Fig. 3
From: Low-level retention forestry, certification, and biodiversity: case Finland
Volumes of living large-diameter (DBH > 20 cm, solid line) and small-diameter (10–20 cm, dotted lined) retention trees and dead trees (DBH > 10 cm or DBH > 20 cm from 2005 onwards, dashed line) (m3/ha) in 1998–2017 in clearcutting areas of private forests (data: Forestry Centre Tapio 2013, Finnish Forest Centre 2019). The volume of living large-diameter retention trees has remained quite the same despite the starting peak in the early years of PEFC certification (early 2000s) (Kendall’s rank correlation coefficient rK = − 0.08, p = 0.643). The volume of living small-diameter retention trees has decreased during the monitoring years (rK = − 0.61, p < 0.001) and that of dead retention trees has slightly decreased but not statistically significantly so (rK = − 0.33, p = 0.053). The pooled volume of all living retention trees has decreased (rK = − 0.35, p = 0.041)