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Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Objective] This study analyzed the diurnal transpiration of Larix gmelinii stand and its responses to environmental factors to further clarify regulation mechanism of environmental conditions on stand transpiration. [Method] During the growing season of June to August in 2018, trees in the sample plot of L. gmelinii forest were divided into three diameter classes according to diameter at breast height, and one tree was selected for each diameter class. The stem sap flow density was measured by thermal probe technology, and the stand evapotranspiration was obtained by scale expansion. The net solar radiation (Rn), air temperature (Ta), relative humidity (RH) and soil moisture were observed simultaneously. Soil water content (SWC), photosynthetically active radiation (PAR) and other environmental factors as well as response of stand transpiration to environmental factors were analyzed by Pearson correlation analysis, principal component analysis and multiple regression fitting. Based on decoupling connection number (Q) and diurnal variations of transpiration, the dominant period of transpiration was determined by net solar radiation (Rn) and water vapor pressure deficit (VPD). [Result] (1) The daily transpiration of L. gmelinii stands from June to August was 0. 41-1. 44 mm/d, and average daily transpiration was in the order of July (0. 85 mm/d) >August (0. 65 mm/d) >June (0. 64 mm/d). (2) Pearson correlation analysis showed that main environmental factors affecting daily transpiration were Rn, Ta and SWC with absolute correlation coefficients in the order of SWC (0. 657) > Ta(0. 383) >Rn(0. 318). (3) Through principal component analysis, environmental factors affecting transpiration of L. gmelinii stand included plant growth factors (WS, SWC and PAR), water change factors (Rn, RH and SWC), and daily transpiration driving factors (Ta and Rn). The contribution rates of Ta and Rn to transpiration of L. gmelinii stand were in the order of Rn (61. 36%) >Ta(38. 64%). (4) Based on diurnal variations of decoupling connection number and stand transpiration, Rn dominant period was from 05:30 to 13:00 and VPD dominant period was from 13:00 to 02:50 of next day. [Conclusion] The main environmental factors affecting daily transpiration of L. gmelinii stand were Rn and Ta. On diurnal scale, Rn and VPD dominated daily transpiration with different dominant periods. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The altitudinal patterns of soil fungi have attracted considerable attention; however, few studies have investigated the diversity and community assembly of fungal functional guilds along an altitudinal gradient. Here, we explored ectomycorrhizal (EcM) and saprotrophic (SAP) fungal diversity and community assembly along a 470 m vertical gradient (ranging from 830 to 1300 m) on Oakley Mountain, sampling bulk soils in the 0–10 cm and 10–20 cm soil layers of Larix gmelinii-dominated forests. Illumina MiSeq sequencing of the ITS genes was employed to explore the fungal community composition and diversity. The relative abundance of EcM and SAP fungi showed a divergent pattern along an altitudinal gradient, while we observed a consistent altitudinal tendency for EcM and SAP fungal diversity and community assembly. The diversity of both fungal guilds increased with increasing altitude. Altitude and soil moisture were the key factors affecting the community composition of both fungal guilds. In addition, the plant community composition significantly affected the EcM fungal community composition, whereas the dissolved organic nitrogen and ammonium nitrogen contents were the driving factors of SAP fungal community. Despite the effects of vegetation and soil factors, EcM and SAP fungal communities were mainly governed by stochastic processes (especially drift) at different altitudes and soil depths. These results shed new light on the ecology of different fungal functional guilds along an altitudinal gradient, which will provide a deeper understanding of the biogeography of soil fungi.

Drought is a critical and increasingly common abiotic factor that has impacts on plant structures and functioning and is a challenge for the successful management of forest ecosystems. Here, we test the shifts in leaf morpho-anatomical or hydraulic traits and plant growth above ground caused by drought. A factorial experiment was conducted with two gymnosperms (Larix gmelinii and Pinus koraiensis) and two angiosperms (Fraxinus mandshurica and Tilia amurensis), tree species grown under three varying drought intensities in NE China. Considering all the species studied, the plant height (PH), root collar diameter (RCD), and plant biomass (PB) were significantly decreased by drought. The leaf thickness (LT) increased, while the leaf area (LA) decreased with drought intensity. In the gymnosperms, the mesophyll thickness (MT) increased, and the resin duct decreased, while in the angiosperms the palisade mesophyll thickness (PMT), the spongy mesophyll thickness (SMT), and the abaxial (ABE) and adaxial epidermis (ADE) thickness were increased by drought. The correlation analysis revealed that P. koraiensis and F. mandshurica had the higher RMF and total plant biomass, but the least LMF, suggesting drought tolerance. In contrast, the L. gmelinii had the least RMF and higher LMF, suggesting vulnerability to drought. Similarly, T. amurensis had the higher leaf size, which increased the evaporative demand and depleted the soil water quickly relative to the other species. The interrelation among the morpho-anatomical leaf traits was equally affected by drought across all the studied species, suggesting that there is no clear evidence to differentiate the taxa based on drought resistance vs. drought tolerance. Thus, we have identified some easily measurable traits (i.e., LMF, RMF, and PB) which evidenced the seedling’s ability to cope with drought and which therefore could be used as proxies in the selection of drought tolerant species for reforestation in the temperate forest.

