草原黑蘑(Agaricus arvensis)圈对牧草生产的影响

在黑蘑圈上、圈内及圈外分别作测产样方,分析它们之间的差异。结果表明：黑蘑圈可极显著地提高群落地上生物量。其中对羊草(Leymus chinensis)的影响较大,圈上羊草的生物量和密度均明显高于圈内、圈外;对其它植物的影响不明显。黑蘑圈可增强植物的吸水力和储水力。     

草原蘑菇圈对牧草长势影响的初步分析

在白蘑,黄蘑圈上,圈内及圈外分别作测产样方,分析它们之间的差异。结果表明：白蘑,黄蘑圈均可极显著地提高群落地上生物量。其对羊草的影响较显著,圈上羊草的生物量,株高,密度及单株重均明显高于对圈内,圈外;对黄囊苔草和其它植物的影响不明显。白蘑圈对羊草的影响较黄蘑圈小。     

蒙古白丽蘑蘑菇圈土壤真菌多样性

通过2011—2012年间在呼伦贝尔市陈巴尔虎旗境内3个蒙古白丽蘑蘑菇圈样地的调查、采集和实验室研究,共分离得到蘑菇圈内、外可培养土壤真菌26属,其中圈上分离得到19属,圈外分离得到24属,圈上、圈外共有属17属。形态和分子鉴定确认特异性地存在于蘑菇圈上的土壤真菌有印度毛壳Chaetomium indicum Corda、花序棘壳孢Pyrenochaeta inflorescentiae Crous,Marinc.M.J.Wingf两种。7月1日到9月18日期间,蘑菇圈圈上与圈外土壤真菌数量变化趋势大体一致,但8月11日圈上的数量明显多于圈外。种类数目除了圈外在7月24日变化较大外,其余圈上和圈外均相对平稳。蘑菇圈外土壤真菌数量和种类随着土层加深呈减少趋势,但深度为7~14 cm的土层圈上土壤真菌数量大量增加,圈外的种类丰富于圈上。分析认为蘑菇圈抑制土壤真菌的种类,但对一些特定种类的生长有利,同时圆形闭合且活跃的蘑菇圈在一定程度上抑制土壤真菌的发生。     

新疆巴音布鲁克草原白蘑蘑菇圈土壤真菌多样性分析

【背景】新疆巴音布鲁克草原为我国第二大高山草原,草原上生长的白蘑(Tricholoma mongolicum Imai)属于口蘑属(Tricholoma)的一种,可形成典型的蘑菇圈。【目的】了解巴音布鲁克草原白蘑蘑菇圈圈上及其两侧土壤真菌的物种组成和群落结构特点,为研究白蘑蘑菇圈的形成与生长及其子实体的发生提供一定的理论依据。【方法】采用Illumina HiSeq平台高通量测序技术研究白蘑蘑菇圈周围土壤真菌的物种组成丰富度和菌群结构多样性。【结果】测定有效序列经注释得到809个操作分类单元(Optical taxonomic unit,OTU),分为5个门、26个纲、79个目、166个科、232个属;蘑菇圈上土壤真菌的物种丰富度、群落结构多样性以及特异性物种均低于圈外及圈内,蘑菇圈上特有真菌物种为Xylodonnothofagi、Agaricales、Phaeococcomyces、Ochrocladosporium adansoniae、Coniochaeta ligniaria、未知子囊菌、 Tomentella amyloapiculata、 Dothideomycetes、Incertea_sedis_Helotiales。【结论】研究表明白蘑蘑菇圈的形成影响土壤真菌的分布,圈上优势真菌类群对其他真菌类群具有抑制作用,蘑菇圈向外生长可能与微生物群落结构失衡有关。     

