@misc{9221779,
  abstract     = {{Old Scots pine (Pinus sylvestris L.) trees provide important habitat structures in boreal forest ecosystems, yet long-term intensive forest management in Sweden has made such trees increasingly rare and difficult to locate across large forest landscapes. Although field-based inventories can identify old trees reliably, they are time-consuming, costly, and spatially limited. This creates a need for scalable approaches that can support retention forestry and conservation planning over large areas. 
This thesis develops and evaluates a method for identifying Scots pine trees with old-like structural characteristics using nationally available airborne laser scanning (ALS) data. Rather than focusing on biological age, the approach targets structural ageing. Structural ageing in Scots pine is commonly expressed through reduced height growth, lateral crown expansion, and increasingly flattened or irregular crown shapes. Individual tree crowns were segmented from canopy height models, and four crown-level structural metrics were derived: tree height, crown diameter, crown flatness, and recent height growth estimated from multi-temporal ALS data.
To account for variation in site conditions that influence tree growth and structure, trees were analysed within environmentally similar strata defined by elevation, soil moisture and peat depth. Within each stratum, an enrichment-based threshold analysis using the LIFT ratio was applied. LIFT was used to identify combinations of structural traits that occurred more frequently than expected under a null assumption of independence. Such enriched trait combinations were interpreted as indicators of old-like structural patterns.
The method was developed in the Idre–Särna forest landscape in northern Dalarna and evaluated in an independent landscape in the Lunsen–Kungshamn–Morga area south of Uppsala. Clear enrichment patterns were detected in a limited number of strata, primarily on dry to fresh mineral soils. Across both study areas, trees classified as structurally old-like represented well below one percent of all segmented crowns. A limited field validation showed high precision but moderate recall (0.37). This indicates that the method successfully identifies a small subset of trees with strong structural ageing signals but not managing to capture all old individuals.
Overall, the results demonstrate that national ALS data can be used to support the identification and prioritization of structurally mature Scots pine at the individual-tree level. The proposed method functions as a decision-support tool that can guide field surveys and complement existing forestry workflows.}},
  author       = {{Westman, Simon}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Master Thesis in Geographical Information Science}},
  title        = {{Detecting Structurally Old Scots Pine: A Crown-Metric Approach Using National ALS and LIFT Enrichment}},
  year         = {{2026}},
}