Background and aim: Boreal forests account for one third of terrestrial carbon stock. Wildfires are an important perturbation of this carbon pool, affecting in particular the litter layer. After forest fires, the litter layers may possess shifting chemical property and decomposition dynamics due to the changes in post-fire vegetations succession and abiotic factors. Methods: We measured water-soluble organic carbon (WSOC) and water-soluble nitrogen (WSN) in the litter layers of Oi and Oe horizons in boreal forests along a gradient of fire history in northeastern China. Results: We found that WSOC and WSN concentrations in the Oi layer were higher than those in the Oe layer. The concentrations were markedly altered by fires and showed different responses to the ecological succession. The time since fire had significant positive correlations with WSOC in Oi and Oe layers. Interestingly, the distance-based redundancy analysis and the structural equation model analysis indicated that factors additional to the time since fire also strongly influenced the litter water-soluble matter (WSM) properties. Biotic factors were more strongly correlated with the litter WSM properties in the Oe layer than in the Oi layer. Although biotic factors contributed less than abiotic factors to the WSM properties, they still play significant roles in litter WSM in burned area. Conclusions: Our results show that manipulating biotic factors can be an important management strategy for litter WSM restoration, which can assist the overall ecological restoration in burned forests faced with the increasing danger of wildfires in the changing global climate. [ABSTRACT FROM AUTHOR]

The Daxinganling Region, in Heilongjiang Province, China, has experienced considerable losses to forest resources owing to a recent increase in forest fire frequency. This necessitates the predictions of fire behaviour in this region, which requires assessment of fuel moisture content (FMC) at appropriate space and time intervals. Here, we compare and extrapolate results of vapour-exchange methods for predicting hourly moisture contents of downed wood. The FMC of larch and birch twig fuels was measured at 1-h intervals at different slope positions with respect to meteorological factors. The twigs were categorised based on diameter and degree of decay. The Nelson and Simard methods (which consider equilibrium moisture content and the associated time lag) and direct regression method (which allows direct attainment of the FMC) were used. Both Nelson and Simard methods predicted hourly twig moisture content more accurately than the direct regression method. The Simard method was the most accurate, with the lowest mean absolute error and mean relative error as well as relatively small variation coefficients based on results of the extrapolation analysis. Further, the resulting models applied to needle-leaved and lightly decomposed fuels performed better than for the broad-leaved and badly decomposed fuels on evaluation parameters. As fuel moisture affects fuel ignition potential and fire behaviour, this study was aimed to determine whether vapour-exchange methods could be used for determining hourly twig fuel moisture content in larch and birch twigs in the Daxinganling Region, China, which is adversely impacted by frequent forest fires. [ABSTRACT FROM AUTHOR]

Post-fire recruitment plays a crucial role in enhancing forest resilience. While previous research highlights the importance of early post-fire forest recovery in determining future forest structure, little has breen reported on whether this relationship exists in the boreal coniferous forests of Eastern Siberia. Additionally, there is a lack of research on whether there are differences in the driving mechanisms that affect juvenile recruitment across different timescales. This study compared key biophysical factors affecting recruitment across short-term and long-term timescales. Leveraging field data and dendrochronological techniques, we determined the germination years of saplings and seedlings in 73 plots across eight fire times. We quantified annual recruitment and cumulative recruitment rates post-fire for each plot, examining the correlation between the time to achieve 75% cumulative recruitment post-fire and the number of recruits, thereby assessing the importance of initial recruitment. Utilizing spatial Generalized Linear Mixed Models (GLMMs), we inferred the impact of biophysical factors on recruitment across short- and long-term timescales. Subsequently, we visualized the relationship patterns between predictor variables and recruitment. The findings revealed that plots with a faster post-fire recruitment pace exhibited a greater quantity of recruitment. On long-term timescales, growing-season mean temperature (GSMT) exhibited a positive correlation with Larix gmelinii recruitment. Basal area demonstrated a robust positive effect on Larix gmelinii recruitment, displaying significance at long-term timescales. The stand age between 60 to 150 years, representing the middle-mature stage of Larix gmelinii , is conducive to post-fire recruitment. Downed dead wood (DDW) exhibited a highly significant boost to recruitment at both timescales, albeit with a relatively weaker effect observed at the long-term scale. Our findings provide some confirmation of the critical role of immediate post-fire recruitment in forest resilience, while also unveiling timescale effects that influence the mechanisms of post-fire recruitment. The findings furnish timely new perspectives on integrating temporal scales into model predictions of the recovery process and adaptive forest management strategies. ● The Great Xing'an Mountains region is primarily affected by non-stand replacing surface fires. ● Plots with faster cumulative recruitment rates also exhibited greater recruitment. ● Downed dead wood significantly facilitates the recruitment of Larix gmelinii. ● The relationship between biophysical predictors and recruitment differed slightly on short-and long-term timescales. [ABSTRACT FROM AUTHOR]

