不同水位梯度下克隆植物大米草的生长繁殖特性和生物量分配格局

通过温室模拟控制实验,研究了不同水位梯度处理对外来克隆植物大米草(Spartina anglica) 衰退种群的形态性状、克隆生长性状、生物量积累及生物量分配格局的影响.实验共设置5种水位处理,分别为淹没至大米草株高的1/2, 淹没至株高的1/3,表面水淹0 cm,低于土表5 cm (-5 cm),以及低于土表10 cm (-10 cm).结果表明:水位梯度对大米草的形态性状、克隆生长性状、生物量的积累与分配格局等部分指标均有显著影响(p < 0.05);株高、克隆分株数、根状茎节数、根状茎总长、间隔子长度及生物量在0 cm至1/3株高水位梯度处理下均显著高于-10 cm和1/2株高水位处理(p < 0.05),但与-5 cm处理无显著差异(p > 0.05);-10 cm水位处理的地上生物量分配和根状茎生物量分配显著低于其它处理(p < 0.05).综合大米草衰退种群的形态特征、克隆生长特性、生物量积累及分配格局对水位处理的响应格局,认为大米草种群较适宜的水位梯度为表面积水至淹没株高的1/3处,而水位的变化可能是大米草种群自然衰退的原因之一.     

多菌灵处理对克隆植物大米草(Spartina anglica)表型可塑性的影响

对外来植物大米草(Spartina anglica)衰退种群进行高、中、低3个浓度(即50%多菌灵可湿性粉剂的300倍、600倍和1200倍稀释液)多菌灵灌根处理,测定大米草在杀菌剂处理条件下的形态可塑性、克隆生长特性及生物量积累与分配格局.结果表明:与对照相比,各浓度多菌灵处理对大米草的株高、叶数、叶片厚度、叶片面积和根长均没有显著影响(P〉0.05);中浓度处理后,大米草种群的根状茎节数和分枝强度均显著高于对照和其它处理,而根状茎总长和间隔子长度均显著高于对照和低浓度处理(p<0.05),与高浓度处理差异不显著;高浓度处理的大米草地下生物量和根生物量分配显著高于对照和其它处理,而地上生物量分配却显著低于对照和其它处理(P相似文献   

咸淡交替灌溉对克隆植物大米草生长繁殖和生物量分配的影响

通过温室模拟控制实验,研究了咸淡交替灌溉处理对外来克隆植物大米草(Spartina anglica)形态性状、克隆生长、生物量积累及分配格局的影响。实验共设6种浇灌处理:单一淡水灌溉(D)、单一咸水浇灌(X)、淡咸交替灌溉(DX)、咸淡交替灌溉(XD)、淡咸淡交替灌溉(DXD)和咸淡咸交替灌溉(XDX)。结果表明:DX处理条件下,大米草株高、叶片数及根长均达到最高;克隆数最多,且显著高于X、DXD和XDX处理;芽数及根状茎总长均显著大于XDX处理;在DX和D处理下,地上生物量、根系生物量、地下生物量和总生物量均显著高于其它处理。这表明作为滨海盐沼植物,大米草种群比较适应淡咸水交替环境,单一的咸水,以及过度的咸淡转换均不利于大米草的生长繁殖与生物量积累,而淡咸水交替过程的失序可能是引起我国大米草种群衰退的重要原因。     

