Effects of three coniferous plantation species on plant-soil feedbacks and soil physical and chemical properties in semiarid mountain ecosystems

Background:Large-scale afforestation can significantly change the ground cover and soil physicochemical properties,especially the soil fertility maintenance and water conservation functions of artificial forests,which are very important in semi-arid mountain ecosystems.However,how different tree species affect soil nutrients and soil physicochemical properties after afforestation,and which is the best plantation species for improving soil fertility and water conservation functions remain largely unknown.Methods:This study investigated the soil nutrient contents of three different plantations(Larix principis-rupprechtii,Picea crassifolia,Pinus tabuliformis),soils and plant-soil feedbacks,as well as the interactions between soil physicochemical properties.Results:The results revealed that the leaves and litter layers strongly influenced soil nutrient availability through biogeochemical processes:P.tabuliformis had higher organic carbon,ratio of organic carbon to total nitrogen(C:N)and organic carbon to total phosphorus(C:P)in the leaves and litter layers than L.principis-rupprechtii or P.crassifolia,suggesting that higher C:N and C:P hindered litter decomposition.As a result,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved soil nutrients and clay components,compared with the P.tabuliformis plantation forest.Furthermore,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved the soil capacity,soil total porosity,and capillary porosity,decreased soil bulk density,and enhanced water storage capacity,compared with the P.tabuliformis plantation forest.The results of this study showed that,the strong link between plants and soil was tightly coupled to C:N and C:P,and there was a close correlation between soil particle size distribution and soil physicochemical properties.Conclusions:Therefore,our results recommend planting the L.principis-rupprechtii and P.crassifolia as the preferred tree species to enhance the soil fertility and water conservation functions,especially in semi-arid regions mountain forest ecosystems.

Mechanism of plant-soil feedback in a degraded alpine grassland on the Tibetan Plateau

Although biotic and abiotic factors have been confirmed to be critical factors that affect community dynamics,their interactive effects have yet to be fully considered in grassland degradation.Herein,we tested how soil nutrients and microbes regulated plant-soil feedback(PSF)in a degraded alpine grassland.Our results indicated that soil total carbon(STC;from 17.66 to 12.55 g/kg)and total nitrogen(STN;from 3.16 to 2.74 g/kg)exhibited significant(P<0.05)decrease from non-degraded(ND)to severely degraded(SD).Despite higher nutrients in ND soil generating significantly(P<0.05)positive PSF(0.52)on monocots growth when the soil was sterilized,a high proportion of pathogens(36%)in ND non-sterilized soil resulted in a strong negative PSF on monocots.In contrast,the higher phenotypic plasticity of dicots coupled with a higher abundance of mutualists and saprophytes(70%)strongly promoted their survival and growth in SD with infertile soil.Our findings identified a novel mechanism that there was a functional group shift from monocots with higher vulnerability to soil pathogens in the ND fertile soil to dicots with higher dependence on nutritional mutualists in the degraded infertile soil.The emerging irreversible eco-evolutionary in PSF after degradation might cause a predicament for the restoration of degraded grassland.

植物-土壤微生物反馈在草地演替过程中的作用机制

植物-土壤反馈影响生态系统结构、功能及过程,推动植物群落组成的变化,对解释植物群落的演替进程和方向、维持植物群落多样性和稳定性有着重要意义,已成为近年生物学和生态学研究热点。植物-土壤微生物反馈是植物-土壤反馈的重要组成部分。重点综述植物-土壤微生物反馈在植物群落演替过程中的作用机制,简要指出目前研究中存在的不足,并对未来研究中值得重点关注的科学问题进行了探讨与展望。