Decomposition processes in larch forests, which occupy a significant part of the boreal zone and are most frequently affected by devastating ground fires, are poorly researched. In the course of a long-term (850 days) field experiment, the decomposition of litter types typical for boreal larch forests of the Russian Far East (needles, leaves, branches, and grass) was monitored in larch stands, both natural ones and those disturbed by fire. The following litter parameters were measured: mass loss, carbon (C) and nitrogen (N) dynamics, respiration, and environmental conditions (temperature and humidity). It is established that, 15 years after a long-lasting ground fire, the inflow of C and N with ground litter has decreased 2.2 times in comparison with the prefire level. At this stage of post-fire succession, the share of tree litter is lower, while the share of low-lignin grass litter is higher in comparison with the control. No differences in mass loss rates were identified between the studied stands for leaves, grass, and branches. However, at the end of the experiment (day 850, p = 0.0035), needles were decomposing more slowly in the burned larch forest than in the control. A lower CO2 emission intensity featured by the needle litter in the postfire forest (p = 0.0207) in comparison with the control and a lower nitrogen content in decomposing needles at later stages of the experiment (p = 0.0234) indicate that the post-fire factor inhibits microbiological activities. A decrease in the total N inflow with litter in the post-fire stand, combined with a lower needle decomposition rate, results in a slower release of nitrogen and its availability to plants and microorganisms, which may affect the restoration of boreal larch forest ecosystems damaged by fires. [ABSTRACT FROM AUTHOR]

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Boreal forests have been evidenced to be highly sensitive to enhanced nitrogen (N) deposition due to prevailing N limitations, and external N inputs from atmospheric deposition are expected to alter plant nutrient stoichiometry. Previous studies have mostly focused on the dominant tree species while neglecting understory plants that often play important role in the nutrient cycles in forest ecosystems. By conducting a six‐year N‐addition experiment with four treatments of 0 (control), 20 (low N), 50 (medium N), and 100 (high N) kg N·ha−1·yr−1 in a boreal forest in Northeast China, we assessed the responses of leaf nutrient stoichiometry (N, phosphorus [P], potassium [K], calcium [Ca], and magnesium [Mg]) for tree, shrubs, and grass. Although the responses of different species to N addition varied, six‐year N addition, especially the medium and high N treatments, generally increased the leaf N concentration and decreased the leaf P and Ca concentrations. As a result, the foliar N:P, N:K, N:Ca, and N:Mg ratios increased consistently across plant functional groups under the high N addition compared with the control, and the grass Deyeuxia angustifolia showed a larger increase in its foliar N:P, N:Ca, and N:Mg than the shrubs. The leaf N concentration increased consistently with soil inorganic N in a nonlinear saturating form, while the other leaf nutrients either decreased (P, Ca) or were not affected (Mg, K) by the soil N availability. Consequently, the foliar N:P, N:K, N:Ca, and N:Mg ratios increased linearly with increasing soil N availability. In spite of this alteration of the leaf nutrient stoichiometry with increasing soil N availability, foliar nutrients and their stoichiometry were less affected under the low N treatment in both trees and understory plants, suggesting minor effects of current N deposition rates on the foliar nutrient balance in boreal forests. [ABSTRACT FROM AUTHOR]

To accurately estimate the age of individual tree and to achieve full-cycle sustainable management of natural Larix gmelinii forest in Great Xing'an Mountains of northeastern China, we constructed individual tree age prediction model using stepwise regression and random forest algorithms based on 44 fixed plots data and 280 stan-dard tree cores obtained from the Pangu Forest Farm. We analyzed the influence of stand structure, site conditions, and competition index on the accuracy of model prediction. The model was evaluated by the coefficient of determination ( R 2 ), root mean square error (RMSE), and mean absolute error (MAE). The results showed that the random forest model had the highest prediction accuracy when number of decision trees was 1500 and number of node con-tention variables was 8. The random forest model had better accuracy and prediction ability than the stepwise regression model, with R 2 , RMSE and MAE of 0.5882, 9.9259 a, 8.1155 a. Diameter at breast height was the most important factor affecting age prediction (83.8%), followed by tree height (34.4%), elevation (17.9%), and basal area per hectare (17.5%). The random forest algorithm exhibited better adaptability and modeling effect on constructing a predictive model for individual tree age. This research contributed to improving the accuracy of growth and harvest estimation for L. gmelinii , and could provide a reference for other scientific studies related to tree age estimation in forests.