初始克隆分株数对大米草表型可塑性及生物量分配的影响

克隆植物大米草 (Spartina anglica) 目前在我国出现了严重的自然衰退 (Dieback),为了阐明大米草衰退的机理,分析影响大米草形态可塑性的因素与自然衰退之间的相关性,以期为近缘植物互花米草 (S. alterniflora) 这一爆发种群的生物控制提供借鉴,对3种不同初始克隆分株数 (单克隆、三克隆和五克隆) 大米草的克隆生长、生物量累积与分配和异速生长特征进行了野外栽培试验。研究结果表明,初始克隆分株数对间隔子长度影响较弱;初始多克隆的分支强度高于初始单克隆;初始三克隆和五克隆在总生物量 (7.921 5~10.431 7 g 和 8.903 9~10.431 7 g)、地上生物量 (3.396 1~4.255 8 g 和3.618 4~4.338 9 g)、地下生物量 (4.286 9~5.206 6 g 和 5.298 8~6.079 3 g)和根状茎生物量 (1.318 6~1.767 7 g 和 1.499 1~2.038 7 g) 积累上均显著高于初始单克隆,不同初始克隆分株数条件下根生物量差异不显著;初始多克隆倾向于将资源更多地分配给根状茎,而初始单克隆倾向于将更多的资源分配给根系。由此推断,在不同初始克隆分株数条件下,大米草的形态可塑性和生物量分配格局的差异显示出在同样资源格局下,初始多克隆的克隆生殖能力较初始单克隆强。初始多克隆生长的大米草较初始单克隆生长的大米草更能占据优势生境,选择生境“觅养”的能力与克隆繁殖能力更强。     

不同生境下假臭草生长特征分析

通过测定庄稼地、弃耕地、桉树林、公路边4种生境下假臭草叶面积(LA)、比叶面积(SLA)、LDMC和株高等形态特征、植株各构件生物量及生物量分配比和假臭草种群盖度、密度等种群数量性状,研究不同生境类型下假臭草个体的形态特征、生物量及生物量分配和种群生长状况的差异。结果表明:光照和土壤养分对假臭草的形态特征、生物量及生物量分配和种群数量性状的影响显著;低光照、高土壤养分生境下假臭草的LA、SLA、株高较高,假臭草叶片的LDMC较小,植株的花序数较少,生物量主要向叶和茎器官进行分配,根和花果器官的生物量分配则受到限制;高光照、养分贫瘠生境下假臭草的LA、SLA、株高较低,假臭草叶片的LDMC较大,生物量主要向根和花果器官进行分配,种群的盖度、密度、生物量和高度等种群数量性状较低,种群生长状况较差;高光照、肥沃养分生境为假臭草的最适生境,假臭草构件的资源配置较为优化,株高、基径粗、冠宽和花序数等形态指标较大,种群盖度、密度、生物量等种群数量性状较大,种群生长较好。     

不同水盐条件对三江藨草生长和生物量分配的影响

水、盐条件是盐沼生态系统最重要的环境因子,直接影响着植物的生长和繁殖。以莫莫格湿地优势植物三江藨草（Scirpus nipponicus）为研究对象,探究不同水盐条件及其交互作用对湿地植物三江藨草功能性状和生物量分配格局的影响,以期加深对湿地盐渍化背景下内陆盐沼植物生态适应对策的了解,为指导湿地水盐管理和植被生态恢复提供基础数据。实验采用室内模拟控制水盐条件的方法,设置盐度（300、1000、2000、3000、4000 mg/L和5000 mg/L）和水位（-10,0,20,40,60 cm和80 cm）各6个梯度处理,结果表明,三江藨草株高变化仅受水位处理的影响（P<0.05）,随水位的升高株高呈现先增加后下降的趋势;株数变化仅受盐度处理的影响,并且受水位的限制,适宜盐度能促进浅水域植株分株数增加;水位、盐度和二者的交互作用对三江藨草生物量积累及其分配均产生显著影响,随着水位和盐度的升高,三江藨草球茎、地下、地上和单株总生物量均呈先增加后降低的趋势;生物量分配受水盐交互作用较明显,在1000、2000 mg/L和3000 mg/L盐度处理时,随着水位升高球茎生物量分配和地下生物量分配增加,地上生物量分配减少。综合三江藨草的生长特征和生物量累积,认为其在40-80 cm水位和1000-3000 mg/L盐分处理环境中生长状态较好,适宜的盐分处理可以增加三江藨草对水深的耐受程度。     

