入侵植物加拿大一枝黄花根际解钾菌多样性及解钾活性

入侵植物加拿大一枝黄花(Solidagocanadensis)具有较强的钾(K)富集能力,这可能和其对土壤微生物群落的改变有关。根际解钾菌能够将植物难以利用的矿物态钾转化为植物可以利用的可溶性钾,而加拿大一枝黄花如何影响根际解钾菌多样性和解钾活性尚未明了。该研究以浙江省杭州湾湿地围垦区内自然生长的加拿大一枝黄花和其伴生本地植物白茅(Imperata cylindrica)为研究对象,比较了加拿大一枝黄花和白茅体内及土壤中的钾含量水平,钾供给水平对生物量积累的影响,以及根际解钾菌的数量、多样性和解钾活性的差异。结果表明,加拿大一枝黄花茎、叶中的钾含量均显著高于白茅,分别是白茅的1.59和7.33倍;加拿大一枝黄花和白茅的土壤全钾含量差异不显著,速效钾含量在0-10 cm土层中差异显著、在10-20 cm土层中差异不显著。随着钾供应水平提高,加拿大一枝黄花和白茅的生物量均显著增加。利用解钾培养基计数培养后发现,加拿大一枝黄花根际解钾菌的数量是白茅的3.51倍。分离培养后将出现解钾圈的菌株进行鉴定,利用解钾液体培养实验测定其解钾量,发现从加拿大一枝黄花根际土中分离得到的15个解钾菌株中,有9个具有高效解钾能力,其处理液中K+含量较空白对照高出85.11%-192.54%,其中菌株H2-20解钾能力最强,解钾量为10.657 mg·L-1。加拿大一枝黄花根际解钾菌解钾作用显著高于白茅。经16Sr DNA鉴定发现,加拿大一枝黄花15个根际解钾菌株分属11个属,其中有6个属已经被报道证实具有明显解钾能力。这些结果表明加拿大一枝黄花根际解钾菌数量较为丰富,且大多具有较高解钾活性,可能对其钾富集具有重要贡献。     

钾长石矿区土壤解钾菌的分离与多样性

目的获得高效钾长石分解细菌及分析钾长石矿区土壤中解钾菌的多样性。方法采集湖南省吉首市钾长石矿区土壤,用钾长石为唯一钾源的选择性培养基筛选分离解钾细菌,采用形态特征观察、生理生化特性检测和基于16S rRNA基因序列的系统发育分析初步鉴定解钾菌株,并测定菌株摇瓶条件下的解钾能力。结果分离获得38株钾长石分解细菌,分别属于13个属,其中13株菌为剑菌属,4株菌为芽胞杆菌属。菌株L17的发酵液中有效钾含量最高,为87.66 mg/L,是对照组的15.8倍。结论钾长石矿区土壤细菌种类有较好的多样性,其中剑菌属和芽孢杆菌属为优势种群,Mitsuaria属的L17解钾能力最强。     

高效钾长石分解菌株的筛选、鉴定及解钾活性研究

目的 筛选高效的钾长石分解细菌,并进行初步鉴定和解钾活性测定.方法 采集湖南省桂东县钾长石开采区土壤,利用钾长石为唯一钾源的选择性培养基筛选分离解钾细菌,通过摇瓶释钾试验复筛高效解钾菌株;同时,利用ICP-OES测定解钾菌的释钾效率.采用形态特征观察、生理生化特性检测和基于16S rRNA基因序列的系统发育分析初步鉴定高效解钾菌株.结果 分离获得11株生长良好的钾长石分解细菌,其中菌株JKC1、JKC2、JKC5和JKC7的解钾能力较强,解钾率分别为11.00％、11.50％、12.70％和11.70％.经初步鉴定JKC1为Bacillus megaterium,JKC2为Bacillus aryabhattai,JKC5为Azotobacter chroococcum,JKC7为Microbacterium trichothecenolyticum.结论 菌株JKC1、JKC2、JKC5和JKC7是高效的钾长石分解菌,可作为微生物浸矿(钾长石)机制研究的候选菌株.     

