Patterns of covariance between airborne laser scanning metrics and Lorenz curve descriptors of tree size inequality

In this study, Lorenz curve descriptors of tree diameter inequality were used to characterize the dynamics of forest development in a shelterwood-managed Pinus sylvestris (L.) dominated area. The purpose was to stratify the forest area into forest structural types (FST) from airborne laser scanning (ALS)-based wall-to-wall predictions of the chosen indicators: Gini coefficient (GC) and Lorenz asymmetry (LA). A clear boundary at GC = 0.5 was found, which separated even-sized (below) and uneven-sized (above) areas. Furthermore, a need for including LA in the characterization of the uneven-sized areas was detected, to distinguish bimodal from reverse J-shaped stands. Beta regression was used for the ALS predictions, yielding RMSEs of 19.67% for GC and 11.01% for LA. Based on our results, we concluded that forest disturbance decreases GC, whereas seed regeneration increases GC and, therefore, gap dynamics are characterized by shifts between either side of the GC = 0.5 threshold. In even-sized stands, GC decreases toward maturity owing to self-thinning occurring at the stem exclusion stage. In uneven-sized stands, the skewness of the Lorenz curve indicates understory development, as ingrowth decreases LA. The possible applications of the resulting FST map are discussed; for instance, in identifying areas needing silvicultural treatments or evaluating forest recovery from disturbances.

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A Comparison of Airborne Laser Scanning and Image Point Cloud Derived Tree Size Class Distribution Models in Boreal Ontario

Forests ◽

10.3390/f6114034 ◽

2015 ◽

Vol 6 (12) ◽

pp. 4034-4054 ◽

Cited By ~ 24

Author(s):

Margaret Penner ◽

Murray Woods ◽

Douglas Pitt

Keyword(s):

Point Cloud ◽

Laser Scanning ◽

Size Class ◽

Airborne Laser Scanning ◽

Tree Size ◽

Image Point ◽

Distribution Models ◽

Size Class Distribution ◽

Class Distribution ◽

Airborne Laser

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Comparing individual tree detection and the area-based statistical approach for the retrieval of forest stand characteristics using airborne laser scanning in Scots pine stands

Canadian Journal of Forest Research ◽

10.1139/x10-223 ◽

2011 ◽

Vol 41 (3) ◽

pp. 583-598 ◽

Cited By ~ 32

Author(s):

Jussi Peuhkurinen ◽

Lauri Mehtätalo ◽

Matti Maltamo

Keyword(s):

Laser Scanning ◽

Statistical Approach ◽

Basal Area ◽

Airborne Laser Scanning ◽

Tree Size ◽

Size Distributions ◽

Individual Tree ◽

Tree Detection ◽

Airborne Laser ◽

Number Of Stems

Airborne laser scanning based forest inventories employ two major methods: individual tree detection (ITD) and the area-based statistical approach (ABSA). ITD is based on the assumption that trees are of a certain form and can be delineated using airborne laser scanning techniques, whereas ABSA is an empirical method based on the relations between area-level forest attributes and laser echo height distributions. These two methods are compared here within the same test area in terms of their usefulness for estimating mean forest stand characteristics and tree size distributions. All evaluations were performed using leave-one-out cross validation. The average errors in volume and basal area did not differ significantly between the methods. ABSA resulted in overall better accuracies when estimating the diameter and height of the basal area median tree and the number of stems, whereas ITD produced significantly biased estimates for the number of stems and the mean tree size. Tree size distributions were estimated with slightly better accuracy using ABSA. More comprehensive investigations revealed that both methods were not able to estimate forest structure (tree size distribution and spatial distribution of tree locations), which in turn, affected the estimation accuracies.

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