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Aims: In temperate forests, small increases in winter temperature can lead to substantial decreases in snow accumulation, which may alter plant–consumer interactions such as seed predation. However, seed predation by small mammals may also be affected by local habitat structure (e.g., downed woody debris). We tested whether the effect of snow depth on seed predation by small mammals depends on habitat structure (woody debris) that may influence small-mammal foraging behavior. Location: Northern temperate forests in Wisconsin, USA. Methods: We performed a factorial manipulation of snow depth and woody debris presence at 10 sites that differed in site-level ambient woody debris. At these sites, we monitored seed removal of four temperate tree species (Abies balsamea, Acer rubrum, Acer saccharum, Pinus resinosa). Results: Mean rates of winter seed removal varied among species, as did the effects of snow depth and woody debris. The presence of woody debris decreased Abies balsamea seed removal in plots with snow removed. Regardless of woody debris, snow removal increased Acer saccharum seed removal. Acer rubrum seed removal was lowest at sites with high site-level woody debris volume, especially in plots with snow removed. Conclusions: Warming winter temperatures may amplify seed removal for some tree species, but local-scale heterogeneity in woody debris may modify these effects. Because the effects of woody debris and snow removal were much stronger for some tree species than others, changes in seed removal associated with reduced future snow cover or changes in forest management may accelerate regional changes in forest composition. [ABSTRACT FROM AUTHOR]

Winter is becoming warmer and shorter across the northern hemisphere, and reductions in snow depth can decrease tree seedling survival by exposing seedlings to harmful microclimates. Similarly, herbivory by small mammals can also limit the survival and distribution of woody plants, but it is unclear whether winter climate change will alter small‐mammal herbivory. Although small‐scale experiments show that snow removal can either increase or decrease both soil temperatures and herbivory, we currently lack snow‐removal experiments replicated across large spatial scales that are needed to understand the effect of reduced snow. To examine how winter herbivory and snow conditions influence seedling dynamics, we transplanted Acer saccharum and Tsuga canadensis seedlings across a 180 km latitudinal gradient in northern Wisconsin, where snow depth varied seven‐fold among sites. Seedlings were transplanted into one of two herbivory treatments (small‐mammal exclosure, small‐mammal access) and one of two late‐winter snow removal treatments (snow removed, snow unmanipulated). Snow removal increased soil freeze‐thaw frequency and cumulative growing degree‐days (GDD), but the magnitude of these effects depended on forest canopy composition. Acer saccharum survival decreased where snow was removed, but only at sites without conifers. Excluding small mammals increased A. saccharum survival at sites where the small‐mammal herbivore Myodes gapperi was present. Excluding small mammals also increased T. canadensis survival in plots with < 5 cm snow. Because variation in canopy composition and M. gapperi presence were important predictors of seedling survival across the snow‐depth gradient, these results reveal complexity in the ability to accurately predict patterns of winter seedling survival over large spatial scales. Global change scenarios that project future patterns of seedling recruitment may benefit from explicitly considering interactions between snow conditions and small‐mammal winter herbivory. [ABSTRACT FROM AUTHOR]

Guidelines for managing sugar maple-dominated forests by the single-tree selection method are well established and widely adopted. The forests of the Menominee Tribe in Wisconsin provide an opportunity to validate current guidelines by testing tree value and size/age relationships in forests that have substantially older and larger high-quality trees than can be found through the northern region. We harvested grade 1 sugar maple trees across a wide spectrum of ages and diameters, which we then manufactured into veneer, sawlogs, cants, and hardwood/pulpwood bolts to determine tree value. Tree value continued to increase with increasing dbh, but when the effect of tree age on value was discounted, the value of trees older than 100 years dropped precipitously toward zero. Thus, managing trees to maximize diameter and quality within genetic and site potential and harvesting at about 100 years will produce high-value grade 1 trees in the range of 24 to 30 in. dbh. Management and Policy Implications Forest research conducted on Indian lands often provides different perspectives and conditions that give new insight to forest management. In the case of the Menominee Tribe of Wisconsin, we were able to expand our understanding of tree value and how it changes for much older and larger sugar maple trees than were studied in previous research. The results of this research in many ways confirm existing recommendations for tree size and age related to financial maturity. We did find that absolute tree value increased with ever-increasing tree dbh beyond 30 in.; however, there is a financial cost to growing trees for 300 years to obtain large dbh. This is important for policy and management because it is crucial for managers to practice silviculture to promote the highest diameter growth rates possible given tree genetics and site productivity to maximize tree dbh at harvest. High-grade sugar maple can be grown to 24->30 in. dbh on productive sites in 100–150 years, and this should help to maximize financial returns. Careful logging operations are vital to avoid injury to crop trees that can lead to the development of discolored wood and decay, serious grade defects, and other sources of value loss. [ABSTRACT FROM AUTHOR]

