Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary...Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary to establish an eco-compensation mechanism for them. As the compensation standard is one of key issues in establishing eeo-compensation mechanism, this paper calculated the standard based on the farmers' willingness to accept (WTA) and the input-output analysis of eco-compensation. We took the traditional rice-fish eco-agriculture as the research object, conducting field surveys in Hani Terrace of Honghe County. Through the questionnaires in 2o11, we obtained the farmers' willingness to accept government compensation and market compensation. Then, the research evaluated the output of eco-compensation, the economic value of rice-fish paddy ecosystem services. Finally, under different market compensation standards, we compared the input and output of government compensation. The results show that, in 2011 the government should to pay farmers 7462 yuan.ha^-1·a^-1 to meet their willingness, but the output (ecological benefit) was only 7393 yuan.ha^-1·a^-1. However, whenthe rice price increases 1 yuan·kg-1 because of the limited use of chemicals in the next year, the government just has to pay farmers 4062 yuan.ha^-1·a^-1 and the surplus will be 3331 yuan.ha^-1·a^-1.展开更多
The ecology system of Hani Terraced Paddy Fields is the typical repre-sentative of the ecological agriculture in the southwestern mountainous areas of our country. After long-term development, Hani ecology system has ...The ecology system of Hani Terraced Paddy Fields is the typical repre-sentative of the ecological agriculture in the southwestern mountainous areas of our country. After long-term development, Hani ecology system has developed, cored by"forest-vil age-terrace-river", including paddy cultivation system, forests and ecologi-cal maintenance, folk culture and construction of water facilities. This research ex-plored the details of the structure and functions of the ecology system of Hani ter-raced fields. And il ustrates that the system is a new model of agriculture ecological civilization and deserves further study and more applications.展开更多
The objective evaluation to the terrace cultural landscape heritage value can provide targeted scientific basis for continuation of terrace culture landscape and establishment of protection measures. On the basis of f...The objective evaluation to the terrace cultural landscape heritage value can provide targeted scientific basis for continuation of terrace culture landscape and establishment of protection measures. On the basis of field investigation, expert consultation and literature review, combined with the AVC (Attraction、Vitality and Ca-pacity)theory and Analytic Hierarchy Process based on Fuzzy Comprehensive Evalu-ation, the terrace cultural landscape heritage protection evaluation system and eval-uation model, which selects 22 indicators from three levels including terrace culture landscape resources attraction, resources vitality and resources bearing capacity were structured. Based on col ection of data, material from field survey of China's most representative Yunnan Yuanyang Hani terrace, Hunan Ziquejie terrace and Longsheng Longji terrace and relevant mathematical calculation to determine evalua-tion index weights, organical y combined of qualitative with quantitative analysis, the diversity, reasonableness and accuracy of evaluation system is improved. Compre-hensive result of mathematical statistics showed that the rank of the cultural land-scape heritage value with the three most representative terraces in southern China is: γ(Hani)〉γ(Longji)〉γ(Ziquejie).展开更多
Having outlined evolution and tour value of Dragon Back Terraces in Longsheng County,Guilin,the author puts forward following proposals for tour development in policy-making:(1) With improving the villages of the Mino...Having outlined evolution and tour value of Dragon Back Terraces in Longsheng County,Guilin,the author puts forward following proposals for tour development in policy-making:(1) With improving the villages of the Minority community,to set up ecological museums in which the cultures of Minority are preserved,the primitive local "live humanity heritages" are shown as the key display on the basis of typical agricultural complex ecological system;(2) To encourage the citizens of the community to participate in the tour industry development,including the participation both in the decision-making in tour planning and preservation of the terrace agricultural civilization heritages as well as the allocation of the income of the local tour industry;(3)To promote the mutual development of both folkways and sightseeing tour,to enhance the exploitation of the present natural scenic and historical landscapes through the making full advantages of the present tour market.The Dragon Back Terraces are characterized by the important tour values,including the rich and colorful natural landscapes,typical complex agricultural ecological system,and the combination of the Minority folkways and agricultural civilization.展开更多
