Peer Review #2 of "Using lidar to assess the development of structural diversity in forests undergoing passive rewilding in temperate Northern Europe (v0.1)" [peer_review]

2019 unpublished
Forested areas are increasing across Europe, driven by both reforestation programs and farmland abandonment. While tree planting remains the standard reforestation strategy, there is increased interest in spontaneous regeneration as a cost-effective method with equal or potentially greater benefits. Furthermore, expanding areas of already established forests are left for passive rewilding to promote biodiversity conservation. Effective and objective methods are needed for monitoring and
more » ... itoring and analyzing the development of forest structure under these management scenarios, with airborne laser scanning (lidar: Light Detection And Ranging) being a promising methodology. Here we assess the structural characteristics and development of unmanaged forests and 28-to 78-year old spontaneously regenerated forests on former agricultural land, relative to managed forests of similar age in Denmark, using 25 lidar-derived metrics in 10-m and 30-m grid cells. We analyzed the lidarderived cell values in a Principal Component Analysis (PCA) and interpreted the axes ecologically, in conjunction with pairwise tests of median and variance of PCA-values for each forest. Spontaneously regenerated forest in general had increased structural heterogeneity compared to planted and managed forests. Furthermore, structural heterogeneity kept increasing in spontaneously regenerated forest across the maximal 78-year timespan investigated. Natural disturbances showed strong impacts on vegetation structure, leading to both structural homogeneity and heterogeneity. The results illustrate the utility of passive rewilding for generating structurally heterogeneous forested nature areas, and the utility of lidar surveys for monitoring and interpreting structural development of such forests. PeerJ reviewing PDF | Abstract 14 Forested areas are increasing across Europe, driven by both 15 reforestation programs and farmland abandonment. While tree 16 planting remains the standard reforestation strategy, there is 17 increased interest in spontaneous regeneration as a cost-18 effective method with equal or potentially greater benefits. 19 Furthermore, expanding areas of already established forests are 20 left for passive rewilding to promote biodiversity conservation. 21 Effective and objective methods are needed for monitoring and 22 analyzing the development of forest structure under these 23 management scenarios, with airborne laser scanning (lidar: Light 24 Detection And Ranging) being a promising methodology. 25 Here we assess the structural characteristics and 26 development of unmanaged forests and 28-to 78-year old 27 spontaneously regenerated forests on former agricultural land, 28 relative to managed forests of similar age in Denmark, using 25 29 lidar-derived metrics in 10-m and 30-m grid cells. We analyzed 30 the lidar-derived cell values in a Principal Component Analysis 31 (PCA) and interpreted the axes ecologically, in conjunction with 32 pairwise tests of median and variance of PCA-values for each 33 forest. 34 Spontaneously regenerated forest in general had 35 increased structural heterogeneity compared to planted and 36 managed forests. Furthermore, structural heterogeneity kept PeerJ reviewing PDF | Manuscript to be reviewed 37 increasing in spontaneously regenerated forest across the 38 maximal 78-year timespan investigated. Natural disturbances 39 showed strong impacts on vegetation structure, leading to both 40 structural homogeneity and heterogeneity. The results illustrate 41 the utility of passive rewilding for generating structurally 42 heterogeneous forested nature areas, and the utility of lidar 43 surveys for monitoring and interpreting structural development 44 of such forests. 45 46 47 48
doi:10.7287/peerj.6219v0.1/reviews/2 fatcat:qtpehfomujgedod2jj3i2lazqq