Risk assessment Robinia pseudoacacia L.

Naamloos-2 1 15-03-13 08:10 © Naturalis Biodiversity Center, Leiden March 2013

Naamloos-2 2 15-03-13 08:10 Risk assessment Robinia pseudoacacia L.

E. Boer

March 2012

Naamloos-2 1 15-03-13 08:10 Naamloos-2 2 15-03-13 08:10 Table of contents

1. Introduction — 5

2. Robinia pseudoacacia: description, ecology and history — 6 2.1. Description — 6 2.2. Ecology — 6

3. Risk assessment — 8 3.1. Entry — 8 3.2. Establishment — 8 3.3. Spread — 8 3.4. Endangered areas — 9 3.5. Impact — 10 3.5.1. Ecological impact — 10 3.5.2. Economic impact — 10 3.5.3. Social impact — 11

4. Risk management — 12 4.1. Prevention of deliberate planting — 12 4.2. Prevention of dispersal — 12 4.3. Eradication and control — 12 4.4. Conclusions — 13

5. References — 14

Annex 1 Risk assessment scores using the ISEIA protocol — 16

This report was commissioned by the Invasive Alien Species Team of the Netherlands Food and Consumer Product Safety Authority.

Table of contents 3

Naamloos-2 3 15-03-13 08:10 4 Risk assessment Robinia pseudoacacia L.

Naamloos-2 4 15-03-13 08:10 1. Introduction

Exotic, invasive plant species have a negative impact on biodiversity, economy and/or public health. For this reason the Invasive Alien Species Team of the Netherlands Food and Consumer Product Safety Authority has requested a risk assessment for Robinia pseudoacacia.

The current risk assessment will focus on the situation in the Netherlands and discuss the following subjects: • Probability of entry • Probability of establishment in the Netherlands • Probability of spread • Identification of endangered areas based on the results of the three previous subjects • Impact of Robinia pseudoacacia in respect to ecological, economical and public health aspects • Management options to eradicate the species • Management options to control further spread and reduce impact.

This report is based on published literature, either in print or in the internet.

Introduction 5

Naamloos-2 5 15-03-13 08:10 2. Robinia pseudoacacia: description, ecology and history

2.1. Description 2.2. Ecology Robinia pseudoacacia is a deciduous tree belonging Robinia pseudoacacia is a native to eastern North to the Fabaceae family. It is a fast-growing tree America. It is a pioneer species, which is replaced up to 15-30 m in height, up to 120 cm in diameter, already after 20-30 years through successional bark of saplings smooth and green, mature tree processes. It is found on a wide variety of sites but with dark brown and deeply furrowed bark, with does best on rich moist limestone soils and soils flat-topped ridges, up to 4 cm thick, stem forking without pronounced subsoil development. Its native in ascending branches and horizontal and more range is classified as humid and climatic conditions crooked-growing branches; branches glabrous, are: January average daily temperatures: -4° to 7°C, branches of seedling and sprouts with stout, paired August average daily temperatures: 18° to 27°C, stipular spines, buds almost invisible (sunken in mean length of frost-free period, 150 to 210 days tissue) and terminal bud absent. Leaves alternate, and normal annual total precipitation: 1020-1830 20-30 cm long, imparipinnate with (7-)9-25 leaflets, mm, elevation is up to 1040 m a.s.l. (Huntley, 1990) leaflets oval to rounded, leaflet tip mucronate, dark Black locust is very sensitive to poorly drained or green above and pale green beneath. Inflorescences compact plastic soils. Excessively dry sites are drooping clusters, about 15 cm long, arising from also poor for the species. As a species with pioneer leaf axils near the tip of new shoots, flowers up to characteristics it is intolerant of shade and compe- 2 cm long, white with a yellow blotch on the upper- tition of herbaceous vegetation (Huntley, 1990). most petal, fragrant. Fruits: pods, 5-10 cm long, flat, smooth and glabrous, with 4-8 dark, 3-5 mm long seeds (van der Meijden, 2005; Wieseler, 2005; Stone, 2009; de Koning et al., 2009).

