Dynamic effects of insect herbivory and climate on tundra shrub growth: roles of browsing and ramet age
Data files
Nov 02, 2020 version files 349.62 KB
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Virtanen_2020_JEcology_Data.csv
Nov 09, 2020 version files 373.19 KB
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edm_analysis_shoot_precip_sup.R
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Virtanen_2020_JEcology_Data.csv
Abstract
Methods
The study area is located in NW Finnish Lapland at a transitional area between boreal mountain birch forests and treeless oroarctic and arctic tundra heaths at higher elevations (Virtanen et al., 2016). The study site lies at an elevation of 550–570 m a.s.l. (68.92° N, 20.97° E). In total, 40 willow genets in two forest-tundra ecotone sites were selected for the experiment in 1997. In these two sites lying c. 800 m apart, the genets were selected within areas of c. 50 × 200 m and 50 × 250 m. Genets were 30–50 cm tall and consisted of 10–25 ramets each. All genets were initially accessible to both reindeer and ptarmigan. The genets were then assigned into blocks of four genets. In 1997–1998, two random genets within each block were rejuvenated by pruning ramets five cm above the ground level. The pruned genets produced sprouts that initially grew vigorously for 1–3 years and within a few years reached the size of unpruned genets. Thus, each block consisted of two old genets and two rejuvenated genets. Within each block one of the old and rejuvenated genets were protected by reindeer fences (2×2 m area). In 2000, reindeer fences were replaced by ptarmigan proof fences in half of the blocks, selected at random. Final treatments therefore included rejuvination ("J"), reindeer browsing ("R"), and ptarmagin browsing ("P").
Usage notes
Data are in .csv format, with decimal points indicated by ".". "GDD5MJJ" shows summed daily mean temperature in excess of + 5 °C in May–July. "PJune" and "PJuly" show summed annual precipitation in June and July, in mm. Lastly, columns "s1.cm" through "s11.cm" show shoot lengths -- the mean taken across these columns was the primary response variable in our paper. Finally, the ".R" file includes the source code used to analyse these data.