Abstract
The accurate characterization of three-dimensional (3D) root architecture, volume, and biomass is important for a wide variety of applications in forest ecology and to better understand tree and soil stability. Technological advancements have led to increasingly more digitized and automated procedures, which have been used to more accurately and quickly describe the 3D structure of root systems. Terrestrial laser scanners (TLS) have successfully been used to describe aboveground structures of individual trees and stand structure, but have only recently been applied to the 3D characterization of whole root systems. In this study, 13 recently harvested Norway spruce root systems were mechanically pulled from the soil, cleaned, and their volumes were measured by displacement. The root systems were suspended, scanned with TLS from three different angles, and the root surfaces from the co-registered point clouds were modeled with the 3D Quantitative Structure Model to determine root architecture and volume. The modeling procedure facilitated the rapid derivation of root volume, diameters, break point diameters, linear root length, cumulative percentages, and root fraction counts. The modeled root systems underestimated root system volume by 4.4%. The modeling procedure is widely applicable and easily adapted to derive other important topological and volumetric root variables.
Highlights
Tree roots are estimated to comprise approximately 19%–28% of the total living tree biomass of boreal forests [1,2] and the ability to adequately estimate total root biomass is central to understanding the carbon dynamics and storage capacity of these forest ecosystems [3,4,5,6]
We evaluate how well coarse root system architecture and volume can be estimated by applying 3D quantitative structure modeling to terrestrial laser point cloud data
Visual inspection of the 3D quantitative structure models (QSM) stump models and visualizations of the Terrestrial laser scanners (TLS) point cloud data illustrate that the produced models appear to be realistic and complete representations of the coarse root systems (Figure 2)
Summary
Tree roots are estimated to comprise approximately 19%–28% of the total living tree biomass of boreal forests [1,2] and the ability to adequately estimate total root biomass is central to understanding the carbon dynamics and storage capacity of these forest ecosystems [3,4,5,6]. As illustrated by the reviews in Tobin et al [7], Danjon and Reubens [8], and Danjon et al [9], knowledge of root system architecture is of large importance in order to understand key ecosystem processes including tree stability, slope stabilization, erosion control, water and nutrient uptake through fine roots, and root competition. All of these processes affect a tree species’ competitive performance and aid in the understanding of observed shifts in intra- and interspecific competition and the resulting forest dynamics across resource gradients [10]. The root diameters and lengths, azimuths, inclinations, and depths were manually measured, the 3D coarse-root architecture of the root systems were modeled with software [11]
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