Fig. 2.

Concentric circles are used to measure the proportion of countryside forest elements at different scales: landscape scales (A) and fine scales (B). Gray areas are countryside forest elements detected because they are ≥4 m² in size. (C) Correlation between community similarity index and the proportion of countryside forest elements at landscape scales. Each point represents the Pearson correlation coefficient (r) for each landscape-scale sampling location on farmland (n = 15) and the proportion of countryside forest elements within the radius on the horizontal axis. To demonstrate how critical even the smallest forest elements can be, we compare correlations between countryside forest elements from 2-m resolution aerial photographs (•) with forest cover calculated from 28.5-m resolution satellite images (○). Gray dashed lines represent correlation values corresponding to Holm's adjusted P values: thick line, P < 0.001; medium line, P < 0.01; and thin line, P < 0.05. (D) Correlation between community similarity index and the proportion of countryside forest elements at fine scales. Each point represents the Pearson correlation coefficient (r) for each fine-scale sampling location in farmland (n = 39) and the proportion of countryside forest elements within the radius on the horizontal axis. The single black point is the highest correlation (r = 0.939), indicated by the arrow. Error bars show 95% confidence intervals based on Fisher's Z transformation. All correlations were significant (Holm's adjusted P values at P < 0.001).