Download Long-term human impact on Alpine Tundra - 25 years of

SouthͲEasternEuropeanJournal
ofEarthObservationandGeomatics
Issue
Vo3,No2S,2014
LongͲtermhumanimpactonAlpineTundraͲ25yearsofchanges
assessedbyaerialphotography
JanaMüllerová*,MichaelaVítková
InstituteofBotany,AcademyofSciencesoftheCzechRepublic,Prƽhonice,Czech
Republic
*Correspondingauthor:[email protected]
Abstract:InourstudyweassessedthelongͲtermeffectsofalkalinegravelusedfortrail
stabilizationuponadjacentalpinetundravegetationonnutrientpoorsubͲalpineplateau
ofKrkonošeMtsNationalPark,CzechRepublic,usingaseriesofaerialMSS(1986,1989,
1997)andCIRimagery(2012),GPSmapping,andrepeatedsoilandvegetationsurveys.
Aerial imagery was analyzed using both pixel and objectͲbased approach. During the
studyperiodof25years,theareaofroadsidevegetationmorethendoubled,showing
high rate of spread. In terrain depressions leading down the slope from alkaline
stabilized roads it formed extensive lobes reflecting the nature of the terrain and
reaching far into undisturbed vegetation (up to 156m). The spread of roadside
vegetationwasspatiallyexaminedtodetermineitsdrivingforces,andwasfoundtobe
significantly related to the type of the stabilizing material and the position relative to
theroad(slopeposition,distancefromtheroad),indicatingtheeffectofrunoffwater.
The latest imagery of 2012 documented reconstruction of trails (started in 2005). The
conservation measure stopped the ecosystem alteration although the damage during
reconstruction was extensive and ability of arcticͲalpine tundra to recover in the
extremeclimaticconditionsveryslow.Longertimelagisthereforeneededtorecordthe
recoveryprocess.
Keywords: CIR Aerial Imagery, Change Detection, EnvironmentalMonitoring, Historical
Analysis,RemoteSensing,RoadDisturbances,VegetationChanges.
1.
Introduction
Roads represent an important landscape element affecting both biotic and abiotic
components. Disruption of the chemical environment (alteration of chemical soil
properties) along roads affects plant growth and species diversity and composition
(Cape et al., 2004). The impact is especially profound if alkaline gravel is used in
predominantlynutrientͲpoorenvironmentdominatedbystresstolerantplants(Hilland
Pickering,2006).Suchprocessesfacilitatecolonizationbymorecompetitive,oftennonͲ
nativespecieswithgreaternutrientuptakeefficiencyandhigherbiomass(Dulièreetal.,
1999).Thealpinetundrarepresentsanextremelyfragileecosystemsensitivetohuman
disturbances. In such nutrient poor environment, adding nutrients (alteration of soil
propertiesalongroads)isassumedtohaveverystrongimpactonvegetationstructure.
483
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PublishedonlineMay2014
SouthͲEasternEuropeanJournal
ofEarthObservationandGeomatics
1986
Issue
Vo3,No2S,2014
1989
1997
2012
Figure1.TheeffectofalkalineroadͲstabilizingmaterialontundravegetationtracedfromMSSandCIR
aerialimageryinKrkonošeMts.,CzechRepublic.
2.
Methodology
OurstudyissituatedintheKrkonošeMtsNationalParkandBiosphereReserve(Figure
1),thehighestmountainrangeintheCzechRepublic.Uppermostareassituatedabove
the timberline are covered by a particular ecosystem called "alpine" or "arcticͲalpine
tundra",displayingaffinitiestobothsubͲarcticandhighͲmountainregions(Gordonetal.
2002), and hosting many endemic, glacial relic and rare species, and unique
geomorphologiccomponents(Štursa1998).DespitetheN.P.status,in1970'sto1980's
many paths and roads were stabilized to prevent erosion using unsuitable alkaline
material.Inthisacidicenvironment,suchmeasuremarkedlyalteredbothsoilproperties
andvegetationstructurealongsuchtrails.Whereasnormaltundravegetationisformed
by short thin grasses and sessile herbs, along trails paved with alkaline nutrients, the
native flora was replaced by mesoͲ to nitrophilous species and species of manͲmade
habitats, mostly herbs with broader leaves and comparable higher biomass. This
enabledtorecognizetheroadͲalteredvegetationonremotelysensedimagery.
