三种盐胁迫对互花米草和芦苇光合作用的影响

互花米草(Spartina alterniflora)的入侵给海岸带盐沼生态系统的结构和功能带来了显著影响。互花米草盐沼中的硫含量高于附近的土著芦苇(Phragmites australis)盐沼。为探讨硫元素对互花米草和芦苇竞争过程的可能影响及其作用机制, 以50 mmol·L^-1的Na₂SO₄和Na₂S对互花米草和芦苇进行处理, 分析处理前后5天内两种植物光合气体交换和叶绿素荧光指标变化的差异, 实验另设等Na⁺浓度的NaCl处理作为比较。研究发现: Na₂S对互花米草和芦苇光合作用影响的差异最大, NaCl次之, Na₂SO₄最小。Na₂S处理后, 互花米草净光合速率(P_n)出现显著上升, 芦苇P_n值大幅度下降。互花米草的光饱和点(I_sat)上升而芦苇的I_sat值无变化。表明Na₂S处理对互花米草的光合能力有促进作用, 但对芦苇的光合能力有抑制作用。NaCl处理后互花米草P_n值也出现小幅上升, 而芦苇P_n值略有下降。Na₂SO₄处理对互花米草和芦苇的P_n值均无显著影响。除Na₂SO₄处理的互花米草外, 不同盐处理后的互花米草和芦苇非光化学淬灭(NPQ)均出现上升趋势。研究结果表明互花米草对环境硫胁迫的适应能力显著高于芦苇, 暗示盐沼高硫环境尤其是硫化物有助于互花米草相对于芦苇的竞争, 也很可能是其形成单一植被的重要原因之一。     

凋落物去除和氮添加对亚热带阔叶林土壤不同组分碳、氮的影响

人类活动显著增加了氮沉降,对森林生态系统产生了不同程度的影响;凋落物在其分解过程中输入的大量有机碳、氮也会影响土壤碳氮的形成、稳定及转化.本研究选择亚热带常绿阔叶林,对样地进行8年氮添加[对照(0)、低氮(75 kg·hm^-2·a^-1)、高氮(150 kg·hm^-2·a^-1)]和控制凋落物处理(保留凋落物、去除凋落物),之后采集土壤样品,通过K₂SO₄、Na₂B₄O₇、Na₄P₂O₇、NaOH、H₂SO₄、Na₂S₂O₄、HF等化学试剂逐级浸提土壤,测定各浸提液和残渣中的碳、氮含量,研究凋落物及氮添加对土壤矿物结合态碳、氮的影响.结果表明: 整体上,胡敏素(humin,H)组分的土壤碳、氮含量均为最高,分别占土壤全量的33.5%和33.3%.Na₂B₄O₇溶液提取的土壤可溶性碳、氮含量最高,其次是NaOH和Na₄P₂O₇溶液,3种试剂提取的土壤可溶性总碳、可溶性总氮以及可溶性有机氮分别占提取总量的46.2%、47.9%和76.5%.与对照相比,氮添加增加了Na₂S₂O₄和H组分碳、氮含量;与保留凋落物比较,去除凋落物降低了Na₂B₄O₇、H₂SO₄、Na₂S₂O₄和H组分的碳含量,以及NaOH、HF和H组分的氮含量.保留凋落物和氮添加显著增加了K₂SO₄组分氮含量.可见,保留凋落物和外源氮通过影响化学稳定性不同的土壤组分的碳氮变化来改变土壤碳氮过程.     

不同盐碱类型胁迫对红地球/贝达葡萄植株离子分布的影响

以盆栽红地球/贝达葡萄为试材,定量浇灌NaCl、Na₂SO₄、NaHCO₃、NH₄Cl和(NH₄)₂SO₄,筛选导致葡萄叶片黄化的盐、碱离子,研究不同盐碱类型胁迫对葡萄植株离子分布的影响.结果表明： NaHCO₃对植株影响最大,叶片在处理14 d时出现黄化症状,而NaCl和NH₄Cl处理28 d时出现黄化症状.NaHCO₃和NaCl处理均显著增加了植株各器官中Na^+含量,NaHCO₃处理根中Na⁺含量是对照的 6.4倍;这两种盐处理均降低了除叶片外其他器官中的K⁺含量,NaHCO₃处理显著降低了各器官中K/Na,根中K/Na仅为0.1,NaCl处理降低了除茎外其他器官中K/Na;这两种盐处理还降低了Ca²⁺、Mg²⁺、Fe²⁺向地上部的运输.NH₄Cl、(NH₄)₂SO₄和Na₂SO₄处理降低了植株各器官中K/Na,以NH₄Cl处理显著.碱性盐NaHCO₃对葡萄叶片黄化影响最大,其次是中性盐NaCl,再次是NH₄Cl,而(NH₄)₂SO₄和Na₂SO₄影响较小.     

