Christian Bay
To monitor the vegetational changes in Zackenbergdalen, 10 permanent plots were established in 2000 within each of the vegetation zones along a 6 km long tran- sect, the ZERO line, from the coast of Young Sund to the top of Aucellabjerg – i.e. a total of 1280 plots (Fredskild and Mo- gensen 1997, Caning and Rasch 2001). This work is expected to be carried out every 5th year to investigate the long term changes of the species composition and distribution of the plant communities along this landscape gradient.
The vegetation analyses were carried out during the two last weeks of July 2005 by Christian Bay assisted by Marie-Luise Øllgaard Meyhoff. Most of the markers of the permanent plots in the lowland and on the slope of Aucellabjerg up to 600 m a.s.l. were undisturbed. Frost action had dis- turbed some of the markers, but it was possible to re-establish them. On the other hand, most markers of the plots in the up- land were pushed out of the soil, which is
of a more coarse type, and it was not pos- sible to re-establish them in the original position. Consequently, most of the up- land plots above 600 m were abolished. The detailed vegetation analyses were car- ried out by using the frequency analysis method used five years ago (Caning and Rasch 2001). The species composition and frequency of the vascular plant species were recorded in the undisturbed plots of the 1280 permanent plots.
In all types of plant communities along the line except for salt marsh, an increase in number of species since 2000 was found. The number of species new to the plant communities varied from one to eight species with the largest increase in the plant community with high species di- versity – Salix arctica snowbed. Nearly all new species are perennials with a short life strategy. The only woody species new to a few plots was Salix herbacea, a species which indicates a prolonged snow cover. Only in a few analyses there was a de- crease in number of species. In the wet plant communities, the most frequent new species were Eriophorum scheuchzeri, Carex bigelowii, Saxifraga cernua and Juncus biglu- mis. In the moist plant communities, Poly- gonum viviparum, Festuca hyperborea, Pedic- ularis hirsuta and Luzula confusa were com- mon new species.
There were differences in the changes of frequency among the different life strate- gies. Woody dwarf shrubs (Cassiope tetra- gona, Vaccinium uliginosum ssp. microphyl- lum, Dryas sp. and Salix arctica) with a long term life strategy, showed no or only mi- nor changes in frequency, whereas the perennials both among herbs and grami-
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1 (0-50 m) 0.37 0.43 0.44 0.44 0.30 0.41 0.34 0.34 – 0.42 0.41 2 (0-50 m) 0.43 0.50 0.50 0.51 0.41 0.48 0.43 0.44 – 0.50 0.49 3 (50-150 m) 0.54 0.53 0.54 0.53 0.41 0.51 0.47 0.49 – 0.54 0.53 4 (150-300 m) 0.46 0.45 0.46 0.44 0.31 0.43 0.36 0.38 – 0.41 0.40 5 (300-600 m) 0.36 0.35 0.38 0.38 0.22 0.37 0.26 0.26 – 0.31 0.30 6 (50-150 m) 0.48 0.48 0.47 0.46 0.33 0.44 0.39 0.41 – 0.46 0.45 7 (150-300 m) 0.48 0.46 0.48 0.45 0.32 0.43 0.38 0.39 – 0.45 0.44 8 (300-600 m) 0.42 0.38 0.41 0.42 0.25 0.35 0.28 0.29 – 0.33 0.32 9 (0-50 m) 0.42 0.50 0.52 0.51 0.39 0.50 0.44 0.45 – 0.52 0.51 10 (50-150 m) 0.52 0.53 0.54 0.52 0.40 0.52 0.48 0.48 – 0.55 0.54 11 (150-300 m) 0.47 0.45 0.46 0.42 0.26 0.41 0.35 0.36 – 0.45 0.44 12 (300-600 m) 0.42 0.42 0.44 0.45 0.28 0.32 0.34 0.33 – 0.41 0.40 13 (Lemmings) 0.42 0.49 0.50 0.49 0.40 0.47 0.41 0.43 – 0.48 0.47 Total 0.45 0.46 0.48 0.47 0.32 0.43 0.38 0.38 – 0.45 0.44
Table 3.8. Mean NDVI values for 12 sections of the bird and musk ox monitoring areas in Zack- enbergdalen together with the lemming moni- toring area (part of sec- tion 2) based on Landsat TM, ETM+ and SPOT 4 HRV and ASTER satellite images 1998-2005 (see Fig. 4.1 in Caning and Rasch 2003 for position of sections). The data have been corrected for differ- ences in growth phe- nology between years to simulate the 31 July value. When comparing values, it should be noted that optimum of the plant communities varies between years with 31 July close to optimum of most years.
