White Birch Forest Research Articles

Effect of In Situ Large Soil Column Translocation on CO2 and CH4 Fluxes under Two Temperate Forests of Northeastern China

Global warming has a significant impact on soil carbon dioxide (CO2) and methane (CH4) fluxes in temperate forests. However, due to a lack of field observations, limited information is available about the responses of soil CO2 and CH4 fluxes to changes in temperature during the non-growing season and throughout the year in temperate forests. The broadleaf and Korean pine mixed mature forest (MF) and adjacent secondary white birch forest (BF) at different succession stages in the Changbai mountain region in northeastern China were selected, to study the effect of in situ soil column translocation on CO2 and CH4 fluxes in temperate forests. On average, the air temperature and soil temperature at 5 cm depth under BF stands from October 2018 to October 2022 increased by 0.64 and 0.42 °C during the non-growing season and by 0.49 and 0.43 °C throughout the year, respectively, compared with those under MF stands. Based on multi-year measurements in field experiments, it was shown that during the non-growing season, fluxes of CO2 and CH4 from soil columns under MF and BF stands ranged from 0.004 to 1.175 and from 0.015 to 1.401 (averages of 0.321 and 0.387) μmol CO2 m−2 s−1, and from −1.003 to 0.048 and from −1.037 to −0.013 (averages of −0.179 and −0.250) nmol CH4 m−2 s−1, respectively, accounting for approximately 20.8% and 25.3%, and 48.8% and 69.1% of the corresponding average fluxes during the growing season. When undisturbed soil columns of MF were transferred to a BF stand, to simulate warming, the cumulative soil CO2 emissions and CH4 uptake increased by 23.5% and 15.3% during the non-growing season, and by 9.5% and 16.3% across the year, respectively. However, when soil columns of BF were transferred to a MF stand, to simulate cooling, the cumulative soil CO2 emissions decreased by 16.9% and 0.1% during the non-growing season and across the year, respectively. Upon cooling, the cumulative soil CH4 uptake decreased by 21.8% during the non-growing season but increased by 15.4% across the year. The soil temperature and moisture at 5 cm depth in soil columns could explain 84–86% of the variability in CO2 fluxes and 16–51% of the variability in CH4 fluxes under the two forest stands throughout the field measurement period. The results of the in situ soil column translocation experiments highlight that a small climate warming in nature can increase soil CO2 emissions and CH4 uptake in the temperate forests of northeastern China, particularly during the non-growing season, which should be considered when predicting soil C fluxes in the temperate forests of northeastern China under global warming scenarios.

Effects of Biotic and Abiotic Factors on Biomass Conversion and Expansion Factors of Natural White Birch Forest (Betula platyphylla Suk.) in Northeast China

Biomass conversion and expansion factors (BCEFs) are widely utilized in national and regional biomass estimates and greenhouse gas reporting, as they can be used to directly transform the stocking volume into biomass. In this study, the power function was used as the basic model form with biotic variables, and abiotic variables were considered to improve the fitting results. Then, the random effects parameters were also introduced into the models to describe the variation of BCEFs among different forest management units. Random sampling strategies were applied to calibrate the random effects. The results showed that the stocking volume exhibited a negative proportional relationship in the stem BCEF (BCEFst), the root BCEF (BCEFro) and the total tree BCEF (BCEFto) models, and the quadratic mean diameter exhibited a positive proportional relationship in the branch BCEF (BCEFbr) and the foliage BCEF (BCEFfol) models. In addition, the fitting effect of generalized models with abiotic predictors was superior to that of the basic models. Considering the effects of abiotic variables on the BCEFs of each component, the results showed that BCEFst and BCEFto decreased as the mean annual precipitation increased; BCEFbr increased as the annual temperature increased; BCEFfol gradually decreased as the elevation increased; and BCEFro first increased with increasing mean annual temperature and then declined. In conclusion, abiotic factors explained the variation in BCEFs for the biomass components of the natural white birch forest. Although the fitting effect of generalized models with abiotic predictors was superior to that of the basic models, the mixed-effects model was preferable for modeling the BCEFs of each component. In addition, the prediction precision of the mixed-effects models enhanced gradually with increasing sample size, and the selection of eight plots for calibration and prediction based on the mixed-effects model was the best sampling strategy in this study of a natural white birch forest.

