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  • 1
    Language: English
    In: Atmospheric Environment, Jan, 2013, Vol.64, p.242(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.atmosenv.2012.10.015 Byline: Weijun Shen (a), Huili Ren (a), G. Darrel Jenerette (b), Dafeng Hui (c), Hai Ren (a) Abstract: Acid deposition as a widely concerned environmental problem in China has been less studied in plantation forests compared to urban and secondary forests, albeit they constitute 1/3 of the total forested areas of the country. We measured the rainwater amount and chemistry outside and beneath the canopies of two widely distributed plantations (Acacia mangium and Dimocarpus longan) in the severe acid rain influenced Pearl River Delta region of southeastern China for two years. Our results showed that the frequency of acid rain was 96% on the basis of pH value 〈5.6. The volume-weighted mean (vwm) pH was 4.62 and higher in the dry (Oct.-Mar.) than in the wet (Apr.-Sep.) seasons. The major acidic anion was sulfate with vwm concentration of 140 [mu]eq l.sup.-1 and annual deposition flux of 110.3 kg ha.sup.-1 yr.sup.-1. The major neutralizing cations were calcium (94.8 [mu]eq l.sup.-1 and 28 kg ha.sup.-1 yr.sup.-1) and ammonium (41.2 [mu]eq l.sup.-1 and 11.7 kg ha.sup.-1 yr.sup.-1). Over 95% of these major acidic anions and neutralizing cations were derived from anthropogenic and terrestrial sources as a result of industrial, agricultural and forestry activities. Plantation canopy had marked impacts on rainwater chemistry, with the measured anion and cation concentrations being significantly enriched in throughfall (TF) and stemflow (SF) rainwater by 1.4 (for NO.sub.3.sup.-) to 20-fold (for K.sup.+) compared to those in bulk precipitation (BP). Dry deposition generally contributed about 13-22% of the total deposition while canopy leaching mainly occurred for K.sup.+ (〉88%) and NH.sub.4.sup.+ (10-38%). The two tree species showed distinct impacts on rainfall redistribution and rainwater chemistry due to their differences in canopy architecture and leaf/bark texture, suggesting that species-specific effects should not be overlooked while assessing the acid deposition in forested areas. Author Affiliation: (a) CAS Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, 723 Xinke Rd., Tianhe District, Guangzhou 510650, China (b) Department of Botany and Plant Sciences, Center for Conservation Biology, University of California Riverside, Riverside, CA 92521, USA (c) Department of Biological Sciences, Tennessee State University, Nashville, TN 37209, USA Article History: Received 18 July 2012; Revised 4 October 2012; Accepted 9 October 2012
    Keywords: Rivers ; Rain ; Sulfates ; Air Pollution ; Forest Management ; Ecosystems ; Plantations ; Acid Deposition ; Forests ; Rainwater
    ISSN: 1352-2310
    Source: Cengage Learning, Inc.
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  • 2
    In: PLoS ONE, 2014, Vol.9(3)
    Description: The temperature sensitivity (Q 10 ) of soil heterotrophic respiration (R h ) is an important ecological model parameter and may vary with temperature and moisture. While Q 10 generally decreases with increasing temperature, the moisture effects on Q 10 have been controversial. To address this, we conducted a 90-day laboratory incubation experiment using a subtropical forest soil with a full factorial combination of five moisture levels (20%, 40%, 60%, 80%, and 100% water holding capacity - WHC) and five temperature levels (10, 17, 24, 31, and 38°C). Under each moisture treatment, R h was measured several times for each temperature treatment to derive Q 10 based on the exponential relationships between R h and temperature. Microbial biomass carbon (MBC), microbial community structure and soil nutrients were also measured several times to detect their potential contributions to the moisture-induced Q 10 variation. We found that Q 10 was significantly lower at lower moisture levels (60%, 40% and 20% WHC) than at higher moisture level (80% WHC) during the early stage of the incubation, but became significantly higher at 20%WHC than at 60% WHC and not significantly different from the other three moisture levels during the late stage of incubation. In contrast, soil R h had the highest value at 60% WHC and the lowest at 20% WHC throughout the whole incubation period. Variations of Q 10 were significantly associated with MBC during the early stages of incubation, but with the fungi-to-bacteria ratio during the later stages, suggesting that changes in microbial biomass and community structure are related to the moisture-induced Q 10 changes. This study implies that global warming’s impacts on soil CO 2 emission may depend upon soil moisture conditions. With the same temperature rise, wetter soils may emit more CO 2 into the atmosphere via heterotrophic respiration.
