Scots Pine Crown Research Articles

Effects of Stem Density on Crown Architecture of Scots Pine Trees.

Trees adapt to their growing conditions by regulating the sizes of their parts and their relationships. For example, removal or death of adjacent trees increases the growing space and the amount of light received by the remaining trees enabling their crowns to expand. Knowledge about the effects of silvicultural practices on crown size and shape and also about the quality of branches affecting the shape of a crown is, however, still limited. Thus, the aim was to study the crown structure of individual Scots pine trees in forest stands with varying stem densities due to past forest management practices. Furthermore, we wanted to understand how crown and stem attributes and also tree growth affect stem area at the height of maximum crown diameter (SAHMC), which could be used as a proxy for tree growth potential. We used terrestrial laser scanning (TLS) to generate attributes characterizing crown size and shape. The results showed that increasing stem density decreased Scots pine crown size. TLS provided more detailed attributes for crown characterization compared with traditional field measurements. Furthermore, decreasing stem density increased SAHMC, and strong relationships (Spearman’s correlations > 0.5) were found between SAHMC and crown and stem size and also stem growth. Thus, this study provided quantitative and more comprehensive characterization of Scots pine crowns and their growth potential. The combination of a traditional growth and yield study design and 3D characterization of crown architecture and growth potential can open up new research possibilities.

Quantitative characterization of clumping in Scots pine crowns.

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. 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. 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. 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.

Effects of wood ash and nitrogen fertilization on Scots pine crown biomass

The crown biomass, being one of the most susceptible components of the above-ground tree biomass, could respond positively to environmental changes and temporary increase in nutrient availability. The influence of wood ash and nitrogen fertilization on crown biomass was studied in a 40-year-old Scots pine (Pinus sylvestris L.) stand growing on a Haplic Arenosol. The 36-model trees for the crown biomass measurements were sampled for 3 growing seasons after the application of 5.0 t wood ash ha -1 , 180 kg N ha -1 , 2.5 t wood ash ha -1 plus 180 kg N ha -1 , and control (untreated plots). The masses of the current, 1-year-old and older needles and shoots, and branches were measured. A significant influence on the current year needles and shoots was found after the application of 180 kg N ha -1 or 2.5 t wood ash ha -1 plus 180 kg N ha -1 . When wood ash was applied in combination with nitrogen, an extra response tendency of the crown growth, especially of the top and the middle sections of the crown, was determined. However, there was no short-term influence of wood ash on crown biomass growth.

Vertical structure of Scots pine crowns in different age and size classes

The pipe model theory postulates a static relationship between foliage mass/area and the cross-sectional area of active pipes in branches and stems. If a regular relationship exists, the theory can be used for modelling growth allocation within crowns, provided that the turnover of active pipes and foliage is understood. The objective of this study was to assess to what extent the assumptions of the pipe model hold true within the crowns of 24 Scots pine sample trees of different age and social position. The results suggest that Scots pine crowns are very regular, but some important modifications to the pipe model assumptions are required. The relative vertical foliage density distribution peaked at about 50% down the live crown regardless of age or social position. The ratio of foliage mass to branch cross-sectional area in the top half of the crown increased from the top downwards. The ratio of cumulative branch cross-sectional area to stem cross-sectional area in the top half seemed to increase with tree vigour or growth rate. The ratio of foliage mass to branch cross-sectional area decreased fast in the lower half of the crown, and this decrease was faster than could be predicted from heartwood formation in the branches. This result may be taken as (1) evidence against the pipe model, or as (2) an indication that active pipes cannot always be identified with sapwood. The latter proposition should be studied further.

A model for the structural growth of young Scots pine crowns based on light interception by shoots

A model for the structural growth of the crown of a young Scots pine ( Pinus sylvestris) is described. Each shoot produces new shoots, whose number and length are linearly related to the length of the parent shoot. The length of parent shoots is computed from the amount of direct and diffuse radiation intercepted by the parent shoot during the previous growing season. This procedure utilizes the spatial distribution of shoots (location, azimuth, inclination) produced by the growth process, and the structure of the shoots as determined in terms of the needle density, needle angle and length of needles with no need in advance to specify the statistical distribution of shoots in the crown space. The computations indicate that shoot structure could have only a negligible effect on the total light interception compared to the total needle area and its distribution within the crown. The modelling based on modular growth with a shoot as a basic computational unit seems to have great potential in describing the interaction between the tree crown and light conditions and the structural development of the crown system.

A model for the structural development of a Scots pine crown based on modular growth

A model is described for the structural development of the crown system of young Scots pine ( Pinus sylvestris L.) based on modular growth, where a shoot is the basic unit of structural development. The model input represents the initial length of the stem, which is utilized in generating the structural development of the crown during a given time period. The model parameters represent the branching habit (number of shoots produced from each shoot and branching angle of shoots), dimensions (length, diamete and biomass) and the death of the shoots as arranged in orders of modules. The properties of the model in terms of the crown structure are discussed.

Crown projection area of young Pinus sylvestris: A model and its test

In this study we applied a theoretical model for determining the projection area of a Scots pine (Pinus sylvestris L.) crown in different directions. The model is based on the assumption that the foliage elements (shoots) are randomly distributed within a symmetrical crown envelope. The model was tested using photographically measured data for three young Scots pine crowns. The compatibility between calculated and measured values was satisfactory.

Architecture of Scots pine crown.

Architecture of Scots pine crown.