Species closely resembling Robinia pseudoacacia (Black locust) are Robinia viscosa (with pink flowers) and Robinia hispida (with rose-purple flo- wers); all three Robinia species are native to the Appalachians. These two resembling species, when used in cultivation, may share Black locust’s invasive tendencies (Wieseler, 2005).

6 Risk assessment Robinia pseudoacacia L.

Naamloos-2 6 15-03-13 08:10 Figure 1 Winter aspect of Robinia pseudoacacia.

Description, ecology and history 7

Naamloos-2 7 15-03-13 08:10 3. Risk assessment

3.1. Entry 3.2. Establishment The first introduction ofRobinia pseudoacacia in Eu- Robinia pseudoacacia is found naturalized in the rope from North America dates back to the year 1601. following countries (Cabi, 2012; Başnou, 2006; see The tree was brought to France (Muller, 2004). It was Figure 3): planted as an ornamental and for timber production. • Europe: Albania, Austria, Belarus, Belgium, In the Netherlands the first record is of 1847, by 1879 Bosnia-Hercegovina, Bulgaria, Croatia, Cyprus, the tree is said to be common and naturalized near Czech Republic, Denmark, Finland, France, Den Bosch (van der Ham, unpublished). Today it is Germany, Greece, Hungary, Ireland, Italy, Latvia, still the most widely planted American tree species Liechtenstein, Lithuania, Malta, Moldova, in Europe (Başnou, 2006). Seedling production for the Netherlands, Poland, Portugal, Romania, European market is concentrated in Italy as seed- Russian Federation, Serbia, Slovakia, Spain, lings develop more rapidly in the warmer climate Sweden, Switzerland, Ukraine, United Kingdom when compared to northern Europe (Moraal, 2008). • Asia: Afghanistan, Bhutan, China, India, Israel, Japan, Jordan, North Korea, South Korea, Myan- Planting of Robinia pseudoacacia in the USA has mar, Nepal, Pakistan, Turkey receded due to the locust borer Megacyllene • Africa: Botswana, Kenya, Namibia, Réunion, South robiniae (Forster) (Coleoptera: Cerambycidae). Africa, Zimbabwe This borer is often the cause of rapid population • North America: Canada, Mexico, USA (native and declines in plantation settings (Stone, 2009). Borer introduced) attack is often followed by fungal attack, of which • South America: Argentina, Chile heart rot by Fomes rimosus is the most common • Oceania: Australia, New Zealand. (Converse, 1984). In Europe, it is the most widely distributed alien tree species (Lambdon, et al, 2008). More recently Black locust is planted for a wide range of objectives viz. erosion control, reclamation In the Netherlands, Robinia pseudoacacia is of drastically disturbed sites, windbreaks, nurse found throughout the country, see figure 4 with an crops, amelioration of sites, honey production, increased occurrence in the northern part of the and ornamental use (Muller, 2004). In Germany, country since 1980 (FLORON & NHN, 2012). 14.000 ha of Robinia has been planted (Starfinger & The probability of establishment in the Netherlands Kowarik, 2003) and in Hungary 20% of the forested is high, and has occurred widely. area is planted with Robinia providing 25% of the annual timber cut (Redei, 1997 in: CABI, 2012). By 1984 there were worldwide over 1 million hectares 3.3. Spread of Robinia pseudoacacia plantations (Sabo, 2000). Robinia pseudoacacia is mainly distributed by man and planted for a variety of purposes. Planted and Plantation for timber production has recently at- established trees can spread through seeds or, tracted a lot of attention, as the timber quality can more importantly, by means of sprouting. compete with that of imported tropical hardwoods; a silvicultural and economical analysis revealed Most natural reproduction of Black locust is that production of sawn timber with a rotation of 25 vegetative by means of root suckering and stump years would be economically feasible in the Nether- sprouting. Root suckers originate from endogenous lands (Oosterbaan et al. 2002). Currently, an estima- adventitious buds in the roots, primarily where ted 800 ha of plantations of Robinia pseudoacacia branch roots emerge from older roots. Sprouts arise exist in the Netherlands (Dirkse et al., 2006). from dormant buds at the root crown, or on the The probability of entry in the Netherlands is very lower portion of the trunk. Physical damage to roots high. and stems (top damage, cutting, burning)

8 Risk assessment Robinia pseudoacacia L.

Naamloos-2 8 15-03-13 08:10 Figure 2 White, fragrant flowers in drooping clusters. Figure 5 Sprouts with heavy thorns.

