Managed Forest Stands Research Articles

TreeCompR: Tree competition indices for inventory data and 3D point clouds

Abstract In times of more frequent global change‐type droughts and associated tree mortality events, competition release is one silvicultural measure discussed to have an impact on the resilience of managed forest stands. Understanding how trees compete with each other is therefore crucial, but different measurement options and competition indices (CI) leave users with a difficult choice, as no single competition index has proven universally superior. To help users with the choice and computation of appropriate indices, we present the open‐source TreeCompR package, which handles 3D point clouds and classical forest inventory data, enabling the calculation of both innovative point cloud‐based indices and traditional distance‐dependent indices. It serves as a centralized platform for exploring and comparing different CIs, allowing users to test and select the most suitable CI for their specific research questions within a common interface. To evaluate the package, we used TreeCompR to quantify the competition situation of 307 European beech trees from 13 sites in Central Europe. Based on this dataset, we discuss the interpretation, comparability and sensitivity of the different indices to their parameterization and identify possible sources of uncertainty and ways to minimize them. The compatibility of TreeCompR with different data formats and different data collection methods makes it accessible and useful for a wide range of users, specifically ecologists and foresters. Due to the flexibility in the choice of input formats as well as the emphasis on tidy, well‐structured output, our package can easily be integrated into existing data‐analysis workflows both for 3D point cloud and classical forest inventory data.

Effect of the irregular shelterwood system on soil organic carbon stock and soil quality of Shorea robusta Gaertn. f. forest in Nepal

The effective management of forests relies on the crucial role played bysilvicultural systems. However there exist a significant knowledge gap regarding impact of these systems in Nepalese forests. Therefore, this research was conducted to assess the effects of the forest management activities under irregular shelterwood system on soil organic carbon (SOC) stock and the overall soil quality of Sal (Shorea robusta Gaertn. f.) forests in Terai region of Nepal. Stratified random sampling method with 1.67 % sampling intensity was adopted in this study where management of stands was used as basis of strata. A total of 30 composite soil samples (15 each from managed and unmanaged forest stands) were collected from a depth of 0–30 cm, taken from the four corners and the center of each plot. Soil quality index (SQI) method was used for soil quality assessment using indicators on the basis of prior studies conducted in Nepal. Our study found significant difference in soil parameters except organic carbon, pH, silt, and clay among the managed and unmanaged forest stands (p < 0.05). SOC stock of unmanaged forest stands (48.87 ± 1.34 ton ha−1) was significantly greater than managed forest stands (27.76 ± 1.27 ton ha−1). Similarly, unmanaged forest stands demonstrated better soil quality with higher SQI value (0.66) than managed forest stands (0.50). This negative impact of irregular shelterwood silviculture system highlights the necessity for management interventions to enhance SOC stock and overall soil quality. To establish a robust conclusion, further replication of similar studies at different soil depths and in other management regimes, along with longitudinal studies, is essential.

Nová paleobotanická data prokazují původní status modřínu opadavého (Larix decidua Mill.) v severních Čechách

Using pollen analysis, phytolith analysis and radiocarbon dating of newly discovered sedimentary archives, here we prove the native status of European larch (Larix decidua Mill.) in two sandstone rocky areas of north Bohemia (Czech Republic). At the end of the Last Ice Age and at the beginning of the Holocene, European larch was relatively common in Central Europe. In most critical period of the Middle Holocene, it demonstrably retreated to exposed rocky habitats, but did not become completely extinct. In the form of relict populations, it survived locally until the modern era, when non-native larch types were artificially introduced into managed forest stands. Our findings call for a radical rethinking of the approach to larch by both foresters and nature conservation authorities. In the future, it is primarily necessary to search for and protect the remnants of its original gene pool.

