Abstract
BackgroundIn recent decades the frequency and severity of natural disturbances by e.g., strong winds and insect outbreaks has increased considerably in many forest ecosystems around the world. Future climate change is expected to further intensify disturbance regimes, which makes addressing disturbances in ecosystem management a top priority. As a prerequisite a broader understanding of disturbance impacts and ecosystem responses is needed. With regard to the effects of strong winds – the most detrimental disturbance agent in Europe – monitoring and management has focused on structural damage, i.e., tree mortality from uprooting and stem breakage. Effects on the functioning of trees surviving the storm (e.g., their productivity and allocation) have been rarely accounted for to date.Methodology/Principal FindingsHere we show that growth reduction was significant and pervasive in a 6.79·million hectare forest landscape in southern Sweden following the storm Gudrun (January 2005). Wind-related growth reduction in Norway spruce (Picea abies (L.) Karst.) forests surviving the storm exceeded 10% in the worst hit regions, and was closely related to maximum gust wind speed (R2 = 0.849) and structural wind damage (R2 = 0.782). At the landscape scale, wind-related growth reduction amounted to 3.0 million m3 in the three years following Gudrun. It thus exceeds secondary damage from bark beetles after Gudrun as well as the long-term average storm damage from uprooting and stem breakage in Sweden.Conclusions/SignificanceWe conclude that the impact of strong winds on forest ecosystems is not limited to the immediately visible area of structural damage, and call for a broader consideration of disturbance effects on ecosystem structure and functioning in the context of forest management and climate change mitigation.
Highlights
Natural disturbances have been increasing in frequency and severity in forests around the world in recent decades [1,2]
Norway spruce increment dropped in all counties affected by Gudrun compared to pre-storm levels
Functional disturbance effects such as growth changes after wind events have to date received only limited attention in the literature. Such effects are currently neglected in the monitoring and economic assessment of wind damage in the context of forest management, which focus exclusively on structural effects [1,3,29]. While both positive and negative wind-induced growth changes have been reported at the level of individual trees [11,12,13,14,15,16,17,18], we have shown here that the storm Gudrun resulted in a pervasive and significant growth reduction in Norway spruce forests at the landscape scale
Summary
Natural disturbances have been increasing in frequency and severity in forests around the world in recent decades [1,2]. Disturbances by e.g., wildfires, insect outbreaks, and strong wind events are increasingly becoming a challenge for the sustainable management of forest ecosystems. Disturbance events can turn forests acting as a carbon (C) sink to the atmosphere into a C source [4,5]. They have the potential to strongly interfere with objectives of mitigating climate change through forest management. In recent decades the frequency and severity of natural disturbances by e.g., strong winds and insect outbreaks has increased considerably in many forest ecosystems around the world. Effects on the functioning of trees surviving the storm (e.g., their productivity and allocation) have been rarely accounted for to date
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