noids (i.e. grasses, sedges and rushes) showed many increases or decreases in frequency. In plots with major changes, up to 55% of the recordings from year 2000 have changed either by an increase or a decrease in frequency of the species.
In several of the plots, the plants had changed their reproductive status either by flowering or by having been sterile af- ter the flowering season five years ago.
It is expected that the border between Cassiope tetragona heath and Salix arctica snow bed is a good marker for changes of the distribution of the snow cover and changes in the duration of the snow free period. But there were no signs in 2005 of
changes in the distribution of these plant communities.
The disappearance within the last years of a large snow bank at an altitude of ap- proximately 600 m on the ZERO line is ex- pected to have a major impact on the vegetation below, because the early melt
1999 2000 2001 2002 2003 2005 early 2005 late
NDVI Date NDVI Date NDVI Date NDVI Date NDVI Date NDVI Date NDVI Date
Cassiope 1 0.40 29.7 0.41 29.7 0.37 5.8 0.35 29.7 0.36 5.8 0.34 9.7 0.30 22.7 Cassiope 2 0.41 29.7 0.46 22.7 0.38 22.7 0.38 26.8 0.43 5.8 0.37 9.7 0.39 22.7 Cassiope 3 0.41 19.8 0.36 19.8 0.33 5.8 0.31 26.8 0.34 12.8 0.30 9.7 0.34 29.7 Cassiope 4 0.38 26.8 0.41 22.7 0.35 29.7 0.33 26.8 0.39 5.8 0.34 9.7 0.39 29.7 Mean 0.40 0.41 0.36 0.34 0.38 0.34 0.36 Dryas 1 0.43 22.7 0.41 22.7 0.37 22.7 0.35 25.7 0.40 22.7 0.32 9.7 0.25 29.7 Dryas 2/Salix 7 0.39 19.8 0.42 22.7 0.39 29.7 0.43 5.8 0.42 5.8 0.36 9.7 0.37 22.7 Dryas 3 0.45 29.7 0.45 22.7 0.42 26.7 0.41 29.7 0.46 22.7 0.33 9.7 0.31 29.7 Dryas 4 0.34 19.8 0.32 22.7 0.33 22.7 0.28 29.7 0.29 22.7 0.25 9.7 0.29 29.7 Dryas 5 0.34 29.7 0.33 22.7 0.31 22.7 0.28 29.7 0.31 15.7 0.20 9.7 0.23 29.7 Dryas 6/Papaver 4 0.35 26.8 0.41 22.7 0.34 26.7 0.37 5.8 0.38 22.7 0.33 9.7 0.36 29.7 Mean 0.38 0.39 0.36 0.35 0.38 0.30 0.30 Papaver 1 0.41 19.8 0.41 22.7 0.38 29.7 0.39 29.7 0.41 22.7 0.35 9.7 0.37 22.9 Papaver 2/Salix 5 0.44 19.8 0.45 22.7 0.41 29.7 0.40 5.8 0.42 29.7 0.37 9.7 0.43 29.7 Papaver 3 0.37 26.8 0.41 22.7 0.35 29.7 0.34 5.8 0.39 22.7 0.33 9.7 0.39 29.7 Mean 0.39 0.42 0.37 0.37 0.40 0.345 0.3875 Salix 1 0.57 29.7 0.59 22.7 0.54 8.7 0.54 22.7 0.60 15.7 0.51 9.7 0.43 29.7 Salix 2 0.52 29.7 0.52 22.7 0.49 29.7 0.51 22.7 0.50 22.7 0.46 9.7 0.42 29.7 Salix 3 0.41 29.7 0.44 22.7 0.39 29.7 0.38 29.7 0.38 22.7 0.34 9.7 0.31 22.7 Salix 4 0.46 29.7 0.47 22.7 0.43 2.8 0.45 29.7 0.47 15.7 0.40 9.7 0.38 29.7 Salix 6 – – – – – – – – 0.39 31.7 0.33 9.7 0.43 29.7 Mean 0.46 0.48 0.44 0.45 0.46 0.396 0.396 Saxifraga/Silene 1 0.28 29.7 0.34 7.8 