Effects of arbuscular mycorrhizal fungi on photosynthesis,carbon content,and calorific value of black locust seedlings

Arbuscular mycorrhizal fungi (AMF) form symbioses with many plants. Black locust (Robinia pseudoacacia L.) is an important energy tree species that can associate with AMF. We investigated the effects of AMF (Rhizophagus irregularis and Glomus versiforme) on the growth, gas exchange, chlorophyll (Chl) fluorescence, carbon content, and calorific value of black locust seedlings in the greenhouse. The total biomass of the arbuscular mycorrhizal (AM) seedlings was 4 times greater than that of the nonmycorrhizal (NM) seedlings. AMF greatly promoted the photosynthesis of black locust seedlings. AM seedlings had a significantly greater leaf area, higher carboxylation efficiency, Chl content, and net photosynthetic rate (P _N) than NM seedlings. AMF also significantly increased the effective photochemical efficiency of PSII and significantly enhanced the carbon content and calorific value of black locust seedlings. Seedlings inoculated with G. versiforme had the largest leaf area and highest biomass, Chl content, P _N, and calorific value.     

AM真菌控制蚕豆枯萎病发生的根际微生物效应

在温室盆栽条件下,研究了接种尖孢镰刀菌蚕豆专化型和丛枝菌根(AM)真菌(摩西球囊霉Gm、扭形球囊霉Gt、根内球囊霉Gi及幼套球囊霉Ge)对灭菌连作土壤中蚕豆幼苗生长、枯萎病发生、根际镰刀菌数量和微生物代谢功能多样性的影响.结果表明: 接种AM真菌能显著增加蚕豆幼苗地上部和地下部鲜质量;接种Gm、Gt、Gi和Ge真菌使蚕豆枯萎病病情指数分别显著降低94.0%、60.0%、64.0%和94.0%,使蚕豆根际镰刀菌数量分别显著降低98.6%、74.3%、77.8%和90.4%,以Gm和Ge真菌对蚕豆枯萎病的抑制效应最好.接种Gm、Gt和Ge显著提高了根际微生物对糖类(CH)、氨基酸类(AA)、羧酸类(CA)和酚酸类(PA)碳源的利用,使蚕豆根际微生物的AWCD值分别显著提高34.4%、31.5%和50.8%;而接种Gi对AA、CA、PA类碳源利用和AWCD值均无显著影响,使微生物对CH类碳源的利用显著降低59.3%.主成分和相关分析表明, 接种AM真菌明显改变了蚕豆根际微生物的群落结构.接种Gt真菌提高了蚕豆根际微生物对AA类碳源(β-甲基-D-葡萄糖苷、D-半乳糖酸-γ-内酯、D-甘露醇、N-乙酰基-D-葡萄糖胺、D-纤维二糖)和CA类碳源(D-半乳糖醛酸)的利用,而接种Gi真菌降低了微生物对以上碳源的利用;接种Gm和Ge真菌提高了根际微生物对L-精氨酸和4-羟基苯甲酸的利用.表明糖类和羧酸类是接种Gt真菌后蚕豆根际土壤微生物利用的主要碳源, 氨基酸和酚酸类是接种Gm和Ge后蚕豆根际土壤微生物利用的主要碳源.接种AM真菌显著提高了蚕豆根际微生物的活性,改变了微生物群落结构并抑制病原菌的增殖,是AM真菌减轻了蚕豆枯萎病的发生的重要原因.不同AM真菌减轻了蚕豆枯萎病的发生与其改变微生物的碳源利用密切相关.     

混合接种球孢白僵菌与摩西球囊霉对烟草促生抗逆影响

利用球孢白僵菌Beauveria bassiana与摩西球囊霉菌Glomus mosseae以单独和混合接种的方式在烟草Nicotiana tabacum苗期进行接种处理,检测烟草苗期和成熟期的农艺性状和生理特性。结果表明：在育苗期,混合接种处理烟苗具有最大的叶长和最大叶宽,与对照相比提高了30.27%和42.98%,球孢白僵菌处理组生物量最大,AM真菌处理组烟草株高最高;在成熟期,混合接种处理组烟草的株高、最大叶长、最大叶宽、茎围、生物量等指标均优于单接种处理,且过氧化氢酶（CAT）、超氧化物歧化酶（SOD）、过氧化物酶（POD）等抗氧化酶活性最高,丙二醛（MDA）含量最低。球孢白僵菌和AM真菌可协同提高烟草生长和抗逆能力。     

