title: Quantitative characterization of clumping in Scots pine crowns.
abstract: OBJECTIVE
  Proper characterization of the clumped structure of forests is needed for calculation of the absorbed radiation and photosynthetic production by a canopy. This study examined the dependency of crown-level clumping on tree size and growth conditions in Scots pine (Pinus sylvestris), and determined the ability of statistical canopy radiation models to quantify the degree of self-shading within crowns as a result of the clumping effect.
  
  
  METHODS
  Twelve 3-D Scots pine trees were generated using an application of the LIGNUM model, and the crown-level clumping as quantified by the crown silhouette to total needle area ratio (STAR(crown)) was calculated. The results were compared with those produced by the stochastic approach of modelling tree crowns as geometric shapes filled with a random medium.
  
  
  RESULTS
  Crown clumping was independent of tree height, needle area and growth conditions. The results supported the capability of the stochastic approach in characterizing clumping in crowns given that the outer shell of the tree crown is well represented.
  
  
  CONCLUSIONS
  Variation in the whole-stand clumping index is induced by differences in the spatial pattern of trees as a function of, for example, stand age rather than by changes in the degree of self-shading within individual crowns as they grow bigger.
authors.forename: Pauline
authors.initials: P
authors.lastname: Stenberg
authors.forename: Matti
authors.initials: M
authors.lastname: Mõttus
authors.forename: Miina
authors.initials: M
authors.lastname: Rautiainen
authors.forename: Risto
authors.initials: R
authors.lastname: Sievänen
mesh_terms: D018533:Biomass; D008954:Models, Biological; D010788:Photosynthesis / Q000528:radiation effects; D041605:Pinus sylvestris / Q000033:anatomy & histology* / Q000254:growth & development / Q000528:radiation effects; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000254:growth & development / Q000528:radiation effects; D014197:Trees