Does N limit C sequestration in terrestrial ecosystems? If so, how? Yiqi Luo Department of Botany...

download Does N limit C sequestration in terrestrial ecosystems? If so, how? Yiqi Luo Department of Botany and Microbiology University of Oklahoma USA

of 36

  • date post

    15-Dec-2015
  • Category

    Documents

  • view

    215
  • download

    3

Embed Size (px)

Transcript of Does N limit C sequestration in terrestrial ecosystems? If so, how? Yiqi Luo Department of Botany...

  • Slide 1
  • Does N limit C sequestration in terrestrial ecosystems? If so, how? Yiqi Luo Department of Botany and Microbiology University of Oklahoma USA
  • Slide 2
  • Key points 1. 1.Mineral N regulates plant growth and its responses to global change 2. 2.N capital in organic form determines long-term carbon sequestration
  • Slide 3
  • Working hypotheses 1.CO 2 stimulation of carbon sequestration will be down-regulated by limited N supply over time. 2.Climate warming stimulates N mineralization and increases N availability, which will enhance C sequestration 3.N deposition increases mineral N availability, stimulate plant growth, and thus will enhance C sequestration
  • Slide 4
  • Carbon cycle Soil Mineral N Nitrogen cycle Plant assimilation Warming N deposition Elevated CO 2
  • Slide 5
  • Effects of nitrogen on plant growth, overall and grouped by biome LeBauer and Treseder 2008
  • Slide 6
  • Slide 7
  • Plant Carbon cycle Soil Mineral N Nitrogen cycle assimilation Atm CO 2 Litter / CWD Soil Organic Matter N deposition N fixation denitrification N leaching respiration Internal fast External slow mineralization photosynthesis litterfall & mortality decomposition (i) Thornton et al. 2009
  • Slide 8
  • Effects of N addition on C and N cycles Meta-analysis of data from 206 papers Lu et al. 2011 New Phytologist (N cycle) Lu et al. 2011 Agricultural Ecosystems & Environment (C cycle)
  • Slide 9
  • Leaching 461% N 2 O 134%Den 84% N addition NH 4 + 47% N uptake NO 3 - 429% Aboveground plant N 44% Belowground plant N 53% N-Min 25% Litter/OH decomposition Litter N 24% Organic Horizon N 6.1% Soil N pool 6.2% Microbial biomass N 5.8% DON 21% Nit. 154% Extremely leaking system Lu et al. 2011a
  • Slide 10
  • OSullivan et al. 2011 GCB Once N fertilization stops, mineral N gradually reset to the control level
  • Slide 11
  • N additions Aboveground plant C 35.7% Ps Belowground plant C 23% Litter/OH decomposition Litter C 20.9% Organic Horizon C 1.8% Deep layer SOM DOC 11% R:S 14.5 Rs 4.3% Soil organic C 2.2% Microbe C 6.4% 1.Reduce C input into soil systems 2.Little contributions of aboveground biomass and litter production to soil C 3.Increased C loss via decomposition and respiration 4.Increased C loss via DOC Lu et al. 2011b
  • Slide 12
  • Mack et al. 2004 Nature
  • Slide 13
  • Mineral N does not set the level of soil N capital over time
  • Slide 14
  • dummy heater Infrared heater clip unclip clip Long-term (12 years) warming and clipping
  • Slide 15
  • C and N interactions under experimental warming Plant community C 4 /C 3 species Leaf Ps Phenology Growing season Plant growth Microbial community Fungi/bacteria Plant N uptake Plant & soil C Available N Quality of bulk litter Respiration NUE Litter Decomposition Luo, 2007. Ann. Rev. Ecol. Evol. System
  • Slide 16
  • Plant community C 4 /C 3 species Leaf Ps Phenology Growing season Plant growth Microbial community Fungi/bacteria Plant N uptake Plant & soil C Available N Quality of bulk litter Respiration NUE Litter Decomposition Sherry et al. 2007, PNAS Zhou et al. 2007a, JIPB Zhou et al. 2006, GBC; 2007b, GCB Luo et al. 2001, Nature Zhang et al. 2005 GCB Zhou et al. In review An et al. 2005, GCB Cheng et al. 2010 Agric Ecosystems Wan et al. 2005, GBC Luo et al. 2009, GCB-E Sherry et al. 2008, GCB Niu et al. 2010, Ecology