Environmental Factors Driving the Transpiration of a Betula platyphylla Sukaczev Forest in a Semi-arid Region in North China during Different Hydrological Years

More and more droughts happened during the last decades, threatening natural forests in the semi-arid regions of North China. The increase in drought pressure may have an impact on stand transpiration (T) in semi-arid regions due to rising temperature and changes in precipitation. It is unclear how the transpiration of natural forest in semi-arid regions respond to drought, which is regulated by environmental factors. In this study, a relatively simple but mechanism-based forest stand T model that couples the effects of the reference T, solar radiation (Rn), vapor pressure deficit (VPD), and relative extractable water (REW) in the 0–80 cm soil layer was developed to quantify the independent impacts of Rn, VPD, and REW on T. The model was established based on the observed sap flow of four sample trees, and environmental factors were observed from May to September in different hydrological years (2015, 2017, 2018, and 2021) in a pure white birch (Betula platyphylla Sukaczev) forest stand in the southern section of the Greater Khingan Mountains, northeastern China. The sap flow data were used to calculate tree transpiration (Tt) and T to calibrate the T model. The results indicated that (1) The Tt sharply declined in the ‘dry’ year compared with that in the ‘wetter’ year. The daily Tt for small trees in the ‘dry’ year was only one-fifth of that in the ‘wetter’ year, and the daily Tt of large trees was 48% lower than that in the ‘normal’ year; (2) Large trees transpired more water than small trees, e.g., the daily Tt of small trees was 89% lower than that of the large trees in the ‘normal’ year; (3) Daily T increased with the increase in Rn, and the response conformed to a binomial function. Daily T responded to the rise of VPD and REW in an exponential function, first increasing rapidly, gradually reaching the threshold or peak value, and then stabilizing; (4) The driving factors for the T shift in different hydrological years were the REW in the ‘dry’ year, but the Rn and REW in the ‘wet’, ‘normal’, and ‘wetter’ years. The REW in the ‘wet’ and ‘wetter’ years exerted positive effects on T, but in the ‘normal’ and ‘dry’ year, exerted negative effects on T. Thus, the environmental factors affecting T were not the same in different hydrological years.

Occupancy modeling of habitat use by white‐tailed deer after more than a decade of exclusion in the boreal forest

The exclusion of herbivores in forest areas is a strategy used to reduce the impact of selective browsing and increase the regeneration of desired plant species. On Anticosti Island (Québec, Canada), selective browsing by white‐tailed deer prevents the regeneration of balsam fir – white birch forests leading to their conversion into white spruce forests. Large deer exclosures were established for ca 10–12 years in clear‐cuts with patches of residual forest from 2001 to 2006 to assist in the natural regeneration of fir stands and to provide shelter and food resources for deer. Our objective was to assess how deer use exclosures after the removal of fences according to their spatial configuration and habitat composition. We randomly distributed automatic cameras for periods of 14 days during summer in six exclosures ranging from 3.1 to 11.2 km2 (n = 25 cameras per exclosure) from which deer were reduced for 10–12 years. We compared candidate occupancy models that included spatial configuration and food resource variables while simultaneously controlling for variables affecting detection probability. We obtained weak evidence that deer habitat use increased by 19% when forage resources, represented by the cover of Cornus canadensis, increased from 0 to 100%. None of the other variables (distance between the border of exclosures and cameras and distance between forest patches and cameras) was retained, suggesting that the use of regenerating forests by deer in summer after a period of exclusion is related to forage availability and therefore, any forest management that improves food production during summer should help maintain or increase habitat use by deer.

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.

Ground beetle (Coleoptera, Carabidae) communities as natural indicators of ecosystem restoration on the terminated fly ash dump of the thermoelectric power station (Novosibirsk, Russia)

The aim of the study. The aim of the study was to reveal regularities in the development of ground beetles (Coleoptera, Carabidae)’ communities, to determine their species peculiarities as dependent on soil formation rate and soil ecology in the ecosystems developed on the terminated fly ash dump of the thermoelectric power station over nine years of restoration. Location and time of the study. The main object of the study was a terminated fly ash dump No.1 of the thermoelectric power station No.5 in Novosibirsk, Russia. (54°59' NL, , 83°03' EL). Soil samples were collected in 2019, whereas the ground beetles were collected in 2017 and 2019. Methodology. Six study sites, corresponding to the fly ash dump sedimentation zones, were chosen. The undisturbed white birch forest and clover-brome meadow were chosen as controls representing mature climax ecosystems. Soil cover, developing on the fly ash dump after its termination, was described according to the soil classification of technogenic landscapes, and was shown to consist of various types of embryozems (Technosols). Soil water content on each study site was measured in 0–5cm layer by gravimetric method. Soil samples were collected in May 2019. To collect ground beetles five traps were placed on each study site, each trap filled up to 1/3 of its volume with 4% acetic acid for fixing the trapped beetles. The beetles were collected in May–June 1017 and in June–July 2019. The data obtained were used to calculate α-biodiversity indices and perform cluster analysis using PAST v.3.09 software. Main results. Altogether 74 species of the ground beetle we found: 60 species of ground beetles were identified in the revegetating fly ash dump areas, with 48 species found at the sites amended with potentially fertile substrate (PFS), and 35 species found at the sites without PFS addition. The control sites under birch forest and meadow had 14 and 10 species, respectively. Thus the ground beetles’ abundance in the reclaimed area was almost 3 times greater than in the non-reclaimed area (973 specimens vs. 347). Cluster analysis discriminated three groups in the studied fly ash dump sites, namely dry non-reclaimed sites, dry PFS sites and moist sites. Soil cover of the studied fly ash dump was represented by initial, organic matter accumulating, humus-accumulating and sod embryozems (Technosols). Conclusion. Over nine years of spontaneous restoration at the terminated fly ash dump of the thermoelectric power station species rich and abundant communities of ground beetles were formed. These communities differed significantly from those at the adjacent undisturbed climax ecosystems used for comparison. Species richness and dynamic density of ground beetles was shown to increase from the control sites to non-reclaimed sites and PFS-reclaimed sites. The autonomous position in the catena was found to be occupied by the less evolutionary developed embryozem type, whereas downwards along the catena, i.e. with increasing soil moisture content, identified soil types belonged to higher evolutionary order. Therefore technical recultivation with fly ash dump overlaying with potentially fertile substrate or fertile soil allow accelerating soil cover development, as well as the development of an entire biogeocenosis.