De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau.There are different views about the defarming method,and also various...De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau.There are different views about the defarming method,and also various de-farming patterns have been put into practice.This paper takes the Yangou Watershed in Shaanxi Province of China as a case for studying the comprehensive benefits of transforming slope farmland to terraces.Based on the day-by-day meteorological data of the Yan'an station in 2005 and the data of terrain features,soil and land use data of the Yangou Watershed,the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software WIN-YIELD.Furthermore,an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou Watershed.The results show that:(1) The bigger the topographic gradient is,the more remarkable benefits it has in yield increase and water-soil conservation.(2) Farmland with slope below 5° could be retained,but farmland with slope above 15° should be converted to forest or grassland as soon as possible.(3) Transforming slope farmland to terraces has the same remarkable effects as the current policy of "Relieving and de-farming" in improving agricultural production conditions,safeguarding food security,raising permanent vegetation coverage rate,and preventing soil and water loss.Besides,it is more cost-effective than the policy of "Relieving and de-farming".It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay.展开更多
The Yalong River is an important river that runs across the abruptly changing terrain of the SE Tibetan Plateau. The terraces and Quaternary sediments in its valleys preserve the information of tectonic uplift, climat...The Yalong River is an important river that runs across the abruptly changing terrain of the SE Tibetan Plateau. The terraces and Quaternary sediments in its valleys preserve the information of tectonic uplift, climate changes, and landform evolution since the Middle Pleistocene. Based on geomorphological, sedimentological, and chronological investigations, 6-8 terraces are identified in the lower reaches of Yalong catchment and its tributary--the Anning River. The electron spin resonance (ESR) or optically stimulated luminescence (OSL) data on the alluvial sediments in the upper portion of terraces indicate that they formed in 1.10, 0.90, 0.72, 0.06-0.04, 0.03-0.02, and 0.01 Ma. Tectonic uplift and the climatic cycle controlled the formation of the Yalong River terraces. The former dominated the dissection depths and incision rates, whereas the latter controlled the transformation between accumulation, which developed during the glacial period, and incision, which developed during the glacial-interglacial transition. The Yalong downstream incised rapidly from 1.10 to 0.72 Ma and rapidly from 0.06 Ma until the present; the terraces developed during these two periods. The incision rates in space during the two periods indicate the uplifting extent of the Jinpingshan area, which decreases toward the east and the south. The results reveal two rapidly uplifting stages in the SE Tibetan Plateau, including an accelerated uplifting since 0.06 Ma. Since the Middle Pleistocene, the tectonic uplift of the SE and NE parts of the Tibetan Plateau is synchronous, according to the same development stages of the river terraces of the Yalong downstream and the Yellow River in the Lanzhou area of the NE Tibetan Plateau. The difference in the horizontal displacement between the Xianshuihe Fault and the Anninghe Fault bend resulted in the rapid uplift of the Jinpingshan area. The incision rate for the spatial distribution of the Yalong downstream is the geomorphologicai response of crustal shortening and uplift differences in the SE margin block of the Tibetan Plateau. The southeastward diffusion process of the Tibetan Plateau was recorded.展开更多
Based on the study of magnetostratigraphy,magnetic susceptibility and grain size of Garze A section on the southeastern margin of the Qinghai-Tibetan Plateau since the late early-Pleistocene,the basal age of Garze loe...Based on the study of magnetostratigraphy,magnetic susceptibility and grain size of Garze A section on the southeastern margin of the Qinghai-Tibetan Plateau since the late early-Pleistocene,the basal age of Garze loess is located at~1.16 MaBP and a series of abrupt paleoclimatic changes is detected.The times of abrupt changes are of distinct series features,and the interval between each two adjacent abrupt changes is~50 kyr or~100 kyr.The most significant abrupt changes occur at around 1.06,0.85,0.6,0.46,0.39 and 0.14 MaBP.There is a chronological link between the abrupt changes of paleoclimate and the formation of river terraces and it is almost simultaneous with a strengthening trend of neotectonic activities.Therefore,maybe the climatic transition controll the timing of terrace formation,and the tectonic uplift originate potential energy and has a direct effect on channel incision, both the climatic transition and the tectonic uplift are important.Terraces are the products of the interaction of instable climatic variations and tectonic uplift.Like the loess-paleosol sequences,river terrace sequences are also controlled by the climate-tectonic coupling system and are ruled by climate-tectonic gyration with a~100 kyr paracycle,which may be the short eccentricity period of the earth.展开更多
Many agricultural landscapes have been formed through the interaction and co-evolution of nature and people, and represent the living landscapes shaped over time through intensive and continuous human cultivation. Ter...Many agricultural landscapes have been formed through the interaction and co-evolution of nature and people, and represent the living landscapes shaped over time through intensive and continuous human cultivation. Terraced paddy fields are being re-evaluated to take into account the multiple functions they fill beyond only rice cultivation, particularly their contribution to the national biodiversity strategy of Japan. Since the 1990 s, terraced paddy fields have been considered a representative cultural landscape of Japan and, at the same time, multi-stakeholder conservation activities have been conducted throughout Japan to reverse the increasing abandonment of terraces. Shiroyone Senmaida is an outstanding cultural landscape and a major tourist attraction in Noto