Understory fuel loads and the impact factors of Quercus mongolica natural secondary forest in Hebei Pro-vince, China.

We investigated understory fuel loads of Quercus mongolica natural secondary forests in Hebei Province, China. We analyzed the effects of stand factors, topographic factors, and ground cover factors on the quantity and composition of fuel, established the dynamic models of understory fuel loads, and proposed management measures. The results showed that the understory total fuel load in Q. mongolica natural secondary forests was 11.68 t·hm-2, which exceeded the forest fire potential threshold (10 t·hm-2). The understory dead fuel load was mainly humus, and the understory living fuel load was mainly shrubs. The 1 h time-lag fuel load increased significantly with increasing canopy density, stand density, stand age, and litter thickness. The 10 h time-lag fuel load increased signi-ficantly with increasing stand density, average tree height, and litter thickness. Humus load decreased significantly with increasing altitude and increased significantly with increasing humus thickness. Herb load increased significantly with increasing sunny slope orientation and herbal coverage. Shrub load increased significantly with increasing slope degree, shrub coverage, and humus thickness. Understory total fuel load decreased significantly with increasing altitude, and increased significantly with increasing stand density, humus thickness, and litter thickness. The results of stepwise regression analysis indicated that stand density, humus thickness, and altitude could better predict the understory total fuel load (Radj2=0.775). Therefore, more attention should be paid on the control of stand density of Q. mongolica natural secondary forest in Hebei Province. Cleaning of litters and humus on the ground would help prevent forest fires scientifically and effectively.

[Responses of photosynthetic physiology and sap flow to the introduction of external dye in Populus ×euramericana cv. '74/76']. / 107æ¨å ‰åˆç”Ÿç†ä¸Žæ ‘å¹²æ¶²æµå¯¹å¤–æºæŸ“æ¶²å¯¼å ¥çš„å“åº”.

The exogenous liquid introduction technology is an effective way to produce the value-added poplar wood with excellent pattern color. This technology was used to add the various concentrated active red dyeing solution (0.2%, 0.4% and 0.6%) into target trees of six-year-old 107 poplar (Populus ×euramericana cv. '74/76'). The photosynthetic gas exchange parameter and sap flow rate were measured by Li-6400 photosynthetic instrument and TDP stem flowmeter, respectively. We analyzed the relationship between photosynthetic parameters, sap flow rate and dye absorption, and the effects of exogenous dye solution on the photosynthetic physiology and sap flow characteristics. The results showed that exogenous dyeing solution significantly inhibited flow rate of poplar trunks. The 0.2% concentrated liquid was far less effective than others (0.4% and 0.6%). The net photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr) of poplars treated with different concentrated dyeing liquids were significantly lower than the control poplar. The intercellular carbon dioxide concentration (Ci) decreased first and then increased. The inhibitory effects of 0.4% and 0.2% concentrated dyeing solutions on photosynthesis were stronger than that of 0.6%. Dye absorption decreased with increasing dye concentration. The maximum liquid flow rate, Pn, gs and Tr were significantly negatively correlated with the dye content. The contents of chlorophyll (a+b), chlorophyll a and chlorophyll b in exogenous dyeing solution treatments were significantly lower than those of the control at the later stage. The concentration of dyeing solution and introduction time determined the amount of dye absorption. The dye solution 0.4%, which was introduced for three days, could ensure the appropriate dye absorption and reduce the inhibitory effect on the physiological activities of the poplar.

[Effects of NaCl stress on photosynthesis characteristics and fast chlorophyll fluorescence induction dynamics of Pistacia chinensis leaves].