青藏高原4类典型水化学特征湖泊的细菌多样性差异及影响因素

青藏高原分布着我国最密集的极端环境湖泊群, 湖泊类型和水化学特征多样, 而不同类型湖泊的细菌群落组成与多样性差异的系统研究相对较少。本文以青藏高原4类典型水化学特征湖泊(即氯化物型、MgSO₄亚型、Na₂SO₄亚型、碳酸盐型)为研究对象, 借助Illumina测序16S rRNA基因(V₃‒V₄区)分析细菌多样性、群落组成差异及其优势属与环境因素的制约关系。结果表明: MgSO₄亚型与氯化物型湖泊多属于超盐环境, 而大多数Na₂SO₄亚型与碳酸盐型湖泊属于咸水、微咸水或淡水环境。4类湖泊获得分类地位明确的细菌共计45门81纲1,148属(52,031个OTUs), 细菌Shannon指数为碳酸盐型(5.27 ± 0.57) > Na₂SO₄亚型(4.96 ± 0.51) > 氯化物型(4.12 ± 0.80) > MgSO₄亚型(3.64 ± 1.04)。优势细菌门是变形菌门、厚壁菌门和拟杆菌门。变形菌门的相对多度总体较高, 优势纲是γ-、α-和β-变形菌纲; 厚壁菌门多分布于MgSO₄亚型和氯化物型湖泊, 优势纲是芽孢杆菌纲; 拟杆菌门主要分布于碳酸盐型和Na₂SO₄亚型湖泊, 优势纲是黄杆菌纲。全部氯化物型和少数MgSO₄亚型湖泊的细菌组成相似, 优势属是假单胞菌属(Pseudomonas)、乳球菌属(Lactococcus)和不动杆菌属(Acinetobacter), 其聚集分布与总盐度、主要离子(Mg²⁺、Cl^-、Na⁺与K⁺)和温度相关; MgSO₄亚型湖泊独有的常见属是芽孢杆菌属(Bacillus)、气单胞菌属(Aeromonas)、大洋芽孢杆菌属(Oceanobacillus)等, 其聚集分布与SO₄ ^2-浓度正相关; Na₂SO₄亚型与碳酸盐型湖泊的细菌组成相似, 优势属是水弯曲菌属(Aquiflexum)、海仙菌属(Haliea)与苍黄杆菌属(Luteolibacter), 其聚集分布与HCO₃ ^-浓度、pH值和海拔高度呈显著正相关。与世界上其他湖泊组/群相比, 青藏高原湖泊具有独特的细菌优势属和常见属, 不同类型湖泊的细菌群落组成存在显著差异, 可能与水化学类型或地理位置有关。     

响应面法优化fHBP-A蛋白双水相萃取工艺的探究

目的 采用双水相萃取技术对重组B群脑膜炎奈瑟菌H因子结合蛋白A(fHBP-A)进行分离纯化,研究不同双水相萃取体系对fHBP-A粗提纯化的影响,应用响应面法优化fHBP-A在PEG/(NH₄)₂SO₄双水相体系中的萃取工艺。方法 首先建立PEG 2 000/(NH₄)₂SO₄、PEG 4 000/(NH₄)₂SO₄、PEG 6 000/(NH₄)₂SO₄和乙醇/(NH₄)₂SO₄ 共4种双水相萃取体系相图;然后考察PEG相对分子质量、PEG质量分数、(NH₄)₂SO₄质量分数、萃取体系pH这4个因素对fHBP-A萃取率、下相中fHBP-A纯度的影响;最后采用Box-Behnken试验设计以及响应面...     

