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Abstract: At the scale of forest stands, there is a lack of quantitative, statistically valid data on the protective effect of forests against rockfall. Therefore, the first objective of this study was to quantify the velocities, rebound heights as well as the residual hazard of rockfall on a forested and a non-forested slope. The second objective was to evaluate existing rockfall protection forest management guidelines, as well as the underlying criteria. We carried out and analysed 100 real size rockfall experiments at a non-forested site (Site 1) and 102 identical experiments at a forested site (Site 2) on the same slope. We compared the obtained results with literature data on rockfall protection forests. At the non-forested site, results show that the mean maximum velocity is 15.4ms−1 compared to 11.7ms−1 at the forested site. The maximum rebound height decreases from 8m (Site 1) to 2m (Site 2) and the number of rocks that surpass the 223.5m slope distance decreases from 95 out of 100 (Site 1) to 35 out of 102 (Site 2). A major effect of rockfall on a forested slope is the development of a treeless rockfall path or couloir, which had evolved after releasing 78 rocks at Site 2. The effect of such a couloir can be mitigated by cutting trees on both sides of the couloir and leaving the trunks on the slope, diagonally to the slope direction. This is a known and effective technique to reduce the effect of gaps in protection forests. During our experiments, none of the rocks attained their maximal velocity within the first 40m. They did, however, attain destructive velocities (11–15ms−1) within that distance. Based on our observations, we propose a maximum gap size in the slope direction of 1.3 times the mean tree height, with a maximum of 40m. Further, we present various findings that have direct implications for the management of rockfall protection forests. Finally, the results proved that forests can provide effective protection against rockfall. [Copyright &y& Elsevier]

We present repeated tree measurement data from 63 permanent plots in mountain forests in France. Plot elevations range from 800 (lower limit of the montane belt) to 1942 m above sea level (subalpine belt). Forests mainly consist of pure or mixed stands dominated by European beech ( Fagus sylvatica), Silver fir ( Abies alba), and Norway spruce ( Picea abies), in association with various broadleaved species at low elevation and with Arolla pine ( Pinus cembra) at high elevation. The plot network includes 23 plots in stands that have not been managed for the last 40 years (at least) and 40 plots in plots managed according to an uneven-aged system with single-tree or small-group selection cutting. Plot sizes range from 0.2 to 1.9 ha. Plots were installed from 1994 to 2004 and remeasured two to five times during the 1994-2015 period. During the first census (installation), living trees more than 7.5 cm in dbh were identified, their diameter at breast height (dbh) was measured and their social status (strata) noted. Trees were spatially located, either with x, y, and z coordinates (40 plots) or within 0.25-ha square subplots (23 plots). In addition, in a subset of plots (58 plots), tree heights and tree crown dimensions were measured on a subset of trees and dead standing trees and stumps were included in the census. Remeasurements after installation include live tree diameters (including recruited trees), tree status (living, damaged, dead, stump), and for a subset of trees, height. At the time of establishment of the plots, plot densities range from 181 to 1328 stems/ha and plot basal areas range from 13.6 to 81.3 m2/ha. [ABSTRACT FROM AUTHOR]