外来种湿地松凋落物对土壤微生物群落结构和功能的影响

外来种湿地松是我国亚热带地区大面积造林树种,研究其凋落物影响下土壤微生物群落结构和功能的变化,对于全面科学的评价湿地松的生态影响具有重要的理论与实践意义。通过凋落物袋 小盆模拟试验研究,分两个时期(分解5个月和18个月)比较了外来种湿地松与本地种马尾松的凋落物对土壤微生物群落结构(磷脂脂肪酸)和功能(碳代谢)的影响,结果表明：(1)外来种湿地松凋落物的C:N高于本地种马尾松;(2)两个时期,湿地松凋落物处理土壤细菌和放线菌的磷脂脂肪酸含量均低于马尾松,18个月时湿地松凋落物处理土壤真菌含量和群落真菌/细菌显著高于马尾松处理;(3)湿地松凋落物影响下土壤微生物群落功能多样性显著低于马尾松;(4)土壤微生物群落的结构显著影响微生物的活性和功能多样性：土壤微生物群落碳源代谢的强度、多样性及丰富度与细菌磷脂脂肪酸含量呈极显著正相关,细菌特征脂肪酸14:0、15:0、a15:0、i16:0、16:1ω7c、a17:0和cy19:0的含量显著影响土壤微生物群落碳代谢功能。上述结果表明：与本地种马尾松相比,引进种湿地松的凋落物显著改变了土壤微生物群落结构,降低了微生物群落的功能。     

南亚热带乡土树种人工纯林及混交林土壤微生物群落结构

以我国南亚热带格木、马尾松人工纯林及二者混交林林地土壤为对象,运用磷脂脂肪酸(PLFAs)法研究了3种人工林土壤微生物生物量和群落结构特征.结果表明: 旱季土壤微生物的PLFAs总量及各菌群的PLFAs量显著高于雨季.旱季土壤微生物的PLFAs总量、细菌PLFAs量、真菌PLFAs量、放线菌PLFAs量均为马尾松人工林最高,混交林次之,格木林最低;而雨季格木人工林土壤微生物的PLFAs总量、细菌PLFAs量、真菌PLFAs量、丛枝菌根真菌PLFAs量高于混交林,并显著高于马尾松人工林.主成分分析表明,土壤微生物群落结构组成受林分类型和季节的双重影响.冗余分析表明,土壤温湿度、pH值、全氮及铵态氮含量与特征磷脂脂肪酸之间呈显著相关关系.在全年水平上,混交林土壤真菌/细菌比值始终高于格木林和马尾松林,表明格木与马尾松混交更有利于提高土壤生态系统的稳定性.     

天然及人工红树林土壤微生物群落结构分析

应用高通量测序和OTU 分析法比较了红树植物人工修复区(Transplant-, TP)与天然区(Natural-, NA)土壤微生物的群落结构差异。结果显示: 从群落组成来看, 细菌在天然林和人工林主要由27 个门类的菌群组成, 优势菌群包括变形杆菌(Proteobacteria)、拟杆菌(Bacteroidetes)、绿弯菌(Chloroflexi)、酸杆菌(Acidobacteria)、浮霉菌(Planctomycetales)。古菌的组成在纲的水平上主要以盐杆菌(Halobacteria)、热原体(Thermoplasmata)和甲烷菌(甲烷微菌Methanomicrobia、甲烷杆菌Methanobacteria、甲烷球菌Methanococci)为主, 其中盐杆菌占的比重最大(约19%-37%)。从结构来看, 多样性指数(H)和丰富度指数(Schao)表明: 天然林和人工林细菌的多样性和丰度均高于古菌, 天然林多样性及丰度均高于人工林(NA>TP)。此外, 对采集的样本进行主成分分析(PCA)显示细菌聚成两大类: 源自外周土壤的菌群聚成一类, 源自根际土壤的菌群聚成另一类; 古菌则按生境聚成三类: 分别是天然林、人工林和采自非红树区的基围鱼塘。对细菌来说, 经长时间修复的人工林与天然林的外周土壤群落结构差异不大, 显示出了趋同性; 但同一环境下的根际与外周土壤群落结构差异较大, 体现了明显的根际效应。古菌结构受根际效应的影响较小, 受环境因素影响较大。     

