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2030Statisticalanalysis
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ventitiousinacommunity,withnorelationshipwithit0Theyoccurredvery
rarelyandhadlowbiomass0
Constancyofspeciesoccurrence(CI)inacommunityistheratiobetween
thenumberofsamplesofthisspecies(N
a)andthetotalnumberofsamplesin
thecommunity(N;Dengleretal02009),computedaccordingtotheformula:
CI=N
a/N•100%.Basedonthesecalculations,5classesofspeciesconstancy
weredistinguished:I0veryhigh(>75%),II0high(50–75%),III0average(25–
50%),IV
0low(5–25%)andV
0verylow(<5%)0
Speciesdominance(DI)inacommunityorsamplewascalculatedaccord-
ingtotheformula:DI
i=n
i/N•100%,whereDI
i–dominanceindexofspecies
i,n
i–itsbiomass,N–totalbiomassofspecies(Kasprzak,Niedbała1981)0On
thebasisoftheDIindex,5classesofspeciesdominanceinacommunitywere
distinguished:1–eudominant(>30%ofbiomass),2–dominant(20–30%),3–
subdominant(10–20%),4–recedent(5–10%)and5–subrecedent(<5%)0The
importanceindexofspecies(II)includesthevaluesofCIandDI(Kasprzak,
Niedbała1981),accordingtotheformula:II=√(CI•DI)0Thefollowingscale
ofspeciesimportanceinacommunitywasadopted:verylow(I
1<5%),low
(I
2=5–10%),average(I
3=10–15%),high(I
4=15–30%),veryhigh(I
5>30%)0
Moreover,thefrequenciesofemergentspecies,vascularplants,stone-
wortsandmosseswerecalculatedforeachcommunity,aswellasthefre-
quencyofone-,two-,three-,…n-speciespatches0Thefrequencyofspecies
assemblagesforthespecieswithCI>5%wasalsocalculated0Onlytheas-
semblageswithF>1%wereconsideredintheanalysisofthecommunities0
Thestructureofselectedcommunitiesandtheirenvironmentalcondi-
tionswerecomparedbythenon-parametricKruskala-Wallistestwithpost−
hocDunn’stest(STATISTICA12)0Thistestisnotlimitedbythenormalityof
comparedfeatures,orthehomogeneityofvarianceinthegroups0Compari-
sonsofparticipationofvascularplants,stonewortsandmossesinthecom-
munities,aswellasthefrequencyofone-,two-,three-,…n-speciespatches,
thefrequencyofspeciesassemblagesandthestructureofconstancy,domi-
nanceandimportanceofspeciesinthecommunitieswereanalysedbythe
Chisquaretest(PopTools-MicrosoftExcel)0Theconsideredsignificancelevels
wereasfollows:p<0005;p<0001andp<000010
Theimportanceofenvironmentalfactorsresponsibleforspeciesdiversity
wasdeterminedusing10692sampleswith122plantspeciesand4650envi-
ronmentalsamples,including2325sedimentsamplesand2325above-sedi-
mentwatersamples0Thesampleswerecollectedfrom775depthzonesof161
lakes0Itwasassumedthatforevery10–20plantsamplesinthegivendepth
zoneenvironmentalconditionsareequal,sothattheywerecharacterisedby
themeanof3samplesofwaterand3sedimentsamplesfromthisdepthzone0
