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Wang J.-Q.,Nanjing University of Information Science and Technology | Wang J.-Q.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Zheng Y.-F.,Nanjing University of Information Science and Technology | Xue Y.,Nanjing University of Information Science and Technology
Chinese Journal of Ecology | Year: 2015

Based on the in situ UV-B doses observed in the late spring and early summer, the photosynthesis fluorescent parameters of the adult plants of Potamogeton cripus under the ultraviolet radiation stress (50, 100, 150, and 200 μW·cm-2) were determined. The results revealed that Foand Fmincreased in the initial period and then decreased with the increasing the dose of UV-B radiation. Fv/Fm, ΦPSIIand NPQ consistently increased with increasing the radiation dose. The findings suggest that when the adult plants of P. cripus were irradiated under UV-B radiation, PSII reaction center was injured to reversible inactivity or irreversible damage, the light energy conversion efficiency and the electron transport rate were reduced, and the actual photochemical efficiency declined. In conclusion, UV-B radiation accelerates the decline of P. crispus, indicating that ultraviolet radiation might be an important factor leading to mass mortality of P. crispus in late spring and early summer. However, further research is necessary to discover whether UV-B radiation combines with other environmental factors to cause the decline of P. crispus. © 2015, editorial Board of Chinese Journal of Ecology. All rights reserved. Source


Wang J.Q.,Nanjing University of Information Science and Technology | Wang J.Q.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Zheng Y.F.,Nanjing University of Information Science and Technology | Xue Y.,Nanjing University of Information Science and Technology
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

Potamogeton crispus plays an important role in purifying water and maintaining a healthy aquatic ecosystem in some shallow lakes; however, mass mortality occurs to P. crispus populations in the late spring and early summer, which possibly results in secondary pollution. Therefore, the causes of P. crispus mass mortality have been a hot research topic in the field of aquatic ecological restoration. Some researchers have reported that intense light is the key factor in the decline of P. crispus. The UV- B band in strong light is generally recognized to damage plants and animals, and can even penetrate into the water column and cause harm to aquatic organisms. Therefore experiments were conducted to determine the effect of the UV-B radiation in strong light on P. crispus decline. In this study, mature plants of P. crispus were daily exposed to different doses of UV-B radiation (50, 100, 150, and 200 μW/ cm2) for 6 hours (09:00—15:00). The cumulative effective doses of UV-B radiation were, respectively, 10.8 kJ/ m2, 21.6 kJ/ m2, 32.4 kJ/ m2 and 43.2 kJ/ m2. The control group was only exposed to UV-A radiation and photosynthetically active radiation (PAR). PAR and UV-A radiation were set to the same levels in all treatment groups. The physiological characteristics of the experimental plants were monitored regularly under UV-B radiation, and physiological and biochemical indices and photosynthetic pigment contents were determined. The results show that the chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (Chlt), and carotenoid (CAR) contents can be improved by UV-B radiation at doses below 10.8 kJ/ m2, and can be inhibited in the decline stage. The Chla, Chlb, Chlt, and CAR contents were all decreased by UV-B radiation when the UV-B radiation dose was greater than 10.8 kJ/ m2, and the inhibition effects increased with increasing radiation dose. Catalase (CAT) and peroxidase (POD) activities were increased under short-term radiation and gradually increased with increasing radiation dose; however, these activities were inhabited with continuing exposure to radiation. The activity of superoxide dismutase (SOD) increased gradually with prolonged irradiation time, and the activity of SOD increased with increasing radiation dose. The malondialdehyde (MDA) content was increased at the beginning of the UV-B radiation and gradually increased with increasing radiation dose; however, the MDA content decreased with continuing radiation. The soluble protein (Pr) and soluble sugar (SC) contents were improved at the beginning of the UV-B radiation, and gradually increased with increasing radiation dose, but these contents decreased after long-term UV-B radiation, and the contents decreased gradually with increasing radiation dose. The results indicate that UV-B radiation may be an important factor leading to the mass mortality of P. crispus in late spring and early summer. Accordingly, we deduce that the sharp increases in ultraviolet radiation on the land surface in the late spring and early summer leads to mass mortality of wild P. crispus populations. However, further research is necessary to study whether UV-B radiation acts synergistically with other environmental factors to affect physiological activity in the decline of P. crispus. © 2015, Ecological Society of China. All rights reserved. Source