• Deer had only minor impact on growth and survival of sugar maple and ash seedlings. • Seedlings responded primarily to light availability, soil N, and initial size. • Measures of root collar diameter:height detected some effect of deer herbivory. Deer herbivory has a reputation for suppressing tree seedling development in Northern hardwood forests. We examined survival and growth of sugar maple (Acer saccharum) and ash (Fraxinus spp.) seedlings in a controlled factorial experiment with differing light conditions and levels of deer access in a Northern hardwoods forest in Wisconsin, USA. Measurements were made in ∼380 m3 harvest gaps, in transition zones adjacent to gaps, and under closed canopy conditions, both inside and outside of deer exclosures. Browse incidence was initially greater in unfenced treatments, but a general decline through time eliminated this difference. Seven-year survival of both species groups was correlated positively with initial root collar diameter (RCD) and was greater in transition zones. Ash seedling survival was greater in plots with greater overall seedling aggregate height. Soils were primarily differentiated by available nitrogen, which positively influenced height growth of sugar maple in transition zones but did not influence ash growth. Although sugar maple height growth was correlated positively with initial RCD, greater initial height reduced growth rates, both as a simple effect (sugar maple) and in combination with initial RCD (ash). Ash growth correlated negatively with seedling aggregate height in gaps but was unaffected in transition or canopy zones. Allometric coefficients of RCD:height indicated some influence of deer herbivory which was not detected in other analyses. Coefficient values trended downward from year 2 to year 9, but wide confidence intervals limit the value of this metric as an indicator of seedling community resilience with regard to deer. [ABSTRACT FROM AUTHOR]

We used the ecosystem process model Biome-BGC to simulate the effects of harvest and residue removal management scenarios on soil carbon (C), available soil nitrogen (N), net primary production (NPP), and net ecosystem production (NEP) in jack pine ( Pinus banksiana Lamb.) and sugar maple ( Acer saccharum Marsh) ecosystems in northern Wisconsin, USA. To assess harvest effects, we simulated short (50-year) and long (100-year) harvest intervals, high (clear-cut) and low (selective) harvest intensities, and three levels of residue retention (15%, 25%, and 35%) over a 500-year period. The model simulation of NPP, soil C accumulation, and NEP agreed reasonably well with biometric and eddy-covariance measurements of these two ecosystems. The more intensive (50-year rotation clear-cuts with low residue retention) harvest scenarios tended to have the greatest NEP (420 and 678 t C ha−1 for the 500-year interval for jack pine and sugar maple, respectively). All the harvest scenarios decreased mineral soil C and available mineral soil N content relative to the no-harvest scenario for jack pine and sugar maple. The rate of change in mineral soil C decreased the greatest in the most intensive biomass removal scenarios (−0.012 and −0.072 t C ha−1 yr−1 relative to no-harvest for jack pine and sugar maple, respectively) and the smallest decrease was observed in the least intensive biomass removal scenarios (−0.002 and −0.009 t C ha−1 yr−1 relative to no-harvest for jack pine and sugar maple, respectively). The more intensive biomass removal harvest scenarios in sugar maple significantly decreased peak productivity (NPP) in the simulation period. [ABSTRACT FROM AUTHOR]

