Pouttu A, Dobbertin M (2000) Needle-retention and density patterns in Pinus sylvestris in the Rhone Valley of Switzerland: comparing results of the needle-trace method with visual defoliation assessments. Canadian Journal of Forest Research-Revue Canadienne De Recherche Forestiere, 30 (12): 1973-1982.


needle retention, above-ground part of trees, Methods: reconstruction, Plants: Pinus sylvestris, reconstruction


We used the needle-trace method (NTM) to reveal the needle-retention patterns of Scots pine (Pinus sylvestris L.) over the past 100 years. The average annual needle retention (ANR) on main stems has gradually decreased from five needle sets in the 1890s to four needle sets in the 1990s. Needle retention is significantly correlated with tree age and altitude, and the decrease in needle retention may be at least in part due to the increasing ages of sample trees. The average needle density varied plotwise between 7.2 and 10.5 short shoots/cm. In a comparison of ANR values and visually assessed foliage percentage from the Swiss Forest Health Inventory between 1985 and 1996, we found significant correlation between the mean annual values. While the direction of annual change was identical in two thirds of all years we found disagreement in 3 years. Both needle retention and foliage were lower in the early 1990s than in the late 1980s. With the help of the NTM we can show that there had been similar decreases in foliage usually connected with severe droughts during the last century.

LWF Classification

Network: LWF, Sites: Visp, Category: ISI,