Estimation of fungal biomass in forest litter and soil

The contents of fungal biomass markers were analysed in the fruit bodies of dominant basidiomycetes from an ectomycorrhiza-dominated coniferous forest, and used to estimate the fungal biomass content in the litter and soil. The content of ergosterol (3.8 ± 2.0 mg g^?1 dry fungal biomass) and the phospholipid fatty acid 18:2ω6,9 (11.6 ± 4.3 mg g^?1) showed less variation than the internal transcribed spacer (ITS) copy numbers (375 ± 294 × 10⁹ copies g^?1). A high level of variation in the ITS copy numbers (per ng DNA) was also found among fungal taxa. The content of fungal biomass in the litter and soil, calculated using the mean contents, varied between 0.66 and 6.24 mg g^?1 fungal biomass in the litter, and 0.22 and 0.68 mg g^?1 in the soil. The ratio of fungal biomass in the litter to that in the soil varied greatly among the markers. The estimates of fungal biomass obtained with different biomarkers are not exactly comparable, and caution should be used when analysing taxon abundance using PCR amplification of fungal rDNA.     

Variation in soil seed bank species composition of a dry coniferous forest: spatial scale and sampling considerations

In order to assess the effects of disturbance on soil seed bank spatial structure, variation in seed bank species composition was analyzed at two spatial scales in mature (undisturbed) and recently disturbed stands of Interior Douglas-fir forest in south-central British Columbia. Coarse-scale analysis among stands 10–100 km apart using Multi-Response Permutation Procedures showed that individual mature stands were mainly characterized by unique seed bank species compositions. Disturbance had an homogenizing effect on seed bank species composition at the coarse scale––there was less variability among stands following disturbance by both low and high severity fires, and by non-salvage logging. In contrast, finer scale analysis among sampling units c. 10 m apart showed that heterogeneity in seed bank species composition was greater on severely burned and logged sites, commensurate with greater levels of soil disturbance, than on lightly burned and undisturbed sites. Despite the high intensity of seed bank sampling (sixty 25 cm² soil samples from each of 16 sites), species-area curves leveled off only when infrequent species were removed from the dataset. The number of seed bank samples required to account for the common species ranged from 84 on severely burned sites, to 196 on undisturbed sites; more than the 240 samples collected per disturbance class in this study would have been required to account for the remaining infrequent species. Overall, this study highlights the importance of sampling intensively within multiple stands to capture the variation in species composition inherent to these dry coniferous forest soil seed banks.     

Plant species richness and productivity determine the diversity of soil fungal guilds in temperate coniferous forest and bog habitats

Fungi have important roles as decomposers, mycorrhizal root symbionts and pathogens in forest ecosystems, but there is limited information about their diversity and composition at the landscape scale. This work aimed to disentangle the factors underlying fungal richness and composition along the landscape‐scale moisture, organic matter and productivity gradients. Using high‐throughput sequencing, we identified soil fungi from 54 low‐productivity Pinus sylvestris‐dominated plots across three study areas in Estonia and determined the main predictors of fungal richness based on edaphic, floristic and spatial variables. Fungal richness displayed unimodal relationship with organic matter and deduced soil moisture. Plant richness and productivity constituted the key predictors for taxonomic richness of functional guilds. Composition of fungi and the main ectomycorrhizal fungal lineages and hyphal exploration types was segregated by moisture availability and soil nitrogen. We conclude that plant productivity and diversity determine the richness and proportion of most functional groups of soil fungi in low‐productive pine forests on a landscape scale. Adjacent stands of pine forest may differ greatly in the dominance of functional guilds that have marked effects on soil carbon and nitrogen cycling in these forest ecosystems.     

Impact of local forest composition on soil fungal communities in a mixed boreal forest

Plant and Soil - While fungi are key drivers of the carbon cycle and obligate symbionts of trees, the link between plant-fungal interactions and landscape vegetation changes has been largely...     

