Fine root lifespan depending on their diameter and soil depth

(1)

HAL Id: hal-02797952

https://hal.inrae.fr/hal-02797952

Submitted on 5 Jun 2020

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Fine root lifespan depending on their diameter and soil depth

Amandine Germon, Rémi Cardinael, Christian Dupraz, Jean-Paul Laclau, Christophe Jourdan

To cite this version:

Amandine Germon, Rémi Cardinael, Christian Dupraz, Jean-Paul Laclau, Christophe Jourdan. Fine root lifespan depending on their diameter and soil depth. ISRR9: International Society of Root Research, Roots Down Under, Belowground Solutions to global challenges, Oct 2015, Canberra, Aus-tralia. 2015, �10.13140/RG.2.1.3101.0967�. �hal-02797952�

(2)

Fine root lifespan

depending on their

diameter and soil depth

Materials and methods

Opening of a deep pit and

Minirhizotron set up

•  A pit 5 m (length) x 1.5 m (width) x 4 m (depth) was dug

perpendicular to the tree rows, starting close to the tree row

and ending in the middle of the inter-row (Cardinael et al. 2015)

•  16 minirhizotrons installed at 0, 100, 250 and 400 cm deep

Results

•  Surprisingly, deep fine root growth (at depths > 2.5 m) mainly occurred not only at bud break in spring but also throughout the winter, after leaf fall

•  By contrast, shallow roots grew mainly during the spring-summer period.

•  Fine roots below a depth of 4 m accounted for more than one fourth of the total root production in the

whole soil rooting profile down to a depth of 4.7 m •  Carbon and nutrient remobilizations also occur in

winter to support fine root growth in deep soil layers

(Germon et al. 2015)

•  Root mortality occurred mainly in upper soil layers and only 10% of the fine roots that appeared over the study period below 4 m died

•  Fine root lifespan was longer with increasing root diameter and soil depth.

Cardinael R, Mao Z, Prieto I, Stokes A, Dupraz C, Kim JH, Jourdan C (2015a) Competition with winter crops induces deeper rooting of walnut trees in a Mediterranean alley cropping agroforestry system. Plant and Soil 391: 219-235

Germon A, Cardinael R, Prieto I, Mao Z, Kim J, Stokes A, Dupraz C, Laclau J-P, Jourdan C Unexpected phenology and lifespan of shallow and deep fine roots of walnut trees grown in a Mediterranean agroforestry system; Plant and Soil, to be published, 2015.

Goel MK, Khanna P, Kishore J (2010) Understanding survival analysis: Kaplan-Meier estimate. International Journal of Ayurveda Research 1: 274-278.

>

CONCLUSION

> CONCLUSION

•  In Mediterranean agroforestry systems, the

competition with winter intercrops induces tree roots to explore deep soil layers

•  Organic matter was added into shallow layers through root mortality, whereas carbon injected

deeper through root growth may improve C storage during longer periods in this ecosystem.

www.cirad.fr

• Agroforestry systems are simultaneous or sequential associations of woody

perennial species and crop or animal production systems in the same area and

provide a variety of ecosystem services whilst maintaining a high agricultural

production

• Fine roots play a major role in the global carbon cycle through respiration,

exudation and decomposition processes, but their dynamics are poorly understood

• Current estimates of root dynamics have principally been observed in shallow soil

horizons (< 1m), and mainly in forest ecosystems

GERMON Amandine1,2

CARDINAEL Rémi1,3

DUPRAZ Christian1

LACLAU Jean-Paul4

JOURDAN Christophe4 1_{INRA UMR System,} 2_{AgroParisTech GEEFT,}

3_IRD4_{CIRAD UMR Eco&Sols}

Montpellier, France

christophe.jourdan@cirad.fr

Objectives of the study

Our study aims to examine the phenology, elongation

and turnover rates of walnut fine roots in an agroforestry system and to estimate the influence of root diameter

and soil depth (down to 4.7 m) on root dynamics

Study Site

•  Sub-humid Mediterranean climate •  Silty clay deep alluvial fluvisol

•  20-year-old hybrid walnuts (Juglans regia x

nigra). The current density is 96 trees ha-1

•  The associated crop is mainly durum wheat (Triticum turgidum L. subsp. durum)

Root monitoring and data processing

•  Fine root (diameter ≤ 2 mm) dynamics were recorded across three diameter classes every three weeks for one year

•  Root survivorship and lifespan were estimated using the

Kaplan-Meier and Cox Proportional Hazard methods

(Goel et al. 2010) © R. C ard in ae l 0 50 100 150 200 250 300 0-‐170 cm 250-‐470 cm Ro ot li fe sp an (d ay s) Depth D < 0.5 0.5 < D < 1.5 1.5 < D

Fine root elongation rate (RER)