Accepted Article
Received Date : 03-Feb-2015 Accepted Date : 29-Mar-2015 Article type : Primary Research Articles
Plant community structure regulates responses of prairie soil respiration to decadal experimental warming
Running title: plant control of soil respiration to warming
Xia Xu1,2, Zheng Shi2, Dejun Li2,3, Xuhui Zhou2,4, Rebecca A. Sherry2,5, Yiqi Luo2
1
Key Laboratory of Forestry Ecological Engineering of Jiangsu Province, College of Biology
and Environment, Nanjing Forestry University, Nanjing, Jiangsu Province, 210037, China 2
Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK,
73019, USA 3
China Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan,
410125, China 4
The Institute of Biodiversity Science and Research Institute of the Changing Global
Environment, Fudan University, Shanghai, 200433,China 5
US Geological Survey, Fort Collins Science Center, Fort Collins, CO, 80526, USA
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/gcb.12940 This article is protected by copyright. All rights reserved.
Author for Correspondence:
Xia Xu & Yiqi Luo
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101 David L. Boren Blvd., Norman, OK, 73019, USA Tel.: + 1 405-325-6519; Fax: +1 405-325-7619 E-mail address:
[email protected];
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Key words: soil respiration, warming, ecosystem production, plant community composition, tallgrass prairie
Paper type: primary research Authorship: XX analyzed the data and wrote the article. XX, ZS, and YL conceived the idea. YL designed the experiment. XX, DL, and XZ conducted the measurements. RAS performed canonical correspondence analysis.
Abstract: Soil respiration is recognized to be influenced by temperature, moisture, and ecosystem production. However, little is known about how plant community structure regulates responses of soil respiration to climate change. Here, we used a 13-year field warming experiment to explore the mechanisms underlying plant community regulation on feedbacks of soil respiration to climate change in a tallgrass prairie in Oklahoma, USA. Infrared heaters were used to elevate temperature about 2 oC since November 1999. Annual clipping was used to mimic hay harvest. Our results showed that experimental warming significantly increased soil respiration approximately from 10 % in the first 7 years (2000-2006) to 30 % in the next 6 years (2007-2012). The two-stage warming stimulation of
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of soil CO2 efflux (commonly referred to as soil respiration) to climate warming.
In the global C cycle, soil respiration is the second largest C flux between terrestrial
ecosystems and atmosphere (Raich & Schlesinger, 1992; Raich & Tufekcioglu, 2000). Concerns about climate change and its subsequent long-term impact on the global C cycle have intensified research interest in soil respiration (e.g. Rustad et al., 2001; Zhou et al., 2007; Schuur et al., 2009). Soil respiration is strongly regulated by temperature (e.g. Rustad et al., 2001; Schuur et al., 2009), as seen in observations of soil respiration in manipulative warming experiments (Melillo et al., 2002; Zhou et al., 2007). Warming usually increases soil respiration rates in the short term due to warming-accelerated decay of soil organic matter (Rustad et al., 2001; Melillo et al., 2002). Long-term responses of soil respiration to warming, however, are less clear because most manipulative experiments are too short to establish a clear trajectory of change with time (Rastetter, 1996; Rustad et al., 2001; Luo et al., 2011). Several long-term studies in forest ecosystems show that soil respiration rates returned to pre-warming levels within a few years mainly due to decreased substrate availability in soils (Rustad et al., 2001; Melillo et al., 2002). In grasslands, plant productivity usually increases under warming (Xu et al., 2012a; Lu et al., 2013), leading to increased litter input and partial counteraction of the substrate loss from organic C pools. This may create different temporal patterns in the response of soil respiration to warming with the possible scenario that respiration response to warming will continue to increase as the experiment continues.
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Each 2 m × 2 m plot is divided into four 1 m × 1 m subplots. Plants in two diagonal
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subplots are clipped at a height of 10 cm above the ground once a year to mimic hay harvest while the other two subplots are unclipped. Clipped materials are removed and not returned to the plots. Thus, the experiment has four treatments: unclipped and control (ambient) temperature (UC), unclipped and warming (UW), clipped and control temperature (CC), and clipped and warming (CW).
