•The C and N dynamics are regulated mainly by tree species identity.•Wood density loss and cellulose and lignin degradation are related to the N dynamics.•Bark fragmentation partly controls the C and ...N amounts dynamics at the log level.•In boreal forests, downed logs contribute significantly to long-term C and N cycles.
Quantifying forest carbon (C) and nitrogen (N) turnover rates requires better understanding of the mechanisms of decomposition of coarse woody debris (CWD). We examined the dynamics of bulk density, C, N, cellulose and lignin in downed logs, taking into account initial interspecific trait differences in bark and wood, in a 66-year-long decomposition chronosequence in an old-growth mixed boreal forest.
Wood and bark density decreased with increasing decay class and time since tree death. The C concentration per mass did not change or slightly decreased. Nitrogen increased in wood faster than in bark. In aspen wood, it increased two times more intensively than in wood of conifers. The C/N ratio and the cellulose content decreased, whereas the lignin content increased, decreased or remained stable in wood depending on tree species and calculation basis. Spruce wood was characterized by the greatest cellulose degradation rates. The N availability positively influenced wood bulk density loss and cellulose degradation in wood of all tree species, as well as the C loss in conifer bark.
The total C amount in bark and wood of individual downed logs decreased. The total N amount decreased in bark and increased in wood with different rates depending on tree species identity.
The results indicate the importance of accounting for the CWD tissue tree species specific traits in decomposition studies. In old-growth boreal forests, downed logs contribute significantly to long-term C and N sequestration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•In almost half of Siberian larch trees, decomposition started prior to death.•Those trees lost up to 29% of their wood mass before falling.•After tree death, the whole stem decomposition rate was ...0.026 yr−1.•Trees affected by biotrophic fungi decomposed after death at a rate of 0.010 yr−1.
Information on pathways and rates of decomposition of coarse woody debris (CWD) from one of the dominant boreal tree species – Siberian larch (Larix sibirica Ledeb.) – is scarce. We examined presence and distribution of internal decay in its living trees and decomposition rates in an 88-year chronosequence of logs in an old-growth mesic mixed European boreal forest. Fifty-two percent of the trees started decaying prior to death. Butt or stem rot was caused by white- and brown-rot biotrophic fungi in almost equal proportions. Those trees lost on average 29% of their initial wood mass. The mean decomposition rate of wood as related to initial conditions was 0.007 yr−1 for wood with initial biotrophic decay and 0.010 yr−1 for wood with saprotrophic decay. Bark lost its mass and volume faster – at a rate of 0.056 yr−1. The rate of carbon (C) loss for the whole stem was 0.024 yr−1 in wood affected by saprotrophic fungi and 0.007 yr−1 when the tree was affected by biotrophic fungi. When calculating C losses due to decomposition, separating bark and wood with different C concentrations and decomposition patterns as well as the rate of biotrophic and saprotrophic decay enables us to refine estimates of the role of Siberian larch CWD in C cycling. Further research is still needed to resolve uncertainties around the role of fungal communities and the origins and decomposition rates of butt rots and stem rots in living trees of Siberian larch, as well as the distribution patterns of these fungi and decomposition processes in individual trees and at the ecosystem level.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Decomposition of tree log bark is characterized by complex dynamics.•It integrates bark mineralization, peeling, consumption by insects and sloughing.•Log bark characteristics do not necessarily ...correlate with CWD decay class.•The decomposition rate averaged 0.147yr−1 for birch, aspen and spruce log bark.•Scots pine bark had the highest decomposition rate (0.291yr−1).
