Degradation of White Birch Shelterbelts by the Attack of White-Spotted Longicorn Beetles in Central Hokkaido, Northern Japan

A widespread decline of white birch (Betula platyphylla var. japonica) shelterbelts was observed in central Hokkaido, Japan. Many exit holes bored by white-spotted longicorn beetles (Anoplophora malasiaca) were found at the base of the trunks of trees in these stands. The present study aims to evaluate the effects of infestation on the degradation, and demonstrates whether the number of exit holes (Nholes) can be used as an index of the decline of trees. We selected 35 healthy appearing stands and 16 degraded stands in the study area. A generalized linear mixed model with zero inflation revealed that Nholes of standing dead trees tended to be greater than that of living trees, and the tree vigor decreased with increasing Nholes. These results implied that the degradation of the shelterbelts was caused by the beetle. We also found size-dependent mortality, i.e., only a few larvae can cause the death of smaller trees, but not larger trees. Furthermore, evaluation of the degradation at the stand level (Nholes) using a logistic regression analysis revealed that the degradation at the stand level could be predicted by Nholes. Our findings can be used as a useful index marker for diagnosing white birch shelterbelts.

Stock of standing dead trees in boreal forests of Central Siberia

A significant part of carbon assimilated by forest is deposited in tree trunks. Growth and development of tree stands is accompanied by accumulation of standing dead trees (snags) due to natural tree mortality and as a result of the impact of exogenous factors. Carbon accumulated in these dead trunks is excluded from the fast turnover due to low rate of wood decomposition, so that snags can be considered as a pool of organic carbon with a slow rate of its return to the atmosphere. We estimated stock of snags on 54 sample plots, which represent the main types of forest ecosystems in the northern and middle taiga of Central Siberia. In the middle taiga, stock of snags varied from up to 7 m3 ha-1 in Siberian spruce forests to 20-42 m3 ha-1 in Scots pine forests. Larch forests in the northern taiga had the similar stock of snags as larch forests in the middle taiga despite significantly higher growing stock in the later. Snags contributed from 4 to 19% to the total stock of woody biomass in studied forests. This study indicated the significance of snags and can be used to estimate carbon budget of forest ecosystems of the region.

Is the modern-day dieback of yellow-cedar unprecedented?

In Southeast Alaska, many stands of yellow-cedar (Callitropsis nootkatensis D. Don; Oerst. ex D.P. Little; hereafter: ‘YC’) contain numerous standing, dead snags. Snag-age estimates based on morphology have been used to support the interpretation that a warming climate after ca. 1880 triggered unprecedented YC dieback. Here we present new estimates of YC snag longevity by cross-dating 61 snags with morphologies that suggest they stood dead for extended periods. All but four of these snags have lost their outermost rings to decay, so we estimate when they died using a new method based on wood-ablation rates measured in six living trees that display partial cambial dieback. Results indicate that ~59% of YC snags that lost their branches to decay (Class 5 snags) have remained standing for > 200 years, and some for as long as 450 years (snag longevity mean ± SD: 233 ± 92 years). These findings, along with supporting evidence from historical photos, dendrochronology, and snag-morphology surveys in the published literature suggest that episodes of YC dieback also occurred before 1880 and before significant anthropogenic warming began. The roles played by climate change in these earlier dieback events remain to be further explored.

Impacts of Land Surface Conditions and Land Use on Dust Events in the Inner Mongolian Grasslands, China

Aeolian processes in temperate grasslands (TGs) are unique because the plant growth–decay cycle, soil water, and land-use interactions affect the seasonal and inter-annual changes in dust events. Land-use types in Inner Mongolian TGs are unique (settled grazing and grass mowing) compared with those in Mongolian TGs. Since 2003, land use has been controlled by grassland protection legislation, which is intended to prevent desertification and dust storms. In this study, we used process-based ecosystem (DAYCENT) and statistical modeling, along with dust event observations from March to June of 1981–2015, to (1) identify critical land surface factors controlling dust emissions (vegetation components, live grass, standing dead grass, litter, and soil moisture) at typical and desert steppe sites in Inner Mongolia and (2) estimate the impact of controlled land-use legislation on dust events. The DAYCENT model realistically simulated the dynamics of the observed vegetation components and soil moisture in 2005–2015. At both sites, similar significant correlations were obtained between spring dust events and wind speed or a combination of all surface factors that retained anomalies (memory) from the preceding year. Among the surface factors, vegetation was a critical factor that suppressed dust in Inner Mongolian TGs, similar to that in Mongolian TGs. In the desert steppe, standing dead grass had the strongest memory and was significantly correlated with dust events, whereas no significant correlations were observed in the typical steppe. This suggests that, in a typical steppe region, heavy grazing and mowing result in few dead grasses, thereby inhibiting the prevention of dust events. Moreover, the simulations of dust events under controlled (light grazing) and uncontrolled (heavy grazing) land-use conditions demonstrated that the grassland protection legislation reduced the occurrence of dust events in typical and desert steppe sites by 25 and 40%, respectively, since 2003.

