White Birch Research Articles

Increased leaf area compensated photosynthetic downregulation in response to elevated CO2 and warming in white birch

Predicting photosynthetic acclimation to elevated CO2 and warming is difficult because they have opposite effects. We investigated physiological and morphological responses in white birch ( Betula papyrifera Marshall) to a combination of CO2 and temperature (ACT — 400 µmol·mol–1 CO2, current temperature; ECT — 750 µmol·mol–1 CO2, current + 4 °C temperature). ECT reduced photosynthesis, maximum Rubisco carboxylation ( Vcmax), maximum electron transport rate ( Jmax), photorespiration, daytime respiration, leaf N, and stomatal and mesophyll conductance, but increased biomass, height, total leaf area, electron partitioning to carboxylation and oxygenation ratio, and CO2 compensation point. The photosynthetic acclimation is consistent with the optimal carbon gain theory (carbon gain drives the coordination of carboxylation, electron transport, and respiration). While the photosynthetic acclimation was similar to acclimation to elevated CO2, ECT reduced Jmax/ Vcmax, which is consistent with the response to warming but opposite to the response to elevated CO2, suggesting that thermal acclimation may be the primary mechanism of photosynthetic acclimation to ECT and ECT probably altered N allocation between machinery for carboxylation and that for ribulose-1,5-bisphosphate regeneration. The increase in total leaf area by ECT more than offset the negative effect of photosynthetic downregulation on carbon sequestration, resulting in faster growth and greater biomass under ECT.

Tree growth is connected with distribution and warming-induced degradation of permafrost in southern Siberia.

Hemiboreal and boreal forests growing at the southern margin of the permafrost distribution are vulnerable to climate warming. However, how climate warming threatens the growth of dominant tree species that are distributed on permafrost remains to be determined, particularly in synchrony with warming-induced permafrost degradation. Tree growth in the permafrost region of southern Siberia was hypothesized to be highly sensitive to temperature increasing and warming-induced permafrost degradation. To test this hypothesis, we sampled the tree ring width of 535 trees of dominant species, larch (including Larix gmelinii and L. sibirica) and white birch (Betula platyphylla), in ten hemiboreal to boreal forest plots within different permafrost zones. The relationships between the tree ring basal area index (BAI) and temperature, precipitation, and the Palmer drought severity index (PDSI) were compared among plots located in two permafrost zones. In the isolated permafrost zone, white birch grows better than larch and is not drought-stressed (p < .05). We suggest that the deep-rooted white birch benefits from the water from thawing permafrost, while the growth of the shallow-rooted larch is stressed by drought. In the sporadic discontinuous permafrost zone, both white birch and larch benefited from permafrost melting, but the sensitivity of larch growth to PDSI is still significant (p < .05), indicating drought is still an important climatic factor limiting the growth of larch. Our results imply that the permafrost degradation caused by climate warming affects tree growth by creating the root layer additional water source. In the future, it is necessary to focus on monitoring permafrost degradation to better predict forest dynamics at the southern margin of the permafrost distribution.

White bark in birch species as a warning signal for bark-stripping mammals

Background : Birch species such as Betula pendula have conspicuous white bark and the evolutionary drivers for this colouration remain unresolved. Aims We evaluated our hypothesis that the white bark is a visual warning signal to deter mammals from bark-stripping. Many species of deer (Cervidae) and multiple other mammals consume bark. White birch species’ bark contains betulin and other compounds which likely make the bark unprofitable for herbivores. The white bark has features consistent with a visual signal for mammalian herbivores and could act as a visual aposematic signal of chemical defence. Methods We compared deer bark-stripping between tree species in Scottish woodlands. For Betula pendula, we compared stripping of juvenile brown bark with mature white bark. We also reviewed existing literature to find the tree-species preference for a wide-range of bark-stripping mammals. Results In Scotland, we found that white-barked birch bark was less preferred. We also found mature white birch bark was avoided compared to juvenile brown bark. Existing literature for multiple herbivores showed that white birch species’ bark was often either not preferred or avoided. Conclusion We suggest that the conspicuous white colouration of birch bark may act as an aposematic visual signal to deter bark-stripping mammals.

