Linking crown plasticity to tree growth using terrestrial laser scanning under a gradient of competition conditions

PI : Ignacio Barbeito (Laboratoire d’Étude Ressource Forêt-Bois — LERFOB)

Co-applicants :
François Ningre, Catherine Collet (Laboratoire d’Étude Ressource Forêt-Bois — LERFOB)
Patrick Vallet, Thomas Perot (IRSTEA)
Alexandre Piboule (R&D, ONF)

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Context — Canopy structure has profound effects on forest productivity, biodiversity and potential resistance to disturbances. Until recently, many whole plant architectural studies were performed only in small plants, since canopy variables were difficult to access in the field. This can be now overcome by the use of high-resolution terrestrial laser scanning (TLS), a non-destructive tool that allows us to collect detailed data of the 3-D canopy.

Objectives — The question remains how different silvicultural practices aimed initially at optimizing productivity- but that could potentially be used to better adapt management to extreme climatic events such as droughts- affect crown structure and architecture; and how crown attributes, in turn, influence growth. Moreover, we aim to understand what is fundamentally different in crown competition across plant sizes.

Approaches — We will replicate TLS surveys of sessile oak trees (Quercus petraea Liebl.), a widely distributed broadleaved species found in plain forests across western Europe, under a range of growth conditions (low to high competition) modified by thinnings and by species mixing, and explore variation determinants in crown architecture. We will use two fully inventoried experimental sites, one in a pure even-aged oak stand (Forest of Tronçais) and another one in pure and mixed stands with Scots pine (Orleans State Forest). We will scan around 100 trees in each site to extract descriptors of crown architecture such as crown projected surface, crown volume or displacement of the crown center of gravity from the stem base. We will make use of the growth data available to classify the trees in growth classes and test if different crown architectures lead to different growth patterns.

Expected results and impacts — Our results will inform forest management on the effect that modifying competition through density and species mixing management of trees of different sizes has on crown structure and effects on forest productivity in the context of climate change.