Abstract
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.
Highlights
The size of a tree correlates with the space a tree occupies and it defines tree growth that is linked to carbon sequestration (Vanninen and Mäkelä, 2000, 2005; Rayment et al, 2002; Pretzsch et al, 2015)
Livecrown ratio and crown diameter at the bottom of a crown (i.e., 10–30 percentiles) (Figure 5) statistically significantly (p < 0.05) increased when thinning intensity increased, but this was true for all thinning types
Stem densities affected crown size and shape of Scots pine trees growing in boreal forests
Summary
Trees are direct available resources to reproduction and growth and can regulate their size and the relationship between their parts. Removal or death of trees enhances the light regime and photosynthesis for the remaining trees, which increases the crown size This is evident near the lowest limit of live crown where changes in the amount of light increase considerably more compared to the top of a tree. Trees of different species require differing amount of growing space; birch (Betula sp.) requires more space than Scots pine (Pinus sylvetris L.), which in turn is more demanding than Norway spruce [Picea abies In dense forests, lower branches die due to the limited amount of light (Heikinheimo, 1953; Flower-Ellis et al, 1976; Kellomäki, 1980) for light-demanding species such as Scots pines and birches (Kellomäki and Tuimala, 1981) and loblolly pine (Pinus taeda L.) (Zeide, 1998), and this decreases live-crown ratio (i.e., proportion of live crown from tree height). Raulier et al (1996) discovered that stand structure did not affect crown adjustment of black spruce [Picea mariana (Mill.) BSP]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
