivity (GPP, a), ecosystem respiration (ER, b) and net ecosystem exchange (NEE, c). Values are mean ± standard errors for six replicates. * indicates significant difference at p0.05. Negative values of NEE indicated that warming enhanced C uptake.
Figure S3Relationship betweengross primary productivity (GPP), ecosystem respiration (ER),net ecosystem exchange (NEE) and soil temperature, soil moisture both in control and warming treatments.Negative values represent net carbon uptake from the ecosystem, and positive values represent net carbon release.
Figure S4 Relationship between warming-induced seasonal changes in net ecosystem exchange (NEE), ecosystem respiration (ER), gross primary productivity (GPP) and warming-induced changes in soil temperature (a), soil moisture (b). Relationship between warming-induced annual changes in net ecosystem exchange (NEE), ecosystem respiration (ER), gross primary productivity (GPP) and warming-induced changes in soil temperature (c), soil moisture (d).The delta terms indicate the difference between the OTC and control, for example, Soil temperature = OTC (Soil temperature)-Control (Soil temperature).Negative values ofΔNEE indicate that warming enhanced C uptake, negative values ofΔGPP indicate that warming suppressed C uptake, and negative values of ΔER indicate that warming decreased C respiration.
Figure S5. Variations of soil temperature (A, B, and C) and soil moisture (D, E, and F) at 10 cm induced by open top chambers during the three growing seasons. Variations were calculated as the difference between the experimental warming and control treatments.
Figure S6 Relationships between warming-induced changes in soil total inorganic nitrogen (TIN, a) and legume biomass (b) and warming-induced changes in aboveground biomass (AGB), graminoid, legumeand forbbiomass.
Figure S7 Relationships between warming-induced changes in AGB and the corresponding changes in ecosystem Cfluxes.Negative values ofΔNEE indicate that warming enhanced C uptake, negative values ofΔGPP indicate that warming suppressed C uptake, and negative values of ΔER indicate that warming decreased C respiration.
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