Quantities and types of ectomycorrhizal and endophytic fungi associated with Betula platyphylla var. japonica seedlings during the initial stage of establishment of vegetation after disturbance

Ectomycorrhizal and endophytic fungi of Betula platyphylla Sukatchev var. japonica Hara seedlings were investigated by bioassay using soils from sites where the surface layer had been removed by destructive disturbances. Soil samples were taken from sites A, B, C and D, where 1, 2–3, 4–5, and 7–8 years, respectively had passed since disturbance. Naturally regenerated B. platyphylla var. japonica seedlings grew at sites C and D, but not at sites A or B. The percentages of ectomycorrhizal formation in seedlings were significantly lower in the soils from site A (4%) and site B (13%), compared to those in the soils from site C (53%) and site D (37%). The numbers of ectomycorrhizal morphologic types in sites A, B, C, and D were eight, five, one, and seven, respectively. The same dominant type of ectomycorrhiza was found in sites C and D, and this type was different from those in sites A and B. The frequencies of colonization of seedling roots by endophytic fungi, especially Mycelium radicis atrovirens Melin (MRA) in soils from sites A and B were 31 and 33%, respectively; these frequencies were significantly higher than those for site C (0%) and site D (2%). During the initial stage of establishment of vegetation following disturbance, the quantities and types of ectomycorrhizal fungi in the field that have the potential to associate with B. platyphylla var. japonica might rapidly change after invasion of the host plant. Ectomycorrhizal fungi seemed to compete with endophytic MRA fungi for colonization of the roots of B. platyphylla var. japonica seedlings.     

Antioxidant and anticancer activity of extract from Betula platyphylla var. japonica

The antioxidant and anticancer properties of a medicinal plant, Betula platyphylla var. japonica were investigated. The total methanol extract of B. platyphylla var. japonica had protective effects against hydrogen peroxide (H2O2) in the Chinese hamster lung fibroblast (V79-4) cell line and induced apoptotic cell death in human promyelocytic leukemia (HL-60) cells, a cancer cell line. B. platyphylla var. japonica extract significantly increased cell viability against H2O2. The extract also showed high 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50 2.4 microg/ml) and lipid peroxidation inhibitory activity (IC50 below 4.0 microg/ml). Furthermore, B. platyphylla var. japonica extract reduced the number of V79-4 cells arrested in G2/M in response to H2O2 treatment and increased the activities of several cellular antioxidant enzymes, including superoxide dismutase, catalase and glutathione peroxidase. Treatment with B. platyphylla var. japonica extract induced cytotoxicity and apoptosis in HL-60 cells, as shown by nucleosomal DNA fragmentation, increases in the subdiploid cell population, and fluorescence microscopy. B. platyphylla var. japonica extract gradually increased the expression of pro-apoptotic Bax and led to the activation of caspase-3 and cleavage of PARP. These findings suggest that B. platyphylla var. japonica exhibits potential antioxidant and anticancer properties.     

Effect of flooding and temperature regime on growth and stomatal resistance ofBetula platyphylla var.japonica seedlings

Summary Both flooding and low temperature reduced height and stem diameter growth; leaf initiation; growth of leaves, stems, and roots; and lowered root-shoot ratios of 112-dayoldBetula platyphylla var.japonica seedlings. Flooding also induced leaf scorching and abscission. Growth was reduced much more by flooding than by low temperature. Interactive effects of flooding and temperature were shown on height growth, leaf initiation and expansion, and dry weight increment of leaves, stems and roots. The amount of growth reduction by flooding and low temperature was greater when based on analysis of dry weight increment of leaves, stems, and roots, than on their relative growth rates. The greater reduction of growth by flooding than by low temperature was associated with fewer and smaller leaves, more leaf injury, more stomatal closure, and greater decay of roots in flooded plants. Flooding and low temperature appeared to reduce growth by somewhat different physiological mechanisms. Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI, USA and by Yamagata University, Tsuruoka, Japan. McIntyre-Stennis Project 2599.     

