Migration of Naphthalene through Low Organic Content Sandy Soil Columns: Comparison of Unsaturated and Saturated Conditions

The transient transport of naphthalene through low organic matter content soil columns was investigated in different water-saturation and flow conditions. Some parameters were tested as flow rate, column height, and water saturation conditions. The soil was a clayed sandy soil from the Algerian coast near Boumerdes. The organic carbon content was 0.13% and the main mineral components were quartz (88%), clays minerals (7%) and calcite (3%). The height of the packing of the soil column (5.1 cm in diameter) varied from 15 to 40 cm. Simultaneous step injections of inert tracer (calcium chloride) and naphthalene at 10 mg L^?1 were performed. Tracer and naphthalene breakthrough curves (BTCs) were measured continuously by conductimetry and UV – 220 nm, respectively. The BTCs were simulated using the classical mixing cells in series with exchange model (MCE). In unsaturated conditions the comparison of the mean residence time of tracer BTCs with the geometrical pore volume gave us access to average water saturation along the column as a function of height. The higher the soil bed was, the higher the mean water saturation. The comparison of naphthalene distribution coefficients (K_d) in different flow conditions with the theoretical value from the Karickhoff law showed that in saturated conditions the obtained value was close to the theoretical one. In unsaturated conditions, the measured naphthalene K_d's were much lower than the theoretical value and correlated to the water saturation.     

Adaptations for feeding on rock surfaces and sandy sediment by the fiddler crabs (Brachyura: Ocypodidae) Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758)

Two species of fiddler crab, Uca tetragonon(Herbst, 1790) and Uca vocans(Linnaeus, 1758), which belong to the subgenus Gelasimus, dwell on rocky shores and muddy–sandy tidal flats, respectively, in Phuket Is., Thailand. We investigated their feeding ecology in relation to the morphology of their feeding organs: minor food-handling chelipeds and maxillipeds. U. tetragononfed chiefly on rocks covered by filamentous green algae. U. vocansfed on the emerged sand and in shallow water along the shoreline and in pools. While feeding, both crabs made sand pellets beneath their mouthparts and discarded them, indicating that they divided the matter scooped up with their minor chelipeds into edible and inedible fractions by using the maxillipeds in the water passing through their buccal cavity. The morphology of maxillipeds hardly differed between the two species, which means that both species are flotation-feeders. The morphology of their minor chelipeds, however, differed: the tips of the dactyl and pollex were flat in U. tetragononand pointed in U. vocans.When the minor cheliped was closed, U. tetragononhad a hemispherical space in the distal one-fourth of the gape, which was closed by the framing keratin layers and a few setae of the dactyl and pollex. On the other hand, U. vocanshad an ellipsoidal space in the distal half of the gape. We consider these morphological characters to be adaptations to the different feeding substrates for retaining more food-laden sediment. We discuss the role of the setae on the minor chelipeds on the basis of the morphological differences between populations of U. tetragononin Phuket Is. and East Africa where the crab inhabits muddy–sandy tidal flats.     

沙化草地土壤碳氮磷化学计量特征及其对植被生产力和多样性的影响

沙化草地土壤碳(C)、氮(N)、磷(P)化学计量特征及其对植被生产力与多样性的影响对于认识草地沙漠化过程中土壤与植被的互馈关系,以及沙漠化发展的生态学机理具有重要的意义。通过对科尔沁沙地75个沙化样地的野外调查,研究了科尔沁沙地不同程度沙化草地的表层土壤C、N、P化学计量特征及其与生产力和多样性的相关关系。结果表明:1)科尔沁沙地沙化草地表层土壤具有较低的有机C、全N、全P含量及C∶N、N∶P和C∶P,平均值分别为1.39 mg/g、0.117 mg/g、0.079 mg/g和7.50、2.22、16.91;草地沙漠化过程中,土壤有机C、全N、全P含量显著降低的同时,C∶N、N∶P和C∶P亦显著降低,表明土壤有机C、全N、全P在沙漠化过程中的损失是不同步的;2)科尔沁沙地沙化草地表层土壤有机C、全N、全P元素间均呈显著正相关,具有一定的耦合关系,且土壤有机C和全P间的耦合关系不随沙漠化的发展而发生改变;3)草地沙化过程中,土壤养分的损失限制着草地生产力,而土壤N∶P较全N、全P含量更能反映土壤养分对生产力的限制作用;4)沙化草地土壤全N含量与物种丰富度间具有显著正相关关系,而土壤全P含量与其无显著相关性;多样性指数与全N、全P含量间均具有显著正相关关系;相对于土壤全N、全P含量,N∶P能更好地反映养分平衡对物种多样性的影响作用。     

