Biodiversity in riverbank techniques for erosion control: assessment of animal and plant species diversity along a naturality gradient

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1 Biodiversity in rivernk techniques for erosion control: ssessment of niml nd plnt species diversity long nturlity grdient P. Cvillé, N. Dumergue, S. De Dnielli, A. Evette To cite this version: P. Cvillé, N. Dumergue, S. De Dnielli, A. Evette. Biodiversity in rivernk techniques for erosion control: ssessment of niml nd plnt species diversity long nturlity grdient. 7th SER Europen Conference on Restortion Ecology, Ecologicl Restortion nd Sustinle Development, Aug 21, Avignon, Frnce. 4 p., 21. <hl-52573> HAL Id: hl Sumitted on 12 Oct 21 HAL is multi-disciplinry open ccess rchive for the deposit nd dissemintion of scientific reserch documents, whether they re pulished or not. The documents my come from teching nd reserch institutions in Frnce or rod, or from pulic or privte reserch centers. L rchive ouverte pluridisciplinire HAL, est destinée u dépôt et à l diffusion de documents scientifiques de niveu recherche, puliés ou non, émnnt des étlissements d enseignement et de recherche frnçis ou étrngers, des lortoires pulics ou privés.

2 CAVAILLE, P., DE DANIELLI, S., DAUMERGUE, N., EVETTE, A Biodiversity in rivernk techniques for erosion control: ssessment of niml nd plnt species diversity long nturlity grdient. 7th SER Europen Conference on Restortion Ecology, Ecologicl Restortion nd Sustinle Development, 23-27/8/21, Avignon, FRA. 4 p. Biodiversity in rivernk techniques for erosion control: ssessment of niml nd plnt species diversity long nturl grdient. Pul Cvillé 1*, Nthn Dumergue 1, Séstien De Dnieli 1 nd André Evette 1. 1 Cemgref, UR EMGR, 2 rue de l ppeterie BP 76, 3842 Sint-Mrtin-d Hères, Frnce * Corresponding uthor: pul.cville@cemgref.fr Keywords: eetles, iodiversity, ecologicl restortion, plnt diversity, rivernk, soil ioengineering, Extended strct: Rivernks re chrcterised y high levels of oth species-richness nd nthropic pressure (Decmps 23; Schnitzler-Lenole 27). Erosion controls on rivernks often involve instlltions to protect humn investments (i.e. uildings, pulic menities etc.). However, whether such instlltions cn ccommodte nturl iodiversity hs not een well ssessed nd is consequently seldom tken into ccount in the choice of technique. Furthermore, specific work must e done on exotic species nd their negtive effect on iodiversity in such environment. Indeed, the development of invsive species is of considerle importnce s it represents the fourth thret in terms of iodiversity loss (Thuiller 27). Riprin ecosystems re prticulrly impcted y this invsion phenomenon since they re considered s eing rich nd strongly pertured re (PlntyTcchi, Tcchi et l. 1996; Vitousek, Dntonio et l. 1997; Alpert, Bone et l. 2). This study ims to ssess niml nd plnt txonomic diversity on nturlness grdient of vrious rivernk protection systems. This is done y compring iodiversity of rivernk construction from entirely stone riprp, through comined constructions (mixing riprp nd ioengineering), to purely vegettive ioengineering structures. We lso seek to highlight ioengineering effects on exotic species development. Three types of rivernk protections were chosen: - Entirely minerl protections: mde up of rough riprp. - Mixed protections: composed of rough riprp for the lower prt of the rivernk nd plnt seedings nd cuttings on the upper prt. - Vegettive ioengineering protections: mde up of willow fscines, rush lyers, cuttings nd seeding. These three types of rivernk protections re respectively clled Minerl, Mixed nd Vegetl (fiugure1).