Phytogeography boundaries between Stone-birch and White-birch forests in the North of the Koryak Region

The distribution boundaries of the two birch species communities: Stone-birch (Betula ermanii Cham.) and White birch (Betula platyphylla Sukacz) forests have been firstly reliably established for the North of the Koryak Region. The remote sensing data, aerial observations, original relevés, and itinerary research data were used. A map of the Stone-birch and White-birch forests allocation in the mainland part of the Koryak Region was compiled. It was shown that Stone-birch groves were found in relatively warmer and wetter areas adjacent to the Bering Sea coast. They occupy Southern and South-Eastern slopes of the Koryak Upland spurs; whereas White birch forests are common in the continental districts. They are found in the valleys of the rivers Penzhina, Talovka, Belaya, Oklan, Apukvayam, on the Penzhinskiy Ridge slopes. Stone-birch forests do not occur North of 62° northern latitude, do not overcome the boggy depression of Parapolsky Dale, and do not occur to the West of 167° 30’ eastern longitude. The natural phytogeographical boundary between the areas of the two birch formations are the Southern and South-Eastern spurs of the Koryak Upland.

Taxonomic diversity of bacterial assemblage in technosol of the revegetating fly ash dump

Background. The aim of the study was to assess the composition and structure of bacterial assemblages by estimating 16S rRNA gene sequences diversity in a young Technosol, developing on a revegetating fly ash dump. Location and place of the study. Two soils were chosen for the study in the environs of the thermoelectric power station No.5 in Novosibirsk region: 1) nine years old Technosol (54°59' NL, 83°03' EL), developing on the spontaneously revegetating fly ash dump, and 2) Phaeozem under undisturbed white birch forest (55°00' NL, 83°04' EL). Soils were sampled from the 0-5 cm layer as three individual replicates each. Materials and methods. The total DNA extracted from soil samples was used as a matrix for PCR amplification using V-3-V4 primers for 16S rRNA genes. The obtained amplicons were sequenced on Illumina MiSeq platform in the Genomics Core Facility of the Institute of Chemical Biology and Fundamental Medicine SB RAS (Novosibirsk, Russia). Descriptive statistics and principal components analysis were used to analyze and present the data. Results. Overall 4887 different operational taxonomic units (OTUs) were found at the 97% similarity level; the OTUs were ascribed to 306 genera, 212 families, 123 orders, 84 classes and 32 phyla of bacteria domain. At the phylum level bacterial assemblages in both soils were dominated by Proteobacteria, Acidobacteria and Actinobacteria, showing rather similar outline of the phyla relative abundance, confirming the direction of pedogenesis towards Phaeozem. Higher abundance of Chloroflexi a physiologically diverse phyla with aerobic and anaerobic thermophiles, anoxigenic phototrophs and anaerobes, able to respire organic halides, in the young Technosol complies with harsh edaphic conditions there. Although the relative abundance of Rhizobiales, Actinomycetales and unclassified Acidobacteria_Gp6 and Acidobacteria_Gp3 was found to be 1.5–2.4 times higher in the undisturbed Phaeozem, they also were predominating in the Technosol samples. The α-biodiversity indices, pertaining mostly to species/OTUs richness, i.e. Chao-1, OTUs number, Margalef, Fisher’s alpha, were higher in Phaeozem, whereas evenness and equitability were higher in Technosol. Both soils demonstrated similar Shanno indices, which were rather high (6.3). Conclusions. Nine years of spontaneous revegetation on the terminated fly ash dump of the thermoelectric power station resulted in the development of the Technosol, containing quite rich and diverse bacterial assemblage, which was rather close in structure at the phylum taxonomic level to the adjacent undisturbed Phaeozem. Overall the early stages of pedogenesis were dominated by specific bacterial assemblage (Chloroflexi, Xanthomonadales, Geobacter, Aciditerrimonas, Iamiaceae and some others), performing weathering of the pedogenic substrate, i.e. fly ash. The present of nitrificators (Nitrospira), denitrificators денитрификаторов (Reyranella) together with diazotrophs (Bradyrhizobium, Rhizobiales) dominance evidences the establishment of the entire network of nitrogen transformation process already at the early stages of revegetation of the fly ash dump. Large percentage (17%) of Bacteria, the information about which ribosomal gene sequences is most likely absent in the respective data bases necessitates more detailed research into the soil microbiome on fly ash dumps.