Legacies of forest harvesting on plant diversity and plant community composition in temperate deciduous forest

AbstractAimsTo conserve forest natural heritage, sustainable forest harvesting requires the recovery of plant diversity and ecosystem functions following management. There is a need to clarify the temporal dynamics of plant diversity following harvesting, for both even‐aged and uneven‐aged silvicultural systems. To achieve this goal, the temporal dynamics of plant diversity in the herb layer were measured in unmanaged forests (control) and along a chronosequence (&lt;5 years, 15 years and 30 years after harvesting) for even‐aged and uneven‐aged managed forests.LocationHardwood forest of southern Quebec, Canada.MethodsPlant diversity, plant community composition and ecosystem functioning were investigated using metrics exploring richness, evenness and disparity diversity components, and included two scales of diversity partitioning (alpha and beta). Shrub–canopy layer, forest tree species composition and structure, and total forest basal area were also measured.ResultsIn both uneven‐aged and even‐aged managed forest stands, we found: (a) a substantial decrease in mean plant phylogenetic diversity compared with unmanaged forest, even 30 years after harvesting (i.e., decrease of 16% and 22%, respectively); and (b) lowest plant alpha‐diversity in the herb layer 15 years after harvesting. Modification of community composition based upon dissimilarity (beta‐diversity) metrics demonstrated more numerous effects of even‐aged management than uneven‐aged management. For forest composition and structure, plant community and plant traits, dissimilarity relative to the unmanaged control was highest 5 years after even‐aged management. Trait‐based communities were more similar to unmanaged forest at the intermediate levels of forest density (i.e., ~20 m2/ha) that were found 5 years after uneven‐aged management.ConclusionsForest management clearly affected diversity, community composition and ecosystem functions along the chronosequence, highlighting the strongest effects of more intensive management (i.e., even‐aged) and the need to improve the sustainability of forest management.

Soil Organic Matter Mineralization as Driven by Nutrient Stoichiometry in Soils Under Differently Managed Forest Stands

Nutrient contents of soil organic matter in forests vary with regional differences in soil types, and can be modified by forest management. Variation of organic carbon (OC)-to-nutrient ratios in soils supposedly alters microbial carbon and nutrient use efficiencies and the rates of OC-to-nutrient mineralization. Here, we studied mineralization rates of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) for topsoil samples from differently managed forest plots in Germany. Samples were incubated for two weeks in microlysimeters under controlled conditions. CO2 respiration, leachable dissolved organic carbon (DOC), nitrate (NO3-), ammonium (NH4+), sulphate (SO42-) and phosphate (PO43-) were determined as net organic C (OC) and nutrient mineralization rates. We hypothesized that in soils with high C-to-nutrient ratios, soil microbes may mobilize relatively more OC as CO2 or DOC than nutrients to meet their nutrient and that forest type influences the stoichiomertry of SOM mineralization by altering the ratios of C-to-nutrients in soils. Results showed that CO2-release rates were proportional to soil OC, but when normalized to microbial biomass C, they increased, similar to DOC leaching rates, with soil OC-to-N ratios. However, higher soil OC-to-nutrient ratios did not go along with reduced nutrient leaching. Instead, when normalized to soil OC, the largest amounts of N, P and S were leached in the most nutrient poor region, so that sites with highest soil OC-to-nutrient ratios had the smallest OC-to-nutrient mineralization ratio. Forest type affected soil stoichiometry only in the most nutrient poor region with smaller OC-to-nutrient ratios and OC-normalized DOC leaching rates under deciduous than coniferous forest sites. However, in the two other study regions tree species had a significant effect on N and S leaching rates and the ratio of OC-to-nutrient leaching despite similar stoichiometry. Overall, our study suggests that increasing nutrient scarcity enhances microbial based CO2 and DOC production, possibly because of increased energy demand for enzyme production to reach and mobilize nutrients, thereby allowing for high nutrient leaching rates despite small total stocks. Forest management affected OC-to-nutrient mineralization rates mostly via tree species selection, but differences were not caused by soil stoichiometry but rather other ecological differences between forest types.

