Recovery of mycorrhizas of a fungus, <Emphasis Type="Italic">Cenococcum geophilum</Emphasis>, after urea treatment in warm temperate forests in Japan

We studied recovery of the ectomycorrhizal species Cenococcum geophilum (Cg) after urea treatment in two types of vegetation. The recovery was as quick as 6 months after the treatment and overlapped the fruiting period of ectomycorrhizal ammonia fungi. Ectomycorrhizas investigated as Cg belonged to a single species irrespective of treatment and vegetation type. Cg ectomycorrhizas were significantly more abundant in density in nontreated soil than in treated soil. Between vegetation types, Cg ectomycorrhizas were significantly more in density in broad-leaved deciduous forest than in broad-leaved evergreen forest. Moreover, Cg was dominant in the nontreated soils of the former type of forest.     

Early colonization of red alder and Douglas fir by ectomycorrhizal fungi and Frankia in soils from the Oregon coast range

The potential for mycorrhizal formation and Frankia nodulation were studied in soils from six sites in the Pacific Northwest. The sites included young and old alder stands, a 1-year-old conifer clear-cut, a young conifer plantation, and rotation-aged and old-growth conifer stands. A bioassay procedure was used with both red alder and Douglas fir seedlings as hosts. After 6 weeks growth, seedlings of both hosts were harvested every 3 weeks for 21 weeks and numbers of nodules and ectomycorrhizal types estimated. Nodules formed on red alder and ectomycorrhizae formed on both alder and Douglas fir in soil from all sites. Nodulation potential was highest in soil from the alder stands and the conifer plantation. Seven morphologically distinct ectomycorrhizal types were recovered on Douglas fir and five on alder. Only Thelephora terrestris, a broad-host-range mycobiont, formed mycorrhizae on both hosts. New ectomycorrhizal types formed on both hosts throughout the bioassay. Ectomycorrhizal colonization of alder was greatest in the alder and clear-cut soils. Low ectomycorrhizal colonization on alder was found in soils from sites where conifers were actively growing. Ectomycorrhizal colonization of Douglas fir was highest in the young alder and conifer plantation soils and was low in the rotation-aged conifer soil. The highest diversity of ectomycorrhizal types was found on alder in the conifer clear-cut soil and on Douglas fir in the rotation-aged conifer soil. Effects of host specificity, nodulation and mycorrhiza-forming potential and nodule-mycorrhiza interactions on seedling establishment are discussed in relation to seral stage dynamics and attributes of pioneer ectomycorrhizal fungal species.     

Soil transfers from valley oak (Quercus lobata Nee) stands increase ectomycorrhizal diversity and alter root and shoot growth on valley oak seedlings

 Soils from valley oak (Quercus lobata Nee) riparian areas of the Cosumnes River Nature Conservancy Preserve near Sacramento, California were added to growth medium of valley oak seedlings grown in a greenhouse or in agricultural fields at Cosumnes which probably once supported valley oak trees and are now replanted with native riparian vegetation or allowed to revegetate naturally. Agricultural field soil from the Cosumnes River Preserve was presumed to be low or lacking in ectomycorrhizal inoculum. The study was designed to (1) determine whether valley oak stand soil transfer could cause mycorrhizal infection on valley oak seedlings in an agricultural field and in a greenhouse, (2) describe ectomycorrhizal morphological types formed on valley oak seedlings, and (3) determine whether seedling growth is enhanced more by transfer of natural valley oak stand soil than agricultural field soil. In the field study, transfer of forest soil increased average ectomycorrhizal diversity (2.4 types) more than transfer of agricultural field soil (1.2 types). Valley oak seedlings were responsive to ectomycorrhizal infection in the field study. With increase in mycorrhizal infection there was an increase in shoot growth at the expense of root growth. In the greenhouse study, both percent mycorrhizal infection and mycorrhizal diversity were increased more by transfer of oak forest and woodland soils than agricultural field soil. Eight morphotypes occurred on seedlings in forest and woodland soils but only three morphotypes in agricultural soil. This result strongly suggests that the agricultural field also harbors ectomycorrhizal propagules but forest and woodland soils support a more abundant and diverse ectomycorrhizal flora. Accepted: 17 August 1997     

