Corridor effect of the spatial changes of landscape patterns in arid areas:A case study of the river corridor areas in the middle and lower reaches of Tarim River

在 Tarim Riverare 的中间、更低的活动范围的河走廊区域在 Ruoqiang 从 Qara 水库 inYuli 县沿着河节由传统的绿走廊统治了到泰泰马·莱克县，它在 Tarim 河分水岭在社会、经济的发展起一个重要作用与一极其重要的生态的功能。对水路垂直的缓冲区地区从水路在 5-kminterval 开始沿着两个河边被定义(10 km 更宽) 用缓冲区地区分析的方法。每个缓冲区地区的风景模式索引被计算，并且主要风景模式的索引被分析以便在风景和补丁层次上揭示放射的效果和河走廊的特征。放射的宽度通常是在学习区域的 30 km 的结果表演，和罐头直到在潜水艇的 50-70 km -- 区域 FG1 因为学习区域位于二排水盆，与在他们之间的一个生态的空隙的地区。树林和沼泽地的 Thelandscapes 通常在 10 km 缓冲区地区以内被散布(它意味着缓冲区地区是离开水路的 5 km；一样此后) 沿着两个河边。而且，缓冲区地区越靠近到水路，补丁密度和最大的补丁索引是越多 higher。在为学习区域的生态、环境的新生，河走廊的生态的效果的程度必须充分被考虑，并且工程必须科学地并且讲道理地被计划并且设计。

Changes in groundwater levels and the response of natural vegetation to transfer of water to the lower reaches of the Tarim River

Restoration and reconstruction of the degraded Tarim River ecosystem is an important challenge. A goal of an ecological water conveyance project is to protect and restore the natural vegetation in the lower reaches of Tadm River by transferring water from Bosten Lake, through the river channel, to the lower reaches. This study describes the changes in groundwater depth during the water transfer and the respondence of riparian vegetation to alterations in groundwater levels. The results indicate that groundwater depth along the Tarim River channel has a significant spatial-temporal component. Groundwater levels closest to the river channel show the most immediate and pronounced changes as a response to water transfer while those further away respond more slowly, although the observed change appears to be longer in duration. With a rise in the groundwater level, natural vegetation responded with higher growth rates, biomass and biodiversity. These favorable changes show that it is feasible to protect and restore the degraded natural vegetation by raising the groundwater depth. Plant communities are likely to reflect the hysteresis phenomenon, requiting higher water levels to initiate and stimulate desired growth than what may be needed to maintain the plant community. Because different species have different ecologies, including different root depths and densities and water needs, their response to increasing water availability will be spatially and temporally heterogenous. The response of vegetation is also influenced by microtopography and watering style. This paper discusses strategies for the protection and restoration of the degraded vegetation in the lower reaches of the Tarim River and provides information to complement ongoing theoretical research into ecological restoration in add or semi-arid ecosystems.

Precipitation cycles in the middle and lower reaches of the Yellow River （1736-2000）

Based on the long-term precipitation series with annual time resolution in the middle and lower reaches of the Yellow River and its four sub-regions during 1736-2000 reconstructed from the rainfall and snowfall archives of the Qing Dynasty, the precipitation cycles are analyzed by wavelet analysis and the possible climate forcings, which drive the precipitation changes, are explored. The results show that： the precipitation in the middle and lower reaches of the Yellow River has inter-annual and inter-decadal oscillations like 2-4a, quasi-22a and 70-80a. The 2-4a cycle is linked with El Nino events, and the precipitation is lower than normal year in the occurrence of the El Nino year or the next year; for the quasi-22a and the 70-80a cycles, Wolf Sun Spot Numbers and Pacific Decadal Oscillation （PDO） coincide with the two cycle signals. However, on a 70-80a time scale, the coincidence between solar activity and precipitation is identified before 1830, and strong （weak） solar activity is generally correlated to the dry （wet） periods; after 1830, the solar activity changes to 80-100a quasi-century long oscillation, and the adjusting action to the precipitation is becoming weaker and weaker; the coincidence between PDO and precipitation is shown in the whole time series. Moreover, in recent 100 years, PDO is becoming a pace-maker of the precipitation on the 70-80a time scale.