三裂叶豚草对其入侵地植物-土壤微生物反馈作用的影响

三裂叶豚草(Ambrosia trifida L)是入侵我国的重要杂草,目前对其入侵地土壤微生物群落反馈对三裂叶豚草入侵的影响尚不清楚。采用土壤接种的植物-土壤反馈研究方法,通过比较研究三裂叶豚草非入侵区和入侵区土壤接种物对三裂叶豚草和非入侵区由3种本地植物构成的人工群落的影响,分析三裂叶豚草对其入侵地土壤微生物反馈作用的影响,探讨三裂叶豚草入侵的土壤反馈机制。单独种植条件下,三裂叶豚草和本地植物对非入侵区和入侵区土壤接种物的响应不同(轮廓分析:F=76.18,P<0.001),非入侵区土壤接种处理本地植物的生物量较入侵区土壤接种处理高68.12%,而二者对三裂叶豚草生物量影响差异不显著,表明非入侵区土壤接种物调节了有利于本地植物生长的正反馈(Is=8.78,P=0.007)。但三裂叶豚草混种条件下,两种土壤接种处理对本地植物和三裂叶豚草生物量影响的差异均不显著,表明非入侵区土壤接种物在三裂叶豚草混种条件下对本地植物无显著的正反馈作用。无论是单独种植还是与三裂叶豚草混种种植,构成本地群落的3种植物对不同来源土壤接种物反馈作用的响应趋势均与对本地植物群落总生物量的响应趋势一致。可见,三裂叶豚草非入侵区土壤微生物群落能够调节有利于非入侵区植物生长的正反馈作用,但三裂叶豚草入侵能够削弱非入侵区土壤微生物群落对非入侵区植物的正反馈影响,从而促进自身的入侵过程。

紫茎泽兰和黄顶菊入侵对土壤微生物群落结构和旱稻生长的影响

为比较入侵植物与本地植物对土壤微生态影响的差异,探索外来植物入侵的土壤微生物学机制,本研究通过同质园试验,比较分析了2种入侵菊科植物(紫茎泽兰、黄顶菊)和2种本地植物(马唐、猪毛菜)对土壤肥力和微生物群落的影响,并通过盆栽反馈试验验证入侵植物改变后的土壤微生物对本地植物旱稻生长的反馈作用。同质园试验结果表明:2种入侵植物和2种本地植物分别对土壤微生态产生了不同的影响,尤其是紫茎泽兰显著提高了土壤有效氮、有效磷和有效钾含量,紫茎泽兰根际土壤中有效氮含量为39.80 mg.kg-1,有效磷含量为48.52 mg.kg-1。磷脂脂肪酸指纹图谱结果表明,2种入侵植物与2种本地植物相比,较显著增加了土壤中放线菌数量,而紫茎泽兰比其他3种植物显著增加了细菌和真菌数量。盆栽结果表明:黄顶菊生长过的土壤灭菌后比灭菌前旱稻株高增加113%,紫茎泽兰也使旱稻的株高增加17%。由以上结果可知,紫茎泽兰和黄顶菊可能通过改变入侵地土壤的微环境,形成利于其自身生长扩散的微生态环境从而实现其成功入侵。

土壤微生物增强了外来植物紫茎泽兰对本地植物种的竞争力（英文）

【背景】土壤微生物群落对植物种群建立、生长及其营养都起着至关重要的作用,植物入侵进程也可能与植物—土壤微生物互作相关。【方法】在温室条件下,研究了从紫茎泽兰入侵的土壤(IS)和本地植物生长的土壤(NS)中获得的微生物群落对外来杂草紫茎泽兰与本地植物生长及其互作的影响。【结果】接种来自IS接种剂的紫茎泽兰,特别是与黄花苜蓿或狗尾草共同种植时,较接种NS接种剂具有更高的丛枝菌根侵染率。来自IS的接种剂促进了与本地植物狗尾草共同栽培的紫茎泽兰的生长,但这一本地植物种的生长却未受影响。接种IS接种剂的紫茎泽兰抑制了与其临近种植的2种本地植物的生长,而接种NS接种剂时,未受此影响。接种IS接种剂时,所有种植组合中的紫茎泽兰对接种剂均呈正响应;而接种NS接种剂时,单独种植或与黄花苜蓿共同种植的紫茎泽兰对接种剂呈负响应。【结论与意义】存在于紫茎泽兰根周包括丛枝菌根真菌在内的土壤微生物,增强了这一入侵杂草与本地植物种的竞争力,这可能是外来植物入侵的一个重要机理。