Dahurian larch (Larix gmelinii Rupr.), Korean spruce (Picea koraiensis Nakai), and Manchurian fir (Abies nephrolepis Maxim) are valuable tree species of northeast China. Management tools are required for these species to support the industrial and ecological development of forest ecosystems of China. This study aimed to develop taper equations for these species. Five well-known taper equations from two groups (segmented and variable form taper models) were evaluated using the fixed- and mixed-effect modeling. The models were independently fitted utilizing diameter and height datasets comprising 473 trees. A third-order continuous autoregressive error structure (CAR (3)) was used to account for autocorrelation. The model of Clark et al. (1991. Stem profile equations for southern tree species. Asheville, NC: USDA Forest Service. Research Paper, SE-282. doi:) was superior to other models for estimating diameter, merchantable volume, and stem volume when upper stem diameter at 5.3 m was available or predicted. After model comparison, the best Clark et al. (1991) model was refitted as a nonlinear mixed-effects model. This study also demonstrated that the fixed-effect model of Clark et al. (1991) was more accurate than Kozak (2004) mixed model when the later was calibrated for upper stem diameter at 5.3 m with validation data. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Remote Sensing is the property of Editorial Office of Journal of Remote Sensing & Science Publishing Co. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Management of post-fire forest is essential for carbon cycling and forest ecosystem. Effects of post-fire logging on soil respiration have not been well studied, in particular in permafrost regions. We examined soil respiration rate, soil temperature and soil moisture during two growing seasons within the permafrost area of Daxing’anling in northeastern China. We were interested in the effects on soil respiration of (1) the forest fire and (2) the post-fire salvage logging. Soil respiration was measured by applying LI-8100 (LI-COR Inc.) measurement system. Heterotrophic soil respiration was measurement with the trenching method that cut off the roots resulting in root death without removing them. Our results indicated that the autotrophic soil respiration significantly increased after fire (P < 0.05). Selective-cutting increased both total soil respiration and heterotrophic soil respiration, while clear-cutting reduced soil respiration and both respiration components. Soil respiration of the selective-cut plot were significantly higher than that of the clear-cut plot (P < 0.05). Fire was associated with an increase in the share of autotrophic soil respiration, while salvage-logging of post-fire forest reduced this share, as the ratio of autotrophic soil respiration in the clear-cut plot was significantly lower than that in the unlogged area (P < 0.05). With increasing salvage logging intensity after fire disturbance, soil temperature increased. The varying and somewhat contradicting effects of different logging practices on soil respiration in burnt forest ecosystems require more studies to disentangle the effect of salvage logging and fire on soil respiration. [ABSTRACT FROM AUTHOR]

Purpose: Climate change, particularly rising atmospheric carbon dioxide (CO2) concentration, can influence carbon (C) and nitrogen cycling (N) in different forest ecosystems. The major objective of this study was to quantify the long-term physiological and tree growth trends of Larix gmelinii plantation in a boreal environment of northern China in response to elevated atmospheric CO2 concentration and other climatic conditions. Materials and methods: Tree rings were extracted from four Larix gmelinii sample trees, located in a boreal plantation forest of Mohe City, Heilongjiang Province, China. Tree rings were measured with a mean annual basal area increment (BAI), while tree ring stable C isotope composition (δ13C) and N isotopic composition (δ15N) as well as total C and N concentration were measured on mass spectrometer at 3-year intervals. Tree intrinsic water use efficiency (iWUE) was calculated using tree rings δ13C and atmospheric δ13C data. Multiple regression analysis was used to quantify the BAI and WUE relationships with atmospheric CO2 concentration, temperature, precipitation and humidity of the study site. Results and discussion: The results showed a quadratically decrease in relative humidity over the past 60 years with rising temperature, indicating the initial increasing water availability, which is peaked, but increasing water limitation thereafter. Tree iWUE continued to increase as atmospheric CO2 concentration (Ca) increased. Tree BAI showed a quadratic relationship with atmospheric CO2 (Ca), increasing initially, but peaking at the critical threshold of 352.5 ppm or in 1986, and decreasing with the Ca thereafter. Tree ring δ15N, an index of N availability, also responded non-linearly to the rising Ca, increasing initially with the Ca, but peaking at the critical Ca of 348–367 ppm and decreasing thereafter with the rising Ca, indicating the decreasing N availability in the last 20–30 years after the Ca continued to rise. Conclusions: The iWUE of Larix gmelinii continued to increase under rising Ca, but this increased iWUE did not translate into tree growth consistently due to increasing water and N limitation in the boreal forest ecosystems under intensifying climate change in the last 20–30 years. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) plates are new components in modern wooden building structures and have good integrity, stability, and high strength. However, the bending performance of CLT plate is affected by the stacking method of laminates. This study adopted two different stacking methods (three-layer cross and four-layer cross) to make four CLT two-way slabs by using Larix gmelinii slab and polyurethane structural adhesive as raw materials. The slabs were divided into two groups to reveal the effects of stacking method on the bending performance of CLT two-way plates. A jack was used to apply concentrated load on a single point of the middle span of slabs, and the strain, deflection, and ultimate load data were measured. The crack development and failure mode were observed. The ultimate failure characteristics and failure mechanism were discussed, and the finite element model of CLT two-way slab was established using structural analysis software. The influence of elastic-plastic and plywood layers on the bending properties of CLT two-way slab was analyzed, and the results were compared with the experimental results. Results show that the failure modes of CLT two-way slabs are mainly from the transverse grain tensile failure of the slab bottom, and the bearing capacity decreases rapidly when the load reaches to approximately 80% of the ultimate load. For the same thickness of CLT plate, the flexural capacity of four-layer plate is increased by 14.08%, and the elastic bending stiffness is increased by 13.63% compared with three-layer plate. The overall bearing capacity and flexural stiffness of a two-way CLT slab with the same thickness can be improved by increasing the number of laminates when four sides are simply supported. The optimal number of laminates is five. The result of finite element simulation aligns with the test, showing that the test results and analysis are reliable. This study can provide references for future engineering design. [ABSTRACT FROM AUTHOR]