Effects of manganese toxicity on photosynthesis of white birch (Betula platyphylla var. japonica) seedlings

The effects of manganese (Mn) toxicity on photosynthesis in white birch ( Betula platyphylla var. japonica ) leaves were examined by the measurement of gas exchange and chlorophyll fluorescence in hydroponically cultured plants. The net photosynthetic rate at saturating light and ambient CO₂ (C_a) of 35 Pa decreased with increasing leaf Mn concentrations. The carboxylation efficiency, derived from the difference in CO₂ assimilation rate at intercellular CO₂ pressures attained at C_a of 13 Pa and O Pa, decreased with greater leaf Mn accumulation. Net photosynthetic rate at saturating light and saturating CO₂ (5%) also declined with leaf Mn accumulation while the maximum quantum yield of O₂ evolution at saturating CO₂ was not affected. The maximum efficiency of PSII photochemistry (F_v/F_m) was little affected by Mn accumulation in white birch leaves over a wide range of leaf Mn concentrations (2–17 mg g₋₁ dry weight). When measured in the steady state of photosynthesis under ambient air at 430 μmol quanta m₋₂ s₋₁, the levels of photochemical quenching (qP) and the excitation capture efficiency of open PSII (F'^v/F'^m) declined with Mn accumulation in leaves. The present results suggest that excess Mn in leaves affects the activities of the CO² reduction cycle rather than the potential efficiency of photochemistry, leading to increases in Q_A reduction state and thermal energy dissipation, and a decrease in quantum yield of PSII in the steady state.     

Callus proliferation from leaf protoplasts using phenylurea type cytokinin, 4-PU,inBetula platyphylla VAR.Japonica

Summary Protoplasts were isolated from leaves ofBetula platyphylla var.japonica using a 0.6M mannitol solution containing 1% Cellulase Onozuka R-10 and 1% Driselase. The cell division and colony formation were largely enhanced using Murashige and Skoog (1962) liquid medium at half strength (1/2 MS), containing 0.6M mannitol, 0.09M sucrose, and factorial combinations of 0.1–30 μM N-(2-chloro-4-pyridyl)-N′-phenylurea (4-pu) and 0.1–10 μM 1-naphthaleneacetic acid (NAA) or 0.1–30 μM 2,4-dichlorophenoxyacetic acid (2,4-D). The optimal protoplast density was 5–7 × 10⁴/ml. Continuous callus proliferation from protoplasts was achieved by transferring colonies to fresh 1/2 MS agar medium containing 1 μM NAA and 1 μM 4-pu with no mannitol. It appeared that supplementation of the medium with phenylurea type cytokinin, 4-pu gave the successful callus proliferation from the protoplasts ofB. platyphylla.     

The effects of phenolic glycosides from Betula platyphylla var. japonica on adipocyte differentiation and mature adipocyte metabolism

Betula platyphylla var. japonica (Betulaceae) has been used traditionally in Asian countries for the treatment of inflammatory diseases. A recent study has reported a phenolic compound, platyphylloside from B. platyphylla, that shows inhibition on adipocyte differentiation and induces lipolysis in 3T3-L1 cells. Based on this finding, we conducted phytochemical analysis of the EtOH extract of the bark of B. platyphylla var. japonica, which resulted in the isolation of phenolic glycosides (1–4). Treatment of the isolated compounds (1–4) during adipocyte differentiation of 3T3-L1 mouse adipocytes resulted in dose-dependent inhibition of adipogenesis. In mature adipocytes, arylbutanoid glycosides (2–4) induced lipolysis related genes HSL and ATGL, whereas catechin glycoside (1) had no effect. Additionally, arylbutanoid glycosides (2–4) also induced GLUT4 and adiponectin mRNA expression, indicating improvement in insulin signaling. This suggests that the isolates from B. platyphylla var. japonica exert benefial effects in regulation of adipocyte differentiation as well as adipocyte metabolism.     

