WP O6 - Carbon turnover Final Meeting Aberdeen 28 May - 1 June WP 6 – Carbon Turnover at different depths

WP O6 - Carbon turnover Introduction Objectives and deliverables Presentation of last main results (WPI to WPIII) : Keeling plots Microbial biomass and activity Coupling microbiological and organic chemistry variables Peat basal respiration (CO 2 -CH 4 profiles) Microbiological indexing systems Considering the microbioligical variables as indicators Disturbance, resilience, regeneration … Microbial community functioning vs secondary succession Concluding remarks Plan

WP O6 - Carbon turnover –To determine the impact of recolonizing vegetation (Sphagnacae, vascular plants) on soluble organic forms of C and N and emissions of CO 2 and CH 4 from restored cut-over sites –To correlate rates of C turnover with structure of microbial communities (WP03) and the peat organic matter components at different depths (WP05) –To relate C turnover to management practices and procedures at different time scales Objectives

WP O6 - Carbon turnover Deliverables –D 19 – Production of isotopically labelled 13 C/ 15 N WP III : lab and field experiment –D20 - Establishment of regeneration thresholds in terms of « link- source » and assessment of the origin of C in gaseous efflux WP I : field experiment Connexion with D6, D7 (WP02), D23 (WP 07) –Keeling plots (Daniel E. presented by AJ + ) –D21 - Modelling CO 2 -CH 4 -Microbial biomass C potential ratios in different cases of peatland restoration including the influence of N-litter WP I + WP II + WP III Connexion with D16 (see Fatima report on WP5) –Effect of plant species on microbial biomass (AJ) –Modelling microbiological indicators (AJ) –CO 2 /CH 4 peat profiles (Andy)

WP O6 - Carbon turnover Results WP I & II …. 1 - Keeking plots 2 - Microbial biomass 3 - Coupling microbiological and organic chemistry variables 4 - Peat basal respiration (CO 2 -CH 4 profiles)

WP O6 - Carbon turnover D20 - Establishment of regeneration thresholds Old peat vs new peat: measurements of  13 C (Keeling Plots method) The isotopic signature of respired CO 2 ranged between and ‰ and it varied among plots and seasons Bare peat respired more 13 C enriched CO 2 than revegetated plots May 05July 05Aug 05 AdvancedRecentBare peat  13 C of respired CO 2  13 C of bulk organic matter ( ‰ ) Mosses  0.05 Vascular plants  0.44 Peat cores : advanced regeneration  0.19 recent regeneration  0.12 bare peat  0.12 This is consistent with the isotopic signatures of bulk organic matter of peat and vegetation Respired CO 2 is enriched in 13 C when compared with bulk organic matter, suggesting negative fractionation during respiration Objective : determination of the contribution of new peat and old peat to CO 2 emission

WP O6 - Carbon turnover D21 - Modelling CO 2 -CH 4 -Microbial biomass C potential ratios Effect of Living plants and Water level on microbial pools No significant effect of plant and water level on soluble C-N-C/N Kruskal-Wallis test Effect PLANT P value WATER LEVEL P value N - MB Yes No C/N No No C - MB Yes No FI SC FB FR Only a significant effect of plant on C and N microbial biomasss

WP O6 - Carbon turnover Kruskal-Wallis test Effect LITTER P value WATER LEVEL P value Increasing N microbial biomass under Eriophorum litter (EA : 85  1 ppm ; EV : 63  10) and no difference between bare peat and Sphagnum (BP : 46  9 ppm and S : 42  9) N - MB Yes No C/N Yes < No No effect on C microbial biomass Microbial C/N lower with Eriophorum litter (EA : 4.5  1.0 and EV : 7.1  1.1) vs higher values in bare peat and Sphagnum treatment (BP : 8.6  0.9 and S : 9.4  0.9) C - MB No No D21 - Modelling CO 2 -CH 4 -Microbial biomass C potential ratios Effect of Litter plants and Water level on microbial pools

WP O6 - Carbon turnover Coupling microbial variables –organic chemistry multivariate analyses using constrained ordination methods (Co-inertia) Biological Variables in the Co- inertia plan 1 (All sites) Chemical Variables in the Co-inertia Plan 2 (All sites) organic chemical variables (explicative) Axis 1  Total Organic C, Preserved Tissues, Hemicellulose and Galactose Axis 2  Total Organic N, Amorphous Organic matter and Decayed Tissues biological variables (to be explained) Axis 1  C and N microbial biomasses and Anaerobic Activity Axis 2  Aerobic activity and C microbial turnover The main contributions in the co-inertia analysis were :

WP O6 - Carbon turnover Results WP I & II …. 4 - Peat basal respiration (CO 2 -CH 4 profiles) Andy

WP O6 - Carbon turnover Microbiological indexing systems for assessing regeneration of peat accumulation process 1 - Considering the microbioligical variables as indicators 2 - Disturbance, resilience, regeneration … 3 - Microbial community functioning vs secondary succession

WP O6 - Carbon turnover Microbiological indexing systems to assess peatland regeneration trends C mineralization rate = microbial quotient = in relation with organic matter quality = allows to compare rates of activity in peat with different organic C status - sensitive to land management i.e.  increase with peat extraction  no early change after restoration management Microbial variables Characteristics (Relationship to peat function, causes of variations Responses (processes in the upper part of peat profile (0- 50 cm max) Microbial Biomass C, N, C/N = labile pool vs sink = driving force to nutrient transformation = aggregative agent - Sensitive to restoration management i.e. increasing of C-N microbial stocks - sensitive to peat extraction (declining with aeration, erosion and subsidence) Basal Respiration anaerobic & anaerobic = activity of the microbial pool and capacity of mineralisation = flux of C (source) - change with peat age and regeneration stages (low in early secondary succesion) - high in natural peatland vs low in cutover peatland Microbial turnover rate = Microbial metabolic Qqtient Changes in MTR (=MMQ)  = change in substrates or = change in microbial community or = change in substrate and community or = change in the physiological status of communities due to altered requirement - no difference between disturbed situation and natural - less sensitive to regenertation gradient

