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Liu H.,Nanjing Normal University | Liu H.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Lin Z.,Nanjing Normal University | Lin Z.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | And 5 more authors.
Ecological Research | Year: 2014

This study investigates a spatially explicit, individual-based model for simulating the spread of invasive smooth cordgrass (Spartina alterniflora) in Yancheng coastal wetlands from 1995 to 2010. The model, which considers the landscape heterogeneity and changes detected by remote sensing, also reveals the relative importance of sexual and asexual reproduction in the spread by global sensitivity analysis. The model was verified as suitable for simulating the range expansion of S. alterniflora. The results show that: (1) although seedling recruitment is low, it significantly contributes to the range expansion of S. alterniflora. Removing sexual propagation greatly reduces the expansion rate. Rapid expansion requires both sexual and asexual reproduction; (2) in the global sensitivity analysis, the most significant affecters of S. alterniflora invasion were seed dispersal distance, adult survival rate and asexual recruitment survival rate. Sexual propagation contributes much more significantly to quick range expansion than asexual reproduction, but asexual reproduction is the main source of recruitment. Invasion control strategies should target a single reproduction mode. Here, limiting the germination and dispersal of seeds is suggested as a realistic strategy for controlling and managing invasion by this species. © 2014, The Ecological Society of Japan.


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.


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.


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.


Xiangzhen Q.,Nanjing Normal University | Xiangzhen Q.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Zhenshan L.,Nanjing Normal University | Zhenshan L.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | And 2 more authors.
Ecological Informatics | Year: 2016

Although invasion by exotic species is recognized as a major ecological problem, little is known about the interactive effects of competition and landscape patterns. In this paper, neutral landscape model and spatially explicit model are employed to numerically analyze the interactive effects of key demographic traits, competition abilities and landscape patterns on the spread dynamics of exotic species. The results showed that: (1) Competition is critically important for the spread of exotic species, which mediates the effects of landscape structure. The spread of competitively superior exotic species is much easier in large and highly clumped habitat while spread of inferior ones does well in small and scattered landscape patterns. Strong competitors can efficiently exploit the massive clumping resources, and poor competitors tend to escape from competition of native species in disrupted niches; (2) The spread of invasive exotic species is positively related to the seed production and negatively related to the reproduction age. The fitting curve varies with landscape patterns and competition abilities. For strong exotic competitors, spread dynamics mostly grows logarithmically with the seed production, but quadratic polynomial equation can better fit their relationship in some scenarios. For inferior ones, quadratic polynomial fitting appears in all landscape scenes but H= 0.5, h= 0.75; (3) The mean dispersal distance is vital to the spread of exotic species. Comparing to convex increase of superior exotic species, inferior exotic competitor shows a fast concave growth with the increasing mean dispersal distance; (4) It will not be an effective method to control invasion of inferior exotic species by increasing landscape fragmentation. According to our simulation results, habitat conservation needs to be distinctively treated for particular case. For example, the abundance of poor exotic species increases when landscape aggregation, seed production and mean dispersal distance decrease. So different management strategies should be taken according to different targets, landscape scenarios, competition and demography characteristics. © 2015.


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.


Zhang J.,Nanjing Normal University | Zhang J.,CAS Nanjing Institute of Soil Science | Zhang J.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Yu Y.,Nanjing Normal University | And 4 more authors.
Journal of Geophysical Research G: Biogeosciences | Year: 2014

Previous studies have demonstrated that denitrification rates are low in subtropical forest soils. However, the mechanisms governing this process are not well known. This study seeks to identify the mechanisms responsible for the low denitrification capacity and high nitrogen oxide gas ratio in subtropical forest soils in China. The denitrification capacity and nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2) emission rates were measured using the acetylene inhibition method under conditions of added nitrate and anoxia. The abundance of nitrate reductase (narG), nitrite reductase (nirK), nitric oxide reductase (cnorB), and nitrous oxide reductase (nosZ) was measured using real-time, quantitative polymerase chain reaction, and sequencing of the nirK and norB products was performed to analyze the population structure of denitrifying bacteria. These results showed that the denitrification capacity in subtropical forest soils was lower than in temperate forest soils (p < 0.05). Multiple regression analysis showed that redox potential at the start of incubation (Ehi), rather than soil pH or soil organic C, was the key soil variable influencing denitrification, and Ehi alone could explain 68% of the variations in denitrification capacity. The high Ehi in subtropical soils led to a low abundance of nirK and significant differences in the population structure of denitrifying bacteria between subtropical and temperate soils. Therefore, Ehi was responsible for the low denitrification capacity in subtropical forest soils. The ratio of NO to total denitrification gas products (p < 0.01) and the ratio of NO and N2O to total denitrification gas products (p < 0.05) were significantly higher in subtropical forest soils than in temperate forest soils, while the reverse trend was observed for the ratio of N2 to total denitrification gas products (p < 0.05). A high Ehi reduced the specific reduction activity of each nosZ copy and, in turn, resulted in a large ratio of NO and N2O to total denitrification gas products in subtropical soils. Thus, NO and N2O, but not N2, were the dominant denitrification gas products, accounting for 80%, even under the highly anaerobic conditions in subtropical forest soils and despite low denitrification capacity. These results were significant for understanding the "Hole in the Pipe" model and NO and N2O gases emission in subtropical forest soils. Despite the fact that the nitrogen flowing through the pipe (denitrification capacity) was low, the large holes in the pipe resulted in a large quantity of NO and N2O gases leaking out. This leakage may be a potential mechanism for the high levels of NO and N2O gas emission in subtropical forest soils and could partly explain why NO and N2O emissions are generally high in subtropical and tropical soils. ©2014. American Geophysical Union. All Rights Reserved.