Figure 3 World distribution Figure 4 Distribution in the Netherlands

increases suckering and sprouting. Root suckering tion, hindering seedling establishment. Seedlings and stump sprouting forms groves (or clones) of also exhibit juvenile growth with rapid growth and trees interconnected by a common fibrous root sturdy thorns (Stone, 2009; Bossard et al., 2000). system. Lateral spread of these groves in a study in Ohio, USA, valued 1-3 m per year. In its native range In the USA Robinia pseudoacacia is abundant in Black locust roots may spread laterally up to 50 m. logged stands and responds immediately through Sprouts exhibit juvenile growth characterized by vigorous sprouting, rapid growth and increased rapid growth and heavy thorns. More suckers are abundance (Stone, 2009). produced in full sun, open areas and sandy loam soil than in shade, dense vegetation and heavy soils The probability of rapid spread by seed is low as (Wieseler, 2005; Converse, 1984; Stone, 2009). seeds have a low viability and are dispersed over short distances only. Spread by extension through Seed production starts at the age of six and good root suckers is slow, likely under 1 m/year. seed crops are produced every 1-3 years. The distance over which seeds are dispersed is limited. Seed production is abundant, but seeds rarely 3.4. Endangered areas germinate. This is due to seed coat impermeability In some cases nitrogen fixation can facilitate later- and high light requirements for germination. Seeds successional species in managed forests (Stone, remain viable in the soil for at least 10 years, mean- 2009; Huntley, 1990), but it may be a major concern ing that stands and groves create a soil seed bank. for land managers of nutrient-poor nature areas. This should be taken into account when devising In abandoned fields reverting back to forest within strategies to eradicate unwanted trees. Seedlings the oak-pine forest region of southern Poland, Black are intolerant of shade and herbaceous competi- locust reduced the number of woodland and grass­

Risk assessment 9

Naamloos-2 9 15-03-13 08:10 land species. The cover of nitrophilic and ruderal 3.5.1. Ecological impact herbaceous species was positively correlated with As leguminous species Robinia pseudoacacia can Black locust cover (Dzwonko & Loster, 1997 in: fix atmospheric nitrogen through symbiosis in its Stone, 2009; Konopska, 2011). Soil characteristics root nodules with Rhizobium bacteria. It is fairly are permanently altered by the input of nitrogen, specific with regard to its requirements for specific which poses serious problems in sandy and cal- strains of Rhizobium bacteria and it does perform careous grasslands in Germany; here the number best with strains from native trees (CABI, 2012). The of species is reduced to half under only 2-year old estimated symbiotic N fixation rate is 30-75 kg ha-1 Robinia plants (Starfinger & Kowarik, 2003). The yr-1 (Boring et al., 1988). The effect of Black locust pitch pine / scrub oak forest in New York, a forest on associated vegetation resulted principally from type poor in soil nutrients, is also threatened by a high annual turnover of nitrogen from limbs and Black locust invasion (Stone, 2009). Stream waters litter rather than from increased total nitrogen in draining out of areas with Robinia pseudoacacia the soil. An annual turnover of 56 kg ha-1 yr-1 was stands had 10-100 times the nitrogen concentration estimated in a 16-20-year old stand in the USA of streams draining out of nearby watershed of (Converse, 1984). mixed hardwoods (Sabo, 2000). Apart from the input of nitrogen, the openness of In southern Switzerland and northern Italy, Robinia certain landscapes is also at stake as the pioneer pseudoacacia has replaced entire valleys of chest- characteristics of Black locust allow it to establish nut (Castanea sativa) and many more areas in that easily in open conditions. In its natural area Robinia region are still being invaded (P.Cherubini, pers. pseudoacacia is being replaced by succession after comm., in: Sabo, 2000). 20-30 years, but in Germany it can survive for 40-50 years (Starfinger & Kowarik, 2003). The trees can In Belgium, dry grasslands are invaded by Robinia shade out native plants by forming dense colonies pseudoacacia (Branquart et al., 2010). (Kaufman & Kaufman, 2007) where little ground vegetation remains (Wieseler, 2005). In the south of the Netherlands, Robinia pseudoa- cacia is known to invade forests on steep slopes Endangered areas in Europe are natural, open sites, (“hellingbossen”) causing an influx of nutrients and various types of grasslands, and forest or woodland a corresponding change in species composition of margins from where the species can invade the the undergrowth (Duistermaat, pers.comm.). forest, generally with a low soil nutrient level. Sites invaded by Robinia pseudoacacia experience an ex- In conclusion, for the Netherlands the areas most tra input of nitrogen which results in an irreversible likely to be invaded by Robinia pseudoacacia are change of the soil nutrient status and consequently forests on slopes and calcareous grasslands in the a change in vegetation composition. High nutrient south of the country. levels favour more ruderal plant species and decre- ase the ecological value of the site.