内生真菌和丛枝菌根真菌对羊草生长的影响

该研究比较了摩西球囊霉(Glmous mosseae)和幼套球囊霉(Glmous etunicatum)两种丛枝菌根真菌和内生真菌单独及混合接种对羊草(Leymus chinensis)生长的影响。结果表明, 内生真菌对2种菌根真菌的侵染均无显著影响, 内生真菌可极显著增加羊草的分蘖数、地上生物量、总生物量。内生真菌与菌根真菌之间的相互作用因菌根真菌种类而不同, 幼套球囊霉对宿主植物生长无明显影响且和内生真菌之间也无明显的相互作用; 单独接种摩西球囊霉显著增加羊草的地上、地下和总生物量, 当其与内生真菌共同存在时, 二者之间存在一定的拮抗作用。冗余分析结果表明, 在内生真菌-AM真菌-羊草共生体中, 内生真菌对宿主植物生长的影响最大, 摩西球囊霉对宿主植物生长也有一定的贡献, 幼套球囊霉对宿主植物生长无明显影响。     

氮素和植物生长促进剂对羊草生长及竞争力的影响

选取羊草、斜茎黄芪、克氏针茅3种内蒙古典型草原常见植物,通过不同植物物种组合(单独种植或者羊草与其他两种混合种植)、施加不同剂量的氮素(0、0.1、0.2、0.4、0.8mg·g^-1)和植物生长促进剂——油菜素内酯(0.005 mg·g^-1)的温室盆栽试验,分析氮素和油菜素内酯对羊草生长及其与其他植物竞争力关系的影响.结果表明:添加氮素对羊草、斜茎黄芪的生物量影响显著,对克氏针茅的生物量影响较弱,并且氮素的影响因其伴生植物的不同而改变.氮素添加显著增加了羊草在单独种植和与斜茎黄芪混合种植时的地上生物量,但显著降低了与克氏针茅混合种植时的地下生物量.由于土壤可利用氮增加,羊草的地上与地下分配发生变化,表现为单独种植、与克氏针茅混合种植时,根冠比下降;与斜茎黄芪混合种植时,氮素添加对羊草根冠比的影响则不显著.油菜素内酯对植物生长的显著影响不普遍,仅显著降低了斜茎黄芪单独种植时的地下生物量;在羊草与斜茎黄芪混合种植时,显著增加了羊草地上生物量.油菜素内酯和氮适量联用可有效增加特定物种组合的生物量,从而在退化草地恢复中具有一定的应用前景.     

氮素对内蒙古典型草原羊草种群的影响

为了研究氮素对内蒙古典型草原植物种群的影响, 在中国科学院内蒙古草原生态系统定位研究站, 实施了长期的氮素添加试验。就两年来不同梯度氮素处理对羊草 (Leymuschinensis) 种群的影响进行了分析。结果表明, 氮素对羊草种群具有显著的调节效应, 随着氮素梯度的增加, 羊草种群密度、种群高度、地上生物量、地下生物量、总生物量均显著增加, 羊草种群地下生物量 /地上生物量比值逐渐降低。氮素对羊草种群构件的生物量分配有显著影响, 随着氮素梯度的增加, 羊草种群生物量向根茎的分配比例显著降低, 向叶片和根系的分配比例显著提高。羊草种群的相对密度和相对生物量也随着氮素梯度的增加而显著提高。     

