Dobbertin M, Baltensweiler A, Rigling D (2001) Tree mortality in an unmanaged mountain pine (Pinus mugo var. uncinata) stand in the Swiss National Park impacted by root rot fungi. Forest Ecology and Management, 145: 79-89. [10.1016/S0378-1127(00)00576-4]


CC/DB-WSI: tree mortality; spatial statistics; root disease; Pinus mugo var. uncinata, long term; jack pine; dynamics ; competition ; population ; Methods: spatial analysis, Plants: Pinus mugo, spatial analysis


We investigated mortality patterns and their possible causes in a Swiss mountain pine forest. Although the period of observation was only 4 years, it was possible to estimate spatial relationships between tree conditions and past and future stand dynamics. The 2 ha research plot, established in 1995 as part of the Swiss long-term forest ecosystem research programme (LWF), is located in the Swiss National Park and has not been managed since 1914. Tree assessments in 1995 and 1998 gave an annual mortality rate for standing trees of 1.5% and annual fall-down rates of 0.7%, while ingrowth was 1.4% of the initial toe number in 1995. Over the past 4 years the percentage of standing dead trees with stem diameters of at least 12 cm has increased by 0.8% annually to more than 20%.The trees that died during the last 3 years were significantly smaller than the surviving trees. However, the available growing space, as indicated by Thiessen polygons, of all living trees in 1995 was not different between the two groups of trees. Mortality due to competition alone was therefore discounted. Kernel estimation showed clusters for living and dead trees, with high densities of dead trees in areas of low densities of living trees and vice versa. Nearest-neighbour distances and K-functions showed that the spatial distributions of both living and dead trees were significantly clustered. The clustering of dead trees was higher than expected under random mortality. Sixty-one trees that died in the last 2 years were analysed for root rot. More than 90% were infected by root rot fungi (Armillaria spp. and/or Heterobasidion annosum). Two thirds of the trees were infected by H, annosum and 50% by Armillaria spp., with 18% of the trees having infections by both pathogens. Trees with H. annosum were on average larger, and the growing space of trees with H. annosum tended to be larger than for trees without H. annosum. This suggests that H. annosum was a primary cause of tree death. Future studies are planned to quantify the effects of both Armillaria and annosum root disease in this mortality process. In summary, our study suggests that pathogens play an important role in the dynamics of these natural mountain pine ecosystems. (C) 2001 Elsevier Science B.V. All lights reserved.

LWF Classification

Network: LWF, Sites: Nationalpark, Category: ISI,