五氯酚在厌氧生物体系中的降解及反馈作用

为探讨厌氧系统降解五氯酚(PCP)能力及PCP对厌氧系统的毒性影响,采用UASB反应器进行了PCP模拟污水连续流试验,考察了不同PCP浓度及负荷条件下系统对PCP和COD的降解去除规律,揭示了PCP对系统产酸相和产甲烷相影响状况.结果表明,在进水PCP含量从无到开始加入、PCP浓度提高以及PCP负荷提高3个冲击变化阶段,厌氧系统对PCP和COD的去除率均表现出先迅速降低后缓慢升高的变化趋势,运行稳定后PCP和COD的去除率分别达91.2%和83.5%以上.PCP对厌氧系统中微生物种群产生影响,使系统产酸菌由丁酸型菌群为主逐渐演替为丙酸型菌群为主,PCP对系统产甲烷菌活性产生明显抑制,甲烷产量由PCP加入前的12.1L/d降低至加入后的2.5L/d.

进水COD浓度对基于MFC的UASB生物传感器反馈性能的影响

考察MFC生物传感器在不同COD负荷条件下电信号的反馈情况.通过对比不同进水COD条件下的反馈时间,研究pH对MFC传感器反馈性能的影响.实验结果表明：MFC电信号与进水COD质量浓度具有良好的线性关系;在1000-3000mg/L的进水条件下,MFC稳定电压与进水COD质量浓度呈y=3.83×10^-5x＋0.25的线性增长关系,传感器的反馈时间为4h;随着进水COD质量浓度提升至4000-6000mg/L,MFC稳定电压与进水COD质量浓度呈y=-5.95×10^-5x＋0.54的线性下降关系,系统内挥发性脂肪酸大量积累导致pH降至4.6,反馈时间延缓至8.6h,系统长期处于酸化状态,产电微生物活性降低,电子传递速率受到抑制,传感器反馈时间延迟.

全球变暖背景下土壤微生物呼吸的热适应性:证据、机理和争议

土壤微生物呼吸的热适应性被认为是决定陆地生态系统对全球变暖反馈作用的潜在重要机制,可能显著改变未来的气候变化趋势,然而学术界对于这一机制是否真实存在尚有分歧。阐述了土壤微生物呼吸的热适应性概念,从证据、机理和争议3方面对已有研究进展进行了综述和分析。土壤微生物呼吸的热适应性是微生物在群落尺度上对温度变化的适应性,具有坚实的生物学与生态学理论基础,研究者们运用各类指标已在许多实验中证实土壤微生物物种及群落的呼吸过程能够在高温环境产生适应性变化。土壤微生物呼吸的热适应性机理涉及生物膜结构变化、酶活性变化、微生物碳分配比例变化和微生物群落结构变化等方面。关于土壤微生物呼吸热适应性的争议可能是由研究方法、微生物物种及环境条件的差异引起的。根据对已有研究的分析,认为土壤微生物呼吸的热适应性是真实存在的,未来的研究可进一步探索土壤微生物呼吸的热适应性机理,深入研究环境和全球变化对土壤微生物呼吸的热适应性影响,定量评估土壤微生物呼吸的热适应性对陆地生态系统反馈过程的影响。

植物–土壤反馈对禾草内生真菌响应

植物–土壤反馈是指植物的生长可以改变土壤的生物和非生物特性;反过来,土壤特性的改变可以影响植物的生长,进而改变植物群落的结构和动态。禾草内生真菌对植物–土壤反馈有重要影响。本文主要总结了Epichlo?属禾草内生真菌对宿主植物根际土壤化学性质、根际微生物、植物竞争力以及对生态适应机制的影响。研究发现,禾草内生真菌的侵染会对土壤营养元素产生影响,致使土壤有机碳、土壤全氮含量发生改变。禾草内生真菌对根际土壤微生物生物量和微生物群落产生作用,致使革氏兰阴性细菌、菌根真菌和球囊霉素等产生不同地变化。禾草内生真菌参与宿主植物的生活史,影响宿主植物的种内种间竞争,对生物群落结构和物种丰富度产生影响。