Crop tree management (CTM) is a widely applicable silviculture technology that is used to improve the performance of individual trees. However, only little information is available about the effects of the CTM regime on the soil microbial community structure. We conducted a study to explore the effects of short-term (five years) CTM on the soil bacterial and fungal diversity, community composition, and structure in the 0–10 cm soil layer in a Larix gmelinii (Rupr.) Kuzen. plantation. We set out to investigate the differential response of bacterial and fungal communities to variations in soil properties mediated by short-term CTM. Compared with the control plots, the soil microbial biomass carbon and microbial biomass nitrogen in CTM increased significantly by 64.2% and 32.3%, respectively. CTM significantly promoted the content of soil organic carbon, dissolved organic carbon, and nitrate nitrogen, and reduced the content of dissolved organic nitrogen. CTM changed the Shannon and Simpson indices of soil fungi to a remarkable extent but had little effect on the α diversity of bacterial communities. The bacterial β diversity was more sensitive to CTM than fungi. The relative abundance of Verrucomicrobiae (the dominant class of soil bacteria) in CTM was significantly increased by 78.2%, while the relative abundance of Agaricomycetes (dominant class for soil fungi) was reduced by 43.3%. We observed a significantly increased number of unique OTUs for soil fungi in the CTM plots. Redundancy analysis showed that dissolved organic carbon, soil moisture, and total phosphorus content significantly affected the composition of bacterial communities, while soil dissolved organic nitrogen, C/N, and total phosphorus drove the high variation in fungal community composition. Overall, our results emphasize the divergent response of soil bacterial and fungal communities in Larix gmelinii plantations to short-term CTM. We must pay more attention to the functional role of soil microbiota in future forest management.

The purpose of this paper is to develop a method of constructing density distribution charts in roundwood log based on the density values obtained with a resistograph. The problem of improving the performance properties of structures made of wood and wood-based composite materials and laminated products is particularly relevant for construction in the northern regions. The experience of building in Yakutia shows sufficient reliability and durability of structures made of larch wood, despite the fact that their use is associated with technological challenges: larch planks warp and crack during the drying process; rigidity of wood increases. These disadvantages are caused by the structural features of the wood material; the degree of their intensity is proportional to the index of wood density. This paper presents the methods and results of qualitative research on wood indices obtained in laboratory and field conditions, as well as the authors' methods of graphical representation of density distribution in the cross and axial sections of a tree trunk, which are based on measurements taken via the method of oriented drilling. In the experimental studies, we performed a comparative analysis of the two-dimensional charts of density distribution with the charts of velocity distribution of acoustic pulses produced by a sonic tomograph "Arbotom". The elaborated method of evaluating the quality indicators of forest resources contributes to the expansion of the boundaries of wood-based material utilization, reduces their cost and improves the quality of construction of wooden structures and buildings.

Abstract Root turnover is a key process contributing to soil carbon storage, nutrient cycling, and other ecosystem functions. However, quantifying root turnover rates remains highly uncertain and methodologically challenging. Field rhizotrons were employed to quantify root turnover times using median longevities of five branching orders in a Larix gmelinii plantation. Root images were recorded by scanning the rhizotron windows at a monthly interval during four growing seasons. Root demographic data and branching orders were obtained by analyzing these images using Rootfly software coupled with manual mouse‐tracing of individual roots. Root longevities and turnover estimates were calculated using these data. Roots of different branching orders showed significantly different turnover times. The mean turnover times of the first‐order roots and second‐order roots were 284 and 994 d, respectively. Roots of higher branching orders (third to fifth orders) remained alive at the end of the 4‐yr experimental period, indicating much longer turnover times than the duration of the experiment. Root turnover times increased exponentially with branching orders. Further analysis of these data suggested that root branching orders combined with sampling biases, timing of root cohorts, and longevity distribution patterns crucially influenced root turnover times. The method of combining field glass rhizotrons with electronic scanning permits quantification of root turnover for five branching orders in a temperate forest. The overall result empirically demonstrates the crucial role of branching orders for accurately quantifying root turnover times.

Secondary mixed forests of larch and birch are common in the mountainous areas of north-eastern China. In the Daxing'an Mountain of Heilongjiang Province, the larch species of this type of forest is Larix gmelinii Rupr. and the birch species is Betula platyphylla Suk. Science-based information on the optimal sustainable management of these forests is largely missing. Since the forests serve multiple functions, including soil protection, carbon sequestration and maintenance of habitats, only continuous cover forestry is regarded acceptable. This study optimized a sequence of transformation cuttings of mixed secondary forests of larch and birch to sustainable steady-state uneven-aged structure. The optimization problem was formulated in such a way that the species composition of the steady-state forest was also sustainable. A reference management scenario was obtained by letting the stands grow for 100 years without any cuttings. The results showed that the no-management option leads to low rate of regeneration and ingrowth, and the stands do not develop towards typical uneven-aged structures. Maximizing net present value without any constraints leads to heavy cuttings, making these schedules unacceptable from the soil protection and carbon storing point of views. Schedules that were evaluated as the most recommendable were obtained by adding a minimum basal area constraint to the problem formulation, and maximizing species and size diversity of the steady-state forest simultaneously with net present value. [ABSTRACT FROM AUTHOR]