光强对比度对大米草克隆整合作用的影响

通过温室控制试验,分析不同光强及光强对比度处理下克隆植物大米草生长性状的差异,研究同质异质光强条件下克隆整合对大米草响应遮阴能力的修饰作用.结果表明： 在同质条件下,大米草在无遮阴(高光强：温室内自然光照强度)条件下的生物量显著大于中度遮阴(中光强：光照强度为高光强的70%)和深度遮阴(低光强：光照强度为高光强的30%).在低对比度异质性光强条件下(分株对的一个分株不遮阴,另一个分株中度遮阴),大米草遮阴分株的叶片数、根长和生物量均显著高于同质中度遮阴处理,而无遮阴分株各生长指标与同质无遮阴处理相比均无显著差异.因此,在低对比度异质性光强下,大米草受体(遮阴)分株通过克隆整合显著受益;同时,对供体(非遮阴)分株没有显著的耗损.然而,在高对比度处理下(分株对的一个分株不遮阴,另一个分株深度遮阴),克隆整合对受体(遮阴)分株的效应不显著.大米草的克隆整合并不随着光强对比度的增加而增加.在自然生境中度遮阴情况下,克隆整合可以提高大米草的生长和克隆繁殖能力,但在深度遮阴情况下,克隆整合对大米草适应性的作用可能很小.     

秦王川湿地盐角草和盐地碱蓬种群的空间格局及其关联性

植物种群的空间格局及关联性是植物种群生态学特性对环境条件长期适应和选择的结果。在秦王川国家湿地公园盐沼湿地,利用群落学调查法和点格局分析法,按照盐角草(Salicornia europaea)植株密度依次设置高密度Ⅰ(800株·m~(-2))、中密度Ⅱ(400~800株·m~(-2))和低密度Ⅲ(400株·m~(-2))3个密度梯度样地,分析了盐角草和盐地碱蓬(Suaeda salsa)种群的空间格局及其关联性。结果表明:随着盐角草植株密度的减小,其植株高度和地上生物量呈逐渐减小的趋势(P0.05),盐地碱蓬的植株高度和地上生物量呈逐渐增大的趋势(P0.05);盐角草在样地Ⅰ和Ⅲ中呈不同尺度的聚集分布,聚集尺度由较小尺度向小尺度过渡,在样地Ⅱ中所有尺度上呈聚集分布;盐地碱蓬在样地Ⅰ所有尺度上呈聚集分布,在样地Ⅱ和Ⅲ的聚集分布由较小尺度向中尺度过渡;在样地Ⅰ中,盐角草和盐地碱蓬之间表现为负相关和不相关(P0.05),在样地Ⅲ中表现为不相关,在样地Ⅱ中从负相关过渡到正相关(P0.05)。湿地植物密度调控机制影响下的非对称竞争关系,引起群落优势物种发生更替,反映了植物适应环境变化的生活史策略。     

葎草种群自疏过程中幼苗构件性状及生物量分配变化

以雌雄异株攀援草本植物葎草为材料,通过每10 d测量1次,连续6次,测定幼苗期葎草种群的密度和高度、个体构件性状和生物量分配等参数,分析种群自疏过程中种群密度与个体构件性状及生物量分配的关系,研究葎草种群的自疏规律。结果表明:幼苗期葎草种群存在显著的自疏现象,种群密度60 d内下降了71%;幼苗期葎草由直立生长向横向生长时,种群密度和株高显著降低;自疏过程中存留植株的茎性状有显著变化,变化大小为节间长主茎长茎直径,节间长增加,叶性状变化大小为叶面积叶柄长叶厚叶宽叶长总叶数保留叶片数,根性状变化大小为总根长根体积根数根长最大根长;自疏过程中存留植株的构件生物量、单株生物量显著增加,而单位面积累积生物量呈阶段性下降;留存植株的地上生物量分配比相对稳定(P0.05),根茎比和叶茎比有极显著变化(P0.01);叶、茎、叶柄生物量与根生物量和地上生物量之间均呈极显著的异速关系(P0.01),茎随地上生物量增长呈等速生长,而叶、叶柄和根随地上生物量增长呈异速生长,地上生物量与叶、茎、叶柄及根生物量极显著相关(P0.01);茎生物量与密度的异速关系遵循最终产量恒定法则,叶、叶柄和根生物量并不满足-3/2或-4/3或-1自疏法则;地上和单株总生物量与密度极显著相关(P0.01),存留单株的地上生物量和总生物量与密度的异速关系遵循最终产量恒定法则。     

