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Trampling Impacts on Thermotolerant Vegetation of Geothermal Areas in New Zealand

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Trampling Impacts on Thermotolerant Vegetation of Geothermal Areas in New Zealand
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           1 3 Environmental Management  ISSN 0364-152XVolume 52Number 6 Environmental Management (2013)52:1463-1473DOI 10.1007/s00267-013-0187-5 Trampling Impacts on Thermotolerant Vegetation of Geothermal Areas in NewZealand  Bruce R. Burns, Jonet Ward & TheresaM. Downs           1 3 Your article is protected by copyright and allrights are held exclusively by Springer Science+Business Media New York. This e-offprint isfor personal use only and shall not be self-archived in electronic repositories. If you wishto self-archive your article, please use theaccepted manuscript version for posting onyour own website. You may further depositthe accepted manuscript version in anyrepository, provided it is only made publiclyavailable 12 months after official publicationor later and provided acknowledgement isgiven to the srcinal source of publicationand a link is inserted to the published articleon Springer's website. The link must beaccompanied by the following text: "The finalpublication is available at link.springer.com”.  Trampling Impacts on Thermotolerant Vegetation of GeothermalAreas in New Zealand Bruce R. Burns  • Jonet Ward  • Theresa M. Downs Received: 14 September 2012/Accepted: 3 October 2013/Published online: 18 October 2013   Springer Science+Business Media New York 2013 Abstract  Geothermal features such as geysers, mudpools, sinter terraces, fumaroles, hot springs, and steamingground are natural attractions often visited by tourists.Visitation rates for such areas in the Taupo Volcanic Zoneof New Zealand are in the order of hundreds of thousandsannually. These areas are also habitat for rare and spe-cialized plant and microbial communities that live in thesteam-heated soils of unusual chemical composition. Weevaluated historical and current trampling impacts of tourists on the thermotolerant vegetation of the Waimanguand Waiotapu geothermal areas near Rotorua, and com-pared the results to experimental trampling at a third site(Taheke) not used by tourists. Historical tourism hasremoved vegetation and soil from around key features, andremaining subsoil is compacted into an impervious pave-ment on which vegetation recolonization is unlikely in theshort term. Social tracks made by tourists were present atboth tourist sites often leading them onto hotter soils thanconstructed tracks. Vegetation height and cover were loweron and adjacent to social tracks than further from them.Thermotolerant vegetation showed extremely low resis-tance to experimental trampling. This confirms and extendsprevious research that also shows that thallophytes andwoody shrubs, life forms that dominate in thermotolerantvegetation, are vulnerable to trampling damage. Preserva-tion of these vulnerable ecosystems must ensure that touristtraffic is confined to existing tracks or boardwalks, andactive restoration of impacted sites may be warranted. Keywords  Trampling impacts    Social tracks   Geothermal areas    Thermotolerant vegetation   Vulnerable plant communities Introduction The surface manifestations of geothermal upwellings areuncommon and increasingly rare phenomena worldwide,but are much valued landscape features including fortourism (Barrick  2010). The Taupo Volcanic Zone on the North Island of New Zealand has several remaining geo-thermal areas that are noted for their spectacular surfacefeatures (Kissling and Weir 2005; Cody 2007). Interesting geothermal features include mud pools, hot water springs,lakes and streams, fumaroles, sinter terraces, steamingground, and geysers. Not surprisingly, these naturalattractions have been the focus of tourism since the mid-1800 s (Hunt et al. 1994; Barrick  2007). Recent surveys of  tourist activity at New Zealand’s geothermal sites showthat geothermal areas are ranked as one of the main naturalattractions for international and domestic visitors (Ministryof Economic Development 2012). Luketina (2002, 2012) estimated that over 2 million tourists visited geothermalattractions in 2001, and that this visitation rate hadincreased by 10 % by 2012. B. R. BurnsLandcare Research, Private Bag 3127, Hamilton, New Zealand Present Address: B. R. Burns ( & )School of Biological Sciences, University of Auckland,Private Bag 92019, Auckland 1142, New Zealande-mail: b.burns@auckland.ac.nzJ. WardFaculty of Environment, Society and Design, LincolnUniversity, P.O. Box 84, Canterbury, New ZealandT. M. DownsCentre for Biodiversity and Ecology Research, University of Waikato, Private Bag 3105, Hamilton, New Zealand  1 3 Environmental Management (2013) 52:1463–1473DOI 10.1007/s00267-013-0187-5  As well as interesting surface geothermal features, thebiology of New Zealand’s geothermal areas is equallyfascinating yet not widely appreciated (Ecroyd 1982; Huser1991; Boothroyd 2009). Geothermal areas can provide an extremely hot, humid, and acidic environment which mostplants cannot tolerate. The species of plants that grow inand around these areas are often rare and some are endemicto these environments (Given 1980; Burns 1997). These ecosystems can also contain taxonomically distinctmicroorganisms of extremely ancient lineage, e.g., ther-mophilic archaebacteria (Potter 1997; Stott et al. 2008). Such ecosystems occur as an ‘archipelago’ of small patchestotaling approximately 1,000 ha in New Zealand (Burns1997; Wildland Consultants Ltd 2011). Geothermal features and ecosystems can be extremelysensitive to disturbance (Huser 1991; Luketina 2012). In New Zealand, some geothermal surface features and ther-motolerant vegetation have already been subject to sub-stantial degradation through human disturbance. Forexample, over 100 geysers in New Zealand have becomeextinct due to geothermal energy development (Barrick 2007), and there has been an approximately 30 % loss of thermotolerant vegetation area ‘‘from the time of Europeansettlement’’ (Wildland Consultants Ltd 2011). However,quantitative assessments of the impacts of tourism ongeothermal sites in New Zealand are rare (Ward et al.2000).Tourists mostly visit commercially operated geothermalareas, and walk from one feature to another using a mapprovided by the operators. The maps guide them alongformed tracks which often bisect heated ground covered bythermotolerant vegetation. However, visitors move off-track to gain different views of particular features or toexplore. Walking off these tracks damages thermotolerantvegetation and soils by breaking branches, killing plants,disturbing and compacting soils, and breaking up sintercrusts. Tourist damage of geothermal ecosystems has beenbroadly recognized in Japan (Glime and Iwatsuki 1997),Turkey (Simsek et al. 2000), and in New Zealand (Given 1976; Ecroyd 1982; McMillan 1982; Huser 1991; Luketina 2002; 2012), although the extent, impact, or the relative vulnerability of geothermal ecosystems to trampling islargely unknown.Pedestrian trampling impacts on natural plant commu-nities have been studied in an increasingly wide range of ecosystems (e.g., Weaver and Dale 1978; Bayfield 1979; Sun and Liddle 1993; Andersen 1995; Cole 1995; Whinam and Chilcott 1999; Kutiel et al. 2000; Gallet and Roze ´2001; Monz 2002; Hill and Pickering 2009; Pickering and Growcock  2009). Plant communities range in their sensi-tivity to impact, from those that require relatively longreestablishment times after trampling impacts (e.g., alpinemeadows, Bell and Bliss 1973), to those that recoverquickly (e.g., stabilized coastal sand dune communities,Kutiel et al. 2000). Research has allowed land managers to better reconcile the dilemma of meeting the public’s desirefor increasingly intensive recreational use of areas, whilepreserving off-track natural communities (Cole 1995). A deficiency of information regarding the ecological impactsof visitors to geothermal sites in New Zealand has beenidentified by several management agencies (PCE 1997).For example, the Department of Conservation and itspredecessors in New Zealand have repeatedly expressedconcern over the impacts of visitors to geothermal sites,especially those where rare and unique thermotolerantvegetation grows (McMillan 1982; C. Jenkins pers.comm.).The aims of our study were to determine vegetationchanges over time in relation to site tourist history;examine the nature and extent of current unmanagedpedestrian impacts on vegetation; and assess the relativesensitivity of thermotolerant vegetation to trampling. Thiswas done at two geothermal areas with high numbers of tourists and one not visited by tourists. Study Areas The study was conducted at two commercially operatedgeothermal areas near