    Keywords: Research Article ; Biology And Life Sciences ; Earth Sciences ; Ecology And Environmental Sciences ; Physical Sciences
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: Forest Ecology and Management, Jan 15, 2012, Vol.264, p.72(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.foreco.2011.10.012 Byline: Dafeng Hui (a), Jun Wang (b), Xuan Le (a), Weijun Shen (b), Hai Ren (b) Keywords: Allometry; Biomass; Power function; Productivity; Regression analysis; Scaling Abstract: a* We study the relationship between tree productivity and biomass in China. a* Scaling exponents and slopes of tree productivity-biomass regression are not constant. a* Regression slope decreased with tree age, DBH, height, and elevation, but increased with tree density and longitude. a* Using tree size and age improves prediction of productivity from biomass estimates. Author Affiliation: (a) Department of Biological Sciences, Tennessee State University, Nashville, TN 37209, USA (b) Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China Article History: Received 6 August 2011; Revised 7 October 2011; Accepted 8 October 2011
    Keywords: Ecosystem Components -- Analysis ; Biomass Energy -- Analysis
    ISSN: 0378-1127
    Source: Cengage Learning, Inc.
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  • 4
    Language: English
    In: Climatic Change, 2015, Vol.133(4), pp.695-708
    Description: There is a pressing need to develop earth system models (ESMs), in which ecosystem processes are adequately represented, to quantify carbon-climate feedbacks. In particular, explicit representation of the effects of microbial activities on soil organic carbon decomposition has been slow in ESM development. Here we revised an existing Q 10 -based heterotrophic respiration (R H ) algorithm of a large-scale biogeochemical model, the Terrestrial Ecosystem Model (TEM), by incorporating the algorithms of Dual Arrhenius and Michaelis-Menten kinetics and microbial-enzyme interactions. The microbial physiology enabled model (MIC-TEM) was then applied to quantify historical and future carbon dynamics of forest ecosystems in the conterminous United States. Simulations indicate that warming has a weaker positive effect on R H than that traditional Q 10 model has. Our results demonstrate that MIC-TEM is superior to traditional TEM in reproducing historical carbon dynamics. More importantly, the future trend of soil carbon accumulation simulated with MIC-TEM is more reasonable than TEM did and is generally consistent with soil warming experimental studies. The revised model estimates that regional GPP is 2.48 Pg C year −1 (2.02 to 3.03 Pg C year −1 ) and NEP is 0.10 Pg C year −1 (−0.20 to 0.32 Pg C year −1 ) during 2000–2005. Both models predict that the conterminous United States forest ecosystems are carbon sinks under two future climate scenarios during the 21st century. This study suggests that terrestrial ecosystem models should explicitly consider the microbial ecophysiological effects on soil carbon decomposition to adequately quantify forest ecosystem carbon fluxes at regional scales.