Enhanced spring phenological temperature sensitivity explains the extension of carbon uptake period in temperate forest protected areas

Land surface phenology (LSP) and its trend are important for understanding the vegetation–climate relationship. However, whether LSP and LSP trends for different forest communities vary with the intensity of forest disturbance and the main cause of the change is still unclear. In this study, LSP indicators and their temperature sensitivity (Ts) were obtained for coniferous (Larch Coniferous forests (LC) and Spruce Fir Korean Pine forests (SFKP)), mixed (Broadleaf Korean Pine forests (BKP) and Spruce Fir Broadleaf forests (SFB)), and broadleaf (Aspen White Birch forests (AWB) and White Birch forests (WB)) communities in protected (Fenglin National Natural Reserve, FNNR) and unprotected (Lilin Experimental Forest Farm, LEFF) areas in Northeastern China from remote sensing and climate data. Statistical comparisons of the LSP, LSP trends, and Ts were conducted for various forest communities in both FNNR and LEFF. The results show that the values of mean start of the season (SOS) and mean end of the season (EOS) in FNNR were significantly different from those in LEFF, and the SOS, EOS, and the length of season (LOS) trends for various forest communities in FNNR were significantly different from those in LEFF, except for the SFB. In broadleaf forests, both the mean LOS and LOS trends for various forest communities were significantly higher in FNNR. However, significantly higher LOS but lower LOS trends in FNNR were identified for coniferous and mixed forests. In addition, the SOS Ts for various forest communities in FNNR were significantly higher than those in LEFF, and the Ts for broadleaf forests in FNNR were significantly lower than that in other forest communities. The results of this study suggest that the carbon uptake periods of most temperate forest communities are apparently enhanced by the high spring phenological Ts in protected areas, which provides important insights into future carbon sequestration potential and forest management strategies for temperate forests in Northeastern China.

Effects of freeze-thaw and soil moisture on content and spectral structure properties of dissolved organic matter in forest soil leachates.

The contents and stability of soil dissolved organic matter (DOM) can affect key processes of soil carbon and nitrogen cycle. The responses of DOM content and its spectral structure pro-perties in forest soils to climate change remain unclear. We collected soil samples from two temperate forests, i.e., the broadleaf and Korean pine mixed forest (BKPF) and adjacent secondary white birch forest (WBF), in Changbai Mountains, northeastern China. Using a combination of three-dimensional fluorescence spectrum and parallel factor analysis, a simulated freeze-thaw experiment was conducted in the laboratory. We examined the effects of freeze-thaw intensity, freeze-thaw cycle and their interaction on the content, components and spectral properties of DOM leached from the two forest surface soils with different moisture levels. The results showed that DOM content and components of soil leachates varied with forest types, soil moisture, freeze-thaw intensity and freeze-thaw cycle. The DOM content in the leachates was lowest at medium moisture level and was significantly affected by the high freeze-thaw intensity. In addition, the DOM content increased first and then decreased with the increases of freeze-thaw cycles. Three fluorescence components of DOM in the forest soil leachates were identified as humic acid-like DOM, fulvic acid-like DOM and protein-like DOM. The DOM components of BKPF soil leachates were mainly consisted of fulvic acid-like substances with a high humification index. However, the DOM from WBF soil leachates was dominated by humic acid-like substances with low stability, and the three fluorescence components were significantly affected by the freeze-thaw intensity. Results from the redundancy analysis showed that under the experimental conditions, forest type played a leading role in changing DOM properties. The DOM content and its three fluorescence intensities of WBF soil leachates were higher than those of BKPF. Soil moisture significantly affected the aromaticity of DOM in the forest soil leachates, and the DOM aromaticity of soil leachates from the two forest stands ranked as medium moisture > high moisture > low moisture. With the increases of freeze-thaw intensity, the DOM aromaticity of BKPF soil leachates significantly decreased. Furthermore, the increases of freeze-thaw cycles significantly increased the humification degree of DOM in the forest soil leachates. Therefore, upon different freeze-thaw disturbance, the DOM content and bioavailability of soil leachates with low moisture tended to increase, particularly in the WBF soil leachates, which may result in an increased lea-ching of DOM in temperate forest soils during spring freeze-thaw periods. The results provide a refe-rence for further investigating DOM turnover in temperate forest soils during spring freeze-thaw periods.

