Abstract
ContextChanges in the structure of boreal old-growth forests are typically studied at a specific spatial scale. Consequently, little is known about forest development across different spatial scales.ObjectivesWe investigated how and at what spatial scales forest structure changed over several decades in three 4 km2 boreal old-growth forests landscapes in northeastern Finland and two in Quebec, Canada.MethodsWe used canopy cover values visually interpreted to 0.1-ha grid cells from aerial photographs taken at three time points between the years 1959 and 2011, and error distributions quantified for the interpretation. We identified the spatial scales at which canopy cover changed between the time points, and examined the credibility of changes at these scales using the error distributions in Bayesian inference.ResultsCanopy cover changed at three to four spatial scales, the number of scales depending on the studied landscape and time interval. At large scales (15.4–321.7 ha), canopy cover increased in Finland during all time intervals. In Quebec, the direction of the large-scale change varied between the studied time intervals, owing to the occurrence of an insect outbreak and a consequent recovery. However, parts of these landscapes also showed canopy cover increase. Superimposed on the large-scale developments, canopy cover changed variably at smaller scales (1.3–2.8-ha and 0.1-ha).ConclusionsOur findings support the idea that the structure of boreal old-growth forests changes at discernible spatial scales. Instead of being driven by gap dynamics, the old-growth forests in the studied regions are currently reacting to large-scale drivers by an increase in canopy cover.
Highlights
Vast areas of boreal forests still remain outside of direct human influence (Gauthier et al 2015)
Canopy cover changed at three to four spatial scales, the number of scales depending on the studied landscape and time interval
During the whole study interval (38 to 52 years, depending on the landscape), we identified canopy cover changes at three spatial scales in each landscape, based on the scale-derivative analysis
Summary
Vast areas of boreal forests still remain outside of direct human influence (Gauthier et al 2015). These forests play a crucial role in global biodiversity conservation (Thom and Seidl 2016), and terrestrial carbon cycling and storage (Bradshaw and Warkentin 2015). Stand-replacing disturbances which caused tree mortality over large areas, fire, were considered the most important processes that alter boreal forest structure (e.g., Zackrisson 1977; Bouchard et al 2008; Wallenius 2011), while research during the past couple of decades has emphasized the role of small-scale disturbances (e.g., Kuuluvainen 1994; Pham et al 2004; St-Denis et al 2010). Understanding how boreal forests develop requires that forest dynamics is studied at multiple spatial and temporal scales, at levels beyond the conventional gap-landscape – dichotomy
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.
