Appendix 1.Electronic supplementary material.A brief description of the methods used to sample the six (Helsinki) and three (Edmonton) vegetation and environmental variables (see Table 1). For more detailed descriptions of these variables, see Isaksson 2004 (for Edmonton) and Hamberg et al. 2008 and Malmivaara-Lämsä et al. 2008 (for Helsinki).
Helsinki
Canopy cover (%) was visually estimated above each understorey vegetation plot. Pitfall traps were placed along the edge of these vegetation plots.
Vegetation cover (%) was visually estimated within 0.5 x 1 m understorey vegetation plots at a scale of 0.1, 1, 2, 3, 4, 5, 10, 15, 20, ..., 100%. Tree and bush seedlings < 30 cm in height were included in this.
Litter cover (%)was visually estimated within each understorey vegetation plot with the same scale as above.
Broadleaf trees (%). The diameter of all trees over 5 cm diameter at breast height was measured in 50 m2 circular plots around each understorey vegetation plot. Percentage broadleaf trees were calculated from these data.
Soil moisture (%) and pH. Six humus layer subsamples were collected from each understorey vegetation plot, and were pooled to form a composite sample for each sampling location. Moisture content per sample was determined by oven drying 2 g (fresh weight) of humus overnight at 105oC. pHH2O was determined according to the methods of Tamminen and Starr (1990).
Edmonton
Canopy cover (%). A convex spherical densiometer was used to measure the canopy cover at every understorey vegetation plot. Two estimates were made, one facing north and one facing south and the two were averaged.
Vegetation cover (%).Vegetation was inventoried using 0.5 m2 plots placed within a few cm from each pitfall trap. The percent cover of each plant species was visually estimated and assigned to one of seven categories per plot: (1) < 1% cover, (2) 1-3%, (3) 4-10%, (4) 11-25%, (5) 26-50%, (6) 51-75% and (7) 76-100%. Average percent cover per plot per species was used in the analysis instead of these categories.
Bare ground (%).Ground cover was estimated in a similar way to Canopy cover (%) above.
References
Hamberg L, Lehvävirta S, Malmivaara-Lämsä M, Rita H, Kotze DJ (2008) The effects of habitat edges and trampling on understorey vegetation in urban forests in Helsinki, Finland. ApplVegSci 11:81-96
Isaksson W (2004) The effects of edges and trampling intensity on vegetation in urban forests east of Edmonton in Alberta, Canada. Honours Thesis. Department of Renewable Resources, University of Alberta. Edmonton, Alberta, Canada, pp. 84
Malmivaara-Lämsä M, Hamberg L, Haapamäki E, Liski J, Kotze DJ, Lehvävirta S, Fritze H (2008) Edge effects and trampling in boreal urban forest fragments – impacts on the soil microbial community. Soil BiolBiochem 40:1612-1621
Tamminen P, Starr MR (1990) A survey of forest soil properties related to soil acidification in southern Finland. In: Kauppi P, Anttila P, Kenttämies K (eds), Acidification in Finland. Springer-Verlag, Berlin, pp 234-251