3.5. Impact Robinia pseudoacacia produces robinetin and other The gall midge Obolodiplosis robiniae was observed allelopathic compounds which may affect the the first time in the Netherlands in 2003 and can ecological functioning of natural areas. reproduce rapidly with 3 generations per year. The It has once been stated that Black locust is a com- leaf miner Phyllonorycter robiniella is in the Nether- petitor for pollination by bees, suggesting that the lands since 1998. Both pests may prove harmful chance that native plants are pollinated is reduced to existing Robinia plantations (Moraal, 2008). This (Wieseler, 2005). may have ecological, economic and social impact.

10 Risk assessment Robinia pseudoacacia L.

Naamloos-2 10 15-03-13 08:10 The potential level of ecological damage in the Netherlands is moderate.

3.5.2. Economic impact Direct economic impact is limited to damage to built structures and pavements. Indirect economic impact involves the costs for control of Black lo- cust, i.c. removal from sites where it is not wanted.

The potential level of economic impact in the Netherlands is estimated to be very limited, both direct impact as well as indirect impact as costs involved for control.

3.5.3. Social impact Flowers, seeds, leaves and bark are toxic to humans and livestock; in humans the robinin contained in flowers and seeds provokes gastroentritis (Başnou, 2006; Bossard et al., 2000). Livestock do feed on the leaves, so toxicity is ambiguous. Working with the wood of Robinia pseudoacacia may cause allergic skin and eye reactions. Branches are susceptible to rot and when breaking off these present a health and safety risk (Booy et al., 2012).

The potential level of social impact in the Nether- lands is estimated to be very limited.

Risk assessment 11

Naamloos-2 11 15-03-13 08:10 4. Risk management

4.1. Prevention of deliberate planting debated. Cutting induces vigorous sprouting and Robinia pseudoacacia is widespread in the Nether- necessitates further measures. Repeated cutting lands. Moreover, trees for planting can easily be of sprouts for 4-5 more years can kill all trees. obtained from commercial tree growers; generally Incomplete girdling is a promising technique and these trees are one of the approximately 20 culti- has been applied in Germany. In winter a strip of vars which are on sale in the Netherlands. bark and sapwood 8 cm wide is removed from 9/10th of the circumference of the tree. In the following growing season the tree is completely girdled and 4.2. Prevention of dispersal can be cut later. In this way the tree doesn’t produce It is already explained that Black locust easily repro- root suckers or stem sprouts (Starfinger & Kowarik, duces from root suckers. Land managers not always 2003). realize that cutting of trees enhances vigorous regrowth of root suckers and necessitates increased When cutting trees, the best season to do so is in future control measures to limit dispersal. August which gave the lowest volume of sprouts (Yamada & Masaka, 2009). In southern Limburg As dispersal by means of seed is limited, fragile Robinia pseudoacacia, when cut in forest yields nature conservation areas, like dry grasslands, can 2 or more shoots, which need to be cut again and be protected by avoiding planting of Black locust leads to germination of seeds due to increased light within 500 m of these areas (Starfinger & Kowarik, reaching the soil (Kloet, 2012). 2003). In the Netherlands, this recommendation is appropriate for planting in the vicinity of calcareous Cutting trees in grassland in southern Limburg and grasslands like there are in southern Limburg. subsequent grazing to control shoots has not been successful, in part because grazing could not be done early in the growing season due to presence of 4.3. Eradication and control protected plants (Kloet, 2012) The vigorous regrowth after cutting makes monito- ring after control measures necessary. Moreover, Chemical measures it is generally recommended to avoid soil disruption Chemical control has shown variable success and as these areas are apt for recolonization by Black is less labour intensive than manual or mechanical locust. For the Netherlands, eradication of Black treatment. It is generally recommended to apply the locust is not practiced, as far as known. herbicides on the freshly cut surface. Foliar sprays are also used late in the growing season. They To control or eradicate trees, the following work best on thick patches under 2 m tall or small measures can be taken: isolated plants since every branch and stem needs • Manual to be treated. The cut part of girdled trees may also • Mechanical be treated with herbicides. • Chemical • Biological Control by chemical means has been successful using glyphosate, triclopyr, picloram, an atrazine- Manual measures simazine mixture and a fomasine ammonium Occasionally, new infestations in fragile ecosystems formulation (Stone, 2009; Heim, 2011). are uprooted by hand. It is important to remove roots as well (CABI, 2012). Biological measures In the USA domestic goats and cattle defoliated Mechanical measures Black locust and after 4 years of browsing all trees The efficacy of cutting and girdling systems is had been killed (Stone, 2009).

