Figure 4.

NMDS ordination of annual arthropod communities from Zackenberg, Greenland between 1996 and 2014 in wet fen (black circles), mesic heath (blue filled circles) and arid heath (red triangles) habitats. Each point represents the community composition from a single plot within a given sampling year. (a) PC1, indicative of warmer active seasons and fewer winter freeze–thaw events, and PC2, indicative of warmer non-active seasons, are overlaid as correlation vectors, whereby the arrows show the direction of the gradient, and the length of the arrows are proportional to the correlations between the climatic variables and the ordination (PC1: p = 0.004; r² = 0.13; PC2: p = 0.003; r² = 0.12). Abbreviations in black denote the centroids of each of the analysed arthropod groups (Col, Collembola; Aca, Acari; Dip, Diptera; Lep, Lepidoptera; Ara, Araneae; Hem, Hemiptera and Hym, Hymenoptera); habitat-specific communities are delimited by 95% confidence ellipses. (b) Arrows indicate the change in average NMDS scores for communities in each habitat type from the first third (1996–2001) to the last third of the study period (2009–2014).