Thermal Characteristics and Simulation of Enzymatic Lignin Isolated from Chinese Fir and Birch

Lignin is one of the main components of the plant cell wall, and the thermal properties of in situ biomass lignin are crucial for the multi-scale modeling of biomass properties and the thermodynamic modeling of lignin. In this study, high yields of double enzymatic lignin (DEL) were successfully isolated from softwood Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) and hardwood white birch (Betula platyphylla Suk.) to represent the in situ wood lignin. Their thermal properties, including specific heat capacity, thermal conductivity, thermal stability, and thermal degradation kinetic parameters, were tested and simulated. The results showed that Chinese fir DEL has different chemical structural units and thermal properties than birch DEL. The specific heat capacities of Chinese fir DEL and birch DEL at 20 °C were 1301 and 1468 J/(kg·K), respectively, and their thermal conductivities were 0.30 and 0.32 W/(m·K). Their specific heat capacity and thermal conductivity showed a positive linear relationship over a temperature range of 20–120 °C. Chinese fir DEL had a better thermal stability and a higher carbon residue than birch DEL. The average activation energy and pre-exponential factor changed with the conversion rate, and their relationships were simulated using linear or quadratic equations in the conversion rate range of 0.02–0.60. A second-order reaction function was found to be the best mechanism function for DEL thermal degradation.

Effects of strands geometry on the physical and mechanical properties of oriented strand boards (OSBs) made from black spruce and trembling aspen

Black spruce is widely used for lumber production in Eastern Canada, and it has the potential to replace trembling aspen and paper birch for oriented strand board (OSB) manufacturing. This study evaluated the bending modulus of elasticity (MOE) and modulus of rupture (MOR), the internal bond (IB), and the thickness swelling (TS) of OSB panels made from black spruce and trembling aspen strands and how they were affected by strand geometry. All the panels met the CSA O437 (1993) standard for class O-2 properties except for the TS. The strand thickness had a significantly negative effect on the bending properties but a significantly positive effect on the IB and TS properties. The strand length had a significantly positive effect on the parallel bending properties but a significantly negative effect on the perpendicular bending properties and the IB, except for the TS. The OSB panels made from aspen obtained better bending properties, while the IB and TS properties were lower than those of the OSB black spruce panels. The results indicate that black spruce strands obtained from the Eastern Canadian softwood lumber industry are suitable for OSB production, but more work is required to reduce the TS.