吸烟与非吸烟者口腔微生物多样性形成机制对比分析

目的:探究烟草对口腔微生物多样性形成与演替影响机制。方法:追踪调查了吸烟和非吸烟者各20例4个月口腔的5个常见菌属——链球菌属、普氏菌属、嗜血杆菌属、罗氏菌属和韦荣氏菌属的比生长速率、胞内脂类物质含量及种群数量变化。结果:非吸烟者口腔微生物胞内的脂类物质含量显著增高,而比生长速率却有不同的变化,而各菌群动态呈现出明显的异步波动趋势。非吸烟者口腔微生物多样性形成与维持包括两种基本动力学机制:一是底物分解产物对种群的负反馈调节,二是微生物对口腔环境发生的时滞响应。而吸烟者恰恰相反,口腔菌群多样性降低且有紊乱的趋势。结论:吸烟对口腔菌群多样性产生负面影响,不易形成稳定种群多样性;非吸烟者口腔微生物群落中的各菌种数量呈现异步趋同波动,从而大大减弱菌群内部的种间竞争,在口腔中形成与维持较高的物种多样性。

不同禾草生长对甘肃马先蒿群落土壤养分和微生物群落的影响

为探讨不同禾草-土壤反馈对甘肃马先蒿(Pedicularis kansuensis)群落土壤养分及微生物群落结构组成和功能的影响,本研究以4种禾草为材料,以甘肃马先蒿为主的退化草地植物群落土壤为栽培基质,通过盆栽控制试验,分析了禾草生长对甘肃马先蒿土壤养分和微生物群落组成的影响,并采用FUNGuild和FAPROTAX工具分别对真菌和细菌群落进行功能注释分析。结果表明:与空白对照相比,不同禾草生长提高了土壤pH及铵态氮含量,使速效钾和硝态氮含量显著降低,有机质含量无显著差异。不同禾草在甘肃马先蒿土壤中生长的株高、禾草碳、氮、钾含量、土壤真菌和细菌群落的多样性指数、相对丰度因禾草种类而异。不同禾草生长对禾草养分、土壤养分和微生物群落产生直接影响,禾草养分、土壤养分和微生物群落反馈作用对禾草生物量产生影响。本研究以期为甘肃马先蒿为优势种的退化草地改良和人工草地管理提供科学依据。

Soil legacy effects and plant-soil feedback contribution to secondary succession processes

Secondary succession is the process by which a community develops into a climax community over time.However,knowledge on the mechanisms,relating to soil legacy effects(soil chemistry and enzyme activity)and plant-soil feedback(PSF),driving community succession remains limited.In this work,we examined the PSF associated with three succession stage species through a 2-year greenhouse experiment.Setaria viridis,Stipa bungeana,and Bothriochloa ischemum were selected to represent dominant and representative early-,mid-,and late-successional stage species,respectively,of semiarid grasslands on the Loess Plateau.In response to the different soil origin,the shoot biomass of early-,mid-,and late-species were all higher when grown in their own soil than in other species’soils,which indicated that the PSF of three species were positive.Over two growth periods,the early-species experienced a negative PSF,but the mid-and late-species experienced negative,neutral and positive PSF in the soil of early-,mid-and late-species,respectively.Our study demonstrates that soil legacy effects and PSF have a significant impact on community succession processes.

Similarity in fine-to-total root mass ratio leads to comparative plant-soil feedbacks between co-occurring native and invasive plants

Aims Soil biota can affect plant-plant interactions and non-native plant invasions via plant-soil feedback(PSF).Understanding the drivers underlying interspecific variations in PSF is im portant for predicting the role of soil biota in non-native plant invasions.Recent studies found that PSF could be predicted by plant traits.The success of plant invasions is also linked with plant traits,suggesting a potential linkage between PSF and plant invasion via plant traits,but has not yet been tested.Here,we compared PSF between six phylogenetically paired co-occurring native and invasive plants,and explored the potential linkage between PSF with plant root traits.Methods We conducted a two-phase PSF experiment.Field collected soils were conditioned by the six plant species for 3 months firstly,then seedllings of these plants were grown in living or sterilized soils that had been conditioned by conspecific vs.heterospecific(the conge ner/confamilial species)individuals.We estimated effects of biota in conspecific(conspecific PSF)or heterospecific(heterospecific PSF)soils relative to sterilized soils,and the relative effects of biota in conspecific vs.heterospecific soils(PSF-away)on plant biomass.Important Findings In general,soil biota suppressed plant growth,and there were no differences in conspecific PSF,heterospecific PSF and PSF-away between native and invasive plants.PSF increased with rising plant fineto-total root mass ratio in the presence of soil biota,and its value was comparable between native and invasive plants.Our results indicate that similarity in plant fine-to-total root mass ratio that predicted PSF may have partially led to the comparable PSFs between these native and invasive plants.Studies exploring the linkages among plant traits,PSF and plant invasions with more plants,in particular phylogenetically distant plants,are needed to improve our understanding of the role of soil biota in plant invasions.