基于超声清洗的树木叶面颗粒物粒径分布与吸滞效率研究——以银杏和油松为例

明确在常规叶片清洗方法(泡洗或泡洗+刷洗)上增加超声清洗对叶面各径级颗粒物滞纳量定量评估的影响, 并在此基础上研究叶面颗粒物的粒径分布和吸滞效率, 可进一步提高城市树木大气颗粒物吸滞能力的定量评估精度。该文以城市森林建设常用阔叶树种银杏(Ginkgo biloba)和针叶树种油松(Pinus tabuliformis)为研究对象, 于雨后(降水量>15 mm) 4天(短滞尘时长)和14天(长滞尘时长)分别采集叶样, 并依次对其进行泡洗(WC)、刷洗(BC)、超声清洗(UC)等洗脱程序, 然后对每个清洗步骤下叶片洗脱液中颗粒物的质量和粒径分布进行测试, 并依此估算叶片各径级颗粒物的吸滞效率。结果表明, 以“泡洗+刷洗+超声清洗”清洗流程的测试结果为参照, 若只对叶片进行泡洗, 则银杏和油松对大气颗粒物(PM₁, 粒径d ≤1 µm)、PM_2.5 (d ≤ 2.5 µm)、PM₅ (d ≤ 5 µm)、PM₁₀ (d ≤ 10 µm)吸滞量会分别被低估约一半(54%、53%、53%和53%)和40% (42%、42%、42%和42%); 若只进行“泡洗+刷洗”, 则银杏和油松对相应径级颗粒物的吸滞量仍会分别被低估约15% (17%、16%、15%和15%)和20% (21%、20%、20%和20%)。油松叶面颗粒物粒径分布呈双峰曲线, 而银杏叶面颗粒物粒径则呈单峰分布, 且银杏叶面颗粒物平均粒径在短、长滞尘时长下均大于油松。油松叶片对PM₁、PM_2.5、PM₅、PM₁₀和总悬浮颗粒物的吸滞效率分别为8.96、23.92、23.96、23.96和23.96 mg·m^-2·d^-1, 分别比银杏叶片高112%、73%、34%、37%和42%。     

接种AM真菌对喜树幼苗生长及光合特性的影响

 喜树(Camptotheca acuminata)是我国特有的多年生亚热带落叶阔叶树种, 因其次生代谢产物喜树碱具有良好的抗肿瘤活性而备受关注。通过温室盆栽接种试验, 观察了3属6种丛枝菌根(AM)真菌木薯球囊霉(Glomus manihot)、地表球囊霉(G. versiforme)、透光球囊霉(G. diaphanum)、蜜色无梗囊霉(Acaulospora mellea)、光壁无梗囊霉(A. laevis)和弯丝硬囊霉(Sclerocystis sinuosa)对喜树幼苗生长及光合特性的影响。结果表明, 除地表球囊霉外, 其余菌根幼苗生物量显著高于无菌根幼苗, 蜜色无梗囊霉、弯丝硬囊霉和透光球囊霉的菌根幼苗生物量分别达到无菌根幼苗的1.6倍、1.4倍和1.3倍。与无菌根幼苗相比, 蜜色无梗囊霉菌根幼苗叶片的净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)均有显著提高, 而胞间CO₂浓度(C_i)与气孔限制值(L_s)则变化不明显。接种透光球囊霉、蜜色无梗囊霉、光壁无梗囊霉和弯丝硬囊霉的喜树幼苗叶片叶绿素a含量、总叶绿素含量、叶绿素a/b和类胡萝卜素含量均显著高于无菌根幼苗, 而叶绿素b含量只有木薯球囊霉和弯丝硬囊霉菌根幼苗显著高于无菌根幼苗。接种AM真菌对喜树幼苗叶片叶绿素荧光参数影响较小, 只有透光球囊霉菌根幼苗叶片的最大光能转换效率(F_v/F_m)显著高于无菌根幼苗, 接种木薯球囊霉和弯丝硬囊霉的喜树幼苗的PSⅡ有效光化学量子产量(EQY)显著高于无菌根幼苗, 弯丝硬囊霉菌根幼苗的光化学淬灭(qP)显著高于无菌根幼苗, 非光化学淬灭(NPQ)则显著低于无菌根幼苗。     

丛枝菌根真菌延长百合切花观赏期作用机制的初步研究

为初步探究丛枝菌根(arbuscularmycorrhizal,AM)真菌促进百合生长并延长瓶插过程中切花观赏期的作用机制,于温室盆栽条件下对百合Lilium brownii进行摩西斗管囊霉Funneliformis mosseae和变形球囊霉Glomusversiforme单一接种或者共同双接种处理。结果表明,共同接种F.mosseae和G.versiforme的百合地上部干重和地下部干重均显著高于不接种对照,分别增加了60%和58%。与不接种对照相比,接种F. mosseae和G. versiforme处理的百合根尖数、根系长度、分叉数、表面积和根系体积分别比对照增加123%、128%、182%、118%和232%。切花瓶插期间,接种AM真菌处理的百合切花水分平衡值和鲜重变化率显著高于对照处理;乙烯释放速率和呼吸速率显著低于对照,瓶插5d时达到乙烯峰值5.4μL/*g·h (FW)+,共同接种F. mosseae和G. versiforme处理的百合切花乙烯释放速率比对照降低30%;呼吸速率则在瓶插1d时达到峰值0.7μL/*g·h (FW)+,共同接种比对照降低37%;百合花瓣内超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性、可溶性糖含量和可溶性蛋白含量比对照分别提高19%、32%、52%和26%。百合花瓣内N、P、K、Mg、Ca、Fe和Zn含量均显著高于不接种对照处理,Mn和Cr含量则低于对照;共同接种处理的百合瓶插寿命增加了3d,最佳观赏时间比对照延长2d。结论认为共同接种F. mosseae和G. versiforme处理更加有效地改善切花花枝的水分平衡、营养状况与生理代谢,控制衰老激素的合成,从而延长百合切花的瓶插寿命和最佳观赏期。     