Rotorua; Waimangu and Waiotapu,and a control site not visited by tourists at Taheke (Fig. 1).The commercial sites were chosen because of the presenceat each of thermotolerant vegetation, their commercialmanagement regimes, and their popularity as tourist des-tinations. However, the managers of these sites would notallow us to impose trampling treatments on undisturbedthermotolerant vegetation at either site, so this was carriedout on highly similar vegetation at the non-tourist Tahekesite, where permission was granted to carry out such anexperiment (Fig. 1).Waimangu (www.waimangu.co.nz) occupies a valleysouthwest of Lake Rotomahana (Seward and Sheppard1986; Scott 1992; Houghton and Scott 2002). The Lake formed as a result of the eruption of Mount Tarawera in1886 (Simmons et al. 1993) which destroyed the celebratedPink and White Terraces (Hunt et al. 1994; Maxwell 2009) and opened a fissure allowing escape of hot geothermalreservoir water to the surface. The resulting hot springs andother features attract visitors to Waimangu today (Huntet al. 1994). All vegetation in the area was restarted in 1886(Ward et al. 2000; Fitzgerald and Smale 2010). Maintained tracks lead tourists down the valley past a series of lakesthat fill former hydrothermal eruption craters, and alongstreams draining those lakes. The tracks traverse areas of thermotolerant vegetation close to the lake and streamedges. The thermotolerant vegetation associated with 1464 Environmental Management (2013) 52:1463–1473  1 3  Waimangu’s geothermal features occupies approximately51 ha (Fitzgerald and Smale 2010). Tourists have fre-quented these tracks since the late nineteenth century(Ward et al. 2000). One of the earliest attractions was theWaimangu Geyser, which was active between 1900 and1904 (Seward and Sheppard 1986). At that time it was theworld’s largest known geyser. Today, visitor numbers atWaimangu are measured in the tens of thousands per year(H. James pers. comm.).Waimangu has the largest number of geothermallyassociated plant species of any single location in NewZealand (Fitzgerald and Smale 2010). Particularly notableis the diversity of unusual ferns and fern allies. On heatedground, thermal vegetation is mostly shrubland dominatedby a 1- to 2-m-tall dense canopy of   Kunzea ericoides  var. microflora , with occasional  Leucopogon fasciculatus  and  Dracophyllum subulatum , over a dense bryophyte turf groundcover. Common mosses and liverworts forming thisturf are  Campylopus pyriformis ,  C. introflexus, Isoptery-gium minutirameum, Lepidozia glaucophylla , and  Chi-loscyphus semiteres . Around hot lakes, springs, andstreams, populations of several thermal ferns occur, e.g., Christella dentata ,  Cyclosorus interruptus, Hypolepisdicksonioides,  and  Nephrolepis flexuosa . The occurrencesof these species are notable here as their main centers of distribution are in subtropical or tropical climates, either innorthern New Zealand or in the tropical Pacific. Otherunusual geothermally associated ferns or fern allies whichoccur at Waimangu are the living fossil  Psilotum nudum ,  Lycopodiella cernua, Dicranopteris linearis , and  Cheilan-thes sieberi  ssp.  sieberi . Of these species,  Christella den-tata ,  C. interruptus  and  N. flexuosa  are listed as ‘declining’,and  D. linearis, H. dicksonioides , and  K. ericoides  var. microflora  are listed as ‘naturally uncommon’ in the cur-rent list of threatened and uncommon plants of NewZealand (de Lange et al. 2009).A central area of approximately 40 ha of the WaiotapuGeothermal Field located between Rotorua and Taupo wasspecifically developed for tourists (www.waiotapu.co.nz)(Hedenquist 1986; Hunt et al. 1994). At this site, tourists walk past a zone of steaming craters, sulfur deposits, alarge sinter terrace and Champagne Pool. Champagne Poolis a hot pool with a sinter rim occupying a hydrothermaleruption crater, and gains its name from the effervescenceof carbon dioxide through its waters. The development of the pool’s silica deposits and the composition of itsmicrobial community have been the subject of recentstudies (Jones and Renaut 2003; Ellis et al. 2005; Hetzer et al. 2007). Past the sinter terrace (named Artist’s Palette),tracks lead through a series of narrow canyons with colored Fig. 1  Location of study sitesnear the town of Rotorua, NewZealandEnvironmental Management (2013) 52:1463–1473 1465  1 3
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