[Yearly Changes of Phytoplankton Community in the Ecology-monitoring Area of Changli, Hebei in Summer].

Based on the investigation of phytoplankton and water body nutrient concentration in the ecology-monitoring area of Changli in summer from 2005 to 2013, the phytoplankton community structure was analyzed. The result showed that in recent 9 years, 3 phyla including 23 families, 39 genera and 105 species of phytoplankton were identified, in which 85.7% were diatoms and 13.3% were dinoflagellate. Only one species was found belonging to golden algae. There was great difference in dominant species among different years. According to the value of dominance, there were Coscinodiscus radiatus, Coscinodiscus debilis, Rhizosolenia styliformis, Cerataulina bergoni, Coscinodiscus wailesii, Thalassiosira sp., Ceratium tripos, Chaetoceros lorenzianus, Skeletonema costatum. The cell abundance was decreased yearly. The Shannon-Wiener index of phytoplankton community ranged from 0.015 to 3.889, and the evenness index ranged from 0.009 to 1, which showed little yearly change. And phytoplankton species were unevenly distributed among the 19 sites, there were relatively low amount of dominant species, but the dominance was relatively high. Canonical Correspondence Analysis (CCA) results of the phytoplankton community and its environmental factors showed that the environmental factors influencing the change of phytoplankton community structure in summer included water temperature, nutrients (TP, TN and NO3(-) -N, NH4(+)-N) and salinity, and the structural change was the result of the interactions of different environmental factors.

[Antioxidase activities and photosynthetic pigment contents in Larix principis-rupprechtii leaves along an altitudinal gradient].

To study the physiological mechanisms in environment adaptation of alpine trees, the antioxidase activities and photosynthetic pigment contents in Larix principis-rupprechtii leaves along an altitudinal gradient from 1 600 m to 2 800 m at Pangquangou National Nature Reserve were investigated. The results showed that the superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities in L. principis-rupprechtii leaves had the same change pattern along the altitudinal gradient, i. e. , relatively lower at middle altitude (1 900-2 400 m) and relatively higher at lower (1 600-1 800 m) and higher altitudes (2 500-2 800 m). Comparing with those at middle altitude, the SOD, POD and CAT activities were 62.79%, 42.13% and 7.87% higher at lower altitude and 75.20%, 14.49% and 63.38% higher at higher altitude, respectively, but decreased at the altitude near the upper limit of forest vertical distribution. At lower and higher altitudes, malondialdehyde (MDA) content was up to 9.27 and 14.06 micromol x g(-1) FM, respectively, while at middle altitude, it was 5.58 micromol x g(-1) FM on average. Chlorophyll and carotinoid contents tended to decrease with increasing altitude, while chlorophyll a/b ratio and relative carotinoid content (Car/ Chl) were in adverse, with the relative coefficients being -0.969 and -0.986, and 0.962 and 0.877, respectively.