Effects of inoculation with arbuscular mycorrhizal fungi on photosynthetic physiology in females and males of Populus deltoides exposed to cadmium pollution

Aims Populus deltoides is an important plantation tree species in the middle and lower reaches of the Yangtze River and in Huai River Plain. The extensively cultivated varieties are consisted of both females and males of P. deltoides. The objective of this paper was to characterize the difference in cadmium (Cd) tolerance between the sexes and the effects of symbiosis with Rhizophagus intraradices on their Cd tolerance.
Methods The experiment was carried out under semi-controlled conditions in a natural light greenhouse, protected from rain. Rhizophagus intraradices was inoculated on roots of both females and males when transplanting to a sand culture substrate. After one month, half of cuttings were exposed to Cd pollution (10 mg·kg^-1). All cuttings were irrigated with sterile water to avoid infection by other microorganism. About three months later, the gas exchange rate, net photosynthesis rate (P_n)-intercellular CO₂ concentration (C_i) curve, chlorophyll fluorescence, osmotic adjustment and phytohormone content of both females and males of P. deltoides were measured.
Important findings Our main results are as follows: (1) when compared to the controls, decreases in P_n, stomatal conductance, C_i, transpiration rate, maximum photochemical efficiency of photosystem II (PSII), effective quantum yield of PSII, photo-chemical quenching coefficient, maximum rate of carboxylation of Rubisco, photosynthetically active radiation-saturated rate of electron transport and rate of triose phosphate utilization to a different degree in both sexes of P. deltoides under Cd pollution were found, and females exhibited a greater decrease in such parameters than males. Rhizophagus intraradices inoculation mitigated the toxic effect of Cd on such parameters to a different degree in females, not in males. (2) Under Cd pollution, there was an increase in proline content in both sexes when compared to the controls. A further increase in proline content occurred in females, not in males, when inoculated with R. intraradices. (3) When compared to the controls, there was a decrease in indoleacetic acid, but an increase in abscisic acid in leaves of both sexes when exposed to Cd pollution. The amplitude changed in both phytohormones in females was greater than that in males. Rhizophagus intraradices inoculation was helpful for recovery of phytohormone balance in females, which was not observed in males. Therefore, our results indicated that (1) there were a greater negative effect exerted by Cd pollution on gas exchange rate, carbon fixation capacity and phytohormone balance and a more impairment of photosynthetic apparatus in females when compared to males, showing a less tolerance to stress conditions in females; (2) Rhizophagus intraradices inoculation could enhance the osmotic adjustment capacity in females, thus mitigate the negative effect of Cd stress on ability of carbon fixation and phytohormone balance in females. However, such positive effects derived from R. intraradices symbiosis were not observed in males.     

Effects of light intensity variation on nitrogen and phosphorus contents,allocation and limitation in five shade-enduring plants

Aims To enhance the understanding on nitrogen (N) and phosphorus (P) physiological responses to different light environments in shade-enduring plants and provide references to improve the stand structure and ecosystem functions of plantation forests.Methods We selected seedlings of five shade-enduring species with high ecological and economic value in subtropical area of China to study the effects of light intensity on leaf N and P contents, allocation and nutrient limitation in shade-enduring plants. A light intensity gradient of five different levels was set to simulate the varying understory light environment.Important findings With decreasing light intensity, the total biomass and total N and P accumulation of five shade-enduring plants all showed a decreasing trend, but N, P contents in different organs increased. Among them, Gardenia jasminoides (GJ) had the highest while Illicium henryi (IH) had the lowest N content; The P contents of Quercus phillyraeoides (QP) and GJ were significantly higher than Elaeocarpus sylvestris (ES), Ardisia crenata (AC) and IH. QP and GJ had the highest N, P contents under extremely low light intensity (6% natural light intensity) condition (LIC), while AC and IH had the highest N and P contents in low (15% natural light intensity) and moderate (33% and 52% natural light intensity) LIC. ES demanded differently for LIC on N and P, which were 52% and 6% natural light intensity, respectively. N and P allocation of ES, AC and IH followed leaf > root > stem, but for QP and GJ were root > leaf > stem. Decreasing LIC significantly affected N and P allocation. N content variations shown good consistency among different organs under higher LIC (100% natural light intensity) while distinct variability under lower LIC (15% and 6% natural light intensity) in all five species. Phosphorus contents exhibited good consistency in IH, QP and GJ but varied in ES and AC. Decreasing LIC significantly affected organ N/P ratios of shade-enduring plants, but the fundamental growth restriction patterns remained. Light intensity variation and tree species co-regulated N, P utilization and allocation in shade-enduring plants, and then affected the total biomass and total N, P accumulation, which might result from the change of N and P utilization strategy. Therefore, light intensity preference and N, P nutrient balances in shade-enduring plants should be taken into account when constructing multiple layer and uneven-aged forests.     