盐碱胁迫下外源硫化氢对裸燕麦叶片氮代谢和产量构成因素的影响

为探讨外源信号硫化氢(H₂S)对盐碱胁迫下裸燕麦(Avena nuda)氮代谢的调控机制及产量构成因素的影响,采用盆栽土培试验,以‘定莜9号’品种为材料,设置盆土不添加盐碱和添加3.00 g·kg^-1盐碱(摩尔比NaCl∶Na₂SO₄∶Na₂CO₃∶NaHCO₃=12∶8∶1∶9)与抽穗期喷水和喷50μmol·L^-1 H₂S供体硫氢化钠(NaHS)溶液,共4个处理。喷施3 d后分别在第7天和第14天取叶片检测氮代谢相关物质含量和关键酶活性,成熟期调查产量构成因素及产量。结果表明：(1)喷施后第7天,盐碱胁迫显著降低裸燕麦叶片氨态氮、硝态氮、可溶性蛋白质含量和蛋白酶、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)、谷氨酸脱氢酶(GDH)、谷草转氨酶(GOT)、谷丙转氨酶(GPT)活性,对游离氨基酸含量和硝酸还原酶(NR)活性无显著影响;喷施NaHS溶液使盐碱胁迫下裸燕麦叶片氨态氮、游离氨基酸...     

追踪韩国白垩纪恐龙海岸

2012年8月,第11届“中生代陆地生态系统学术会议”（MTE2012）在韩国光州举行,这是该学术会议第一次在韩国举行。会后的野外考察地点为韩国的白垩纪恐龙海岸,以恐龙足迹化石点为主,这些化石点正在联合中请世界自然遗产。在三天的野外考察中,     

盐胁迫对藜麦种子萌发的影响研究

再生水资源可浇灌农田,但水中含有的阴离子可使土壤产生盐胁迫。为研究盐胁迫对藜麦(Chenopodium quinoa)种子萌发特性及胚根、胚芽生长的影响,该研究以6个藜麦品种(红藜麦、国红藜麦、台红藜麦、台紫红藜麦、黄藜麦、台黄红藜麦)为材料,分别以NaCl、Na₂SO₄、NaHCO₃和对照(CK)处理6个藜麦品种种子,测定其发芽率、胚根、胚芽抑制率等指标,运用均方差决策法对不同藜麦品种耐盐性进行综合评价,初步筛选出不同盐胁迫下耐盐性较强的品种。结果表明：(1)三种盐胁迫中,Na₂SO₄对种子萌发指标抑制作用最明显,6个藜麦品种的发芽率均相对较低,一直保持在5%以下,除黄藜麦、台黄红藜麦,其余4个品种的活力指数和生长速率均为0,除黄藜麦外,Na₂SO₄ 对其余5个藜麦品种的胚根、胚芽抑制率均达到100%;NaCl对种子萌发和生长的抑制作用较小,甚至可促进胚根和胚芽生长,国红藜麦和台黄红藜麦的生长速率在NaCl处理下始终高于对照,在9 ...     

混合盐碱胁迫对小白菜种子萌发的影响

用不同浓度的NaCl、Na₂SO₄、NaHCO₃和Na₂CO₃混合液对小白菜(Brassica chinensis L.)种子进行种子萌发试验,观察小白菜种子在不同浓度盐碱胁迫下的发芽率和发芽指数。结果表明,在混合盐碱胁迫下,小白菜种子的发芽率、发芽势、发芽指数和活力指数均随pH值增大和盐浓度的升高呈下降趋势,且各萌发指标与盐浓度的相关系数明显大于pH值,可见小白菜种子发芽受盐浓度的影响更大。低浓度(50mmol·L^-1)盐碱胁迫对小白菜种子萌发影响不大,高浓度(200mmol·L^-1)盐碱胁迫下小白菜的种子萌发受到严重影响。     

影响恐龙足印化石形成的若干外界条件

在博物馆里展出的很多恐龙化石已被大家所熟悉 ,但恐龙足印化石却鲜为人知 ,这是因为恐龙足印化石的形成过程复杂 ,形成条件极为苛刻。爬行动物足印化石同其它足印化石一样是动物的遗迹 ,这就区别于骨骼等实体化石。实体化石可经受一定的风吹雨淋 ,而足印化石则很容易受到地表侵蚀而消失。所以 ,足印化石的形成一般认为需要具备以下几个条件 :(一 )要有适于脚印形成的地方。大多数的足印都保留在泥质或沙质岩石上 ,这就意味着足印形成在含水丰富松软适当的地带。一般来讲 ,松软的湖岸或海岸是形成足印的理想场所。 (二 )需要有适当的时间。…     

