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Spatial variability of leaf area index in homogeneous forests relates to local variation in tree characteristics

  • Life Sciences :: Environmental Sciences & Ecology [F08]
  • Sciences Du Vivant :: Sciences De L'Environnement & éCologie [F08]


Spatial variability of leaf area index in homogeneous forests relates 1 to local variation in tree characteristics 2 3 Keywords: Error, sample size, sampling strategy, tree height, crown length, distance 4 5 6 Abstract 7 8 Forest canopy density can be highly variable within one stand. The accuracy of indirect 9 methods to quantify stand leaf area index (LAI) is often unknown, and intensive sampling strategies are 10 required. Our objectives were to study the drivers of the spatial LAI variability, and to improve the 11 sampling strategy based on a sampling protocol as a function of the local canopy pattern. We examined 12 the spatial variability of hemispherical photography (HP) based LAI estimates of European beech 13 (Fagus sylvatica L.), pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.) in 14 Flanders, Belgium. Within the 30 selected forest stands, a regular grid of 16 LAI measurement points 15 and a circular forest inventory plot were established. The LAI estimates of the grid points were used to 16 calculate the LAI of the squared cells (defined as ‘patches’), within the regular grid. Local forest 17 inventory data were used to study the drivers of the deviation of patch LAI (LAIdev) relative to the 18 average plot LAI. Average tree distance from a patch centre was negatively related with the LAIdev. Tree 19 structural characteristics (diameter at breast height (DBH), tree height, crown length and crown cover) 20 were all positively related to the LAIdev. Based on our findings, we suggest that for the analysed forest 21 types, sampling layouts for HP-based LAI estimates should follow a pattern of selecting two (beech 22 and pine) or three (oak) sample points and positioning the camera at a distance of approximately 23 20% of the dominant height from one (beech) or two (oak and pine) large trees. 24 Introduction 25 26 The leaf area index (LAI; m2 leaf m-2 ground) is

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