0.27 8.7 0.19 22.7 0.27 15.7 0.19 9.7 0.15 29.7 Saxifraga/Silene 2 0.36 29.7 0.38 22.7 0.34 19.7 0.31 22.7 0.38 15.7 0.34 9.7 0.27 15.7 Saxifraga/Silene 3 0.23 29.7 0.26 22.7 0.27 15.7 0.20 29.7 0.24 22.7 0.17 9.7 0.15 29.7 Silene 4 0.32 26.8 0.36 22.7 0.27 29.7 0.26 5.8 0.28 29.7 0.26 9.7 0.30 29.7 Mean 0.30 0.34 0.29 0.24 0.29 0.24 0.22 Eriophorum 1 0.57 5.8 0.60 14.7 0.60 29.7 0.57 29.7 0.61 15.7 – – 0.54 15.7 Eriophorum 2 0.58 29.7 0.58 22.7 0.53 26.7 0.50 29.7 0.45 15.7 0.44 9.7 0.44 15.7 Eriophorum 3 0.54 19.8 0.56 22.7 0.47 29.7 0.47 29.7 0.48 22.7 0.37 9.7 0.35 22.7 Eriophorum 4 0.73 5.8 0.72 22.7 0.68 29.7 0.64 5.8 0.67 22.7 – – 0.70 29.7 Mean 0.61 0.62 0.57 0.54 0.55 0.41 0.51 Mean of all 0.43 0.44 0.40 0.39 0.41 0.33 0.36
Table 3.9. Peak NDVI recorded in 26 flower plots 1999-2005 together with date of maximum record using a hand held Skye 110 instrument with a 660-730 nm sensor. NDVI values presented are transformed averages of eight (four in very small plots) hand held RVI measurements in each plot. Note that the greening measured accounts for the entire plant community, in which the taxon denoted may only make up a minor part. Mean of e.g. Salix plots also involve Salix plots 5 to 7. NOTE: In 2005 two peaks, a very early and a normal, are given. 2004 data is not included due to instru- mental error that season.
off of the snow bank will lead to reduced water supply to the vegetation during the later parts of growing season. However, the results of 2005 did not show any dis- tinct signs of floristical changes in the plant communities below the snow bank.
Monitoring of northern limit species
The reproduction of selected vascular plant species with their northern distribu- tion limit in the study area were checked in the plots established in 2000 (Caning and Rasch 2001). For almost all the species and in nearly all the plots there was a marked reduction in the number of flowers or inflorescences of plants grow- ing in moist, wet or dry soils. Campanula gieseckiana in dry south exposed habitats showed a marked decrease from 155 buds five years ago to none this year in the plot with the biggest decrease.
As the only species, the snowbed species Carex lachenalii showed a marked increase in numbers of inflorescens in all the plots.
A new northern limit species was in- cluded in the monitoring programme. A viable population of Pyrola grandiflora growing just south of the air strip in a dwarf shrub community was included. This site is at the northern distribution limit of the species (Bay 1992), and it is the only site in the study area, where the species has been found.