Floral sex ratio variation in hermaphrodites of gynodioeciousChionographis japonica var.kurohimensis Ajima et Satomi (Liliaceae)

Intrapopulation and interpopulation variations in floral sex ratio in hermaphrodites of gynodioeciousChionographis japonica var.kurohimensis (Liliaceae) were examined. The relative ratio of male flowers to total flowers (male and perfect flowers) decreased with plant size, suggesting size-dependent gender modification. The relative ratio of male flowers per population-basis is negatively correlated with the mean number of perfect flowers. Since the number of perfect flowers proportionally increased with plant size, populations showing low maleness consist of relatively bigger plants and are considered to be in high-quality environment. On the other hand, the relative ratio of male flowers per population basis is independent of female frequency in the population. Plasticity in gender expression probably plays an important role of maintenance of gynodioecy inC. japonica var.kurohimensis.     

华重楼内生真菌聚多曲霉的促生与拮抗作用

[背景]华重楼(Paris polyphylla var.chinensis)是我国一种名贵稀缺中药材,有多种药效,由于过度采挖等原因,其野生资源现已极度匮乏.华重楼的人工栽培技术尚未成熟,生长缓慢、病害频繁发生是主要的制约因素.[目的]植物益生菌的开发是一种环保且有效的解决途径,符合生态种植的要求.[方法]通过常规方...     

干旱条件下接种AM真菌对小马鞍羊蹄甲幼苗根系的影响

为了探讨岷江干旱河谷丛枝菌根真菌(AMF)对寄主植物幼苗根系的影响,通过接种购买的AMF摩西球囊霉菌(Funneliformis mosseae)到优势乡土灌木小马鞍羊蹄甲(Bauhinia faberi var.microphylla)幼苗,在重度、中度和轻度干旱条件下培养3个月,研究不同干旱条件下AMF对幼苗根系形态特征、结构特征、功能性状的影响。方差分析结果表明:(1)3种干旱胁迫条件下,接菌均显著增加了幼苗的根总长、根表面积、根分枝数、根尖数(P0.001),在中度胁迫和轻度胁迫下,接菌显著促进根鲜重、根体积的增加(P0.001),轻度胁迫条件下接菌幼苗的根鲜重、根总长、根表面积、根体积、根尖数最高并显著高于其它处理,但接菌与未接菌的根平均直径之间没有显著差异;(2)接菌幼苗根系趋向于叉状分支结构,在重度胁迫时,叉状分支趋势更显著(P0.001);(3)接菌幼苗的根比例都显著小于未接菌的,但幼苗比根长不存在显著差异。相关分析结果表明:菌根侵染率与根鲜重、根总长、根表面积、根体积、根分枝数、根尖数呈极显著正相关(P0.001),与拓扑指数、根比例呈极显著负相关(P0.001)。研究表明,在干旱条件下,AMF虽然没有提高生长初期的根系的吸收效率,但接种AMF显著影响幼苗根系形态特征和结构特征,更利于植物适应干旱环境,并且AMF对幼苗根系的促生作用随着干旱胁迫程度减轻而提高。     

樟子松固沙林生长对土壤磷素变化的影响

磷是森林生态系统重要养分元素之一,是干旱半干旱地区植物生长的限制性因子。然而沙质草地转化为人工林生态系统后,林分的生长对沙地土壤磷素的变化及其影响机理还不清晰,为沙地合理经营和管理人工林带来了不确定性。以辽宁省章古台地区各生长阶段(幼龄林、中龄林、成熟林和过熟林阶段)的20块樟子松固沙林样地(在各生长阶段林分附近寻找1块天然草地作为对照样地)为研究对象,取样并测定样地各土层(0—10、10—20、20—40、40—60、60—80、80—100 cm)的土壤磷(全磷和速效磷)、土壤氮(全氮和速效氮)、土壤钾(全钾及速效钾)、土壤有机碳等含量以及土壤含水率、土壤pH值、土壤质地、土壤容重等因子值,并进行统计分析。结果表明:沙质草地营造樟子松人工林后,土壤全磷含量随林龄的增加而逐渐递增,成熟林时期达到最高,过熟林地全磷降低,且土壤全磷对土层深度不敏感。成熟林地的速效磷含量略高于幼林和中龄林;虽然与幼林、中龄林没有显著差异,但过熟林的土壤速效磷含量是所有林分中最低的。除了林分生长影响外,草地营造樟子松林后,土壤全磷的变化还受土壤容重和土壤速效氮含量的影响,而土壤速效磷的变化受土壤有机碳和pH...     