3 CAVAILLE, P., DE DANIELLI, S., DAUMERGUE, N., EVETTE, A Biodiversity in rivernk techniques for erosion control: ssessment of niml nd plnt species diversity long nturlity grdient. 7th SER Europen Conference on Restortion Ecology, Ecologicl Restortion nd Sustinle Development, 23-27/8/21, Avignon, FRA. 4 p. Figure 1: Schemes of the three types of rivernk protection. In order to compre the species diversity of these three types of rivernk protection, environmentl fctors nd locl topogrphic profile need to e priorly studied. First, ll protection sites re locted etween 25 nd 5 meters high in order to minimize the ltitude influence on vegettion structure. The ges of rivernk protections re lso considered s determining fctor especilly to tke into ccount the progression of species colonistion nd ecologicl succession processes. We compred plnt species diversity nd niml txonomic diversity ove ground (eetles) on five sites for ech type of rivernk protection. Anlyses were lso mde on the verge numer nd frequency of exotic plnt species for ech type of rivernk protection. Vegettion ws smpled long three longitudinl trnsects using the point contct method. Coleopter genuses were smpled in the ir y trpping (yellow Flor owl trp). The fifteen sites smpled were locted in the Rhône-Alpes region (South Est Frnce). As result, 148 plnt species nd 78 eetle gener were recorded. We found significntly lower plnt diversity on riprp constructions ( Minerl ) thn on oth other types. Surprisingly, plnts diversity ws higher, even if not significntly, in comined works ( Mixed ) thn in purely vegettive ones ( Vegetl )(figure2). Coleopter genius diversity ws clerly linked to the type of rivernk protection. Thus we counted n verge numer of 12.2 coleopter genus for the Vegetl type, 7.2 for the Mixed ctegory nd only 3 genuses for the Minerl type (figure 3). Species numer verges Plnt species verge numers on ech type of rivernk protection ccording to their positions on the river nk. Trnsect 1 Trnsect 2 Trnsect 3 Totl Position on the rivernk Minerl Mixed Vegetl Figure 2: Br chrt of plnt species verge numer on ech type of rivernk protection ccording to their positions on the river nk. Genus verge numer Coleopter genus verge numer in yellow trps relted to the type of rivernk protection. Vegetl Mixed Minerl Rivernk types Figure 3: Br chrt of coleopter genus verge numer in yellow trps relted to the type of rivernk protection. We found out tht riprp techniques were more sujected to exotic invsions thn techniques using ioengineering. Indeed, the numer of exotic species (figure 4) is lmost the

4 CAVAILLE, P., DE DANIELLI, S., DAUMERGUE, N., EVETTE, A Biodiversity in rivernk techniques for erosion control: ssessment of niml nd plnt species diversity long nturlity grdient. 7th SER Europen Conference on Restortion Ecology, Ecologicl Restortion nd Sustinle Development, 23-27/8/21, Avignon, FRA. 4 p. sme etween the three types ut the frequency (figure 5) is clerly higher for the Minerl type. Averge numer 2,5 2 1,5 1,5 Invsive species verge numers relted to the type of rivernk protection. Vegetl Mixed Minerl Rivernk types Figure 4: Br chrt of invsive species verge numers relted to the type of rivernk protection. Averge frequency Invsive species frequency verges for ech type of rivernk protection. Vegetl Mixed Minerl Rivernk types Figure 5: Br chrt of invsive species frequency verges for ech type of rivernk protection. This study highlights mny differences etween the three types of rivernk protections. Indeed, plnts diversity is clerly lower on the Minerl type. This phenomenon my e relted to the sustrtum composition which is not conducive to plnt colonistion. We found tht plnts diversity ws higher, even if not significntly, on comined works ( Mixed ) thn on purely vegettive ones ( Vegetl ). This result cn e explined y the presence of rough riprp on the lower prt of the rivernk. It forms second colonistion front (following the one t the top of the rivernk) which prticulrly enles helophytic plnt colonistion. Moreover, willows used for fscines re generlly fst growing trees (Newsholme 23; Adm 28). Consequently, they inhiit plnt species colonistion y reducing light nd spce vilility. Likewise, mjor result is the reltionship etween the verge numer of coleopter genus in yellow trps nd the type of rivernk protection. The coleoptern diversity is significntly lower on Minerl protection type. This result is consistent with previous studies (Lecomte nd Pouzt 1986; Phm-Delegue nd Besson 1992). It cn e explined y the lck of vegettion which plys key role in hitts formtion y providing shelters nd source of food for nimls. The results of coleopter diversity on Mixed nd Vegetl types moderte the previous oservtions on flor diversity. Thus, we took census tht ws sustntilly higher on Vegetl protection type thn on Mixed type. This result confirm tht Slix genus is importnt hitt for insects (Sommerville 1991) s it provides very erly nd undnt source of food (Newsholme 23). The nlyses conducted on exotic species (including Fllopi jponic, Budlei dvidii nd Solidgo Cndensis) show tht the numer of invsive species is nerly the sme on every type of rivernk protection. By contrst, their frequency is gretly superior on the minerl type. The invsion is not prolem in itself. However, since the invsive species ecome undnt, the thret to nturl or restored systems ecomes significnt (Siemens nd Blossey 27). This result demonstrtes the cpcity of rivernk ioengineering to limit invsive species development. It underlines n inter-species competition etween invsive species nd plnts used for ioengineering. To conclude, this study gives new insights into niml nd plnt iodiversity of rivernk protections ginst erosion, rnging from entirely minerl to purely vegettive constructions. It lso provides useful informtion to prctitioners y providing them with useful dt to choose techniques in reltion to their future impct on iodiversity. However,