解钾促生菌的筛选鉴定及对东北黑土区玉米的促生效应

【背景】东北地区作为全国玉米的主产区,土壤缺钾严重限制了玉米的高产。解钾促生菌可活化土壤中难溶的钾,提高土壤钾的有效性,进而促进植物生长。【目的】从中国东北黑土区的玉米根际土壤中筛选鉴定高效解钾菌,研究其在缺钾条件下对玉米生长的促生效果,为开发适应当地环境的微生物钾肥提供优良的菌种资源。【方法】采用选择性培养基从玉米根际土中筛选解钾菌;采用16S r RNA基因测序方法鉴定菌株的分类地位;采用生理生化特征鉴定培养基测定其生态适应性(耐酸碱、耐盐、耐干旱及耐农药);2年的田间接种试验验证解钾菌在缺钾条件下对玉米的促生效果。【结果】筛选出3株高效解钾促生菌MZ4、KM1和KM2,经鉴定MZ4和KM2属于芽孢杆菌属,KM1属于短小芽孢杆菌属;3株菌可耐受强干旱、强碱、不同浓度的吡虫啉和嘧菌酯,并耐受一定程度的酸和盐;田间试验结果表明,与缺钾区不接种解钾菌相比,接种MZ4、KM1和KM2增加了拔节期、吐丝期玉米的株高、地上生物量、叶面积指数和叶绿素,接种MZ4和KM2显著增加了玉米产量,可增产9.65%-11.50%。【结论】鉴定出适合东北黑土区的高效解钾微生物,为该区域微生物钾肥研发及微生物解钾机理研究提供了优良菌种资源。     

香蕉根际土壤解钾放线菌的筛选鉴定及解钾特性研究

旨在根据解钾菌的解钾特性和机理,从香蕉根际土壤中分离获得解钾能力较强且十分稳定的高效解钾放线菌。首先,通过解钾分离培养基和筛选培养基的初筛,获得一批高效解钾菌,然后在实验室条件下鉴定菌株类型和测定解钾率,得到一株高效解钾放线菌。最后通过形态观察、生理生化实验和16S r RNA基因序列分析对所筛菌株进行鉴定,并测定不同条件下的解钾率,对其解钾特性进行了研究。结果显示,从香蕉根际土壤中筛选出16株高效解钾菌,通过鉴定和解钾率的测定,最终获得一株稳定的解钾链霉菌(Streptomycete)M3-4,其在120 h,30℃,p H为6,钾长石粉为5 g,摇床转速为250 r/min条件下,以麦芽糖为碳源,蛋白胨为氮源时解钾率达最大值。该菌株为陕西链霉菌(Streptomyces shaanxiensis),解钾率约为20%。     

钾细菌JF88菌株解钾作用及应用研究

采用比浊法测定JF88菌株的解钾能力,其结果为接菌处理水溶性钾比不接菌增加30．5％,可作为钾细菌肥料的生产菌种,对农业环保具有一定的理论和实践意义。     

土生空团菌对白云母的风化作用及解钾特性

摘要:【目的】为了提高森林土壤含钾硅酸盐矿物利用率和改善树木钾素营养,探讨外生菌根真菌对白云母矿物的解钾及风化效应。【方法】通过5种外生菌根真菌在贫钾条件下与白云母的相互作用,考察了3种常用培养基对菌株解钾能力的影响;采用解钾效果最高的土生空团菌在Modified Melin-Norkrans(MMN)培养基条件下,进一步研究了21d浸出过程中主要矿质元素的释放量、生物量、剩余葡萄糖量、产生的小分子有机酸种类及含量、菌丝-矿物微环境的改变,利用扫描电子显微镜观测白云母被风化的痕迹。【结果】培养基对不同外生菌根真菌解钾能力的影响各异,其中土生空团菌在MMN培养基条件下解钾能力最强,其解钾量与生物量、剩余葡萄糖量、pH值显著相关。土生空团菌能够分泌有助于菌丝-矿物粘附的胞外多糖以形成菌丝-矿物微环境,并富集有机酸,促进微环境内钾的释放;菌丝不仅能够粘附在白云母表面产生刻蚀作用,还能破坏矿物深入其内部。【结论】外生菌根真菌具有促进白云母风化并释放钾素的能力,这种能力可能与菌丝、有机酸、多糖的协同作用有关。     

不同基因型烤烟钾吸收特性差异及吸收机理

以富钾植物烟草为研究对象,烤烟基因型ND202、NC628、G28、NC628×ND202为材料,分析了不同基因型间根系特性及其对矿物钾活化能力的影响差异.结果表明： 根系对矿物钾活化总量越高,烤烟的钾积累量越高.ND202根系发达,富钾能力强,但受环境中钾含量影响较大;NC628根系矿钾活化能力较强,能够显著提高根际土壤钾有效性,但富钾能力较弱;杂交种NC628×ND202较母本具有较高的矿钾活化能力及耐低钾能力,较父本有较高的干物质积累量及富钾能力.因此,利用杂交培育高钾品种是有效的,选育高钾品种时,亲本不仅应具有较高的配合力,更应优先考虑其能否提高根际土壤钾的有效性.     