A total of 10 sub-regions were identified and tree total volume equations were developed for economically important Dahurian larch species in northeast China (Daxing’an Mountain region/Heilongjiang province). These equations were based on a simple power function and adjusted to the forest inventory data volumes of three mountainous regions, including the northwest of northern slope of Yilehuli Mountains (NWYLHLM), the southeast of northern slope of Yilehuli Mountains (SAYLHLM) and the eastern slope of northern part of Daxin’an Mountains (NDXAM). The volume equations were tested to determine if differences by ecoregion were statistically significant. Results varied by species, volume and ecoregion suggesting that the relationship between tree volume and tree diameter of Dahurian larch (Larix gmelinii Rupr) tree species is significantly different between the three geographic regions, depending on local climatic, soil and ecological conditions. This implies that the provincial and regional models of volume-diameter relationships are not appropriate for predicting tree volume at ecoregional level. In addition, the use of an ecoregional specific model will lead to significant bias in predicting the total volume of trees. The ecoregion-based volume models developed in this study could provide more accurate information on tree growth and development to forest resource managers and planners. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A comparative study of karyotypes of two Siberian species of larch—L. sibirica and L. gmelinii—growing in the zone of forest-tundra on the Taimyr Peninsula was carried out. The number of chromosomes has been analyzed and the increase in chromosomal instability in larches in forest-tundra conditions has been shown. The size and morphology of chromosomes and the localization and frequency of secondary constrictions in chromosomes of L. sibirica and L. gmelinii were estimated. The parameters of chromosomes in polyploid cells of L. gmelinii were studied. The asymmetry of karyotypes of L. sibirica and L. gmelinii was analyzed. The spectrum and frequency of chromosome rearrangements in L. sibirica and L. gmelinii were studied. Using the data of the karyological analysis, the issues of differentiation and adaptation of the investigated larch species in Taimyr are discussed. [ABSTRACT FROM AUTHOR]

Taking Larix gmelinii from Greater Khingan Mountains as the research object, four nitrogen( N) treatment level plots with unified site conditions were established in Nanwenghe Nature Reserve of Greater Khingan Mountains, included contrast CK( CK, 0 g N/( m2·a)), low nitrogen( LN, 2. 5 g N/( m2·a)), middle nitrogen( MN, 5 g N/( m2·a)), high nitrogen( HN, 7. 5 g N/( m2·a)). The contents of C、N、P、K、Ca、Mg in leaves, roots and fresh leaves were determined under different N addition gradient.The purpose was to elucidate the aboveground organ leaves and underground organ roots of Larix gmelini. The distribution pattern of each element content and stoichiometry ratio revealed the heavy absorption rate of each element before leaf litter and discussed the relationship between each nutrient element and response to different levels of N application. The results showed that:( 1) C、N、P of fresh leaves, roots and littered leaves ranged from 393. 174-518. 362 mg/g, 4. 405-23. 963 mg/g, and 0. 743-1. 671 mg/g. The range of C and P content in leaves was the highest, and the lowest in roots.( 2) LN, MN, HN significantly increased N content in roots, and MN, HN significantly increased N content in roots. There were significant differences in plant nutrient content in different organs.( 3)The plant leaves were enriched to Ca and reabsorbed to the elements. It conclude that the leaf and root were the main factors that affected the chemical measurement ratio and the C, N, P of Larix gmelinii. Under the condition of sufficient nitrogen, nitrogen deposition resulted in the extravagant absorption of N and P by Larix gmelinii, which could increase the decomposition rate of litter leaves and nutrient cycling in its ecosystem. [ABSTRACT FROM AUTHOR]

Abstract Although it has been recognized that rising temperatures and shifts in the hydrological cycle affect the depth of the seasonally thawing upper permafrost stratum, it remains unclear to what extent the frequency and intensity of wildfires, and subsequent changes in vegetation cover, influence the soil active layer on different spatiotemporal scales. Here, we use ring width measurements of the subterranean stem part of 15 larch trees from a Sphagnum bog site in Central Siberia to reconstruct long-term changes in the thickness of the active layer since the last wildfire occurred in 1899. Our approach reveals a three-step feedback loop between above- and belowground ecosystem components. After all vegetation is burned, direct atmospheric heat penetration over the first ~20 years caused thawing of the upper permafrost stratum. The slow recovery of the insulating ground vegetation reverses the process and initiates a gradual decrease of the active layer thickness. Due to the continuous spreading and thickening of the peat layer during the last decades, the upper permafrost horizon has increased by 0.52 cm/year. This study demonstrates the strength of annually resolved and absolutely dated tree-ring series to reconstruct the effects of historical wildfires on the functioning and productivity of boreal forest ecosystems at multi-decadal to centennial time-scale. In so doing, we show how complex interactions of above- and belowground components translate into successive changes in the active permafrost stratum. Our results are particularly relevant for improving long-term estimates of the global carbon cycle that strongly depends on the source and sink behavior of the boreal forest zone. Graphical abstract Unlabelled Image Highlights • Tree rings record permafrost active layer dynamics after wildfires. • Post-fire feedback loops exist between above- and belowground forest components. • Increases of the upper permafrost horizon correspond to organic layer growth rates. • Siberian wildfires affect the boreal forest ecosystem at centennial time-scales. • Wildfires induce long-term changes in the terrestrial carbon cycle. [ABSTRACT FROM AUTHOR]