Features of coarse woody debris volume formation in fresh sudibrova conditions in Zmiini islands tract of Kaniv Nature Reserve

Dead wood (woody debris) is an important component of forest ecosystems. It performs a number of ecological and environmental functions. The article studies the peculiarities of the formation of coarse wood detritus volume and its qualitative structure in forests in the conditions of fresh sudibrova of the Zmiiini Islands tract of Kaniv Nature Reserve. The study of dead wood was carried out in 140-year-old pine-oak forests of natural origin on a permanent sample plot (0.24 ha) by identifying and measuring of standing and lying deadwood components. It was found that dead wood in the forest ecosystem was formed due to the dying of trees of five species: common oak (Quercus robur L.), Scots pine (Pinus sylvestris L.), Norway maple (Acer platanoides L.), small-leaved lime (Tilia cordata Mill.) and common hornbeam (Carpinus betulus L.), and has a volume 56.3 m3·ha–1. Dead wood volume is dominated by standing dead trees — 82.1%, and the share of lying dead wood, respectively, is 17.9%. The main part of dead wood volume is formed by two tree species — common oak and Scots pine, the share of which together is 94.3%. Common oak and Scots pine is characterized by a predominance of standing dead wood, while for other tree species — lying dead wood. In general, dead wood is formed by detritus of I–IV classes of destruction, at the same time detritus of class II decomposition has a significant advantage (70.5%), recently dead wood has a much smaller share (I class, 24.8%), and other classes of destruction have insignificant shares, which together do not exceed 5.0%. No woody detritus of the last (V) class of destruction was detected. Volume of standing dead wood is 46.2 m3·ha–1, and is formed by whole and broken dead trees. In terms of species composition, common oak has a significant advantage (74.5%), Scots pine has a much smaller share (25.1%), and the share of Norway maple is insignificant (0.4%). The total standing dead wood volume is dominated by wood of class II destruction (33.0 m3·ha–1, 71.4%) compared with class I (13.2 m3·ha–1, 28.6%). Lying dead wood is represented by four classes of destruction (I–IV), however, no woody debris was found at the late (last) stage of decomposition (class V). In terms of volume, the second class of destruction has an absolute advantage (6.7 m3·ha–1, 66.3%), much less class III detritus (2.3 m3·ha–1, 22.8%). Lying dead wood of common oak is represented by all four classes of destruction, among which III (40.5%) and I (33.3%) classes predominate. Lying dead wood of other tree species is characterized by the predominance of II or III classes of destruction. The main factors in the formation of woody detritus in the pine-oak forest in the Zmiiini Islands tract could be the impact of adverse climatic conditions (long periods without precipitation in summer), which led to the weakening of individual trees and their death, gusts of wind that broke individual tree trunks, low-intensity snow breaks, and the influence of biotic factors (insects, pathogens).

Understanding the climate impacts on decadal vegetation change in northern Alaska

The Arctic is experiencing rapid climate change. This research documents tundra vegetation changes near Atqasuk and Utqiaġvik, Alaska. At each location, 30 plots were sampled annually from 2010 to 2019 using a point frame. For every encounter, we recorded the height and classified it into eight groupings (deciduous shrubs, evergreen shrubs, forbs, graminoids, bryophytes, lichens, litter and standing dead vegetation); for vascular plants we also identified the species. We found an increase in plant stature and cover over time consistent with regional warming. Graminoid cover and height increased at both sites, with a fivefold increase in cover in Atqasuk. At Atqasuk shrub and forb cover and height increased. Species diversity decreased at both sites. Year was generally the strongest predictor of vegetation change suggesting a cumulative change over time; however, soil moisture and soil temperature were also predictors of vegetation change. We anticipate plants in the region will continue to grow taller as the region warms, resulting in greater plant cover, especially graminoids and shrubs. The increase of plant cover and accumulation of litter may impact nonvascular plants negatively. Continued changes in community structure will impact energy balance and carbon cycling and may result in regional and global consequences.

Volume of woody detritus in fresh maple-linden dibrova in Slobozhanskyi National Nature Park

The article examines the volume of coarse woody detritus in fresh maple-linden-dibrova in Slobozhanskyi National Nature Park. The study was carried out in 115-year-old forest with a predominance of common oak (Quercus robur L.) of natural origin on a sample plot (0.24 ha) by identifying and measuring of standing and lying dead wood components. The volume of dead wood in the forest ecosystem is 32.4 m3·ha–1 and consists of fallen (84.3%) and standing (15.7%). The main part of the dead wood volume is formed by one tree species — common oak (91.3%). In general, woody detritus is characterized by I–IV stages of decomposition, at the same time detritus of III (52.5%) and II (41.7%) stages prevails, detritus of other decomposition stages has insignificant shares (not exceeding 5.0%). No detritus of the last (V) stage of decomposition was detected. The volume of standing dead wood was 5.1 m3·ha–1 and is formed by whole and broken dead trees. In terms of species composition, common oak predominates (80.4%), other species have much smaller shares: small-leaved linden (Tilia cordata Mill.) (13.7%) and Norway maple (Acer platanoides L.) (5.9%). The volume of standing dead wood is dominated by detritus of decomposition stage II (4.8 m3·ha–1, 94.1%), compared with stage I (0.3 m3·ha–1, 5.9%). The volume of lying dead wood is 27.3 m3·ha–1 and is formed by whole fallen trees, fragments of fallen trees (trunks) and thick branches. In terms of species composition dead wood volume is dominated by common oak detritus (25.6 m3·ha–1, 93.7%), and the shares of other species are insignificant. Fallen dead wood is represented by four stages of decomposition (I–IV). In terms of volume, decomposition stage III has an absolute advantage (16.9 m3·ha–1, 61.9%), much less detritus of stage II (8.7 m3·ha–1, 31.9%). Relatively low volume of woody detritus and the absence of dead wood of decomposition stage V may be associated with forestry activities, including selective sanitary cutting and fallen woody debris removal, in the past in modern NNP areas.