不同邻居物种的基因型多样性对冷蒿生长的影响

植物物种多样性与基因型多样性对群落的结构和功能具有重要的生态作用,近年来植物基因型多样性对植物间相互作用的影响已成为研究者关心的重要科学问题。实验选择退化草原优势种冷蒿(Artemisia frigida)为目标植物,稳定群落建群种羊草(Leymus chinensis)和群落伴生种洽草(Koeleria cristata)为邻居植物,来研究基因型多样性不同的邻居植物对冷蒿生长表现(株高、地上生物量、地下生物量和总生物量)的影响,并通过测量植物相对竞争强度及邻居植物性状变异来进一步探究邻居植物基因型多样性对目标植物影响的内在机制。结果表明:(1)邻居物种为羊草时,基因型多样性对冷蒿的生长表现影响显著,当邻居为6基因型时,冷蒿的株高、地上生物量以及总生物量显著低于单基因型和3基因型时的表现(P0.05),且相对竞争强度高于其他两种处理;而邻居物种为洽草时,基因型多样性对冷蒿所有观测指标以及相对竞争强度的影响均不显著(P0.05)。(2)利用主成分分析法来分析基因型多样性对自身性状变异的影响发现,邻居物种为羊草时,基因型多样性对性状变异响应显著,主要表现为3基因型时,羊草种群的株高、总生物量、地上生物量显著高于单基因型时的表现(P0.05);而邻居物种为洽草时,基因型多样性对性状变异影响不显著(P0.05)。(3)邻居物种为羊草时,羊草总生物量和比叶面积与冷蒿的地上生物量和总生物量呈显著负相关(P0.05);邻居物种为洽草时,洽草各性状与冷蒿性状间无显著相关性(P0.05)。实验结果揭示,基因型多样性对目标植物生长的效应受邻居植物种类的影响,稳定群落建群种羊草高基因型组合能显著抑制冷蒿的生长,这可能与羊草高基因型多样性种群性状变异大且对冷蒿有较高的相对竞争强度有关。所得结果为建群种基因型多样性影响种间相互作用提供了实验证据,为草原的合理利用和保护提供了理论指导。     

黄绿蜜环菌蘑菇圈生长对土壤及植物群落的影响

通过调查青海省祁连县峨堡乡野生黄绿蜜环菌蘑菇圈发生季节蘑菇圈上、圈外植物群落的物种多样性、植物群落种类组成及多度变化 ,分析了蘑菇圈上、圈外土壤主要微生物类群的数量变化、土壤水分、速效养分、交换性阳离子及pH等的差异。结果表明 ,蘑菇圈上和圈外植物群落组成种类不同 ,圈上物种数明显高于圈外物种数 ;圈上各物种分盖度总和比圈外高出 4 9 .16 % ,但圈上和圈外优势种及主要伴生种相同。在 0～ 10cm土壤层 ,圈上土壤含水量、速效磷、硝态氮、氨态氮的含量明显高于圈外 ,但土壤有机质、交换性Ca2 + 、交换性Mg2 + 和pH值的变化不明显 ;在 10～ 2 0cm土壤层 ,圈上速效磷、硝态氮、氨态氮的含量仍明显高于圈外 ,但土壤含水量变化趋势相反 ,圈外高于圈上。在 0～ 10cm土壤层 ,细菌、放线菌、真菌及纤维素分解菌的数量 ,均以圈上显著高于圈外 (P <0 . 0 5 ) ;在 10～ 2 0cm土层 ,它们的数量差异不显著 (P <0 . 0 1)。在两层土壤中 ,各类微生物数量表现为 :细菌 >放线菌 >真菌 >纤维素分解菌。     

松嫩草原黄墩蚁对羊草群落组成与生物量的影响

研究了松嫩草原土壤动物优势类群黄墩蚁对羊草群落和羊草 虎尾草群落组成及生物量的影响。结果表明,黄墩蚁改变了其生境中的植被组成,两群落中的羊草密度增大,结穗率降低,但重量增加。受其影响,羊草和虎尾草的高度明显较大,地上生物量和地下生物量明显增加。     

Stability of ecosystem properties in response to above-ground functional group richness and composition