入侵豚草与本地植物竞争对丛枝菌根真菌多样性的影响

外来植物入侵常引起入侵地丛枝菌根真菌（arbuscular mycorrhizal fungi,AMF）多样性的变化,但AMF多样性的变化与入侵域本地植物种类相关性目前尚不清楚。本研究采用野外同质园试验研究豚草与不同本地植物竞争时对AMF多样性的影响。本试验共设入侵豚草单种、本地植物狗尾草Setaria viridis单种、藜 Chenopodium album单种、黄香草木犀Melilotus officinalis单种、豚草和狗尾草混种、豚草和藜混种、豚草和黄香草木犀混种以及裸土（无任何植物生长）对照8个处理。采集根区土样后分离、鉴定AMF,分析植株生物量和AMF物种多样性变化间的关系。结果表明,对豚草而言,单种处理中生物量均高于混种处理;豚草分别与3种本地植物竞争时,与黄香草木犀混种中豚草竞争能力最强,而与藜混种中竞争能力最弱。豚草分别与3种本地植物混种时土壤中AMF种丰度和香农-威纳指数分别显著高于豚草单种和本地植物单种,其中豚草与藜混种中AMF的种丰度和香农-威纳指数最高,与狗尾草混种中AMF的种丰度和香农-威纳指数最低,而豚草分别与3种本地植物混种处理中孢子密度显著低于本地植物单种（豚草与黄香草木犀混种除外）。豚草单种、狗尾草单种、藜单种、豚草分别与狗尾草和藜混种4个处理中AMF优势种均为网状球囊霉Glomus reticulatum和缩隔球囊霉Septoglomus constrictum;黄香草木犀单种中优势种是网状球囊霉、缩隔球囊霉和根内根孢囊霉Rhizophagus Intraradices,豚草与黄香草木犀混种中优势种是网状球囊霉和根内根孢囊霉;狗尾草单种、豚草与狗尾草混种和豚草与藜混种3个处理的特有种分别是木薯根孢囊霉Rhizoglomus manihotis、近明球囊霉Claroideoglomus claroideum和美丽盾巨孢囊霉Scutellospora calospora。狗尾草单种生物量与孢子密度呈显著正相关,豚草与狗尾草混种中豚草的生物量与均匀度呈显著负相关,豚草与黄香草木犀混种中豚草的生物量与孢子密度呈显著正相关,与香农威纳指数呈显著负相关。综上可知,豚草与本地植物竞争对AMF多样性的影响具有异质性,这与本地植物种类密切相关。     

Estimation of biomass allocation and carbon density of Rhododendron simsii shrubland in the subtropical mountainous areas of China

Aims As an important potential carbon sink, shrubland ecosystem plays a vital role in global carbon balance and climate regulation. Our objectives were to derive appropriate regression models for shrub biomass estimation, and to reveal the biomass allocation pattern and carbon density in Rhododendron simsii shrubland.
Methods We conducted investigations in 27 plots, and developed biomass regression models for shrub species to estimate shrub biomass. The biomass of herb and litterfall were obtained through harvesting. Plant samples were collected from each plot to measure carbon content in different organs.
Important findings The results showed that the power and linear models were the most appropriate equation forms. The D and D²H (where D was the basal diameter (cm) and H was the shrub height (m)) were good predictors for organ biomass and total biomass of shrubs. All of the biomass models reached extremely significant level, and could be used to estimate shrub biomass with high accuracy. It was more difficult to predict leaf and annual branch biomass than stem biomass, because leaf and annual branch were susceptible to herbivores and inter-plant competition. The mean biomass of the shrub layer was 20.78 Mg·hm^-2, in which Rhododendron simsii and Symplocos paniculata biomass accounted for 93.63%. Influenced by both environment and species characteristics, the biomass of the shrub layer organs was in the order of stem > root > leaf > annual branch. The root:shoot ratio of the shrub layer was 0.32, which was less than other shrubs in subtropical regions. The relative higher aboveground biomass allocation reflected the adaptation of plants to the warm and humid environment for more photosynthesis. The mean total community biomass was 26.26 Mg·hm^-2, in which shrub layer, herb layer and litter layer accounted for 79.14%, 7.62% and 13.25%, respectively. Litter biomass was relatively high, which suggested that this community had high nutrient return. There were significant correlations among aboveground biomass, belowground biomass and total biomass of shrub layer and herb layer. The mean biomass carbon density of the community was 11.70 Mg·hm^-2 and the carbon content ratio was 44.55%. The carbon density was usually obtained using the conversion coefficient of 0.5 in previous studies, which could overestimate carbon density by 12.22%.     