土壤中钾细菌的筛选及筛选底物加入量对其数量的影响

研究土壤中加入不同数量的钾长石粉后其解钾细菌数量的变化,同时初步筛选钾细菌,为进一步研究土壤中解钾细菌的分离、筛选及其鉴定提供参考。测试土壤中加入不同数量的钾长石粉后其解钾细菌数量,对结果进行比较分析;利用四苯硼钠法测试菌株解钾能力,并进行初步筛选。结果表明,按钾细菌数量由多到少的顺序,筛选底物加入量为0.2%0.1%0.4%空白对照;筛选菌株的解钾效率高于K01的共14株,高于K02的共9株。解钾效率最高的菌株5.15-2解钾效率为35.4%,较外购生产菌种K01高13倍,与本实验室保存菌种K02相比高3.6倍。     

土壤中解钾菌K02的筛选、鉴定及培养条件优化

解钾微生物是能够在土壤或纯培养条件下,将含钾矿物如长石、云母等不能被作物吸收利用的矿物态钾分解,并产生水溶性钾的微生物。利用以钾长石粉为唯一钾源的硅酸盐细菌选择性培养基,采用梯度稀释分离法平板划线对番茄土壤中的钾细菌进行筛选。利用原子吸收火焰分光光度法测定钾细菌培养液中可溶性钾的含量,筛选高效解钾菌株。通过形态观察和16S rDNA序列GenBank比对,同时利用clustalx和MEGA 4.0等相关软件构建系统进化树对解钾能力最强的菌株K02进行鉴定,初步鉴定该解钾菌为胶质类芽胞杆菌(Paenibacillus mucilaginosus);利用单因素试验法对K02菌株培养基组分及发酵条件进行优化,初步确定菌株K02最佳培养基组分以解钾复筛培养基为基础,其碳源、氮源及无机盐以可溶性淀粉1%、酵母膏0.2%、K_2HPO_40.05%为最佳;菌株K02最佳发酵条件:培养温度为30℃,培养时间为48 h,培养基装量为50 mL/250 mL,培养基初始pH值为7.5,接菌量为5%,这一结果为解钾菌肥的研制和生产提供参考。     

Effects of glyphosate on interspecific competition between Solidago canadensis and Imperata cylindrica

Aims The extensive use of herbicide to control invasive plants would change the relationship between alien and neighboring plants. In order to provide data for rational use of herbicide and a theoretical reference for further studies on the ecological effects of glyphosate, we explored the variation of the relationship between an invasive plant Solidago canadensis and a native plant Imperata cylindrica when they were sprayed glyphosate.
Methods A replacement series experiment was conducted from June to August 2016 in Wetland Ecosystem Research Station of Hangzhou Bay, State Forestry Administration, to examine the effects of glyphosate at seven concentration levels (0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8 mL·L^-1) on the growth and interspecific competition of S. canadensis and I. cylindrica.
Important findings (1) Glyphosate treatment significantly inhibited the growth of S. canadensis and I. cylindrica (p < 0.05). During the test, cumulative growth of height and leaf number of S. canadensis were apparently reduced with the increase of glyphosate concentration, but the leaf number of S. canadensis treated with 0.3- 1.5 mL·L^-1 glyphosate was re-growing with time, while the one treated with 1.8 mL·L^-1 was mostly dead. The withering rate of tiller and green leaf of I. cylindrica also significantly increased with the increase of glyphosate concentration, and the growth indices of this plant treated with 0.3-0.6 mL·L^-1 were also re-growing with time. (2) Glyphosate treatment significantly affected interspecific competition (p < 0.05), which diminished as the glyphosate concentration increased. (3) Interspecific competition has significant influence on the biomass allocation of S. canadensis (p < 0.05). When facing competition, S. canadensis would allocate more organic matter to root and thus increase the ratio of root to shoot. Competition only inhibited the tiller number and total biomass of I. cylindrica, but insignificantly affected its ratio of root to shoot. (4) The interaction between glyphosate treatment and S. canadensis-I. cylindrica interspecific relationship also significantly influenced the biomass of S. canadensis and I. cylindrica (p < 0.05), but insignificantly affected the root/shoot ratio of two plants. Different plants have different tolerance to glyphosate stress. Compared with native plant I. cylindrica, S. canadensis has stronger tolerance to glyphosate. Low-concentration glyphosate could decrease the competitive intensity between S. canadensis and I. cylindrica, which may disturb the structure and dynamics of plant communities.     