不同森林恢复方式对我国南方红壤区土壤质量的影响

2008-2009年在我国南方红壤区,研究了3种典型森林恢复方式(自然恢复的天然次生林、人工恢复的本地种马尾松人工林和引进种湿地松人工林)对林地土壤质量的影响.结果表明:天然次生林的土壤含水量、土壤容重、土壤粒径构成、土壤全碳、全氮、全磷、有机碳、速效氮、速效磷、速效钾含量均优于两种人工林.综合土壤物理性状、化学性状和微生物性状得到土壤质量综合指数.天然次生林土壤的综合质量指数(1.20+0.10)显著高于马尾松人工林(0.59±0.03)和湿地松人工林(0.59±0.06),而两种人工林之间差异不显著.在我国南方红壤区,自然恢复的天然次生林土壤质量优于人工恢复的马尾松林和湿地松林.     

南亚热带马尾松-红椎混交林及其纯林土壤细菌群落结构与功能

营建乡土阔叶树种人工纯林和针阔混交林是我国亚热带地区森林经营的发展趋势,但对人工纯林和针阔混交林土壤细菌群落结构及功能知之甚少。本研究以南亚热带乡土针叶树种马尾松、阔叶树种红椎人工纯林及二者的混交林为对象,运用细菌16S rRNA基因高通量测序技术和PICRUSt基因功能预测,分析了3种人工林不同土层(0～20、20～40和40～60 cm)土壤细菌群落的结构与功能。结果表明: 混交林和马尾松林土壤细菌群落结构相似,但与红椎林差异显著,红椎林土壤细菌群落多样性、生物通路代谢功能和氮循环功能低于马尾松林和混交林;土壤全氮、硝态氮和C/N是导致红椎林与马尾松林和混交林土壤细菌群落结构及功能差异的主要土壤理化因子。就土壤细菌群落结构与功能而言,在该地区营造红椎和马尾松针阔混交林要优于红椎纯林。     

南方红壤区3种典型森林恢复方式对植物群落多样性的影响

合理的森林恢复方式能提高植物多样性,进而提高生态系统服务功能.在我国南方红壤区研究了3种典型森林恢复方式(引进种恢复的湿地松(Pinus elliottii)人工林本地种恢复的马尾松(Pinus massoniana)人工林和自然恢复的天然次生林)的植物区系构成和植物群落多样性.结果表明:(1)湿地松人工林有155种植物,隶属66科118属,马尾松人工林有137种植物,隶属59科97属;天然次生林有226种植物,隶属86科160属,3种森林恢复方式的乔木层、灌木层和草本层的优势科属明显不同,马尾松人工林的优势物种和天然次生林更相似;(2)天然次生林的植物区系基本构成、植物区系类型种类高于马尾松人工林和湿地松人工林,并且天然次生林的温带成分比例高于湿地松人工林;(3)恢复方式对植物群落的多样性指数有显著影响,天然次生林的物种丰富度、辛普森指数明显高于马尾松人工林和湿地松人工林,两种人工林之间差异不显著;(4)3种森林恢复方式的植物群落结构存在显著差异,相比湿地松人工林,马尾松人工林的植物群落组成与天然次生林更相似.总之,自然恢复的天然次生林植物群落多样性高于人工恢复的马尾松人工林和湿地松人工林,本地种马尾松人工林在维持区域植物群落结构功能上优于引进种湿地松人工林.     

引进种桉树人工林取代天然次生林对土壤微生物群落结构和功能的影响

由于桉树对原生生态系统具有潜在的破坏性影响,随着桉树人工林面积的不断扩大,桉树种植对森林生态系统的影响越来越受到社会的关注。围绕引进种桉树造林对土壤微生物群落的影响,应用成对试验设计,采用磷脂脂肪酸(PLFA)和BIOLOG微平板培养等技术手段探讨土壤微生物群落结构和功能如何响应桉树人工林取代天然次生林这一变化,主要结果为:桉树人工林取代天然次生林导致:(1)土壤微生物生物量减少,包括:生物量碳、氮和磷脂脂肪酸丰度显著下降;(2)反映土壤微生物群落生理胁迫状况的指标:饱和直链脂肪酸/单不饱和脂肪酸、革兰氏阳性菌/革兰氏阴性菌、支链异构/反异构脂肪酸以及cy19:0/18:1ω7c的比值显著增加;(3)土壤微生物群落碳代谢强度和多样性显著降低;(4)桉树人工林取代天然次生林导致土壤微生物群落结构变化和功能退化的主要环境因素包括:植物物种丰富度和覆盖度的降低以及土壤资源(碳、氮和水分)可获得性的降低。综上所述,引进种桉树人工林取代天然次生林降低了植物物种丰富度和覆盖度以及土壤资源的可获得性,进而显著增强了土壤微生物群落生理胁迫、显著降低了土壤微生物群落功能。     

