Long-term effects of reclamation treatments on plant succession at Gunnarsholt, southern Iceland
Published source details
Gretarsdottir J., Aradottir A.L., Vandvik A.L., Heegaard E. & Birks H.J.B. (2004) Long-term effects of reclamation treatments on plant succession in Iceland. Restoration Ecology, 12, 268-278
Published source details Gretarsdottir J., Aradottir A.L., Vandvik A.L., Heegaard E. & Birks H.J.B. (2004) Long-term effects of reclamation treatments on plant succession in Iceland. Restoration Ecology, 12, 268-278
In Iceland, anthropogenic activities in conjunction with highly erodible soils and a harsh climate have combined to cause extensive vegetation degradation and soil erosion over hundreds of years. The long-term effects (20–45 years) of revegetation reclamation treatments were examined at two localities in Iceland that were fertilized and seeded from 1954 to 1979 with perennial or annual grasses, or left untreated. Here, the effects of restoration attempts at Gunnarsholt in south Iceland are summarised.
Site description: Gunnarsholt is located in south Iceland (elevation 50–60 m). The area was probably covered by birch Betula woodland and willow Salix scrub at the time of human settlement (AD 874) but were fully eroded long before the onset of reclamation.
Reclamation treatments: Reclamation started about 70–80 years ago by fencing areas to exclude livestock (the site has been ungrazed since 1950) and later by sowing grasses and fertilizer addition. The reclamation treatments were grass sowing (with two perennials: red fescue Festuca rubra and timothy Phleum pratense; and four annuals: wild oat Avena sativa, barley Hordeum vulgare and Italian rye-grass Lolium multiflorum) and fertilization from 1954 to 1979.
Sections of the reclamation areas had not been treated, providing the opportunity to compare vegetation in treated and untreated areas.
Data collection: In 1999, five 10 × 10 m plots were laid out in each of the five reclamation treatments and control area. Within each plot, 10, 0.5 × 0.5 m quadrats were randomly placed and percent cover of vascular plant species and total plant cover, bare ground, bryophytes, lichens, biological soil crust and litter were visually estimated. The thickness of the bryophyte and litter layer was measured at 25 points in each quadrat. Soil samples were taken to assess soil pH, soil organic carbon content and total nitrogen content.
Plant cover: Total plant cover was significantly higher in treated areas than control plots. Average species richness per 0.25 m² quadrat was similar between treated and untreated areas. Species composition in treated areas was significantly different from the composition in control plots.
The flora of the control plots was characterized by perennial low-growing herbs and grasses. Shrubs and trees (willows Salix spp. and downy birch Betula pubescens) were absent in control plots. The vegetation in treated areas was characterized by dwarf-shrubs, grasses, shrubs, and a high bryophyte cover, the bryophyte layer on average 7.8 cm thick, and no woody plants were found. The sown perennial grasses (red fescue and timothy) had very low cover: red fescue (control 1%; treatment 0.8%); timothy control 0%; treatment 1.4%) The seeded annual species wild oat, barley and Italian rye-grass were absent.
Soil carbon, nitrogen and pH: Organic carbon (0.7%) and percentage total nitrogen (0.05%) were very low in the control plots, whilst treated areas were 2- to 3-fold higher; carbon (1.2-1.9%) and nitrogen (0.09-0.18%). Soil pH was considerably lower in treated areas (5.6-6) than in control plots (6.6).
The reclamation treatment area had significantly higher total plant cover (71–100%) than the control plots (5%) and floristic composition was usually significantly different between treated and control plots. Dwarf-shrubs (heather Calluna vulgaris and crowberry Empetrum nigrum), bryophytes, biological soil crust, grasses characterized the vegetation in the treated plots, but low-growing herbs that have negligible effects on the environment, such as northern rock-cress Cardaminopsis petraea and mountain sandwort Minuartia rubella, and grasses characterized the control plots. Seeded perennial grass species declined (<1%), annual grassess died out completely but acted as nurse species facilitating native plant colonization.
Conclusions: The authors consider that by seeding and fertilizer additon, some factors that limit plant colonization were overcome. Soil nutrients, vegetation cover, litter and biological soil crust were greater in the treated areas than the controls. This may have enhanced colonization through increases in soil stability, fertility and moisture, increased availability of suitable microsites and the capture of wind-blown seeds.
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