Organic Phosphorus in Shallow Lake Sediments in Middle and Lower Reaches of the Yangtze River Area in China

Thirteen sediment core samples(0-10 cm) were taken from the seven lakes in the middle and lower reaches of the Yangtze River to determine the contents and distributions of organic phosphorus(P) fractions in the sediments of the shallow lakes in the area.The organic P fractions in the sediments were in the order of moderately labile organic P(MLOP) > moderately resistant organic P(MROP) > highly resistant organic P(HROP) > labile organic P(LOP),with average proportional ratios of 13.2:2.8:1.3:1.0.LOP,MLOP,and MROP were significantly related to the contents of total organic carbon(TOC),water-soluble P(WSP),algal-available P(AAP),NaHCO3-extractable P(Olsen-P),total P(TP),organic P(OP),and inorganic P(IP).However,HROP was significantly related to OP and weakly correlated with TOC,WSP,AAP,Olsen-P,TP or IP.This suggested that organic P,especially LOP and MLOP in sediments,deserved even greater attention than IP in regards to lake eutrophication.In terms of organic P,sediments were more hazardous than soils in lake eutrophication.Although OP concentrations were higher in moderately polluted sediment than those in heavily polluted sediment,LOP and MLOP were higher in the heavily polluted sediment,which indicated that heavily polluted sediment was more hazardous than moderately polluted sediment in lake eutrophication.

Research on Methods of Ecological Security Assessment of the Middle and Lower Reaches of Liaohe River Based on GIS

Ecological security assessment and early warning research possess the attributes of spatiality, non-linearity and randomicity, so we must process much spatial information. Spatial analysis and data management are the advantages of GIS, which can define distribution trend and spatial relations of environmental factors, and show ecological security pattern graphically. Spatial differences of ecological security assessment based on GIS are discussed in this paper, of which the middle and lower reaches of the Liaohe River is taken as a study case. First, to work out pressure-state-response (P-S-R) assessment indicators system, and investigate in person and gather information; second, to digitize the watershed; third, to quantize and calculate by the fuzzy method; last, to construct GIS grid database, and expound spatial differences of ecological security by GIS interpolation and assembly analysis.

Summertime temperature variations in the middle and lower reaches of Yangtze River and their related circulation anomalies in the past five decades

Using the daily data of temperature from China Meteorological Administration and the NCEP/NCAR reanalysis from 1960 to 2005, we have analyzed the relationships between the summertime high/low temperature events in the middle and lower reaches of the Yangtze River （MLRYR） and the related circulation anomalies in the Eastern Hemisphere. Our results have demonstrated that a significantly increasing trend is observed in daily minimum temperature in the past 50 years. And in some regions in the Northern Hemisphere, the opposite scenarios are observed in circulation anomalies in lower and upper parts of the troposphere in the years when the temperatures are higher than normal, as compared to those in the years when the temperatures are lower than normal in the middle and lower reaches of the Yangtze River （MLRYR）. Additionally, the anomalous circulation structure in vertical direction in both the high and lower temperature years are barotropic. It is found that the emergence and maintenance of the aforementioned anomalous circulations are related to three kinds of wave train teleconnection patterns. Further more, influences of the long wave surface radiation on the air temperature are stronger in the nighttime than that in the daytime. While both the maximum and minimum temperatures have negative relationships with the sensible heat flux but positive relationships with the latent heat flux. To some extent, the anomalous dynamic heating （cooling） caused by the vertical thermal advection as well as the diabatic heating （cooling） caused by diabatic processes can explain the formation of the high （low） temperature events in the middle and lower reaches of the Yangtze River （MLRYR） in boreal summer.

The Background Features and Formation of Chemical Elements of Groundwater in the Region of the Middle and Lower Reaches of the Yangtze River

The paper deals with the background features, formation and distribution of the chemical el-ements K, Na, Ca, Mg, Si, Fe, Mn, Cr, Ni,V, Co, Ti, Mo, Cu, Pb, Zn, As, Hg, Cd, Be, Li, Sr, B,F, Cl, Br and I in the groundwater in the region of the middle and lower reaches of the YangtzeRiver and their relations to the composition of the water-bearing media, properties of the overly-ing rocks and soils, redox environment, and groundwater flow condition, mineralization and pHof groundwater.

Basement Characteristics and Crustal Evolution of the Copper-Gold Metallogenic Belt in the Middle and Lower Reaches of the Yangtze River:Some Isotope Constraints

Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has “two-layer structure” and partly has “multi-layered structure”, and is inhomogeneous and shows the distinct feature of E-W provincialism. The calculated model lead ages (t1) are mostly greater than 2600 Ma, and the model neodymium ages (TDM) vary from 953 to 2276 Ma and concentrate in two time intervals: 1800–2000 Ma and 1200–1600 Ma. It is concluded that the basement of the MBYR is composed of the Late Archaeozoic to Middle Proterozoic metamorphic series and that the crust was initiated in the Archaean and continued to grow in the Early and Middle Proterozoic, and the proportion of new crust formed by mantle differentiation during the Late Proterozoic is low.