Peninsula, Ishikawa Prefecture, which was designated through an initiative by the Food and Agriculture Organization(FAO) as a Globally Important Agricultural Heritage Systems(GIAHS) pilot site in 2011. It is important to clarify tourist preference for terraced paddy field landscapes to contribute to future policy making toward improved agricultural landscape conservation. A key finding of this study is that tourists visiting toenjoy the agricultural landscape are also concerned on the sustainability of the farming methods and preferred to maintain the naturalness of the landscape. Respondents with higher educational levels and greater concern for the biological and traditional farming knowledge aspects of the rice terraces were also more inclined to favor sustainable farming practices. Tourists preferred to maintain the naturalness and rurality of the agricultural landscape, and indicated that construction of excessive tourist facilities would cause the landscape to deteriorate. It was suggested that the local community and surroundings, including rural settlements, hills, and forests, should also be conserved together with the scenic terrace.展开更多
The Huang Shui River, a main tributary of the Yellow River, crosses a series of tectonically subsided and uplifted areas that show different patterns of terrace formation. The distribution of fluvial terrace of the Hu...The Huang Shui River, a main tributary of the Yellow River, crosses a series of tectonically subsided and uplifted areas that show different patterns of terrace formation. The distribution of fluvial terrace of the Huang Shui River is studied through topographic and sedimentologic terrace mapping. Three terraces in the Haiyan Basin, four terraces in the Huangyuan Basin, 19 terraces in the Xi'ning Basin (the four high terraces may belong to another river), nine terraces in the Ping'an Basin, five terraces in the Ledu Basin and 12 terraces in the Minhe Basin are recognized. Sedimentology research shows that the geomorphologic and sedimentological pattern of the Huang Shui River, which is located at the margin of Tibet, are different from that of the rivers at other regions. The formation process of the terrace is more complicated at the Huang Shui catchment: both accumulation terrace and erosion terrace were formed in each basin and accumulation terraces were developed in some basins when erosion terraces were formed in other basins, indicating fluvial aggradation may occur in some basins simultaneously with river incision in other basins. A conceptual model of the formation process of these two kinds of fluvial terraces at Huang Shui catchment is brought forward in this paper. First, the equilibrium state of the river is broken because of climatic change and/or tectonic movement, and the river incises in all basins in the whole catchment until reaching a new equilibrium state. Then, the downstream basin subsides quickly and the equilibrium state is broken again, and the river incises at upstream basins while the river accumulates at the subsidence basin quickly until approaching a new equilibrium state again. Finally, the river incises in the whole catchment because of climatic change and/or tectonic movement and the accumulation terrace is formed at the subsidence basin while the erosion terrace is formed at other basins. The existence of the accumulation terrace implied the tectonic subsidence in the sub-basins in Huang Shui catchment. These tectonic subsidence movements gradually developed from the downstream Minhe Basin to the upstream Huangyuan Basin. Dating the terrace sequence has potential to uncover the relationship between the subsidence in the catchment and the regional tectonic at the northeastern Tibetan Plateau.展开更多
Soil organic matter (SOM) content is one of the most important indicators of the sustainability of soil. To maintain sustainable soil utilization and management in fragile Hani terraced field, it is meaningful to in...Soil organic matter (SOM) content is one of the most important indicators of the sustainability of soil. To maintain sustainable soil utilization and management in fragile Hani terraced field, it is meaningful to investigate the effects of topography and land use type on SOM content. Descriptive statistics and geostatistics were used to analyze the data and the kriging method was applied to map the spatial patterns of SOM content. The results showed that the mean SOM content was 32.76 g/kg, with a variation coefficient of 40%. The SOM content was affected by elevation and land use type. As the increase of elevation, the SOM content in Hani terraced field also increased obviously. The SOM content in tea garden, which is almost at high elevation, was the highest in all six land use types, and the SOM content decreased in a following sequence: tea garden 〉 paddy field 〉 corn field 〉 banana garden 〉 cassava field 〉 sugarcane field. In addition, at the same elevation, the paddy field had the highest SOM content compared with other land use types. All these results demonstrate that paddy field is the most efficient and suitable land use type for SOM conservation at high, middle or low elevations in the fragile Hani terraced field. In order to protect soil quality and maintain the sustainable agricultural development, it is necessary to maintain or even to enlarge the area of paddy field in Yuanyang county, Yunnan Province, China.展开更多