摩西斗管囊霉改善连作花生根际土壤的微环境

花生(Arachis hypogaea)长期连作导致土壤环境恶化, 严重影响产量和品质。丛枝菌根真菌(AMF)作为有益真菌能够与80%的陆生植物根系形成共生关系, 这种共生体能够改善植物根系微环境, 提高植物对营养物质的吸收和对逆境胁迫的抗性。为了探究AMF对花生连作土壤微环境的影响, 该研究通过对花生连作土壤接种和未接种摩西斗管囊霉(Funneliformis mosseae)试验, 在花生不同生长期检测根际土壤的酶活性、土壤矿物质含量、土壤微生物群落结构和多度的变化情况, 以及对连作花生产量和品质的影响。研究结果表明: 1)摩西斗管囊霉能够显著提高花生根际土壤蔗糖酶、脲酶、碱性磷酸酶和硝酸还原酶的活性; 2)摩西斗管囊霉显著增加花生连作土壤中全氮、全磷、全钾、速效磷和速效钾的含量; 3)摩西斗管囊霉显著降低土壤中有害真菌曲霉菌属(Aspergillus)的多度, 减少镰刀菌属(Fusarium)和赤霉菌属(Gibberella)的多度, 但是没有达到显著水平, 显著增加有益细菌放线菌Gaiella属的多度; 4)摩西斗管囊霉显著提高连作花生的产量, 增加籽仁中蛋白质、油酸和亚油酸的含量。因此, 摩西斗管囊霉能够改善连作花生根际土壤微生态环境, 增强连作土壤对致病菌的抵抗能力, 从而缓解连作障碍对花生根系的危害。     

Effects of nitrogen addition on soil respiration in shrublands in Mt. Dongling,Beijing, China

Aims Soil respiration from terrestrial ecosystems is an important component of terrestrial carbon budgets. Compared to forests, natural or semi-natural shrublands are mostly distributed in nutrient-poor sites, and usually considered to be relatively vulnerable to environmental changes. Increased nitrogen (N) input to ecosystems may remarkably influence soil respiration in shrublands. So far the effects of N deposition on shrubland soil respiration are poorly understood. The aim of this study is to investigate the soil respiration of Vitex negundo var. heterophylla and Spiraea salicifolia shrublands and their response to N deposition. Methods We carried out a N enrichment experiment in V. negundo var. heterophylla and S. salicifolia shrublands in Mt. Dongling, Beijing, with four N addition levels (N₀, control, 0; N₁, low N, 20 kg N·hm^-2·a^-1; N₂, medium N, 50 kg N·hm^-2·a^-1 and N₃, high N, 100 kg N·hm^-2·a^-1). Respiration was measured from 2012-2013 within all treatments.Important findings Under natural conditions, annual total and heterotrophic respiration were 5.91 and 4.23, 5.76 and 3.53 t C·hm^-2·a^-1 for the V. negundo var. heterophylla and S. salicifolia shrublands, respectively and both were not affected by short-term N addition. In both shrubland types, soil respiration rate exhibited significant exponential relationships with soil temperature. Temperature sensitivity (Q₁₀) of total soil respiration in V. negundo var. heterophylla and S. salicifolia shrublands ranged from 1.44 to 1.58 and 1.43 to 1.98, and Q₁₀ of heterotrophic soil respiration ranged from 1.38 to 2.11 and 1.49 to 1.88, respectively. Short-term N addition decreased only autotrophic respiration rate during the growing season, but had no significant effects on total and heterotrophic soil respiration in V. negundo var. heterophylla shrubland. In contrast, N addition enhanced the heterotrophic soil respiration rate and did not influence autotrophic and total soil respiration in S. salicifolia shrubland.     

