Fig. 2
From: Low-level retention forestry, certification, and biodiversity: case Finland
Proportion of living retention trees (solid line) and living trees retained in set-asides (different types of valuable woodland key habitats, dotted line) of the stand volume (%) in 1998–2017 in clearcutting areas of private forests (data: Forestry Centre Tapio 2013, Finnish Forest Centre 2019). The proportion of living retention trees of the stand volume has decreased during the monitoring years from the level of the early years of PEFC certification (early 2000s) (Kendall’s rank correlation coefficient rK = − 0.57, p = 0.001) whereas the proportion of living trees retained in set-asides has remained the same (rK = 0.11, p = 0.574). Thus, also the pooled proportion of living retention trees and living trees retained in set-asides of the stand volume has decreased (rK = − 0.50, p = 0.005). Data for the year 2017 were not included in the above analyses (see text)