Rich Bright Days: Six Writers on Nature and Life

Rich Bright Days:Six Writers on Nature and Life Sam Pickering (bio) Thorpe Moeckel, Down by the Eno, Down by the Haw. Mercer University Press, 2019. 129 pages. $16.00. Paperback. J. Drew Lanham, Sparrow Envy: Field Guide to Birds and Lesser Beasts. Hub City Press, 2021. 95 pages. $13.99. Hardback. John Hess, A Perfectly Ordinary Paradise: An Intimate View of Life on Brawley Creek. Brawley Creek Photography, 2021. xi + 239 pages. Illustrated. $75. Hardback. Connie May Fowler, A Million Fragile Bones: A Memoir. Twisted Road Publications, 2017, 313 pages. $15.95. Paperback. Bob Kunzinger, The Iron Scar: A Father and Son in Siberia. MadVille Publishing, 2022. 157 pages. Illustrated. $19.95. Paperback. Julia Ridley Smith, The Sum of Trifles. University of Georgia Press, 2021. 238 pages. $22.95. Paperback. In the woods bordering and running into old farm fields and along riverbanks around Storrs is an arboretum of trees: red and sugar maples; massive white pines; beech; black, yellow, and sometimes white birch; shagbark and mockernut hickories; hemlocks; the occasional cottonwood; small tulip trees; and among others a congregation of oaks. If I were to shut my eyes and stray from the trails I walk, and, of course, not tumble over an elbow of granite, I'd probably bump into a white oak. Nature writers are as various as the trees of "my" forests, but there are the great oaks, some defoliated by an absence of readers but still [End Page 173] predominant. Towering above others in my study is Gilbert White's The Natural History of Selborne, a collection of letters White wrote in the eighteenth century describing his ramblings around the parish of Selbourne in Hampshire. He described the landscape, the people, and, above all, the birds. Because his observations were parochial and specific, they transcended the limitations of mind and hedgerow. In the nineteenth century, the book became the nature lover's Pilgrim's Progress, and almost every naturalist worth his sap genuflected to Shelborne. The other big oak on my shelf is Nan Shepherd's The Living Mountain. Published in 1977, 184 years after Selborne, the book describes Shepherd's love for and wanderings in the Cairngorm Mountains in Scotland. Much as White was born and died in Selborne, Shepherd states that she "had the same bedroom all my life." Like White, she describes her world in learned, appreciative detail: its frost and snow, the air and light, plants, insects, people. Her prose, however, is more poetic and evocative of mood. "A mountain," she writes, "has an inside." Repeated walks are not repetitious. Although details become clearer, the walker's vision and understanding shimmer. White is a sensible eighteenth-century spectator. Exteriors not only please and startle; they also satisfy. They are what senses perceive. Shepherd, on the other hand, is a modern quick to ponder and envision interiors. "As I penetrate more clearly into the mountain's life," she writes, "I penetrate also into my own." Down by the Eno, Down by the Haw. Thorpe Moeckel. Mercer University Press, 2019. 129 pages. $16.00. Paperback In varying degrees, the books of most nature writers are hybrids of White and Shepherd. The Haw and the Eno are rivers in the Piedmont of North Carolina. In Down by the Eno, Down by the Haw, Thorpe Moeckel canoes and roams the watersheds of the rivers. He says he follows "slants of light." For me, the slants are usually deer trails. For Moeckel, the light is actual but also metaphoric and freeing. It shines in the broken woods and creeks behind big-box stores and strip malls, churches and schools, unexpected places that surprise and inspire. Moeckel's nature is not a landscape fenced in by topic sentences. [End Page 174] He knows that words shackle, and he tries to capture the truths of refracting moments in the moments themselves rather than by recollecting and framing them in a later falsifying tranquility. As a result, his prose often smacks of the automatic writing popular a hundred years ago. Ordering observation, proponents of automatic writing argued, distorted the truth of spontaneity. Of course, words themselves are artifacts. By their very nature, they shape fictions, much as a well...

Inside old reclaimed mine tailings in Northern Ontario, Canada: A microbial perspective

Large areas of metal–contaminated tailings have been revegetated in Northern Ontario (Canada). The specific objective of the present study is to determine if variations in vegetation, and soil physico-chemistry in sulfide tailings is associated with microbial biomass, abundance and diversity. Microbial biomass was determined using Phospholipid fatty acid analysis (PLFA). Amplicon based analysis of the soil bacterial and fungal microbiota was assessed by high throughput sequencing of 16S rRNA gene for bacteria and internal transcribed spacer (ITS) region for fungi. Significant differences in soil pH, organic matter content, and total metals (Cu, Fe, Ni, and Zn) were observed among sites. There were significant variations in microbial biomass among the tailing sites with areas covered with white birch showing the highest level of bacterial and fungal biomass compared to areas vegetated by pines species or pine-white birch mixture. Proteobacteria was the most dominant bacterial phylum while Basidiomycota was the predominant fungal phylum. The most abundant bacterial genus was Mucilaginibacter , followed by Acidobacterium , Acidisphaera , Burkholderia , and Steroidobacter . Site-specific bacterial and fungal genera were identified. However, there were no significant differences for # of OTUs, Chao 1, Simpson index, Shannon index, and species richness among the bacterial populations from different soil tailing areas despite differences in plant populations and soil physico-chemistry. The relative abundance of fungi was associated with the variation in ecology of specific areas. Chao 1, # of OTUs, Simpson index, Shannon index, and species richess were significantly lower at Vale 3 compared to Vale 1 and Vale 5.