海草形态、生长的种间差异及其相关生长关系

海草是海洋沉水高等植物,属典型的根茎克隆植物.根状茎直径和分株重分别是其个体大小的第一、二表征指标,个体大小是海草重要的种间识别特征.对海草6个形态构件指标和18个生长指标的综合分析表明:果实大小、单株叶面积、分株重具有显著的种特异性;分株发出的时间差、水平根状茎分枝率、叶年产量、分株寿命和垂直茎分枝率是海草种特异性最强的5个生长动态指标,海草生长动态的差异主要体现在克隆生长能力强弱和分株生活史长短上;大海草趋于游击型克隆构型,而小海草则趋于密集型,但小海草Cymodocea nodosa例外;大海草基株水平扩展能力较小海草差.海草个体大小与生长特征的相关生长关系表明:随个体的增大,海草在有机构件生长上表现出两相邻叶、相邻分株、相邻节发出的时间差延长,分株、叶、茎寿命延长的特点;在克隆生长水平上表现出根状茎节间长变短、延伸速率降低,分枝率和根状茎上年产分株数降低,分枝角度变小和间隔子增大的趋势;在克隆片段水平上表现为生理整合性增强;在种群层面则表现出生物量增大和种群密度降低的特点.因此,海草个体大小对其形态、生长特征、克隆构型、种群密度和生产力起到了决定作用.大小海草不同的形态、生长动态和克隆构型特征导致它们的生存策略及生态功能也不同,这一点可能对海草场修复基础理论研究具有一定的指示作用.     

Biophysical and morphological leaf adaptations to drought and salinity in salt marsh grasses

Leaf energy budgets were constructed for 13 species of estuarine C₄ grasses (Poaceae) to elucidate the biophysical effects of drought and salinity on the interception and dissipation of solar energy. Spartina alterniflora, S. anglica, S. argentinensis, S. bakeri, S. cynosuroides, S. densiflora, S. foliosa, S. foliosa × S. alterniflora hybrids, S. gracilis, S. patens, S. pectinata, S. spartinae, and Distichlis spicata plants were grown under controlled soil water potential gradients in a greenhouse. Species were grouped into four major ecological functional types, based on elevational zonation ranges: low marsh species, middle marsh species, high marsh species, and freshwater species. Different functional types are adapted to different environmental conditions, and responded differently to reduced water potentials. Latent heat flux decreased similarly across species in response to decreasing water potential. Latent heat loss was found to decrease by as much as 65% under decreasing water potential, leading to an increase in leaf temperature of up to 4 °C. Consequently, radiative and sensible heat losses increased under decreasing water potential. Sensible heat flux increased as much as 336% under decreasing water potential. Latent heat loss appeared to be an important mode of temperature regulation in all species, and sensible heat loss appeared to be more important in high marsh species compared to low marsh species. High marsh species are characterized by narrower leaves than middle and low marsh species, leading to a smaller boundary layer, and providing higher conductance to sensible heat loss. This may be an adaptation for high marsh species to regulate leaf temperature without access to large amounts of water for transpirational cooling. Stomatal conductance decreased with decreasing water potential across species: leaf conductances to water vapor and CO₂ decreased as much as 69% under decreasing water potential. Additionally, oxidative stress appeared to increase in these plants during times of drought or salinity stress. Ascorbate peroxidase activities increased with decreasing soil water potential, indicating increased cellular reactive oxygen species. High marsh species had higher ascorbate peroxidase activities compared to low marsh species, indicating higher tolerance to drought- or salinity-induced stresses. It was concluded that different species of marsh grasses are adapted for growth in different zones of salt marshes. Adaptations include biophysical, biochemical, and morphological traits that optimize heat exchange with the environment.     