中国东部森林样带典型森林水源涵养功能

通过对我国东部森林样带四个森林生态系统定位研究站（长白山站、北京站、会同站和鼎湖山站）的九种森林类型水源涵养监测数据的分析,研究了水热梯度下不同森林生态系统水源涵养功能。结果表明：在生长季的5-10月份,各森林类型的水源涵养特性表现出较大差异。林冠截留率的大小依次为：阔叶红松林＞杉木林＞常绿阔叶林＞针阔混交林＞季风常绿阔叶林＞落叶阔叶混交林＞马尾松林＞落叶松林＞油松林,最高的长白山站阔叶红松林的截留率是最低的北京站油松林的2.2倍。森林降雨截留量与林外降雨量呈显著的正相关,林冠截留率与降雨量呈显著负相关。枯落物最大持水深（5-10月份）以北京站落叶阔叶林最大,为6.0mm;鼎湖山站的季风常绿阔叶林最小,为1.0mm。0-60cm土层蓄水量最大的是会同站的人工杉木林,为247mm;最小的是北京站的落叶松林,仅为45.5mm;林分总持水量依次为：杉木林＞阔叶红松林＞常绿阔叶林＞针阔混交林＞季风常绿阔叶林＞落叶阔叶混交林＞马尾松林＞落叶松林＞油松林。各林分总持水量主要集中在土壤层,占总比例的90%以上。     

冻融交替对长白山不同林型土壤两种温室气体排放的影响

以长白山5种林型土壤(硬阔叶林、红松阔叶林、次生白桦林、长白松林和蒙古栎林)为对象,利用原位培养连续取样法研究了冻融过程中5种林型土壤CO₂和N₂O排放特征及相关机理。结果表明:冻融期5种林型土壤是CO₂和N₂O的源。次生白桦林和红松阔叶林土壤CO₂和N₂O的平均通量显著高于其他3种林型。除硬阔叶林外,各林型土壤CO₂通量与土壤含水量间存在显著负相关,但不同林型的土壤CO₂排放对水分敏感性差异较大;除硬阔叶林外,各林型土壤N₂O通量与土壤含水量间存在显著正相关,但水分敏感性因林型而异。5种林型土壤CO₂和N₂O排放通量均与土壤表层温度呈二次函数关系。     

Ectomycorrhizal and arbuscular mycorrhizal colonization of two species of floodplain willows

To understand the relationships between the distribution of Chosenia arbutifolia and Salix sachalinensis and their mycorrhizal colonization, changes in the quality and types of ectomycorrhizas and arbuscular mycorrhizas of the seedlings of two species were studied at five different sites with different soil conditions in the floodplain of the Satsunai River, Hokkaido. High ectomycorrhizal and low arbuscular mycorrhizal colonization were found in roots of both plants. Ectomycorrhizal colonization of S. sachalinensis in wet sandy or muddy soil conditions was at the same level as that in dry gravelly sites. In contrast, ectomycorrhizal colonization of C. arbutifolia seedlings was lower from wet sandy sites than that from dry gravelly sites. In all study sites, the same three morphological types of ectomycorrhizas were dominant.     

Belowground ectomycorrhizal communities in three Norway spruce stands with different degrees of decline in the Czech Republic

We investigated the ectomycorrhizal communities on the roots of adult trees and seedlings associated with three Norway spruce stands in the Czech Republic using morphological and molecular tools. The stands had different degrees of forest decline due to air pollution. The aims of the study were to obtain information about the belowground ectomycorrhizal community in a heavily damaged spruce forest and to assess whether missing ectomycorrhizal fungal partners could be one of the reasons for the observed lack of regeneration. The ectomycorrhizal species richness on the roots of adult trees was significantly lower in the heavily damaged site Mumlavska hora than in the other two, but less drastically so than that found in a fruitbody survey. The roots of adult trees and seedlings were fully mycorrhizal at this site although they were less species-rich. The most abundant ectomycorrhizal species on the root system of adult trees in all three forest stands was Tylospora fibrillosa, a member of the athelioid clade. It made up over 60% of root tips in Mumlavska hora and its proportion was at least twice that in the other two sites. This species was also an efficient colonizer of roots from seedlings, in particular, in the most damaged site. The different soil properties in this site may have caused the observed differences in the ectomycorrhizal species richness and composition. For example, cation exchange capacity and soil base saturation were lower and the soil more often saturated. However, the number of living trees and their defoliation status may well directly impact the ectomycorrhizal species composition by presumably affecting the amount of carbon delivered to the symbiotic fungal partners. Athelioids and thelephoroids are an important component of the belowground ectomycorrhizal community in most temperate and boreal forests, but the role they play might even be more crucial in stressed forest ecosystems. Based on our results, we suggest that factors other than missing ectomycorrhizal inoculum constrain natural regeneration in the heavily damaged site Mumlavska hora.     