Modeling Optimal Forest Rotation Age for Carbon Sequestration in the Great Khingan Mountains of Northeast China

The growing concern about climate change has led to the rise of carbon cycle research. Forest cutting planning affects the carbon cycle due to the carbon sequestration function of forests. In this work, we propose a planning model for determining the regeneration cutting age of forests to optimize carbon sequestration and improving the associated economic and ecological benefits. We first built a model based on the carbon sequestration consumption of forest products and forest carbon sequestration to predict the change in forest carbon sequestration over time. The accuracy of the model was verified with forest data from the Great Khingan mountains. Furthermore, we added in economic and ecological factors to build an improved model, which was also applied to the Great Khingan forest. The improved regeneration cutting ages were calculated as 65, 134, 123, 111 and 73 years for white birch, larch, Scots pine, oak, and poplar trees for natural forests, whereas the ages were 34, 65, 64, 77 and 37 years for planted forests, respectively. It can be predicted that the total carbon sequestration in the Great Khingan forests will accumulate to 974.80 million tons after 100 years. The results of this study can provide useful guidance for local governments to develop a sustainable timeline for forest harvesting to optimize carbon sequestration and improve the associated economic and ecological benefits.

Cold-season freeze frequency is a pervasive driver of subcontinental forest growth

As northern latitudes experience rapid winter warming, there is an urgent need to assess the effect of varying winter conditions on tree growth and forest carbon sequestration potential. We examined tree growth responses to variability in cold-season (November–April) frequency of freeze days (FFD) over 1951 to 2018 using tree-ring data from 35,217 trees and 57 species at 4,375 sites distributed across Canada. We found that annual radial growth responses to FFD varied by species, with some commonalities across genera and clades. The growth of gymnosperms with late spring leaf-out strategies was negatively related to FFD; years with high FFD were most detrimental to the annual growth of Pinus banksiana, Pinus contorta, Larix lyalli, Abies amabilis, and Abies lasiocarpa. In contrast, the growth of angiosperms with early leaf-out strategies, namely, Populus tremuloides and Betula papyrifera, was better in the coldest years, and gymnosperms with intermediate leaf-out timing, such as widespread Picea mariana and Picea glauca, had no consistent relationship to FFD. Tree growth responses to FFD were further modulated by tree size, tree age, regional climate (i.e., mean cold-season temperature), and local site conditions. Overall, our results suggest that moderately warming winters may temporarily improve the growth of widespread pines and some high-elevation conifers in western Canada, whereas warming winters may be detrimental to the growth of widespread boreal angiosperms. Our findings also highlight the value of using species-specific climate-growth relationships to refine predictions of forest carbon dynamics.

Foliar nutrient concentrations of six northern hardwood species responded to nitrogen and phosphorus fertilization but did not predict tree growth.

Foliar chemistry can be useful for diagnosing soil nutrient availability and plant nutrient limitation. In northern hardwood forests, foliar responses to nitrogen (N) addition have been more often studied than phosphorus (P) addition, and the interactive effects of N and P addition have rarely been described. In the White Mountains of central New Hampshire, plots in ten forest stands of three age classes across three sites were treated annually beginning in 2011 with 30 kg N ha−1 y−1 or 10 kg P ha−1 y−1 or both or neither–a full factorial design. Green leaves of American beech (Fagus grandifolia Ehrh.), pin cherry (Prunus pensylvanica L.f.), red maple (Acer rubrum L.), sugar maple (A. saccharum Marsh.), white birch (Betula papyrifera Marsh.), and yellow birch (B. alleghaniensis Britton) were sampled pre-treatment and 4–6 years post-treatment in two young stands (last cut between 1988–1990), four mid-aged stands (last cut between 1971–1985) and four mature stands (last cut between 1883–1910). In a factorial analysis of species, stand age class, and nutrient addition, foliar N was 12% higher with N addition (p < 0.001) and foliar P was 45% higher with P addition (p < 0.001). Notably, P addition reduced foliar N concentration by 3% (p = 0.05), and N addition reduced foliar P concentration by 7% (p = 0.002). When both nutrients were added together, foliar P was lower than predicted by the main effects of N and P additions (p = 0.08 for N × P interaction), presumably because addition of N allowed greater use of P for growth. Foliar nutrients did not differ consistently with stand age class (p ≥ 0.11), but tree species differed (p ≤ 0.01), with the pioneer species pin cherry having the highest foliar nutrient concentrations and the greatest responses to nutrient addition. Foliar calcium (Ca) and magnesium (Mg) concentrations, on average, were 10% (p < 0.001) and 5% lower (p = 0.01), respectively, with N addition, but were not affected by P addition (p = 0.35 for Ca and p = 0.93 for Mg). Additions of N and P did not affect foliar potassium (K) concentrations (p = 0.58 for N addition and p = 0.88 for P addition). Pre-treatment foliar N:P ratios were high enough to suggest P limitation, but trees receiving N (p = 0.01), not P (p = 0.64), had higher radial growth rates from 2011 to 2015. The growth response of trees to N or P addition was not explained by pre-treatment foliar N, P, N:P, Ca, Mg, or K.

