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temporal stability analysis of soil moisture along a coniferous forest hillslope with subtropical monsoon climate in southwest China

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Journal of Mountain Science 2021年第11期18卷 2900-2914页

作者： BAI Yu-shi LIU Mu-xing YI Jun ZHANG Hai-lin Hubei Province Laboratory for Geographical Process Analyzing&Modeling Wuhan 430079China College of Urban and Environmental Sciences Central China Normal UniversityWuhan 430079China Research Institute of Sustainable Development Central China Normal UniversityWuhan 430079China

Soil water content(SWC)plays a crucial role in simulating hydrological process,guiding reforestation and controlling soil erosion in mountainous regions.Spatial-temporal variability of SWC increases the difficulty of quantifying SWC pattern in the prediction of soil moisture.temporal stability analysis of SWC can reduce the labor consuming and simplify the costly field monitoring.This study aimed to evaluate the temporal stability of SWC at hourly,daily and monthly temporal periods and its controlling factors at a hillslope in the Three Gorges region.The SWC of five soil depths was monitored at 5 topographic locations(toe,lower,middle,upper and top slope positions)along a 170 m hillslope in the Three Gorges region(110°04'~112°04'E,29°53'~31°34'N),Yichang City,Hubei Province,China from May 4^(th),2018 to May 3^(rd),2019.The results showed thatthe coefficient of variation of SWC ranged from 4%to 49%,which increased with rising soil depth within 40 cm but thereafter decreased.However,the high Spearman's rank coefficients(Ptemporal stability at three temporal periods.Therepresentative locations(RLs)varied in the different soil depths,which weretoe,upper and middle slope positions at 0~40,40~60 and 60~80 cm depthsof the investigated hillslope,respectively.Saturated hydraulic conductivity served as adominant factor controlling the temporal stability of SWC.The result advances our thorough understanding of hydrology and soil water resource in the Three Gorges region.

关键词： Soil water content temporal stability Representative location Hillslope hydrology temporal period Three Gorges region

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Using random-parameter and fixed-parameter ordered models to explore temporal stability in factors affecting drivers' injury severity in single-vehicle collisions

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Journal of Traffic and Transportation Engineering(English Edition) 2019年第2期6卷 132-146页

作者： Essam Dabbour Murtaza Haider Eman Diaa College of Engineering Abu Dhabi University Ted Rogers School of Management Ryerson University

Understanding the temporal stability in the factors influencing drivers' injury severity in single-vehicle collisions would help evaluating the effectiveness of implementing different safety treatments so that researchers could understand whether any safety improvements,observed after applying a certain safety treatment, are attributed to the specific treatment or simply attributed to the temporal instability of the factors being addressed. This study investigates the temporal stability of the factors affecting drivers' injury severity in singlevehicle collisions involving light-duty vehicles. The study is based on utilizing ordinal regression modeling to analyze the severity of drivers' injuries in all police-reported lightduty single-vehicle collisions that occurred in North Carolina from January 1, 2007, to December 31, 2013. A separate regression model was estimated for each year so that statistical significance of each risk factor may be compared over the years. The study also estimated random-parameter(mixed) ordered logit models to explore the heterogeneity in data. The most significant factor that was found to increase the severity of drivers' injuries in light-duty single-vehicle collisions is driving under the influence of alcohol or illicit drugs. Other significant factors, in decreasing order in terms of their significance, include driving on a highway curve, exceeding speed limit, lighting conditions, the age of the driver, and the age of the vehicle. In contrast, there were six factors that were found to be significant in only some years and not in all years. These six temporally unstable factors include the use of seatbelt, driver's gender, rural highways, undivided highways, the type of the light-duty vehicle, and weather and road surface conditions. These same factors were found by other previous research studies to be significant and stable predictors of drivers' injury severity in single-vehicle collisions.

关键词： Drivers' injury severity Single-vehicle collisions Ordinal regression models Mixed logit models temporal stability

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Coherent States of Nonlinear Oscillators with Position-Dependent Mass:temporal stability and Fractional Revivals

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Communications in Theoretical Physics 2017年第8期68卷 181-190页

作者： Naila Amir Shahid Iqbal School of Electrical Engineering and Computer Sciences National University of Sciences and Technology Department of Physics School of Natural Sciences National University of Sciences and Technology

We develop generalized coherent states for a class of nonlinear oscillators with position-dependent effective mass in the context of the Gazeau–Klauder formalism and discuss some of their properties. In order to investigate the temporal evolution we first explore the statistical properties by means of weighting distribution and the Mandel parameter. It is found that the temporal evolution of the coherent states may exhibit the phenomena of quantum revivals and fractional revivals for a particular choice of position-dependent mass oscillator.