Mycorrhizas and C and N transformations in the rhizospheres of Pinus sylvestris,Picea abies and Betula pendula seedlings

Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and silver birch (Betula pendula L.) seedlings were grown in a greenhouse for four months in three different soils. The soils were from a field afforestation site on former agricultural land: soil from a pine site, soil from a spruce site and soil from a birch site. Pots without seedlings were included. The aim was to discover, independent of the effects of the different quality of aboveground litter and microclimate under the tree species, whether the roots change the microbial activities and chemical characteristics of the soil, whether the changes are dependent on the tree species, and whether the changes vary in different soils. Pine, spruce and birch had, on average, five, one and six meters of roots, respectively. Birch had by far the highest number of short root tips, on average 11 450 per seedling, compared to 1900 and 450 in pine and spruce seedlings, respectively. The majority of the short roots of pine and spruce were brown sheathed mycorrhizas, and those of birch were mycorrhizas in an early stage of development. The seedlings caused no major changes in either the soil pH or the concentrations of nutrients in the soils, but did affect the microbial characteristics of the soils. The effect of the tree species did not differ in different soils. Microbial biomass C and N, C mineralization rate and the concentration of ergosterol were all higher under birch and pine than under spruce and in plantless soils. Nitrate concentrations were lowest under pine and birch, but rates of net N mineralization, nitrification and denitrification did not differ under different seedlings. The stimulative effect of pine and especially birch on soil microbes was possibly due to them having more roots and releasing more root exudates to soil. There were, however, indications that not only the length/mass of roots determined the changes in microbial activities, but also differences in root activities per unit of root or in the quality of root exudates.     

普洱市周边地区4种土地利用类型土壤种子库特征

通过对云南普洱市周边地区次生季风常绿阔叶林、针阔混交林、人工更新形成的针叶林及茶园等4种土地利用类型的野外调查及土壤种子库的萌发实验,探讨其土壤种子库的密度大小、物种丰富度和组成及与地上植被的关系。结果表明:干扰强度与频度不同导致土地利用类型之间土壤种子库密度与物种丰富度存在较大差异,土壤种子库密度大小顺序为:针叶林(248.67±116.86)粒·m-2>针阔混交林(186.00±43.27)粒·m-2>次生季风常绿阔叶林(107.33±16.48)粒·m-2>茶园(51.67±10.17)粒·m-2;茶园土壤种子库物种丰富度要显著低于其他类型。4种土地利用类型土壤种子库生活型组成差异极显著,主要以草本植物组成,以菊科与禾本科占优势;针阔混交林的草本植物种子密度最多,非森林的原生物种是草本植物的主要组成;针叶林外来物种的种子密度要显著高于其他类型,紫茎泽兰(Eupatorium adenophorum)是其主要组成。土壤种子库与地上植被的相似性系数较低,其大小顺序为:次生季风常绿阔叶林(0.175)<针阔混交林(0.176)<针叶林(0.215)。     

Quercus rubra-associated ectomycorrhizal fungal communities of disturbed urban sites and mature forests