Bacterial communities associated with wood rot fungi that use distinct decomposition mechanisms

Wood decomposer fungi are grouped by how they extract sugars from lignocellulose. Brown rot fungi selectively degrade cellulose and hemicellulose, leaving lignin intact, and white rot fungi degrade all components. Many trees are susceptible to both rot types, giving carbon in Earth’s woody biomass, specifically lignin, a flexible fate that is affected not only by the fungal decomposition mechanism but also the associated microbial community. However, little is understood about how rot type may influence the microbial community in decaying wood. In this study, we quantified bacterial communities associated with Fomes fomentarius (white rot) and Fomitopsis betulina (brown rot) found on a shared tree host species, birch (Betula papyrifera). We collected 25 wood samples beneath sporocarps of F. fomentarius (n = 13) and F. betulina (n = 12) on standing dead trees, and coupled microbial DNA sequencing with chemical signatures of rot type (pH and lignin removal). We found that bacterial communities for both fungi were dominated by Proteobacteria, a commonly reported association. However, rot type exerted significant influence on less abundant taxa in ways that align logically with fungal traits. Amplicon sequence variants (ASVs) were enriched in Firmicutes in white-rotted wood, and were enriched in Alphaproteobacteria, Actinobacteria and Acidobacteria in lower pH brown rot. Our results suggest that wood decomposer strategies may exert significant selection effects on bacteria, or vice versa, among less-abundant taxa that have been overlooked when using abundance as the only measure of influence.

Estimating available unused dead wood materials for heat generation in Mongolia: how much coal can unused dead wood materials substitute?

In this study, we estimated the technoeconomic availability of three types of dead trees, namely commercially fallen, normally fallen, and standing, in Mongolian subgroups. For dead trees of three major Mongolian tree species (Siberian larch, Scotch pine, and Asian white birch), lumber, firewood, and unused material as sources of energy were quantified and operational costs (marking, felling, skidding, transporting, loading/unloading, processing, and stumpage prices) were estimated. As a result, most Mongolian subgroups were profitable and suitable for the harvest of unused materials. Moreover, unused materials of dead trees can substitute nearly 5.45 million tons of coal, although it is not sufficient to meet the 0.6years of coal demand across Mongolia. However, in some places, unused dead wood materials can completely substitute coal for decades. Therefore, although the heat utilization of woody biomass is not suitable for Mongolia as a whole, it is feasible in specific regions where forest resources are abundant, such as some Mongolian sub-provinces. Promoting the use of dead trees can reduce the risk of damage caused by wildfires and pests, which are serious problems in Mongolia, and keep the forests healthy. Furthermore, unused materials can generate new income opportunities, and the forest land can be well prepared by removing dead trees to promote planting for sustainable forest management. Finally, dead trees can be used as a resource until transition to sustainable forests with living trees.

Drought timing and species growth phenology determine intra-annual recovery of tree height and diameter growth.