Decomposition of coarse woody debris (CWD) bark is characterized by complex and poorly understood dynamics with unclear implications for carbon and nutrient cycling and biodiversity. We examined changes in cover and physical parameters through decomposition of bark attached to logs of the main tree species in an old-growth middle boreal forest. In a 66yrs long chronosequence after tree death and fall, we analyzed changes in the following parameters of log bark: cover, moisture, area-specific mass, total mass, dry bulk density, thickness and proportion of phloem. The percent of bark left on the sampled stems decreased with time since tree death and averaged 38%, 61% and 86% for Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and silver and downy birch (Betula pubescens and Betula pendula)=aspen (Populus tremula), respectively. Bark moisture increased along with succession of epixylic vegetation on logs that progressed similarly for all studied tree species. On average, no vegetation was recorded on logs 3yrs after tree death. In 9yrs, logs were characterized by the first stage of sparse vegetation cover. The closed groups of the second stage, with cover of not less than 70%, consisted mainly of non-epigeous species, and developed an average of 19yrs after tree death. The third stage was dominated by ground cryptogam species without a significant contribution of vascular plants, and the fourth stage, when the wood was completely overgrown by the establishment and spread of vascular plants, was observed and average of 30yrs after tree death. The exponential rate of total mass loss of bark increased at rates of 0.068, 0.110, 0.197 and 0.312yr−1 for birch, aspen, spruce, and pine, respectively. The highest rate of bulk density loss was recorded for aspen (0.024yr−1) and did not differ for birch, pine and spruce (0.009yr−1). The decomposition rate was expressed as a rate of bark mass loss divided by initial volume (integrating losses due to bark mineralization, peeling, consumption by insects and sloughing from logs). It averaged 0.147yr−1 for birch, aspen and spruce and 0.291yr−1 for pine, independent of stem section, log diameter and decay class. In old-growth forests, where CWD volumes may reach hundreds of cubic meters, the accurate portrayal of bark decomposition patterns is crucial for estimating the role of CWD in carbon and nutrient cycles and the diversity of CWD-dependent organisms with different habitat requirements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
As the development of the eight‐toothed spruce bark beetle Ips typographus is temperature‐dependent, climate change may encourage development of its additional generations per year and facilitate ...mass outbreaks further north than previously known.
The aim of the study was to analyse historical changes in effective temperature sums (ETSs) and early season swarming weather for I. typographus in different forest zones of European Russia between 1960 and 2016. The difference in ETSs was analysed with linear regression using daily temperature data from the 30 meteorological stations. Historical data regarding the location of I. typographus outbreaks were examined and changes in their distribution during the entire study period were analysed.
There was a substantial increase in ETSs, especially in the latter half of the study period. Increased ETSs coincided with more favourable conditions for swarming of I. typographus. Areas with favourable ETSs for the complete development of bivoltine populations of I. typographus (>1500 DD) shifted northwards on average 450 km during the entire study period.
The northward shift of ETSs may enhance the transition from univoltine to bivoltine life cycles of I. typographus in the south and middle taiga and from bivoltine to trivoltine life cycles in conifer‐broadleaf forests.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Narrowing the uncertainties in carbon (C) and nitrogen (N) dynamics during decomposition of coarse woody debris (CWD) can significantly improve our understanding of forest ecosystem functioning. We ...examined C, N and pH dynamics in the least studied CWD component—tree bark in a 66-year-long decomposition chronosequence. The relative C concentration decreased by ca. 32% in pine bark, increased by ca. 18% in birch bark and remained stable in spruce and aspen bark. Nitrogen increased in bark of all tree species. In conifer bark, it increased along with epixylic succession. Over 45 years, the relative C/N ratio in bark decreased by 63 and 45% for coniferous and deciduous species, respectively. Bark pH did not change. Due to bark fragmentation, the total C and N amounts in bark of individual logs of aspen, birch, pine and spruce decreased at average rates of 0.03, 0.02, 0.26 and 0.05 year
−1
, and 0.02, 0.02, 0.03 and 0.03 year
−1
, respectively. At the forest stand level, the total amounts of C and N in log bark were 853 and 21 kg ha
−1
or 11.2 and 45.5% of the C and N amounts stored in downed logs and ca. 2.3–3.8 and 2.2–2.4%, respectively, of total C and N amounts stored in forest litter. In boreal forests, decomposing log bark may act as a long-term source of N for wood-inhabiting communities.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
6.
The ingot geometry effect on the axial shrinkage Romashkin, Alexander Nikolaevich; Malginov, Anton Nikolaevich; Tolstyh, Dmitriy Sergeevich ...
Kompʹûternye issledovaniâ i modelirovanie (Online),
2/2015, Volume:
7, Issue:
1
Journal Article
Peer reviewed
Open access
There was studied the effects of ingot geometry changes on axial shrinkage. The investigation was carried out on the basis of 65-t ingot solidification computer simulation.
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