Arbuscular mycorrhizal fungi enhanced the growth,photosynthesis, and calorific value of black locust under salt stress

Saline soils spread wildly in the world, therefore it is important to develop salt-tolerant crops. We carried out a pot study in order to determine effects of arbuscular mycorrhizal fungi (AMF) (Rhizophagus irregularis and Glomus versiforme) in black locust seedlings under salt (NaCl) stress. The results showed that AMF enhanced in seedlings their growth, photosynthetic ability, carbon content, and calorific value. Under salt stress, the biomass of the seedlings with R. irregularis or G. versiforme were greater by 151 and 100%, respectively, while a leaf area increased by 197 and 151%, respectively. The seedlings colonized by R. irregularis exhibited a higher chlorophyll content, net photosynthetic rate, intercellular CO₂ concentration, stomatal conductance, and transpiration rate than that of the nonmycorrhizal seedlings or those colonized by G. versiforme. Both R. irregularis and G. versiforme significantly enhanced a carbon content, calorific value, carbon, and energy accumulations of black locust under conditions of 0 or 1.5 g(NaCl) kg^–1(growth substrate). Our results suggested that AMF alleviated salt stress and improved the growth of black locust.     

Arbuscular mycorrhiza improves plant adaptation to phosphorus deficiency through regulating the expression of genes relevant to carbon and phosphorus metabolism

Aims Arbuscular mycorrhizal (AM) symbiosis plays an important role in plant adaptation to phosphorus (P) deficiency. The mycorrhizal fungi can directly regulate P stress response of the host plants, and can also indirectly influence neighbor plants via AM exudates. This study aimed to reveal the regulation mechanisms of plant response to P deficiency by AM associations. Methods In a compartmentation cultivation experiment with Zea mays ‘B73’ and AM fungus Rhizophagus irregularis ‘DAOM197198’, we investigated mycorrhizal effects on plant P nutrition and the expression of plant and fungal genes related to P and carbon (C) metabolisms under both low P (10 mg?kg^-1) and high P (100 mg?kg^-1) conditions. The cultivation system consisted of three compartments, namely donor compartment, buffer compartment and receiver compartment divided by two pieces of microporous filters with pore size of 0.45 μm. Maize plant in donor compartment inoculated with AM fungus served as a source of AM exudates. The microporous filters could restrict the development of extraradical mycelium of AM fungi, but allow diffusion of AM exudates. Real-time PCR was performed to quantify the gene expression levels both in maize plants and AM fungi. Important findings The experimental results indicated that under low P conditions mycorrhizal colonization increased plant dry weight and P concentration in donor plants, and up-regulated plant genes encoding P transporters Pht1;2, Pht1;6, phosphoenolpiruvate carboxylase (PEPC), inorganic pyrophosphatase (TC289), glycerol-3-phosphate transporter (G3PT) and malate synthase (MAS1). The expression of AM fungal genes encoding P transporter (GiPT), GlcNAc transporter (NGT1), GlcNAc kinase (HXK1b), GlcNAc phosphomutase (AGM1), UDP GlcNAc pyrophosphorylase (UAP1), chitin synthase (CHS1), GlcNAc-6-phosphate deacetylase (DAC1) and glucosamine-6-phosphate isomerase (NAG1) was significantly higher under low P conditions compared with high P conditions. However, for the receiver plants, plant dry mass and P concentration were only significantly increased by higher P addition, while inoculation treatment significantly up-regulated the expression of P transporter genes Pht1;2 and Pht1;6, C metabolism related genes G3PT, PEPC, TC289 and MAS1. The study proved that AM exudates could potentially stimulate plant response to P deficiency by regulating functional genes relevant to P and C metabolisms in the mycorrhizal associations.     

不同基质中番茄菌根苗的培育及其抗南方根结线虫的效果

根结线虫病是番茄主要的土传病害,特别是保护地长期种植会加重病害的发生。接种丛枝菌根真菌（arbuscular mycorrhizal fungi,AMF）能提高植物抗根结线虫的能力,促进植株生长发育,减轻病害。本试验旨在评价常用基质配合施用一种生物有机肥对番茄苗生长和菌根定殖的影响,以获得菌根发育良好且生长健壮的菌根苗,并通过盆栽实验验证菌根苗移栽于大棚连作土壤中对南方根结线虫的防治效果。结果表明,栽培于商业基质的番茄苗的株高、茎粗、地上部及根系干重和壮苗指数均显著高于草炭蛭石混合基质的番茄苗;草炭蛭石混合基质中施加生物有机肥能促进番茄苗的生长,但是显著抑制根内根孢囊霉Rhizophagus intraradices的侵染。草炭蛭石混合基质在培养过程中施加适量Hoagland营养液使番茄苗生长发育较好且根内根孢囊霉R. intraradices侵染率达到71%;商业基质培养的番茄苗壮苗指数更高,但侵染率较低（44%）。在草炭蛭石混合基质中接种变形球囊霉Glomus versiforme和根内根孢囊霉R. intraradices及其混合菌种培育的番茄苗对南方根结线虫Meloidogyne incognita的侵染和繁殖均表现出一定的抑制作用。按照单位重量根系进行统计,混合菌种显著降低了根结线虫的根结和卵块数量（分别降低了22.8%和23.5%）。本研究结果表明番茄菌根苗在草炭蛭石混合基质中AMF发育状况优于常用商业基质,在菌根应用中可优先选择;相对于单一接种AMF,混合接种的菌根化苗对南方根结线虫病害的抑制作用更好。     