    Keywords: Microbial Respiration – Research ; Carbon Sinks – Research ; Forest Reserves – Research;
    ISSN: 0165-0009
    E-ISSN: 1573-1480
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  • 5
    In: Journal of Experimental Botany, 2018, Vol. 69(15), pp.3531-3540
    Description: Review of the contemporary perspective on the specific photosynthesis machinery in the vasculature of C 3 plants, such as Arabidopsis and rice, and a new area for future C 3 photosynthesis study. In C 4 plants, the vascularization of the leaf is extended to include a ring of photosynthetic bundle sheath cells, which have essential and specific functions. In contrast to the substantial knowledge of photosynthesis in C 4 plants, relatively little is known about photosynthesis in C 3 plant veins, which differs substantially from that in C 3 mesophyll cells. In this review we highlight the specific photosynthetic machinery present in C 3 vascular cells, which likely evolved prior to the divergence between C 3 and C 4 plants. The associated primary processes of carbon recapture, nitrogen transport, and antioxidant metabolism are discussed. This review of the basal C 4 photosynthesis in C 3 plants is significant in the context of promoting the potential for biotechnological development of C 4 -transgenic rice crops.
    Keywords: C Vein ; C Vein ; Carbon Recapture ; Nitrogen Transport ; Photosynthesis ; Plant Vasculature
    ISSN: 0022-0957
    E-ISSN: 1460-2431
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  • 6
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, March 20, 2014, Vol.445, p.97(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.colsurfa.2014.01.023 Byline: Wei Zhang, Xiaomin Li, Tongxu Liu, Fangbai Li, Weijun Shen Abstract: Author Affiliation: (a) Guangdong Institute of Eco-Environment and Soil Sciences, Guangzhou, 510650, P. R. China (b) South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, P. R. China Article History: Received 15 September 2013; Revised 7 January 2014; Accepted 15 January 2014
    Keywords: Iron Oxides
    ISSN: 0927-7757
    Source: Cengage Learning, Inc.
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  • 7
    In: PLoS ONE, 2014, Vol.9(7)
    Description: The presence of an intonational phrase boundary is often marked by three major acoustic cues: pause, final lengthening, and pitch reset. The present study investigates how these three acoustic cues are weighted in the perception of intonational phrase boundaries in two experiments. Sentences that contained two intonational phrases with a critical boundary between them were used as the experimental stimuli. The roles of the three acoustic cues at the critical boundary were manipulated in five conditions. The first condition featured none of the acoustic cues. The following three conditions featured only one cue each: pause, final lengthening, and pitch reset, respectively. The fifth condition featured both pause duration and pre-final lengthening. A baseline condition was also included in which all three acoustic cues were preserved intact. Listeners were asked to detect the presence of the critical boundaries in Experiment 1 and judge the strength of the critical boundaries in Experiment 2. The results of both experiments showed that listeners used all three acoustic cues in the perception of prosodic boundaries. More importantly, these acoustic cues were weighted differently across the two experiments: Pause was a more powerful perceptual cue than both final lengthening and pitch reset, with the latter two cues perceptually equivalent; the effect of pause and the effects of the other two acoustic cues were not additive. These results suggest that the weighting of acoustic cues contributes significantly to the perceptual differences of intonational phrase boundary.
    Keywords: Research Article ; Biology And Life Sciences ; Medicine And Health Sciences ; Social Sciences
    E-ISSN: 1932-6203
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  • 8
    Language: English
    In: Landscape Ecology, 2011, Vol.26(5), pp.629-644
    Description: Lateral flows in landscape mosaics represent a fundamentally important process in landscape ecology, but are still poorly understood in general. For example, windblown litter nutrient transfer across a landscape has rarely been studied from an ecosystem perspective. In this study we measured the litter nutrient transfer from an Acacia mangium plantation to a Dimocarpus longan orchard in an agroforestry landscape for 3 years from January 2002 to December 2004. About 11% of the total litterfall of the acacia plantation were transported to the longan orchard annually, accounting for ca. 9–59% of the total litter nutrient input of the longan orchard. The windblown litter transfer showed high spatial variation mainly caused by wind speed and directions. Slope positions 5 m away from the source acacia plantation received significantly greater amount of allochthonous acacia litter than those 10 m away, and the northwest-facing slope of the longan orchard received 2 to 3-fold more litter than the southeast- and south-facing slopes because of the prevailing southeasterly wind in the region. To explore how different management practices may influence the litterfall, leaf production, and soil nutrient status of the two ecosystems, we developed a Meta-Ecosystem Litter Transfer (MELT) model to simulate the processes of litter-related transformation (production, deposition, and decomposition) and transfer (wind- and management-driven movement). Our simulation results suggest that less than 30% of acacia litter should be transferred to the longan orchard in order for the acacia plantation to sustain itself and maximize production of the longan. Connectivity of nutrient flow between adjacent ecosystems as shown here leads to a functional meta-ecosystem with higher landscape-scale production of ecosystem services. That is, managing this connectivity through landscape design or active litter transfers can lead to large changes in overall landscape functioning and service production.