Abstract Both topography and the occurrence of wildfire can strongly affect soil properties in forest successions. Although numerous studies have examined the effects of fire and topography, few have explored their shifting relative importance with time since fire. We measured physical, chemical, and biological soil properties in two topographic positions (north-facing and south-facing) in a Chinese boreal forest along a gradient of fire history. In the control site, topography strongly influenced soil properties, with north-facing slopes having higher soil moisture (SM), depth of organic matter layer (OML), total carbon and inorganic N concentrations, and lower pH, dissolved organic carbon (DOC) and nitrogen (DON). In the 1-year-post-fire site, wildfire erased topographic effects on soil variables, and greater changes in soil properties occurred on the north-facing slopes. The wildfire significantly increased soil pH, DON, ammonium and nitrate, and decreased SM, OML, DOC and microbial biomass, while no significant differences in soil properties appeared between high- and low-severity plots. In the 11-year-post-fire site, most soil properties were similar to the control except for microbial biomass, OML and DOC; topography again became a significant factor in explaining variations in soil properties. Fire severity was highly correlated only with soil pH in the 1-year-post-fire site, whereas topographic factors were always correlated with some soil properties in the three sites. In the 1-year-post-fire site, wildfire explained almost five times more variance than topography for most soil properties, whereas in the 11-year-post-fire site, the proportion of variance explained by topography increased and even surpassed that by wildfire. These results demonstrate that the resilience of Larix gmelinii forest soils might be controlled by wildfires in the short term but by topography in the long term. Graphical abstract Unlabelled Image Highlights • Wildfire reduced topographic effects on soil properties in the 1-year-post-fire site. • Fire severity had no significant impacts on soil properties • Soils could rapidly recover to the pre-fire state except for soil organic matter and microbes. • Correlations between fire severity and soil properties decreased over time, while those with topography increased. • Topography again exerted stronger effects on soils in the 11-year-post-fire site. [ABSTRACT FROM AUTHOR]

A set of 899 L. gmelinii expression sequence tags (ESTs), available at the National Center of Biotechnology Information (NCBI), was employed to address the feasibility on development of simple sequence repeat (SSR) markers for Larch species. Totally, 634 non-redundant unigenes including 145 contigs and 489 singletons were finally identified and mainly involved in biosynthetic, metabolic processes and response to stress according to BLASTX results, gene ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) maps. Approximately 11.7% (74) unigenes contained 90 candidate SSRs, which were mainly trinucleotides (29, 32.2%) and dinucleotides (26, 28.9%). A relatively high frequency of SSRs was respectively found in the Open Reading Frame (ORF, about 54.4%) and 5′-untranslated region (5′-UTR, 31.2%), while a low frequency was observed in the 3′-untranslated region (3′-UTR, about 14.4%). Of the 45 novel EST-SSRs markers, nine were found to be polymorphic at two L. gmelinii populations. The number of alleles per locus (Na) ranged from two to four, and the observed (Ho) and expected (He) heterozygosity values were 0.200–0.733 and 0.408–0.604, respectively. The inbreeding coefficients (FIS) for all loci were more than zero except Lg41. Most of these 9EST-SSR markers were transferable to its related species L. kaempferi, L. principis-rupprechtii and L. olgensis. These novel EST-SSRs will be useful for further research on comparative genomics, genetic resources conservation and molecular breeding in larch trees.

An ionic liquid-based microwave-assisted extraction method (ILMAE) was successfully applied for the extraction of taxifolin from Larix gmelinii. Different kinds of 1-alkyl-3-methylimidazolium ionic liquids with different kinds of cations and anions were studied and 1-butyl-3-methylimidazolium bromide was chosen as the optimal solvent for taxifolin extraction. The optimal conditions of ILMAE were determined by single factor experiments and Box-Behnken design as follows: [C4mim]Br concentration of 1.00 M, soaking time of 2 h, liquid-solid ratio of 15:1 mL/g, microwave irradiation power of 406 W, microwave irradiation time of 14 min. No degradation of taxifolin had been observed under the optimum conditions as evidenced from the stability studies performed with standard taxifolin. Compared with traditional solvent and methods, ILMAE provided higher extraction yield, lower energy and time consumption. The distribution of taxifolin in different parts of larch and the influences of age, orientation, and season on the accumulation of taxifolin were analyzed for the sufficient utilization of L. gmelinii.

An ionic liquid-based homogenate-ultrasound-synergistic technique was proposed to simultaneously extract dihydroquercetin and arabinogalactan from Larix gmelinii stumps. The appropriate extraction solvent of [C 2 mim]Br was screened from thirteen kinds of imidazolium-based ionic liquids. The optimal conditions for the proposed method obtained by response surface methodology were a [C 2 mim]Br concentration of 0.87 mol/L, IL-HUSE time of 24 min, liquid/solid ratio of 14 mL/g, and ultrasound power of 240 W. Under these conditions, the satisfied extraction yields were 53.09 ± 2.24 mg/g for dihydroquercetin and 152.48 ± 5.78 mg/g for larch arabinogalactan. Validation studies suggested that the improved method was capable of extraction of dihydroquercetin and arabinogalactan from L. gmelinii stumps. High extraction yields of dihydroquercetin and arabinogalactan obtained from the recycled [C 2 mim]Br indicated that the proposed method is a highly efficient technique. The present research indicates that the improved process shows promising prospects for application to the preparation of bioactive substances from plant materials. [ABSTRACT FROM AUTHOR]