玉米秸秆还田对土壤丛枝菌根真菌群落的影响

为揭示农业管理活动对土壤丛枝菌根(AM)真菌的影响机制,基于Illumina Miseq高通量测序平台以及脂肪酸指纹图谱方法,研究了连续4年玉米秸秆还田后,AM真菌群落组成、AM真菌生物量及其与土壤环境因子间的相互关系.结果表明:所获得的2430个AM真菌OTUs从门到种依次分类,共分为1门、3纲、4目、8科、10属、143种,但不同处理间AM真菌群落丰富度(Chao1指数和ACE指数)、多样性(Shannon、Simpson多样性指数)没有显著差异.AM真菌中类球囊霉属、球囊霉属为优势属.随秸秆还田量的增加,球囊霉属丰度降低;3000、9000 kg·hm^-2秸秆还田量下,类球囊霉属、无梗囊霉属的丰度与对照(0 kg·hm^-2)间差异达极显著水平;原囊霉属、类球囊霉属、球囊霉属在3000 kg·hm^-2秸秆还田量下与对照间差异显著,非度量多维尺度(NMDS)分析表明,9000、12000 kg·hm^-2的秸秆还田量下土壤AM真菌β多样性与对照间聚集度较其他处理相差较远,秸秆还田量对AM真菌β多样性的影响显著.多元分析结果能在累积变量82.8%上揭示土壤主要理化性状与AM真菌丰富度、多样性的空间变化关系.土壤全氮、碱解氮是影响以磷脂脂肪酸表征的土壤主要微生物类群生物量以及以中性脂肪酸表征的AM真菌生物量的主要因子.持续玉米秸秆还田改变了AM真菌属水平上的分类学组成;随秸秆还田量的增加,AM真菌特有的微生物种类减少,AM真菌群落组成间的相似度下降;秸秆还田增加了土壤AM真菌生物量及其占土壤微生物总生物量的比例.     

褐环乳牛肝菌对樟子松生长的调控——影响激素和代谢产物含量

为了进一步探究褐环乳牛肝菌对樟子松苗木生长的促进机制,利用生物化学和植物生理学等研究方法,在前期研究基础上对2年生沙地樟子松苗木施加褐环乳牛肝菌液体菌剂,并在2个月后对苗木各部分生长状态、生长相关激素、抗逆性代谢产物进行检测。结果表明：褐环乳牛肝菌可以通过升高樟子松IAA和GA含量促进樟子松苗木的生长。其中,对樟子松根系中IAA含量影响最为显著,接菌苗木根中IAA含量比未接菌苗木根中IAA含量高85%以上;与此结果相反,褐环乳牛肝菌可以降低樟子松苗木ABA含量,通过ABA含量变化调控IAA含量,进而调控根系的生长;除此之外,褐环乳牛肝菌可以调控樟子松苗木甜菜碱和黄酮化合物的含量。未接菌苗木的甜菜碱在根、茎、叶中的含量分别比接菌苗木高46%、26%和23%,说明接菌苗木在受环境的影响方面相较于未接菌苗木低。接菌处理可以显著提高樟子松苗木根部黄酮化合物含量。本研究结果可以为今后进一步研究提供数据借鉴,同时也可以为辽西半干旱地区森林健康调控与褐环乳牛肝菌科学应用于当地造林提供科学依据。     

Carbon storage,spatial distribution and the influence factors in Tianshan forests