Invasive grasses consistently create similar plant-soil feedback types in soils collected from geographically distant locations

Aims Plants of similar life forms and closely related species have been observed to create similar types of plant–soil feedbacks(PSFs).However,investigations of the consistency of PSFs within species have not yielded clear results.For example,it has been reported that species create different types of PSFs in their native and introduced ranges.The aim of this project is to examine if four species create similar PSF types from soils collected from widely distributed areas within their introduced range.The soil for this project was collected from three areas in western North America.With this design,we aim to determine species-and site-specific ability to create PSFs and if the type of PSF created is consistent in all soil from all three collection areas.The species examined are Agropyron cristatum,Centaurea solstitialis,Poa pratensis and Taeniatherum caput-medusae.Methods We used three-field collected soils(from northern Nevada,western Montana and eastern Montana)in a two-phase greenhouse experiment to quantify the type of PSFs created by four invasive species.The first phase was a conditioning phase wherein each invasive species created species-specific changes to the soil.The second phase of the experiment was the response phase wherein both the conditioning species and a native phytometer were grown in the conditioned soil and in unconditioned(control)soil.The final aboveground biomass was used to evaluate the effect of conditioning and to determine the type of PSF created by each invasive species.Important Findings Our results suggest that three of our four study species did show consistency in relation to PSF.Two species A.cristatum and T.caputmedusae consistently created PSF types that benefit conspecifics more than heterospecifics(and thus are‘invasive’PSF types)and P.pratensis consistently exhibited no,or‘neutral’,feedbacks.The fourth species(C.solstitialis)was inconsistent:in one soil,no feedback was created;in other soil,an invasive PSF was created and in the last soil,a feedback that relatively benefited the native phytometer was created.Thus,PSFs appear to uniformly contribute to the success of two species(A.cristatum and T.caput-medusae)but not C.solstitialis nor P.pratensis.

Microbial insecticide model and homoclinic bifurcation of impulsive control system

A new microbial insecticide mathematical model with density dependent for pest is proposed in this paper.First,the system without impulsive state feedback control is considered.The existence and stability of equilibria are investigated and the properties of equilibria under different conditions are verified by using numerical simulation.Since the system without pulse has two positive equilibria under some additional assumptions,the system is not globally asymptotically stable.Based on the stability analysis of equilibria,limit cycle,outer boundary line and Sotomayor's theorem,the existence of saddle-node bifurcation and global dynamics of the system are obtained.Second,we consider homoclinic bifurcation of the system with impulsive state feedback control.The existence of order-1 homoclinic orbit of the system is studied.When the impulsive function is slightly disturbed,the homoclinic orbit breaks and bifurcates order-1 periodic solution.The existence and stability of order-1 periodic solution are obtained by means of theory of semi-continuous dynamic system.

林下植被对土壤微生物群落组成与结构的影响

植被和土壤微生物是生态系统的重要组成部分,研究二者之间的联系对森林经营管理和生态恢复实践具有重要的指导意义.目前相关研究主要集中于乔木层对土壤微生物的影响,林下植被层对土壤微生物的潜在作用常被忽视.本文从林下植被对土壤微生物群落组成与结构的影响及其作用机理两个方面进行总结:(1)林下植被对土壤微生物有重要的影响,其作用结果有正面、负面和没有影响几方面;(2)作用途径为通过分泌物和凋落物归还的质与量等直接影响土壤微生物群落结构和组成,也通过影响土壤微气候环境、土壤营养有效性和p H、改变乔木层和其他土壤微生物类群而间接影响土壤微生物;(3)在林下植被对土壤微生物影响的研究中,试验方法多采用磷酸脂肪酸(PLFA)法,而最新土壤微生物的测定方法(如高通量测序等)应用较少.今后林下植被影响土壤微生物群落的研究重点在于(1)提高土壤微生物测定方法的准确性;(2)扩展研究方向;(3)与应用方面相联系.