Soil nutrient concentrations in the top soils from two paddy terraces were determined in order to investigate spatial distributions of soil nutrients along the elevations on the Yunnan plateau of China during the fall...Soil nutrient concentrations in the top soils from two paddy terraces were determined in order to investigate spatial distributions of soil nutrients along the elevations on the Yunnan plateau of China during the fallow period.Results showed that soil nutrients in both terraces were higher than the reference concentrations except for SOC,TN,TP and Fe.Soil macronutrients didn't show significant differences in both terraces except for Mg and Ca,so did soil micronutrients except for Mn.Spatial distribution patterns of soil nutrients along the increasing elevations were different in both terraces.However,soil nutrients in both terraces were generally not significantly influenced by the elevations and soil pH values.The findings of this study can contribute to soil fertility management and ecological protection of Hani terraces.展开更多
The eolian deposits distributed in the river valleys in the eastern margin of the Tibetan Plateau (TP) are very useful in neotectonic and paleoclimatic studies. Firstly, the climate in the eastern margin of the TP i...The eolian deposits distributed in the river valleys in the eastern margin of the Tibetan Plateau (TP) are very useful in neotectonic and paleoclimatic studies. Firstly, the climate in the eastern margin of the TP is mainly controlled by the Indian summer monsoon, and detailed studies on the loess-paleosol sequences in this region can provide valuable terrestrial evidence of past changes in the Indian summer monsoon. Secondly, the river terraces in the eastern margin of the TP are considered to be a sensitive recorder of neotectonism to reflect the timing and amplitude of the TP uplift.展开更多
On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang...On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace (i.e., the T3 terrace) tread is 38 - 39 m above fiver level, and the top of the gravels is generally covered by 3 - 10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the early- middle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modem Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang River .展开更多
Based on field landscape investigations, thermoluminescence (TL), magnetostratigraphy and Ioess-paleosol sequence, we found that there are at least four Yellow River terraces, whose ages are 0.86 Ma, 0.62 Ma, 0.13 M...Based on field landscape investigations, thermoluminescence (TL), magnetostratigraphy and Ioess-paleosol sequence, we found that there are at least four Yellow River terraces, whose ages are 0.86 Ma, 0.62 Ma, 0.13 Ma and 0.05 Ma, in Yuxi Fault-Uplift (from Sanmen Gorge to Mengjin) and at least three Yellow River terraces, whose ages are 1.24 Ma, 0.25 Ma and 0.05 Ma, in Huabei Fault Depression (from Mengjin to Kouma). All the terraces have a similar structure that several meters of paleosols directly develop on the top of fluvial silt. It shows that the Yellow River incised and consequently abandoned floodplain converted to terrace during the interglacial period. Therefore, there may be a link between the formation of terraces and glacial-interglacial climatic cycles. However, the differences in the Yellow River terrace sequences and ages between Yuxi Fault-Uplift and Huabei Fault Depression indicate that the surface uplift should play an important role in the formation of these terraces.展开更多
Soil-erosion-induced land degradation is a great challenge in the Ethiopian highlands. Consequently, the government has invested in soil and water conservation measures to tackle the problem where farmland terracing i...Soil-erosion-induced land degradation is a great challenge in the Ethiopian highlands. Consequently, the government has invested in soil and water conservation measures to tackle the problem where farmland terracing is one of the commonly implemented measures in the country. The purpose of this study was to analyze the role of farmland terracing in maintaining soil fertility and to evaluate its performance within a terrace, across terrace age and slope of terrain. The study was conducted in the Lake Maybar watershed in Wello, northern Ethiopia. Composite topsoil samples were collected from plots representing four slope categories across the terrain and three positions within a terrace. The samples were analyzed for selected soil physico-chemical properties and statistically tested using ANOVA (analysis of variance). The study revealed that soil pH (△pH [H2O] = 0.6), exchangeable K+ (△K+ = 0.33 cmol(+)/kg) and clay (9%) content significantly increased towards the lower terrain position. Unlike other studies, all soil properties except bulk density (△ 0.40 g/cm3) showed non-significant differences within a terrace. Bench terrace formation reduced soil fertility gradients within a terrace for which it has been commented. Soil fertility also showed very slight change across terrace age, which indicates terracing reduced erosion-induced soil and nutrient loss. However, in order to optimize impact of farmland terracing on soil fertility maintenance, terracing should be complemented by fertility amendment considering site-specific conditions.展开更多
The Hani Rice Terraces System, based on gravity-flow irrigation, is one of the Globally Important Agricultural Heritage Systems(GIAHS) pilot sites selected by FAO in 2010. The water resource plays an important role in...The Hani Rice Terraces System, based on gravity-flow irrigation, is one of the Globally Important Agricultural Heritage Systems(GIAHS) pilot sites selected by FAO in 2010. The water resource plays an important role in the sustainable development of this system. The value of water conserved by the forest is influenced by natural, economic and social factors. In this paper, the water quality, per capita water resources, per capita GDP and population density are chosen as indices to construct an index system for a comprehensive evaluation of water resources value. The weights of these indices are 0.443, 0.31, 0.141 and 0.106 respectively, which are determined by the analytic hierarchy process(AHP) method. The water resources value has been assessed by the fuzzy comprehensive evaluation model. The results show that the water resources value in the Hani Rice Terraces System is 4.25 RMB/m^3. Evaluating the value of water resources in the Hani Rice Terraces System can provide a reference for ecological compensation, for raising public awareness of the importance of protecting the system, and ultimately achieving its sustainable development.展开更多
