Relationship between TA (mmol/L) and TDS (mg/L) of water from the lakes in the Songnen Plain (two pairs of extreme values of Huao Lake and Bali Lake had been removed).

<p>Relationship between TA (mmol/L) and TDS (mg/L) of water from the lakes in the Songnen Plain (two pairs of extreme values of Huao Lake and Bali Lake had been removed).</p

Comparison of hydrochemical characteristics from various studies in 7 lakes in the Songnen Plain.

<p>Comparison of hydrochemical characteristics from various studies in 7 lakes in the Songnen Plain.</p

Variations of cell density (a), genera richness (b), proportion of dominant species (c) and H’ value (d) at different levels of TDS (mg/L) and TA (mmol/L) of water from the lakes in the Songnen Plain.

<p>Variations of cell density (a), genera richness (b), proportion of dominant species (c) and H’ value (d) at different levels of TDS (mg/L) and TA (mmol/L) of water from the lakes in the Songnen Plain.</p

The study lakes are located in the Songnen Plain of Northeast China, and this figure is generated from USGS National Map Viewer (public domain): http://viewer.nationalmap.gov/viewer/.

<p>The study lakes are located in the Songnen Plain of Northeast China, and this figure is generated from USGS National Map Viewer (public domain): <a href="http://viewer.nationalmap.gov/viewer/" target="_blank">http://viewer.nationalmap.gov/viewer/</a>.</p

Effects of Different Saline-Alkaline Conditions on the Characteristics of Phytoplankton Communities in the Lakes of Songnen Plain, China

<div><p>Many lakes located in the Songnen Plain of China exhibit a high saline-alkaline level. 25 lakes in the Songnen Plain were selected as research objects in this study. Water samples in these lakes were collected from June to August in 2008. Total Dissolved Solids (TDS) and Total Alkalinity (TA) were measured to assess the saline-alkaline level, and partial canonical correspondence analysis (CCA) was conducted as well. The results show that the majority of these lakes in the study area could be categorized into HCO₃⁻-Na⁺-I type. According to the TDS assessment, of the total 25 lakes, there are 14 for freshwater, 7 for brackish water and 4 for saltwater; and the respective range of TA was from 0.98 to 40.52. The relationship between TA and TDS indicated significant linear relationship (R² = 0.9292) in the HCO₃⁻-Na⁺-I type lakes in the Songnen Plain. There was a general trend that cell density, genera richness and taxonomic diversity decreased with the increase of saline-alkaline gradient, whereas a contrary trend was observed for the proportion of dominant species. When the TDS values were above 3×10³mg/L and the TA values were above 15mg/L, there was a significant reduction in cell density, genera richness and biodiversity, and their corresponding values were respectively below 10×10⁶ (ind/L), 15 and approximately 2.5. Through the partial canonical correspondence analysis (CCA), 10.7% of the genera variation was explained by pure saline-alkaline variables. <i>Cyclotella meneghiniana</i>, <i>Melosira ambigua</i> and <i>Melosira granulate</i> were found to become the dominant species in most of these lakes, which indicated that there may be rather wide saline-alkaline niches for common dominant species. About one-quarters of the genera which have certain tolerance to salinity and alkalinity preferred to live in the regions with relatively higher saline-alkaline levels in this study.</p></div

Partial canonical correspondence analysis (CCA) between phytoplankton genera and saline-alkaline parameters (TA and TDS) in the Songnen Plain.

<p>Partial canonical correspondence analysis (CCA) between phytoplankton genera and saline-alkaline parameters (TA and TDS) in the Songnen Plain.</p

Characteristics of phytoplankton communities of the lakes in the Songnen Plain in 2008.

<p>Characteristics of phytoplankton communities of the lakes in the Songnen Plain in 2008.</p

Environment characteristics of the lakes in the Songnen Plain in 2008.

<p>Environment characteristics of the lakes in the Songnen Plain in 2008.</p

Partial canonical correspondence analysis (CCA) between saline-alkaline parameters (TA and TDS) and the 25 lakes’ samples in the Songnen Plain.

<p>No.1 to No.25 represents the samples of the 25 lakes respectively, and the corresponding relations of number and the lakes’ name are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164734#pone.0164734.t001" target="_blank">Table 1</a>.</p

Testing serial correlation in a general <i>d</i>-factor model with possible infinite variance

It is well-known that the presence of serial correlation may result in an inefficient or even biased estimation in time series analysis. In this paper, we consider testing serial correlation in a general d-factor model when the model errors follow the GARCH process, which is frequently used in modeling financial data. Two empirical likelihood-based testing statistics are suggested as a way to deal with problems that might come up with infinite variance. Both statistics are shown to be chi-squared distributed asymptotically under mild conditions. Simulations confirm the excellent finite-sample performance of both tests. Finally, to emphasize the importance of using our tests, we explore the impact of the exchange rate on the stock return using both monthly and daily data from eight countries.</p