2015國際森林土壤研討會-主會場mycorrhiza and soc sequestration

1、Mycorrhiza and its potential contribution to soil carbon sequestration in subtropical forests, southern ChinaTang Xuli et al.South China Botanical Garden, CAS2015-10-26 FuzhouSoudzilovskaia et al. 20154887 plant species are arbuscular fungi symbiotic plantsMost terrestrial vascular plants form mycor

2、rhizae125 plant species are ectomycorrhizal fungi symbiotic plantsTreseder and Holden, 2013The carbon compounds remain in the soil over the long term have been produced by fungi and other microbes, not by plants (see Prescott et al. 2010)Mycorrhizal fungi associated with plant roots may contribute t

3、o carbon sequestration in soilsMycorrhizal fungi is a rapid pathway for translocating fresh plant C to soil Kaiser et al. 2015Using NanoSIMS imaging and 13C-PLFA/NLFA, Kaiser et al (2015) found a major release of recent photosynthates into soil leave plant roots via AM hyphae rather than root exudat

4、ions.Mycorrhizal fungi drive carbon sequestration Litter-derived CRoot-derived CTraditional viewAboveground plant litter quality and position rates determine fundamentally of long-term soil organic matter accumulation.New finding50 to 70% of stored carbon in soil derives from roots and mycorrhizal f

5、ungi.Clemmensen et al.2013. Science, 339:1615-1618Mycorrhizal fungi may increase organic carbon position Hyphae consume certain amount of carbon because of fast turnover rate (Staddon et al. 2003; Johnson et al. 2002) “Priming effect” under elevated CO2 (Cheng et al. 2012)Staddon et al. 2003, Scienc

6、e,300:1138-1140Hyphae turnover fast (5-6 days)eCO2 enhance plant N demand prompts AMF to pose OM, release nitrogen for host plantsCheng et al. 2012. Science, 337:1084-1087Short-term liability versus long-term benefitsVerbruggen et al. 2013In the short term, mycorrhizal fungi-mediated increase in pos

7、ition of liable plant litter may lead to a reduction of soil C. However, the C balance is offset by a long-term gain in recalcitrant compounds. Tang et al. 2011. Plant EcologyAllocation of the accumulated carbon was different between the young and the old-growth subtropical forests. Old-growth fores

8、tYoung forestOld-growth forestYoung forestDo mycorrhizal fungi benefit for soil carbon accumulation in subtropical forests?More than 60% of NPP in the old-growth forest was allocated to belowground, where have these carbon been?Higher APA and APA per unit of soil organic carbon in the old-growth for

9、est, suggesting severe P limitation in the old-growth forest (Huang et al. 2013).Exacerbated P limitation in the old-growth forest Huang et al. 2013. Plant Soil, 364:181-191youngold-growthAPAAPA per unit of soil organic carbonSOC stock in the top 20 cm soil layer increased between 1979 and 2003 with

10、 an average rate of 61g m-2 year-1 (Zhou et al. 2006)Zhou et al.2006, Science,314:1417g C m-2 year-1PlantSoilThe old-growth forest exhibit high carbon sequestration potential in soils.Tang et al. 2011. Plant Ecology, 212:1385-1395SOC accumulated in the old-growth forestFact 2The old-growth forest is

11、 P limited.More mycorrhizal fungi exist in the old-growth forest? Mycorrhizal fungi drive SOC accumulation in subtropical forests.Fact 1Old-growth forest allocated substantial carbon to belowgroundNPP allocated to mycorrhizal fungi was proportional to NPPb (Hobbie, 2006)The mutualism between mycorrh

12、izal fungi and plant is bidirectional controlled（Kiers et al. 2011）Fact 3The old-growth forest accumulated carbon in soilsMechanisms of mycorrhizal fungi benefit to SOC accumulationDirect way: mycorrhizal biomass, exudations .Indirect way: stabilization of soil aggregates, protect SOC （Zhu and Mille

