Morphology, biometry and distribution of Difflugia biwae Kawamura, 1918 (Protozoa : Rhizopoda)

The freshwater testate amoeba Difflugia biwae Kawamura, 1918, isolated from Mulan Lake, Hubei Province, China is investigated using light microscopy and scanning electron microscopy. The morphology, biometry and distribution of this little known species are supplied. After careful comparison with three other similar species, including D. delicatula Gauthier-Livre et Thomas, D. elegans Penard and D. oblonga caudata Stepanek, we believe that the characteristics of smooth fusiform shell, conspicuous great collar flare (always larger than body-width) around the aperture, constriction behind the aperture and a somewhat curved aboral horn set D. biwae apart from all other Difflugia species. This species shows a great diversity in total length, collar height and aboral horn length which have high variability (CV between 11.76 and 24.52). However, body width, collar diameter, neck width, body length and aperture diameter are fairly constant with low variability (CV between 5.34 and 8.79) which shows a remarkable uniformity of D. biwae. Also, the size frequency distributions of both body width and body length yield bell-shaped (normally distributed) curves and indicate that D. biwae is a size-monomorphic species, characterized by a main-size class and a small size range. D. biwae is probably endemic to East Asia (China and Japan) because it has such a large size (165-306 mu m) that it would have been easily found in Europe and North America, if it were there. Consequently, D. biwae must have a restricted geographical distribution, disproving the old hypothesis that microscopic organisms are cosmopolitan.

Difflugia mulanensis nov spec., a freshwater testate amoeba from Lake Mulan, China

Testate amoebae are an important and abundant component of aquatic ecosystems. Our knowledge of their distribution and the species inventory in Asia is still limited. This paper describes a new planktonic Difflugia from Lake Mulan, province of Hubei, China. These findings are of taxonomic, as well as biogeographic significance because Difflugia mulanensis nov. spec. is a rare and perhaps the only locally distributed member of the well-known urceolate division within this most species-rich genus of lobose testate amoebae. We have studied its morphology and biometry with light and scanning electron microscopical methods. D. mulanensis differs from related species by its very large wide funnel-shaped apertural collar which normally exceeds the width of the test, a relatively long neck, its rounded apical end and the presence of only one nucleus. All shell parameters are normally distributed with low variability. Only the collar height is more variable. This shows that D. mulanensis is a size-monomorphic species. (c) 2005 Elsevier GrnbH. All rights reserved.

Redescription of Difflugia tuberspinifera Hu, Shen, Gu et Gong, 1997 (Protozoa : Rhizopoda : Arcellinida : Difflugiidae) from China

The freshwater testate amoeba Difflugia tuberspinifera Hu et al. 1997 collected from pond and lake in China, is investigated by light and scanning electron microscopy. This little known taxon is redescribed and its morphology, biometry and ecology are supplied. After carefully comparison with other six similar species including Difflugia bartosi Stepanek, D. corona Wallich, D. corona cashi Deflandre, D. corona tuberculata Vucetich, D. muriformis Gauthier-Lievre et Thomas and Netzelia tuberculata (Wallich) Netzal we believe that the sub-spherical to spherical shell, the mulberry-shaped appearance, the 7-10 apertural tooth-like structures, the short collar and the conical spines numbering from 4 to 8 at the upper equatorial region in D. tuberspinifera set it apart from other species. Besides, statistical analysis indicates that D. tuberspinifera is a size-monomorphic species characterized by a main-size class and a small size range and the shell height is significant correlated with other morphometric characters at p < 0.05 excepting the number of aperture tooth-like structures and the number of spines. Moreover, D. tuberspinifera inhabits not only lotic but also lentic environment.

涡动相关法估算森林生产力及与测树学方法的比较

大气中CO2、CH4和其它温室气体浓度升高导致的全球气候变化引起了人们对全球碳循环和碳收支的关注，植被与大气间CO2通量的长期测定能够加深对陆地生态系统在全球碳循环作用的科学理解。本文以我国北方典型的温带植被类型长白山阔叶红松林为研究对象，利用观测塔上的涡动相关系统对长白山阔仆卜红松林进行长期的CO2通量监测，并分析CO2通量的周年动态，估算森林净生态系统生产力；同时基于测树学方法，进行群落调查，根据已有的经验公式，估算森林净生态系统生产力，综合评价长白山阔汗卜红松林碳收支，为森林碳收支的研究提供基础。主要结论有：（1）FSAM模型的分析结果表明，观测塔上40m高度的涡动相关仪器测量的信息中，76％来自于西北至西南方相对均质的阔叶红松原始林，其中footprint最大的源区在塔西南方100m-400m范围内。因此，森林群落调查选择在此区内进行，使得涡动相关法和测树学方法估算的生产力具有可比性。（2）2003-2004年碳通量季节变化趋势基本一致，从年初到4月上旬该森林生态系统保持较弱的正的碳通量（释放CO2），5月开始表现为净的碳吸收，且吸收量迅速增加，到6月达到最大值，然后又逐渐减小；9月末到10月末随着生长季的结束，净生态系统COZ交换（NEE）开始由负转为正，11-12月NEE为正，生态系统以呼吸为主。净生态系统COZ交换的年累计量表明长白山阔叶红松林为明显的碳汇，2003年和2004年净生态系统生产力NEP分别为-217±75gcm-2a-1和-190±85gcm-2a-1，相当于-2.17±0.75tCha-1a-1和-1.90±0.85tCha-1a-1。（3）根据经验公式和材积法得到阔汗卜红松林的生物量在343．9-362．3tha－l之间，应用两种方法得到2003一2004年群落的净初级生产力在10.22-10.40tCha-1a-1之间，净生态系统生产力在2.50±1.12tCha-1a-1-2.68±1.20tCha-1a-1之间。（4）测树学方法与涡动相关法测得的净生态系统生产力略有差异，但在误差有效范围内基本一致。