A 1.44 ha plot in a disjunct Tsuga canadensis-dominated forest in southern Wisconsin was mapped and examined for 25 y. Every 5 y between 1981 and 2006, all of the trees ≥ 2.54 cm dbh were measured and mortalities and additions were noted. The stand had a 27.6% overall decline in density and a 5.8% decline in basal area. Tsuga remained the dominant species though it had a 28.2% decline in density and a loss in basal area of 12.6%. It still made up almost half the relative density and relative dominance throughout the study. Diameter distributions for the six leading species were all bell-shaped or skewed unimodal with the exception of Acer saccharum which had an inverse J-shaped curve. Tsuga presented bell-shaped curves due to the lack of recruitment from the seedling stage. Nearly 32% of the original Tsuga trees ≥ 2.54 cm dbh died throughout the study, giving an annual mortality rate of 1.53%/year. The annual mortality rate for Tsuga stems ≥ 30 cm dbh was 0.71%/year, which is higher than a Michigan study using the same sized stems. The long-term outlook for the Tsuga in this isolated stand is uncertain due to its sporadic regeneration, high mortality rate, possible deer browsing effects combined with future potential threats such as land development, climate warming and the hemlock woolly adelgid. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effects of elevated carbon dioxide [CO2] and ozone [O3] and their interaction on wood chemistry and anatomy of five clones of 3-year-old trembling aspen (Populus tremuloides Michx.). Wood chemistry was studied also on paper birch (Betula papyrifera Marsh.) and sugar maple (Acer saccharum Marsh.) seedling-origin saplings of the same age. Material for the study was collected from the Aspen Free-Air CO2 Enrichment (FACE) experiment in Rhinelander, WI, USA, where the saplings had been exposed to four treatments: control (C; ambient CO2, ambient O3), elevated CO2 (560ppm during daylight hours), elevated O3 (1.5 × ambient during daylight hours) and their combination (CO2 + O3) for three growing seasons (1998–2000). Wood chemistry responses to the elevated CO2 and O3 treatments differed between species. Aspen was most responsive, while maple was the least responsive of the three tree species. Aspen genotype affected the responses of wood chemistry and, to some extent, wood structure to the treatments. The lignin concentration increased under elevated O3 in four clones of aspen and in birch. However, elevated CO2 ameliorated the effect. In two aspen clones, nitrogen in wood samples decreased under combined exposure to CO2 and O2. Soluble sugar concentration in one aspen clone and starch concentration in two clones were increased by elevated CO2. In aspen wood, α-cellulose concentration changed under elevated CO2, decreasing under ambient 03 and slightly increasing under elevated O3. Hemicellulose concentration in birch was decreased by elevated CO2 and increased by elevated O3. In aspen, elevated O3 induced statistically significant reductions in distance from the pith to the bark and vessel lumen diameter, as well as increased wall thickness and wall percentage, and in one clone, decreased fibre lumen diameter. Our results show that juvenile wood properties of broadleaves, depending on species and genotype, were altered by atmospheric gas concentrations predicted for the year 2050 and that CO2 ameliorates some adverse effects of elevated O3 on wood chemistry. [ABSTRACT FROM AUTHOR]

• Long-term comparisons of partial cutting treatments show significant differences. • Selection heavier than conventional practice is sustainable and financially superior. • Single-tree selection treatments maximize both harvested and residual tree quality. • Heavy selection reduces mortality; medium and heavy selection boost diameter growth. Evaluation of long-term studies provides information about the sustainability of forest management on a time scale valuable to forest managers. A long-term silvicultural study at the Argonne Experimental Forest in northern Wisconsin has been continuously maintained for over six decades, providing an opportunity to test differences in growth and yield between three partial cutting methods: single-tree selection, crop tree release, and diameter-limit cutting. Over 65 years, results showed that single-tree selection with low residual stocking (14 m2 ha−1 basal area) performed best in regard to financial returns, growth, and yield, with high financial returns, greater levels of ingrowth, lower mortality, and greater residual percent volumes of high quality sawtimber. Diameter growth was maximized in low to moderate (17 m2 ha−1 residual basal area) residual stocking selection. The diameter-limit cut (18 cm dbh limiting diameter) was not successful in producing high-quality trees or consistent yield. After 50 years the crop tree release treatment did increase percent of high-quality harvested volumes, but to a lesser extent than the selection treatments. Selection treatments removing more basal area provided an overall better return on investment, providing potential incentive for modification to traditionally practiced single-tree selection to higher residual basal areas. [ABSTRACT FROM AUTHOR]

The article deals with the variability in seedling management of sugar maple and the mortality rates of the seedling over the first decade in three climatic regions in Wisconsin. The authors claim that the use of age relationships in the study of plant populations or communities is limited. They add that to be able to determine the probability of a plant individual surviving to the next year, the species being considered should have a stable age distributions. Based on the article, sugar maple has a stable age structure because it has a continuous reproductive input into the youngest age class.