Seasonal fluctuations in soil phenolics of a coniferous forest: effects on seed germination of different coniferous species

This study examined seasonal variations in the content of water-soluble phenolics extracted from litter and Ah horizon of forest soil under Pinus laricio Poiret trees. After having identified and quantified different phenolics, the effects of seasonal phenolic extracts, single phenolic acids and synthetic phenol mixtures on seed germination of Pinus laricio Poiret, Pinus pinaster Aiton and Pinus halepensis Mill. were evaluated, and the activity of phenolics on the main enzymes involved in the glyoxylate cycle was tested. The results indicated a seasonal variation of phenol content in soil, with largest concentrations of water-soluble phenolic acids in autumn and smallest concentrations in summer. Addition of phenol extracts to germination medium reduced seed germination showing phytotoxic effects which differed, depending on the species and the fractions tested. Phenols extracted from litter and Ah horizon in autumn and winter, vanillic acid, and synthetic mixtures reproducing phenols extracted from soil in winter inhibited seed germination of Pinus laricio, pinaster and halepensis more than other treatments. A greater inhibitory effect was observed on seed germination of Pinus pinaster and halepensis compared to Pinus laricio. The phenols also had the greatest inhibitory effect on glyoxylic enzyme activities. Section Editor: H. Lambers     

长白山暗针叶林苔藓植物生物量的研究

在长白山北坡暗针叶林对地面和树附生苔藓植物的生物量进行了测定.地面生苔藓采取样带调查取样法测定,树附生苔藓应用McCune方法对树干和树枝的附生苔藓生物量都做了细致的测定.结果表明,长白山暗针叶林中的苔藓植物分布很不均匀,随海拔变化差异很大,海拔1100m最低,仅为543kg·hm^-2;海拔1250m最高,达5097kg·hm^-2.苔藓植物生物量的变化对生境有很好的指示作用,特别是塔藓和拟垂枝藓的生物量随海拔的变化与森林系统的群落学特点有一定的相关性:在海拔1100～1700m,塔藓的生物量与臭冷杉的重要值变化趋势相近,随海拔升高而减少;拟垂枝藓的生物量与鱼鳞云杉重要值的变化趋势相似,随海拔升高而增加.此外,生物量随海拔的变化表明了不同苔藓植物对环境条件要求的差异,拟垂枝藓比塔藓水分条件要求更高.因此,生物量的研究在植物生理上也有一定的指示作用.     

长白山暗针叶林苔藓植物生物量的研究

在长白山北坡暗针叶林对地面和树附生苔藓植物的生物量进行了测定．地面生苔藓采取样带调查取样法测定,树附生苔藓应用McCune方法对树干和树枝的附生苔藓生物量都做了细致的测定．结果表明,长白山暗针叶林中的苔藓植物分布很不均匀,随海拔变化差异很大,海拔1100m最低,仅为543kg·hm^-2;海拔1250m最高,达5097kg·hm^-2．苔藓植物生物量的变化对生境有很好的指示作用,特别是塔藓和拟垂枝藓的生物量随海拔的变化与森林系统的群落学特点有一定的相关性：在海拔1100～1700m,塔藓的生物量与臭冷杉的重要值变化趋势相近,随海拔升高而减少;拟垂枝藓的生物量与鱼鳞云杉重要值的变化趋势相似,随海拔升高而增加．此外,生物量随海拔的变化表明了不同苔藓植物对环境条件要求的差异,拟垂枝藓比塔藓水分条件要求更高．因此,生物量的研究在植物生理上也有一定的指示作用．     

模拟氮沉降下南方针叶林红壤的养分淋溶和酸化

以中国科学院红壤生态实验站林草生态试验区针叶林红壤为研究对象,在恒温(20 ℃)条件下,通过大土柱（直径10 cm、高60 cm）,8个月间隙性淋溶试验模拟研究了不同氮输入量（0、7.8、26和52 mg N/月/柱）对针叶林红壤NO₃^-、NH₄⁺、H⁺和土壤盐基离子(Ca²⁺、Mg²⁺、K⁺、Na⁺⁾淋溶以及土壤酸化的影响.结果表明,土壤交换态盐基总量、Ca²⁺和Mg²⁺淋溶量随氮输入量的增加而增加,土壤交换态Na⁺和K⁺则无明显影响.4种N输入处理的土壤交换态盐基总量净淋溶（淋溶出的盐基与淋洗液累计输入的盐基之差）分别占土壤交换性盐基总量的13.9%、18.6%、31.8% 和57.9％,土壤交换态Ca²⁺净淋溶分别占土壤交换性Ca²⁺总量的19.6%、25.8%、45.3%和84.8%,土壤交换态Mg²⁺净淋溶分别占土壤交换性Mg²⁺总量的4.4%、6.1%、10.9%和17.1%.随氮输入量增加,表层土壤pH值逐渐下降,4种N输入处理的表层土壤pH（KCl）分别为3.85、3.84、3.80和3.75;随氮输入量增加,淋溶液中无机氮、NO₃^-和H⁺逐渐增加.氮沉降可促进针叶林红壤的有机氮矿化,加速养分淋失和土壤酸化.     