Huang X.,Nanjing Normal University | Wen T.,Nanjing Normal University | Meng L.,Hainan University | Zhang J.,Nanjing Normal University | And 3 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

Soil-born diseases mainly caused by continuous cropping of monocultures are world-wide problems and seriously restrain the development of contemporary agriculture. Traditionally, farmers use chemical pesticides as a relatively dependable method of protecting plants from soil-borne pathogens. However, increased use of chemical pesticides have several negative effects on the environment and human health and restrictions have increased on use of a variety of chemical pesticides. Therefore, there is an urgent need for effective and environmentally friendly ways to prevent and control soil- borne diseases. Banana fusarium wilt caused by Fusarium oxysporum f. sp. Cubense (FOC) is a kind of world-wide soil- borne diseases and causes serious economic loss every year. The effective ways to prevent the disease are still not available. The experiment was carried out in October 2012. The study site was located in Ledong, Hainan province, China (18º65´N, 107º79´E). The filed used in the experiment was planted with banana for many years, and had a high Fusarium wilt disease incidence of more than 50%. The experiment contained ten treatments, i.e. (1) untreated soil, (2) disturbed soil, (3) flooding disturbed soil, (4) flooding soil incorporated with rice straw at low rate, (5) flooding soil incorporated with rice straw at high rate, (6) flooding soil incorporated with rice straw at high rate plus lime, (7) flooding soil incorporated with pig manure, (8) flooding soil with bagasse, (9) flooding soil with bagasse plus lime, and (10) flooding soil with lime. The soil pH, contents of SO2- 4 , NO- 3 and NH+ 4, and the populations of bacteria, actinomyces, fungi and FOC of the soils were analyzed at 5, 10, and 15 days after flooding and drained. The results showed that the soil pH in the flooding treatments were raised in the fifth day significantly compared with untreated soils and then became gradually declined over treated time. The contents of SO2- 4 and NO- 3 were decreased significantly, while the content of NH+ 4 were increased in the soils with straw, pig manure and lime, respectively, under flooding conditions. Flooding the soil incorporated with organic matters significantly reduced the populations of cultivable actinomyces and fungi but not influenced the populations of cultivable bacteria. The populations of FOC were significantly declined in the soils with increasing the rate of incorporated rice straw under flooding condition to 2.88% of untreated soil. Incorporation of bagasse and lime decreased the population of FOC significantly as well, but less effectively than with rice straw did under flooding conditions. Pig manure was not effective to reduce the FOC population. The total amounts of microbe in the treatments applied with organic matters were raised compared with untreated soil. These resluts indicated that anaerobic conditions created by flooding soil incorporated with organic matters not only reduced the FOC population in the soil, but also improved the soil physicochemical properties and microbial communities. It is the first report in China that quickly and intensively anaerobic conditions created by flooding soil incorporated with organic matters effectively reduce the population of plant pathogens within 15 days. Therefore, anaerobic soil disinfection would provide a feasible measure for the control of banana fusarium wilt in agricultural production. Furthermore, the method provides a way to recycling use of crop residues. © 2014, Science Press. All rights reserved.


Zhang J.,Nanjing Normal University | Zhang J.,Chinese Academy of Sciences | Zhang J.,Jiangsu Key Laboratory of Environmental Change and Ecological Construction | Sun W.,Nanjing Normal University | And 4 more authors.
Soil Biology and Biochemistry | Year: 2014

In this study, a 15N tracer experiment was carried out to investigate the relative availability of different nitrogen (N) substrates for heterotrophic nitrifiers and to determine the significance of heterotrophic nitrification in two acidic forest soils in eastern China. Five 15N labeled substrates were applied, i.e. Glycine (4.90atom% 15N excess), l-glutamic acid (4.89atom% 15N excess), maize straw (3.63 atom% 15N excess), (NH4)2SO4 (4.97atom% 15N excess), and control and were incubated for 4 days without or with C2H2 at 1KPa (1%) in laboratory. The results showed that accumulation of 15N-NO3- significantly increased with the incubation time in all 15N labeled treatments in the presence of acetylene, indicating that NO3- produced from heterotrophic nitrification convincingly occurred and heterotrophic nitrifiers could use both ammonium and organic N compounds substrates for nitrification in the studied soils. The 15N-NO3- production in the Glycine and l-glutamic acid treatments in the presence of acetylene was obviously higher than that in the (NH4)2SO4 and maize straw treatments (p<0.05), indicating availability of N substrates for heterotrophic nitrifiers was different. The heterotrophic nitrification of amino organic N compounds could occur via a combined organic and inorganic pathway. However, for complicated organic N substrate, e.g. maize straw in this study, almost all 15N-NO3- was produced by organic N pathway. The contribution of heterotrophic nitrification to total nitrification varied from 23% to 93% in the different N substrate treatments as follows: (NH4)2SO4


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 .

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