Evaluation of endophytic actinobacteria as antagonists of Gaeumannomyces graminis var. tritici in wheat

Endophytic actinobacteria isolated from healthy cereal plants were assessed for their ability to control fungal root pathogens of cereal crops both in vitro and in planta. Thirty eight strains belonging to the genera Streptomyces, Microbispora, Micromonospora, and Nocardioidies were assayed for their ability to produce antifungal compounds in vitro against Gaeumannomyces graminis var. tritici (Ggt), the causal agent of take-all disease in wheat, Rhizoctonia solani and Pythium spp. Spores of these strains were applied as coatings to wheat seed, with five replicates (25 plants), and assayed for the control of take-all disease in planta in steamed soil. The biocontrol activity of the 17 most active actinobacterial strains was tested further in a field soil naturally infested with take-all and Rhizoctonia. Sixty-four percent of this group of microorganisms exhibited antifungal activity in vitro, which is not unexpected as actinobacteria are recognized as prolific producers of bioactive secondary metabolites. Seventeen of the actinobacteria displayed statistically significant activity in planta against Ggt in the steamed soil bioassay. The active endophytes included a number of Streptomyces, as well as Microbispora and Nocardioides spp. and were also able to control the development of disease symptoms in treated plants exposed to Ggt and Rhizoctonia in the field soil. The results of this study indicate that endophytic actinobacteria may provide an advantage as biological control agents for use in the field, where others have failed, due to their ability to colonize the internal tissues of the host plant.     

Effects of vegetation change and soil disturbance on ectomycorrhizas ofBetula platyphylla var.japonica: A test using seedlings planted in soils taken from various sites

The occurrence and character of different types of ectomycorrhizas of birch seedlings were investigated in soils from three naturally regenerating birch stands: a forest site, a clear-cut site, and a site recently disturbed by plowing. Birch grown in soil from an evergreen broad-leaved forest without birch was also studied. The rate of ectomycorrhizal formation in the soil from the evergreen broad-leaved forest was lower than that in the soil from the other three sites. The ectomycorrhizal formation of seedlings grown in soil from the clear-cut and plowed sites were the same as or higher than that in soil from the birch forest site. The largest number of ectomycorrhizal types were formed in soil from the birch forest site. In the soil from the plowed site, only one type of ectomycorrhiza was formed, and it was different from the dominant type formed in soils from the birch forest site and the clear-cut site. The results of this investigation showed that equal levels of ectomycorrhizas were formed in soils from the different birch stands, but the types formed were different among those sites. It is likely that the different ectomycorrhizal fungi were better adapted to the soil conditions at each of those sites.     

Endophytic fungi associated with Fallopia japonica (Polygonaceae) in Japan and their interactions with Puccinia polygoni-amphibii var. tovariae, a candidate for classical biological control