Additive tree biomass equations for Betula platyphylla Suk. plantations in Northeast China

A new system of additive tree biomass equations was developed for juvenile white birch plantations based on tree diameter at breast height (DBH) and tree height (HT). Compared with previous equations developed for natural white birch forests, the new system included one more biomass component and provided more accurate predictions. Accurate estimates of tree component and total biomass are necessary for evaluating alternative forest management strategies for biomass feedstock, carbon sequestration, and products. Previous biomass equations developed for white birch trees in natural stands provided substantially biased predictions for white birch plantations. A new system of additive tree biomass equations was developed for juvenile white birch plantations in the northeastern China. With destructive biomass sampling data from 501 trees sampled from white birch provenance and family trails at ages 7, 9, 10, and 13 in three provinces, a system of nonlinear additive tree biomass equations based on DBH and tree height was developed using the nonlinear seemingly unrelated regressions (NSUR) approach. Compared with previously published equations developed for natural white birch forests, the new system provided more accurate predictions of white birch tree component and aboveground and total biomass, especially of branch, foliage, and root biomass. The new system extended the applicability of biomass equations to white birch plantations in the northeastern China.

Effect of carbon and nitrogen addition on nitrous oxide and carbon dioxide fluxes from thawing forest soils

AbstractPacked soil-core incubation experiments were done to study the effects of carbon (glucose, 6.4 g C m−2) and nitrogen (NH4Cl and KNO3, 4.5 g N m−2) addition on nitrous oxide (N2O) and carbon dioxide (CO2) fluxes during thawing of frozen soils under two forest stands (broadleaf and Korean pine mixed forest and white birch forest) with two moisture levels (55 and 80% water-filled pore space). With increasing soil moisture, the magnitude and longevity of the flush N2O flux from forest soils was enhanced during the early period of thawing, which was accompanied by great NO3−-N consumption. Without N addition, the glucose-induced cumulative CO2fluxes ranged from 9.61 to 13.49 g CO2-C m−2, which was larger than the dose of carbon added as glucose. The single addition of glucose increased microbial biomass carbon but slightly affected soil dissolved organic carbon pool. Thus, the extra carbon released upon addition of glucose can result from the decomposition of soil native organic carbon. The glucose-induced N2O and CO2fluxes were both significantly correlated to the glucose-induced total N and dissolved organic carbon pools and influenced singly and interactively by soil moisture and KNO3addition. The interactive effects of glucose and nitrogen inputs on N2O and CO2fluxes from forest soils after frost depended on N sources, soil moisture, and vegetation types.

森林土壤融化期异养呼吸和微生物碳变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 森林土壤融化期异养呼吸和微生物碳变化特征 DOI: 10.5846/stxb201511162320 作者: 作者单位: 中国科学院大气物理研究所,中国科学院大气物理研究所,中国科学院大气物理研究所,长安大学地球科学学院,Faculty of Agriculture, Yamagata University, Tsuruoka, Japan 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（41175133，21228701，41275166，41321064，41575154） Changes in heterotrophic respiration and microbial biomass carbon of forest soils during thaw Author: Affiliation: Institute of Atmospheric Physics, Chinese Academy of Sciences,Institute of Atmospheric Physics, Chinese Academy of Sciences,Institute of Atmospheric Physics, Chinese Academy of Sciences,College of Earth Science and Resources, Chang'an University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用室内土柱培养的方法，研究在不同湿度（55%和80% WFPS，土壤充水孔隙度）和不同氮素供给（NH4Cl和KNO3，4.5 g N/m2）条件下，外源碳添加（葡萄糖，6.4 g C/m2）对温带成熟阔叶红松混交林和次生白桦林土壤融化过程微生物呼吸和微生物碳的激发效应。结果表明：在整个融化培养期间，次生白桦林土壤对照CO2累积排放量显著高于阔叶红松混交林土壤。随着土壤湿度的增加，次生白桦林土壤对照CO2累积排放量和微生物代谢熵（qCO2）显著降低，而阔叶红松混交林土壤两者显著地增加（P < 0.05）。两种林分土壤由葡萄糖（Glu）引起的CO2累积排放量（9.61-13.49 g C/m2）显著大于实验施加的葡萄糖含碳量（6.4 g C/m2），同时由Glu引起的土壤微生物碳增量为3.65-27.18 g C/m2，而施加Glu对土壤DOC含量影响较小。因此，这种由施加Glu引起的额外碳释放可能来源于土壤固有有机碳分解。融化培养结束时，阔叶红松混交林土壤未施氮处理由Glu引起的CO2累积排放量在两种湿度条件下均显著大于次生白桦林土壤（P < 0.001）；随着湿度的增加，两种林分土壤Glu引起的CO2累积排放量显著增大（P < 0.001）。单施KNO3显著地增加两种湿度的次生白桦林土壤Glu引起的CO2累积排放量（P < 0.01）。单施KNO3显著地增加了两种湿度次生白桦林土壤Glu引起的微生物碳（P < 0.001），单施NH4Cl显著地增加低湿度阔叶红松混交林土壤Glu引起的微生物碳（P < 0.001）。结合前期报道的未冻结实验结果，发现冻结过程显著地影响外源Glu对温带森林土壤微生物呼吸和微生物碳的刺激效应（P < 0.05），并且无论冻结与否，温带森林土壤微生物呼吸和微生物碳对外源Glu的响应均与植被类型、土壤湿度、外源氮供给及其形态存在显著的相关性。 Abstract:Packed soil core incubation experiment was made to study the effects of external carbon (C) (glucose, 6.4 g C/m2) addition on microbial respiration and microbial biomass C (MBC) in soils of a mature broadleaf and Korean pine mixed forest (BKPF) and an adjacent white birch forest (WBF) during thaw under different soil moisture levels (55% and 80% water-filled pore space) and nitrogen (N) supply (NH4Cl and KNO3, 4.5 g N/m2). The results showed that, without C and N addition, cumulative CO2 flux from the WBF soil was significantly higher than that from the BKPF soil during the incubation period. With increasing soil moisture, the cumulative CO2 flux and microbial metabolic quotient (qCO2) decreased in the WBF soil but increased in the BKPF soil without C and N addition(P < 0.05). The glucose-induced cumulative CO2 fluxes from the two forest soils ranged from 9.61 to 13.49 g CO2-C/m2, which was greater than the dose of added C in the form of glucose. The glucose-induced MBC in the two forest soils ranged from 3.65 to 27.18 g C/m2, while glucose addition had little impact on soil dissolved organic C pool. Hence, the extra C released upon addition of glucose may result from the decomposition of soil native organic C. Without N addition and under the two soil moisture levels, the glucose-induced cumulative CO2 flux from the BKPF soil was significantly higher than that from the WBF soil during thaw (P < 0.001). With increasing soil moisture, the glucose-induced cumulative CO2 fluxes from the two forest soils were significantly increased (P < 0.001). The addition of KNO3 alone significantly increased the glucose-induced cumulative CO2 flux (P < 0.01) and the glucose-induced MBC (P < 0.001) in the WBF soil under two soil moisture levels (P < 0.001). Addition of NH4Cl alone significantly increased the glucose-induced MBC in the BKPF soil with low moisture level. Based on the results from the previously reported non-freezing experiments and the results of the present study, it can be concluded that freezing treatment significantly affects the stimulating effects of glucose on soil microbial respiration and MBC under temperate forests. Regardless of whether freezing occurred or not, the responses of soil microbial respiration and MBC to the addition of extraneous C as glucose in temperate forests depend on vegetation type, soil moisture, and the amount and type of N added. 参考文献 相似文献 引证文献