The objectives of this study were to analyze the biodiversity of the Traditional Gudeuljang Irrigated Rice Terraces in Cheongsando, South Korea's representative GIAHS(Globally Important Agricultural Heritage Syste...The objectives of this study were to analyze the biodiversity of the Traditional Gudeuljang Irrigated Rice Terraces in Cheongsando, South Korea's representative GIAHS(Globally Important Agricultural Heritage System) site, with reference to position and land-use features, and to develop a plan to promote agricultural biodiversity in the region. We confirmed approximately 54,000 m2 of Gudeuljang paddy fields by an on-site survey. Of the Traditional Gudeuljang Irrigated Rice Terraces confirmed by onsite inspection, our survey showed that approximately 24,000 m2 are currently being used as paddy fields, approximately 15,000 m2 are being used as dry fields, and approximately 14,000 m2 are fallow. In terms of other non-agricultural land use, there was grassland, including graveyards; artificial arboreal land, such as orchards, rivers and wetlands, and man-made facilities, such as roads and residences. We also confirmed that the Traditional Gudeuljang Irrigated Rice Terraces had higher plant species diversity than conventional terraced rice paddies, and there was a difference in life form characteristics between the two types. Although the superficial topsoil structure is thesame for the Traditional Gudeuljang Irrigated Rice Terraces(TGIRTs) and conventional terraced rice paddies, it is thought that the differences in the subsurface structure of the TGIRTs contribute greatly to species and habitat diversity. However, the TGIRTs in Cheongsando are facing degeneration, due to damage and reduction in agricultural activity. The main cause is the reduction in the number of farming households due to an aging population in Cheongsando. In order to address this problem, we proposed a management plan, related to fallow paddy fields in South Korea, to initiate voluntary activities in the TGIRTs.展开更多
A combined survey including infrared thermography(IRT)and field-laboratory tests were conducted to analyze the thermal responses and thermal properties of loess on a landslide-prone loess slope in the Heifangtai terra...A combined survey including infrared thermography(IRT)and field-laboratory tests were conducted to analyze the thermal responses and thermal properties of loess on a landslide-prone loess slope in the Heifangtai terrace in Northwest China aiming at preliminarily demonstrating the potential of IRT as a complementary technique to the investigation of irrigation-induced loess landslides.Multitemporal thermographic surveys corresponding to various solar radiation intensities during the afternoon were carried out on the landslide-prone loess slope.Accordingly,the spatiotemporal distribution of the thermal responses within the observed slope surface was analyzed qualitatively and quantitatively.Meanwhile,field and laboratory investigations were also performed on the thermal properties of different landslide materials.The results indicate that loess,a landslide-prone deposit that usually has a relatively high water content,exhibits different thermal properties and anomalies,including a lower surface temperature and greater thermal inertia,compared to surrounding zones without landslides.The groundwater table and corresponding seepage line could also be obtained by determining the potential boundary between the thermal response distribution of landslide scarps and that of saturated deposits in the presence of landslides.The results of these investigations are expected to provide insight for future endeavors combining infrared thermography with other efficient survey methodologies(e.g.,InSAR,which can monitor the active displacement of a loess slope)to evaluate the activity of this kind of excessive irrigation-induced loess landslide.展开更多
The Luan River is the most important water system in north-eastern Hebei Province,China and is located in the transitional zone of the Eastern Yan Mountains,North China Plain and Songliao Plain.The well-developed rive...The Luan River is the most important water system in north-eastern Hebei Province,China and is located in the transitional zone of the Eastern Yan Mountains,North China Plain and Songliao Plain.The well-developed river terraces of its tributary,the Yixun River,provide excellent information for studying neotectonics and climate change.There are seven terraces in the lower reaches of the Yixun River,numbered T7-T1.The optically stimulated luminescence dating results of 23 samples show that terraces T7-T2 formed at 111.36±5.83 ka,78.20±4.45 ka,65.29±4.15 ka,56.44±3.07 ka,40.08±2.66 ka,and 13.14±0.76 ka,respectively.A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e,MIS 3,and MIS 1.Since the Late Pleistocene,the incision rate of the Yixun River has ranged from 0.371-1.740 mm/a.During the formation of T7-T6,T5-T4,T4-T3,and T3-T2,the incision rate was low.However,in the two stages during which T6-T5 and T2-T1 formed(13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka),these rates reached 1.554 mm/a and 1.592-1.740 mm/a,respectively.At approximately 30 ka,the activity of the Langying Fault increased,leading to footwall uplift.The river gathered in the north of Langying to form the ancient Erdaowan Lake,which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits.In the Early Holocene,headward erosion in the lower reaches of the Yixun River was enhanced,which resulted in the disappearance of the lake,and incised meandering formed due to increased neotectonism.Based on the analyses of river incision and the formation of ancient lakes and incised meandering,it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.展开更多