Liu D.,Nanjing Normal University | Liu D.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Wang Y.,Nanjing Normal University | Cheng H.,University of Minnesota | And 3 more authors.
Quaternary Science Reviews | Year: 2015

Climate during the early Holocene was highly variable due to the complex interplay of external and internal forcing mechanisms. The relative importance for them on the Asian monsoon (AM) evolution yet remains to be resolved. Here we present two-to six-yr-resolution oxygen isotope (δ18O) records of five stalagmites, four of which are annually-laminated, from Qingtian Cave, central China, revealing detailed AM variability between 10.9 and 6.1kaBP. Over the contemporaneous periods, the δ18O records agree well with each other at multi-decadal to centennial timescales. When pieced together with the previously published isotopic data from the same cave, the final δ18O record reveals detailed AM variability from the last deglaciation to the mid-Holocene, consistent with other cave records. The most striking feature of the δ18O record is the recurrence of centennial-scale oscillations, especially during the annually-counted period (8.8-6.1kaBP). Cross-wavelet analyses between the δ18O record and solar proxies show strong coherence at 200-yr cycle, suggesting that solar output was actively involved as a primary contributor. The AM depression at 8.2kaBP is indistinguishable in amplitude and pattern from a series of weak AM events after 8kaBP. We speculate that these centennial-scale AM changes might be regulated by the positive feedbacks of oceanic/atmospheric interactions to the solar activity under the condition of the retreat of continental ice-sheets. © 2015 Elsevier Ltd. Source


Cheng Y.,CAS Nanjing Institute of Soil Science | Cheng Y.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Zhang J.-B.,Nanjing Normal University | Wang J.,Nanjing Normal University | And 2 more authors.
Journal of Plant Nutrition and Soil Science | Year: 2015

It is commonly believed that nitrification is the dominant process for N2O production under aerobic conditions. However, this has been challenged by recent studies on acidic soils, where denitrification has been found to dominate N2O production. Analyzing the data collected from peer-reviewed literature, we found that pH was a critical factor regulating N2O production pathways under aerobic conditions. There is a pH threshold of approx. 4.4, below which denitrification dominated N2O production and vice versa. A decrease in soil pH can significantly increase the contribution of denitrification to N2O production. Overall, this mini-review increases our understanding of N2O sources in soils under aerobic conditions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Zhang J.,Nanjing Normal University | Zhang J.,Chinese Academy of Sciences | Zhang J.,Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control | Wang J.,Nanjing Normal University | And 5 more authors.
Soil Biology and Biochemistry | Year: 2015

Many previous studies have demonstrated that heterotrophic nitrification processes play an important role in the production of NO3- in acidic soils. However, it is not clear whether a low concentration of nitrogenous organic compounds support heterotrophic nitrification processes in natural soils. In this study, we performed an 15N tracer experiment with a glycine concentration gradient (20, 40, 80, and 160mgNkg-1) to investigate the effect of the organic nitrogen concentration on the heterotrophic nitrification rate and its relative contribution to the total nitrification of the studied acidic forest soil. This experiment demonstrated that 15N-NO3- accumulated over time with all nitrogen treatments in the presence of acetylene, confirming that heterotrophic nitrification occurred even at a low organic nitrogen concentration (20mgkg-1) in the studied acidic forest soil. In the presence of acetylene, the 15N-NO3- concentration in the 20 and 40mgkg-1 glycine-N treatments was significantly lower than in the 80 and 160mgkg-1 glycine-N treatments (p<0.05), indicating that a high organic nitrogen concentration stimulated the heterotrophic nitrification rate. There was no significant difference in the average contribution of heterotrophic nitrification to total nitrification among the different nitrogen treatments, suggesting that the organic nitrogen concentration did not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil. Our results confirmed that a low concentration of organic N (20mgkg-1) supported heterotrophic nitrification in the studied soil. The organic nitrogen concentration stimulates the heterotrophic nitrification rate, but does not affect the relative contribution of heterotrophic nitrification to total nitrification in the studied acidic soil. © 2014 . Source

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