RoadͲrelated changes were reconstructed using a series of multispectral (1986, 1989,
1997) and CIR aerial imagery (2012), GPS mapping, and repeated soil and vegetation
surveys.Theroadsidevegetationcouldbetracedonthemultispectraldatabecauseitis
484
®AristotleUniversityofThessaloniki,Greece
PublishedonlineMay2014
SouthͲEasternEuropeanJournal
ofEarthObservationandGeomatics
Issue
Vo3,No2S,2014
muchtaller,hasbroaderleavesandproducesahigherbiomasscomparedtothenatural
vegetation (Figure 2). It was classified using both pixel based (parallelepiped
classification Ͳ nonͲparametric supervised method defining the lowest and the highest
values of classes in every spectral band; for details see Müllerová 2004), and objectͲ
based approach (a combination of automated hierarchical, iterative, and ruledͲbased
classification). Seven permanent transects following the slope and perpendicular to a
road/trail were selected randomly to analyze the effects of different road/trail
constructionmaterialonvegetationcomposition(iny.2000and2004)andsoilphysicalͲ
chemicalproperties(iny.1998,2000and2001;fordetailsseeMüllerováetal.2011).
a)
c)
b)
d)
Figure2.RoadͲalteredvegetationon:a)MSSimagery(histogramequalized,roadͲalteredvegetationin
violet),andb)CIRimagery(roadͲalteredvegetationinred).Bottompictures(bandd)showOBIA
classificationresults.
3.
Results
Both pixel and objectͲbased image classifications enabled successfully analyze roadͲ
related vegetation changes. Vegetation along roads paved with alkaline material grew
considerablyfrom2.5%ofthestudysubsetin1986upto4.1%in2012(Figure1).Both
soil and vegetation changes depended significantly on the type of the rodͲstabilizing
materialandpositionrelativetotheslope(Müllerováetal.2011).Interraindepressions
leading down the slope from alkaline stabilized roads the roadside vegetation formed
lobesreflectingthenatureoftheterrainandreachingfarintoundisturbedvegetation,
providingevidenceoftheroleofwatererosion.Alongalkalineroads,soilpHincreased
from3.9upto7.6,basesaturationfrom9Ͳ30%upto100%,andlocalstressͲtolerant
lowcompetitivetundraspeciesdisappeared(includingrareandprotectedspecies),and
were replaced by mesoͲ to nitrophilous species and species preferring manͲmade
habitats.
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SouthͲEasternEuropeanJournal
ofEarthObservationandGeomatics
Issue
Vo3,No2S,2014
Based on increase between years 1886/97 measured by Müllerová et al. (2011),
roadsidevegetationwasestimatedtocoverover7%in2012.Thispredictionwasnot
metandtundraecosystemalterationsloweddownthankstotheconservationmeasures
undertakenbyNPAuthoritiessince2004.Alkalineroadmaterialwasremovedandtrails
stabilized using local building material. Today, most of the trails are reconstructed
exceptfromtheasphaltroadbuiltwiththicklayerofdolomiteandmelaphyre.During
the reconstruction, roadsides (ca 2 meters wide) were often disturbed and cleared of
vegetation. From the latest imagery, we could document the process of vegetation
recovery,althoughitwasnotthereforealwayspossibletodistinguishfromtheimagery
whethervegetationalongroadsisdamagedbythereconstructionorreturnstonatural
compositionoflowcoverandbiomass.
4.
Conclusions
Aerial imagery proved to be a good source of information on roadͲrelated changes in
tundra vegetation, mainly thanks to its different size and biomass compared to native
flora.Itwasevenpossibletosomeextendtodocumentthereconstructionofthetrails.
Althoughtheappliedcontrolmeasureslimitexpansionofundesirablevegetation,they
represent a serious disturbance in this fragile arcticͲalpine tundra ecosystem with
limited ability to recover in the extreme climatic conditions, and future studies are
thereforeneededtoassesstheprocessofecosystemrestorationinlongertimespan.
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®AristotleUniversityofThessaloniki,Greece
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ofEarthObservationandGeomatics
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