For fully understanding the hydrological dynamics of an infinite terraced slope, the infiltration process was studied by employing the Green and Ampt infiltration model. The limit equilibrium method and the Mohr-Coulo...For fully understanding the hydrological dynamics of an infinite terraced slope, the infiltration process was studied by employing the Green and Ampt infiltration model. The limit equilibrium method and the Mohr-Coulomb failure criterion were adopted to derive a stability model for the infinite terraced slope subjected to an intense rainfall. Numerical simulation was performed for verifying its applicability. The results of numerical simulation indicate that a set of stepped wetting fronts are found during infiltration, and the infiltration of terraced slope covered by coarse-textured soils can be approximated as one-dimensional infiltration. The potential sliding surfaces from the numerical method are all parallel to the slope line, and the proposed model and framework can provide an approximate method of estimating how the infiltration affects the stability of an infinite terraced slope.展开更多
基金supported by the China National Natural Science Foundation (Grant Nos. 41201586, 41201580)Visiting Professorship for Senior International Scientists (2013T2Z0011)
文摘Traditional eco-agriculture provides many ecosystem services which are important for the local environment, especially in mountain areas. In order to encourage the farmers to engage in coo-agriculture, it is necessary to establish an eco-compensation mechanism for them. As the compensation standard is one of key issues in establishing eeo-compensation mechanism, this paper calculated the standard based on the farmers' willingness to accept (WTA) and the input-output analysis of eco-compensation. We took the traditional rice-fish eco-agriculture as the research object, conducting field surveys in Hani Terrace of Honghe County. Through the questionnaires in 2o11, we obtained the farmers' willingness to accept government compensation and market compensation. Then, the research evaluated the output of eco-compensation, the economic value of rice-fish paddy ecosystem services. Finally, under different market compensation standards, we compared the input and output of government compensation. The results show that, in 2011 the government should to pay farmers 7462 yuan.ha^-1·a^-1 to meet their willingness, but the output (ecological benefit) was only 7393 yuan.ha^-1·a^-1. However, whenthe rice price increases 1 yuan·kg-1 because of the limited use of chemicals in the next year, the government just has to pay farmers 4062 yuan.ha^-1·a^-1 and the surplus will be 3331 yuan.ha^-1·a^-1.
基金Supported by Project of Ministry of Human Resources and Social Security~~
文摘The ecology system of Hani Terraced Paddy Fields is the typical repre-sentative of the ecological agriculture in the southwestern mountainous areas of our country. After long-term development, Hani ecology system has developed, cored by"forest-vil age-terrace-river", including paddy cultivation system, forests and ecologi-cal maintenance, folk culture and construction of water facilities. This research ex-plored the details of the structure and functions of the ecology system of Hani ter-raced fields. And il ustrates that the system is a new model of agriculture ecological civilization and deserves further study and more applications.
基金Supported by Guangxi Scientific Research and Technology Development Program(14124005-2-4)Youth Tourism Expert Training Program of National Tourism Administration Operation System(TYETP201548,TYETP201445)+2 种基金Guangxi Education Department Qualification and Postgraduate Education Reform and Development Program(JGY2014077)Guangxi Superior and Characteristic Key Subject Open-end Fund(LYKF05)Guilin S&T Research and Development Program(20150110-5)~~
文摘The objective evaluation to the terrace cultural landscape heritage value can provide targeted scientific basis for continuation of terrace culture landscape and establishment of protection measures. On the basis of field investigation, expert consultation and literature review, combined with the AVC (Attraction、Vitality and Ca-pacity)theory and Analytic Hierarchy Process based on Fuzzy Comprehensive Evalu-ation, the terrace cultural landscape heritage protection evaluation system and eval-uation model, which selects 22 indicators from three levels including terrace culture landscape resources attraction, resources vitality and resources bearing capacity were structured. Based on col ection of data, material from field survey of China's most representative Yunnan Yuanyang Hani terrace, Hunan Ziquejie terrace and Longsheng Longji terrace and relevant mathematical calculation to determine evalua-tion index weights, organical y combined of qualitative with quantitative analysis, the diversity, reasonableness and accuracy of evaluation system is improved. Compre-hensive result of mathematical statistics showed that the rank of the cultural land-scape heritage value with the three most representative terraces in southern China is: γ(Hani)〉γ(Longji)〉γ(Ziquejie).
