Influence of Stand Density on Crown Formation and Growth along the Diameter of Scots Pine (Pinus sylvestris L.)

Abstract

Crown size determines tree’s life space formation, its growth and development. The research object was a middle-aged pine stand spatially included in the Krasnoyarsk island forest-steppe. The permanent trial plot of 0.15 ha size with over 300 trees was established in high-yield green moss pine forest. Each tree on the plot was mapped and assigned with an individual number; its diameter at breast height was measured. A large-scale survey of the trial plot with resolution of 25 cm was acquired using the unmanned aerial vehicle (UAV). The trial plot identification on the image and its matching with the land-based mapping data were performed in ArcMap. In this program crowns of all trees are outlined and areas of their projections are calculated using GIS-technology methods. The data analysis showed a close correlation between crown projection contours and areas and the field data. Dominance area (SОД) was used as an available resource valuation for a tree in the competition conditions in a forest stand. Dominance area is defined as an area, where each individual tree has dominating influence in space around it and obtains light and soil resource in assumption that this influence is directly proportional to sample size and inverse to squared distance to it. It was found that crowns of rare and medium density with projection area (Sкр) of 2…6 m² are formed in case of a low dominance area (less than 6 m2). Crowns with SОД of 6…12 m² have high density and projection area up to 10 m² and length more than 40 % of tree height. The dynamics of tree radial increment after thinning at the age of 37 was studied depending on the dominance area increase. During 4 years after thinning, annual radial increment increases up to 2 times with increase of available resource. Regression analysis has shown strong correlation between crown projection area and dominance area with a correlation coefficient R = 0.84. Use of UAV is a promising, low-cost and effective technique of distance studying the tree stand structure. Office analysis of images allows to obtain crown projection area characteristics. These data can be used in improvement thinning and forming of even-aged pine stand canopy, which provide the maximum use of light
and soil resource and effective ecological forest functioning.

For citation: Ivanov V.V., Borisov A.N., Petrenko A.E. Influence of Stand Density on Crown Formation and Growth along the Diameter of Scots Pine (Pinus sylvestris L.). Lesnoy Zhurnal [Forestry Journal], 2019, no. 3, pp. 9–16. DOI: 10.17238/issn0536-1036.2019.3.9

Funding: The research was carried out within the framework of fundamental scientific research programs of the Russian Academy of Sciences no. 0356-2016-0706. State Registration (TsITIS) no. АААА-А17-117101940014-9 “Theoretical Foundations for the Ecological and Resource Potential Conservation of Siberian Forests in the Conditions of Increasing Anthropogenic Pressure and Climatic Anomalies”.

Acknowledgements: The authors are grateful to Rubtsov A.V. for the provided aerial photographic image of the forest site.