Fallopia japonica (Polygonaceae), or Japanese knotweed, is now spreading globally, causing serious problems in Europe and North America in both natural and urban habitats. There is an urgent need for alternative management solutions, and classical biological control, using coevolved natural enemies found in the native range, is currently being investigated. Here, we isolated fungal endophytes from F. japonica in Japan, its natural habitat, to find endophytes that might increase the virulence of a coevolved rust pathogen, Puccinia polygoni-amphibii var. tovariae. A total of 1581 fungal endophytes were recovered from F. japonica and classified into 15 taxa. Five genera (Colletotrichum, Pestalotiopsis, Phoma, Phomopsis, and Alternaria) were dominant as endophytes in F. japonica. A greenhouse study of the dominant endophyte-pathogen interactions revealed three types of reactions: suppressive, synergistic, and neutral. In particular, one Phomopsis isolate--closely related to Diaporthe medusaea, based on ITS sequences--promoted the pathogenic aggressiveness of P. polygoni-amphibii var. tovariae and, therefore, this interaction is potentially useful to increase the effectiveness of the rust fungus as a biological control agent of F. japonica in its invasive range.     

温度、pH及干旱胁迫对沙地樟子松外生菌根菌生长影响

通过对采集于沙地樟子松人工林内的3种外生菌根真菌（牛肝菌Boletus sp.、乳菇Lactariussp.、高环柄菇Macrolepiota procera）进行纯培养,在不同温度、pH值和PEG模拟干旱胁迫条件下,观测了外生菌根菌的生长发育状况.结果表明,3种外生菌根菌生物量在不同pH范围（3～7）内存在着显著差异（P＜0.05）;在低于5℃和高于37℃时,3种外生菌根菌均不能生长,其最适生长温度分别为：牛肝菌,25℃高环柄菇,25～28℃,乳菇,25～30℃;在低浓度PEG胁迫处理条件下（10%,-0.20MPa）,3种外生菌根菌的生长均有所增加,当PEG胁迫达到30%（-1.53 MPa）时,3种外生菌根菌的生长均受到抑制.与上述结果比较,沙地樟子松人工林地土壤的实际pH值在外生菌根菌的最适生长范围内;林地最高气温值远远超过3种外生菌根菌的最适生长值的时间在每年的生长季都会出现;在极端干旱年份（如1996年）,林地土壤的实际含水量在生长季节（5～9月）远远低于抑制外生菌根菌生长的土壤含水量,可能影响到外生菌根菌的生存.因此,可以推断,沙地樟子松人工林地的外生菌根菌的生长与发育,在干旱胁迫及高温作用下受到很大程度的影响,如果仅从微生物角度分析,外生菌根菌在干旱和高温条件下不能生长或已经死亡是导致沙地樟子松人工林衰退的一个原因.     

干旱胁迫对蒙古黄芪生长及根部次生代谢物含量的影响

以山西道地药材黄芪一年生幼苗为试验材料,设置常规水分条件(CK)、轻度干旱胁迫(A1)、中度干旱胁迫(A2)、重度干旱胁迫(A3)4个不同处理,研究土壤干旱胁迫对黄芪生长及生理的影响。结果表明:黄芪茎叶快速生长集中在出苗后80—120d,以后生长减缓;当茎叶枯萎时,根中生物量短期快速积累。与常规水分条件相比,干旱胁迫处理显著降低了黄芪苗高及茎叶生物量,但对抗氧化能力、根系生长及次生代谢物积累产生了不同的影响。轻度干旱胁迫下SOD、POD、CAT 3种抗氧化酶活性升高,丙二醛(MDA)含量和细胞膜透性降低,同时根长与根生物量增加、多糖与皂苷两种次生代谢物积累增多,黄芪药材的质量得到显著提高(P0.05);胁迫上升到中度、重度时,SOD酶活性逐渐降低,重度胁迫下低于对照,而POD及CAT酶活性、MDA含量、细胞膜透性均随胁迫增强而升高,相反,根长、根生物量、多糖与皂苷含量降低,导致黄芪药材的质量显著降低(P0.01)。综上表明,干旱胁迫下,SOD酶表现较为敏感,可能在清除活性氧中起主要作用;轻度水分胁迫能有效启动黄芪体内抗氧化酶系统和次生代谢,它们相互协作共同对抗胁迫对细胞产生的伤害,通过降低地上部分的生长,将营养物质优先运往根部,促进根产量及药材质量的提高。这一结论,可在黄芪多糖和皂苷次生代谢物定向培育的水分管理中加以利用。     