Droughts interact with tree phenology to drive declines in growth. As climate change makes drought more likely in the Northeastern USA, it is important to understand how droughts at different times of year will lead to reduced height and diameter growth of trees. To determine how seasonal drought may reduce intra-annual growth, we implemented spring, summer or fall droughts on 288 containerized saplings of six tree species (Acer rubrum, Betula papyrifera, Prunus serotina, Juniperus virginiana, Pinus strobus and Thuja occidentalis). We tracked weekly soil moisture, leaf water potential, height, diameter and survival of all trees before, during and after each 6-week drought. We found that the tree species that conducted the majority of their height or diameter growth in the spring were most sensitive to spring droughts (B. papyrifera and Pi. strobus). Thuja occidentalis also experienced significantly reduced growth from the spring drought but increased growth after the drought ended and achieved total height and diameter growth similar to controls. In contrast, summer droughts halted growth in most species for the remainder of the growing season even after the drought had ended. Fall droughts never impacted growth in the current year. These fine temporal-scale measurements of height and diameter growth suggest that tree response varies among species and is dynamic at intra-annual scales. These relatively rare data on intra-annual height growth sensitivity are important for canopy recruitment of saplings in forest ecosystems. Species-specific sensitivities of intra-annual growth to drought can inform models of forest competition in a changing climate.

Effects of the seasonal availability of freshly cut logs and tree species on the early response of saproxylic insects in boreal forest

Deadwood left on site after logging can be colonized by many saproxylic insects including xylophagous species that can damage the wood. This study aims to estimate the risks resulting from the storage of logs at the edge of balsam fir-white birch stands. We used taxonomic richness, as well as visitation and colonization rates of saproxylic insects to determine how their use of freshly cut logs varies with the seasonal availability of logs and the tree species. During the summer of 2019, balsam fir, black spruce, and paper birch logs were experimentally cut at three different periods and were placed in four harvested sites located in the Forêt Montmorency experimental forest in eastern Quebec, Canada. Visitation and colonization rates were assessed using trunk-window traps and log dissection, respectively. A total of 854 saproxylic insects belonging to 53 genera were captured over the three months of sampling. The logs were colonized by xylophagous species within one month after tree death. These xylophagous insects belonged mainly to the species Urocerus prob. albicornis, and Monochamus prob. scutellatus. Colonization rates of logs by Monochamus prob. scutellatus were higher from mid-July to mid-September than earlier during the season. These xylophagous species also responded to tree species, with higher abundance on conifers than on white birch both in terms of visitation and colonization rates. Furthermore, there was no evidence of colonization on paper birch. Our results suggest that a prompt harvesting of conifer logs between mid-July and mid-September on harvested sites will minimize damage to freshly cut logs.

Photosynthetic and Growth Responses in a Pioneer Tree (Japanese White Birch) and Competitive Perennial Weeds (Eupatorium sp.) Grown Under Different Regimes With Limited Water Supply to Waterlogging.

For a successful natural regeneration of Japanese white birch (Betula platyphylla var. japonica), competitive vegetation should be managed. Here, we clarified how soil water condition modifies the competitiveness of Japanese white birch against perennial weeds, Eupatorium species, based on an ecophysiological approach combining a glasshouse experiment and a field survey. We investigated photosynthetic and growth responses to various water regimes from water deficit to waterlogging (two times-a-week irrigation, three times-a-week irrigation, half waterlogging, and full waterlogging) in pot-grown seedlings of Japanese white birch and the competitive weed Eupatorium makinoi. The ratio of seedling height of Japanese white birch to seedling height of E. makinoi showed a decreasing trend from two times-a-week irrigation to full waterlogging, which suggests a lower competitiveness for light resource in Japanese white birch with increasing soil wetness. The maximum rate of Rubisco carboxylation (Vc,max) based on unit N was lower in waterlogging treatments than in two times- and three times-a-week irrigation in Japanese white birch, whereas E. makinoi showed the opposite response. This suggests that N partitioning into Rubisco and/or Rubisco activation might be suppressed in Japanese white birch but enhanced in E. makinoi under waterlogging. The maximum photochemical efficiency of photosystem II (Fv/Fm) was also lower in seedlings of Japanese white birch grown under waterlogging treatments. We further conducted a field survey on the relationship between Fv/Fm and topographic wetness index (TWI) in seedlings of Japanese white birch and E. glehnii (closely related to E. makinoi) naturally grown in a study site 5 years after canopy tree cutting. Lower Fv/Fm was observed in seedlings of Japanese white birch with increasing TWI, whereas no significant trend was observed in E. glehnii, in agreement with the glasshouse experiment. Thus, keeping soils not always humid might be favorable to photosynthetic performance and growth competitive ability of Japanese white birch against Eupatorium species.