文摘Having outlined evolution and tour value of Dragon Back Terraces in Longsheng County,Guilin,the author puts forward following proposals for tour development in policy-making:(1) With improving the villages of the Minority community,to set up ecological museums in which the cultures of Minority are preserved,the primitive local "live humanity heritages" are shown as the key display on the basis of typical agricultural complex ecological system;(2) To encourage the citizens of the community to participate in the tour industry development,including the participation both in the decision-making in tour planning and preservation of the terrace agricultural civilization heritages as well as the allocation of the income of the local tour industry;(3)To promote the mutual development of both folkways and sightseeing tour,to enhance the exploitation of the present natural scenic and historical landscapes through the making full advantages of the present tour market.The Dragon Back Terraces are characterized by the important tour values,including the rich and colorful natural landscapes,typical complex agricultural ecological system,and the combination of the Minority folkways and agricultural civilization.
基金the National Natural Science Foundation of China(No.40771086)National Key Technology R&D Program of China (No.2006BAD09B10)Knowledge Innovation Project of Chinese Academy of Sciences (No.KZCX2-XB2-05-01)
文摘De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau.There are different views about the defarming method,and also various de-farming patterns have been put into practice.This paper takes the Yangou Watershed in Shaanxi Province of China as a case for studying the comprehensive benefits of transforming slope farmland to terraces.Based on the day-by-day meteorological data of the Yan'an station in 2005 and the data of terrain features,soil and land use data of the Yangou Watershed,the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software WIN-YIELD.Furthermore,an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou Watershed.The results show that:(1) The bigger the topographic gradient is,the more remarkable benefits it has in yield increase and water-soil conservation.(2) Farmland with slope below 5° could be retained,but farmland with slope above 15° should be converted to forest or grassland as soon as possible.(3) Transforming slope farmland to terraces has the same remarkable effects as the current policy of "Relieving and de-farming" in improving agricultural production conditions,safeguarding food security,raising permanent vegetation coverage rate,and preventing soil and water loss.Besides,it is more cost-effective than the policy of "Relieving and de-farming".It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay.
基金supported by the Project of China Geological Survey (grant nos.1212011120071,201211077-3 and 1212011120182)
文摘The Yalong River is an important river that runs across the abruptly changing terrain of the SE Tibetan Plateau. The terraces and Quaternary sediments in its valleys preserve the information of tectonic uplift, climate changes, and landform evolution since the Middle Pleistocene. Based on geomorphological, sedimentological, and chronological investigations, 6-8 terraces are identified in the lower reaches of Yalong catchment and its tributary--the Anning River. The electron spin resonance (ESR) or optically stimulated luminescence (OSL) data on the alluvial sediments in the upper portion of terraces indicate that they formed in 1.10, 0.90, 0.72, 0.06-0.04, 0.03-0.02, and 0.01 Ma. Tectonic uplift and the climatic cycle controlled the formation of the Yalong River terraces. The former dominated the dissection depths and incision rates, whereas the latter controlled the transformation between accumulation, which developed during the glacial period, and incision, which developed during the glacial-interglacial transition. The Yalong downstream incised rapidly from 1.10 to 0.72 Ma and rapidly from 0.06 Ma until the present; the terraces developed during these two periods. The incision rates in space during the two periods indicate the uplifting extent of the Jinpingshan area, which decreases toward the east and the south. The results reveal two rapidly uplifting stages in the SE Tibetan Plateau, including an accelerated uplifting since 0.06 Ma. Since the Middle Pleistocene, the tectonic uplift of the SE and NE parts of the Tibetan Plateau is synchronous, according to the same development stages of the river terraces of the Yalong downstream and the Yellow River in the Lanzhou area of the NE Tibetan Plateau. The difference in the horizontal displacement between the Xianshuihe Fault and the Anninghe Fault bend resulted in the rapid uplift of the Jinpingshan area. The incision rate for the spatial distribution of the Yalong downstream is the geomorphologicai response of crustal shortening and uplift differences in the SE margin block of the Tibetan Plateau. The southeastward diffusion process of the Tibetan Plateau was recorded.
基金support was provided by the National Science Foundation of China grant (40472088)
文摘Based on the study of magnetostratigraphy,magnetic susceptibility and grain size of Garze A section on the southeastern margin of the Qinghai-Tibetan Plateau since the late early-Pleistocene,the basal age of Garze loess is located at~1.16 MaBP and a series of abrupt paleoclimatic changes is detected.The times of abrupt changes are of distinct series features,and the interval between each two adjacent abrupt changes is~50 kyr or~100 kyr.The most significant abrupt changes occur at around 1.06,0.85,0.6,0.46,0.39 and 0.14 MaBP.There is a chronological link between the abrupt changes of paleoclimate and the formation of river terraces and it is almost simultaneous with a strengthening trend of neotectonic activities.Therefore,maybe the climatic transition controll the timing of terrace formation,and the tectonic uplift originate potential energy and has a direct effect on channel incision, both the climatic transition and the tectonic uplift are important.Terraces are the products of the interaction of instable climatic variations and tectonic uplift.Like the loess-paleosol sequences,river terrace sequences are also controlled by the climate-tectonic coupling system and are ruled by climate-tectonic gyration with a~100 kyr paracycle,which may be the short eccentricity period of the earth.