While there has been a rapidly increasing research effort focused on understanding whether and how composition and richness of species and functional groups may determine ecosystem properties, much remains unknown about how these community attributes affect the dynamic properties of ecosystems. We conducted an experiment in 540 mini‐ecosystems in glasshouse conditions, using an experimental design previously shown to be appropriate for testing for functional group richness and composition effects in ecosystems. Artificial communities representing 12 different above‐ground community structures were assembled. These included treatments consisting of monoculture and two‐ and four‐species mixtures from a pool of four plant species; each plant species represented a different functional group. Additional treatments included two herbivore species, either singly or in mixture, and with or without top predators. These experimental units were then either subjected to an experimentally imposed disturbance (drought) for 40 d or left undisturbed. Community composition and drought both had important effects on plant productivity and biomass, and on several below‐ground chemical and biological properties, including those linked to the functioning of the decomposer subsystem. Many of these compositional effects were due to effects both of plant and of herbivore species. Plant functional group richness also exerted positive effects on plant biomass and productivity, but not on any of the below‐ground properties. Above‐ground composition also had important effects on the response of below‐ground properties to drought and thus influenced ecosystem stability (resistance); effects of composition on drought resistance of above‐ground plant response variables and soil chemical properties were weaker and less consistent. Despite the positive effects of plant functional group richness on some ecosystem properties, there was no effect of richness on the resistance of any of the ecosystem properties we considered. Although herbivores had detectable effects on the resistance of some ecosystem properties, there were no effects of the mixed herbivore species treatment on resistance relative to the single species herbivore treatments. Increasing above‐ground food chain length from zero to three trophic levels did not have any consistent effect on the stability of ecosystem properties. There was no evidence of either above‐ground composition or functional group richness affecting the recovery rate of ecosystem properties from drought and hence ecosystem resilience. Our data collectively point to the role of composition (identity of functional group), but not functional group richness, in determining the stability (resistance to disturbance) of ecosystem properties, and indicates that the nature of the above‐ground community can be an important determinant of the consistency of delivery of ecosystem services.     

Biodiversity and belowground interactions mediate community invasion resistance against a tall herb invader

Aims Species-rich plant communities are hypothesized to be more resistant against plant invasions because they use resources in a more efficient way. However, the relative contributions of aboveground competition and belowground interactions for invasion resistance are still poorly understood.Methods We compared the performance of Knautia arvensis transplants growing in plots differing in plant diversity both under full competition and with shoots of neighbors tied back to determine the relative strength of aboveground competition in suppressing this test invader without the confounding effect of shading. In addition, we assessed the effects of belowground competition and soil-borne pathogens on transplant performance.Important findings Both aboveground competition and plant species richness strongly and independently affected invader performance. Aboveground biomass, height, leaf mass per area and flowering of transplanted individuals of K. arvensis decreased with increasing species richness of the host community. Species-rich and species-poor communities both imposed equally strong aboveground competition on K. arvensis. However, belowground interactions (especially belowground root competition) had strong negative effects on transplant performance. In addition, the presence of grasses in a plant community further reduced the performance of K. arvensis. Our results suggest that belowground competition can render species-rich host communities more suppressive to newly arriving species, thus enhancing community invasion resistance.     

灌丛化对黄土高原草地植物群落结构和地上生物量的影响

中国北方草地普遍出现灌丛化现象,灌丛化改变植物群落结构、植物多样性和生产力,直接影响着草地生态保护与可持续利用.该研究以黄土高原灌丛化草地为研究对象,通过植被调查,分析比较不同坡向的灌丛斑块与禾草斑块植物群落结构(物种组成、优势种及物种多样性)和地上生物量的差异.结果发现:(1)灌丛化草地不同坡向对物种多样性及地上生物...     

Trampling enhances the dominance of graminoids over forbs in flooded grassland mesocosms

