production efficiency for a grassland and a forest with similar - - PowerPoint PPT Presentation

Heid L., Darsonville O., Conil S., Klumpp K., Longdoz B. ICOS Belgium Science Conference, 20 octobre 2017

Comparison of aboveground biomass production efficiency for a grassland and a forest with similar edaphic and climatic conditions

With help of: Naiken A., Gross P., Granier B

CONTEXT & OBJECTIVES

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• Evolution in ecosystem management
• Intensification, soil changes (structure, fertility,…)
• Climate change (Temperature, Pluviometry)
• Drift & extreme events (drought, heat wave, flood,…)
• Need of better understanding of ecosystem C balance
• Strategies in C allocation, sequestration & emission

(Trumbore, 2006)

• Uncertainties around the spatio-temporal variability of

theses strategies (Campioli et al., 2013)

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cultures 30% espaces hétérogènes 13% prairies 16% forêt 26% milieux semi- naturels, zones humides et aquatiques 10% bâti 5%

+0.5% /an

• 0.7%/an
• 0.7%/an

+0.1%/an +0.5%/an

Building 5% Crops 30% Forests 26% Grasslands 16% Mixed 13% Humid zones 10%

GPP Rautoaerial Rautosoil

NEE= GPP + Reco

GPP = Rauto + BP + exudates

+ COV

BPE = BP/GPP

Vicca et al., 2012

aBPE (leaves, wood) bBPE (roots)

Compounds of Interest Forest : aerial Structural C Grassland: Digestible C

CIPE= CIBP/GPP

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CIP + (réserves, SS ,…)

Rhetsoil

Biomass Production Efficiency Compound of Interest Production Efficiency

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• Only annual BPE/aBPE
• Large variability in annual BPE/aBPE
• Ecosystem type, Nutriments availability, Mean

annual temperature, Specie, Age, Management, [CO2] ⇛ Seasonal variability of aBPE ? Which drivers ? ⇛ Comparing aBPE evolutions of Forest vs Grassland Same meteo and soil

MATERIAL ET METHOD

29/06/2016 6

29/06/2016 7

Sites

Grassland Forest

• Beech (88%) stand ~55 ans
• Soil type: calcisol (7.1 <pH<8)
• Stem density: 800 stems/ha
• Height: 20-25m
• LAI = 8
• Type of soil: calcisol (7.1 <pH<8)
• Vegetation: Bromus hordaceus (53.8%), Bellis

perennis (16.8%)

Dates Event 30/03/2014 Fertilization (NPK) 13/04/2014 Grazing (Part 1) 05/06/2014 Mowing (Part 2) 12/07/2014 Grazing (Part 1 +2)

29/06/2016 8

CO2 Flux and weather measurements

• « Traditional » equipment with LI-7200 enclosed
• Data processing : Frequency correction (Fratini); Flux quality

selection (Mauder, u*threshold), Gapfilling & Partitioning (Reinschtein)

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Biomass measurements

80 cm 80 cm

= 0.64 m²

x 10 dispatched randomly on the 5.1ha

Dates Sampling 23/02/2014 Cleaning 1 16/04/2014 Growth 1 (Cleaning 2) 23/05/2014 Growth 2 (Cleaning 3) 05/06/2014 Cleaning 4 24/07/2014 Growth 3 (Cleaning 5) 11/09/2014 Growth 4 (Cleaning 6) 06/11/2014 Growth 5

Cages excluding grazing Dendrometers Litter traps Allometric equations fitted on the site (diameter, age, height) Lab analyses of cleaning biomass for C content Lab analyses of wood micro-cores for wood density and C content Lab analyses

• f collected

litter for C content Lab Biochemical analyses for (non-) structural C

RESULTS

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GPP Rautoaerial Rautosoil

NEE= GPP + Reco

GPP = Rauto + BP + exudates

+ COV

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CIP + (réserves, SS ,…)

Rhetsoil

• 549gC m-2
• 1639 gC m-2

1089 gC m-2

aBP aBPE

652 gC m-2 0.39

GPP

• 484 gC m-2
• 1538 gC m-2

1054 gC m-2

aBP aBPE

400 gC m-2 0.25

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• 549gC m-2
• 1639 gC m-2

1089 gC m-2

652 gC m-2 0.39

NEE= GPP + Reco

Reco

GPP = Rauto + BP + exudates

+ COV

• 1. Forest : more assimilated C dedicated to

aboveground biomass

• 2. Grassland : Belowground or Rauto ? (soil

ingrowth cores)

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Intra-annual variability (Forest)

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

10.04-05.05 06.05-02.06 03.06-30.06 01.07-28.07 29.07-25.08 26.08-22.09 22.09-23.11

Aboveground wBP (gC.m-2.d-1)

aBP aBP - d fixed

• 1. Density correction up to 22%
• 2. Can’t be neglected for studies on C allocation

seasonal variability

50 100 150 200 250 300 350 400

C content (gC/m²)

GPP aBP bois aBP feuille

Avril- Mai Juin Juillet Août Septembre Octobre

1 0.31 0.46 0.55 0.32 0.07

0.00 0.20 0.40 0.60 0.80 1.00 1.20

1 2 3 4 5 6

aBPE

• 1. Large intra-annual variability
• 2. No apparent influence of meteo or soil

conditions

• 3. Seasonal bell-shaped phenology similar to the

photoperiod

Intra-annual variability (Forest)

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Management: Fertilization Grazing Mowing

Intra-annual variability (Grassland)

0.00 0.10 0.20 0.30 0.40 0.50 0.60 22/02-16/04 17/04-23/05 05/06-24/07 25/07-11/09 12/09-06/11

aBPE

• 1. Larger variability ⇔ forest
• 2. Impact of mowing ?

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0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Production efficiency NSC C_Cel+L C_Hem

April Mai June July August Sept October- November

TAKE HOME MESSAGE

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• Forest allocated larger % of GPP to

aboveground

• Large aBPE seasonal variability (larger on

grassland)

• Forest : continuous curve ⇔ Grassland :

impact of mowing

• Temporal evolution of the reserve/wood

formation strategy

Thank