Assimilation of ASAR data with a hydrologic and semi-empirical backscattering coupled model to estimate soil moisture

The most promising approach for studying soil moisture is the assimilation of observation data and computational modeling.However,there is much uncertainty in the assimilation process,which affects the assimilation results.This research developed a one-dimensional soil moisture assimilation scheme based on the Ensemble Kalman Filter(EnKF)and Genetic Algorithm(GA).A two-dimensional hydrologic model-Distributed Hydrology-Soil-Vegetation Model(DHSVM)was coupled with a semi-empirical backscattering model(Oh).The Advanced Synthetic Apertture Radar(ASAR)data were assimilated with this coupled model and the field observation data were used to validate this scheme in the soil moisture assimilation experiment.In order to improve the assimilation results,a cost function was set up based on the distance between the simulated backscattering coefficient from the coupled model and the observed backscattering coefficient from ASAR.The EnKF and GA were used to re-initialize and re-parameterize the simulation process,respectively.The assimilation results were compared with the free-run simulations from hydrologic model and the field observation data.The results obtained indicate that this assimilation scheme is practical and it can improve the accuracy of soil moisture estimation significantly.     

Comprehensive measurement for carrying capacity of resources and environment of city clusters in central China

Studying the carrying capacity of resources and environment of city clusters in the central China has impor-tant practical guidance significance for promoting the healthy,sustainable and stable development of this region.Ac-cording to their influencing factors and reciprocity mechanism,using system dynamics approaches,this paper built a SD model for measuring the carrying capacity of resources and environment of the city clusters in the central China,and through setting different development models,the comprehensive measurement analysis on the carrying capacity was carried out.The results show that the model of promoting socio-economic development under the protection of resources and environment is the optimal model for promoting the harmony development of resources,environment,society and economy in the city clusters.According to this model,the optimum population scale of the city clusters in2020 is 42.80×106 persons,and the moderate economic development scale is 22.055× 1012 yuan(RMB).In 1996-2020,the carrying capacity of resources and environment in the city clusters took on obvious phase-change characteristics.During the studied period,it is basically at the initial development stage,and will come through the development process from slow development to speedup development.     

Response of regeneration diversity of <Emphasis Type="Italic">Carex Lasiocarpa</Emphasis> community to different water levels in Sanjiang Plain,China

The species diversity at the regeneration stage, inflenced by different water levels, is important for community composition in the later growing season. Regeneration diversity of Carex lasiocarpa community under different water levels was studied at two stages, recruitment and adult, in the Sanjiang Plain, Heilongjiang Province, China. The results showed that, at the two growing stages, important value of C. lasiocarpa population and species richness of the community decreased with the increasing water level, while the Simpson and Shannon-Wiener diversity indexes and Pielou evenness index increased. Under different water levels, community diversities were higher at the recruitment stage, while population important values of C. lasiocarpa were higher at the adult stage. Indexes in vegetation evaluation must be chosen prudentially for successful restoration and effective management of wetlands, and especially for wetland restoration, the optimal time should be selected according to the restoration objectives and costs.     

Estimation on Aesthetic Value of Tourist Landscapes in a Natural Heritage Site： Kanas National Nature Reserve, Xinjiang, China

Most world natural heritage sites are designated partly by reason of their prominent aesthetic values in accordance with Article Ⅶ of World Natural Heritage Convention.In this paper, the aesthetic values of Kanas National Nature Reserve, which has potential for such designation, was analyzed quantitatively using scenic beauty estimation(SBE).The landscapes of 19 representative scenic spots in the Kanas National Nature Reserve in summer and autumn were selected as the objects of evaluation.The contributions of different landscape factors to the aesthetic value of the Kanas National Nature Reserve were revealed using a multivariate quantitative model.The main factors affecting the aesthetic value were waterscapes, vegetation, mountains, folk culture and the tourist environment.The t-test and F-test results are extremely significant.According to the results, some suggestions were given for conserving the landscapes in the Kanas National Nature Reserve.     