樟子松固沙林更新迹地草本植物多样性及其对土壤理化性质的影响

以科尔沁沙地南缘的彰武县章古台万亩林为研究对象,野外取样调查和实验室检测分析相结合,以樟子松固沙林采伐迹地为对照,研究不同植被恢复类型下樟子松固沙林更新迹地生境的改良效果,探讨植被重建后植物多样性及土壤理化性质的响应。结果表明:1)樟子松(Pinus sylvestris)固沙林更新迹地植被重建后,草本植物物种多样性增加,林下植物偶见种数目增多,13种草本植物在8个样地中未重复出现;2)与采伐迹地相比,不同植被重建类型土壤理化性质均有所改善,土壤容重、田间持水量、有机质、全氮、碱解氮、速效钾在彰武小钻杨(Populus xiaozhuanica)、五角枫(Acer mono)林地改良效果较好,全钾在红刺榆林(Hemiptelea davidii)地含量明显提高、山杏(Armeniaca sibirica)林地的有效磷相比采伐迹地明显提高,且均表现为上层改良效果优于下层;3)不同植被恢复类型土壤理化性质间存在显著差异,随着物种多样性的增加,土壤理化性质逐渐改善,土壤容重、田间持水量、有机质、全磷与植物多样性具有显著的相关性,土壤理化性质的与植物多样性相互作用,共同促进生态系统正向演替。研究结果为控制科尔沁沙地土壤沙化,加速该区生态系统的恢复与重建提供理论依据。     

Effects of understory dwarf bamboo on soil water and the growth of overstory trees in a dense secondary <Emphasis Type="Italic">Betula ermanii</Emphasis> forest,northern Japan

The effects of understory dwarf bamboo (Sasa kurilensis) on soil water and the growth of overstory trees were studied in a dense secondary forest of Betula ermanii in northern Japan. Four plots were established in a Betula ermanii forest with Sasa kurilensis in the understory. The Sasa was removed in two of the plots. The annual increment of the trunk diameter for each tree was measured in the first two years from the commencement of the experiment. Soil water potential was similar in the plots following significant rainfall, but was found to be greater in the plot without Sasa between rainfall events. This suggests that the removal of Sasa slows the reduction of soil water after rainfall. The relative growth rate of the trunk diameter of Betula ermanii increased with tree size in all of the plots because taller trees strongly suppressed smaller ones in the dense forest. The growth rates of Betula ermanii were higher in the plots without Sasa. However, the difference in growth rates between all of the plots tended to be smaller in smaller size classes, possibly because smaller trees were strongly suppressed by larger ones, irrespective of the presence/absence of Sasa. Therefore, the removal of Sasa increased soil water and encouraged the growth of larger Betula ermanii in dense forest during the first two years after the Sasa was removed. The present study suggests that Sasa can reduce the growth of larger Betula ermanii in dense forest by limiting available soil water to these trees.     