模拟氮沉降增加对寒温带针叶林土壤 CO2排放的初期影响

研究大气氮沉降增加情景下北方森林土壤CO2排放通量及其相关控制因子至关重要。在大兴安岭寒温带针叶林区建立了大气氮沉降模拟控制试验,利用静态箱-气相色谱法测定土壤CO2排放通量,同时测定土壤温度、水分、无机氮和可溶性碳含量等相关变量,分析寒温带针叶林土壤CO2排放特征及其主要驱动因子。结果表明:氮素输入没有显著改变森林土壤含水量,但降低了有机层土壤溶解性无机碳(DIC)含量,并增加有机层和矿质层土壤溶解性有机碳(DOC)含量。增氮短期内不影响土壤NH+4-N含量,但促进了土壤NO-3-N的累积。增氮倾向于增加北方森林土壤CO2排放。土壤CO2通量主要受土壤温度驱动,其次为土壤水分和DIC含量。虽然土壤温度整体上控制着土壤CO2通量的季节变化格局,但在生长旺季土壤含水量对其影响更为明显。在分析增氮对土壤CO2通量的净效应时,除了土壤温度和水分外,还要考虑土壤有效碳、氮动态的影响。     

Sulfur speciation and distribution in soils and aboveground biomass of a boreal coniferous forest

Major sulfur pools are quantified in soils and aboveground biomass of a coniferous boreal forest. Total ecosystem S averages 1395 kg·ha⁻¹ of which 98% is found in the soil, with 89% being in the mineral horizons. Organic S dominates in soil, tree parts (trunks, branches + foliage, roots) and litterfall, ranging from 77 to 99% of total S concentration. Carbon-bonded S, ester sulfate and SO₄-S in soil profiles range respectively from 51–68%, 29–37% and 1–14% of total S concentrations and account respectively for 57, 33 and 10% of total S on an areal basis. Adsorbed SO₄ accounts for 82% of total SO₄, and can be predicted from Al bound to organic matter, amorphous Al and pH (r^{2 = 0.81}). There is a strong relationship between % carbon and carbon-bonded S in 4 of the 5 soil horizons studied which represent over 95% of the total soil organic matter, whereas ester sulfate is related to % carbon in 3 soil horizons representing only 37% of the soil organic matter. An analysis of atmospheric S loading and S data for 10 forested sites in Europe and North America suggests that the size of the organic S pool in forested systems is independent of atmospheric loading.     

喀斯特森林常见树种倒木分解对土壤真菌群落组成及分布规律的影响

倒木是森林生态系统的重要组分,其分解调控着土壤的养分循环,同时也影响着土壤微生物群落结构。但目前鲜见关于倒木分解对土壤微生物群落影响方面的报道。选取贵州茂兰喀斯特常绿落叶阔叶混交林中处于轻、中和重度腐烂等级的狭叶润楠（Machilus rehderi）、枫香（Liquidambar formosana）、青冈栎（Cyclobalanopsis glauca）和圆果化香（Platycarya longipes）4种常见树种倒木为研究对象,以距倒木外围的3个不同水平距离（10cm、30cm和50cm）的土壤样品为实验材料,分析倒木树种、腐烂等级和距离对土壤真菌种类及多样性的影响。结果表明：1）喀斯特森林4种树种倒木所影响土壤真菌群落在门级分类上主要为子囊菌门、担子菌门和毛霉门,优势属有Mortierella spp.、Phlebia spp.、Pluteus spp.和Chaetomium spp.等;2）倒木的树种对土壤真菌群落相对丰度的影响有差异,圆果化香倒木下的土壤真菌丰富度Chao1指数显著高于青冈栎;3）随腐烂程度加深,4种树种倒木下的土壤真菌群落多样性呈显著增加趋势;4）土壤真菌群落丰度随着距倒木距离的增大（10-50cm）变化明显,如狭叶润楠影响的Pluteus spp.、Mortierella spp.和Ganoderma spp.,枫香的Chaetomium spp.,圆果化香的Mortierella spp.和青冈栎的Phlebia spp.和Oliveonia spp.等。本研究量化了喀斯特森林倒木所影响的土壤真菌群落组成及分布规律,在一定程度上为倒木分解与土壤微生物群落之间的作用机制的深入探索提供了科学依据。     