13、r, 2003; Guo and Tian, 2013）Mycorrhizal fungi and potential contribution to soil organic carbon sequestration: Questions and HypothesesMethodyoungold-growthPFMFMEBFSubtropical forestsMycorrhizal fungiMycorrhizal fungi type and amountMycorrhizal fungi in subtropical forestsDirect wayIndirect wayFores

14、t compositionContribution of mycorrhizal fungi to SOC accumulationBiomassExudationsRespirationSoil aggregatesMicrobial diversityRecalcitrant carbonIndexMethodMycorrhizal resourceType; colonization ratio; spores densityHyphae biomassNPP, colonization ratio, PLFAExudationGRSPRespirationPartition soil

15、respiration with micro-pore meshes70% of plant roots were infected by mycorrhizal fungiNPP allocated to mycorrhizal fungiPF:198.161.3g C m-2 year-1MF:285.976.4 g C m-2 year-1MEBF:324.881.6g C m-2 year-1（Zheng et al，2013）1.Direct contribution of mycorrhizal fungi to SOC accumulationC budget ForestMyc

16、orrhizal typeNumbers of plant speciesNumbers of individuals per hectarePFECM3380AM213065MFECM6687AM412285MEBFECM10461AM574597Basal respirationHyphae respirationFine roots respirationSoil respirationPartition soil respiration with micro-pore mesh method（Moyana et al, 2007;2008;Heinemeyer et al. 2007;

17、 Nottingham et al, 2010）Treatments：1 m，35 m，2 mm，CKHyphae respiration（mol CO2 m-2 s-1）=35 m respiration1 m respirationC loss via hyphae respirationPF:118.9100.7 g C m-2 year-1MF:174.889.5g C m-2 year-1MEBF:190.6125.2g C m-2 year-1ForestC allocated to mycorrhizal fungi(g C m-2 year-1)C loss via hypha

18、e respiration(g C m-2 year-1)C loss/NPP to mycorrhizal fungi ratioPF198.161.3118.9100.7 60%MF285.976.4174.889.539%MEBF324.881.6190.6125.241%Direct contribution of mycorrhizal fungi to SOC sequestration may negligible(Zhong and Tong, unpublished data)2.Indirect contribution of mycorrhizal fungi to SO

19、C sequestrationmg cm-3Dry seasonWet seasonT-GRSP4.580.34(4.24-4.57)5.800.36(5.39-6.05)EE-GRSP0.890.12(0.84-0.97)1.480.14(0.71-1.41)GRSP concentration in the 0-10 cm soil (n=21)Subtropical forest soil has relative high GRSP stockGRSP stock（Zhang et al. Under review）SOC concentration increased linearl

20、y with T-GRSP （Zhang et al. 2015 unpublished data)youngold-growth0-10 cm10-20 cm%EE-GRSP/SOC1-2% (0-10 cm)3-5% (10-20 cm)%T-GRSP/SOC6-9% (0-10 cm)10-15% (10-20 cm)The contribution of GRSP to SOC ranged from 8 to 15 times of microbial biomass C to SOCEE-GRSPT-GRSP（Zhang et al. 2015, unpublished data)

21、T-GRSP accounted to 6-15% of SOC in subtropical forestsGRSPSOC0-10 cm10-20 cmGRSP as recalcitrant compounds may enhance the stability of SOC Blue bars: recalcitrant C fractionGreen bars: liable C fractionHigher recalcitrant index in GRSP than in SOC(Zhang et al. 2015, unpublished data)MEBFPFMF2mm, l

22、arge macro-aggregate0.053-0.25 mm, large micro-aggregateMacro-aggregatesMicro-aggregatesGRSP may facilitate the formation of macro-aggregates in subtropical forests T-GRSPyoungold-growthEnvironmental changeVegetation compositionFungal groups Soil C storage?N depositioneCO2WarmingDroughtAir temperature rise experiment in subtropical forests (2012)+3oC+1.5oC+1.5oC600 m a.s.l300 m a.s.l20 m a.s.lLiu et al. 2013Nitrogen deposition experiment (2013)2 treatments: canopy