Microclimate and NPP measurements Precipitation data was obtained from an Oklahoma Mesonet Station (Washington Station)
located approximately 200 m away from our experimental site. Soil temperature was monitored by thermocouplers at a depth of 2.5 cm in the centers of one clipped and one unclipped subplot in each plot. Volumetric soil water content in the top 15 cm was measured once or twice a month using portable Time Domain Reflectometry (TDR) equipment (Soil Moisture Equipment Crop., Santa Barbara, CA, USA). Aboveground NPP (ANPP, separated into C3 forbs and C4 grasses) was directly measured by clipping in clipped subplots and indirectly estimated by pin-contact counts in unclipped subplots at peak biomass (usually August, Frank & McNaughton, 1990; Sherry et al., 2008). From 2005 to 2010, the root ingrowth-core (0 - 45 cm) method was applied to estimate belowground NPP (BNPP, Xu et al., 2012a). In 2000-2004 and 2011-2012, BNPP was indirectly estimated based on the correlation between ANPP and BNPP from 2005 to 2010 (BNPP=1.01*ANPP+160.64, r2=0.40, P=0.001, n=24).
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subalpine forests. Ecology, 82, 955-964.
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warming and clipping in a tallgrass prairie. Global Change Biology, 18, 1648-1656. doi: 10.1111/j.1365-2486.2012.02651.x.
Xu X, Sherry RA, Niu S, Zhou J, Luo Y (2012b) Long-term experimental warming decreased labile soil organic carbon in a tallgrass prairie. Plant Soil, 361, 307-365. Doi: 10.1007/s11104-012-1265-9.
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Zhou J, Xue K, Xie J, Deng Y, Wu L, Cheng X, Fei S, Deng S, He Z, van Nostrand JD, Luo Y (2012) Microbial mediation of carbon cycle feedbacks to climate warming. Nature Climate Change, 1331, 106-110. Figure legends Figure 1 Warming-induced increases (warmed minus un-warmed) in soil respiration per year across the 13 years. Values are mean ± SE with 12 replicates. Figure 2 Path analysis of the effects of warming-induced changes in abiotic and biotic factors on warming-induced changes in soil respiration. Solid and dashed arrows represent significant (P0.05) paths in a fitted structural equation model depicting impact of variables on soil respiration. Tair: air temperature; Tsoil: soil temperature; Wsoil: soil moisture; ANPP & BNPP: above- and below-ground net primary production; C3%: the proportion of ANPP contributed by C3 forbs; Rs: soil respiration. Yearly data are used to perform the path analysis. Figure 3 Changes in soil respiration positively affected by the proportion of ANPP
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contributed by C3 forbs under warming across the 13 years. ANPP: aboveground net primary
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production. Yearly data are used in this figure. Figure 4 Positive relationships of warming-induced changes in soil respiration with changes in the biomass of C3 forbs (A), C4 grasses (B), aboveground NPP(ANPP, C), belowground NPP (BNPP, D), and NPP (E). NPP: net primary production. Yearly data are used in this figure. Figure 5 Positive impact of the proportion of ANPP contributed by C3 forbs on aboveground net primary production (ANPP, A) and belowground net primary production (BNPP, B) under warming. Yearly data are used in this figure.
Table 1 Results of split-plot repeated-measures ANOVA (P values) for responses of soil temperature and moisture (Tsoil, Wsoil), ANPP, BNPP, and soil respiration (Rs) to warming (W), clipping (CL), year (Y), and their interactions from 2000 to 2010 (Table S1, Figs. S1-S3). P values smaller than 0.05 and 0.10 are in bold and italic, respectively. Warming Clipping Year
W×CL W×Y
CL×Y
W×CL×Y
Tsoil