By using fast chlorophyll fluorescence induction dynamics analysis technique (JIP-test), this paper studied the photosynthesis characteristics and fast chlorophyll fluorescence induction dynamics of 1-year old Pistacia chinensis seedlings under the stress of NaCl at the concentrations 0% (CK), 0.15%, 0.3%, 0.45%, and 0.6%. With the increasing concentration of NaCl, the contents of Chl a, Chl b, and Chl (a+b) in the seedlings leaves decreased, the Chl a/b ratio decreased after an initial increase, and the carotenoid content increased. The net photosynthetic rate (P(n)) and stomatal conductance (g(s)) decreased gradually with increasing NaCl concentration. The decrease of P(n) was mainly attributed to the stomatal limitation when the NaCl concentration was lower than 0.3%, and to the non-stomatal limitation when the NaCl concentration was higher than 0.3%. The trapped energy flux per RC (TR0/CS0), electron transport flux per RC (ET0/CS0), density of RCs (RC/CS0), and yield or flux ratio (psi(0) or phi(E0)) decreased, but the absorption flux per CS (ABS/CS0) and the K phase (W(k)) and J phase (V) in the O-J-I-P chlorophyll fluorescence induction curves increased distinctly, indicating that NaCl stress damaged the leaf oxygen-evolving complex (OEC), donor sides, and PS II reaction centers. When the NaCl concentration reached 0.3%, the maximum photochemical efficiency (F(v)/F(m)) and performance index (PI(ABS)) decreased 17.7% and 36.6%, respectively, as compared with the control.

[Effects of salt stress on physiological characters and salt-tolerance of Ulmus pumila in different habitats].

Taking the Ulmus pumila seedlings from three different habitats (medium-, mild-, and non-saline soils) as test materials, an experiment was conducted to study their salt-tolerance thresholds and physiological characteristic under different levels (0, 2, 4, 6, 8, and 10 g X kg(-1)) of salt stress. With increasing level of the salt stress, the seedlings taken from medium- and mild- saline habitats had a lower increment of leaf membrane permeability, Na+ content, and Na+/K+ but a higher increment of leaf proline, soluble sugar, and K+ contents, and a lower decrement of leaf starch content, net photosynthetic rate, transpiration rate, intercellular CO2 concentration, and stomatic conductance, as compared with the seedlings taken from non-saline habitat. The salt-tolerance thresholds of the seedlings taken from different habitats were in the order of medium- saline habitat (7.76 g X kg(-1)) > mild- saline habitat (7.37 g X kg(-1)) > non-saline habitat (6.95 g X kg(-1)). It was suggested that the U. pumila seedlings in medium- and mild-saline habitats had a stronger adaptability to saline soil environment than the U. pumila seedlings in non-saline soil environment.

Effect of alpha 2b interferon on inducement of mIL-2R and treatment of HCV in PBMC from patients with chronic viral hepatitis C.

AIM: To study the level of membrane interleukin-2 receptor (mIL-2R) on surface of peripheral blood mononuclear cells (PBMC) and the therapeutic efficacy of alpha 2b interferon on the treatment of HCV-RNA in PBMC of patients with chronic hepatitis C and to compare the negative rates of HCV-RNA in PBMC, HCV-RNA and anti-HCV in serum. METHODS: Before and after treatment of alpha 2b interferon, the level of mIL-2R of patients with chronic hepatitis C was detected by biotin-streptavidin (BSA). The therapeutic group (26 cases) was treated with alpha 2b interferon (3 MU/d) and control therapeutic group (22 cases) was treated with routine drugs (VitC, aspartic acid). The total course of treatment with alpha 2b interferon and routine drug was six months and per course of the treatment was three months. The levels of HCV-RNA in PBMC, HCV-RNA and anti-HCV in serum were detected before and after a course of the treatment. RESULTS: Before and after treatment of alpha 2b interferon and routine drugs, the levels of mIL-2R in silence stage were (3.44+/-0.77) % and (2.95+/-0.72) %, the levels of mIL-2R in inducement stage were (33.62+/-3.95) % and (30.04+/-3.73) %. There was a significant difference between two groups (P<0.01-P<0.05). After treatment of alpha 2b interferon with 3 MU/d for two courses of the treatment, the total negative rates of HCV-RNA in the PBMC and HCV-RNA, anti-HCV in serum were 42.31 % (11/26), 57.69 % (15/26), 65.38 %(17/26) respectively. After the treatment of routine drug, the negative rates of HCV-RNA in PBMC and HCV-RNA, anti-HCV in serum were 13.64 % (3/22), 22.73 % (5/22), 27.27 % (6/22) respectively. There was high significant difference in the group treated with alpha 2b interferon and the group treated with routine drugs (P<0.01-P<0.05). CONCLUSION: The mIL-2R can be induced by alpha 2b interferon during the treatment. The alpha 2b interferon has a definite effect on the treatment of HCV-RNA in PBMC. The curative effect of alpha 2b interferon is better than that of the routine drugs.