Three-dimensional P-wave Velocity Structure Modelling of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt: Crustal Architecture and Metallogenic Implications

In this study,we compiled and analyzed 69310 P-wave travel-time data from 6639 earthquake events.These events(M≥2.0)occurred from 1980 s to June 2019 and were recorded at 319 seismic stations(Chinese Earthquake Networks Center)in the study area.We adopted the double-difference seismic tomographic method(tomo DD)to invert the 3-D P-wave velocity structure and constrain the crust-upper mantle architecture of the Middle and Lower Reaches of the Yangtze River Metallogenic Belt(MLYB).A 1-D initial model extracted from wide-angle seismic profiles was used in the seismic tomography,which greatly reduced the inversion residual.Our results indicate that reliable velocity structure of th e uppermost mantle can be obtained when Pn is involved in the tomography.Our results show that:(1)the pattern of the uppermost mantle velocity structure corresponds well with the geological partitioning:a nearly E-W-trending low-velocity zone is present beneath the Dabie Orogen,in contrast to the mainly NE-trending low-velocity anomalies beneath the Jiangnan Orogen.They suggest the presence of thickened lower crust beneath the orogens in the study area.In contrast,the Yangtze and Cathaysia blocks are characterized by relatively high-velocity anomalies;(2)both the ultra-high-pressure(UHP)metamorphic rocks in the Dabie Orogen and the low-pressure metamorphic rocks in the Zhangbaling dome are characterized by high-velocity anomalies.The upper crust in the Dabie Orogen is characterized by a low-velocity belt,sandwiched between two high velocity zones in a horizontal direction,with discontinuous low-velocity layers in the middle crust.The keel of the Dabie Orogen is mainly preserved beneath its northern section.We infer that the lower crustal delamination may have mainly occurred in the southern Dabie Orogen,which caused the mantle upwelling responsible for the formation of the granitic magmas emplaced in the middle crust as the low-velocity layers observed there.Continuous deep-level compression likely squeezed the granitic magma upward to intrude the upper crustal UHP metamorphic rocks,forming the'sandwich'velocity structure there;(3)high-velocity updoming is widespread in the crust-mantle transition zone beneath the MLYB.From the Anqing-Guichi ore field northeastward to the Luzong,Tongling,Ningwu and Ningzhen orefields,high-velocity anomalies in the crust-mantle transition zone increase rapidly in size and are widely distributed.The updoming also exists in the crust-mantle transition zone beneath the Jiurui and Edongnan orefields,but the high-velocity anomalies are mainly stellate distributed.The updoming high-velocity zone beneath the MLYB generally extends from the crust-mantle transition zone to the middle crust,different from the velocity structure in the upper crust.The upper crust beneath the Early Cretaceous extension-related Luzong and Ningwu volcanic basins is characterized by high velocity zones,in contrast to the low velocity anomalies beneath the Late Jurassic to Early Cretaceous compression-related Tongling ore field.The MLYB may have undergone a compressive-to-extensional transition during the Yanshanian(Jurassic-Cretaceous)period,during which extensive magmatism occurred.The near mantle-crustal boundary updoming was likely caused by asthenospheric underplating at the base of the lower crust.The magmas may have ascended through major crustal faults,undergoing AFC(assimilation and fractional crystallization)processes,became emplaced in the fault-bounded basins or Paleozoic sequences,eventually forming the many Cu-Fe polymetallic deposits there.

Assessment and exploitation of the waterfront resources in the middle and lower reaches of the Yangtze River

Waterfront resources are important and special kind of natural resources in the marginal area between land and wat er. The Yangtze River, the longest river in China, is not only rich in waterfront resources, but also has favorable development conditions with gr eat potentiality. Aided by large-scale underwater topographic map, the maj or factors of the waterfront resources in the middle and lower reache s of the Yangtze River, such as the stability, the water depth and the natural conditions for port construction, are assessed in this pap er respectively on the basis of the overall investigations. The result s show that: (1) the waterfront resources are abundant in the middle and lower reaches of the Yangtze River, but lack of perfectly combined high grade waterfront; (2) there exists an obvious regional difference in the natural quality of the waterfront along the Yangtze; (3) the fore-bank water depth and waterfront stability are the main natural fa ctors related to the waterfront quality in the middle and lower reach es of the Yangtze River; (4) the waterfronts along the Yangtze are mainl y used for port, warehouse and industrial purposes; and (5) the waterfronts near important cities are highly used, especially the high-quality waterfronts. In addition, some suggestions for the development and utilization of the waterfron t resources are presented in this paper.