Biomass allocation and carbon density of Sophora moorcroftiana shrublands in the middle reaches of Yarlung Zangbo River,Xizang, China

Aims The expansion of shrublands is considered as one of the key reasons leading to the increase of carbon density in terrestrial ecosystems in China. In the present study, our aims were to explore the biomass allocation and carbon density of Sophora moorcroftiana shrublands in Xizang.
Methods We sampled the biomass of S. moorcroftiana shrubs from 18 sites in the middle reaches of Yarlung Zangbo River, Xizang. Using concentrations of different organs, we estimated the carbon density of different layers in S. moorcroftiana shrublands.
Important findings The plant cover rather than biomass volume (the product of cover and height) provided the best fit for aboveground biomass. The average of the total biomass was 5.71 Mg·hm^-2, ranging from 2.32 to 8.96 Mg·hm^-2. The average biomass of shrub layer, the main component of shrub ecosystem, was 4.08 Mg·hm^-2, accounting for 71% of the total biomass. The belowground biomass of shrub and herb layers was 2.08 and 0.86 Mg·hm^-2, respectively, which was higher than the corresponding aboveground biomass. The average biomass carbon density was 2.48 Mg·hm^-2. Shrub vegetation in the eastern part of the middle reaches has lower carbon density than that in the western part. The relatively high biomass allocation to roots to increase water and nutrient undertake as well as physical support for plants is an important strategy of S. moorcroftiana to cope with the arid environment on the Qinghai-Xizang Plateau. Moreover, the lower carbon density in the eastern part of the middle reaches might be due to the dry environment resulted from high temperature and evapotranspiration and enhanced human activities at low altitudes. The continuous decrease of evapotranspiration under scenarios of future climate change may lead to increase in carbon density in S. moorcroftiana shrublands.     

Plant nutrient dynamics and stoichiometric homeostasis of invasive species Spartina alterniflora and native Cyperus malaccensis var. brevifolius in the Minjiang River estuarine wetlands

Aims Stoichiometric homeostasis is an important mechanism in maintaining ecosystem structure, function, and stability. The invasion of exotic species, Spartina alterniflora, has largely threatened the structure and function of native ecosystems in the Minjiang River estuarine wetland. However, how S. alterniflora invasion affect plant stoichiometric homeostasis is largely unknown. This could enhance our understanding on wetland ecosystem stability and expand the applications of ecological stoichiometry theory.
Methods Nitrogen (N) and phosphorus (P) contents of plant organs and soils in the S. alterniflora, Cyperus malaccensis var. brevifolius, and S. alterniflora-C. malaccensis var. brevifolius mixture were measured, and the homeostatic index (H) was calculated according to the stoichiometric homeostasis theory.
Important findings Our results showed that the invasion of S. alterniflora significantly increased soil N:P ratio (p < 0.05), but did not affect soil N or P contents. The N and P contents of leaf and stem were the highest for S. alterniflora, and those of the stem were the highest for C. malaccensis var. brevifolius. At the ecosystem level, the average of homeostatic index (H) of N (H_N, 25.31) was larger than those of P (H_P, 10.33) and N:P (H_N:P, 2.50). At the organ level, root H_N was significantly larger than stem H_N (p < 0.05) and sheath H_N:P was greater than root H_N:P (p < 0.05), while there was no significant difference for H_P among root, stem, leaf, and sheath (p > 0.05). As for species, root H_N of S. alterniflora was significantly larger than that of C. malaccensis var. brevifolius in the mixture community (p < 0.05). In the monoculture, stem H_N:P of S. alterniflora was significantly higher than that of C. malaccensis var. brevifolius (p < 0.05). Furthermore, root H_N, leaf H_N and sheath H_N of S. alterniflora in the mixed community was significantly larger than that of S. alterniflora in the monoculture (p < 0.05), suggesting that S. alterniflora invasions increased their stoichiometric homeostasis. Meanwhile, the stoichiometric homeostasis of invasive and native plants were influenced by multiple factors, such as nutrients, organs, vegetation, and invasion. However, larger homeostasis was found in S. alterniflora than in C. malaccensis var. brevifolius in some particular organs either in mixture or monoculture communities. Therefore, the successful invasion of S. alterniflora may result from higher homeostatic index than the native species, C. malaccensis var. brevifolius.     