Soil moisture is a major factor controlling carbon isotope discrimination (Δ13C), which has been demonstrated to decrease under dry conditions in many studies; however, few studies on Δ13C under waterlogging condition have been conducted. In this study, a pot experiment was conducted withLarix gmelinii, a major larch species in the east Siberian Taiga, to investigate the effect of waterlogging on Δ13C during photosynthesis. Assimilation rate and Δ13CRD(instantaneous Δ13C calculated with Rayleigh distillation equation) decreased drastically soon after waterlogging, followed by recovery in their values, which was caused by a change in stomatal conductance. Thereafter, assimilation rate decreased gradually, whereas Δ13CRDdecreased more gently. These results were thought to be caused by the decrease in both stomatal conductance and carboxylation. Our results indicate that extreme wet events may cause a decrease in Δ13C, which is important information for detecting flooding events in the past using tree-ring isotope analyses and for studying impacts of flooding on plants in areas where waterlogging might occur. [ABSTRACT FROM PUBLISHER]

Fine roots play a prominent role in forest carbon flux, nutrient and water acquisition; however, information on fine roots remains scarce due to the limitation of measuring methods. In this study, a nested regression method was used to estimate the biomass and surface area of fine roots of individual Larix gmelinii trees that dominate northernmost China. Aboveground traits including leaf biomass, leaf area, stem volume and aboveground biomass were also investigated. In particular, the relationships between leaves and fine roots, in terms of biomass and area, were examined. The results revealed that allometric models of fine roots, total roots, and leaves consistently fit well with Adj. R2 = 0.92–0.97. The root-shoot ratio at the individual tree level was approximately 0.28. There were robust positive linear correlations between absorption (fine root biomass, fine root surface area) and production (leaf biomass, leaf area) (Adj. R2 = 0.95, p < 0.001). In conclusion, the close coupling between fine roots and leaves presented in this study provides support for the theory of functional equilibrium. [ABSTRACT FROM AUTHOR]

Cavitation hybrid rotation, which was and is still looked upon as an unavoidable nuisance in the flow systems, for extraction processing intensification of active chemical compounds from natural products. In this study, a homogenization-assisted cavitation hybrid rotation extraction method was applied to extract dihydroquercetin (DHQ) from larch ( Larix gmelinii ) wood root. The extraction parameters were optimized in single factor experiments with the DHQ extraction yields as the response values. The optimum conditions were as follows: number of extractions, three; ethanol volume fraction for the extraction, 60%; liquid–solid ratio for homogenization, 10 mL/g; homogenization time, 8 min; liquid–solid ratio for cavitation extraction, 9 mL/g, and cavitation extraction time, 35 min. Under these conditions, the DHQ content in extract was 4.50 ± 0.02 mg/g, and the extraction efficiency was higher than those of traditional techniques. Cavitation can be effectively used to improve the extraction rate by increasing the mass transfer rates and possible rupture of cell wall due to formation of microcavities leading to higher product yields with reduced processing time and solvent consumption. After the extraction process, macroporous resin column chromatography was used to concentrate and purify the DHQ. Three resins were selected from fifteen macroporous resins for further investigation of their performance. Among these resins, AB-8 resin exhibited relatively better adsorption capacities and desorption ratios for DHQ. The ethanol volume fraction of the solutions for sample loading and desorption, and flow rates for loading and desorption were optimized for the macroporous resin column chromatography. [ABSTRACT FROM AUTHOR]

• The unprotected SOC pool is the largest in the Larix gmelinii forests soils. • Physical-chemical and chemical protected SOC pools tended to be saturated. • Unprotected and physical protected SOC pools are still not saturated. • Soil depth presented stronger effects on the SOC pools than forest age and type. • Soil physicochemical properties were crucial for SOC sequestration of each pool. The stability and dynamics of soil organic carbon (SOC) pools in forest soils are crucial for assessing and predicting the effectiveness of forest carbon sequestration. Various factors such as soil depth, nutrients availability, crustal elements, pH, and stand characteristics (tree type, tree age) influence the stability of SOC pools. To better understand SOC stability of cold temperate forest soil, soil samples were collected from 0–10 cm, 10–20 cm, 20–40 cm, and 40–60 cm depths in a Larix gmelinii forest. Then, the distribution characteristics of SOC pools under different protection mechanisms and their influencing factors were examined. Our results showed that the unprotected SOC pool was the highest, while the physical–chemical protected SOC pool was the lowest. Total organic carbon (TOC) had a linear positive relationship with unprotected and physical-protected SOC pools, and a logarithmic positive relationship with physical–chemical protected and chemical-protected SOC pools. Soil depth was the predominant factor affecting the SOC pools of each protection mechanism. The physical–chemical protected SOC pool significantly differed from forest types and forest ages, and the chemical-protected SOC pool was associated with the synergistic effects of forest age and type. Furthermore, soil moisture and acidity, and the crustal elements may play prominent role in the variation of SOC pools in the Larix gmelinii forests. Our findings suggested that the silt- and clay-associated SOC pools in the Larix gmelinii forest soils had approached or achieved saturation, while more organic C was fixed in the relatively active unprotected SOC pool. This unprotected pool was more sensitive to ecosystem change, indicating its importance in assessing forest carbon sequestration. Our study provided insights into the active and dynamic SOC pools in forest soils and their responses to different environmental factors. These findings can be utilized to accurately assess the carbon sink potential of cold temperate forest soils and inform the management of forest ecosystems. [ABSTRACT FROM AUTHOR]