12 Risk assessment Robinia pseudoacacia L.

Naamloos-2 12 15-03-13 08:10 Figure 6 Robinia fruits

Robinia pseudoacacia can most easily establish in 4.4. Conclusions open areas with exposed soil. To prevent infestati- In the neighbouring countries of the Netherlands ons in fragile nature areas, soils disruption should Robinia pseudoacacia is an invasive plant of impor- as much as possible be avoided. It is recommended tance, particularly by its effects on the natural envi- not to prune existing trees as they may react with ronment. It can invade valuable nature conservation the production of root suckers and stem sprouts. areas, especially calcareous and dry grasslands. Infestations cause a shift in species composition, A predictive model to assess climate change sug- favouring more ruderal and less valuable plant gests that the area potentially invaded by Robinia species. The effects on the nitrogen balance of the pseudoacacia will increase considerably under a soil are irreversible and long-lasting. warmer climate. In case of Robinia pseudoacacia, reducing propagule pressure by avoiding purposeful For the Netherlands, identifying and monitoring plantation in the neighbourhood of reserves and en- those sites which are particular susceptible to dangered habitats is a simple but crucial measure Black locust infestations is important to take to prevent further invasion under a warmer climate effective measures if needed. Amongst the en- (Kleinbauer et al., 2010). dangered areas in the Netherlands are the forests on steep slopes (“hellingbossen”) in the southern In Belgium, Robinia pseudoacacia is on the “watch part of Limburg, where Robinia has been planted list” being widespread and with a moderate envi- for erosion control and the calcareous grasslands, ronmental impact hazard (Branquart et al., 2010). which are also located in southern Limburg. In Switzerland it is on the Black List of plant spe- However, undesirable spread and impact may also cies causing actually damage in the areas of biodi- occur in other areas throughout the country. versity, health, and/or economy; the establishment and the spread of these species must be prevented. Declared an invasive species in countries such as Austria, France and Spain. A potentially invasive species in Portugal (FOEN, 2006). In Denmark it is considered a problem for nature conservation (Starfinger & Kowarik, 2003).