The presence and quality of the belowground mycorrhizal fungal community could greatly influence plant community structure and host species response. This study tests whether mycorrhizal fungal communities in areas highly impacted by anthropogenic disturbance and urbanization are less species rich or exhibit lower host root colonization rates when compared to those of less disturbed systems. Using a soil bioassay, we sampled the ectomycorrhizal fungal (EMF) communities associating with Quercus rubra (northern red oak) seedlings in soil collected from seven sites: two mature forest reference sites and five urban sites of varying levels of disturbance. Morphological and polymerase chain reaction–restriction fragment length polymorphism analyses of fungi colonizing root tips revealed that colonization rates and fungal species richness were significantly lower on root systems of seedlings grown in disturbed site soils. Analysis of similarity showed that EMF community composition was not significantly different among several urban site soils but did differ significantly between mature forest sites and all but one urban site. We identified a suite of fungal species that occurred across several urban sites. Lack of a diverse community of belowground mutualists could be a constraint on urban plant community development, especially of late-successional woodlands. Analysis of urban EMF communities can add to our understanding of urban plant community structure and should be addressed during ecological assessment before pragmatic decisions to restore habitats are framed.     

三峡库区不同植被类型土壤养分特征

通过三峡库区8个植被类型370个样地的群落调查和土壤分析,研究了不同植被类型、土壤类型、海拔对表层土壤有机质及全氮、速效磷、速效钾含量的影响.结果表明:(1)三峡库区不同植被类型土壤有机质、全氮平均含量规律为阔叶林＞竹林＞针叶林＞灌丛＞草丛,森林土壤有机质及全氮平均含量丰富;速效磷平均含量表现为草丛＞落叶阔叶林＞灌丛＞暖性针叶林＞常绿落叶阔叶混交林＞温性针叶林＞竹林＞常绿阔叶林,草丛与其他植被类型差异显著;速效钾平均含量表现为常绿落叶阔叶混交林＞落叶阔叶林＞灌丛＞针叶林＞竹林＞草丛＞常绿阔叶林,竹林、草丛、常绿阔叶林与常绿落叶阔叶混交林、落叶阔叶林、灌丛、针叶林差异显著.(2)不同土壤类型养分含量差异显著,黄棕壤中有机质、全氮含量高,分别为6.83%、0.44%,紫色土中速效磷含量高,达到54.24mg/kg.(3)随海拔升高,有机质、全氮含量呈明显增加趋势,速效磷、速效钾含量变化趋势不明显.     

Uptake of 15N-labelled alanine,ammonium and nitrate in Pinus sylvestris L. ectomycorrhiza growing in forest soil treated with nitrogen,sulphur or lime

The uptake of ¹⁵N-labelled alanine, ammonium and nitrate was studied in ectomycorrhizal morphotypes of intact Pinus sylvestris seedlings. PCR-RFLP analysis of the ITS-region of fungal rDNA was used to identify the morphotypes. Seedlings were grown in forest soil collected at an experimental site in southern Sweden. The treatments compared were a control, N fertilisation (600 kg N ha^-1 as urea), sulfur application (1200 kg S ha^-1) and lime application (6000 kg CaCO₃ ha^-1). The forest, which had been dominated by Picea abies, was clear-cut two years before the forest soil was sampled. Soil was also collected from an adjacent standing forest. The aim of the present study was to detect changes in the ectomycorrhizal communities in forest soils and relate these changes to the functional parameter of uptake of nitrogen from organic (alanine and protein) and inorganic (ammonium and nitrate) sources.Liming resulted in the detection of a morphotype not found in other samples, and one morphotype was only found in samples from the standing forest (the fungi in these two morphotypes could not be identified). All mycorrhizal root tips showed a higher ¹⁵N concentration after exposure to different nitrogen forms than non-mycorrhizal long roots. Uptake of¹⁵ N from a labelled solution of alanine or ammonium was higher (about tenfold) than uptake from a ¹⁵N-labelled solution of nitrate. Uptake of ammonium and alanine varied between 0.2 and 0.5 mg N g^-1 h^-1 and between 0.1 and 0.33 mg N g^-1 h^-1, respectively, among the different morphotypes.In seedlings grown in the control soil and in soil from standing forest, alanine and ammonium were taken up to a similar degree from a supply solution by all morphotypes, whereas ammonium uptake was higher than alanine uptake in seedlings grown in lime-treated soil (about twofold) and, to a lesser extent, in the nitrogen- and sulfur-treated soils. The higher ammonium uptake by morphotypes from the limed soil was confirmed in pure culture studies. In cases where ammonium was used as the N source, an isolate of the S. variegatus morphotype collected in the limed soil produced more biomass compared with isolates of S. variegatus collected in nitrogen- or sulphur-treated soil. One isolate of a silvery white morphotype produced about equal amounts of biomass on alanine and ammonium, whereas all S. variegatus isolated performed better with ammonium as their N source. Based on the results it is hypothesised that liming can induce a shift in the ectomycorrhizal community, favouring individuals that mainly utilise inorganic nitrogen over those that primarily utilise organic nitrogen.     

