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http://hdl.handle.net/2282/952
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| Title: | En kvantitativ undersøkelse av ulike miljøfaktorer, i oligotrof fjellvegetasjon, med fokus på effekten av snødekket |
| Authors: | Munkejord, Hans Kristian |
| Issue Date: | 2005 |
| Abstract: | The approach to the problem presented in this research study has been to investigate
the response of alpine plants to varying depths of snow-covering and duration of the
snow cover as well as point out different environmental gradients in oligotrof alpine
vegetation. The research was carried out in the Kjelatind area, just south of Haukeliseter, in the
Vest-Telemark County of Norway. The investigation area is situated in the slightly oceanic section (O1) and includes vegetation zones ranging from northern boreal to
middle alpine. In the normal period (1961-1990) Haukeliseter snow-clearance station had an annual
precipitation of 840 mm and an average annual temperature of 0.4ºC. The
predominant wind direction is west-east and the investigation area lies on the
watershed between West-Norway and East-Norway. The sampling was stratified to cover most types of oligotrof vegetation in the
investigation area. The permanent quadrates also covered the gradient from ridge to
late snow patch over different expositions, slopes and heights. Totally, 82 samples
were investigated, each covering a total area of 4 square metres. The data material was analysed by use of numerical methods (DCA, CCA, GLM). The
program package CANOCO and CANODRAW was used to carry out this analysis. Snow- and soil-temperature data was collected weekly from 27 March – 17 June 2004.
Based on these data, snow melting- and soil temperature-graphs were created to
interpolate which days the quadrates were free of snow (S=0) and which days the soil
temperatures exceeded 6ºC (T>6). Within the 82 quadrates, 90 different vascular plants, 60 bryophytes (mosstaxa) and 21
lichens (lichentaxa) were found. The pattern in the snow melting- and soil temperature-graphs was distinctly correlated
with temperature- and precipitation-data from the two nearby climate stations
Midtlæger and Vågsli. Compared with the normal of 1961-1990 the snow melting
started three weeks anterior in the low alpine zone, while it was equal to normal in the
middle alpine zone. Early snow-bare ridges showed a slow increase in soil temperature, while quadrates
lying sheltered or patched with snow had a rapid increase of soil temperature. In some
cases, the soil temperatures of the snow patches were measured to over 6°C only a few
cm from the edge of the snow. Ridges with a thin snow cover and a higher likelihood
of ground frost were, still, significantly earlier free of snow (S=0, p=0.005) and
reached a soil temperature higher than 6°C (T>6, p=0.0262) before the snow patched
ground that had been protected by its cover of snow. The species-dataset was divided into 5 main groups using the TWINSPAN data
program. DCA axis no. 1 was correlated with a complex snow-gradient, while DCA axis no. 2
was correlated to the complex gradient altitude level. The sample-scores’ frequencydistribution
(i.e. number of species) was slightly discontinuous along DCA axis no. 1,
while the samples were more continuously distributed along DCA axis no. 2. Of the 15 environmental variables used in the statistical analyses, as many as 14 were
significant (p<0.05) according to the Monte Carlo Permutation test. The 15
environmental variables had an explanatory value of 35% of the variation of the data
set.
By the use of the GLM together with attribute plots, indicator values for snow were
proposed based on the species’ response to the environmental variable S=0. Unmodal
species were divided based on "the optimum snow free day", while species with a
linear response were divided on the basis of the regression coefficient β0 and β1. An
indicator value 1 (F1), F2, F8 and F9 was given to species with a linear response to
S=0. Species with F1 did not occur in this investigation, F2 had a β0<40 and a β1<-25,
F8 had β0>-100 and a β1<70, and F9 had a β0<-100 and a β1>70. The unmodal species
were given values F3, F4, F5, F6 and F7, and were divided on the basis of "the
optimum snow free day": F3 ≤ day 110 < F4 ≤ day 126 < F5 ≤ day 140 < F6 ≤ day
159 < F7. The "day" which divides the indicator values F3-F7 is relative, because the
basis for distinguishing that "day" is the snow-melting pattern of the spring 2004.
Maximum snow depth (Smaks) was the variable of the GLM which gave the most
significant (p<0.05) species of all three snow variables: Smaks, S=0 and T>6.
pH seems to be a good indicator for the complex snow-gradient, for oligotrophic
vegetation types, because this variable had the highest correlation to the DCA axis no.
1 (r=0.83, p<0.001) as well as to the snow variables S=0 (r=0.74, p<0.001) and Smaks
(r=0.70, p<0.001) |
| Keywords: | Snødekke
Fjellvegetasjon
Miljøvariabler |
| Document type: | Master's thesis |
| URI: | http://hdl.handle.net/2282/952 |
| Appears in Collections: | Mastergradsavhandlinger i natur-, helse- og miljøvern
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