The Background of Regional Lead Isotopic Compositions and Its Application in the Lower and Middle Reaches of the Yangtze River and Neighbouring Areas

The paper systematically deals with the background of regional isotopic compo-sitions in the lower and middle reaches of the Yangtze River and neighbouring areas. It isshown that the lead isotopic compositions of different geological formations and units are con-trolled by the primary mantle heterogeneity, dynamic process of crust-mantle interchange,abundances of uraninm, thorium and lead of various layers of the earth and timing. Studies onthe background of regional isotopic compositions may offer significant information forgeochemical regionalization, tracing of sources of ore-forming materials, and regionalprognosis of ore deposits.

Relationship between the Late Spring NAO and Summer Extreme Precipitation Frequency in the Middle and Lower Reaches of the Yangtze River

The relationship between the late spring North Atlantic Oscillation (NAO) and the summer extreme precipitation frequency (EPF) in the middle and lower reaches of the Yangtze River Valley (MLYRV) is examined using an NECP/NCAR reanalysis dataset and daily precipitation data from 74 stations in the MLYRV. The results show a significant negative correlation between the May NAO index and the EPF over the MLYRV in the subsequent summer. In positive EPF index years, the East Asian westerly jet shifts farther southward, and two blocking high positive anomalies appear over the Sea of Okhotsk and the Ural Mountains. These anomalies are favorable to the cold air from the mid-high latitudes invading the Yangtze River Valley (YRV). The moisture convergence and the ascending motion dominate the MLYRV. The above patterns are reversed in negative EPF index years. A wave train pattern that originates from the North Atlantic extends eastward to the Mediterranean and then moves to the Tibetan Plateau and from there to the YRV, which is an important link in the May NAO and the summer extreme precipitation in the MLYRV. The wave train may be aroused by the tripole pattern of the SST, which can explain why the May NAO affects the summer EPF in the MLYRV.

DEEP THOUGHTS OF LAND UTILIZATION ABOUT THE RARELY SEVERE FLOODING DISASTERALONG THE MIDDLE AND LOWER REACHES OF THE CHANGJIANG RIVER IN 1998

In the summer of 1998, a rarely severe flooding disaster occurred in the whole basin of the Changjiang(Yangtze) River, which caused enormous losses. By 22nd of August, 29 provinces, autonomous regions and municipalitieswere involved, 21. 2 million ha of land were inundated, 223 million people were affected, 3004 people were killed and4. 97 million buildings were collapsed. The estimated direct loss of the country accounted to 166. 6 billion yuan (RMB).The main reason of the disaster is the unusual climate but the unreasonable land utilization the aggravated the disaster.This paper consists of two parts. One part analysed the unreasonable land utilization, including the neglect of forest landprotection, which caused the forest land area to decrease by 440 thousand ha in the whole country every year, the enclosing of lakes for cultivation, which decreased the area of lakes located along the banks of the Changjiang River from 17 200km2 at the beginning of the founding of the People’s Republic of China to 6531 km2 in 1983, the changing of functions oflakes, which reduced the volume of storage exceedingly, for example, only 5 spots of lakes were used for storing water inWuhan City, and the slow progress of the construction of flood diversion and storage area, which would cause huge lossesonce flood was diverted. The other part explored the strategy of land utilization on the supplying of land for flood controlprojects, such as embankment, drainage installation, flood diversion and storage area, and on tapping the potentialsthrough narrowing and amalgamgting the range of rural residential quarters and small towns, reclaiming reserved resources, transforming middle and low productive fields, attaching importance to land arrangement and recultivation, and adjusting contracted fields partially, to ensure the sustainable and stable growth of the region.

The Sustainable Utilization of Lake Resources in the Middle and Lower Reaches of Yangtze River

Based on geographical and hydrological characteristics of lakes in the middle and lower reaches of Yangtze River, this paper analyzes the factors restricting the sustainable utilization of lake resources, including the conflict among agriculture water conservancy, and fishery, lake water pollution and eutrophication, lake siltation and swamping. The countermeasures and suggestions, such as improving the strategic status of lake harnessing, strengthening integrated management of lakes and their watershed, strengthening researches on lake environment and lake resources, are proposed to practice the sustainable utilization of lake resources.

