Temporal measurement of the loss of native pinewood in Scotland through the analysis of orthorectified aerial photographs

The aim of this study was to develop a methodology where information on forest cover can be determined by comparing contemporary and historical aerial photographs. The paper describes the role of aerial photography in the production of orthorectified aerial photographs for measuring changes in the presence of individual trees. To test the technique, orthophotographs were compared for two native pinewoods located in north Scotland at Glenfeshie (photographed in 1946 and 1988) and Ballochbuie (photographed in 1965 and 1997). The study demonstrated that the relative lass of individual trees can he measured by mapping trees at different dates. Results suggest that about 18% of the mature tree cover at Glenfeshie was lost between 1946 and 1988. Recruitment into the canopy over the same period was about 2% giving an overall loss over the period of the study of 16% or about 0.4% per annum. Losses at the Ballochbuie native pinewood, between 1965 and 1997 were 2.7% with a recruitment rate of 0.8% giving an overall loss of 1.9% or 0.06% per annum. Losses appeared to increase with decreasing elevation although this was only statistically significant at Glenfeshie. The rate of loss may well be greater given that the present average age of the pine trees is around 200 years. While losses at Ballochbuie appear to be smaller, an evaluation of the current age class structure suggests that the existing population, with 43% of trees between 251 and 300 years old, will disappear at a higher rate than that measured (C) 2000 Academic Press.