基于PLFA的高山栎和高山松林松茸菌塘土壤微生物群落特征研究

通过磷脂脂肪酸(Phospholipid fatty acid,PLFA)生物标记法对云南省香格里拉县的高山栎林和高山松林内的松茸菌塘和非菌塘的土壤微生物群落进行对比分析,结果显示:1)菌塘内的优势菌群主要包括真菌(18:2ω6,9c、18:1ω9c、18:3 w6c(6,9,12))、革兰氏阴性菌(19:0 cyclo w8c)、革兰氏阳性菌(15:0 iso)和未被鉴定的PLFAs(16:0、17:1 anteiso B、18:1 w6c、16:1 w6c和18:0);2)从群落组成上看,菌塘内的真菌百分含量、真菌/细菌生物量比(F/B)显著高于非菌塘,而革兰氏阴性菌(GNB)和革兰氏阳性菌(GPB)的百分含量,以及总PLFAs均匀度(J)均低于非菌塘;3)从群落结构上看,土壤微生物群落在菌塘和非菌塘间、以及不同林型间均存在显著差异,且菌塘对群落结构的影响大于林型;4)无论是在群落组成还是群落结构上,林型均不与菌塘存在交互作用,即松茸菌塘的土壤微生物群落特征不随宿主森林类型而发生改变;5)土壤化学性质与林型密切相关,但与菌塘关系不明显。上述结果表明,菌塘内的土壤微生物群落组成和结构与非菌塘有所不同,且在两种林型中表现相似。     

不同森林恢复方式对我国南方红壤区土壤质量的影响

2008-2009年在我国南方红壤区,研究了3种典型森林恢复方式(自然恢复的天然次生林、人工恢复的本地种马尾松人工林和引进种湿地松人工林)对林地土壤质量的影响.结果表明： 天然次生林的土壤含水量、土壤容重、土壤粒径构成、土壤全碳、全氮、全磷、有机碳、速效氮、速效磷、速效钾含量均优于两种人工林.综合土壤物理性状、化学性状和微生物性状得到土壤质量综合指数.天然次生林土壤的综合质量指数(1.20±0.10)显著高于马尾松人工林(0.59±0.03)和湿地松人工林(0.59±0.06),而两种人工林之间差异不显著.在我国南方红壤区,自然恢复的天然次生林土壤质量优于人工恢复的马尾松林和湿地松林.     

亚热带森林转换对土壤微生物呼吸及其熵值的影响

土壤微生物呼吸及其熵值是表征土壤质量变化的敏感性指标,不仅能衡量土壤微生物碳利用效率,还能揭示土壤有机碳的变化。通过比较亚热带米槠天然林转换为马尾松人工林和杉木人工林后土壤微生物呼吸速率、土壤微生物生物量碳以及微生物熵、代谢熵的差异,研究亚热带森林转换对土壤微生物碳利用效率的影响。研究结果显示:(1)与天然林相比,马尾松人工林0—10 cm土壤微生物呼吸速率上升32%(P0.05),马尾松人工林和杉木人工林10—20 cm土壤微生物呼吸速率分别下降26%和24%(P0.05);但在20—40 cm土层和40—60 cm土层,天然林土壤微生物呼吸速率比马尾松人工林分别高50%和43%;(2)马尾松人工林和杉木人工林0—10 cm土层土壤微生物生物量碳(MBC)比天然林分别下降19%和40%(P0.05),但马尾松人工林10—20 cm土壤MBC上升29%(P0.05);(3)人工林表层土壤微生物熵与天然林没有显著差异,但与天然林相比,杉木人工林和马尾松人工林20—40 cm土层土壤微生物熵分别下降51%和71%(P0.05),40—60 cm分别下降52%、66%(P0.05)。土壤微生物代谢熵的变化主要发生在0—10 cm土层,马尾松人工林和杉木人工林分别比天然林增加38%和29%(P0.05),在深层土壤,3种林分微生物代谢熵没有显著差异。亚热带森林转换导致表层土壤微生物碳利用效率下降,深层土壤易分解碳在总有机碳库中占比下降,有机碳可利用程度降低。     