Questions: What are the interactive effects of flooding and cattle trampling upon the structural attributes and the floristic composition of a plant community? Do the effects on the plant community persist over an extended recovery period? Location: Flooding Pampa grasslands, Argentina (36°30′ S, 58°30′ W). Methods: We assessed the effects of 40‐d of flooding, trampling and the combination thereof on plant cover and biomass, vertical distribution of foliage and floristic composition in lowland grassland mesocosms. We considered a 120‐d recovery period to evaluate the persistence of flooding and trampling effects on the plant community. Results: Flooding, with or without trampling, increased cover and biomass of the graminoid species, especially marsh grasses, which developed a taller canopy, whereas most of the forb species were negatively affected. This was enhanced by trampling, as the aerial biomass of the dominant legume Lotus tenuis decreased by 90%, while three major forb species disappeared. Trampling under flooding conditions did not reduce the total above‐ground biomass production, as the growth enhancement of graminoids was enough to compensate for the breakdown of the forbs. Below‐ground biomass was lower when both perturbations occurred simultaneously. After 120‐d of recovery, graminoids continued to be dominant while the remaining forbs (including L. tenuis) recovered only partially. Below‐ground biomass recovered fully at the end of the growing season. Conclusions: The combination of flooding and trampling shifts the community co‐dominance of graminoids and forbs towards a persistent dominance of graminoid species. When both perturbations are combined, the above‐ground production of the grassland is unaffected and root biomass is rapidly recovered. However, the loss of the legume L. tenuis deserves attention because this is the unique nitrogen‐fixing species of the ecosystem, which improves the forage quality for livestock production.     

Effects of shallow flooding on vegetation and carbon pools in boreal peatlands

Question: What are the effects of shallow flooding on boreal peatlands on vegetation composition and size of carbon pools in the living and dead vegetation? Location: Lake 979, Experimental Lakes Area, northwestern Ontario, Canada. Methods: A boreal basin peatland complex with treed bog, open bog, and open water was experimentally flooded by raising water level ca. 1.3 m. Vegetation and above‐ground biomass were compared between pre‐flood conditions and those nine years after flooding. Peat accumulation since flooding was also quantified. Results: Flooding caused almost all trees to die, leading to a net loss of 86% of the above‐ground living plant biomass after nine years of the flooding. Floating up of peat was rapid in the central part of the basin, and the floating peat mats were characterized by newly established open bog community. Wetland types were diversified from bog into open bog, fen, and marsh, accompanied with great species turnover. Floating open bog community accumulated the greatest amount of peat since flooding. Conclusions: This study shows that shallow flooding of bog vegetation can lead to quick re‐establishment of open bog vegetation upon the floating up of peat mats as well as changes to more diverse vegetation over decadal time spans. We estimate that the carbon pools in 2002 in living and dead plant biomass since 1992 are comparable to what they were in the above‐ground biomass in 1992. Flooding caused an initial net decrease in carbon stores, but carbon in the pre‐flood living plant biomass was replaced by both carbon in dead biomass of the pre‐flood vegetation and newly sequestered carbon in new peat growth and post‐flood living plant biomass. Possible vegetation change toward bog‐dominated system could lead to increasing rate of new peat growth, which could affect future carbon sink/source strength of the system.     

Interactive effects of grazing and shrubs on the annual plant community in semi‐arid Mediterranean shrublands

Question: We studied the interactive effects of grazing and dwarf shrub cover on the structure of a highly diverse annual plant community. Location: Mediterranean, semi‐arid shrubland in the Northern Negev desert, Israel. Methods: Variation in the biomass and plant density of annual species in the shrub and open patches was monitored during four years, inside and outside exclosures protected from sheep grazing, in two contrasting topographic sites: north and south‐facing slopes that differed in their dominant dwarf shrubs species: Sarcopoterium spinosus and Corydothymus capitatus, respectively. Results: Above‐ground biomass, density and richness of annual species were lower under the canopy of both shrub species compared to the adjacent open patches in the absence of grazing. Grazing reduced the biomass of annuals in open patches of both topographic sites, but not in the shrub patches. On the north‐facing slope, grazing also reduced plant density and richness in the open patches, but increased plant density in the shrub patches. At the species level, various response patterns to the combined effects of grazing and patch type were exhibited by different annuals. Protection against the direct impacts of grazing by shrub cover as well as species‐specific interactions between shrubs and annuals were observed. A conceptual mechanistic model explaining these interactions is proposed. Conclusion: In semi‐arid Mediterranean shrublands grazing and dwarf shrub cover interact in shaping the structure of the annual plant community through (1) direct impacts of grazing restricted to the open patches, (2) species‐specific facilitation/ interference occurring in the shrub patches and (3) subsequent further processes occurring among the interconnected shrub and open patches mediated through variation in seed flows between patches.     