黄河三角洲滨岸潮滩湿地碱蓬对水沙条件及氮输入的适应性

调水调沙工程的实施为黄河三角洲带来大量淡水恢复退化湿地的同时,也改变了湿地的水沙状况并带来大量的外源物质。本研究采用3因素4水平的正交试验,以黄河口滨岸潮滩湿地典型的先锋物种碱蓬为研究对象,探讨了其对淹水深度、泥沙埋深及外源氮输入的适应机制。结果表明: 泥沙埋深对碱蓬叶片蛋白含量及超氧化物歧化酶(SOD)活性的影响较大;氮输入对过氧化物酶(POD)活性的影响较大,而3种处理对过氧化氢酶(CAT)活性的影响无显著差异。淹水深度对叶、茎及总干重具有显著影响,且随淹水深度的增加呈现减小趋势,最大值(25.70、40.86、69.73 g)均出现在2 cm淹水处理;而氮输入及泥沙埋深对碱蓬干重的影响不显著。极差分析表明,淹水深度对碱蓬叶、茎、根及总干重的影响最为显著,其次为氮输入和泥沙埋深,2 cm淹水深度+12 cm埋深深度+9 g·m^-2氮输入量最有利于碱蓬的生长。可见,淹水深度的变化对碱蓬的生长起到决定性的作用,在调水调沙等工程的实施过程中应注重淹水深度的把控。     

The sediment burial depth and salinity control the early developments of Suaeda salsa in the Yellow River Delta

Sediment deposition is a common phenomenon in the estuary area. Pot control experiments were conducted to evaluate the interaction effects of sediment burial depth and salt stress on the seed germination and early seedling growth of Suaeda salsa (L.) Pall., an pioneer species of tidal wetland near the Yellow River Delta. The results showed that the percentage of seedling emergence, seedling emergence rate, seedling height, branch number, shoot biomass and root biomass were all significantly affected by salt stress and sediment burial depth. While the interaction of salt and burial depth significantly influenced the branch number, leaf biomass, shoot biomass and total plant biomass. Only 5 cm burial depth without salt stress should 6.25 ± 3.61% seedlings emergence. With the increasing of sediment burial depth and salt stress, percentage of seedling emergence, seedling emergence rate and plant height decreased significantly. However, under the salt treatment of 0 and 1%, the branch number increased dramatically with the increasing of sediment burial depth from 0 to 3 cm. The ratio of leaf to total biomass increased with increasing of burial depth, on the contrary, the ratio of root to total biomass decreased. 0–1 cm sediment burial depth was proved the suitable depths for seed germination of S. salsa in the coastal wetland of the Yellow River Delta. Our findings contribute to a better understanding of how to improve the seedling establishment of S. salsa under the dynamic changes of sediment deposition and salinity in the coastal wetland of the Yellow River Delta.     

小叶锦鸡儿幼苗对沙埋的生态适应和生理响应

以中国半干旱地区固定、半固定沙地分布最广泛的灌木种之一小叶锦鸡儿(Caragana microphylla)为对象,于2010～2011年在内蒙古科尔沁沙地测定了不同深度沙埋下其幼苗的存活率、株高、渗透调节物质含量、保护酶活性和膜透性变化,探讨小叶锦鸡儿对沙埋的生理响应特征。结果显示:(1)与对照相比,当沙埋深度为小叶锦鸡儿幼苗株高的25%～75%时,存活率差异不显著;当沙埋深度为50%～75%时其存活率增加,但株高明显下降,沙埋对其生长具有抑制作用;当沙埋达到其株高100%时幼苗全部死亡。(2)不同沙埋深度对小叶锦鸡儿幼苗叶片细胞膜透性无显著影响,对沙埋深度为其株高25%时,叶片含水量增加,MDA含量下降,POD活性增强,细胞膜未受到伤害;沙埋深度为其株高50%～75%时,叶片含水量下降,MDA含量增加,但SOD和POD对细胞膜起到了协同保护作用,细胞膜也未受到损伤;沙埋深度为株高25%～75%情况下,细胞膜未受到损伤,可溶性糖和脯氨酸含量变化不明显。研究认为:小叶锦鸡儿幼苗只能耐受部分沙埋,完全沙埋则会导致其幼苗全部死亡,沙埋胁迫下可溶性糖和脯氨酸等渗透调节物质含量反应迟缓可能是其耐沙埋能力较弱的主要生理原因之一。     

