Major disturbances test resilience at a long‐term boreal forest monitoring site

Abstract

The impact of disturbances on boreal forest plant communities is not fully understood, particularly when different disturbances are combined, and regime shifts to alternate stable states are possible after disturbance. A long‐term monitored semi‐natural forest site subject to intense combined storm and bark beetle damage beginning in 2005 provided an opportunity to investigate the postdisturbance development of the vegetation community. Previous studies suggest that a shift from Picea abies to Fagus sylvatica domination was possible. We analyzed pre‐ and postdisturbance vegetation data to investigate to what extent vascular plant species abundances, diversity, traits, and community composition have changed. We were particularly interested in differences between remaining apparently unaffected areas (potential refugia) and disturbed areas, and in signs of consistent change over time in community composition in response to disturbance that could indicate an impending regime shift. We found that the vegetation community present in the refuge areas has remained substantially intact through the period of disturbance. Nonrefuge areas diverged from the refuges in community composition and showed increased taxonomic and functional diversity. Despite this, and an increase in deciduous tree species (particularly F. sylvatica ), P. abies has shown strong postdisturbance regeneration. The refuges may be important in the apparent ongoing recovery of the disturbed areas to a P. abies‐ dominated state similar to that found predisturbance. This fast recovery is interpreted as evidence of a system resilient to a potential shift to a deciduous‐dominated state. Synthesis : Our results show that even powerful combined disturbances in a system with multiple stable states can be insufficient to initiate a regime shift. Resilience of the P. abies ‐dominated forest community is increased by the survival of refuge areas functioning as a form of ecological memory of the previous ecosystem state. The results also demonstrate the value of data generated by long‐term monitoring programs.

Weak recovery of epiphytic lichen communities in Sweden over 20 years of rapid air pollution decline

“…Interpretation of the Aneboda results is complicated by the extensive disturbances caused by storm and bark beetle damage at the site (Weldon & Grandin 2019). While there is an apparent large decline in the Hultengren sensitivity index and increase in N preference, these were not significant (although the large increase in variation may well be the reason for this lack of significance).…”

“…Lichen monitoring is conducted on five randomly selected mature trees (diameter breast height 40–80 cm) from four randomly selected monitoring plots. However, due to severe storm and bark beetle disturbance in 2005–2008 at the Aneboda site (Weldon & Grandin 2019) the trees selected for lichen monitoring are restricted to those monitoring plots that still have living trees. The lichen monitoring follows a repeated measure design with inventories of the same trees every fifth year, resulting in four inventories at each site, as of 2020.…”

Natural Disturbance Dynamics Analysis for Ecosystem-Based Management—FORDISMAN

“…The potential to support forest resilience to future disturbances can be enhanced by managing the biological components of ecosystem legacies [11,27,28]. For example, refuge areas in managed forest are suggested as mitigation to harmful effects of timber harvest or salvage [17,29].…”