Testing the Effect of Snag and Cavity Supply on Deadwood-Associated Species in a Managed Boreal Forest

Standing deadwood is an important attribute of old-growth boreal forests and it provides essential microhabitats for deadwood-associated species. In managed boreal forests, short rotations tend to limit the amount and diversity of standing deadwood. This study evaluates if the anthropogenic supply of deadwood attributes through tree girdling or by providing nest boxes may favor deadwood-associated species. We studied the short-term response of saproxylic beetles, foraging woodpeckers, and secondary cavity users to snag and cavity supply in 50 to 70-year-old black spruce stands. In spring 2015, we girdled 8000 black spruce according to two spatial distributions (uniform and clustered), and we also installed 450 nest boxes of six different sizes at three distances from the forest edge. Using trunk window traps, we captured significantly more beetles in sites with girdled trees than in control sites in both 2015 and 2016. We also recorded a trend of a greater abundance of beetles in clusters of girdled trees than within uniformly distributed girdled trees. Trypodendron lineatum (Oliver) dominated beetle assemblages, representing 88.5% of all species in 2015 and 74.6% in 2016. The number of beetles captured was 7× higher in 2015 than in 2016. In contrast, we observed greater amounts of woodpecker foraging marks in fall 2016 than in either fall 2015 or spring 2016. Woodpeckers foraged significantly more in clusters of girdled trees than within uniformly distributed girdled trees. Woodpeckers’ foraging mark presence was positively associated with the proportion of recent cuts at 1 km around the study sites. Five Boreal Chickadee (Poecile hudsonicus Forster) pairs used nest boxes and occupied smaller box sizes that were located away from the forest edge. Our study showed that structural enrichment can be effective in rapidly attracting deadwood-associated species within managed forest stands.

Stand structure drives disparities in carbon storage in northern hardwood-conifer forests

Elements of forest structure are fundamentally associated with an array of ecosystem services and habitat characteristics. However, forest structure varies, in particular, through interactions with natural and human disturbances. Both variation in structural characteristics and associated relationships with ecosystem service outcomes have been poorly explored in mature, secondary forests redeveloped since 19th century agricultural abandonment in the eastern United States. Our study addressed this uncertainty focusing on carbon storage as an important climate regulation service. We conducted an inventory of 45 plots sharing similar land use history (i) to identify differences in forest structure, and (ii) to investigate links between stand structure and aboveground carbon storage. We derived 19 structural attributes and used these in Agglomerative Hierarchical Clustering (AHC) to categorize structurally different groups. Subsequently, we analyzed carbon density in each cluster and employed a random forest algorithm to derive partial effects of structural attributes on carbon storage.We found a distinctive disparity in forest structure inferred from two hardwood-dominated and one softwood-dominated clusters. Nine variables (cavity tree density, conifer ratio, foliage height index, gap area, live basal area, species diversity, variation in heights and diameters, and vertical shrub cover) explained significant differences between these clusters. Carbon storage varied markedly, and was highest in the softwood cluster. Structural complexity was overall positively associated with carbon storage, whereas this effect was more distinctive in hardwood compared to softwood-dominated forests. In particular, five variables exhibited a positive (conifer ratio, diameter variation, dead basal area, large live trees, and live basal area), one a negative (live tree density), and two (dead tree density and species diversity) a mixed relationship with carbon storage. Despite only moderate variation in climatic conditions across the investigated plots, we found a strong sensitivity of carbon storage to mean annual temperature. In contrast, annual precipitation and topography had no effect on carbon storage. The link between structural complexity and carbon storage suggests a high potential to actively increase forest carbon density. Based on our findings, a variety of options are available to enhance forest structure, and thus to improve carbon storage in managed forest ecosystems. These include, for instance, increasing the variability in tree dimensions and fostering large live trees which may improve niche complementarity. Increasing structural complexity in managed forest stands may thus improve buffering of potentially negative impacts of climate change on carbon stocks.

Structural and compositional dynamics of strictly protected woodland communities with silvicultural implications, using Bia\u0142owie\u017ca Forest as an example

• Key messageLong-term strict protection of woodland communities may lead to their compositional simplification and homogenisation.• ContextIn the past, it has often been postulated that structures and processes typical for natural forests should be mimicked by silvicultural activities in the case of managed tree stands.• AimsTo determine which features and traits of natural woodland communities (alongside typical old-growth attributes) should be imitated in managed forests, as well as which should not (and for what reasons).• MethodsTree data from five permanent study plots (of a total area of 15.44 ha) established in 1936 in the core area of the Białowieża National Park (NE Poland) are used to calculate several quantitative indices describing the temporal dynamics (in terms of stand structure and composition) of eight major woodland community types.• ResultsMost structural attributes revealed rather high stability over time. In contrast to these, during the observation period, noticeable changes in the composition of particular Białowieża woodland communities have been taking place, related to declining occurrence and reduced roles characteristic for a large number of tree species.• ConclusionIn many ways, natural forests can serve as an important model for managed forest stands. However, in certain circumstances, silvicultural treatments counteracting natural developmental trends may appear to be indispensable, especially when more diverse and stable tree species composition (at a given spatial and temporal scale) is indicated or desirable.