Relationship between North Pacific SST anomalies and the atmospheric circulation anomalies in January 2008

Based on the NCEP (National Centers for Environmental Prediction) data, the relationship between the Sea Surface Temperature Anomalies (SSTAs) in the North Pacific and the atmospheric circulation anomalies in January 2008 is analyzed in this study. The SSTA mode most correlated with the Geopotential Height anomalies (GHAs) in January 2008 in the North Pacific exhibited a basin-wide horseshoe pattern with a warm center in November 2007. This persistent SSTA pattern would induce positive GHAs in the Aleutian Low area and East Asia and the northward extension of the West Pacific Subtropical High in January 2008 by maximum diabatic heating in the atmosphere over the Kuroshio Oyashio Extension (KOE) area, leading to the occurence of the circumpolar trough-ridge wave train anomaly in January 2008.     

Soil physicochemical properties and vegetation structure along an elevation gradient and implications for the response of alpine plant development to climate change on the northern slopes of the Qilian Mountains

Elevation is one of key factors to affect changes in the environment, particularly changes in conditions of light, water and heat. Studying the soil physicochemical properties and vegetation structure along an elevation gradient is important for understanding the responses of alpine plants andtheir growing environment to climate change. In this study, we studied plant coverage, plant height, species richness, soil water-holding capacity, soil organic carbon(SOC) and total nitrogen(N) on the northern slopes of the Qilian Mountains at elevations from2124 to 3665 m. The following conclusions were drawn:(1) With the increase of elevation, plant coverage and species richness first increased and then decreased, with the maximum values being at 3177 m.Plant height was significantly and negatively correlated with elevation(r=–0.97, P0.01), and the ratio of decrease with elevation was 0.82 cm·100 m-1.(2) Both soil water-holding capacity and soil porosity increased on the northern slopes of the Qilian Mountains with the increase of elevation. The soil saturated water content at the 0-40 cm depth first increased and then stabilized with a further increase of elevation, and the average ratio of increase was2.44 mm·100 m-1. With the increase of elevation, the average bulk density at the 0-40 cm depth first decreased and then stabilized at 0.89 g/cm3.(3) With the increase of elevation, the average SOC content at the 0-40 cm depths first increased and then decreased,and the average total N content at the 0-40 cm depth first increased and then stabilized. The correlation between average SOC content and average total N content reached significant level. According to the results of this study, the distribution of plants showed a mono-peak curve with increasing elevation on the northern slopes of the Qilian Mountains. The limiting factor for plant growth at the high elevation areas was not soil physicochemical properties, and therefore,global warming will likely facilitate the development of plant at high elevation areas in the Qilian Mountains.     

Assessments on slope instabilities triggered by engineering excavations near a small settlement (Turkey)

In this study, the mechanisms of slope instabilities triggered by engineering excavations at location of a planned tunnel portal in the northwest region of Turkey were assessed, and stability of the current slopes which has impacts on safety of a settlement (village) and agricultural fields was investigated. In the first stage of the study, in order to identify the geological units and structural properties of the sedimentary rocks in the area, to clarify the mechanisms of instabilities and to characterize discontinuity and rock mass properties field works were conducted. In this content, geotechnical boreholes, geophysical explorations between the boreholes, line surveys to explore discontinuity properties, preparation of slope profiles using topographical techniques and sampling of rock blocks and discontinuity planes were performed. In the second stage, laboratory tests were carried out on the samples to determine the geomechnical properties of the slope forming materials and discontinuities. Then, back analyses of the instabilities were made to assess the responsible shear strength parameters of the geological units during failures by considering laboratory shear test results too. Based on the backanalyses of the failures, the strength properties of the slope debris were estimated, and it has been clarified that the residual shear strength properties are the factors controlling slip mechanism along the beddings. Following the stability analyses, it is understood that a further instability along the mass or bedding planes in the failed and redesigned area are not expected, if the current slope geometry is not changed. However, safety factor calculated for the slope in the debris is 1.1 which is well below the recommended value in the literature. The minimum safety factor for currently stable slopes which were cut at the eastern part of the failed area is 1.22 which is also less than that suggested in literature. Some remedial measures such as mini-pile or slope flattening are suggested after analyses to increase the factor of safety for this part below the settlement.     

