Asian knotweed (Reynoutria spp.)
Experiments in using grazing to manage Japanese knotweed in the Mayenne department t
M s ayenne departmental council 1 e u O
(CG 53) s u n p
CG 53 manages the departmental network for the m a c o
management of invasive alien plants in a partnership with r g A the departmental federation for fishing and the protection of aquatic environments. ©
n Moulin à papier B
CG 53 is both the owner of the site in the B E S sensitive natural area in the town of Saint-Calais-du-Désert © and the manager of the site restoration project: - the work was part of the management plan for the Saint- Calais sensitive natural area drawn up by the Normandie- Maine regional nature park to “manage invasive species, primarily Japanese knotweed and balsam”; - the work was carried out in collaboration with Agrocampus Ouest (Rennes).
1 t
Contacts: Sandrine Forêt (CG 53) [email protected], s e Jacques Haury (Agrocampus Ouest) - jacques.haury@agro - u O
s campus-ouest.fr u p m
Michel Bozec (Agrocampus Ouest) - michel.bozec@agro - a c o campus-ouest.fr r g A
© Intervention site n The Moulin à papier site is a wetland upstream of the Mayenne River, in the Saint-Calais-du-Désert sensitive natural area. The experiments were conducted on several colonised sites within the former poplar grove: - sector A, a grazed area in an enclosure measuring 11 352 square metres; 1. Study site. - northern sector, that consists of an enclosure (grazed) and 2. Diagram of the Moulin à papier experimental site. an exclosure (not grazed); - control sector, located to the south of the house, not n At the end of 2010, it was decided to try another management grazed and divided into two parts. Te.1 is the non-grazed method in 2011, namely using goats to consume the control sector for transects T1 to T6 in sector A and Te.2 is knotweed. the non-grazed and tarped control sector for transect T0 in sector A. Disturbances and issues involved n The initial experiments concerning Reynoutria japonica on this site (mowing and burning of the plants) took place in n The presence of Reynoutria japonica was observed for the 2009. first time on the Moulin à papier site between 2005 and 2007, n In 2010, mowing followed by tarping was experimented and confirmed in 2008 during the examination done in the and the first assessments concerning surface areas and framework of the site management plan drafted by the biomass quantities were conducted. Normandie-Maine regional nature park.
94 n Reynoutria japonica Th e former poplar grove was colonised by following a 3 logging operation that disseminated the rhizomes of the initial population that was planted by the miller to enhance the landscape. In 2011, three colonies t s
measuring 60, 200 and 1 500 square metres were noted. e n Reynoutria japonica u O
CG 53 set up experiments on how to manage and the s u
impacts of its colonisation. p m a c n o
Ecological impacts r g A n Long-term damage to rivers banks due to erosion. © n A reduction in the number of native plant species due to competition with Reynoutria japonica for nutrients and light (with a general closing in of the 4 environment). n Impacts on land use n The plants are a hindrance for fishing, hunting, etc. n Management of Reynoutria japonica was set up in the framework of the
restoration policy for the wetland. 3 5
G C
© Interventions n Since 2009, CG 53 has worked to restore the wetland while limiting the 5 propagation of the knotweed and progressively reducing the stands. The unsatisfactory results produced by the management techniques employed in 2009 and 2010 led to the decision to use goats in 2011. Agrocampus Ouest was selected to monitor the effectiveness of the technique.
n Grazing as a management method 3 5
n G
On 13 July 2011, the day they were weaned (except for two or three animals C
already one year old), 13 male, domestic goats ( Capra aegagrus hircus ) were © brought to the site: 3. Control sector colonised by Reynoutria japonica. - reproduction was not an issue; 4. 5. Domestic goats ( Capra aegagrus hircus ). - the species was suited to underbrush with regrowth of woody plants. n The animals were present the entire year on the site. n A local, retired person checked the animals daily for a fee. n The pen, approximately one hectare in size (10 000 square metres), was set up and maintained by the Études et Chantiers social reintegration association. n A rotary cutter was used to mow or create passages inside the pen from July to September in order to provide the animals with paths and more accessible land. n The trees in the pen were protected against stripping of the bark by the animals. n Scientific monitoring n Monitoring was conducted in 2011 using quadrants (biomass samples) and a set of transects for plant inventories during three periods, two prior to grazing in June and July and one during grazing at the end of September. The observations and measurements were made in all the sectors, including the two control sectors Te. 1 et Te.2 (R = with Reynoutria ) that were not grazed. n Plant inventories: - the study areas were quadrants (2 m x 2 m) positioned along the transects in areas with Reynoutria (R) and in others without (S). Each transect received two quadrants, 1 R and 1 S; - each quadrant was photographed and geolocated (GPS).
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© IIBSN© Agrocampus Ouest A 7
Japanese knotweed
Other species in )
² knotweed quadrant m / Other species in quadrant M without knotweed D g (
s s a m o i B 3 5
G C
© Campaigns: June 2011 July 2011 August 2011 Sept. 2011
8 B Japanese knotweed
Other species in
) knotweed quadrant ² m
/ Other species in quadrant without knotweed M F g (
s s a m 3 o i 5
B G C
©
7. Grazed area at the end of September 2011. Campaigns: June 2011 July 2011 August 2011 Sept. 2011 8. Comparison between a control zone (left) and a grazed area (right) in 2012.
A. Average dry biomass. B. Average fresh biomass.
n Assessment n Certain animals had difficulty in adapting to the environment. Two had to be removed from the site and two others died due to ectoparasites (their young age made them more susceptible to parasites). n The animals immediately (the first day) started eating the Japanese knotweed For more information throughout sector A. n The use of the rotary cutter between the last two campaigns had an impact on the environment that probably modified the interpretation of the results. But did it n Haury J., Moreau C., Bozec M., Druel influence the consumption of knotweed by the goats or contribute to dispersing A., Paulet Y., Cabral T. 2012. stalk fragments and rhizomes? Expérimentation de gestion raisonnée Reynoutria n The costs incurred by this project were not available. de la Renouée du Japon ( japonica ) sur le site du « Moulin à papier », Outlook à Saint-Calais du Désert (53). Synthèse d’intervention 2011 et rappel des résultats n Reynoutria japonica Management of by grazing will be pursued and monitored. 2010. Agrocampus Ouest site de I Rennes, Dreal Pays de la Loire et nformation on the project Conseil général de la Mayenne. 48 pp. n n The work was presented during the national symposium on Asian knotweed Bozec M. 2013. Précisions sur le held on 23 and 24 October 2012 in the city of Saint-Étienne. protocole élaboré par AgroCampus Rennes pour le suivi du pâturage des renouées par les chèvres des fossés, Author: Sandra Fernandez, Irstea CG53, Moulin à Papier, St Calais du désert. 1 pp.
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