The effects of ammonium sulphate deposition and root sinks on soil solution chemistry in coniferous forest soils

The effects of enhanced (NH_{4 2}SO₄deposition on soil solution cation and anion concentrations and annualionic fluxes were followed using a standardised experimental protocolin six European coniferous forests with contrasting soil types, pollutioninputs and climate. Native soil cores containing a ceramic suction cupwere installed in the field, roofed and watered every two weeks withlocal throughfall or local throughfall with added(NH₄)₂SO₄ at 75 kgNH₄ ⁺-N ha^-1 a^-1. Livingroot systems were established in half of the lysimeters.Untreated throughfall NH₄ ⁺-N deposition at thesites ranged from 3.7 to 29 kg ha^-1 a^-1Soil leachates were collected at two weekly intervalsover 12 months and analysed for volume, andconcentrations of major anions and cations. Increasesin soil solution NO₃ ^- concentrations inresponse to N additions were observed after 4–9months at three sites, whilst one sandy soil with highC:N ratio failed to nitrify under any of thetreatments. Changes in NO₃ ^- concentrationsin soil solution controlled soil solution cationconcentrations in the five nitrifying soils, withAl³⁺ being the dominant cation in the more acidsoils with low base saturation. The acidification responses ofthe soils to the (NH_{4 2}SO₄additions were primarily related to the ability of thesoils to nitrify the added NH₄ ⁺. pH and soiltexture seemed important in controllingNH₄ ⁺ leaching in response to the treatments,with two less acidic, clay/clay loam sites showingalmost total retention of added NH₄ ⁺, whilstnearly 75% of the added N was leached asNH₄ ⁺ at the acid sandy soils. The presenceof living roots significantly reduced soil solutionNO₃ ^- and associated cation concentrations attwo of the six sites. The very different responses of the sixsoils to increased (NH₄)₂SO₄deposition emphasise that the establishment of N critical loadsfor forest soils need to allow for differences in N storagecapacity and nitrification potential.     

Above-ground biomass estimation using airborne discrete-return and full-waveform LiDAR data in a coniferous forest

The estimation of forest aboveground biomass (AGB) is critical for quantifying carbon stocks and essential for evaluating global carbon cycle. Many previous studies have estimated forest AGB using airborne discrete-return Light Detection and Ranging (LiDAR) data, while fewer studies predicted forest AGB using airborne full-waveform LiDAR data. The objective of this work was to evaluate the utility of airborne discrete-return and full-waveform LiDAR data in estimating forest AGB. To fulfill the objective, airborne discrete-return LiDAR-derived metrics (DR-metrics), full-waveform LiDAR-derived metrics (FW-metrics) and structure parameters (combining height metrics and canopy cover) were used to estimate forest AGB. Additionally, the combined use of DR- and FW-metrics through a nonlinear way was also evaluated for AGB estimation in a coniferous forest in Dayekou, Gansu province of China. Results indicated that both height metrics derived from discrete-return and full-waveform LiDAR data were stronger predictors of forest AGB compared with other LiDAR-derived metrics. Canopy cover derived from discrete-return LiDAR data was not sensitive to forest AGB, while canopy cover estimated by full-waveform LiDAR data (CC_WF) showed moderate correlation with forest AGB. Structure parameters derived from full-waveform LiDAR data, such as H75_FW * CC_FW, were closely related to forest AGB. In contrast, structure parameters derived from discrete-return LiDAR data were not suitable for estimating forest AGB due to the less sensitivity of canopy cover CC_DR2 to forest AGB. This research also concluded that the synergistic use of DR- and FW-metrics can provide better AGB estimates in coniferous forest.     

Late Quaternary climate change explains soil fungal community composition rather than fungal richness in forest ecosystems

The dramatic climate fluctuations of the late Quaternary have influenced the diversity and composition of macroorganism communities, but how they structure belowground microbial communities is less well known. Fungi constitute an important component of soil microorganism communities. They play an important role in biodiversity maintenance, community assembly, and ecosystem functioning, and differ from many macroorganisms in many traits. Here, we examined soil fungal communities in Chinese temperate, subtropical, and tropic forests using Illumina MiSeq sequencing of the fungal ITS1 region. The relative effect of late Quaternary climate change and contemporary environment (plant, soil, current climate, and geographic distance) on the soil fungal community was analyzed. The richness of the total fungal community, along with saprotrophic, ectomycorrhizal (EM), and pathogenic fungal communities, was influenced primarily by the contemporary environment (plant and/or soil) but not by late Quaternary climate change. Late Quaternary climate change acted in concert with the contemporary environment to shape total, saprotrophic, EM, and pathogenic fungal community compositions and with a stronger effect in temperate forest than in tropic–subtropical forest ecosystems. Some contemporary environmental factors influencing total, saprotrophic, EM, and pathogenic fungal communities in temperate and tropic–subtropical forests were different. We demonstrate that late Quaternary climate change can help to explain current soil fungal community composition and argue that climatic legacies can help to predict soil fungal responses to climate change.     