Holocene pollen record from Lake Sokoch, interior Kamchatka (Russia), and its paleobotanical and paleoclimatic interpretation

A pollen record, obtained from sediments of Lake Sokoch in mountain interior of the Kamchatka Peninsula, covers the last ca. 9600years (all ages are given in calibrated years BP). Variations in local components, including pollen, spores and non-pollen palynomorphs, and related changes in sedimentation document the lake development from initially seepage and shallow basin to deeper lake during the mid Holocene and then to the hydrologically open system during the late Holocene. The studies of volcanic ashes from the lake sediment core show their complex depositional histories.Lake Sokoch occupies a former proglacial basin between two terminal moraines of the LGM time. The undated basal part of record before ca. 9600year BP, however, does not reflect properly cold conditions. At that time, although shrublands and tundra dominated, stone birch and white birch forests have already settled in surroundings; the presence of alder woodland indicates wet and maritime-like climate. The subsequent forest advance suggesting warmer conditions was interrupted by the ca. 8000–7600year BP spell of cooler climate. The following culmination of warmth is bracketed by the evidence of the first maximal forest extent between ca. 7400 and 5100year BP. During that time, dramatic retreat of alder forest suggests a turn from maritime-like to more continental climate conditions. The cool and wet pulse after ca. 5100year BP was pronounced as forests retreat while shrublands, meadows and bogs extended. An expansion of white birch forest since ca. 3500year BP reflected the onset of drier climate, strengthening continentality and seasonal contrast. The second maximum of forests dominated by both stone and white birches occurred between ca. 2200 and 1700year BP and indicated warming in association with relatively dry and increasingly continental climate. The following period was wetter and cooler, and minor outbreak of alder forest around ca. 1500year BP suggests a short-term return of maritime-like conditions. Since ca. 1300year BP forests retreated and replaced by shrublands, tundra and bogs, pointing to cool and wet climate and likely increased back continentality. A prominent re-advance of stone birch forest shown atop the record, most probably reflects recent warming trend.The reconstructed cool periods correlate well with Holocene glacial advances in neighboring mountain areas and with the tree ring and ice core records from the Central Kamchatka Depression. The Lake Sokoch pollen record, being consistent with the previously obtained regional paleoclimatic data, yet contributes new detailed information, especially for the late Holocene.