Risk management 13

Naamloos-2 13 15-03-13 08:10 5. References

Başnou, C., 2006. Robinia pseudoacacia. Record in Federal Office for the Environment FOEN, 2006. DAISIE (Delivering Alien Invasive Species Inven- Invasive alien species in Switzerland – Fact­ tories for Europe) database. http://www.europe- sheets. 204 pp. aliens.org/pdf/Robinia_pseudoacacia.pdf FLORON, Stichting & Nationaal Herbarium Neder- [Accessed 5 March 2012]. land (NHN), 2012. FlorBase. http://www.floron.nl Branquart, E., Vanderhoeven, S., Van Landuyt, W., [data not online accessible] Van Rossum, F., & Verloove, F., 2010. Robinia Huntley, J.C., 1990. Robinia pseudoacacia L. - Black pseudoacacia – Black locust. Invasive species in Locust. In: Burns, R.M. & Honkala, B.H. (tech. Belgium. http://ias.biodiversity.be/species/ coords.). Silvics of North America: Vol. 2. Hard- show/15 [Accessed 5 March 2012] woods. Agriculture Handbook 654. U.S. Depart- Booy, O., Wade, M. & White, V., 2012. False-acacia. ment of Agriculture, Forest Service, Washington, https://secure.fera.defra.gov.uk/nonnativespe- DC. pp. 755-761. cies/downloadDocument.cfm?id=72 [Accessed Kaufman, S.R. & Kaufman, W., 2007. Invasive plants: 5 March 2012] a guide to identification and the impacts and Boring, L.R., Swank, W.T., Waide, J.B. & Henderson, control of common North American species. G.S., 1988. Sources, fates, and impacts of nitro- Stackpole Books, Mechanicsburg, USA. 458 pp. gen inputs to terrestrial ecosystems: review and Kleinbauer, I. Dullinger, S. Peterseil, J. & Essl, F., synthesis. Biogeochemistry 6: 119-159. 2010. Climate change might drive the invasive Bossard, C.C., Randall, J.M. & Hoshovsky, M.C. (Edi- tree Robinia pseudacacia into nature reserves tors), 2000. Invasive plants of California’s wood- and endangered habitats. Biological Conserva- lands. University of California Press, Berkely, Los tion 143(2): 382-390. Angeles. 360 pp. Kloet, P., 2012. Personal communication. CABI, 2012. Invasive Species Compendium (Beta). Konopska, K., 2011. Invasive alien plant species Robinia pseudoacacia (black locust) last modi- of the southern part of the Nowogard Plain fied 15 May 2008. http://www.cabi.org/isc/?com (NW Poland). Biodiversity: Research and Conser- pid=5&dsid=47698&loadmodule=datasheet&p vation 21: 31-38. age=481&site=144 [Accessed 6 March 2012] Lambdon, P.W., et al., 2008. Alien flora of Europe: Converse, C.K. 1984. Element Stewardship Abstract species diversity, temporal trends, geographical for Robinia pseudoacacia – Black Locust. http:// patterns and research needs. Preslia 80(2): www.invasive.org/weedcd/pdfs/tncweeds/ 101-149. robipse.pdf [Accessed 6 March 2012] Moraal, L., 2008. Insectenplagen op bomen en De Koning, J., van den Broek, W., De Meyere, D. & struiken in bos en landelijk gebied in 2007. Bruens, H., 2009. Dendrologie van de lage Vakblad natuur, os en landschap 5(7): 23-27. landen. 14e druk Nederlandse Dendrologie. Muller, S., 2004. Robinia pseudoacacia L. Le robinier KNNV Uitgeverij, Zeist. 547 pp. faux-acacia. In: Muller, S. (Coordinateur): Dirkse, G.M. et al., 2006. Meetnet Functievervulling Plantes invasives en France. Muséum national bos 2001-2005. Vijfde Nederlandse Bosstatis­ d’Histoire naturelle, Paris. Patrimoins naturels tiek. Directie Kennis, Ministerie van Landbouw, 62. pp. 92-93. Natuur en Voedselkwaliteit, Ede. 95 pp. Oosterbaan, A., van de Berg, C.A., de Jong, J.J. & Duistermaat, H., 2012. Personal communication. Olsthoorn, A.F.M., 2002. Mogelijkheden en Heim, J., 2011. Vegetation management guideline beper­kingen voor de teelt van Robiniahout in Black Locust (Robinia pseudoacacia L.). Nederland. [Possibilities and constraints of the http://www.inhs.uiuc.edu/research/VMG/ cultivation of Robinia timber in the Nether- blocust.html Prairie Research Institute, Univer- lands]. Alterra rapport 678. Alterra, Research sity of Illinois-Champaign. [Accessed 6 March Instituut voor de Groene Ruimte, Wageningen. 2012] 54 pp.

