Vulnerability of uneven-aged forests to storm damage

Forest managers are often required to restore forest stands following natural disturbances, a situation that may become more common and more challenging under global change. In parts of Central Europe, particularly in mountain regions dominated by mixed temperate forests, the use of relatively low intensity, uneven-aged silviculture is a common management approach. Because this type of management is based on mimicking less intense disturbances, the restoration of more severe disturbance patches within forested landscapes has received little attention. The goal of this paper is to synthesize research on the restoration of forests damaged by disturbances in temperate forests of Slovenia and neighbouring regions of Central Europe, where uneven-aged silviculture is practiced. Research indicates that active management aimed at favouring mixed uneven-aged forest reduces the risk of disturbance and improves the resilience of stands. Salvage logging may have positive or negative effects on regeneration, much of which is due to the method applied and the quality of work. The most prominent factors that negatively affect restoration are: lack of advanced regeneration and decomposed woody debris, high altitude, steep slopes, dense ground vegetation, and overbrowsing. Planting or sowing should be applied in post-disturbance forests where many negative factors interact and where a high demand for sustainability of forest ecosystem services is present.

Section: Stand Structurementioning

confidence: 99%

Challenges for Uneven-Aged Silviculture in Restoration of Post-Disturbance Forests in Central Europe: A Synthesis

Diaci

Roženbergar

Fidej

et al. 2017

“…In fact, it was climate related damage to stands managed by uniform silvicultural systems that advanced the use of irregular forestry in the 19 th century as a result of the failure of the uniform system subject to storms [53]. Irregular stand structures appear to be more resilient to abiotic damage than even-aged stands and lower damage levels have been observed in irregular stands following storms in comparison with regular even-aged stands [54]. Dominant trees in irregular stands emerge earlier and develop deeper canopies than dominants in regular stands and, as a consequence, are exposed to bigger wind loads due to the greater crown size and over a longer period of time resulting in the development of stabilising features such as greater stem taper and stronger structural roots [55].…”

Section: Developing Irregular Stand Structuresmentioning

confidence: 99%

“…Mason [55] concluded that fully developed irregular stands in a 'balanced' condition would appear to be more resilient to wind damage than regular stands where exposure in moderate, but the difference is likely to be minimal where exposure is severe. Even where the balanced irregular condition exists, harvesting interventions have been found to cause a destabilising effect for a number of years [54]. However, where damage does occur in heterogeneous stands, much of the advanced regeneration will remain limiting the loss of forest cover.…”

Section: Developing Irregular Stand Structuresmentioning

confidence: 99%

Building Resilience into Sitka Spruce (Picea sitchensis (Bong.) Carr.) Forests in Scotland in Response to the Threat of Climate Change

Cameron

2015

Abstract:It is expected that a warming climate will have an impact on the future productivity of European spruce forests. In Scotland, Sitka spruce (Picea sitchensis (Bong.) Carr.) dominates the commercial forestry sector and there is growing pressure to develop alternative management strategies to limit potential economic losses through climate change. This review considers management options to increase the resilience of Sitka spruce dominated forests in Scotland. Given the considerable uncertainty over the potential long-term impacts of climate change, it is recommended that Sitka spruce should continue to be planted where it already grows well. However, new planting and restocking should be established in mixtures where silviculturally practicable, even if no-thin regimes are adopted, to spread future risks of damage. Three potentially compatible species with Sitka spruce are western hemlock (Tsuga heterophylla (Raf.) Sarg.), grand fir (Abies grandis (Lamb.) Lindl.) and Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and all form natural mixtures in its native range in North America. The predicted windier climate will require a range of management inputs, such as early cutting of extraction racks and early selective thinning, to improve stability. The potential to improve resilience to particularly abiotic damage through transforming even-aged stands into irregular structures and limiting the overall size of the growing stock is discussed.

“…For example, lower tree height-to-diameter ratios (H:D) may enhance windfirmness [13] in uneven-aged stands compared to even-aged stands, while partial harvestings, which may increase wind load [14] by leaving spaces between crowns, are repeatedly performed throughout the rotation in uneven-aged silviculture but are only optionally performed in even-aged silviculture. Moreover, comparing even-and uneven-aged silviculture is challenging, as some of the factors that would affect stand windthrow susceptibility may vary through time, especially across even-aged stand development [15].…”

Section: Introductionmentioning

confidence: 99%

Long-Term Susceptibility of Even- and Uneven-Aged Northern Hardwood Stands to Partial Windthrow

Nolet

Béland

2017

Abstract:While uneven-aged silviculture may appear preferable to even-aged silviculture in terms of stand susceptibility to windthrow (major wind damage), the scientific evidence is equivocal on this issue, because the two systems do not operate over the same time frame. The goal of this study was to evaluate the windthrow susceptibility of even-and uneven-aged stands over a 100-year period. Susceptibility to windthrow of North American hardwood stands was evaluated by coupling a stand growth model (Forest Vegetation Simulator, or FVS) to stem windthrow probability equations from the literature. This coupling was straightforward given that FVS provides the diameter at breast height (DBH) of each tree within a stand over the simulation period. Windthrow susceptibility equations also use DBH to calculate stem windthrow probability. Our results show that average loss due to windthrow under uneven-aged management can be twice that observed under even-aged management at moderate wind severity for sugar maple-dominated stands. This result should be interpreted with caution because of the impossibility in our simulations of considering differences in tree form development between the two approaches. Nevertheless, this study clearly shows that even-/uneven-aged silviculture comparisons should be made on a long-term basis since uneven-aged stands are continuously susceptible to windthrow, while even-aged stands tend to be little affected by windthrow in their early developmental stages.