Changes of forest fire regime and landscape pattern under different harvesting modes in a boreal forest of Northeast China

Forest management such as timber harvesting shapes fire regimes and landscape patterns, and these patterns often differ significantly from those under natural disturbances. Our objective was to examine the effects of timber harvesting modes on fire regimes and landscape patterns in a boreal forest of Northeast China. We used a spatially explicit landscape model, LANDIS, to simulate the changes of forest landscape in the Huzhong forest region of the Great Khingan Mountains under no-cutting, clear-cutting, gradual-cutting and selective-cutting modes. Results showed that: (1) the fine fuel loadings generally decreased while the coarse fuel loadings increased with the increase of timber harvesting intensity; (2) the potential burn area significantly varied among different cutting modes, but the potential fire frequency had no obvious difference. Moreover, timber harvesting generally increased the potential fire risk; (3) clear-cutting mode significantly decreased the mean patch size and the aggregation of larch forests and increased the mean patch size and the aggregation of white birch forests. Therefore, clear-cutting mode should be abandoned, and selective-cutting mode be recommended for the sustainable forest management in the Great Khingan Mountains.

Effect of intensity and duration of freezing on soil microbial biomass, extractable C and N pools, and N2O and CO2 emissions from forest soils in cold temperate region

Freezing can increase the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) and the release of labile carbon (C) and nitrogen (N) pools into the soil. However, there is limited knowledge about how both emissions respond differently to soil freezing and their relationships to soil properties. We evaluated the effect of intensity and duration of freezing on the emissions of CO2 and N2O, net N mineralization, microbial biomass, and extractable C and N pools in soils from a mature broadleaf and Korean pine mixed forest and an adjacent secondary white birch forest in northeastern China. These soils had different contents of microbial biomass and bulk density. Intact soil cores of 0–5 cm and 5–10 cm depth sampled from the two temperate forest floors were subjected to -8, -18, and -80°C freezing treatments for a short (10 d) and long (145 d) duration, and then respectively incubated at 10°C for 21 d. Soil cores, incubated at 10°C for 21 d without a pretreatment of freezing, served as control. Emissions of N2O and CO2 after thaw varied with forest type, soil depth, and freezing treatment. The difference could be induced by the soil water-filled pore space (WFPS) during incubation and availability of substrates for N2O and CO2 production, which are released by freezing. A maximum N2O emission following thawing of frozen soils was observed at approximately 80% WFPS, whereas CO2 emission from soils after thaw significantly increased with increasing WFPS. The soil dissolved organic C just after freezing treatment and CO2 emission increased with increase of freezing duration, which paralleled with a decrease in soil microbial biomass C. The cumulative net N mineralization and net ammonification after freezing treatment as well as N2O emission were significantly affected by freezing temperature. The N2O emission was negatively correlated to soil pH and bulk density, but positively correlated to soil K2SO4-extractable NO3 --N content and net ammonification. The CO2 emission was positively correlated to the cumulative net N mineralization and net ammonification. From the above results, it can be reasonably concluded that for a wide range of freezing temperature and freezing duration, N2O and CO2 emissions after thaw were associated mainly with the changes in soil net N mineralization and the availability of substrate liberated by freezing as well as other soil properties that influence porosity.

Effect of vegetation type, wetting intensity, and nitrogen supply on external carbon stimulated heterotrophic respiration and microbial biomass carbon in forest soils

By using packed soil-core incubation experiments, we have studied stimulating effects of addition of external carbon (C) (glucose, 6.4 g C m−2) on heterotrophic respiration and microbial biomass C of a mature broadleaf and Korean pine mixed forest (BKPF) and an adjacent white birch forest (WBF) soil under different wetting intensities (55% and 80% WFPS, water-filled pore space) and nitrogen (N) supply (NH4Cl and KNO3, 4.5 g N m−2) conditions. The results showed that for the control, the cumulative carbon dioxide (CO2) flux from WBF soil during the 15-day incubation ranged from 5.44 to 5.82 g CO2-C m−2, which was significantly larger than that from BKPF soil (2.86 to 3.36 g CO2-C m−2). With increasing wetting intensity, the cumulative CO2 flux from the control was decreased for the WBF soil, whereas an increase in the CO2 flux was observed in the BKPF soil (P < 0.05). The addition of NH4Cl or KNO3 alone significantly reduced the cumulative CO2 fluxes by 9.2%–21.6 % from the two soils, especially from WBF soil at low wetting intensity. The addition of glucose alone significantly increased soil heterotrophic respiration, microbial biomass C (MBC), and microbial metabolic quotient. The glucose-induced cumulative CO2 fluxes and soil MBC during the incubation ranged from 8.7 to 11.7 g CO2-C m−2 and from 7.4 to 23.9 g C m−2, which are larger than the dose of added C. Hence, the addition of external carbon can increase the decomposition of soil native organic C. The glucose-induced average and maximum rates of CO2 fluxes during the incubation were significantly influenced by wetting intensity (WI) and vegetation type (VT), and by WI×VT, NH4Cl×VT and WI×VT×NH4Cl (P<0.05). The addition of NH4Cl, instead of KNO3, significantly decreased the glucose-induced MBC of WBF soil (P<0.05), whereas adding NH4Cl and KNO3 both significantly increased the glucose-induced MBC of BKPF soil at high moisture (P<0.05). According to the differences in soil labile C pools, MBC and CO2 fluxes in the presence and absence of glucose, it can be concluded that the stimulating effects of glucose on soil heterotrophic respiration and MBC under temperate forests were dependent on vegetation type, soil moisture, and amount and type of the N added.