Ectomycorrhizal inoculum potential of northeastern US forest soils for American chestnut restoration: results from field and laboratory bioassays

American chestnut (Castanea dentata) was once a dominant overstory tree in eastern USA but was decimated by chestnut blight (Cryphonectria parasitica). Blight-resistant chestnut is being developed as part of a concerted restoration effort to bring this heritage tree back. Here, we evaluate the potential of field soils in the northern portion of the chestnut's former range to provide ectomycorrhizal (EM) fungus inoculum for American chestnut. In our first study, chestnut seedlings were grown in a growth chamber using soil collected from three sites dominated by red oak (Quercus rubra) as inoculum and harvested after 5 months. Of the 14 EM fungi recovered on these seedlings, four species dominated in soils from all three sites: Laccaria laccata, a Tuber sp., Cenococcum geophilum, and a thelephoroid type. Seedlings grown in the nonsterilized soils were smaller than those growing in sterilized soils. In the second study, chestnut seedlings were grown from seed planted directly into soils at the same three sites. Seedlings with intermingling roots of established trees of various species were harvested after 5 months. Seventy-one EM fungi were found on the root tips of the hosts, with 38 occurring on chestnut seedlings. Multiple versus single host EM fungi were significantly more abundant and frequently encountered. The fungi observed dominating on seedlings in the laboratory bioassay were not frequently encountered in the field bioassay, suggesting that they may not have been active in mycelial networks in the field setting but were in the soils as resistant propagules that became active in the bioassay. These results show that soil from red oak stands can be used to inoculate American chestnut with locally adapted ectomycorrhizal fungi prior to outplanting, a relatively cost effective approach for restoration efforts.     

Nitrogen acquisition and competitive ability of Kalmia angustifolia L., paper birch (Betula papyrifera Marsh.) and black spruce (Picea mariana (Mill.) B.S.P.) seedlings grown on different humus forms

Two species of boreal tree seedlings, paper birch (Betula papyrifera Marsh.) and black spruce (Picea mariana (Mill.) B.S.P.), and the ericaceous shrub Kalmia angustifolia L. were grown in pots with humus from a birch-dominated site and two spruce-Kalmia sites. Root systems interacted with humus form in controlling soil-N cycling as well as energy and nutritional deficiencies of soil microorganisms. In general, Kalmia seedlings affected microbial dynamics and N cycling differently than birch and spruce seedlings did. Birch and spruce seedlings reduced gross N mineralization and immobilization rates, soil mineral-N pools and the amounts of NH –N accreted on buried cation exchange resins in all three soils. Compared to birch and spruce seedlings, the growth of Kalmia resulted in significantly higher gross N mineralization rates, soil mineral-N pools and resin-NH accretion in soil from the fertile birch site. Gross N immobilization rates in all soils were generally higher with Kalmia than with spruce or birch seedlings. All three species of seedlings acquired N from the birch site soil, whereas only Kalmia seedlings acquired N from the two spruce-Kalmia site soils. Relative to control treatments, the amount of N mineralized anaerobically increased in the birch-site soil and decreased in the poor spruce-Kalmia site soil with all three species of seedlings. All seedlings increased the microbial biomass in the birch-site soil. Kalmia humus and Kalmia root systems increased microbial energy-deficiency and decreased microbial nutritional deficiency compared to the other humus and seedlings used. Results are discussed in terms of each species' nutrient acquisition mechanism and its competitive ability during secondary succession.     

