Tree Regeneration Structure Following Beech Bark Disease-Motivated Harvests: Factors Associated with Patterns and Management Implications

In the northern Appalachian region of North America, mortality of mature American beech (Fagus grandifolia Ehrh.) via the introduced beech bark disease (BBD) can result in dense thickets of beech saplings that inhibit the regeneration of other species. It is unknown if similar structures characterize more recently infested managed forests in the Great Lakes region. If these dense beech sapling layers do exist, management would be aided by knowing which site/regional factors they are associated with and by identifying particular sapling structures that may threaten the sustainability of these forests under current management paradigms. To examine these patterns, we used a natural experiment with sample plots in 69 unevenly aged, selection silviculture-managed, maple (Acer spp.)-dominated northern hardwood stands. Our stands were dispersed across northern Michigan, USA and had undergone BBD-motivated partial harvests favoring beech removal (mean = 5.5 years before measurement). In each stand, we quantified tree regeneration structure in relation to winter deer use (fecal pellet count density), site quality (habitat type), geographic region (Eastern Upper Peninsula and Northern Lower Peninsula), and multiple measures of overstory stand density. We also examined the density effects of taller regeneration strata on subordinate strata. Across sites, the small sapling recruit class (i.e., >137 cm tall and <5 cm diameter at 137 cm tall) was dominated by beech and was often dense (44% of subplots > 2000 stems ha−1 and 16% of subplots > 5000 ha−1) but never exceeded the > 10,000 stems ha−1 reported in the northern Appalachian region. Beech sapling density was higher in the Northern Lower Peninsula, on lower quality sites, at lower postharvest overstory densities, and on sites with higher densities of preharvest overstory beech. In contrast to the beech-dominated small sapling recruit class, seedlings (i.e., <25 cm tall) were generally more species diverse than sapling strata and were dominated by maple species. Although generally dense, seedling density was negatively related to small sapling recruit density, suggesting that saplings may suppress the seedling stratum. The general pattern for the small sapling recruit layer of browsing-insensitive beech (and ironwood, Ostrya virginiana Mill. K. Koch) dominance and low representation of browsing-sensitive species (e.g., Acer spp.) circumstantially supports the notion that regeneration structure is heavily influenced by deer. However, current deer use was generally low in our stands, and relationships with tree regeneration structure were weak. Instead, regeneration structure is likely shaped by a combination of factors operating at long time scales (i.e., legacies of deer browsing pressure, selection silviculture (given beech and ironwood are shade tolerant), overstory composition, and site quality) and by those effects that are more proximal, such as postharvest overstory density. Minimum stocking criteria for species considered desirable for management (e.g., sugar maple and Acer saccharum Marshall) suggest many stands are inadequately stocked in the sapling recruit classes. Although future regeneration dynamics are unclear, current patterns suggest that many stands with high beech/ironwood small sapling recruit densities may require management intervention to overcome insufficient recruitment of species targeted for management.

Five Decades of Structural and Compositional Changes in Managed and Unmanaged Montane Stands: A Case Study from South-East Europe

The recent research has indicated that restoration of old-growth attributes such as large-sized living trees and snags contributes to sustaining biodiversity on the landscape level. The extent to which these attributes are restored, maintained, or diminished by total salvage logging, selection silviculture, and strict protection has been partly investigated in the past. However, studies examining the influence of partial salvage logging are largely absent. Thus, we compared long-term structural and compositional changes in three montane beech-fir-spruce stands in Serbia that were exposed to different management regimes for five decades (partial salvage logging, selection silviculture, and strict protection). Tree species composition of partly salvaged stand and selection stand significantly differed from that in the adjacent unmanaged stand. However, the diameter distributions of compared stands often exhibited the same structural forms in certain periods, despite the greater share of large-size trees in the unmanaged stand. The study indicated that managing for old-growth attributes such as large trees may be possible by applying not only rotated sigmoid and negative exponential structures, but also the increasing-q diameter structure as high basal areas in studied beech-fir-spruce stands did not impair the ingrowth of young trees when conifers dominated the upperstory. The study further revealed that partial salvaging may serve as a sound alternative to promoting old-growth attributes such as large veteran trees and snags.

Effects of basal area on survival and growth of longleaf pine when practicing selection silviculture

Aim of study: Uneven-aged (UEA) management systems can achieve multiple-use objectives, however, use of UEA techniques to manage longleaf pine (Pinus palustris Mill.) forests are still open to question, because of the species’ intolerance of competition. It was our aim to examine the influence of different levels (9.2, 13.8 and 18.4 m2 ha-1) of residual basal area (RBA) on longleaf pine seedling survival and growth following three growing seasons.Area of study: This study was conducted at the Escambia Experimental Forest, located on the Southern Coastal Plain of Alabama, in the southeastern United States.Material and Methods: Selection silviculture was implemented with the Proportional-Basal Area (Pro-B) method. Prescribed burning was conducted before seed dispersal and in the second year after germination. Photosynthetically active radiation (PAR) was measured under the canopy in the study plots. Survival and growth of longleaf pine seedlings were observed for three growing seasons.Main results: An inverse relationship was found between the number of germinants and RBA, but the mortality of germinants and planted seedlings was not affected by RBA. At age three, an inverse relationship was observed between root-collar diameter (RCD) growth of the germinants and RBA, but RCD growth of planted seedlings was not affected by RBA. Most of the study plots contained more than the projected number of seedlings needed to sustain the target diameter structure.Research highlights: Long-term continuous monitoring of seedling development and recruitment into canopy is required to determine the efficacy of UEA management. However, current data suggest that UEA methods may be a viable alternative to the use of even-aged (EA) methods in longleaf ecosystems.

La forêt des Erses, laboratoire du contrôle et patrimoine exceptionnel

The forest of Les Erses: a monitoring laboratory and an outstanding heritage The forest of Les Erses is situated at an altitude of 1100 m in the Jura mountains in Switzerland. It contains mixed stands of varying degrees of irregularity, and since 1889 has been the subject of uninterrupted records made by the pioneers of selection silviculture by the check method, Henry Biolley and William Borel, and then by the foresters of the Service of forests, wildlife and nature of the canton of Vaud. Since 1967, monitoring of individual stems of over 10 cm diameter in 59 permanent sample plots has demonstrated a positive trend in total wood production, and in stem diameter. This is probably an effect of global warming and improvement in the soils freed from grazing pressure. The processes of recruitment, growth and removal of the stems are complex: however, the relevance of the models used by the canton of Vaud to manage the forests in a sustainable way has been demonstrated. Although silvicultural objectives vary according to technical progress, the interests of the owners, the needs of society and, today, climate change, monitoring the development of forest stands is the core of a responsible sustainability policy. The concepts and enquiries of Biolley and Borel are still relevant after 120 years of silvicultural history in the forest of les Erses, even though today's concepts of monitoring have gone beyond the narrow frame in which the pioneers developed it.