Modelling and Comparing Shading Effects of 3D Tree Structures with Virtual Leaves

Abstract

Reduced solar radiation brought about by trees on agricultural land can both positively and negatively affect crop growth. For a better understanding of this issue, we aim for an improved simulation of the shade cast by trees in agroforestry systems and a precise estimation of insolation reduction. We present a leaf creation algorithm to generate realistic leaves to be placed upon quantitative structure models (QSMs) of real trees. Further, we couple it with an enhanced approach of a 3D model capable of quantifying shading effects of a tree, at a high temporal and spatial resolution. Hence, 3D data derived from wild cherry trees (Prunus avium L.) generated by terrestrial laser scanner technology formed a basis for the tree reconstruction, and served as leaf-off mode. Two leaf-on modes were simulated: realistic leaves, fed with leaf data from wild cherry trees; and ellipsoidal leaves, having ellipsoids as leaf-replacement. For comparison, we assessed the shading effects using hemispherical photography as an alternative method. Results showed that insolation reduction was higher using realistic leaves, and that the shaded area was greater in size than with the ellipsoidal leaves or leaf-off conditions. All shading effects were similarly distributed on the ground, with the exception of those derived through hemispherical photography, which were greater in size, but with less insolation reduction than realistic leaves. The main achievements of this study are: the enhancement of the leaf-on mode for QSMs with realistic leaves, the updates of the shadow model, and the comparison of shading effects. We provide evidence that the inclusion of realistic leaves with precise 3D data might be fundamental to accurately model the shading effects of trees.

Low Cost Automatic Reconstruction of Tree Structure by AdQSM with Terrestrial Close-Range Photogrammetry

“…The minimum spanning tree (MST) between the Delaunay triangulation edges of point clouds was found [49,50]. The length of edge defined in Euclidean space weighted all edges.…”

“…To test the accuracy of QSM method in estimating trunk volume from TP point clouds, we compared reconstructed trunk volume values of AdQSM and TreeQSM with reference trunk volume of the allometric equation respectively, Figure 14 Figure 16 [40,41]. At present, AdQSM has attracted more and more people's attention [50][51][52][53]. AdQSM needs to be tested using photogrammetric point clouds.…”

“…Using trunk volume derived from allometric [40,41]. At present, AdQSM has attracted more and more people's attention [50][51][52][53]. AdQSM needs to be tested using photogrammetric point clouds.…”

Virtual pruning of 3D trees as a tool for managing shading effects in agroforestry systems

“…Recently, TLS derived point clouds coupled with QSMs have been used for modelling the shade cast at fine spatiotemporal resolutions, thus improving the understanding of the role of trees as physical light obstacles. Initial works by Rosskopf et al (2017), Bohn Reckziegel et al (2021, have demonstrated the potential of applying these approaches.…”

“…The innovation of our research lies within the application of these analogous tree structures, for creating shading scenarios, and by doing so, supporting the design and choice of adequate tending operations. Pruned and unpruned tree structures are fed into a shadow model (Bohn Reckziegel et al 2021) with a fine spatiotemporal resolution, to simulate the shade cast over twelve months and to estimate the insolation reduction on the ground as a result. We hypothesise that conventional and selective pruning methods with comparable branch volume removal differ markedly in both retained tree structures and the shading effects.…”