胶州湾滨海湿地土壤有机碳时空分布及储量

在胶州湾选取芦苇、碱蓬、光滩及大米草4种典型滨海湿地类型,分季节和层次采集土壤样品,测定土壤有机碳含量,分析滨海湿地土壤有机碳的时空分布及储量.结果表明: 垂直方向上,除光滩湿地沿剖面呈先减小后稍有上升的趋势外,其他湿地均随土壤深度的增加而减小;水平方向上,湿地土壤有机碳含量表现为大米草湿地>光滩湿地>碱蓬湿地>芦苇湿地;季节上,湿地土壤有机碳含量表现为春季>夏季>秋季>冬季.土壤有机碳含量与土壤含盐量、含水率、TN及C/N呈正相关,与土壤容重、pH值呈负相关.不同类型湿地土壤剖面有机碳密度表现为光滩湿地>芦苇湿地>碱蓬湿地,湿地类型对土壤有机碳含量和有机碳密度分布的影响存在一定差异.因储碳层厚度及储碳层内有机碳密度的差异,光滩湿地单位面积有机碳储量明显高于碱蓬和芦苇湿地,具有较大的储碳潜能,对研究区滨海湿地起到一定的碳汇作用.     

Effects of burial and erosion on the seagrass Zostera noltii

The effects of experimental burial and erosion on the seagrass Zostera noltii were assessed through in situ manipulation of the sediment level (− 2 cm, 0 cm, + 2 cm, + 4 cm, + 8 cm and + 16 cm). Shoot density, leaf and sheath length, internode length, C and N content and carbohydrates of leaves and rhizomes were examined 1, 2, 4 and 8 weeks after disturbance. Both burial and erosion resulted in the decrease of shoot density for all the sediment levels. The threshold for total shoot loss was between 4 cm and 8 cm of burial, particularly during the 2nd week. A laboratory experiment confirmed that shoots did not survive more than 2 weeks under complete burial. There was no evidence of induced flowering by burial or erosion. As well, no clear evidence was found of sediment level effects on leaf and sheath length. Longer rhizome internodes were observed as a response to both burial and erosion, suggesting a plant attempt to relocate the leaf-producing meristems closer to sediment surface or in search of new sediment avoiding the eroded area. The C content of leaves and rhizomes, as well as the non-structural carbohydrates (mainly the starch in rhizomes), decreased significantly along the experimental period, indicating the internal mobilization of carbon to meet the plant demands as a consequence of light deprivation. The significant decrease of N content in leaves, and its simultaneous increase in rhizomes, suggests the internal translocation of nitrogen from leaves to rhizomes. About 50% of the N lost by the leaves was recovered by the rhizomes. Our results indicated that Z. noltii has a high sensitivity to burial and erosion disturbance, which should be considered in the management of coastal activities.     

土埋深度影响物种水平的种子质量-种子出苗关系

种子出苗对种间关系和群落组成具有重要影响。种内研究表明种子质量与种子出苗之间存在正相关关系, 但这种关系很少在物种水平进行检验, 尤其是在不同土壤埋藏深度条件下。为此, 该文开展了一个因子实验(10种植物和5种土埋深度(0、1、2、4和8 cm))以检验是否在不同土层中“种子质量-种子出苗之间的正相关关系”始终存在。该文在不同土埋深度播种50粒种子(重复5次), 连续30天观测种子出苗, 并提出了一个耐土埋性指标。结果表明: (1) 10种植物的最适出苗深度为0-2 cm土层; 6种植物的最大出苗率发生在1 cm土埋深度。(2)种子质量与耐土埋性之间存在显著的正相关关系, 种子质量越大耐土埋性越强, 适宜出苗的土层越深。(3)当土层较深(4或8 cm)时, 种子出苗率和持续出苗时间随种子质量增加而增大, 种子出苗率与持续出苗时间之间存在正相关关系; 这些关系在较浅土层(0、1或2 cm)并不存在。这些结果有助于进一步理解种子大小与出苗之间的关系, 以及种子出苗过程中的策略。     