Estimating aboveground biomass using Pléiades satellite image in a karst watershed of Guizhou Province,Southwestern China

Biomass in karst terrain has rarely been measured because the steep mountainous limestone terrain has limited the ability to sample woody plants.Satellite observation, especially at high spatial resolution, is an important surrogate for the quantification of the biomass of karst forests and shrublands. In this study, an artificial neural network(ANN) model was built using Pléiades satellite imagery and field biomass measurements to estimate the aboveground biomass(AGB) in the Houzhai River Watershed, which is a typical plateau karst basin in Central Guizhou Province, Southwestern China. A back-propagation ANN model was also developed.Seven vegetation indices, two spectral bands of Pléiades imagery, one geomorphological parameter,and land use/land cover were selected as model inputs. AGB was chosen as an output. The AGB estimated by the allometric functions in 78 quadrats was utilized as training data(54 quadrats, 70%),validation data(12 quadrats, 15%), and testing data(12 quadrats, 15%). Data-model comparison showed that the ANN model performed well with an absolute root mean square error of 11.85 t/ha, which was 9.88%of the average AGB. Based on the newly developed ANN model, an AGB map of the Houzhai River Watershed was produced. The average predicted AGB of the secondary evergreen and deciduous broadleaved mixed forest, which is the dominant forest type in the watershed, was 120.57 t/ha. The average AGBs of the large distributed shrubland,tussock, and farmland were 38.27, 9.76, and 11.69 t/ha, respectively. The spatial distribution pattern ofthe AGB estimated by the new ANN model in the karst basin was consistent with that of the field investigation. The model can be used to estimate the regional AGB of karst landscapes that are distributed widely over the Yun-Gui Plateau.     

Assessment of prospective hazards resulting from the 2017 earthquake at the world heritage site Jiuzhaigou Valley,Sichuan, China

On August 8, 2017, a Ms = 7.0 magnitude earthquake occurred in the Jiuzhaigou Valley, in Sichuan Province, China(N: 33.20°, E: 103.82°). Jiuzhaigou Valley is an area recognized and listed as a world heritage site by UNESCO in 1992. Data analysis and field survey were conducted on the landslide, collapse, and debris flow gully, to assess the coseismic geological hazards generated by the earthquake using an unmanned aerial vehicle(UAV), remote-sensing imaging, laser range finders, geological radars, and cameras. The results highlighted the occurrence of 13 landslides, 70 collapses, and 25 potential debris flow gullies following the earthquake. The hazards were classified on the basis of their size and the potential property loss attributable to them. Consequently, 14 large-scale hazards, 30 medium-sized hazards, and 64 small hazards accounting for 13%, 28%, and 59% of the total hazards, respectively, were identified. Based on the variation tendency of the geological hazards that ensued in areas affected by the Kanto earthquake(Japan), Chi-chi earthquake(Taiwan China), and Wenchuan earthquake(Sichuan China), the study predicts that, depending on the rain intensity cycle, the duration of geological hazard activities in the Jiuzhaigou Valley may last over ten years and will gradually decrease for the following five to ten yearsbefore returning to pre-earthquake levels. Thus,necessary monitoring and early warning systems must be implemented to ensure the safety of residents,workers and tourists during the construction of engineering projects and reopening of scenic sites to the public.     

Iron Regulation of Wetland Vegetation Performance Through Synchronous Effects on Phosphorus Acquisition Efficiency

Iron-rich groundwater flowing into wetlands is a worldwide environmental pollution phenomenon that is closely associated with the stability of wetland ecosystems. Combined with high phosphorus(P) loading from agricultural runoff, the prediction of the evolution of wetland vegetation affected by compound contamination is particularly urgent. We tested the effects of anaerobic iron-rich groundwater discharge in a freshwater marsh by simulating the effect of three levels of eutrophic water on native plants(Glyceria spiculosa(Fr. Schmidt.) Rosh.). The management of wetland vegetation with 1–20 mg/L Fe input is an efficient method to promote the growth of plants, which showed an optimum response under a 0.10 mg/L P surface water environment. Iron-rich groundwater strongly affects the changes in ecological niches of some wetland plant species and the dominant species. In addition, when the P concentration in a natural body of water is too high, the governance effect of eutrophication might not be as expected. Under iron-rich groundwater conditions, the δ~(13)C values of organs were more depleted, which can partially explain the differences in δ~(13)C in the soil profile. Conversely, the carbon isotope composition of soil organic carbon is indicative of past changes in vegetation. The results of our experiments confirm that iron-rich groundwater discharge has the potential to affect vegetation composition through toxicity modification in eutrophic environments.