Short‐term effect of selection cutting in boreal balsam fir forest on cerambycid and scolytid beetles

AbstractThe ecology and management of boreal forest ecosystems are drawing greater attention worldwide as their importance is being increasingly recognized for carbon sequestration or for harbouring the world's largest remaining intact forests. Selection cuts have been introduced as a more socially acceptable silvicultural method to improve the maintenance of habitat structure and functions as they mimic aspects of boreal forest succession dynamics. Many studies have shown that selection cutting helps maintaining arthropod communities in mature forests, but few have examined the increased risks of damage by bark‐ and wood‐boring insects in boreal forests of eastern North America. We used multidirectional flight‐interception traps to quantify the response of these beetles to 25 and 40% selection cutting in a balsam fir–white birch forest of Québec, Canada. The abundance and species number of both cerambycid and scolytid beetles were 5–6 times larger in selectively cut stands than in controls the year following treatments. Analyses revealed that bark‐ and wood‐boring beetles’ response was mostly associated with increased canopy openness in selectively cut stands (and sun‐exposed locations within them) and residual tree injuries caused by harvesting operations. These conditions attracted beetles such as Trypodendron lineatum (Scolytinae) and Rhagium inquisitor (Cerambycidae), two species known for their ability to attack weakened, dying and dead hosts. Most species were more abundant in selection cuts, except for Evodinus m. monticola (Cerambycidae) whose abundance was strongly reduced after treatment. Some beetles can have detrimental effects on residual trees and thus could reduce timber value, but most species found in treated stands do not represent a high risk for healthy trees. Thus, selection cuts do not seem favourable to the establishment of tree‐killing beetles. However, as they were found more active/abundant after selection cutting, it would be wise to further study their population dynamics over mid‐ and long‐term periods, along with the ecological and economic implications associated with this silvicultural treatment.

Effect of carbon and nitrogen addition on nitrous oxide flux from temperate forest soils under different wetting intensity conditions

Packed soil-core incubation experiments were done to study the effects of carbon(glucose, 6.4 g C m-2) and nitrogen(NH4Cl and KNO3, 4.5 g N m-2) addition on nitrous oxide(N2O) fluxes from a mature broadleaf and Korean pine mixed forest(BKPF) soil and adjacent white birch forest(WBF) soil under two wetting intensities(55% and 80% WFPS). The results showed that with the except of the WBF soil added with NH4Cl alone under high wetting intensity, increased wetting intensity and addition of carbon and nitrogen could significantly enhance N2O fluxes from the two forest soils, singly and interactively(P0.05). Glucose-induced N2O fluxes from BKPF and WBF soils were 0.53–2.67 and 4.70–29.32 mg N2O-N m-2, respectively, especially under high wetting conditions and from the WBF soil, which coincided with a significant decrease in soil inorganic N concentration, especially for the water-extractable NO3-in the WBF soil under high wetting conditions. These illustrated that stimulating effect of glucose addition on the soil N2O fluxes increased with increasing wetting intensity, particularly for the WBF soil. Under low wetting conditions, stimulating effect of glucose addition on the N2O fluxes was partly inhibited by extraneous N addition during early stage of the incubation, and then it altered with types of forest vegetation and the N pools added. However, under high wetting conditions, stimulating effect of glucose was enhanced by N addition, particularly by KNO3 addition(P0.05). Additionally, glucose addition could significantly increase microbial biomass carbon and the ratios of microbial biomass carbon to nitrogen in the both forest soils, thus suggesting the change in microorganism communities. Nitrogen addition of two types increased concentrations of water- and K2SO4-extractable DON in both soils, especially in BKPF soil, and there were no differences between the two types of N added. Stepwise regression analysis showed that 61% of the variability in the N2O flux from WBF soil could be attributed to concentrations of WFPS, water-extractable NH4+-N and DON and the ratio of microbial biomass carbon to nitrogen and influenced by the water-extractable DON mostly. Meanwhile, 50% of the variability in the N2O flux from BKPF soil could be explained by the concentration of WFPS, the water-extractable NH4+-N and microbial biomass carbon and influenced by WFPS mostly. From the results, it can be concluded that wetting-induced N2O fluxes from temperate forest soils could be related to wetting intensity, microbial biomass and available N pools in soils.

Autumn at a White Birch Forest

The first time I saw birch trees was many years ago, when I was on a postdoctoral fellowship in the United Kingdom and attended an IFCC Congress in Denmark. They were isolated silver birch planted as ornamental trees in gardens or parks. The yellow leaves quivering in the autumn wind and the unusual silvery white trunks with dark markings made me stop for a …