Seventy-seven years of natural disturbances in a mountain forest area — the influence of storm, snow, and insect damage analysed with a long-term time series

Abstract

We investigated the effects of site properties, forest structure, and time on snow breakage, insect outbreaks, windthrow, and total damage for predominantly planted forests. A time series of forest damage in southwestern Germany spanning 77 years, from 1925 to 2001, was available along with a database on site properties and forest structure. The statistical modeling procedure successively addressed (i) probability of damage occurrence, (ii) timber loss in damaging events, and (iii) interaction among damage agents over time. Logistic and linear regressions were combined with multivariate autoregressive techniques. Natural disturbances were responsible for a total timber loss of 3.0 m 3 Á ha -1 Á year -1 . The distribution of the timber loss values over the years and over sites and stands with different properties was modeled with a standard error of 6.7 m 3 Á ha -1 Á year -1 . Disturbances are more likely to occur in previously damaged stands. Storm events typically provoke subsequent insect outbreaks between 2 and 6 years later. Large windthrow and snow breakage events tend to occur periodically, once every 10th, 11th, or 15th year. Analysis of disturbances as a time series significantly enhances understanding of forest risk processes.Résumé : Nous avons étudié les effets des propriétés de la station, de la structure de la forêt et du temps sur les bris causés par la neige, les épidémies d'insectes et les chablis ainsi que sur les dommages totaux dans des forêts issues principalement de plantations. Une série temporelle des dommages causés aux forêts couvrant une période de 77 ans, de 1925 à 2001, dans le sud-ouest de l'Allemagne était disponible ainsi qu'une base de données sur les propriétés de la station et la structure de la forêt. La procédure de modélisation statistique a successivement abordé : (i) la probabilité que surviennent des dommages, (ii) la perte de matière ligneuse lors d'événements entraînant des dommages et (iii) l'interaction dans le temps entre les agents responsables des dommages. Des régressions logistiques et linéaires ont été combinées à des techniques autorégressives multidimensionnelles. Les perturbations naturelles étaient responsables d'une perte totale de 3,0 m 3 Áha -1 Áan -1 de matière ligneuse. La distribution de ces pertes dans le temps et parmi les stations et les peuplements avec différentes propriétés a été modélisée avec un écart type de 6,7 m 3 Áha -1 Áan -1 . Des perturbations ont plus de chances de survenir dans les peuplements déjà endommagés. Typiquement, les tempêtes sont suivies d'épidémies d'insectes deux à six ans plus tard. Les chablis importants et les épisodes de bris causés par la neige ont tendance à survenir périodiquement à tous les 10, 11 ou 15 ans. L'analyse des perturbations sous forme de série temporelle améliore de façon significative la compréhension des processus de risques en forêt.[Traduit par la Rédaction]

Explaining gender differences in private forest risk management

“…All of these can lead not only to a reduction in revenue from forests, but can also threaten their scenic beauty and ecological value (Hanewinkel et al 2008;Seidl et al 2014). Pro-active risk management may be used to reduce the risk of damage.…”

The importance of threat, strategy, and resource appraisals for long-term proactive risk management among forest owners in Sweden

“…In Sweden forests cover almost 70% of the land area, and individual private forest owners own half of the forest (SFA [the Swedish Forest Agency] 2014). Natural hazards damaging the forest may lead to not only a reduction in revenues but also a loss of scenic beauty and damage to ecological values (Hanewinkel et al 2008;Seidl et al 2014). Owners are responsible for managing their forest when it is damaged by natural hazards, such as storms (Swedish Gov.…”

The Role of Highly-Resolved Gust Speed in Simulations of Storm Damage in Forests at the Landscape Scale: A Case Study from Southwest Germany

“…This effect might be due to higher drag of evergreen conifers in winter when most high-impact storms occur in the study area [55] while broad-leaved tree species are leafless [46,56,57]. [46,56,57]. A map of the modeled proportions of endemically storm-damaged timber (Figure 15) shows that the highest DAM mod,endemic -values (up to 55%) occur mostly in the northern Black Forest in exposed areas at high elevations.…”

“…The median values of DAM OOB are always lowest for mixed forests (between DAM OOB,30yr = 0.15 and DAM OOB,5˚= 0.24) and highest for conifers (between DAM OOB,30yr = 0.26 and DAM OOB,5* = 0.47). This effect might be due to higher drag of evergreen conifers in winter when most high-impact storms occur in the study area [55] while broad-leaved tree species are leafless [46,56,57]. [46,56,57].…”