Morphogenesis and Molecular Phylogeny of a Soil Ciliate Uroleptoides longiseries (Foissner,Agatha and Berger, 2002) Berger 2008 (Ciliophora,Hypotrichia)

Morphogenesis of the hypotrich ciliate Uroleptoides longiseries, isolated from sandy soil beside the Yellow River, Suide, Yulin, Shaanxi Province, China, was investigated using protargol staining. The main events during binary fission are as follows: (1) the long frontoventral row is formed by a single anlage; (2) five frontoventral‐transverse cirral anlagen are formed in primary mode; (3) only the posterior part of the parental adoral zone of the membranelles is renewed; and (4) the oral primordium of the opisthe is formed intrakinetally. This is the first detailed record of all stages of morphogenesis for Uroleptoides. We also provide the first record of the small subunit ribosomal DNA (SSU rDNA) sequences for U. longiseries. Phylogenetic analyses based on the SSU rDNA sequences data show that Uroleptoides longiseries clusters with U. magnigranulosa with moderate to high support which together form a clade with Orthoamphisiella breviseries. These three species share the morphogenetic feature of the long frontoventral row being formed by a single anlage.     

不同干扰强度生境中啮齿动物对苦槠种子的取食和扩散

在浙江省千岛湖地区,选择了受人类活动干扰较轻、中度和严重的3个生境,采用金属片标记法研究了啮齿动物对苦槠种子的取食和扩散.结果表明:在研究点捕获的取食种子的啮齿动物为针毛鼠( Niviventer fulvescens),尽管捕获的数量少,但种子被取食和扩散的速率很快,3个样地内的种子均在2d内被取食或扩散完毕;中等干扰强度的生境中,被就地取食的种子最多,占鉴别种子总数的37.8%.种子扩散距离大多<5m,最大扩散距离为24.76m,3个样地种子扩散均符合负指数分布,且样地间没有显著差异;饱满种子与虫蛀种子被就地取食与搬运后取食的命运没有显著差异,但饱满种子的最大扩散距离均显著大于虫蛀种子(P<0.05),除中等干扰样地中饱满种子与虫蛀种子平均扩散距离没有显著差异外,其余2个样地中饱满种子的平均扩散距离均显著大于虫蛀种子,显示啮齿动物对饱满种子与虫蛀种子有一定的区分能力.     

