Ecology and distribution of Nardus stricta L. () – an alien invader into New Zealand

W.D. Kissling1,2,4, M. Schnittler2, P.J. Seddon3, K.J.M. Dickinson1 and J.M. Lord1

1Botany Department, University of Otago, P.O. Box 56, Dunedin, New Zealand. 2Botanical Institute and Botanical Garden, University of Greifswald, Grimmer Strasse 88, 17487 Greifswald, Germany. 3Zoology Department, Otago University, P.O. Box 56, Dunedin, New Zealand. 4Corresponding author e-mail: [email protected]; Current address: UFZ Centre for Environmental Research Leipzig-Halle, Department of Ecological Modelling, Permoserstr. 15, 04318 Leipzig, Germany.

(Received 13 May 2004, revised and accepted 12 August 2004)

Abstract

The European matgrass Nardus stricta L. (Poaceae), a perennial grass native to Central and Eastern Europe, was first recorded in New Zealand in 1904. A brief description of the species is given, and the ecology of Nardus stricta in its native habitat, and global invasion patterns are briefly summarised. Current knowledge of its distribution within New Zealand is presented based on records from New Zealand herbaria, databases, private sources, and own observations. Three patterns are identified which characterise the current distribution: the species is mainly found (1) on the South Island, (2) on damp soil (e.g. swampy pasture, ephemeral wetlands, kettle depressions, seepages etc.), and (3) in areas that are used for pastoral grazing. Due to the species’ characteristics and the potential impact on indigenous biodiversity and pastoralism, it is recommended that Nardus stricta be regarded as a potential environmental weed in New Zealand. It is most likely to invade low stature vegetation on acid soils, e.g. cushion communities or ephemeral wetlands, and invasion is probably assisted by grazing.

Keywords: exotic species - Nardeae - distribution map - habitat preference.

Introduction little is known about Nardus in New Zealand. Due to its growth form and The European matgrass Nardus stricta its ability to dominate extensive areas L. (Poaceae) (monotypic , Nardus and to replace other , the hereafter), a perennial tussock grass species might be a potential serious native to Europe, was introduced to environmental weed, both for New Zealand approximately 100 years pastoralism and nature conservation. ago (Meusel et al. 1965). Currently, Already listed as a “noxious weed” in