Aims
Accurate estimation of carbon density and storage is among the key challenges in evaluating ecosystem carbon sink potentials for reducing atmospheric CO₂ concentration. It is also important for developing future conservation strategies and sustainable practices. Our objectives were to estimate the ecosystem carbon density and storage of Picea schrenkiana forests in Tianshan region of Xinjiang, and to analyze the spatial distribution and influencing factors.
Methods
Based on field measurements, the forest resource inventories, and laboratory analyses, we studied the carbon storage, its spatial distribution, and the potential influencing factors in Picea schrenkiana forest of Tianshan. Field surveys of 70 sites, with 800 m² (28.3 m × 28.3 m) for plot size, was conducted in 2011 for quantifying arbor biomass (leaf, branch, trunk and root), grass and litterfall biomass, soil bulk density, and other laboratory analyses of vegetation carbon content, soil organic carbon content, etc.
Important findings
The carbon content of the leaf, branch, trunk and root of Picea schrenkiana is varied from 46.56% to 52.22%. The vegetation carbon content of arbor and the herbatious/litterfall layer was 49% and 42%, respectively. The forest biomass of Picea schrenkiana was 187.98 Mg·hm^-2, with 98.93% found in the arbor layer. The biomass in all layers was in the order of trunk (109.81 Mg·hm^-2) > root (39.79 Mg·hm^-2) > branch (23.62 Mg·hm^-2) > leaf (12.76 Mg·hm^-2). From the age-group point of view, the highest and the lowest biomass was found at the mature forest (228.74 Mg·hm^-2) and young forest (146.77 Mg·hm^-2), respectively. The carbon density and storage were 544.57 Mg·hm^-2 and 290.84 Tg C, with vegetation portion of 92.57 Mg·hm^-2 and 53.14 Tg C, and soil portion of 452.00 Mg·hm^-2 and 237.70 Tg C, respectively. The spatial distribution of carbon density and storage appeared higher in the western areas than those in the eastern regions. In the western Tianshan Mountains (e.g., Ili district), carbon density was the highest, whereas the central Tianshan Mountains (e.g., Manas County, Fukang City, Qitai County) also had high carbon density. In the eastern Tianshan Mountains (e.g., Hami City), it was low. This distribution seemed consistent with the changes in environmental conditions. The primary causes of carbon density difference might be a combined effects of multiple environmental factors such as terrain, precipitation, temperature, and soil.     

Effects of mycorrhizal colonization on biomass production and nitrogen fixation of black locust (Robinia pseudoacacia) seedlings grown under elevated atmospheric carbon dioxide

Interactive effects of elevated atmospheric CO₂ and arbuscular mycorrhizal (AM) fungi on biomass production and N₂ fixation were investigated using black locust ( Robinia pseudoacacia ). Seedlings were grown in growth chambers maintained at either 350 μmol mol⁻¹ or 710 μmol mol⁻¹ CO₂. Seedlings were inoculated with Rhizobium spp. and were grown with or without AM fungi. The ¹⁵N isotope dilution method was used to determine N source partitioning between N₂ fixation and inorganic fertilizer uptake. Elevated atmospheric CO₂ significantly increased the percentage of fine roots that were colonized by AM fungi. Mycorrhizal seedlings grown under elevated CO₂ had the greatest overall plant biomass production, nodulation, N and P content, and root N absorption. Additionally, elevated CO₂ levels enhanced nodule and root mass production, as well as N₂ fixation rates, of non- mycorrhizal seedlings. However, the relative response of biomass production to CO₂ enrichment was greater in non-mycorrhizal seedlings than in mycorrhizal seedlings. This study provides strong evidence that arbuscular mycorrhizal fungi play an important role in the extent to which plant nutrition of symbiotic N₂-fixing tree species is affected by enriched atmospheric CO₂.     

Response and correlation of above- and below-ground functional traits of Leymus chinensis to nitrogen and phosphorus additions

AimsLeymus chinensis is a constructive and dominant species in typical steppe of northern China. The structure and functions of L. chinensis grassland ecosystem has been degenerated seriously due to long-term overgrazing in recent decades. As an effective measure to restore the degraded grasslands, the effects of nutrient addition on plant growth and ecosystem structure and functioning have been paid more attention in manipulation experimental research. The effects of nutrient addition, especially P addition on the above- and below-ground functional traits of L. chinensis have rarely been studied; particularly the underpinning mechanisms remain unclear. Our objective is to examine the responses and adaptive mechanisms of L. chinensis to different levels of N and P additions. MethodsWe conducted a culture experiment in the greenhouse, with three levels of N (50, 100 and 250 mg N·kg^-1) and P (5, 10 and 25 mg P·kg^-1) addition treatments. The above- and below-ground biomass, leaf traits (e.g., specific leaf area, leaf N and P contents) and root traits (e.g., specific root length, root N and P contents) of L. chinensis were determined in this study.Important findings Our results showed that: 1) the aboveground biomass and total biomass of L. chinensis were mostly affected by N addition, while the belowground biomass was mainly affected by P addition. N addition greatly enhanced the aboveground biomass of L. chinensis, while P addition reduced the belowground biomass at the moderate and high N levels. The root-shoot ratio of L. chinensis was influenced by both N and P additions, and root-shoot ratio decreased with increasing N and P levels. N and P additions promoted more biomass and N and P allocations to aboveground and leaf biomass. 2) Leymus chinensis showed different responses and adaptive mechanisms to P addition at low and high N levels. At low N level, L. chinensis exhibited high photosynthetic rate and specific root length (SRL) to improve photosynthetic capacity and root N acquisition, which promoted aboveground biomass. High root P content was favorable for belowground biomass. At high N level, P addition did not significantly affect plant growth of L. chinensis, even reduced its belowground biomass. Leymus chinensis showed high specific leaf area (SLA) and SRL to improve light interception and N acquisition in order to maintain stable aboveground biomass. 3) P addition greatly impacted below-ground than above-ground functional traits. SLA exhibited a weakly positive correlation with SRL, indicating L. chinensis exhibited relatively independence of resource acquirement and utilization between leaf and root functional traits.     