黄河首曲-玛曲县高寒草甸沙化演替进程中群落结构及种群生态位特征

以甘肃省玛曲县高寒沙化草甸为对象,应用空间序列代替时间序列的方法,对其不同沙化演替阶段植物群落主要种群结构及其生态位特征进行了研究.结果表明:(1)随着沙化演替的进行,物种组成数呈单峰式曲线变化规律,在轻度沙化阶段物种数最多(43种),禾草类和豆科类物种的重要值和生态位宽度均呈逐渐减少规律,优势度逐渐减弱;在极度沙化阶段(除垂穗披碱草外)几乎完全消失,莎草类和杂类草一些物种的重要值和生态位宽度则均呈逐渐增大规律,优势度逐渐增加,并在重度或极度沙化阶段成为优势种、次优势种或重要伴生种;随沙化演替进程,蒲公英、狼毒和乳白香青等物种则表现出波动性,最后消失,物种组成和数量的变化导致沙化演替进程中高寒草甸草场质量逐渐降低.(2)相邻沙化演替阶段植物群落的物种组成相似性指数较高,而相距较远的沙化演替阶段植物群落的物种组成相似性指数较小,沙化演替系列两个极端阶段的植物群落的物种组成相似性指数最小.(3)垂穗披碱草在整个沙化演替过程中重要值和生态位宽度均逐渐减小,但其值都较大.(4)生态位总宽度占前5位的物种依次是:垂穗披碱草、莓叶委陵菜、矮嵩草、高山唐松草和苔草,其值分别为1.653、1.438、1.387、1.295和1.204.(5)种群之间生态位重叠系数的平均值随沙化程度加深呈单峰式曲线变化规律,轻度沙化阶段种群的生态位重叠程度较高,为0.824.     

氮添加对沙质草地氨挥发及硝态氮淋溶的影响

采用密闭室法和离子交换树脂袋法,研究了科尔沁沙质草地不同处理(水添加、氮添加、水氮添加)氧挥发的损失量和硝态氮的淋溶量.结果表明:氮添加处理和水氮添加处理显著促进了氨挥发(P＜0.05),最大氨挥发速率显著高于对照;氮添加处理和水氮添加处理的氨挥发累积量为111.80和148.64 mg·m-2,分别占氮添加量的1.1％和1.5％;水氮同时添加条件下,氨挥发累计量显著高于氨添加处理(P＜0.05),水添加处理和对照相比没有显著差异(P＞0.05);水氮添加处理显著增加了土壤深度20 cm处的硝态氮淋溶量(P＜0.05),氮添加处理和水氮添加处理的硝态氮淋溶量分别是对照的1.96和4.22倍,然而在土壤深度40 cm处各处理硝态氮淋溶量差异不显著(P＞0.05);可见,氮添加和水氮添加均促进了土壤的氧挥发,对硝态氮的淋溶没有显著影响.     

不同抚育措施对闽西毛竹林碳密度、碳贮量与碳格局的影响

以闽西永安市Ⅰ（挖笋+劈草+施肥+灌水)、Ⅱ(挖笋+劈草+施肥)、Ⅲ（挖笋+劈草)3种不同抚育措施的毛竹林为对象,对其碳密度、碳贮量及碳格局进行了研究。结果表明：毛竹各器官碳密度变动范围为0.3947～0.5619 g·g^-1,碳密度高低排序为竹鞭＞竹秆＞竹枝＞竹蔸＞竹叶＞竹根＞鞭根;不同竹龄间竹秆、竹枝、竹叶、竹根碳密度存在极显著差异（P<0.01）,而竹蔸碳密度差异不显著（P＞0.1）;随着竹龄增加,毛竹平均碳密度有下降趋势,1～6年毛竹平均碳密度为0.4579～0.4957 g·g^-1。Ⅰ、Ⅱ和Ⅲ类毛竹林毛竹层碳贮量分别为76.74、64.30和55.91 t·hm^-2;凋落物层碳贮量分别为2.59、3.01和4.88 t·hm^-2;土壤层碳贮量分别为150.64、197.36和232.56 t·hm^-2;总碳贮量分别为227.37、261.66和288.47 t·hm^-2,其中土壤层碳贮量所占比例最高,分别为66.25%、75.43%和80.62%,毛竹层碳贮量比例分别为32.61%、23.43%和17.69%,凋落物层碳贮量比例分别为1.14%、1.15%和1.69%。毛竹生物器官中,竹秆固碳能力最强,占年总固碳量比例为56.47%～59.66%,鞭根的固碳能力最弱,占年总固碳量的比例仅为2.52%～2.83%;毛竹林年固碳量排序为Ⅰ类型＞Ⅱ类型＞Ⅲ类型。