Monitoring of bacterial community in a coniferous forest soil after a wildfire

Changes in the soil bacterial community of a coniferous forest were analyzed to assess microbial responses to wildfire. Soil samples were collected from three different depths in lightly and severely burned areas, as well as a nearby unburned control area. Direct bacterial counts ranged from 3.3-22.6 x 10(8) cells/(g.soil). In surface soil, direct bacterial counts of unburned soil exhibited a great degree of fluctuation. Those in lightly burned soil changed less, but no significant variation was observed in the severely burned soil. The fluctuations of direct bacterial count were less in the middle and deep soil layers. The structure of the bacterial community was analyzed via the fluorescent in situ hybridization method. The number of bacteria detected with the eubacteria-targeted probe out of the direct bacterial count varied from 30.3 to 84.7%, and these ratios were generally higher in the burned soils than in the unburned control soils. In the surface unburned soil, the ratios of alpha-, beta- and gamma-proteobacteria, Cytophaga-Flavobacterium group, and other eubacteria groups to total eubacteria were 9.9, 10.6, 15.5, 9.0, and 55.0%, respectively, and these ratios were relatively stable. The ratios of alpha-, beta- and gamma-proteobacteria, and Cytophaga-Flavobacterium group to total eubacteria increased immediately after the wildfire, and the other eubacterial proportions decreased in the surface and middle layer soils. By way of contrast, the composition of the 5 groups of eubacteria in the subsurface soil exhibited no significant fluctuations during the entire period. The total bacterial population and bacterial community structure disturbed by wildfire soon began to recover, and original levels seemed to be restored 3 months after the wildfire.     

温带针阔混交林生物量稳定性影响机制

森林生态系统通过响应环境波动和干扰而产生时间变化,对其稳定性机制的研究有利于生态系统服务。温带针阔混交林是全球森林生态系统的重要组成部分,该研究致力于探索超产效应、林分结构、物种异步性及优势物种稳定性对温带天然针阔混交林群落稳定性的影响,以明确主要影响机制。该研究分别设定物种丰富度、胸径变异系数、物种异步性和优势物种稳定性为解释变量,群落生物量稳定性、生物量平均值和生物量标准差为响应变量,构建3个结构方程模型,比较各变量间直接与间接效应的相对大小。主要结果为:(1)结构方程模型提供了良好的拟合效果,并占群落生物量稳定性变化的40.6%;(2)物种丰富度与生物量平均值、生物量标准差均呈显著负相关关系,路径系数分别为–0.103和–0.061;(3)胸径变异系数与群落生物量稳定性及生物量平均值均呈显著负相关关系,路径系数分别为–0.123和–0.097;(4)物种异步性与群落生物量稳定性、生物量平均值、生物量标准差均呈显著正相关关系,路径系数分别为0.055、0.085和0.055;(5)优势物种稳定性与群落生物量稳定性和生物量平均值呈显著正相关关系,路径系数分别为0.623和0.085,...     

Soil-wood interactions: Influence of decaying coniferous and broadleaf logs on composition of soil fungal communities

Wood-inhabiting fungi may affect soil fungal communities directly underneath decaying wood via their exploratory hyphae. In addition, differences in wood leachates between decaying tree species may influence soil fungal communities. We determined the composition of fungi in 4-yr old decaying logs of Larix kaempferi and Quercus rubra as well as in soil directly underneath and next to logs. Fungal community composition in soil covered by logs was different from that in wood and uncovered soil and was clearly influenced by the tree species. Soil fungal species richness under logs was lower than in uncovered soil but higher than in decaying wood. The amount of exploratory hyphae of log-inhabiting fungi was only high close to decaying logs. In conclusion, there is a small but significant effect of decaying coniferous and broadleaf logs on soil fungal communities directly underneath logs, likely affected by differences in wood chemistry and fungal preference between tree species.