青海地区解磷微生物的筛选及对小油菜生长的影响

为了筛选出能适应青海省冷凉气候环境的解磷菌株,以磷酸钙、卵磷脂、植酸为单一磷源,对胶冻样芽孢杆菌、巨大芽孢杆菌、蜡状芽孢杆菌、紫变异链霉菌、肉桂褐链霉菌、黄团孢链霉菌进行固体平板培养基初筛和液体培养基复筛,通过综合比较固体平板培养基中解磷圈的大小和液体培养基可溶性磷含量,初步筛选出解磷效果较好的3株解磷菌,分别为紫变异链霉菌、肉桂褐链霉菌和胶冻样芽孢杆菌。将这3株解磷菌制成液体菌剂,在9月冷凉气候下采用两种不同肥力土壤进行小油菜盆栽试验。结果表明:与对照相比,施加紫变异链霉菌剂后,高肥力耕地土的小油菜收获时株高、鲜重、根长、根重分别增加了35.5%、191.0%、26.2%、282.7%,植株磷吸收量、根际土壤全磷、速效磷分别增加了968.9%、5.1%、2.1%;低肥力自然土的小油菜收获时株高和鲜重分别增加了45.8%和61.3%,根长和根重分别减少了2.6%和4.4%,植株磷吸收量、根际土壤全磷、速效磷分别增加了91.5%、29.1%和213.7%。其他两种解磷菌剂效果不如紫变异链霉菌明显,表明紫变异链霉菌为适合青海地区冷凉气候环境的解磷菌株。     

Modeling the potential suitable habitat of Impatiens hainanensis,a limestone-endemic plant

模拟物种的潜在分布区是保护管理受威胁物种的重要手段。该研究对海南岛石灰岩特有种、濒危植物——海南凤仙花(Impatiens hainanensis)的潜在适宜生境分布进行预测, 旨在为海南凤仙花的有效保护及重引入工作提供基础的科学依据。研究基于海南凤仙花8个种群分布点和12个环境变量, 利用最大熵模型(MaxEnt)和GIS技术构建海南凤仙花适宜生境预测模型, 模拟了当前时期海南凤仙花在海南岛的潜在分布区; 同时基于5个实际分布数据和5个不存在数据, 采用受试者工作特征曲线下的面积(AUC)、Kappa系数、真实技巧统计值(TSS)及总体精度4个评估指标综合评价模型的预测精度。研究结果表明: 4个评估指标值均在0.9以上, 说明MaxEnt模型能够很好地预测海南凤仙花潜在适宜生境的分布。限制其分布的主要环境因子为坡度、最干季降水量、降水量季节性变异系数。当前, 海南凤仙花的最适宜生境占海南岛总面积的1.8%, 主要分布于白沙西部与南部、昌江中部和南部、东方东部、乐东东北部。海南凤仙花潜在适宜生境分布狭窄, 且破碎化严重, 迫切需要保护。因此建议: 收集海南凤仙花各种群种子, 建立种质资源库; 将东方天安乡、江边乡及乐东东北部(佳西保护区)等可能存在最适宜生境的地区, 作为今后野外深入调查的首选区域和重引入的重点区域。     

Nitrogen-fixing bacteria alleviates competition between arbuscular mycorrhizal fungi and Solidago canadensis for nutrients under nitrogen limitation

丛枝菌根真菌(AMF)能与大多数陆生植物的根系形成共生体, 有助于宿主植物吸收养分。但营养胁迫下, 根系微生物对AMF与宿主植物间关系的影响少见报道。该研究假设: 在营养极度匮乏(如氮胁迫)环境下, AMF与宿主植物可能产生营养竞争, 而固氮菌的介入能够缓解两者对营养的竞争关系。为了验证这一假设, 该文探究了加拿大一枝黄花(Solidago canadensis)生长受限的氮浓度, 并在氮受限条件下检验了AMF、加拿大一枝黄花及固氮菌三者间的关系。结果表明: 低氮处理明显抑制了加拿大一枝黄花的地上生物量和总生物量, 尤其以0.025 mmol·L^-1 N的氨态氮对加拿大一枝黄花的负影响更甚。在此氮浓度下, 单独添加AMF总体上都进一步抑制了加拿大一枝黄花的生长, 而固氮菌的添加在一定程度上提高了氮受限条件下AMF对宿主的根部侵染率及宿主植物生物量。这表明固氮菌能够缓和氮受限条件下AMF和加拿大一枝黄花间的营养竞争关系。研究结果加深了对外来植物在极度营养胁迫环境下与多种微生物互作的入侵机制的理解。     

Correlation between vein density and water use efficiency of Salix matsudana in Zhangye Wetland,China