Effects of abiotic environmental factors and land use on the diversity of carrion-visiting silphid beetles (Coleoptera: Silphidae): A large scale carrion study.

Anthropogenic land use causes global declines in biodiversity. Despite the knowledge that animal carrion is the most nutrient-rich form of dead organic matter, studies on landscape and local scales determining whether and the means by which land use intensity influences the diversity of the carrion-associated insect fauna are globally scarce. We investigated the effects of land use intensity and abiotic and biotic environmental factors on the abundance, species richness, and diversity of the important ecosystem-service-providing silphid beetle taxon (carrion beetles) in three regions of Germany. In 61 forest stands distributed over three geographically distinct regions in Central Europe, we trapped silphid beetles on exposed piglet cadavers during late summer. In all three regions, higher ambient temperatures and higher fine sand contents were associated with the abundance of the silphid beetle taxa. The carrion community silphid diversity was negatively affected by an increase in mean ambient temperature in all three regions. Although management intensity in forests did not affect the overall abundance of Silphidae, the abundance of Nicrophorus humator decreased significantly with higher forest management intensity across all three regions. Unmanaged and age-class forests showed a higher abundance of N. humator compared with extensively managed forest stands. These findings indicate that N. humator has potential as an indicator species for anthropogenic disturbances in forests. Overall, the direct responses of the silphid beetle community to diverse soil characteristics underline soil as an important factor determining the abundance and diversity of necrophagous carrion beetles in Central Europe. To protect these valuable ecosystem-service providers, forest-management-induced soil modifications need to be paid close attention.

Tree and stand structure of the non-native Pinus contorta in relation to native Pinus sylvestris and Picea abies in young managed forests in boreal Sweden

ABSTRACTManaged forest stands are typically younger and structurally less diverse than natural forests. Introduction of non-native tree species might increase the structural changes to managed forest stands, but detailed analyses of tree- and stand-structures of native and non-native managed forests are often lacking. Improved knowledge of non-native forest structure could help clarify their multiple values (e.g. habitat for native biodiversity, bioenergy opportunities). We studied the structural differences between the introduced, non-native Pinus contorta and the native Pinus sylvestris and Picea abies over young forest stand ages (13–34 years old) in managed forests in northern Sweden. We found that P. contorta stands had greater mean basal areas, tree heights, diameters at breast height, and surface area of living branches than the two native species in young stands. The surface area of dead attached branches was also greater in P. contorta than P. abies. Although this indicates greater habitat availability for branch-living organisms, it also contributes to the overall more shaded conditions in stands of P. contorta. Only one older 87 years old P. contorta stand was available, and future studies will tell how structural differences between P. contorta and native tree species develop over the full forestry cycle.

Ecological Traits Fail to Consistently Predict Moth Species Persistance in Managed Forest Stands

Ecological Traits Fail to Consistently Predict Moth Species Persistance in Managed Forest Stands

Interactions between windthrow, bark beetles and forest management in the Tatra national parks

Natural disturbances such as windthrow and bark beetle Ips typographus L. outbreak often affect protected areas with non-intervention type of management located in close proximity to managed forest stands. This raises concerns about the migration of the beetle outbreak from non-intervention zones to adjacent managed forests. In this study we analyzed the spatiotemporal dynamics of large-scale disturbances by intervention and non-intervention type of management in the Tatra mountains (Central Europe). We collected a time series of Landsat images from 2003 to 2014, and applied maximum likelihood classification to map the extent of forest, windthrow, clear-cuts, beetle outbreak and fire. Our classified maps achieved high overall accuracies: 0.93±0.03⩽OA⩽0.96±0.03. The extent of forest declined over the study period. We found higher rate of beetle induced tree mortality in non-intervention versus intervention zone. Within two growing seasons after the windthrow, beetle infestation occurred in close proximity to uncleared windthrow (<∼250m), which suggest the positive effect of salvage logging (removal of windthrown trees) on lowering the risk of beetle outbreak. The two times higher sum of disturbances in intervention then in non-intervention zone indicated the limited impact of sanitation felling (removal of standing beetle infested trees) to reduce beetle population. However, sanitation felling highly contributed to the decline of the forest cover. Overall, our results document the dynamics of windthrow, bark beetle and clear-cuts by type of management, and limited impact of logging activities in reducing beetle outbreak in neighboring areas with intervention and non-intervention type of management.

