Individual study: Six sown grass species commonly used in tundra revegetation fail to establish but cotton-grass Eriophorum vaginatum and stiff sedge Carex bigelowii naturally colonize exposed ground, Eagle Creek, Alaska, USA
Chapin III S.S. & Chapin M.C. (1980) Revegetation of an Arctic disturbed site by native tundra species. Journal of Applied Ecology, 17, 449-456
Increased human activity in Arctic tundra regions has led to environmental problems, including vegetation loss and subsequent erosion. Reseeding of disturbed sites with northern varieties of commercial grasses may reduce erosion but in most cases has not lead to permanent cover without repeated fertilizer application. In this study, conducted at Eagle Creek in Alaska (65º10’ N) in a tundra community dominated by Eriophorum vaginatum spissum, the effectiveness of sowing six northern varieties of grasses commonly used in tundra revegetationwas trialled.
Experimental design: In mid-June 1970 a 20 x 50 m area was bulldozed free of vegetation, leaving the underlying 10-20 cm thick organic layer. Seed of six grasses commonly used in tundra revegetation (reed canary-grass Phalaris arundinacea, smooth meadow-grass Poa pratensis, perennial rye-grass Lolium perenne, red fescue Festuca rubra, timothy Phleum pratense and meadow foxtail Alopecurus pratensis) were sown: without fertilizer; with a high-nitrogen fertilizer (at 444 kg/ha); or with a high-phosphorus fertilizer (444 kg/ha).
Plots (each 2.3 m²) were arranged in randomized blocks replicated five times. Vegetation was monitored for 10 growing seasons (August 1970, 1972 and 1974, and July 1979). Grass shoot densities recorded in 20, 0.1 m² quadrats per treatment. Total vegetation cover and cover of E.vaginatum and stiff sedge Carex bigelowii (two common native graminoids), grasses and mosses were estimated in 1972, 1974 and 1979. Above-ground vascular biomass was clipped from 0.04 m² quadrats at ground level in early August 1976 and separated into live and dead material (dried and weighed).
Grass seed germination percentage was determined 15 days after sowing on five 20-seed replicates planted on the disturbed soil at the time the plots were seeded. Expected seedling density for each species could therefore be calculated.
All sown grasses established in the first growing season, with densities at the end of the year 24-81% of that predicted, indicating substantial seedling mortality. Fertilizer application did not significantly enhance seedling density, and vegetation cover was around 20-40% in all except unseeded plots (less cover).
After three growing seasons, grass shoot density had declined to 1-30% of the initial density in unfertilized plots, but less so in fertilized plots. Only F.rubra had high densities after three years. Total cover (primarily E.vaginatum and C.bigelowii) was as low or lower in the third year (20-40% cover) in unfertilized plots.
After five years, the grasses had disappeared except in one unfertilized plot sown with F.rubra. Naturally colonizing Calamagrostis canadensis was the only other grass present. However, vegetation cover increased to 50-100% primarily through vegetative spread of cotton-grass and sedges. Fertilization enhanced cover, particularly of mosses (mostly Polytrichum spp.).
After seven growing seasons, above-ground vascular standing crop of both fertilized and unfertilized plots was similar to that of the undisturbed tundra. The disturbed site was vegetated almost entirely by E.vaginatum and C.bigelowii, and cover had increased to 50-100%. Fertilization increased vegetation cover, particularly of mosses (again mostly Polytrichum). After 10 growing seasons vegetation cover was 100% in all plots and was composed entirely of native species. The area was dominated by E.vaginatum (88% cover) and C.bigelowii (11%).
Conclusions: Sown grasses initially established fairly well in the first growing season, but then declined and had virtually disappeared after 5 years. Fertilizer application did not enhance their long-term survival but did increase shoot density of naturally colonizing native species. After seven growing seasons the site was vegetated almost entirely by E.vaginatum and C.bigelowii.
Note: The compilation and addition of this summary was funded by the Journal of Applied Ecology (BES). If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://links.jstor.org/sici?sici=0021-8901%28198008%2917%3A2%3C449%3AROAADS%3E2.0.CO%3B2-R