南方红豆杉水浸提液对喜树种子发芽和幼苗生长的化感作用

化感作用是影响人工混交林种间关系的重要因素之一。已有研究表明：喜树南方红豆杉混交对喜树生长有明显促进作用,并从混交改善混交林地微气候角度解释了这种促进作用,但未从种间化感作用角度探讨这种作用。为了探究南方红豆杉是否对喜树具有潜在的化感促进作用,从而更全面了解喜树南方红豆杉混交林种间关系,考察了不同浓度（25、50 g/L和100 g/L）的南方红豆杉（Taxus chinensis var.mairei）鲜叶、凋落叶、枝和根水浸提液对喜树（Camptotheca acuminata）种子发芽和幼苗生长的影响。结果表明：（1）南方红豆杉凋落叶浸提液对喜树种子发芽和幼苗生长无显著影响（P>0.05）,而鲜叶、枝和根浸提液对喜树发芽和幼苗生长均具有不同程度的促进作用（P<0.05）,且作用强度大体与浓度呈正相关;（2）100 g/L的南方红豆杉鲜叶、枝和根浸提液浸泡的喜树种子,其发芽率比对照组分别提高8.1%、14.9%和25.6%;（3）南方红豆杉鲜叶浸提液只有在高浓度（100 g/L）时,对喜树幼苗基径生长具有促进作用（P<0.05）,而对其株高、全株干重和净光合速率无显著影响;南方红豆杉根和枝浸提液对喜树幼苗株高、基茎、干重和净光合速率均具有促进作用（P<0.05）,与对照组相比,100 g/L的根和枝浸提液浇灌喜树幼苗,可以使喜树幼苗株高分别提高14.2%和8.4%,基径分别提高19.0%和15.3%,干重分别提高23.1%和15.9%,净光合速率分别提高11.6%和6.1%。研究结果表明,在喜树南方红豆杉混交林中,南方红豆杉对喜树的正向化感作用可能是促进喜树生长的重要因素之一。     

科尔沁沙地樟子松人工林土壤真菌共现网络及其与土壤因子的关系

为揭示科尔沁沙地樟子松(Pinus sylvestris var.mongolica)人工林土壤真菌间相互作用,以不同林龄(中龄、近熟和成熟)、不同土层(0—10和10—20 cm)樟子松人工林土壤为研究对象,以未造林地为对照样地,采用分子生态网络分析法,基于随机矩阵理比较分析樟子松人工林土壤真菌网络特征及其影响因素。研究结果表明：(1)中龄林到近熟林阶段,科尔沁沙地樟子松人工林土壤真菌网络平均连通度增大,平均路径长减小,网络愈加复杂,而近熟林到成熟林阶段则相反,网络愈加简单;不同土层间,10—20 cm土层土壤真菌平均路径长度小于0—10 cm土层,平均连通度和聚类系数大于0—10 cm土层,10—20 cm较0—10 cm土壤真菌间相互联系更为密切;与樟子松人工林相比,未造林地土壤真菌网络中的平均连通度略低于近熟林,平均路径长低于樟子松人工林,未造林地土壤真菌群落更不稳定。(2)中龄、近熟和成熟樟子松人工林土壤真菌关键菌种分别为Guehomyces sp.、Oidiodendron sp.和Pseudeurotium sp.,未造林地关键菌种为Alphamyces sp.。在0—1...     

樟子松人工林营建对土壤颗粒组成变化的影响

植被恢复是退化生态系统的主要恢复措施,也是人类改善区域生态环境较为重要和直接的活动。目前,针对不同植被恢复方式对干旱半干旱地区土壤理化性质及生物特征开展了大量研究。然而,关于科尔沁沙地樟子松人工林营建对土壤颗粒组成变化的影响却鲜有报道。因此,以辽宁省章古台地区不同生长阶段(包括幼龄林、中龄林、成熟林和过熟林)的20块樟子松人工林样地为研究对象(以临近的7块天然草地为对照),研究了沙地樟子松人工林营建对0—100 cm土层土壤颗粒组成变化的影响。结果表明:沙质草地营建樟子松人工林后,不同土层土壤细颗粒(<0.05 mm)含量均呈增加趋势,并且在0—10 cm层增加趋势明显,随土层深度增加土壤细颗粒增加量逐渐降低(除幼龄林外),但樟子松林地土壤颗粒组成仍以砂粒为主,土壤粘粒和粉粒含量极低(仅占5%左右)。随着樟子松人工林林龄的增加,土壤细颗粒变化量在0—10 cm层逐渐升高,而在10—100 cm层并无显著变化趋势。土壤细颗粒含量的变化在10—100 cm层与土壤含水量呈显著正相关,在0—10、20—40 cm和80—100 cm层与土壤全钾极显著负相关,在20—60 cm层与土壤有...