Long term variation of leaf abundance in a northern hardwood forest

Leaf abundance of trees plays a dominant role in energy, water and nutrient flux of forest ecosystems, in defining the habitat structure of entrained biota and in mediating interspecific competition among tree species. We quantified leaf abundance of three dominant tree species (Acer saccharum Marsh.; Fagus grandifolia Ehrh.; Betula alleghaniensis Britt.) for 27 years in mature northern hardwood forest at the Hubbard Brook Experimental Forest, New Hampshire, USA using annual counts of leaves of each species collected in 117 litter traps (0.1 m2, each). We hypothesized that variation in leaf abundance would reflect known disturbance events and canopy dieback episodes. No significant trend in leaf abundance of the three species over 27 years (1993–2019) was observed in seven reference stands despite known canopy dieback of sugar maple and American beech in these stands, indicating that 1) maple decline preceded our sampling interval and 2) expansion of beech understory compensated for canopy dieback caused by beech bark disease. Leaf abundance temporarily declined significantly in response to known disturbances (ice storm, 34 to 47%; late-spring frost, 13 to 16%). Increased leaf abundance, especially for sugar maple (30%), on a watershed where calcium addition restored acidified soils, was probably associated with increased soil pH, Ca availability and decreased Al. The temporal sequence of decline of paper birch at higher elevations following a severe drought in 2002 also was apparent. Leaf abundance based on leaf litterfall in deciduous forests provides a useful indicator of forest ecosystem function and forest health.

Synergism of enzymes in chemical pulp bleaching from an industrial point of view: A critical review

AbstractEnzymes are biological catalysts and are very specific, catalyzing either a single chemical reaction or a limited number of closely related reactions. For example, xylanases are enzymes that catalyze the cleavage of polymeric xylan and thereby break down this hemicellulose. The first xylanase enzyme preparations used in the bleaching process of chemical pulp also contained cellulase, which catalyzes the hydrolysis of cellulose. This obviously had an adverse effect on pulp yield and quality. Unfortunately, this setback gave enzyme‐assisted pulp bleaching a negative reputation. At a later stage, enzyme producers managed to engineer enzyme production strains that generated cellulase‐free xylanase preparations. However, due to the initial negative experiences with the earlier enzyme mixtures, only a limited number of companies in the pulp industry have seriously considered using these so‐called second‐generation enzymes in their bleach plants. It is apparent that these improved enzyme preparations would bring about significant benefits in terms of chemical cost savings and effluent quality. In addition to xylanase‐aided bleaching, it is possible to improve the effectivity further by adding other enzymes, such as lipase and esterase, to create an enzyme cocktail. This may be particularly beneficial in the bleaching of hardwood pulp, such as white birch, which often encounters complex and troublesome problems with wood extractives. By adding different types of enzymes at more than one position in the fiberline, even further improvements are possible. The main objective of this review is to discuss the advantages of incorporating modern enzyme preparations in the bleaching of chemical pulp.

Insect defoliation modulates influence of climate on the growth of tree species in the boreal mixed forests of eastern Canada.

Increasing air temperatures and changing precipitation patterns due to climate change can affect tree growth in boreal forests. Periodic insect outbreaks affect the growth trajectory of trees, making it difficult to quantify the climate signal in growth dynamics at scales longer than a year. We studied climate‐driven growth trends and the influence of spruce budworm (Choristoneura fumiferana Clem.) outbreaks on these trends by analyzing the basal area increment (BAI) of 2058 trees of Abies balsamea (L.) Mill., Picea glauca (Moench) Voss, Thuja occidentalis L., Populus tremuloides Michx., and Betula papyrifera Marsh, which co‐occurs in the boreal mixedwood forests of western Quebec. We used a generalized additive mixed model (GAMM) to analyze species‐specific trends in BAI dynamics from 1967 to 1991. The model relied on tree size, cambial age, degree of spruce budworm defoliation, and seasonal climatic variables. Overall, we observed a decreasing growth rate of the spruce budworm host species, A. balsamea and P. glauca between 1967 and 1991, and an increasing growth rate for the non‐host, P. tremuloides, B. papyrifera, and T. occidentalis. Our results suggest that insect outbreaks may offset growth increases resulting from a warmer climate. The observation warrants the inclusion of the spruce budworm defoliation into models predicting future forest productivity.

