Increased soil organic carbon stocks under ...

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4 AgroCampus Ouest Centre d'Angers, UPSP EPHor, 49045 Angers, France (present address). 5 Agroof, 30140 Anduze, France. 6 INRA, UMR System, 34060 ...

Increased  soil  organic  carbon  stocks  under  agroforestry:  A  survey  of  six  different   sites  in  France   CARDINAEL  R.1,2,3*,  CHEVALLIER  T.1  ,  CAMBOU  A.1,4,  BÉRAL  C.5,  BARTHÈS  B.G.1,  DUPRAZ  C.6,  DURAND  C.1,  KOUAKOUA  E.1,  CHENU  C.2   1  IRD,  UMR  Eco&Sols,  34060  Montpellier,  France  

4  AgroCampus  Ouest  Centre  d’Angers,  UPSP  EPHor,  49045  Angers,  France  (present  address)  

3  CIRAD,  UPR  Aida,  34398  Montpellier,  France  (present  address)    

6  INRA,  UMR  System,  34060  Montpellier,  France  

2  AgroParisTech,  UMR  Ecosys,  78850  Thiverval-­‐Grignon,  France  

*[email protected]    

5  Agroof,  30140  Anduze,  France  

Study  sites  

IntroducFon   •  Agroforestry   systems   (AFS)   associate   crops   and   trees   in   the  same  field   •  Trees  store  carbon  into  their  biomass  but  also  produce  an   important   amount   of   fresh   organic   ma_er   that   could   enhance  soil  organic  carbon  (SOC)  stocks   •  Studies concerning temperate AFS are scarce and little is known concerning their impact on deep SOC stocks

•  5  silvoarable  systems   •  1  silvopastoral  system   •  Adjacent  agricultural  plots   Site  

Soil  

Tree  density   Age   (trees/ha)   (years)   CH   Luvisol   34   6  

ME   Luvisol  

35  

6  

ObjecFves  of  the  study  

SJ   Luvisol  

102  

41  

! Measure  SOC  stocks  in  AFS  compared  to  agricultural  plots  

VE   Fluvisol  

100  

18  

RE   Fluvisol  

110  

18  

TH   Andosol  

200  

26  

! QuanQfy  tree  aboveground  C  stocks  

Table  1.  Main  site  characteris%cs.  

! EsQmate  SOC  accumulaQon  rates  in  AFS  

Fig.  1.  Loca%on  and  descrip%on  of  the  6  agroforestry  systems  sampled  in  France.  

Materials  and  methods  

Results  

•  Paired-­‐sites   (agroforestry   vs   agricultural   control   plots)  

•  SOC   concentraQons   and   stocks   higher   in   the   tree   rows   than   in   the   inter-­‐rows   and   in  the  controls  (Fig.  3)  

•  Three  sampling  pa_erns  per  agroforestry  site  (Fig.  2),       ̴12  sampling  point  per  control  plot  

•  Total   SOC   stocks   higher   in   agroforestry   than  in  the  control  (Fig.  4)  

•  Soil  cylinders  sampled  every  10  cm  depth.  Maximum   sampling   depth   site-­‐related.   Measurement   of   bulk   density  and  SOC  concentraQons  

•  In  the  silvoarable  systems,  the  mean  SOC   stock   accumulaQon   rate   was   0.24   (0.09– 0.46)   Mg   C   ha-­‐1   yr-­‐1   at   a   depth   of   30   cm   (Fig.  5).    

•  SOC   stocks   calculated   on   an   equivalent   soil   mass   basis   •  Measurement  of  tree  aboveground  biomass  

Fig.  2.  Sampling  pa:ern.  

•  C   accumulaQon   rate   was   0.65   (0.004– 1.85)  Mg  C  ha-­‐1  yr-­‐1  in  the  tree  biomass.  

Results  

Fig.  4.  Total  organic  carbon  stock  (Mg  C  ha-­‐1)  of  the  different  sites.  ABG:  aboveground;  BLG:   belowground.  

Fig.  3.  Soil  organic  carbon  concentra%on  (mg  C  g-­‐1)  at  the  different  sites.  

Conclusion   Agroforestry systems efficiently enhance SOC stocks in agricultural lands and contribute to climate change mitigation. These systems are also food-producing systems (compared to afforestation), and are therefore of high interest for the « 4 per 1000 Initiative »

References   Cardinael  R.,  Chevallier  T.,  Barthès  B.G.,  Saby  N.P.A.,  Parent  T.,  Dupraz  C.,  Bernoux  M.,  Chenu  C.,  2015.  Impact  of  alley  cropping  agroforestry  on   stocks,  forms  and  spaQal  distribuQon  of  soil  organic  carbon  -­‐  A  case  study  in  a  Mediterranean  context.  Geoderma  259–260,  288–299.   Cardinael  R.,  Chevallier  T.,  Cambou  A.,  Béral  C.,  Barthès  B.G.,  Dupraz  C.,  Durand  C.,  Kouakoua  E.,  Chenu  C.,  2017.  Increased  soil  organic  carbon   stocks  under  agroforestry:  A  survey  of  six  different  sites  in  France.  Agric.  Ecosyst.  Environ.  236,  243–255.  

Fig.  5.  SOC  stock  accumula%on  rates  as  a  func%on  of  planta%on  age.   Values   are   for   the   approximate   top   30   cm,   except   for   the   SJ   site   (approximate  top  20  cm,  maximum  soil  depth).  

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