WP O6 - Carbon turnover Relation between peat functional integrity, disturbance and resilience (After Herrick et Wander 1998, modified & applied to peat) C Function (ex : C sink) Time B New steady state Disturbance A Steady state Loss of C Regeneration process Gain of C Modelling the C-N microbial biomass vs age of regeneration (WP I results) D Modelling CO 2 -CH 4 -MB potential ratios : Towards other Deliverables in the research of ecological indicators of peat regeneration …. Disturbance, resilience, regeneration ….

WP O6 - Carbon turnover C/N sol Aerial biomass (g DM m -2 ) Regeneration index and CO 2 emission in North France peatlands Index 0,0 0,5 1,0 1,5 2,0 0,20,40,60,8 1,0 CO 2 efflux (g m -2 h -1 ) D Modelling CO 2 -CH 4 -MB potential ratios : T owards other Deliverables in the research of ecological indicators of peat regeneration …. Pastured peatlands (Somme floodplain) Fertilized peatlands (East Massif central) Natural Sphagnum mires (East Massif central) Drained peatlands + NPKCa (South Massif central) Index = 0,19 (CO 2 ) -2,42 (R 2 = 0,92) Biomass = (C/N) -1,18 ; R 2 = 0,52 Relation aerial vegetal biomass vs C/N soil ratio in French peatlands Disturbance, resilience, regeneration …. - left graph  different stages (-  -) of recovering process by refering (Ref) to a known «natural ecosystem» ; Ref …. or looking for thresholds : Increasing « source » function Decreasing « source » function - right graph  step by step way to define the « O » level beyond we recover the function (+ values of index) or not (- values) ( ex : C sink-source function in peatlands)

WP O6 - Carbon turnover Microbial community functioning vs secondary succession High dominance of one species in the plant communities  low N microbial biomass Higher diversity of plant communities  high N microbial biomass Earlier stages of secondary succession on bare peat  1-10 years after abandonment of extraction Older stages of secondary succession on bare peat  years after abandonment of extraction D Modelling CO 2 -CH 4 -MB potential ratios : Towards other Deliverables in the research of ecological indicators of peat regeneration ….

WP O6 - Carbon turnover Signicant but R 2 too low (0.1) … A little bit better ? Relating organic chemistry and microbiological variables, not so simple : 2) A new horizon : applying the Clymo ’s model to acrotelm regeneration C sequestration and new acrotelmic peat forming Considering p a = input of dry matter in the peat,  a the decomposition rate : dx/dt = p a -  a x with the following solution : x p a /  a (1 - e -  a t ) = accumulated peat D Modelling CO 2 -CH 4 -MB C potential ratios …. Towards other Deliverables in the research of ecological indicatorsof peat regeneration

WP O6 - Carbon turnover Concluding remarks (1) Microbiological variables and ratios : –Microbial biomass C or N : signifcant responses with plant community and regeneration age ; –Ratios such as Carbon Turnover also show along the gradient of regeneration stages –CH 4 /CO 2 ratios (potential activity) : not enough sensitive as a regeneration index in our experiment (2) Modelling kinetics –CO 2 kinetics in laboratory (potential activity) : classical fitness to a simple model (one compartment in most of kineticss, sometimes two) (3) Need to be completed : –Use of Clymo’s model of accumulation with results of production and decomposition in Le Russey (WP III) –Further investigation in coupling organic chemistry and blobal microbial variables (will be done in July) –Relationships between kinetics of CO 2 -CH 4 in lab with structure of microbial communities

WP O6 - Carbon turnover Additionnal slides …. 1 - Results on litter (WP III -Ecobio) Theoterical considerations

WP O6 - Carbon turnover 13 C - 15 N Litter – Lab exp. WP III Litter decomposition : - kinetics of dry matter, C/N Microbial biomass in the peat columns : - calculation of 15N and 13 C recovery in progress - labeled 15N found in unfumigated and fumigated extract, in N mineral extract too - 13 C- 15 N deltas

WP O6 - Carbon turnover Diagrammatic representation + - Peat decomposition/accumulation process : source vs sink function 0 Geology Hydrology Climat Biology … Aeration Temperature Nutrients … Attainable Drainage Extraction Erosion … Potential Defining factors Limiting factors Carbon sequestration level Actual Restoration measures Reducing factors

WP O6 - Carbon turnover Evolution of the concept of resilience over the laste 2 decades (from Gunarson 2000 in Groffman et al. 2006) t t + 1 AB Engineering resilience : Recovery time Ecological resilience : Amount of disturbance to change scale 1) How quickly a system recovers from disturbance 2) What amount of disturbance necessary to change the ecosystem state

WP O6 - Carbon turnover Criteria for ecological indicators (after Dale & Beyeler (2001) are easily measured are sensitive to stress on system respond to stress in a predictable manner are anticipatory : signify an impending change in the ecological system predict changes that can be averted by management actions are integrative : the full suite of indicators provides a measure of coverage of the key gradients across the ecological systems (e.g. soils, vegetatyion types, temperature, etc.) have a known response to natural disturbances, anthropogenic stresses, and change over time have low variability in response

WP O6 - Carbon turnover Diagrammatic representation of an impact quantified from an environmental indicator x. Quantification of an impact (André et al. 2000, modified) Indicator Time Without management With management Implantation IMPACT