Footprints pull origin and diversification of dinosaur stem lineage deep into Early Triassic

The ascent of dinosaurs in the Triassic is an exemplary evolutionary radiation, but the earliest phase of dinosaur history remains poorly understood. Body fossils of close dinosaur relatives are rare, but indicate that the dinosaur stem lineage (Dinosauromorpha) originated by the latest Anisian (ca 242-244 Ma). Here, we report footprints from the Early-Middle Triassic of Poland, stratigraphically well constrained and identified using a conservative synapomorphy-based approach, which shifts the origin of the dinosaur stem lineage back to the Early Olenekian (ca 249-251 Ma), approximately 5-9 Myr earlier than indicated by body fossils, earlier than demonstrated by previous footprint records, and just a few million years after the Permian/Triassic mass extinction (252.3 Ma). Dinosauromorph tracks are rare in all Polish assemblages, suggesting that these animals were minor faunal components. The oldest tracks are quadrupedal, a morphology uncommon among the earliest dinosauromorph body fossils, but bipedality and moderately large body size had arisen by the Early Anisian (ca 246 Ma). Integrating trace fossils and body fossils demonstrates that the rise of dinosaurs was a drawn-out affair, perhaps initiated during recovery from the Permo-Triassic extinction.     

内蒙古查布地区下白垩统巨齿龙足印化石

内蒙古鄂尔多斯市鄂托克旗查布地区下白垩统中产有大量的蜥脚类和兽脚类恐龙足迹及鸟类足迹化石,作者对这个地区的足迹化石进行全面普查,发现许多新暴露出来的恐龙足迹化石,包括兽脚类恐龙足迹一新属新种Chapuslockleyiichnogen.etichnosp.nov.属于巨齿龙类(megalosaurid)所留。与兽脚类足迹保存在一起的蜥脚类足迹Brontopodusbirdi分布凌乱,反映了造迹恐龙搏斗的场面。通过测量连续的兽脚类足迹计算,Chapuslockleyi的造迹恐龙的行走速度为4.33km/h。通过足迹化石还识别出造迹恐龙的病态特征。     

Dinosaur Tracks from the Kilmaluag Formation (Bathonian,Middle Jurassic) of Score Bay,Isle of Skye,Scotland, UK

Tracks of a juvenile theropod dinosaur with footprint lengths of between 2 and 9 cm as well as adults of the same ichnospecies with footprints of about 15–25 cm in length were found in the Bathonian (Middle Jurassic) Kilmaluag Formation of Score Bay, northwestern Trotternish Peninsula, Isle of Skye, Scotland, UK. Two footprint sizes occur together on the same bedding plane in the central portion of Score Bay, both in situ and on loose blocks. Another horizon containing footprints above this was also identified. The footprints from the lowest horizon were produced in a desiccated silty mud that was covered with sand. A close association of both adults and juveniles with similar travel direction indicated by the footprints may suggest post-hatching care in theropod dinosaurs. Other footprints, produced on a rippled sandy substrate, have been found on the slightly higher bedding plane at this locality. Loose blocks found 130 m to the northeast in the central part of Score Bay have not been correlated with any in situ sediments, but were preserved in a similar manner to those from the higher bedding plane. These tracks represent the youngest dinosaur remains yet found in Scotland.     

Sauropod and Small Theropod Tracks from the Lower Jurassic Ziliujing Formation of Zigong City,Sichuan, China,with an Overview of Triassic–Jurassic Dinosaur Fossils and Footprints of the Sichuan Basin