关键词： position-dependent effective mass nonlinear oscillators Gazeau–Klauder coherent states Mandel parameter sub-Poissonian statistics temporal stability quantum revivals fractional revivals

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Understanding temporal stability:a long-term analysis of USDA ARS watersheds

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International Journal of Digital Earth 2021年第10期14卷 1243-1254页

作者： Evan J.Coopersmith Michael H.Cosh Patrick J.Starks David D.Bosch Chandra Holifield Collins Mark Seyfried Stan Livingston John Prueger Soil Insight LLCWashington D.C.USA USDA-Agricultural Research Service Beltsville Agricultural Research CenterHydrology and Remote Sensing LaboratoryBeltsvilleUSA USDA-Agricultural Research Service-Grazinglands Research Laboratory El RenoUSA USDA-Agricultural Research Service-Southeast Watershed Research Laboratory TiftonUSA USDA-Agricultural Research Service-Southwest Watershed Research Center TucsonUSA USDA-Agricultural Research Service-Northwest Watershed Research Laboratory BoiseUSA USDAAgricultural Research Service-National Soil Erosion Research Laboratory West LafayetteUSA USDA-Agricultural Research Service-National Laboratory for Agriculture and Environment AmesUSA

The U.S.Department of Agriculture’s Agricultural Research Service(USDAARS)maintains seven in situ soil moisture networks throughout the continental United States,some since 2002.These networks are crucial for understanding the spatial and temporal extent of droughts in their historical context,parameterization of hydrologic models,and local agricultural decision support.However,the estimates from these networks are dependent upon their ability to provide reliable soil moisture information at a large scale.It is also not known how many network stations are sufficient to monitor watershed scale dynamics.Therefore,the objectives of this research were to:(1)determine how temporally stable these networks are,including the relationships between various sensors on a year-to-year and seasonal basis,and(2)attempt to determine how many sensors are required,within a network,to approximate the full network average.Using data from seven in situ,it is concluded that approximately 12 soil moisture sensors are sufficient in most environments,presuming their locations are distributed to capture the hydrologic heterogeneity of the watershed.It is possible to install a temporary network containing a suitable number of sensors for an appropriate length of time,glean stable relationships between locations,and retain these insights moving forward with fewer sensor resources.

关键词： Soil moisture temporal stability in situ networks

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Rapid loss of leguminous species in the semi-arid grasslands of northern China under climate change and mowing from 1982 to 2011

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Journal of Arid Land 2020年第5期12卷 752-765页

作者： XU Bo HUGJILTU Minggagud BAOYIN Taogetao ZHONG Yankai BAO Qinghai ZHOU Yanlin LIU Zhiying Ministry of Education Key Laboratory of Ecology and Resource Use of the Mongolian Plateau&Inner Mongolia Key Laboratory of Grassland Ecology School of Ecology and EnvironmentInner Mongolia UniversityHohhot 010021China

Effects of mowing on the composition and diversity of grasslands varied with climate change(e.g.,precipitation and temperature).However,the interactive effects of long-term mowing and climate change on the diversity and stability of leguminous and non-leguminous species in the semi-arid grasslands are largely unknown.Here,we used in situ monitoring data from 1982 to 2011 to examine the effects of continuous mowing and climate change on the plant biomass and diversity of leguminous and non-leguminous species,and soil total nitrogen in the typical semi-arid grasslands of northern China.Results showed that the biomass and diversity of leguminous species significantly decreased with the increasing in the biomass and diversity of non-leguminous species during the 30-a period.Variations in biomass were mainly affected by the long-term mowing,while variations in diversity were mainly explained by the climate change.Moreover,the normalized change rates of diversity in leguminous species were significantly higher than those in non-leguminous species.Mowing and temperature together contributed to the diversity changes of leguminous species,with mowing accounting for 50.0%and temperature 28.0%.temporal stability of leguminous species was substantially lower than that of non-leguminous species.Consequently,soil total nitrogen decreased in the 2000s compared with the 1980s.These findings demonstrated that leguminous species were more sensitive to the long-term mowing and climate change than non-leguminous species in the semi-arid grasslands.Thus,reseeding appropriate leguminous plants when mowing in the semi-arid grasslands may be a better strategy to improve nitrogen levels of grassland ecosystems and maintain ecosystem biodiversity.