New Zealand Natural Sciences (2004) 29: 1-12 2 New Zealand Natural Sciences 29 (2004) the USA (United States Department of (Hubbard 1992; Edgar & Connor Agriculture 2004), in New Zealand 2000). Outer leaves of tussocks are Nardus is not yet recognised as an spreading at right angles to the environmental weed (M. Newfield & sheaths when mature (Figure 1). The C.J. West, Department of Conservation, inflorescence is a slender unilateral pers. comm.). The aim of this paper is spike with up to 20 . The thus to identify the weed potential of single flowered spikelets are born in Nardus in New Zealand. A description depressions forming two rows along one of the species is given, the ecology of side of the spike axis. Flowers are Nardus in Europe is summarised briefly hermaphroditic and protogynous, and along with global invasion patterns, and apomictic seed production has been current knowledge about the species suggested (Chadwick 1960a). distribution in New Zealand is Growth form and regeneration presented. The growth of the rhizomes around the The ecology of Nardus stricta L. perimeter and the closeness of the (Poaceae) based on knowledge from shoots result in a hemispherical clump Europe giving the species its typical caespitose growth form (Zhukova 1974). In dense General features stands Nardus often forms a thick mat Nardus is a wiry, 10 - 40 (-60) cm tall (hence the common name matgrass), and densely tufted perennial tussock and due to trampling it can adopt a grass with tillers closely packed on flattened growth form (Grime et al. laterally branching rhizomes (Figure 1). 1988). Limited growth and branching Leaves are greyish-green and blades are of the rhizome system followed by decay stiff, sharp-pointed and tightly inrolled of the older rhizomes can result in daughter plants (Chadwick 1960a). Nardus can also regenerate from detached pieces of rhizome (Chadwick 1960a; Grime et al. 1988). However, Nardus does not produce stolons and lateral spread by vegetative reproduction is thus limited in distance. Reproduction by seed is important for colonisation of bare ground (King 1960), but is less important in closed vegetation (Grime et al. 1988). Seeds are rarely seen to germinate in the field, but are capable of germination (Chadwick 1960a). Clumps of Nardus approximately 20 cm in diameter can Figure 1. A single tussock of Nardus stricta. produce up to 2000 florets under Note the outer leaves which are spreading at favourable conditions. Dispersal of the right angles to the sheaths, and the unilateral spikes with slender, single-flowered spikelets. detached florets is thought to occur Drawing kindly provided by J. Weinbecker. “through the agency of grazing W.D. K ISSLING ET AL: Nardus stricta in New Zealand 3 animal, wind, rain and snow” from the mountains of southern Europe (Chadwick 1960a). and the plains of western Asia to western Greenland (Meusel et al. 1965). It Competitive ability occurs from sea level to quite high Nardus is a relatively slow growing altitudes, commonly to 1000-2000 m species (Bradshaw et al. 1958, 1964; altitude, and ascending to 3000 m in Grime et al. 1988) and does not the Swiss Alps and to 3500 m in the compete successfully with other Grand Atlas mountains (Chadwick species in more fertile habitats 1960a). (Chadwick 1960a). This is because Nardus is currently shrinking in Nardus is intolerant of shade and can distribution and declining in be shaded out where it grows with abundance in its native range in central potentially taller plants (Chadwick Europe (Pott 1995; Ellenberg 1996). 1960a). However, on poorer substrates The main reasons are thought to be (Chadwick 1960a) and where grazing fertilisation and intensification of land reduces the competitive ability of other use, afforestation, or abandonment of species (Welch 1986; Grant et al. farm land (Mertz 2000). Apart from 1996), Nardus effectively competes Nardus communities that naturally with other plants. Once established it occur at higher altitudes of mountainous can exclude smaller species due to its areas, most at lower altitudes are of growth form, which allows the anthropo-zoogenic origin, i.e. they to suppress surrounding vegetation arose from deforestation and subsequent (Zhukova 1974). Its potential to grazing of the areas by sheep, cattle, and dominate extensive areas is well known goats (Wilmanns 1998). Due to land from Europe (Tansley 1939; Grime use changes in central Europe, Nardus et al. 1988; Ellenberg 1996). communities are now regarded as threatened there (Pott 1995). However, Habitat and distribution of Nardus in its in the British Isles, Nardus has increased native range in distribution and abundance and is Nardus occurs in a great variety of considered to be a major problem for habitats, but mainly acidic and damp pastoralism due to its low productivity but not permanently wet soils, avoiding and palatability (Fenton 1936, 1937; regions with less than 500 mm average Rawes 1961; Grant et al. 1996; annual precipitation (Tansley 1939; Armstrong et al. 1997). Chadwick 1960a). It is present on soil types ranging from brown earths, Global invasion patterns podsols, gleys, peat podsols to peats, but tends to be most abundant where the Nardus has been introduced to several substrate is relatively calcium-deficient. other countries. The species is listed as The distribution of Nardus seems a ‘noxious weed’ in the USA where it is neither to be limited by topographical found in the north eastern states of preferences nor by extremes of Michigan, New York, New Hampshire temperature (Chadwick 1960a). and Massachusetts, and in the north Nardus has a wide natural western states of Idaho and Oregon geographical distribution and is present (United States Department of 4 New Zealand Natural Sciences 29 (2004)