A dinosaur footprint assemblage from the Lower Jurassic Ziliujing Formation of Zigong City, Sichuan, China, comprises about 300 tracks of small tridactyl theropods and large sauropods preserved as concave epireliefs (natural molds). The theropod footprints show similarities with both the ichnogenera Grallator and Jialingpus. Three different morphotypes are present, probably related to different substrate conditions and extramorphological variation. A peculiar preservational feature in a morphotype that reflects a gracile trackmaker with extremely slender digits, is the presence of a convex epirelief that occurs at the bottom of the concave digit impressions. It is possibly the result of sediment compaction underweight load when the pes penetrated the substrate, being a resistant residue during exhumation and weathering. The sauropod tracks belong to a trackway with eight imprints consisting of poorly preserved pes and manus tracks and a better preserved set, probably all undertracks. The narrow-gauge trackway pattern resembles the ichnogenus Parabrontopodus well known from the Jurassic but other features such as the minor heteropody are different. The assemblage enriches the dinosaur record from the famous Zigong locality and the evidence from the Lower Jurassic in this area that was restricted to a few skeletal remains and footprints. Furthermore it proves the presence of small theropods, whereas skeletons of the group, well- known from the Middle-Upper Jurassic of Zigong, are of medium to large size only. Remarkable is the dominance of saurischians in these assemblages, which is characteristic of Jurassic dinosaur communities whereas the Cretaceous record shows an increase of ornithopod groups. An overview of the dinosaur trace and body fossil record of the Sichuan Basin supports this view. The paleoenvironment can be designated as a low-latitude tropical freshwater lake as it is indicated by bivalve shells.     

Human Tracks from Quaternary Tufa Deposits,Cuatro Cienegas,Coahuila, Mexico

In 1961, two human footprints were excavated from the Cuatro Cienegas region of Coahuila, Mexico, but for decades were not studied scientifically or deposited in any museum. Consequently, knowledge of the locality where they were found was lost. Once the two tracks were relocated they found their way to the Museo del Desierto, Saltillo (Coahuila) where they were placed on display with a tentative label suggesting an early Holocene age (10,000 B.C.). This inference was based only on the known antiquity of humans in the region determined from previous archaeological work and two dated sediment cores close to the footprint site. It was not until 2006 that the presumed footprint discovery site was rediscovered, revealing more than 20 additional well-preserved prints, in at least four trackways representing several different individuals with foot lengths ranging from about 23–27 cm. The tracks include one well-preserved trackway providing step and stride measurements. A poorly preserved cervid trackway and a possible duck footprint have also been identified. The footprints are preserved in hard tufa. Geochemical evidence suggests the tracks were made during periods of increased aridity.     

Diverse Dinosaur-Dominated Ichnofaunas from the Potomac Group (Lower Cretaceous) Maryland

Until recently fossil footprints were virtually unknown from the Cretaceous of the eastern United States. The discovery of about 300 footprints in iron-rich siliciclastic facies of the Patuxent Formation (Potomac Group) of Aptian age is undoubtedly one of the most significant Early Cretaceous track discoveries since the Paluxy track discoveries in Texas in the 1930s. The Patuxent tracks include theropod, sauropod, ankylosaur and ornithopod dinosaur footprints, pterosaur tracks, and miscellaneous mammal and other vertebrate ichnites that collectively suggest a diversity of about 14 morphotypes. This is about twice the previous maximum estimate for any known Early Cretaceous vertebrate ichnofauna. Among the more distinctive forms are excellent examples of hypsilophodontid tracks and a surprisingly large mammal footprint. A remarkable feature of the Patuxent track assemblage is the high proportion of small tracks indicative of hatchlings, independently verified by the discovery of a hatchling-sized dinosaur. Such evidence suggests the proximity of nest sites. The preservation of such small tracks is very rare in the Cretaceous track record, and indeed throughout most of the Mesozoic.

This unusual preservation not only provides us with a window into a diverse Early Cretaceous ecosystem, but it also suggests the potential of such facies to provide ichnological bonanzas. A remarkable feature of the assemblage is that it consists largely of reworked nodules and clasts that may have previously been reworked within the Patuxent Formation. Such unusual contexts of preservation should provide intriguing research opportunities for sedimentologists interested in the diagenesis and taphonomy of a unique track-bearing facies.     