14 Risk assessment Robinia pseudoacacia L.

Naamloos-2 14 15-03-13 08:10 Sabo, A.E., 2000. Robinia pseudoacacia invasions and control in North America and Europe. Resto- ration and Reclamation Review 6(3). 9 pp. http:// conservancy.umn.edu/bitstream/59729/1/ 6.3.Sabo.pdf [Accessed 6 March 2012] Starfinger, U. & Kowarik, I., 2003. (updated by F. Klingenstein in 2008 and by M. Dirk in 2010). Robinia pseudoacacia L. (Fabaceae), Robinie. http://www.floraweb.de/neoflora/handbuch/ robiniapseudoacacia.html [Accessed 5 March 2012]. Stone, Katharine R. 2009. Robinia pseudoacacia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Labo- ratory (Producer). Available: http://www.fs.fed. us/database/feis/ [2012, March 5]. Van der Ham, R.W.J.M., unpublished. Robinia pseu- do-acacia L. From: Archives Atlas Flora van Nederland, Leiden. van der Meijden, 2005. Heukels’ Flora van Neder- land. 23e druk. Wolters-Noordhoff, Groningen/ Houten. 685 pp. Wieseler, S., 2005. Factsheet Black locust. Plant Conservation Alliance’s Alien Plant Working Group - Weeds Gone Wild: Alien Plant Invaders of Natural Areas. http://www.nps.gov/plants/al- ien/fact/rops1.htm [Accessed: 23 January 2012] Yamada, K. & Masaka, K., 2009. Dynamics in growth and survivals of Robinia pseudoacacia sprouts occurred after cutting conducted in different seasons. Journal of the Japanese Forest Society 91(1) 42-45. [in Japanese]

References 15

Naamloos-2 15 15-03-13 08:10 Annex 1

Risk assessment scores using the Colonization of high conservation value habitats: In ISEIA protocol. Germany and Belgium, grasslands with a low nutri- ent profile have been invaded. These are areas with The following risk assessments is based on E. Bran­ a high conservation value. Calcareous and dry quart (Editor), 2009. Guidelines for environmental grasslands are rare in the Netherlands, hence the impact assessment and list classification of non- risk for the category is assessed to be low (score 1). native organisms in Belgium. version 2.6 dated 7-12- 2009, commonly referred to as the ISEIA - Invasive Adverse impacts on native species: It is well know Species Environmental Impact Assessment - proto- and documented that forest with Robinia pseudoa- col. These guidelines are published at: http://ias. cacia as one of its components seriously alters the biodiversity.be/documents/ISEIA_protocol.pdf. nutrient status of the soil by eutrophication; this ef- fect is long-lasting. Through this process species This protocol aims to assess environmental risks composition is changed and more ruderal species only and do not take into consideration the direct are found. This indirect effect on native species and impact of non-native species on human interests. its long-lasting effect allow for a medium risk (score 2). The risk categories are scored as follows: Score 1: risk is low Alteration of ecosystem functions: Eutrophication is Score 2: risk is medium an explicit element of the functioning of an ecosys- Score 3: risk is high tem. The input of nitrogen and its long-lasting effect on the nutrient status of the soil allow for a medium In Belgium, the ISEIA protocol has also been adopt- (score 2) in this category. ed and Robinia pseudoacacia obtained a total score of 10. The different scores are detailed for every type of risk in the ISEIA protocol.

Risk Risk category Dispersion potential or invasiveness 2 Colonization of high conservation value habitats 1 Adverse impacts on native species 2 Alteration of ecosystem functions 2

Dispersion potential or invasiveness: Robinia pseu- doacacia doesn’t colonize remote places as the dis- persal potential (by seed) is limited, except when assisted by man. The reproduction potential and vegetative reproduction capacities are high and the species is found more or less throughout the coun- try, therefore the risk for this category is assessed as medium (score 2).

16 Risk assessment Robinia pseudoacacia L.

Naamloos-2 16 15-03-13 08:10 Strategische prioriteiten 17

Naamloos-2 17 15-03-13 08:10 18 Risk assessment Robinia pseudoacacia L.

Naamloos-2 18 15-03-13 08:10