Study on the extremely cold winter of 1670 over the middle and lower reaches of the Yangtze River

The snow-cover days over the middle and lower reaches of the Yangtze River （MLRYR） in the winter of 1670 were extracted from Chinese historical documents. By these records, the winter temperature anomalies （compared to the mean of 1961-1990） recorded at seven meteorological stations and the regional mean winter temperature were estimated. The results show that： （1） There was an average of about 30 snow-cover days over the MLRYR region in 1670, ranging from 11-20 days in Shanghai and eastern Zhejiang to 5140 days in eastern Hunan Province. The snow-cover days averaged about 40 days in Anqing and Nan- cheng, and ranged from 30 to 40 days in Quzhou, Jingdezhen, and Nanchang; and （2） the regional mean winter temperature in 1670 was estimated to be approximately 4.0 ℃ lower than that of 1961-1990. The maximum negative anomaly of 5.6℃ occurred in Nanchang and the minimum anomaly of-2.8 ℃ was detected in Quzhou. Both of these were lower than that of the coldest winter during the instrumental observation period of 1951-2010. This research could not only provide a method to es- timate historical climate extremes, but also provide a background to understand the recent instrumentally climate extremes.

Research and Application of Rainstorm Disaster Risk Assessment along the Middle and Lower Reaches of Yangtze River

We explored and studied rainstorm disaster impact grade. Firstly,we selected average precipitation,precipitation intensity,coverage and duration during rainstorm process,and economic losses,the number of deaths and total casualties in rainstorm disaster situation as the pre-assessment indexes of rainstorm process impact grade along the middle and lower reaches of Yangtze River. Then,normalized and dimensionless processing of each index was conducted. By using gray correlation method,we established rainstorm process grade and rainstorm disaster impact grade. At last,we conducted regression analysis of relevancy degree between rainstorm process grade and rainstorm disaster situation grade,and established a linear relationship between the two,thereby getting a rainstorm disaster pre-assessment method. On this basis,using rainstorm hazard factors in independent sample,we carried out pre-assessment test of disaster impact grade. The results show that this pre-assessment method is quick and easy,and the effect is better.

Analysis of Precipitation in the Middle and Lower Reaches of Yangtze River in the Summer of 2000-2007

Based upon the summer (June-August) precipitation data from 30 stations in the middle and lower reaches of Yangtze River in China, the spatial and temporal distribution of summer precipitation in the Yangtze River Basin was analyzed. As was shown in the results, the distribution of summer precipitation in the middle and lower reaches of Yangtze River was mainly composed of four types: northern type (2005 and 2007), southern type (2001 and 2003), intermediate type (2000, 2004 and 2006) and integral type (2002). According to the correlation analysis of summer precipitation and atmospheric circulation in East Asia, the precipitation in the Yangtze River Basin and high-low level circulation anomalies were significantly related. In other words,with the increase of the meridional degree of circulation at mid-high latitudes in the middle and upper troposphere as well as anomaly by south of subtropical high at low latitudes,the center or ridge line remained steady in the south of 30° N,thus the precipitation in the Yangtze River Basin was obviously on the high side. The study could provide better guidance for the diagnosis and forecasting of precipitation in the Yangtze River Basin in the future.

Evaluation of oasis stability in the lower reaches of the Tarim River

Oasis stability in the lower reaches of the Tarim River was assessed at the landscape scale（including changes in landscape pattern and land use in the oasis） and at the regional scale（including the cold-island effect and NDVI of the oasis） based on the methods of landscape ecology,GIS and Remote Sensing（RS）.Thematic Mapping（TM） remote sensing images from 1990,2000 and 2009 were employed along with the related meteorological and hydrological data pertaining to the reclamation area of the oasis in the lower reaches of the Tarim River.The results indicated that landscape heterogeneity and oasis complexity increased between 1990 and 2000.The comprehensive index of the degree of land use,the average index of the cold-island effect,NDVI value and oasis stability all decreased.However,the change trends in the indices referred to above were opposite between 2000 and 2009,and oasis stability was enhanced to some extent.

Division of Ecosystem Sensitivity of Natural Landscape in Lower Reaches of Tarim River

By choosing aerial and satellite remote sensing images of the year 1959, 1973, 1989, 2000 and 2008 as data source, combining ground investigation, landscape in lower reaches of Tarim River was classified and landscape classification map was promoted by using GIS technique and landscape ecology theory. Finally landscape classification maps of the five years would be converted into gray scale images which would be used for overlay analysis, and based on this, landscape ecosystem sensitive zone had been identified. The result showed that the extremely sensitive zone took up 10.18% of the study area and sensitive zone occupied 17.95% of the study area. Ecological system of natural landscape in the lower reaches of Tarim River was superior to ecological system of artificial landscape in terms of resistance to wind, dust, salt and drought. Study on division of ecosystem sensitivity area of natural landscape not only provided scientific reference for the formulation of regional policies to prevent and treat ecological environmental problems, but also was beneficial for people to identify treatment focus of ecological environmental problems in different regions and propose countermeasures ameliorating regional ecological environment.