A new medium-sized species of Hippodonta (Bacillariophyceae) is described from Lake Qinghai, China. The morphology and ultrastructure of Hippodonta qinghainensis sp. nov. are described using light and scanning electron microscopy. This new species is compared with similar species of Hippodonta using conventional and geometric morphometric analyses. Hippodonta qinghainensis can be separated from the other species of Hippodonta by a unique combination of characters that include an elliptic-lanceolate to rhombic-lanceolate valve shape, non protracted apices, the absence of fascia, relatively coarse, uniseriate striae and the presence of two rows of lineolae around the valves apices.
The morphology and ultrastructure of Gyrosigma peisonis var. major var. nov., a new variety of Gyrosigma peisonis found in Lake Qinghai (China), are described here on the basis of light and scanning electron microscopy. Most of the morphological features of this new variety are identical to those of the nominal variety Gyrosigma peisonis var. peisonis, but the variety major differs in its distinctly larger cell size and its higher value for the longitudinal/transverse stria density ratio, however. The seasonal variation of this taxon, which was investigated by a sediment-trap study is also discussed.
We examined the long-term dynamics of plant biomass of Filifolium sibiricum steppe, Stipa baicalensis steppe and Leymus chinense) (syn. Aneurolepidium chinense) steppe relative to interannual variation of precipitation and temperature during 1981-1990 in the Tumugi, Xingan League, eastern Inner Mongolia of China. On the average, annual precipitation was 41.1 cm. Peak live aboveground biomass (PLAB) was 152 g m -2 for E sibiricum steppe and S. baicalensis steppe and 162 g m -2 for L. chinense steppe. Peak live belowground biomass (PLBB) varied between 968 g m -2 for E sibiricum steppe and 1022 g m -2 for L. chinense steppe. The coefficient of variation (CV) in annual precipitation (25%) was lower than the CV in PLAB (35% to 37%) but larger than the CV in PLBB (10%) of the three meadow steppe sites. Rain use efficiency was 3.6 gDM m -2 cm -1 yr -1 for E sibiricum steppe and S. baicalensis steppe, and 3.9 gDM m -2 cm -1 yr -1 for L. chinense steppe, respectively.Using the CENTURY ecosystem model, simulation results agreed reasonably well with the observed soil organic matter, seasonal dynamics and interannual variation of plant biomass of these three steppe sites during [1981][1982][1983][1984][1985][1986][1987][1988][1989][1990]. The CENTURY model is slightly more successful than the empirical regression models that use annual precipitation to estimate PLAB of these meadow steppe over time. Both seasonal distribution and interannual variation in precipitation and temperature are the important controls of temporal dynamics of plant biomass, rain use efficiency, carbon flux and storage of these meadow steppe ecosystems over time.
This paper describes a new Cymbella species from an alpine lake in the Pamir Mountains, NW China, with the aid of light and scanning electron microscopy and morphometric analyses. The morphology of the new species, named Cymbella pamirensis, is discussed and compared to similar species. The main morphometric features distinguishing Cymbella pamirensis from similar species of Cymbella are the outline and size of the valves. Cymbella pamirensis has been observed in surface sediment and core samples from Lake Sate Baile Dikuli, an alkaline, mesotrophic lake of the Pamir Mountains.
Stauroneis lacusvulcani sp. nov. is described from two small volcanic lakes in northeastern China. The morphology of S. lacusvulcani is illustrated with light and scanning electron micrographs and discussed in comparison with several species of the Stauroneis gracilior group. S. lacusvulcani can be distinguished by the size of the valves and its long-protracted and strongly capitate apices. Diatom analysis of the sedimentary record from Lake Xiaolongwan (Jilin Province) showed that this new species was most abundant during the early Holocene (~8950 to 10,640 yrs BP).
The unique geographical and climatic settings of the eastern Pamirs make this region sensitive to the Westerlies and global climate change. Holocene fluctuations in water-level of Lake Kalakuli, a proglacial lake located to the northwest of the Muztag Ata glacier, were reconstructed based on diatoms from a ∼15 m long sediment core spanning the last ∼9,900 years. To establish how diatom species distribute in relation to water depth in Lake Kalakuli, a dataset of 45 surface sediment samples was retrieved from different water depth. Statistical analyses such as cluster analysis (TWINSPAN) and redundancy analysis (RDA) were used to demonstrate that the water depth gradient is the main environmental gradient driving the distribution of these diatom assemblages. A diatom-water depth transfer function, was then developed using a weighted averaging partial least squares component 2 model (R2 = 0.89, RMSEP = 1.85 m) and applied to the Holocene diatom sequence from Lake Kalakuli. Due to the large residual errors in the model only the general trends in water level are proposed. Effective moisture increased rapidly during the early Holocene, as the water depth reached a high level from the lowest level within about two thousand years. Only small amplitude fluctuations were recorded during the mid- and late Holocene until the last few hundred years when a marked increase occurred. Changes in summer insolation over the northern hemisphere drove the advances and retreats of the Muztag Ata glacier, which in turn controlled the fluctuations of water level in this lake. The diatom-derived paleoclimatic trend from Lake Kalakuli is consistent with the Holocene climate evolution in the Westerlies-dominated area of Central Asia.
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