宏基因组方法揭示草地土壤微生物群落响应全球变化

草地在生物圈中发挥着重要的生态服务功能,而草地土壤微生物又是维持生态系统功能和稳定的关键要素之一。过去十几年间,宏基因组方法的进步为微生物群落分析提供了有力的工具。本文综述了宏基因组方法应用于草地土壤微生物群落响应全球变化的最新研究进展,特别是针对气候变化、大气组成变化、土地利用方式改变和外来物种入侵等条件下微生物群落的响应规律和反馈机制的研究。这些研究对于我们认识和了解微生物群落的生态功能十分重要,同时也对维持地球生态系统平衡具有积极的意义。最后,我们对未来应用宏基因组方法研究草地微生物群落进行了展望。

A comprehensive review on coupled processes and mechanisms of soil-vegetation-hydrology, and recent research advances

Research on the coupling of soil,vegetation,and hydrological processes is not only a research hotspot in disciplines such as pedology,ecohydrology and Earth system science but also important for achieving sustainable development.However,scientists from different disciplines usually study the coupling mechanism of soil-vegetation-hydrological processes at very different space and time scales,and the mechanistic connections between different scales are quite few.This article reviewed research advances in coupled soil-vegetation-hydrological processes at different spatial scales—from leaf stomata to watershed and regional scales—and summarized the spatial upscaling methods and modeling approaches of coupled soil-vegetationhydrological processes.We identify and summarize the following coupling processes:(1)carbon-water exchange in leaf stomata and root-soil interface;(2)changes in soil aggregates and profile hydraulic properties caused by plant roots and water movement;(3)precipitation and soil moisture redistribution by plant canopy and root;(4)interactions between vegetation patches and local hydrological process;(5)links between plant community succession and soil development;and(6)links between watershed/regional water budget and vegetation phenology and production.Meanwhile,the limitations and knowledge gaps in the observations,mechanisms,scaling methods,and modeling approaches of coupled soil-vegetation-hydrological processes were analyzed.To achieve a deep integration of various coupling processes across different spatiotemporal scales,future work should strengthen multiscale,multifactor and multiprocess soil-vegetation-hydrology coupling observations and mechanism studies,develop new scaling methods,identify different feedback pathways,and take time-variable plant behavior and soil hydraulic properties into account during modeling.

The rhizosphere effect on soil gross nitrogen mineralization: A meta-analysis

Rhizosphere effects play crucial roles in determining soil carbon(C)and nitrogen(N)cycling.However,the rhizosphere effect on soil gross nitrogen(N)mineralization(Nmin)has not been quantitatively assessed on the global scale.Here we performed a meta-analysis of compiled data from 24 publications and 37 species to synthesize the rhizosphere effect on soil gross Nmin and its influencing factors.We found that the rhizosphere effect significantly enhanced soil gross Nmin by 81%on average.Such rhizosphere effect was significantly higher in woody species than in nonwoody species,and higher in ECM(ectomycorrhizal)associated species than in AM(arbuscular mycorrhizal)associated species.Moreover,the variations of the rhizosphere effect on soil gross Nmin were correlated with those on soil C mineralization,phenol oxidase activity and root biomass rather than with other plant(growth form and mycorrhizal association)and climatic(mean annual temperature and precipitation)factors.These results support the‘microbial activation’and‘microbial N mining’hypotheses of rhizosphere effects and indicate the coupling of soil C and gross N mineralization in the rhizosphere.Overall,these findings provide novel insights into the rhizosphere effect on soil gross Nmin among plant growth forms and mycorrhizal associations,and improve our mechanistic understanding of soil N dynamics in the rhizosphere.