Climate change impact assessment—A simulation experiment with Norway spruce for a forest district in Central Europe

Projected climate change implies that site conditions can no longer be expected to remain constant over a tree’s lifetime. The fast and complex changes in site characteristics and growth patterns diminish the value of traditional knowledge and profoundly alter the conditions of forest management. One way to tackle the inherent uncertainties are simulation studies addressing these new dynamics and mechanisms. The aim of this study is to present such a simulation model system comprising various established and validated process-based and statistical models assessing the complex and dynamic response of a forest stand to climate change.For a given climate scenario, these coupled models estimate the potential growth and yield and various risks considering changing site and stand conditions. As an example, the model system is applied to managed forest stands of Norway spruce (Picea abies (L.) H. Karst.) in a forest district located in central-western Germany. For the changing climate conditions according to SRES B1 and A1B, the model results suggest a positive effect on the site index and, by contrast, a negative impact on tree survival of increasing risks regarding drought stress mortality, wind damage, and bark beetle infestation given the climate change scenario. The annual contribution margin of timber production under consideration of damage risks by drought stress mortality, wind, and bark beetle infestation reveals that, in this case, the increased growth is able to compensate for the higher risks with few exceptions. Furthermore, we discuss the advantages and challenges of employing a dynamic complex simulation model system for climate change impact assessment based on high-resolution climate data.

INVISTIGATION ON CANOPY HEIGHT AND DENSITY DIFFERENTIATIONS IN THE MANAGED AND UNMANAGED FOREST STANDS USING LIDAR DATA (CASE STUDY: SHASTKALATEH FOREST, GORGAN)

Abstract. Forest management plans are interesting to keep the forest stand natural composite and structure after silvicultural and management treatments. In order to investigate on stand differences made by management treatments, comparing of these stands with unmanaged stands as natural forests is necessary. Aerial laser scanners are providing suitable 3D information to map the horizontal and vertical characteristics of forest structures. In this study, different of canopy height and canopy cover variances between managed and unmanaged forest stands as well as in two dominant forest types were investigated using Lidar data in Dr. Bahramnia forest, Northern Iran. The in-situ information was gathered from 308 circular plots by a random systematic sampling designs. The low lidar cloud point data were used to generate accurate DEM and DSM models and plot-based height statistics metrics and canopy cover characteristics. The significant analyses were done by independent T-test between two stands in same dominant forest types. Results showed that there are no significant differences between canopy cover mean in two stands as well as forest types. Result of statistically analysis on height characteristics showed that there are a decreasing the forest height and its variance in the managed forest compared to unmanaged stands. In addition, there is a significant difference between maximum, range, and mean heights of two stands in 99 percent confidence level. However, there is no significant difference between standard deviation and canopy height variance of managed and unmanged stands. These results showd that accomplished management treatments and cuttings could lead to reducing of height variances and converting multi-layers stands to two or single layers. Results are also showed that the canopy cover densities in the managed forest stands are changing from high dense cover to dense cover.