Agriculture 2004). Furthermore, and local in the South Island, not being there are records in north Canada reported from Westland and Fiordland. from Quebec, Nova Scotia and However, there is no information given Newfoundland, and from Greenland, on distribution records of Nardus in though it is not clear whether it is New Zealand. introduced or indigenous in the latter Distribution records two regions (Chadwick 1960a). In Central America, Nardus has been New Zealand museums and other found in upper pastures at the institutions were contacted and asked Volcán Turrialba, Costa Rica, at 3000- for herbaria and database records to 3300 m altitude (Pohl 1987). Early gather information on distribution introductions of mixtures of European records of Nardus in New Zealand. pasture grasses, which were imported There are twenty-one records for Nardus to provide forage for dairy cattle, are in New Zealand (Table 1), and twenty thought to be the seed source for its of them are distribution records establishment (Pohl 1987). In South whereas one is cultivated material only America, Nardus has been reported from (Figure 2, Table 1). There was only one the Falkland Islands, although the location in the North Island, and one record is doubtful since subsequent from the Chatham Islands. Here it most botanists were unable to confirm it and likely arrived in seed mixtures for no herbarium specimen exists (Nicora pasture establishment (B.P.J. Molloy, 1978). In the South Pacific, Nardus Landcare Research, pers. comm.). In the occurs in swampy areas at Mount South Island, almost all records were Huxley near Queenstown in western from the eastern side of the Main Tasmania, a region with an annual mean Divide. The dates of the records ranged precipitation of about 2500 mm (J. from 1926 to 2003 and most records Kirkpatrick, University of Tasmania, were old (65% are older than 30 years). pers. comm.). From the distribution records three patterns emerge: Nardus invasion in New Zealand (1) Nardus is mainly found on the South Island. The distribution records Invasion history and current state of suggest that Nardus occurs throughout knowledge the South Island except the west The earliest record of Nardus in New coast (Table 1, Figure 2). In the North Zealand is from Meusel et al. (1965) Island, the species is confined to the who report, without substantiation, higher mountain region of the Volcanic that the species had been found in New Plateau. An explanation for this Zealand since 1904. In contrast, Edgar distribution pattern might be that et al. (1991) note the first Nardus the macroclimate of the South Island record in New Zealand from 1935 as is most suitable for the species. In reported by Allan (1935) from the its native habitat Nardus occurs Dunedin area. Edgar & Connor (2000) throughout Europe but is confined to report that the species occurs on the the higher mountain regions in Volcanic Plateau (Waimarino) in the southern Europe (Chadwick 1960a). North Island, and that it is scattered The South Island has a climate more W.D. K ISSLING ET AL: Nardus stricta in New Zealand 5

Figure 2. Distribution records of Nardus stricta in New Zealand. Numbers (1-20) refer to locations listed in Table 1. similar to central and eastern Europe, predictive power of this approach has where Nardus has its native core varied and it does not appear to be a distribution. The climate of the South very reliable circumscription of invasive Island is more temperate and cooler limits (Wilson et al. 1992; Mack 1996). than the climate of the North Island, (2) Damp soils are the preferred and the South Island is much more habitat. Many distribution records mountainous (Cochrane 1973). suggest that the species occurs most Previously, the climates in the home frequently on damp ground in New ranges of potential invaders have been Zealand (Table 1). The preferred habitat used to predict the long-term potential seems to be damp soil within pasture of alien invasive species (‘climate and , but also red tussock matching’; Mack 1996; Hoffmann (Chionochloa rubra) wetland, Sphagnum 2001; Welk et al. 2002). However, the communities, subalpine bogs and 6 New Zealand Natural Sciences 29 (2004) MPN = Massey

Remarks 100 acres dominant Scenic Reserve L. (Abbreviations: AK = Auckland War stricta

MPN 28245, x 25m, present at least two 249614, BW Rainy Creek, old battery site, Nardus

Source/ID CHR 132306 Rare CHR 96166 Dense stand of approximately CHR 156705 CHR 472549 In open paddock CHR 250173 CHR 196618 CHR 82734 Edgar & Connor (2000), Light infestation in area 100m CHR 477738fruiting years,

Date 1962 1955 1964 1991 Prior 1926 WELT 1973 1968 1955 and CHR 92602 A and B, 1997 AK 1992 BW, 1955 1971 and Zotov, Hatton & C.C. Ogle