关键词： climate change diversity legume mowing productivity succession temporal stability

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Drought sensitivity of beech on a shallow chalk soil in northeastern Germany - a comparative study

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Forest Ecosystems 2017年第1期4卷 45-54页

作者： Marieke van der Maaten-Theunissen Hanna Bummerstede Janette Iwanowski Tobias Scharnweber Martin Wilmking Ernst van der Maaten Institute of Botany and Landscape Ecology University of Greifswald Soldmannstr 15 17487 Greifswald Germany

Background： We compare the climate sensitivity of European beech （Fagus sylvatica L.） in two forest nature reserves in northeastern Germany. The one reserve, Schlossberg, is characterized by shallow chalk soils, whereas in the other reserve, EIdena, soils are deeper and more developed. Little is known about the drought sensitivity of beech on shallow chalk soils. Methods： We collected increment cores at both research sites and established climate-growth relationships. Inter- tree variability was assessed by employing linear mixed-effect models. Results： We expected to find distinctively higher drought sensitivity at Schlossberg due to limited water availability, but find only marginal differences in growth responses. At both sites, drought is the major climatic factor driving tree growth. Adaptations in tree architecture and an underestimation of the water holding capacity of shallow chalk soils are discussed as possible reasons for not finding more distinct climate responses. In analyzing climate-growth relationships, we specifically focused on growth responses of individual trees but observed only low inter-tree variability at both sites. Evident is a shift in climate response patterns from the first to the second half of the twentieth century with previous-year drought conditions becoming more important than current-year drought. This shift is discussed in relation to a warming trend over that same period, as well as possible trends in masting behavior of beech. Conclusion： The investigated beech trees on the shallow chalk soil are only slightly more drought sensitive than beech trees on the reference site with deeper and more developed soils.

关键词： Climate-growth relationships Dendroecology Inter-tree variability temporal stability Drought stress

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Phylogenetic diversity stabilizes community biomass

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Journal of Plant Ecology 2014年第2期7卷 176-187页

作者： Zhichao Pu Poonim Daya Jiaqi Tan Lin Jiang School of Biology Georgia Institute of Technology310 Ferst DriveAtlantaGA 30332USA Division of Biology California Institute of Technology1300 E California BoulevardPasadenaCA 91126USA

Aims The relationship between biodiversity and ecological stability is a long-standing issue in ecology.Current diversity–stability studies,which have largely focused on species diversity,often report an increase in the stability of aggregate community properties with increasing species diversity.Few studies have examined the linkage between phylogenetic diversity,another important dimension of biodiversity,and stability.By taking species evolutionary history into account,phylogenetic diversity may better capture the diversity of traits and niches of species in a community than species diversity and better relate to temporal stability.In this study,we investigated whether phylogenetic diversity could affect temporal stability of community biomass independent of species diversity.Methods We performed an experiment in laboratory microcosms with a pool of 12 bacterivorous ciliated protist species.To eliminate the possibility of species diversity effects confounding with phylogenetic diversity effects,we assembled communities that had the same number of species but varied in the level of phylogenetic diversity.Weekly disturbance,in the form of short-term temperature shock,was imposed on each microcosm and species abundances were monitored over time.We examined the relationship between temporal stability of community biomass and phylogenetic diversity and evaluated the role of several stabilizing mechanisms for explaining the influence of phylogenetic diversity on temporal stability.Important Findings Our results showed that increasing phylogenetic diversity promoted temporal stability of community biomass.Both total community biomass and summed variances showed a U-shaped relationship with phylogenetic diversity,driven by the presence of large,competitively superior species that attained large biomass and high temporal variation in their biomass in both low and high phylogenetic diversity communities.Communities without these species showed patterns consistent with the reduced strength of competition and increasingly

关键词： biodiversity environmental fluctuation the insurance effect phylogenetic diversity temporal stability

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An Investigation into the Role of Capping on Second Harmonic Generation from Nonlinear Organic Polymer and Guest-Host Thin Films by In-Situ Poling

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Optics and Photonics Journal 2016年第5期6卷 101-111页

作者： P. M. Ushasree M. Szablewski Department of Physics and Electrical Engineering Northumbria University Newcastle upon Tyne UK Department of Physics Durham University Durham UK

In attempts to fabricate thermally stable second-order nonlinear polymer thin films, we have investigated the second harmonic generation (SHG) from both nonlinear polymer and guest-host thin films. We have also investigated the role of capping on the SHG, temporal stability and relaxation of dipole alignment. Corona poling techniques were employed to orient the dopants into the noncentrosymmetric structure required to obtain the SHG. The effect of capping with a polymeric encapsulant below the glass transition temperature of the polymers on the unpoled and corona poled thin films was studied. Capping of the nonlinear polymer and guest host thin films have resulted in high SHG with good temporal stability. SHG signal falls drastically during the first 8 days after poling while no further significant decay in SHG signal was observed after about 33 days. Our investigations have identified the characteristics required for a good encapsulant on a non-con-ductive surface.

关键词： Second Harmonic Generation Nonlinear Polymer Thin Films Guest-Host Thin Films Capping temporal stability Corona Poling

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