5 CAVAILLE, P., DE DANIELLI, S., DAUMERGUE, N., EVETTE, A Biodiversity in rivernk techniques for erosion control: ssessment of niml nd plnt species diversity long nturlity grdient. 7th SER Europen Conference on Restortion Ecology, Ecologicl Restortion nd Sustinle Development, 23-27/8/21, Avignon, FRA. 4 p. our results should e complemented with: (i) studies on other techniques of rivernk protection s well s on nturl rivernks to set reference; (ii) hydroiologicl surveys to evlute the influence of the rivernk protection type on qutic mcro inverterte diversity; (iii) dichronic pproch in order to figure out the evolution of iodiversity; (iv) studies on functionl diversity to ssess the ecologicl functions of these restored ecosystems. Biliogrphy: Adm, P., N. Deiis, F. Gerer, B. Lcht. (28). " Le génie végétl, Un mnuel technique u service de l'méngement et de l resturtion des milieux qutiques." Ministère de l'écologie, du développement et de l'méngement durles. Alpert, P., E. Bone, et l. (2). "Invsiveness, invsiility nd the role of environmentl stress in the spred of non-ntive plnts." Perspectives in Plnt Ecology Evolution nd Systemtics 3(1): Decmps, H. (23). "Ripisylves : l iodiversité pr l'instilité = Biodiversity through instility." Journées d'études sur les ripisylves méditerrnéennes. Lecomte, C. nd J. Pouzt (1986). "Etude electrontennogrphique de l reception de stimulus odornts d'origine vegetle chez Acrolepiopsis ssectell." Entomologi Experimentlis et Applict 4(1): Newsholme, C. (23). Willows. The genus Slix., Timer Press. Phm-Delegue, M.-H. nd M.-J. Besson (1992). Bses comportementles et chimiques de l reltion insecte pollinisteur-plnte: le modèle Aeille-Tournesol en production de semences hyrides. Pris, Université de Pris 6: 299. PlntyTcchi, A. M., E. Tcchi, et l. (1996). "Invsiility of species rich communities in riprin zones." Conservtion Biology 1(2): Schnitzler-Lenole, A. (27). Biodiversité végétle. Forêts lluviles d'europe. Pris, Tec et Doc: 388. Siemens, T. J. nd B. Blossey (27). "An evlution of mechnisms preventing growth nd survivl of two ntive species in invsive ohemin knotweed (Fllopi x ohemic, Polygoncee)." Americn Journl of Botny 94: Sommerville, A. H. C. (1991). "Willows in the environment." Proceedings - Royl Society of Edinurgh, Section B 98: Thuiller, W. (27). "Biodiversity: Climte chnge nd the ecologist." Nture 448(7153): Vitousek, P. M., C. M. Dntonio, et l. (1997). "Introduced species: A significnt component of humn-cused glol chnge." New Zelnd Journl of Ecology 21(1): 1-16.