[Comparison of GIMMS and MODIS normalized vegetation index composite data for Qing-Hai-Tibet Plateau].

Consistent NDVI time series are basic and prerequisite in long-term monitoring of land surface properties. Advanced very high resolution radiometer (AVHRR) measurements provide the longest records of continuous global satellite measurements sensitive to live green vegetation, and moderate resolution imaging spectroradiometer (MODIS) is more recent typical with high spatial and temporal resolution. Understanding the relationship between the AVHRR-derived NDVI and MODIS NDVI is critical to continued long-term monitoring of ecological resources. NDVI time series acquired by the global inventory modeling and mapping studies (GIMMS) and Terra MODIS were compared over the same time periods from 2000 to 2006 at four scales of Qinghai-Tibet Plateau (whole region, sub-region, biome and pixel) to assess the level of agreement in terms of absolute values and dynamic change by independently assessing the performance of GIMMS and MODIS NDVI and using 495 Landsat samples of 20 km x20 km covering major land cover type. High correlations existed between the two datasets at the four scales, indicating their mostly equal capability of capturing seasonal and monthly phenological variations (mostly at 0. 001 significance level). Simi- larities of the two datasets differed significantly among different vegetation types. The relative low correlation coefficients and large difference of NDVI value between the two datasets were found among dense vegetation types including broadleaf forest and needleleaf forest, yet the correlations were strong and the deviations were small in more homogeneous vegetation types, such as meadow, steppe and crop. 82% of study area was characterized by strong consistency between GIMMS and MODIS NDVI at pixel scale. In the Landsat NDVI vs. GIMMS and MODIS NDVI comparison of absolute values, the MODIS NDVI performed slightly better than GIMMS NDVI, whereas in the comparison of temporal change values, the GIMMS data set performed best. Similar with comparison results of GIMMS and MODIS NDVI, the consistency across the three datasets was clearly different among various vegetation types. In dynamic changes, differences between Landsat and MODIS NDVI were smaller than Landsat NDVI vs. GIMMS NDVI for forest, but Landsat and GIMMS NDVI agreed better for grass and crop. The results suggested that spatial patterns and dynamic trends of GIMMS NDVI were found to be in overall acceptable agreement with MODIS NDVI. It might be feasible to successfully integrate historical GIMMS and more recent MODIS NDVI to provide continuity of NDVI products. The accuracy of merging AVHRR historical data recorded with more modern MODIS NDVI data strongly depends on vegetation type, season and phenological period, and spatial scale. The integration of the two datasets for needleleaf forest, broadleaf forest, and for all vegetation types in the phenological transition periods in spring and autumn should be treated with caution.

[Canonical correspondence analysis between phytoplankton community and environmental factors in macrophtic lakes of the middle and lower reaches of Yangtze River].

The phytoplankton communities in 4 macrophtic lakes (Longgan Lake, Liangzi Lake, Futou Lake and Baoan Lake) in Middle-Lower Yangtze Plain were investigated in September 2011, and 7 phylum and 231 species of phytoplankton were detected in the waters. The results indicated that phytoplankton was mainly composed of Cyanophyta, Bacillariophyta and Chlorophyta. The four lakes were mesotrophic. And the main phytoplankton was Phormidium foveolarum, Synedra ulna, Phormidium tenu and Tribonema minus. The relationships between the distribution of phytoplankton and environmental factors in each sampling site were studies by canonical correspondence analysis. The results demonstrated that pH and Total phosphorus are the key factors for the distribution of phytoplankton communities in 4 typical macrophtic lakes in Middle-Lower Yangtze Plain.

[Allelopathic effect of Nelumbo nucifera stem and leaf tissue extract on the growth of Microcystis aeruginosa and Scenedesmus quadricanda].

Effects of Nelumbo nucifera stem and leaf tissue extract on the growth of Microcystis aeruginosa and Scenedesmus quadricanda were studied to verify its potential in entriphication control. Five concentrations of Nelumbo nucifera stem and leaf tissue extract were chosen to compare their inhibitory effects on the growth of Microcystis aeruginosa and Scenedesmus quadricanda. The result showed that the leaf extract inhibited the algae bloom more effectively than the stem extract on the whole. When the leaf extract normality was 25 g x L(-1), the highest inhibition rate of Microcystis aeruginosa and Scenedesmus quadricanda was 71.33% and 78.14%, respectively, while for the stem extract, the values were 49.78% and 52.14%. Propanamide was found in both the stem and leaf tissue extracts of Nelumbo nucifera by GC-MS analysis, with concentrations of 1.1 mg x L(-1) and 0.2 mg x L(-1), respectively. The EC50 values of the two kinds of algae were calculated by the probability method.

[Speciation and vertical distribution of heavy metals in sediments of Baiyangdian Lake].

In order to find out the heavy metal concentrations and their potential ecological risks on sediments in Baiyangdian Lake, 0-14 cm surface sediments had been collected by the no-disturbance-gravity sampler at seven representative sampling points of Baiyangdian Lake. Optimized BCR sequential extraction procedure was used to carry out the analysis of heavy metal forms in the surface sediments. The heavy metal contents of different forms and in different depths were determined. The relationship between different forms of heavy metal and total organic carbon (TOC) in the sediments was analyzed. The geo-accumulation index (Igeo) was employed to evaluate the extent of heavy metal contamination. The results demonstrated that Co, Fe, Mn, Pb, Zn were mainly in residual form, acid soluble form, Fe-Mn oxide and organic matter bound forms respectively. The tendency of organic bound form of heavy metals and TOC of sediments was greater than the others. The concentration of Co, Pb, Zn decreased with the increase of sediment depth, with the maximal concentration was between 0-2 cm, while the concentration of Mn was the minimal between 6-8 cm and the maximal was at 14 cm. Baiyangdian sediments were not contaminated as a whole by Co, Mn, apart from medium pollution in the entrance of the Fuhe River. The other regions were lightly polluted by Zn and Pb.