Constructing and testing hypotheses of dinosaur foot motions from fossil tracks using digitization and simulation

Whilst bones present a static view of extinct animals, fossil footprints are a direct record of the activity and motion of the track maker. Deep footprints are a particularly good record of foot motion. Such footprints rarely look like the feet that made them; the sediment being heavily disturbed by the foot motion. Because of this, such tracks are often overlooked or dismissed in preference for more foot-like impressions. However, the deeper the foot penetrates the substrate, the more motion is captured in the sediment volume. We have used deep, penetrative, Jurassic dinosaur tracks which have been naturally split into layers, to reconstruct foot motions of animals living over 200 million years ago. We consider these reconstructions to be hypotheses of motion. To test these hypotheses, we use the Discrete Element Method, in which individual particles of substrate are simulated in response to a penetrating foot model. Simulations that produce virtual tracks morphologically similar to the fossils lend support to the motion being plausible, while simulations that result in very different final tracks serve to reject the hypothesis of motion and help generate a new hypothesis.     

Unusual deinonychosaurian track morphology (Velociraptorichnus zhangi n. ichnosp.) from the Lower Cretaceous Xiaoba Formation,Sichuan Province,China

A new Lower Cretaceous dinosaur footprint locality named the Mujiaowu tracksite in the Xiaoba Formation, Sichuan Province, has yielded a new assemblage containing the didactyl deinonychosaurian ichnogenus Velociraptorichnus. This is the eleventh report in the global record, the seventh from Asia and the fifth from China. All, except for an isolated report from Europe, occur in Lower Cretaceous deposits. Unlike previous reports of the ichnogenus, the Mujiaowu site has yielded both didactyl Velociraptorichnus tracks and tridactyl tracks which we interpret as a different expression of this same ichnogenus, caused by registration of digit II, either due to special substrate conditions or to less claw retraction. These tridactyl Velociraptorichnus footprints are assigned to the new ichnospecies Velociraptorichnus zhangi. Such tridactyl deinonychosaurid footprint morphology is predictable, but based on current ichnological evidence appears to be the exception rather than the rule.     

Dinosaur Footprints from the Lower Cretaceous Sarten Member of the Mojado Formation at Cerro de Cristo Rey,Dona Ana County,New Mexico

Dinosaur tracks and swimming traces have been discovered at three localities in the latest Albian Sarten Member of the Mojado Formation, Bisbee Group (= “Anapra Sandstone”), at Cerro de Cristo Rey in Sunland Park, southernmost Dona Ana County, New Mexico. These localities preserve footprints of ornithopod (Caririchnium) and theropod (Magnoavipes) dinosaurs, ?reptilian swimming traces and possible tracks of an ankylosaurian dinosaur. The Sarten Member is of the latest Albian age, so the Cerro de Cristo Rey tracks are slightly younger than the well-known late Albian tracksites of northeastern New Mexico. At Cerro de Cristo Rey, the dominance of ornithopod tracks and absence of sauropod tracks fit regional patterns of late Albian-early Cenomanian track distribution consistent with North American extirpation of sauropods before the end of Albian time. The deltaic/coastal plain depositional setting of the Sarten Member is also remarkably similar to the track-bearing late Albian-Cenomanian sandstones of NE New Mexico, Oklahoma, Nebraska, and SE Colorado, which also have a tetrapod footprint ichnofacies dominated by ornithopod (Caririchnium) and theropod (Magnoavipes) tracks throughout the so-called “dinosaur freeway.”     

Los Cayos Dinosaur Tracksite: An Overview on the Lower Cretaceous Ichno-Diversity of the Cameros Basin (Cornago,La Rioja Province,Spain)

The Los Cayos dinosaur tracksite is located at the eastern sector of the Cameros Basin (Cornago Township, La Rioja province), NE Spain. The sediments consist of interbedded terrigenous siliciclastics and carbonates belonging to the Enciso Group (Early Cretaceous, Aptian in age). The sedimentological and faunal evidence suggests that these sediments were deposited in a low gradient lacustrine environment. Los Cayos constitutes a relatively wide area with at least 6 localities that have yielded dinosaur tracks. More than 2,000 dinosaur tracks have been discovered to date. Medium to large theropod dinosaurs constitute about 95% of the ichnofauna. Ornithopod dinosaur tracks have been reported from only one of the outcrops (Los Cayos D). Los Cayos S has yielded theropod and sauropod tracks. One sauropod trackway shows a narrow-gauge locomotion pattern and a manus print morphology suggesting that the trackmaker was a titanosaurid, or at least a titanosauriform sauropod. Some pterosaur manus impressions, avian-like footprints of small size and possible turtle tracks complete the assemblage of one of the most impressive and best-preserved dinosaur tracksites of the European Lower Cretaceous.