NEW DATA ON THE DISTRIBUTION OF JAPANESE WHITE BIRCH (BETULA PLATYPHYLLA SUKACZ.) IN THE OLYUTORSKY DISTRICT OF THE KORYAK OKRUG (KAMCHATSKY KRAI)

New data on the distribution of Japanese white birch (Betula platyphylla Sukacz.) groves in the Olyutorsky District (Koryak Okrug of the Kamchatsky Krai) are presented. The geobotanical description of white-birch forests in the valley of River Kailulovayam, a tributary of River Vyvenka, is given. Using the dominantdeterminant approach the forests were ascribed to the association Betuletum platyphyllae fruticoso-varioherbosum. White-birch forests of the Koryak Okrug grow in the valleys of large rivers in areas away from the influence of the Bering Sea. They occupy above-floodplain terraces with mesic coarse-loam and loamy sand soils underlain by pebbles. The studied community of Betula platyphylla is similar in floral composition and structure to the shrub-forb valley white-birch forests of the Penzhinsky District of the Koryak Okrug. In comparison with Kamchatka analogues, the white-birch forests of Northern Koryakia are characterized by a reduced floral composition. The white birch grove in the Kaylulovayam River valley is the second confirmed location of Betula platyphylla in the Olyutorsky District.

Succession of Ambrosia Beetles Colonizing the Logs of Fallen Alder and Birch Trees.

Simple SummaryTo determine the succession of ambrosia beetles after tree felling, two Betulaceae tree species, an alder (Alnus hirsuta), and a white birch (Betula platyphylla var. japonica) were felled as bait logs in central Hokkaido, Japan, in 2016. From 2016 to 2018, the bait logs were dissected late in each flying season to collect ambrosia beetles. During the period of monitoring, most beetles were collected during the first 2 years. The ambrosia beetle faunas colonizing the two plant species were found to be similar, and it was established that each beetle species appeared in the same sequence in each of the two plant species, albeit with differing temporal patterns. These observations thus indicate a similar sequence of beetle succession in the two tree species, and that the relative niches of beetle species in the successional sequence after tree felling can be determined using this methodology.Ambrosia beetles bore into the xylem of woody plants, reduce timber quality, and can sometimes cause devastating damage to forest ecosystems. The colonization by different beetle species is dependent on host status, from healthy trees to the early stages of wood decay, although the precise factors influencing their host selection are not well known. Classic studies on plant ecology have determined the niches of different plant species in vegetation succession, based on comparisons of successions in different locations using ordination analyses, although the factors influencing the colonization of each species are largely undetermined. In this study, to characterize the succession of ambrosia beetles after tree felling, two Betulaceae tree species, an alder (Alnus hirsuta), and a white birch (Betula platyphylla var. japonica) were felled as bait logs in central Hokkaido, Japan, in 2016. From 2016 to 2018, the bait logs were dissected late in each flying season, and ambrosia beetles were collected from the logs. During the period of monitoring, the beetle colonization in both tree species was mostly concentrated in the first 2 years. We observed similarities in the beetle faunas colonizing the two plant species, and that individual species appeared in the same sequence in the logs of the two plant species, although the temporal patterns of colonization differed. Consequently, significant differences in beetle community compositions in the two host species were detected in each of the first 2 years of the study, whereas the difference in the overall composition of beetle assemblages (=pooled over 3 years) between the two plant species was smaller than that in either 2016 or 2017. We speculated that the differences in the temporal pattern of colonization could be attributable to differences in the rates at which the wood of the two tree species deteriorated. Treptoplatypus severini and Xylosandrus crassiusculus were considered to be early-successional species that commenced log colonization soon after felling, although T. severini has a wide niche and was collected during all 3 years of the study. Conversely, Xyleborinus attenuatus and Heteroborips seriatus were identified as probable late-successional species that showed a preference for older logs.