Decline in bryophyte diversity in predominant types of central European managed forests

The extent to which the diversity of forest-inhabiting bryophytes is related to forest management practices has been the subject of a recent study. However, the question of how these practices affect the spatial distribution pattern of bryophyte diversity throughout managed European forests remains unanswered. We surveyed bryophyte diversity in six large forest complexes in the Czech Republic. Our sites encompass a range of managed forest stands (including various temporal phases such as clearings and young forests) across a gradient of environmental conditions. In general, the bryophyte species richness in managed forests was less than in unmanaged forests. Only unmanaged forest stands that provided suitable substrates such as large dead woody debris and large diameter beeches (Fagus sylvatica) were able to support rare bryophyte species. Mature managed forests with simplified tree structure, dominated by either deciduous or coniferous species shared similar bryophyte species richness (α-diversity) and pool (γ-diversity). It appears that forest management, which leads to the loss of old-growth forest attributes, may result in low-diversity bryophyte communities regardless of tree species composition. Nevertheless, bryophyte species turnover (β-diversity) was spatially uniform in mature managed forests dominated by conifers, but quite variable in those dominated by deciduous tree species. Managed forests with diverse tree structure and composition approximated the species pool size of unmanaged forests, in spite of their small contribution to the total area of managed forests. Hence, forest management as commonly applied in the managed forests of the Czech Republic does not appear to be conducive to the persistence of diverse bryophyte assemblages. We suggest that some essential changes in forest management practices are necessary to maintain the conditions favorable to the preservation of bryophyte diversity in central European forests.

Functioning of Ecotones — Spiders and Ants of Edges Between Native and Non-Native Forest Plantations

Habitat edges are regarded as important components of heterogeneous landscapes. Diverse theories exist about the diversity and functional role of edges, and no generalisation have been possible so far, thus case studies are important for better understanding the landscape scale processes. Forest management highly modified the structure and tree species composition of the European forests. The sylvicultural intensification resulted in the rise of the proportion of non-native, intensively managed forest stands. In the present study we explore the response of spider and ant assemblages to forest stand type and the edge effect between native poplar and nonnative conifer plantations in Hungary. We applied pitfall traps to sample the ground-dwelling spiders and ants. Four plots consisting of the two forest types and the transition zones between them were selected. Five transects for each replicated plot were sampled. We identified the significant indicator species of the different habitat types. We found significant differences in the species richness (i.e. number of species) of ants and spiders of the different habitat types. We detected intermediate spider species richness at the edge indicating that edges separate a higher quality habitat from one that has lower resource quality; however, the species richness of ants was the highest at the edge and did not differ between the two forest types. The positive impacts of edge was found due to presence of generalist and grassland species at the edge and presumably edges separate patches that provide complementary resources also increasing the number of ant species.Our results indicate that forest type affects the species compositions of ground-dwelling spiders and ants. Our study also shows that habitat type had a major effect on the species richness and composition of spider and ant assemblages, suggesting that local forestry management plays a crucial role in preserving the native invertebrate fauna of forests.

Using a segmented logistic model to predict trees to be harvested in forest growth forecasts

Aim of the study: Predicting future harvested trees is a prerequisite to growth forecasts in managed forest stands. While harvest algorithms have been traditionally used, statistical harvest models could be an interesting alternative approach. The objective of this study was to fit statistical harvest models for different partial cutting treatments.Area of study: The study has been carried out in the province of Quebec, Canada.Material and Methods: Data from provincial control survey were used to fit harvest models for three different partial cutting treatments. A two-segment logistic modelling approach was used. The harvest models were designed to be compatible with the ARTEMIS growth simulator, which is currently in use in this province. Main results: The results showed that the probability of being harvested is different across the treatments and primarily depends on tree diameter at breast height and species. In selection cutting treatments in particular, trees close to the merchantable limit (e.g., 23 cm in this study) tended to be less frequently harvested than those with smaller or larger diameters, yielding a sinusoidal pattern that was well captured by the segmented approach. Research highlights: Although the models were of average accuracy as indicated by fit statistics, they made it possible to compare different scenarios in terms of productivity and rotation length when coupled with the ARTEMIS growth simulator. Moreover, compatibility requirements between the simulator and the harvest models appeared to be a major limitation in some cases.Keywords: Harvesting; statistical model; segmented approach; growth forecasts; managed stands.