Aims The correlation between vein density and water use efficiency (WUE) affects the balance between water supply and demand of plant leaves, which is significant for comprehending the ecological adaptation strategies of plants. The objective of this study was to study how Salix matsudana modulated vein density and WUE along a soil moisture gradient in Zhangye Wetland, China. Methods The study was conducted in floodplain wetland near Heihe River in Zhangye City, Gansu Province, China. Three sample plots, at a spatial interval of 70 m, were set up along a soil moisture gradient ordinally from the area near the water body to the wetland edge, plot I (69.23%), spot II (48.38%) and spot III (35.27%). Community traits were investigated by using diagonal method, and all individuals of S. matsudana were used for measurements of height and canopy. At each plot, 5 individuals of S. matsudana at 4 vertices and diagonal intersection were selected for measurements of vein density, WUE, net photosynthetic rate (P_n), transpiration rate (T_r), photosynthetically active radiation (PAR), saturated vapor pressure differences (VPD), specific leaf area, stomatal conductance (G_s) and intercellular CO₂ concentration (C_i). We used mathematical methods of correlation analysis and standardized major axis to investigate relationships between vein density and WUE. Important findings With decreasing soil moisture, the height, canopy, specific leaf area, G_s and C_i of S. matsudana decreased gradually, while the vein density, WUE, P_n, T_r, PAR and VPD increased gradually. The correlation between vein density and WUE was positive in all the three plots, but the relationship varied along the soil moisture plots gradient. There was a highly significant positive correlation (p < 0.01) between the vein density and WUE at plot I and III, whereas the correlation only reached a significant level (p < 0.05) at plot II; The correlation coefficient between vein density and WUE is significantly smaller than 1 at plot I (p < 0.05), while the correlation coefficient is significant greater than 1 at plot II and III (p < 0.05). We can conclude that varied relationships between vein density and WUE of S. matsudana along a soil moisture gradient could reflect plant acclimation.     

Distribution pattern and influencing factors of soil salinity at Tamarix cones in the Taklimakan Desert

柽柳(Tamarix chinensis)沙包是塔克拉玛干沙漠特殊的生物地貌景观, 对维持区域生态环境的稳定具有极其重要的作用。该研究采用野外调查与室内分析相结合的方法, 选取且末、阿拉尔、策勒、塔中4个典型区域的柽柳沙包为研究对象, 对柽柳沙包0-500 cm土壤垂直剖面进行采样, 测定土壤pH值、枯落物含量、电导率及HCO₃ ^-、Cl ^-、SO₄ ^2-、Ca ²⁺、Mg ²⁺、K ⁺、Na ⁺含量, 分析柽柳沙包中土壤盐分的空间变化规律及其影响因素。结果表明: 1)从且末、阿拉尔、策勒到塔中, 土壤pH值总体呈升高趋势, 土壤电导率及Na ⁺、Ca ²⁺、Mg ²⁺、SO₄ ^2-含量总体呈降低趋势, K ⁺、Cl ^-、HCO₃ ^-含量没有明显的变化规律。2)盐分在4个样区的垂直分布主要表现为: 且末和策勒样区柽柳沙包的土壤盐分呈表层聚集现象; 阿拉尔和塔中样区柽柳沙包的土壤盐分呈深层聚集现象。随着土层深度的增加, 土壤pH值总体呈升高的趋势, 土壤枯落物含量总体呈降低趋势; 土壤电导率在且末和策勒样区总体呈降低趋势, 阿拉尔样区呈先降低后升高再降低的变化趋势, 而塔中样区呈先升高后降低再升高的变化趋势。3)根据相关性分析和主成分分析, 且末样区土壤枯落物含量、SO₄ ^2-、Na ⁺、K ⁺为影响土壤盐分含量的主要因子, 且土壤盐分以硫酸盐为主; 阿拉尔样区影响土壤盐分组成的主要因子为Cl ^-、Na ⁺; 策勒样区为Cl ^-、K ⁺、Na ⁺; 塔中样区为Cl ^-、Na ⁺、Ca ²⁺、SO₄ ^2-, 且土壤盐分均以氯化物为主。综合分析表明, 不同区域柽柳沙包中土壤盐分存在空间变异性, 柽柳沙包土壤盐分的变化与干旱沙漠地区强烈的蒸发作用、地表风蚀强度、地下水埋深、土壤中枯落物及柽柳的生物积盐效应等因素密切相关, 是影响不同区域土壤盐分分布的关键因子。