Observer J.R. Beggs & A.J. Healy

Habitat pasture C.D. Meurk Sheep pastureDune P.A. in clearing D. & G.C. Kelly ground P. Records (distribution and cultivated material) in New Zealand of invasive European matgrass Canterbury Canterbury North Westland Rahu Saddle Marlborough Plateau (Waimarino)

Code Location 7 Culverden, ? Thaine P. 8 North Canterbury ?Kay W.L. 9Valley, Lees Red tussock wetland and& Baird A. 10 Hills Lyttleton ?Armstrong J.B. 5 Between Reefton & Swampy sown pasture Hoskins F.E. 4 Reefton,6 Maruia On coarse gravel benchGardner R.O. 3 Denniston Old pack track, V.D. Distribution records 1 Raetihi, Volcanic Swampy pasture, dampBrown, A.G. 2 Renwicktown, Old native pasture Memorial Museum Herbarium; BW = BioWeb database of the Department Conservation; CHR = Landcare Research Herbarium, Lincoln; = BioWeb Memorial Museum Herbarium; BW Museum of New Zealand) Papa = Te University Herbarium; WELT Table 1. Table W.D. K ISSLING ET AL: Nardus stricta in New Zealand 7 voucher of the area Noticed in 1956 increasing. Molloy Own observationsOwn 2003: dominant on damp soil Own observationsOwn depressions within CHR 51508 andCHR 61911 Plant was grown at Botany Division, DSIR Glasshouse CHR 224701 Lincoln experimental garden CHR 225694CHR 206760 One patch only seen CHR 172530clump Isolated Own observations CHR 4117 CHR 132295 Forming mat and taking charge 1947 2002 B.P.J. 1963 1972 1970 1959 and2003112363, CHR BW 1966 and2003 CHR 156767,1966 BW 2003: dominant in wet 1999 and2003 CHR 542904 1931 1962 B.H. Macmillan Sphagnum damp soil, deep peat pers. comm. grassland places within tussockKissling W.D. Canterbury Alford Scenic Reserve Station, Lake PukakiMitchell A.R. Central OtagoHealy A.J. Southland Lake Pukaki grassland, subalpine bogKissling W.D. Pukaki Nenthorn Reserve grasslandKissling W.D. 19 Nightcaps, Southland ?Drummond B. 20 Chatham Island grazed by sheep, Paddock Molloy B.P.J. Cultivated material 21Valley, Lees Cultivated at Lincoln McCaskill L.W. 11 near Ashburton River, with Slope 12 Irishman Creek13 Ferintosh Station, Damp soil, west aspect depressions in tussock Wet B.H. Macmillan & Sieowright, H.M. 15 Becks, near St. Bathans, Pasture R.K. Dawin & 14 side of Lake West Wet depressions and dampKerr, T.G.C. 16 Macraes Flat, Damp soil within tussockFord, K.A. & Pearce J. 17 Belt, Dunedin Town ?McCaskill J.M. 18 Burwood Station, ?Gow P.P. 8 New Zealand Natural Sciences 29 (2004) ephemeral wetlands. In its native (Table 1, code 12-14). Now (in 2003), habitat, Tansley (1939) reported from Nardus often forms dense and extensive, the British Isles that ‘it [Nardus] occurs almost monospecific stands. The main in a great variety of habitats, whose habitats are wet depressions and damp common character seems to be a soil of soil within semi-natural tussock acid and damp but not permanently wet grasslands on lateral moraine including raw humus or peat, with stagnant or wet or seasonally ponded kettle nearly stagnant soil water’. Grime et al. depressions (Figure 3), edges of (1988) view Nardus as being ‘essentially tarns, ephemeral wetlands, seepages a dryland species which occasionally (Figure 3), subalpine bogs, and ditches extends into soligenous mire’, being, along road sides. Most sites are on however, ‘particularly abundant in areas pastoral land; however, Nardus has of high rainfall’. Thus, soil moisture recently invaded ephemeral wetlands seems to be very important, no matter on conservation land (Pukaki Scientific whether provided by rain or by the Reserve, managed by the Department hydrology of the habitat. of Conservation) and recruitment (3) Pastoralism and grazing seem to studies suggest that the species is be correlated with the occurrence of spreading (Kissling 2004). Nardus. Many distribution records suggest that pastoralism and grazing is associated with the occurrence of Nardus (Table 1), and grazing has been found to favour Nardus in its native habitat in Europe (Fenton 1936, 1937; Grant et al. 1996). The species is of low palatability (Thomas & Fairbairn 1956), and is avoided by grazing sheep (Fenton 1936, 1937; Grant et al. 1996). When grazed, Nardus increases in abundance at the expense of other species (Ellenberg 1996; Grant et al. 1996). Given the extent of sheep farming in New Zealand, Nardus may have the ideal conditions to further spread and increase in abundance and dominance. Situation at Lake Pukaki, South Canterbury Figure 3. Dense populations of Nardus stricta (light coloured in the centre) within tussock The current occurrence of Nardus was grassland (surrounding) on lateral moraine checked at the western side of Lake at approximately 900 m above sea level at Pukaki, South Canterbury (Kissling the western side of Lake Pukaki, Canterbury, New Zealand. Top: A seasonally ponded 2004). At this location, Nardus was first kettle depression invaded by Nardus stricta. noticed in 1956, and subsequently Bottom: A seepage completely covered by recorded in 1959, 1966 and 1970 Nardus stricta. (Photos: W.D. Kissling) W.D. K ISSLING ET AL: Nardus stricta in New Zealand 9