Survey of the Patterns of Nest Box Use Among Squirrels (Sciuridae) in Managed Forest Stands in Clinton County, New York

Artificial habitat enhancements are important forest structural components that can increase the survival of squirrels (Sciuridae) and thus warrant study. Investigations of squirrel nest box usage can provide useful demographic and community information such as occupancy rates, litter size, habitat preference, species richness and abundance estimates. This artificial nest box study investigated the nesting patterns of squirrels from late winter through early fall 2011 in managed forest stands in Clinton County, New York. Squirrels are sensitive to forest disturbance, hence we compared sites of varying silvicultural activity (e.g., managed for production of timber or maple syrup versus an undisturbed reference stand). A total of 48 nest boxes were constructed and monitored across three separate sites (e.g., reference, logged, and sugaring). Prior research suggested that occupancy may be a function of nest box height (~3.5m and ~5m) and site-specific tree cavity/snags/drey abundance, thus height preference and alternative nesting options were monitored in the survey and analyzed to report detection probability and occupancy estimates in Program Presence. Visual confirmation of northern flying squirrels (Glaucomys sabrinus Shaw) was made in 81%, 44%, and 13% of the nest boxes in the reference, logged, and sugar site, respectively. Approximately 79% of the nest boxes showed evidence of wildlife visitation (e.g., scat, crushed seeds, or nesting material). Additionally, 87% of the high boxes (5m) versus 71% of the low boxes (3.5m) were utilized, and 17% of all occupancies contained multiple individuals. This survey provides additional multi-season occupancy data for an elusive mammal species under managed habitat regimes. We recommend that management plans include a wildlife habitat component that maintains snag trees and live cavity-trees in forest stands. When appropriate, stand management plans could also include installing habitat enhancement structures such as artificial nest boxes for squirrels.

Roundwood pre-grading with longitudinal acoustic waves for production of structural boards

The assessment of timber quality at any stage of the production chain promises to be an advantage for the forest and timber industry. This paper presents results of wood pre-grading by means of the dynamic modulus of elasticity, which was performed along the complete processing chain—from standing trees to sawn timber. The measurements were conducted on 154 forty-year-old trees of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) from two forest experimental stands in Southern Germany. Long logs of about 13 m were bucked into short logs of 4.1 m; the dataset contained 1,820 boards cut out of 332 short logs. Pre-grading was performed at different levels: standing tree, long log, and short log. The boards were machine strength graded by a ViSCAN-COMPACT grading machine. The investigation showed high correlations between different stages in the production chain of timber. For strength classes C24 and C30 an increase in yield of about 10 percentage points by rejecting the 25 % worst logs (short or long) was observed. It did not matter if pre-grading was realized at the stage of long logs or short logs. However, methods of pre-grading at standing tree must be improved to obtain reliable prediction of dry sawn timber quality of managed forest stands (r2 = 0.17).

Is randomized branch sampling suitable to assess wood volume of temperate broadleaved old-growth forests?

Old-growth forests are characterized by the presence of large and very large trees. The estimation of their wood volume and biomass is essential in order to monitor the ecological processes in these stands and their contribution to carbon cycle. However, conventional wood volume estimation techniques based on mensuration of stem diameter at breast height and tree height is most often unfeasible for large and very large trees in old-growth forests because volume models or tables are usually elaborated from trees of smaller size grown up in regularly managed forest stands. Random Branch Sampling (RBS) is often proposed as a possible estimation alternative under such conditions. Starting from the ground level some of the parts of the main trunk and of the branches are sampled and measured to estimate the overall wood volume (or other biophysical variables). The application of RBS in old-growth forests, where tree cutting is usually forbidden or very difficult, requires that the crown of the tree can physically be reached to measure the sampled parts. We argue that under such conditions it is usually preferable to fully measure all the components of the tree crown because RBS estimates are not precise if based on only one sampling path and that, on the other hand, measuring the main trunk and all the branches by tree-climbing consumes the same time as replicating several RBS paths on the same tree. To demonstrate our hypothesis we selected 16 large beech trees located in the old-growth forest of Mount Cimini in Central Italy. Using a modern tree-climbing approach the main trunk and all the branches were measured and recorded in the field. The database was used to simulate RBS paths. Real values from volume census were contrasted with estimates based on RBS. On the whole, RBS estimates based on one single path prove to be highly imprecise. Even for trees characterized by a rather regular form, at least three RBS paths should be repeated on the same tree to maintain the relative standard error under or near 15%. This paper introduces the problem and describes the experimental test. The results are discussed under the perspective of standardized application of the proposed methodology.