氮添加和采脂对湿地松林土壤酶活性及酶化学计量比的影响

大气氮沉降和采脂会引起树木生长和代谢的变化,从而影响土壤养分循环和酶活性.土壤酶和酶化学计量可以揭示土壤碳、氮循环和微生物生长代谢过程的养分限制,但目前亚热带湿地松人工林土壤酶和酶化学计量对氮添加和采脂的响应还不清楚.以亚热带北缘的湿地松人工林为研究对象,设置采脂(resin tapping,RT)和未采脂(no re...     

Soil CO2 efflux and its spatial variation in a Florida slash pine plantation

The efflux of CO2 from the soil surface can vary markedly in magnitude both in time and space and its correct determination is crucial in many ecological studies. In this paper, we report results of field measurements, using an open-top dynamic chamber, of soil CO2 efflux in a mature Florida slash pine (Pinus elliottii Engelm. var.elliottii) plantation. The daily average efflux was 0.217 mg CO2 m-2s-1 in the autumn and 0.087 mg CO2 m-2s-1 in the winter. Soil temperature, which accounts for most of the temporal variability in CO2 efflux, is by far the most influential factor controlling soil respiration rate and its temporal variation. The CO2 efflux in the slash pine plantation is highly spatially variable and effluxes from the soil under palmetto is significantly higher than that from the open floor. The CO2 efflux generally increases with increase in soil fine root biomass, litter and humus amount on the forest floor but is inversely related to the amount of organic matter in the mineral soil. The spatial variation in CO2 efflux can be well characterised by a simple multiple regression model incorporating live and dead biomass and soil total porosity as predictor variables. Understorey plants, mostly Serenoa repens, are an important component of the C cycle and the major contributor to the spatial heterogeneity of soil CO2 efflux. The influence of understorey plants on soil respiration is probably via two approaches: increasing litterfall and root metabolism, both consequently stimulating microbial activity in the mineral soil.     

Molecular characterization of methanotrophic communities in forest soils that consume atmospheric methane

Methanotroph abundance was analyzed in control and long-term nitrogen-amended pine and hardwood soils using rRNA-targeted quantitative hybridization. Family-specific 16S rRNA and pmoA/amoA genes were analyzed via PCR-directed assays to elucidate methanotrophic bacteria inhabiting soils undergoing atmospheric methane consumption. Quantitative hybridizations suggested methanotrophs related to the family Methylocystaceae were one order of magnitude more abundant than Methyloccocaceae and more sensitive to nitrogen-addition in pine soils. 16S rRNA gene phylotypes related to known Methylocystaceae and acidophilic methanotrophs and pmoA/amoA gene sequences, including three related to the upland soil cluster Alphaproteobacteria (USCalpha) group, were detected across different treatments and soil depths. Our results suggest that methanotrophic members of the Methylocystaceae and Beijerinckiaceae may be the candidates for soil atmospheric methane consumption.     

中亚热带湿地松(Pinus elliottii)人工林生长过程

基于树干解析和树轮分析,结合野外调查,揭示了我国主要外来树种--湿地松(Pinus elliottii)的生长规律,从而为人工林经营管理和生态系统服务功能评估提供了依据。2005年调查了1948年江西吉安青原山引种后存留的564株湿地松(1954 1958年生)。胸径(DBH, diameter at breast height)平均值为34.2 cm(18.4-58cm),树高平均值为19.5 m(9-33m)。青原山湿地松树轮分析结果显示:52年间,年树轮宽度增长量平均值为0.32 cm,最大年增长量不超过1.14 cm。胸径年生长量总体上呈下降趋势,直径生长高峰出现在10a左右;林龄达到20a左右时,直径年生长量开始下降;林龄40a后,生长变得极为缓慢。距青原山西南100km的千烟洲湿地松林(20年生)胸径和树高平均值分别为15.9 cm和11.0 m;20a的胸径生长量平均值为0.86 cm;材积方程为V= 0.0000213 D^2.9870924(V为带皮材积,D为胸径)。千烟洲湿地松林生物量低于同期营造的马尾松(Pinus massoniana)林生物量,也明显低于中亚热带地带性植被樟树(Cinnamomum camphora)林的生物量。经比较发现,引种营造的湿地松林,其生长量远不如原产地美国佛罗里达州湿地松林。     