• Diameter, host proportion, and crown class can predict likelihood of hickory mortality. • Extensive hickory mortality most likely due to hickory decline influenced by hickory stem density. • Hickory regeneration not immediately impacted by hickory decline. • Larger hickory stems experience higher mortality rates than smaller stems. Bitternut hickory (Carya cordiformis (Wangenh.) K. Koch) is an important component of many hardwood forest systems in the northern hardwood forests of the Lake States. Extensive mortality of the species was observed in a long-term field experimental site in a second growth northern hardwood forest of Wisconsin between 2010 and 2016. We quantified and documented the characteristics of the mortality, investigated the relationship between bitternut hickory density and mortality patterns, and assessed the persistence of hickory regeneration. The presence of a pathogenic fungus (Ceratocystis smalleyi Johnson and Harrington) and hickory bark beetle (Scolytus quadrispinosus Say) were identified as the main cause of mortality in other instances of hickory decline during a similar time period in the Midwest and Northeast. We investigated the role of these agents through post hoc analysis. Tree surveys of mapped stems ≥10 cm dbh conducted periodically from 2005 to 2016 indicated mortality of hickory rose sharply to 35% year−1 from 2010 to 2016. This is a substantial increase in mortality relative to the dominant species at the site (Acer saccharum Marshall , Tilia americana L., and Fraxinus spp.) which was 1.11% year−1 in the same time period. Mortality rates were higher in larger stems (≥20 cm dbh) than smaller stems (10 < 20 cm dbh). Additional analyses evaluated whether mortality rates were affected by localized species composition, using the proportion of hickory stems among neighboring trees. Proportion of hickory stems, diameter, and crown class proved to be statistically important in predicting mortality in individual hickory stems. The density of hickory regeneration in the <30 cm tall height class decreased from 2010 to 2016. Overall the bitternut hickory population significantly declined, especially the larger sized trees, and this decline will have lasting consequences on the persistence of the species in the area. Potential management actions for mitigating impacts of such rapid hickory decline events, mainly selective thinning, are discussed. Methods for maintaining this co-occurring species is increasingly important as several other codominant species in northern hardwood forests are also decreasing. [ABSTRACT FROM AUTHOR]

Maple syrup is an important non-timber forest product derived from the sap of the sugar maple (Acer saccharum Marshall). However, maple syrup producers are facing a diversity of challenges, including: potential range shifts in the maple resource; increasing variability in the timing, duration and yield of sap flow and syrup operations; invasive species, pests and diseases; and intergenerational land and business transfer challenges. Members of Maple Syrup Producer Associations in Minnesota, Wisconsin, and Michigan were surveyed to learn about their operations, adaptation strategies, concerns, and information needs. While many respondents indicated they have undertaken or plan to undertake adaptation activities, only 11% had done so out of specific concern over changing climate conditions. Climate-motivated activities included: being prepared to tap earlier and utilizing newer technology such as vacuum tubing or reverse osmosis to enhance sap collection and processing efficiency. Respondents were generally unlikely to consider planting climate-resilient maple cultivars or tapping trees other than sugar maple. They expressed the greatest concerns over tree health and forest pests, as well as their physical ability and family member interest to continue their operations. Boil season variability and weather issues were viewed with less concern. Respondents were generally optimistic that they can adapt to future conditions, likely in large measure through the adoption of new technologies, and they expect their syrup production levels to slightly increase in the future. If future climate scenarios play out, however, additional planning and adaptation strategies may be called for, particularly as they relate to forest health and productivity issues.