How root traits are modified in secondary succession gradient along roadsides ?

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https://hal.archives-ouvertes.fr/hal-01268807

Submitted on 5 Jun 2020

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How root traits are modified in secondary succession gradient along roadsides ?

Amandine Erktan, Alexia Stokes, Catherine Roumet, Diane Bouchet, Yogan Monnier, Francois Pailler, François Munoz

To cite this version:

Amandine Erktan, Alexia Stokes, Catherine Roumet, Diane Bouchet, Yogan Monnier, et al.. How root traits are modified in secondary succession gradient along roadsides ?. BES and SFE Joint Annual Meeting, Dec 2014, Lille, France. �hal-01268807�

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0 10 20 30 40 50 60 0-10 11-20 21-30 31-40 >40 0 0,5 1 1,5 2 2,5 3 3,5 0-10 11-20 21-30 31-40 >40

0 – 10 years old

11 – 20 years old

21 – 30 years old

31 – 40 years old

> 40 years old

How root traits are modified in secondary succession

gradient along roadsides ?

1_{UMR AMAP ; TA A-51/PS1, Boulevard de la Lironde ; 34398 Montpellier Cedex 5 -}2_{CNRS, CEFE-UMR 5175; 1919, route de Mende ; 34293 Montpellier 5}

Erktan, A.

1 _{, Stokes, A.}

1 _{, Roumet, C.}

2 _{, Bouchet, D.}

1 _{, Monnier, Y.}

1 _{, Pailler, F.}

1 _{, Munoz, F.}

1 Background and aims

Material and methods

Results and discussion

Conclusion

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 Plant communities developing on linear embankments provide several ecosystem services, such as slope stabilization or refuge for biodiversity. Plant characteristics (traits) determine the way vegetation provides these services.

Understanding how these traits vary within and between plant communities in various land use contexts is then relevant for ecosystem and landscape management.

 After a first phase of hydroseeding or plantation, dynamics of plant communities on road-sides can be considered as a secondary succession. Plant traits change during succession, due to species replacement and intraspecific

adaptations, leading to potential variations in related ecosystems services. Variations of root traits undergoing succession can strongly impact soil stabilization and are poorly known, especially at the plant community level.

 For safety reasons, road-sides are periodically mown, about one to twice a year. Mowing may change root traits by modifying resources allocation. But little is known about the belowground effect of mowing.

Aim : How root traits are modified in periodically mown roadside plant communities undergoing secondary succession?

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 Significant variations in root traits occur along secondary succession gradients, with chemical traits having the lowest variations and morphological traits the highest.

 Early successional communities have relatively small quantities of fine and low dense roots. Conversely, late successionnal communities have large quantities of coarse and high density roots, suggesting an important replacement of

fast growing acquisitive species by slow growing conservative species along the secondary succession gradient.

 Mowing reduces roots diameter and biomass but its general effect on root traits is not significant, suggesting a relative indenpendance between below and aboveground compartments in plant communities.

 Association of more conservative species with more fertile soils is not common and may be linked to the fact that roadside are mainly mineral anthroposoils after roadworks. Plant development add organic carbon into these systems.

0 0,5 1 1,5 0-10 11-20 21-30 31-40 >40 0 10 20 30 40 50 0-10 11-20 21-30 31-40 >40 0 0,1 0,2 0,3 0,4 0,5 0-10 11-20 21-30 31-40 >40 R oot N (%) R oot C (%) RD MC ( mg. g -1 ) 0 100 200 300 400 500 0-10 11-20 21-30 31-40 >40 Mean r oot diam et er (mm)

• How root traits are modified with age and mowing at the community level ?

• How soil parameters changes with modifications in root traits in secondary succession gradient ?

• Do age and mowing influence root trait variations ?

mown not mown

F=2.5/n.s F=2.6/n.s F=11.6/** F=3.9/* F=11.2/** F=2.2/n.s F=6.0/** F=4.6/** ab _a _a ab b a a a _a b a a a ab b a _a ab ab b a a ab ab b 30 - 45° 16 m

Soil composite sample for root analyses

Soil composite sample for soil analyses

Root traits

Soil characteristics

• Root nitrogen (Root N)

• Root carbon (Root C)

• Root dry matter content (RDMC)

• Specific root lenght (SRL)

• Mean root diameter

• Root mass density (RMD)

• Root length density (RLD)

• Soil carbon (Soil C)

• Soil nitrogen (Soil N)

• Soil texture

• Carbonates (CaCO

₃

)

• pH (H

₂

0)

• Available phosphorus (Soil P)

• Cationic Exchange Capacity (CEC)

Sampling zone

years-old years-old years-old years-old years-old F=3.6/* F=3.3/* RM D (kg .m -3 ) RLD (km.m -3 ) F=1.0/n.s F=1.0/n.s years-old a ab ab ab b a ab ab ab b mown not mown 0-10 11-20 21-30 31-40 >40

Road side plant communities

Age (years old)

Sour ce s : D . B ouche t

 Along the succession gradient, organic matter accumulate in soils. The availability of soil nutrients remains low accross the succession gradient (Soil P, CEC)

 Early successional communities have greater quantities of fine roots, with high nitrogen content, growing in poor organic soils

 Late successional communities have large masses of coarse roots, with high carbon concentration, growing in organic-rich soils

Principal component analysis (PCA) n=48

Many thanks to Bruno Buatois, Nicolas Barthès and Raphaëlle Leclerc for their help in labwork

0 20 40 60 80 100 120 0-10 11-20 21-30 31-40 >40 SR L (m. g -1 ) F=20.2/*** F=4.4/* a a ab b b a _a ab ab b years-old

Redundancy analysis (RDA) n=48

 Root N tend to decrease with age

 Increase in root C with age  Low effect of mowing on

chemical root traits variations

 Strong increase in root diameter with age

 Mowing reduces root diameter

 Age significantly influences root trait variations at the community level  Root traits are not modified by mowing (alone or in interaction with age)

 Root dry matter content increases with age in mown communities

 No significant variations of RDMC in non mown communities

Instrumental variables Model

Age Mowing Age x Mowing

Effect on root traits (F/P) 5.8/** 0.56/n.s 0.56/n.s 2.9/**

 Strong increase in root mass density with age

 Mowing reduces root mass density

 Not signficant variations of RLD, a trait often linked to soil stability

Secondary succession

Axis 1 : 37 % A xis 2 : 1 5 % Root N Root C RDMC SRL

Mean root diameter RMD RLD Clay Silt Sand Soil C Soil N C:N CEC Soil P CaCO₃ pH(H₂0)