Soil carbon dynamics in a Pinus massoniana plantation following clear-cutting and slash removal

Aims Slash removal is a common practice to prepare recently harvested sites for replanting. However, little is known about its impact on soil carbon (C) dynamics in subtropical plantations. This study evaluates the effects of burning versus manual slash removal site preparation treatments on soil organic carbon (SOC), soil respiration and soil microbial community structure in a Pinus massoniana plantation in southern China.Methods Three areas within a mature P. massoniana plantation were clearcut. Two months following harvesting, slash on one-half of each area was burned (BURN), whereas slash was manually removed (MANR) on the other portion. Slash removal treatments were also compared with adjacent uncut plantation areas (UNCUT). Soil samples, and soil respiration measurements were used to characterize soil properties and microbial communities following slash removal treatments. Important findings Mean soil respiration rates from the MANR and BURN treatments were 26% and 17% lower, respectively, than the UNCUT treatment over 1 year. The MANR and BURN treatment resulted in soils with 27% and 9% reduction in total phospholipid fatty acids (PLFAs) and 18% and 10% reduction in bacterial PLFAs, respectively, compared with the UNCUT treatment. However, no significant differences existed between slash removal treatments with respect to soil chemical properties, SOC chemical compositions, soil respiration and microbial communities; although PLFA patterns were notably different for the burned plots. Most factors affecting C dynamics and microbial communities were not sensitive to the differences imparted to the ecosystem due to manual slash removal or burning. Our results suggested that low-intensity burning after clear-cutting might have no significant effect on soil C pool and its dynamics compared with manual slash removal in subtropical plantations.     

Bacteria associated with ectomycorrhizas of slash pine (Pinus elliottii) in south-eastern Queensland, Australia

Bacterial communities associated with ectomycorrhizal and uncolonized roots of Pinus elliottii (slash pine) collected from a plantation in south-east Queensland, Australia, were investigated, using cultivation-dependent and -independent methods. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene PCR products obtained using a cultivation-independent approach revealed that bacterial communities associated with ectomycorrhizal root tips differed significantly from those associated with roots uncolonized by ectomycorrhizal fungi. DGGE analysis of cultivable bacterial communities revealed no significant difference between ectomycorrhizal and uncolonized roots. Neither analytical approach revealed significant differences between the bacterial communities associated with ectomycorrhizal roots colonized by a Suillus sp. or an Atheliaceae taxon. Cloned bacterial 16S rRNA genes revealed sequence types closely related with that of Burkholderia phenazinium, common in both ectomycorrhizal-colonized and -uncolonized roots, while sequence types most similar to the potentially phyopathogenic bacteria Burkholderia andropogonis and Pantoea ananatis were only detected in ectomycorrhizal roots. These results highlight the possibility of global movement of microorganisms, including putative pathogens, as a result of the introduction of exotic pine plantations.     

Biological legacies soften pine plantation effects for bryophytes

Biological legacies are organic structures and patterns remaining after a disturbance that may contribute to the complexity of the recovering vegetation. Legacies may, in turn, reduce the impacts of human disturbances such as logging and habitat transformation on elements of biodiversity. To examine the effects of biological legacies on biotic responses after disturbance, we surveyed 32 sites for bryophytes in an area subject to large-scale conversion of native eucalypt forest to exotic Pinus radiata D. Don plantations in eastern Australia. We sampled bryophyte and substrate diversity (log, bare ground, upturned tree/log, and trees) in eight sites in each of four landscape context classes: pine plantation stands, elliptical-shaped remnants, strip-shaped remnants, and controls in a large area of contiguous, unmanaged eucalypt forest. We found a muted response by individual species of bryophyte to landscape context. We attribute this, in part, to the presence of logs in the intensively managed pine plantation sites. The boost in bryophyte diversity from species on logs meant that some pine sites supported similar species composition to the continuous eucalypt forest controls. Our findings also underline the importance of local controls and structural variation, including leaving logs and native trees in plantations, for enhancing bryophyte species richness in managed landscapes.