    Keywords: Agroforestry landscape ; Litter transfer ; Nutrient flow ; Landscape management
    ISSN: 0921-2973
    E-ISSN: 1572-9761
    Source: Springer Science & Business Media B.V.
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  • 9
    In: PLoS ONE, 2014, Vol.9(1)
    Description: Based on the isometric hypothesis, belowground plant biomass (M B ) should scale isometrically with aboveground biomass (M A ) and the scaling exponent should not vary with environmental factors. We tested this hypothesis using a large forest biomass database collected in China. Allometric scaling functions relating M B and M A were developed for the entire database and for different groups based on tree age, diameter at breast height, height, latitude, longitude or elevation. To investigate whether the scaling exponent is independent of these biotic and abiotic factors, we analyzed the relationship between the scaling exponent and these factors. Overall M B was significantly related to M A with a scaling exponent of 0.964. The scaling exponent of the allometric function did not vary with tree age, density, latitude, or longitude, but varied with diameter at breast height, height, and elevation. The mean of the scaling exponent over all groups was 0.986. Among 57 scaling relationships developed, 26 of the scaling exponents were not significantly different from 1. Our results generally support the isometric hypothesis. M B scaled near isometrically with M A and the scaling exponent did not vary with tree age, density, latitude, or longitude, but increased with tree size and elevation. While fitting a single allometric scaling relationship may be adequate, the estimation of M B from M A could be improved with size-specific scaling relationships.
    Keywords: Research Article ; Agriculture ; Biology
    E-ISSN: 1932-6203
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  • 10
    Language: English
    In: Journal of Alloys and Compounds, 25 March 2018, Vol.738, pp.363-371
    Description: A powder metallurgy route which is characterized by the vacuum solid state sintering is utilized to fabricate Fe-20Cr-3C and Fe-20Cr-3C-2Mo-3V-2Co ultra high-carbon martensitic stainless steels. A sintering window from 1190 °C to 1210 °C is chosen to obtain high density samples and avoid liquid phase simultaneously. The densification process is promoted by solubility effect during formation of M C and grain boundary diffusion. TEM analysis demonstrates three types of reaction products: the La(BO ) phase, the La O phase and the La(Fe V )O phase, after adding 0.1 wt% LaB . The impurity elements such as S and O are absorbed following the LaB addition to form non-gaseous products, which promotes densification by decreasing the sintering resistance and thus contributes to the improvement of bending strength and hardness. Both of the electrochemical and immersion results lead to the fact that the corrosion resistance of the steels are improved by 0.1 wt% LaB addition, in 3.5 wt% NaCl solution. However, the corrosion resistance of Fe-20Cr-3C-0.1LaB still can not compete with that of 316L stainless steel. Nevertheless, Fe-20Cr-3C-2Mo-3V-2Co and Fe-20Cr-3C-2Mo-3V-2Co-0.1LaB after quenching at high temperature present comparable corrosion resistance with that of 316L in 3.5 wt% NaCl solution.
    Keywords: In Situ Synthesis ; Vacuum Solid State Sintering ; Ultra High-Carbon Martensitic Stainless Steel ; Lab6 ; Mechanical Properties ; Corrosion Resistance ; Engineering ; Chemistry ; Physics
    ISSN: 0925-8388
    E-ISSN: 1873-4669
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