  • Slide 17
  • Niu et al. 2010 Ecology NUE is the main mechanism underlying warming- induced increases in plant C storage
  • Slide 18
  • Lu et al. In preparation
  • Slide 19
  • Warming effects on carbon processes Lu et al. In preparation
  • Slide 20
  • NPP N sequestered in biomass & litter C input to soil N sequestered in SOM labile soil N N uptake N availability C:N CO 2 P rogressive N itrogen L imitation Luo et al. 2004 BioScineces
  • Slide 21
  • NPP N sequestered in biomass & litter C input to soil N sequestered in SOM labile soil N N uptake N availability C:N CO 2 Luo et al. 2004 BioScineces PNL may not occur if N fixation N loss
  • Slide 22
  • Luo et al. 2006 Ecology 21% increase in litter C 25% increase in litter N 5.6% increase in soil C 11.2% increase in soil N Ecosystem C increases by ~100 g m -2 yr -1 Ecosystem N increases by ~1 g m -2 yr -1 No complete down-regulation
  • Slide 23
  • Working hypotheses N capital increased by ~1 g N m -1 yr -1 to alleviate N limitation Increased N mineralization enhances biomass growth but not soil C sequestration. Yes for plant pools, not for soil pools CO 2 stimulation of carbon sequestration will be down- regulated by limited N supply over time. Climate warming stimulates N mineralization and increases N availability, which will enhance C sequestration N deposition increases mineral N availability, stimulate plant growth, and thus will enhance C sequestration
  • Slide 24
  • Soil mineral N availability regulates plant growth but does not determine long-term C sequestration Which N processes determine long- term C sequestration?
  • Slide 25
  • Rastteter et al. 1997
  • Slide 26
  • N capital in organic form Long-term C sequestration Redistribution of N among pools intermediate C sequestration Adjustment in C/N ratio short- term C sequestration Rastteter et al. 1997
  • Slide 27
  • Binkley et al. 2000 Ecosystems N capital
  • Slide 28
  • Adding inorganic N Lu et al. 2011, New Phytologist Fire Wan et al. 2001, Ecological Appl Plant invasionLiao et al. 2008, New Phytologist Forest successionYang et al. 2011, New Phytologist Forest plantationLiao et al. 2010, PloS One Elevated CO 2 Luo et al. 2006, Ecology Experimental warmingLu et al. In preparation Net change in organic N capital (the key variable to determine long-term C sequestration)
  • Slide 29
  • A database of 124 published papers from the literature Carbon and nitrogen coupling during forest succession Yang et al. 2011 New Phytologists
  • Slide 30
  • The rates of C pool changes declined with forest age and approached an equilibrium state
  • Slide 31
  • Yang et al. 2011 New Phytologists The rate of relative N change was positively associated with the rate of relative C change with different slopes among various ecosystem components
  • Slide 32
  • Yang et al. 2011 New Phytologists The rate of absolute N change increased linearly with that of C pool change
  • Slide 33
  • Yang et al. Unpublished
  • Slide 34
  • Yang et al. 2011 New Phytologists The relative change in C: N ratio was larger than 1.0 in both aboveground plant and woody tissues, but close to 1.0 in other ecosystem components
  • Slide 35
  • Conclusions 1. 1.Mineral N limits plant growth but does not regulate long-term carbon sequestration 2. 2.Organic N capital determines long-term carbon sequestration
  • Slide 36
  • http://ecolab.ou.edu Acknowledgement Financial support: U.S. National Science Foundation US Department of Energy NCEAS Working group: William Currie, Jeffrey Dukes, Christopher Field,,Adrien Finzi, Ueli Hartwig, Bruce Hungate, Yiqi Luo, Ross McMurtrie, Ram Oren, William Parton, Diane Pataki, Rebecca Shaw, Bo Su, Donald Zak Meta analysis collaborators: Dafeng Hui, Chengzhang Liao, Meng Lu, Shuli Niu, Shiqiang Wan, Yuanhe Yang, Deqiang Zhang, Xuhui Zhou