Mycorrhiza formation and growth of Eucalyptus globulus seedlings inoculated with spores of various ectomycorrhizal fungi

 As many eucalypts in commercial plantations are poorly ectomycorrhizal there is a need to develop inoculation programs for forest nurseries. The use of fungal spores as inoculum is a viable proposition for low technology nurseries currently producing eucalypts for outplanting in developing countries. Forty-three collections of ectomycorrhizal fungi from southwestern Australia and two from China, representing 18 genera, were tested for their effectiveness as spore inoculum on Eucalyptus globulus Labill. seedlings. Seven-day-old seedlings were inoculated with 25 mg air-dry spores in a water suspension. Ectomycorrhizal development was assessed in soil cores 65 and 110 days after inoculation. By day 65, about 50% of the treatments had formed ectomycorrhizas. By day 110, inoculated seedlings were generally ectomycorrhizal, but in many cases the percentage of roots colonized was low (<10%). Species of Laccaria, Hydnangium, Descolea, Descomyces, Scleroderma and Pisolithus formed more ectomycorrhizas than the other fungi. Species of Russula, Boletus, Lactarius and Hysterangium did not form ectomycorrhizas. The dry weights of inoculated seedlings ranged from 90% to 225% of the uninoculated seedlings by day 110. Although plants with extensively colonized roots generally had increased seedling growth, the overall mycorrhizal colonization levels were poorly correlated to seedling growth. Species of Laccaria, Descolea, Scleroderma and Pisolithus are proposed as potential candidate fungi for nursery inoculation programs for eucalypts. Accepted: 7 May 1998     

Growth,nutrient acquisition and ectomycorrhizae of <Emphasis Type="Italic">Eucalyptus regnans</Emphasis> F. Muell. seedlings in fertilized or diluted air-dried and undried forest soil

Seedlings of Eucalyptus regnans (mountain ash) grow poorly in undried forest soil, where they develop purple coloration in the foliage, but their growth is markedly improved when forest soil has been air dried. Whether this growth promotion is purely due to improved nutrient status of the soil, as a result of air drying, was investigated. In several pot experiments, E. regnans seedlings were grown (i) in air-dried and undried forest soil with addition of different levels of complete fertiliser, (ii) in air-dried or undried soil diluted to different extents with sand, or (iii) in undried soil mixed with different amounts of air-dried soil. Seedling dry weight, P content and incidence of ectomycorrhizal root tips were determined.In all experiments, the dry weights of seedlings were 3–6 times greater in 100% air-dried soil than in 100% undried soil. Fertiliser application resulted in a significant increase in dry weight of seedlings in both air-dried and undried soil, but the dry weights in air-dried soil were always significantly greater than those in undried soil at the same level of fertiliser application. Even at the highest level of fertiliser application, the growth difference between seedlings in air-dried and undried soil remained. When air-dried soil was diluted with sand, there was a significant reduction in seedling dry weight only when soil was diluted to 20% or less (air-dried soil:total mix). Conversly, when air-dried soil was mixed with undried soil, there was a proportional decrease in seedling dry weight with increasing amounts of undried soil. In all experiments, the dominant ectomycorrhizal morphotypes in 100% air-dried soil were different from those in undried soil. Fertilisation and dilution of air-dried and undried soil did not result in a reduction in the overall incidence of ectomycorrhizal root tips, although the frequency of occurrence of different ectomycorrhizal morphotypes was affected.It is concluded that the growth difference between seedlings in air-dried and undried forest soils is not due solely to differences in the direct availability of nutrients in the soils, and different ectomycorrhizae may indirectly affect nutrient availability to the plant.     

Comparisons of ectomycorrhizae on pinyon pines (Pinus edulis; Pinaceae) across extremes of soil type and herbivory

Using field and greenhouse studies, we examined the relationships among pinyon pines (Pinus edulis), their ectomycorrhizal mutualists, and their moth herbivores as a function of soil fertility. We studied two soil types—the ash and cinder soils of the San Francisco volcanic field and nearby sandy loam soils. In the field, pinyons growing in cinders suffered from reduced moisture, negative nitrogen mineralization rates, low phosphate levels, reduced growth, and high moth herbivory relative to pinyons growing in sandy loam. Pinyons growing in cinders also had twofold higher levels of ectomycorrhizal colonization than their noncinder counterparts. Similarly, in the greenhouse, seedlings grown in cinders had higher levels of ectomycorrhizal colonization and greater numbers of ectomycorrhizae than seedlings grown in sandy loam. Seedling shoot growth was significantly enhanced by ectomycorrhizae in both soils. These patterns support three conclusions. First, field and greenhouse studies demonstrated that trees growing in nutrient-poor soils had higher levels of ectomycorrhizal colonization than trees growing in better soils. Second, across soil types, variation in ectomycorrhizal colonization was better predicted by soil fertility than by herbivory. However, herbivory negatively affected ectomycorrhizae in the stressful cinder environment. Third, although mycorrhizae can be parasitic under some conditions, ectomycorrhizae had mutualistic impacts on pinyon seedlings across the environmental extremes we studied.     