Spread and invasion potential Control The current spread rate of Nardus is not Currently, Nardus control methods are known. The situation along the western largely absent. No biological control site of Lake Pukaki suggests that Nardus agents exist, and herbicide treatments is expanding its range at least locally have been used to kill only individual (Kissling 2004). Many biological tussocks (Callihan & Miller 2003). invasions are characterised by a lag Whatever control method is chosen, phase, i.e. a time lag between the first attention should be given to possible establishment, and the beginning of side-effects on non-target organisms. spontaneous spread (Kowarik 1995). It would be desirable to know whether Conclusions Nardus has gone beyond its lag phase and has started to spread more widely. Environmental weeds are alien plant However, this could only be achieved species that threaten local native species by monitoring currently invaded sites. or ecosystem processes (Reid 1998). Due to the wide range of Due to its growth habit Nardus has the environmental conditions Nardus can ability to dominate extensive areas and tolerate (Chadwick 1960a; Kruijne to replace other plants, while the 1965), it is difficult to make any habitats invaded by Nardus in New predictions of its invasion potential. Zealand constitute ecosystems with Nardus is most likely to occur on acidic, high conservation value (Mark 1992; poor soils, and might be limited to wet Johnson & Jackson 1999; Johnson & depressions in regions with low mean Rogers 2002). Ecosystem processes, for annual precipitation (Chadwick instance the hydrological system of 1960a). It will probably be most seasonally ponded kettle depressions or invasive in open, low stature vegetation, ephemeral wetlands, could be altered or where grazing reduces the by Nardus invasion. Furthermore, the competitive ability of other plants. The species is a problem for pastoralism species could successfully invade due to its unpalatability to stock grasslands as reported from Europe and its low productivity. Based on (Fenton 1936, 1937; Chadwick 1960b; these arguments it is recommended Rawes 1961; Grant et al. 1996). that Nardus be regarded by relevant Furthermore, Nardus is potentially a management agencies (e.g. Department successful invader into alpine and of Conservation and Regional subalpine cushion plant communities Councils) as a potential environmental (Gibson & Kirkpatrick 1985), into weed in New Zealand. However, ephemeral wetlands with their turf and more information is needed on its sward vegetation (Johnson & Rogers distribution, establishment, spread and 2002), and into kettle hole wetlands impact in New Zealand. We would thus (Johnson 1994; Johnson & Jackson like to encourage all New Zealand 1999). 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