Above‐ and below‐ground plant biomass response to experimental warming in northern Alaska

Question: Does experimental warming, designed to simulate future warming of the Arctic, change the biomass allocation and mycorrhizal infection of tundra plants? Location: High Arctic tundra near Barrow, Alaska, USA (71°18′N 156°40′W). Methods: Above and below ground plant biomass of all species was harvested following 3–4 yr of 1‐2°C of experimental warming. Biomass allocation and arbuscular mycorrhizal infection were also examined in the two dominant species, Salix rotundifolia and Carex aquatilis. Results: Above‐ground biomass of graminoids increased in response to warming but there was no difference in total plant biomass or the ratio of above‐ground to below‐ground biomass for the community as a whole. Carex aquatilis increased above‐ground biomass and proportionally allocated more biomass above ground in response to warming. Salix rotundifolia increased the amount of above‐ and below‐ground biomass allocated per leaf in response to warming. Mycorrhizal infection rates showed no direct response to warming, but total abundance was estimated to have likely increased in response to warming owing to increased root biomass of S. rotundifolia. Conclusions: The community as a whole was resistant to short‐term warming and showed no significant changes in above‐ or below‐ground biomass despite significant increases in above‐ground biomass of graminoids. However, the patterns of biomass allocation for C. aquatilis and S. rotundifolia did change with warming. This suggests that long‐term warming may result in changes in the above‐ground to below‐ground biomass ratio of the community.     

高寒小嵩草草原化草甸植物群落结构特征及其生物量

 小嵩草(Kobresia pygmaea)草原化草甸的主要植物有35种,隶属11科,30属。小嵩草为优势种,次优势种有异针茅(Stipa alliena)、美丽风毛菊(Saussurea superba)、紫羊茅(Festuca rubra)等;生活型以地面芽植物为主(65.71%),其次为地下芽植物(34.29%);地上、地下部分生物量垂直分布呈典型的金字塔模式。地上、地下生物量主要分布在0—10cm冠层和土层中,分别占地上、地下总生物量的91.79%和90.43%。每个植物类群生物量季节变化可由Logostic模型表示：Wi=ki/[1+exp(Ai-Bit)] 枯枝落叶生物量变化呈“V”型曲线。 在生长季各类群生物量绝对增长速率具明显的差异,平均每天每平方米可生产干物质2.79g,年地上净生产量为368.4g／m2。所固定太阳能值为6655.16kJ／m2,其中莎草类占35.10%,禾草类占23.33%,杂类草占34.15%,枯枝落叶占7.42%。光能利用率为0.1097%。     

Forage nutritive quality in the Serengeti ecosystem: the roles of fire and herbivory

Fire and herbivory are important determinants of nutrient availability in savanna ecosystems. Fire and herbivory effects on the nutritive quality of savanna vegetation can occur directly, independent of changes in the plant community, or indirectly, via effects on the plant community. Indirect effects can be further subdivided into those occurring because of changes in plant species composition or plant abundance (i.e., quality versus quantity). We studied relationships between fire, herbivory, rainfall, soil fertility, and leaf nitrogen (N), phosphorus (P), and sodium (Na) at 30 sites inside and outside of Serengeti National Park. Using structural equation modeling, we asked whether fire and herbivory influences were largely direct or indirect and how their signs and strengths differed within the context of natural savanna processes. Herbivory was associated with enhanced leaf N and P through changes in plant biomass and community composition. Fire was associated with reduced leaf nutrient concentrations through changes in plant community composition. Additionally, fire had direct positive effects on Na and nonlinear direct effects on P that partially mitigated the indirect negative effects. Key mechanisms by which fire reduced plant nutritive quality were through reductions of Na-rich grasses and increased abundance of Themeda triandra, which had below-average leaf nutrients.