亚热带天然次生常绿阔叶林与杉木人工林土壤动物群落特征比较

调查了中亚热带会同林区毗邻的天然次生常绿阔叶林、一代杉木纯林和二代杉木纯林土壤动物群落特征．结果表明,采伐天然林,接着栽植杉木人工林后,土壤动物的多度和多样性均出现明显下降,而土壤动物的生物量和生产力却没有明显差别．杉木连栽对土壤动物的多度、多样性、生物量影响甚少,特别是杉木一、二代土壤动物的生产力接近相等．此项研究结果支持植被是影响土壤动物演替的一个主要原因,也暗示杉木长期连作对土壤动物群落的影响是一个非常缓慢的过程．     

Correlation of greenhouse bioassay with field response to fertilizer by paper birch

Summary Bulk soil samples were collected from the top 15 cm of untreated areas adjacent to field fertilizer trials at 2 locations. Amounts of N, P, K, and lime equivalent to the field treatments were mixed with the soil in 15-cm diameter pots. Paper birch (Betula papyrifera March.) trees were grown from seed for a greenhouse bioassay. Height and dry weight of the bioassay seedlings were significantly correlated with 3-year volume growth of 10-year-old paper birch seedlings in the field. Correlation coefficients were 0.88 for height growth and 0.91 for dry weight growth on one site, and 0.72 and 0.63 on the other. With further refinements and observations on a larger number of sites, this bioassay technique should be a valuable tool for estimating potential response to fertilizer by young paper birch in the field, and for ranking the relative productivity of different soils.     

川西亚高山森林凋落物去除对土壤腐殖质动态的影响

森林凋落物作为森林土壤腐殖质的主要来源, 在土壤腐殖质的形成中发挥着重要作用, 但不同森林类型凋落物因其含量、组成等的不同, 对土壤腐殖质的影响也不同。该研究以川西亚高山针叶林、阔叶林和针阔混交林3种不同森林类型为对象, 采用凋落物原位控制实验, 对比研究不同关键期凋落物去除对土壤可提取腐殖质、胡敏酸和富里酸含量及胡敏酸/富里酸、胡敏酸/可提取腐殖质的影响。主要结果: (1)土壤可提取腐殖质、胡敏酸和富里酸含量在不同森林类型中差异显著。土壤可提取腐殖质含量总体表现为针叶林>针阔混交林>阔叶林, 胡敏酸含量总体表现为针阔混交林>针叶林>阔叶林, 而富里酸含量则表现为针叶林>阔叶林>针阔混交林, 其中3种林型中土壤腐殖质的主要成分为富里酸, 总体均表现为富里酸型。不同采样时期也显著影响了土壤可提取腐殖质、胡敏酸和富里酸含量, 总体均表现为先升高后下降的趋势。除个别采样时期外, 凋落物去除总体降低了土壤可提取腐殖质、胡敏酸和富里酸的含量。(2)胡敏酸/富里酸和胡敏酸/可提取腐殖质的结果显示3种林型土壤总体腐殖化程度均较低, 整体表现为针阔混交林>阔叶林>针叶林, 凋落物去除在一定程度上有利于提高阔叶林与针阔混交林的腐殖质品质。(3)相关分析表明不同凋落物处理间土壤可提取腐殖质与土壤有机碳含量、全氮含量和土壤含水量呈显著正相关关系, 与温度呈显著负相关关系。综上所述, 短期的凋落物去除会降低土壤腐殖物质的含量, 但不同林型间由于凋落物类型差异会导致土壤腐殖质的不同变化, 说明土壤腐殖质的动态变化受凋落物类型以及环境因素的综合调控。因此, 关于凋落物变化对土壤腐殖质的影响还需进一步的长期研究。