纳帕海高原湿地不同干扰强度下土壤真菌的分布格局

将无干扰的原生沼泽作为对照, 运用比较法研究了纳帕海高原湿地不同干扰强度下形成的湿地利用类型, 即沼泽(无干扰)、沼泽化草甸(轻度干扰)、草甸(中度干扰)和垦后湿地(重度干扰) 4个湿地利用类型的碳氮含量及其分布格局, 揭示干扰对纳帕海不同湿地利用类型碳氮及土壤真菌分布的影响。研究表明: (1) 4个湿地利用类型上下层土壤有机质(SOM)、全氮(TN)、碳氮比(C:N)和pH值均有显著的差异性(p < 0.01), 并且随着干扰强度的增大, SOM和TN含量逐渐减少。(2)土壤真菌经PDA培养基培养后计数, 在同一湿地类型上层的真菌数量大于下层, 随着干扰强度的增加, 真菌的数量逐渐增加。相关性分析表明: 真菌的数量与pH值、SOM和TN呈极显著负相关, 与C:N呈显著正相关。(3)系统发育研究表明: 纳帕海湿地分布有土壤真菌Ascomycota、Basidiomycota和Zygomycota, 其中Ascomycota是优势类群, 在高原湿地土壤碳氮分解等物质循环过程中Ascomycota处于主导地位。     

Responses of growth and litterfall production to nitrogen addition treatments from common shrublands in Mt. Dongling,Beijing, China

Aims The shrublands of northern China have poor soil and nitrogen (N) deposition has greatly increased the local soil available N for decades. Shrub growth is one of important components of C sequestration in shrublands and litterfall acts as a vital link between plants and soil. Both are key factors in nutrient and energy cycling of terrestrial ecosystems, which greatly affected by nitrogen (N) addition (adding N fertilizer to the surface soil directly). However, the effects and significance of N addition on C sequestration and litterfall in shrublands remain unclear. Thus, a study was designed to investigate how N deposition and related treatments affected shrublands growth related to C sequestration and litterfall production of Vitex negundo var. heterophylla and Spiraea salicifolia in Mt. Dongling region of China.
Methods A N enrichment experiment has been conducted for V. negundo var. heterophylla and S. salicifolia shrublands in Mt. Dongling, Beijing, including four N addition treatment levels (control (N₀, 0 kg N·hm^-2·a^-1), low N (N₁, 20 kg N·hm^-2·a^-1), medium N (N₂, 50 kg N·hm^-2·a^-1) and high N (N₃, 100 kg N·hm^-2·a^-1)). Basal diameter and plant height of shrub were measured from 2012-2013 within all treatments, and allometric models for different species of shrub’s live branch, leaf and root biomass were developed based on independent variables of basal diameter and plant height, which will be used to calculate biomass increment of shrub layer. Litterfall (litterfall sometimes is named litter, referring to the collective name for all organic matter produced by the aboveground part of plants and returned to the surface, and mainly includes leaves, bark, dead twigs, flowers and fruits.) also was investigated from 2012-2013 within all treatments.
Important findings The results showed 1) mean basal diameter of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were increased by 1.69%, 2.78%, 2.51%, 1.80% and 1.38%, 1.37%, 1.59%, 2.05% every year; 2) The height growth rate (the shrub height relative growth rate is defined with the percentage increase of plant height) of shrubs in the V. negundo var. heterophylla and S. salicifolia shrublands were 8.36%, 8.48%, 9.49%, 9.83% and 2.12%, 2.86%, 2.36%, 2.52% every year, respectively. Thee results indicated that N deposition stimulated growth of shrub layer both in V. negundo var. heterophylla and S. salicifolia shrublands, but did not reach statistical significance among all nitrogen treatments. The above-ground biomass increment of shrub layer in the V. negundo var. heterophylla and S. salicifolia shrublands were 0.19, 0.23, 0.14, 0.15 and 0.027, 0.025, 0.032, 0.041 t C·hm^-2·a^-1 respectively, which demonstrated that short-term N addition had no significant effects on the accumulation of C storage of the two shrublands. The litter production of the V. negundo var. heterophylla and S. salicifolia communities in 2013 were 135.7 and 129.6 g·m^-2 under natural conditions, respectively. Nitrogen addition promoted annual production of total litterfall and different components of litterfall to a certain extent, but did not reach statistical significance among all nitrogen treatments. Above results indicated that short-term fertilization, together with extremely low soil moisture content and other related factors, lead to inefficient use of soil available nitrogen and slow response of shrublands to N addition treatments.