互花米草入侵下湿地土壤碳氮磷变化及化学计量学特征

为阐明外来物种入侵对生态系统的改变,对闽江河口区本土植物短叶茳芏和不同入侵年限的互花米草湿地土壤总碳(TC)、总氮(TN)、总磷(TP)含量进行了测定与分析.结果表明: 互花米草入侵后0～50 cm深度各层土壤TC、TN和TP含量均有不同程度的增加,其中TC、TN的变化比较一致,而TP的变化滞后;TC的增加引起土壤C/N持续增加,而TP是调节互花米草入侵过程中湿地土壤C/P和N/P的关键因子,C/P和N/P的变化基本一致.土壤TC、TN、TP的变化受到土壤盐度、容重、含水量和黏粒组成的影响,而它们之间计量比主要受土壤盐度、粒径组成的影响;C/N和C/P对互花米草湿地的土壤固碳效应具有良好的指示作用.互花米草入侵引起生物量和湿地生境改变,导致土壤碳氮磷含量及其生态化学计量比发生显著变化,且随入侵时间延长表现出不同的变化特征.     

闽江河口互花米草不同入侵阶段湿地土壤nirK型反硝化微生物群落结构及多样性

为了明确闽江河口互花米草海向不同入侵阶段湿地土壤nirK型反硝化微生物的群落结构及多样性,在鳝鱼滩东部的互花米草分布区,由陆向海方向选择互花米草海向入侵前的光滩(MF)、入侵1～2年(SAN)和入侵6～7年的互花米草(SA)湿地为研究对象,基于高通量测序技术,测定并分析了不同互花米草入侵阶段湿地土壤nirK型反硝化微生物群落结构及多样性的差异。结果表明:互花米草海向入侵降低了土壤中nirK型反硝化微生物群落的多样性及丰富度。不同入侵阶段湿地土壤的nirK型反硝化微生物主要包括变形菌门和放线菌门,其中变形菌门占绝对优势地位。互花米草海向入侵整体改变了湿地土壤中nirK型反硝化菌属的组成特征,MF、SAN、SA湿地土壤中相对丰度最高的nirK基因菌属分别为慢生根瘤菌属、中慢生根瘤菌属和产碱杆菌属。互花米草海向入侵增加了土壤中nirK型反硝化微生物群落组成的空间异质性,尤其是在SAN样地,这主要与样地本身的环境扰动性较大及互花米草海向入侵加大了样地环境因子的空间异质性有关。互花米草海向入侵主要是通过显著改变土壤理化因子(粒度组成、pH值和含水量)和氮养分条件(全氮、NH₄⁺-N、NO₃^--N)来影响nirK型反硝化微生物的群落结构及多样性。本研究结果有助于揭示互花米草海向入侵对湿地土壤反硝化过程影响的微生物机制。     

Resolving the differences in plant burial responses

Burial is one of the major factors influencing plant ecology in deserts and coastal areas. Consequently, many studies have measured the responses of dune plants to sand burial. However, there remains little agreement about the mechanisms and characteristics constituting the burial response of plants. In particular, stimulation of growth has been reported as the most common plant burial response; however, stimulation has not been reported consistently among studies. Here, a literature survey showed that the depth of burial relative to the height of the plant determined whether the growth of a species was stimulated by burial. Growth stimulation was limited to shallow burial depths, while burial depths greater than the height of the plant consistently resulted in reduced growth. As studies used widely differing burial depths or units of growth measurement, the variation in reported stimulation of plant growth can be partly attributed to differences in experimental procedure. The stimulation of growth in many species was accompanied by an increase in photosynthesis over a limited period and by a shift in biomass allocation from root to shoot. Most plants demonstrated stimulated growth (up to 200%) in response to shallow burial indicating that some burial response mechanisms are general to many species. However, a few specialist dune species displayed a much greater ability to respond to burial (up to 700% stimulation of plant mass). Although allocation shifts and increased photosynthesis have been shown to be associated with dune plant burial response, there remains a need for field measurements that focus on the diversity of mechanisms underlying plant response to burial.