文摘Many agricultural landscapes have been formed through the interaction and co-evolution of nature and people, and represent the living landscapes shaped over time through intensive and continuous human cultivation. Terraced paddy fields are being re-evaluated to take into account the multiple functions they fill beyond only rice cultivation, particularly their contribution to the national biodiversity strategy of Japan. Since the 1990 s, terraced paddy fields have been considered a representative cultural landscape of Japan and, at the same time, multi-stakeholder conservation activities have been conducted throughout Japan to reverse the increasing abandonment of terraces. Shiroyone Senmaida is an outstanding cultural landscape and a major tourist attraction in Noto Peninsula, Ishikawa Prefecture, which was designated through an initiative by the Food and Agriculture Organization(FAO) as a Globally Important Agricultural Heritage Systems(GIAHS) pilot site in 2011. It is important to clarify tourist preference for terraced paddy field landscapes to contribute to future policy making toward improved agricultural landscape conservation. A key finding of this study is that tourists visiting toenjoy the agricultural landscape are also concerned on the sustainability of the farming methods and preferred to maintain the naturalness of the landscape. Respondents with higher educational levels and greater concern for the biological and traditional farming knowledge aspects of the rice terraces were also more inclined to favor sustainable farming practices. Tourists preferred to maintain the naturalness and rurality of the agricultural landscape, and indicated that construction of excessive tourist facilities would cause the landscape to deteriorate. It was suggested that the local community and surroundings, including rural settlements, hills, and forests, should also be conserved together with the scenic terrace.
基金supported by the National Natural Science Foundation of China(Grant no.40901002 and 40325007)the 985 project to Nanjing University and the CAS-KNAW PhD project(05-PhD-10)
文摘The Huang Shui River, a main tributary of the Yellow River, crosses a series of tectonically subsided and uplifted areas that show different patterns of terrace formation. The distribution of fluvial terrace of the Huang Shui River is studied through topographic and sedimentologic terrace mapping. Three terraces in the Haiyan Basin, four terraces in the Huangyuan Basin, 19 terraces in the Xi'ning Basin (the four high terraces may belong to another river), nine terraces in the Ping'an Basin, five terraces in the Ledu Basin and 12 terraces in the Minhe Basin are recognized. Sedimentology research shows that the geomorphologic and sedimentological pattern of the Huang Shui River, which is located at the margin of Tibet, are different from that of the rivers at other regions. The formation process of the terrace is more complicated at the Huang Shui catchment: both accumulation terrace and erosion terrace were formed in each basin and accumulation terraces were developed in some basins when erosion terraces were formed in other basins, indicating fluvial aggradation may occur in some basins simultaneously with river incision in other basins. A conceptual model of the formation process of these two kinds of fluvial terraces at Huang Shui catchment is brought forward in this paper. First, the equilibrium state of the river is broken because of climatic change and/or tectonic movement, and the river incises in all basins in the whole catchment until reaching a new equilibrium state. Then, the downstream basin subsides quickly and the equilibrium state is broken again, and the river incises at upstream basins while the river accumulates at the subsidence basin quickly until approaching a new equilibrium state again. Finally, the river incises in the whole catchment because of climatic change and/or tectonic movement and the accumulation terrace is formed at the subsidence basin while the erosion terrace is formed at other basins. The existence of the accumulation terrace implied the tectonic subsidence in the sub-basins in Huang Shui catchment. These tectonic subsidence movements gradually developed from the downstream Minhe Basin to the upstream Huangyuan Basin. Dating the terrace sequence has potential to uncover the relationship between the subsidence in the catchment and the regional tectonic at the northeastern Tibetan Plateau.
基金supported by the National Natural Science Foundation of China (Grant No. 70973143)Natural Science Foundation of Zhejiang Province, China (Grant No. Y5110259)
文摘Soil organic matter (SOM) content is one of the most important indicators of the sustainability of soil. To maintain sustainable soil utilization and management in fragile Hani terraced field, it is meaningful to investigate the effects of topography and land use type on SOM content. Descriptive statistics and geostatistics were used to analyze the data and the kriging method was applied to map the spatial patterns of SOM content. The results showed that the mean SOM content was 32.76 g/kg, with a variation coefficient of 40%. The SOM content was affected by elevation and land use type. As the increase of elevation, the SOM content in Hani terraced field also increased obviously. The SOM content in tea garden, which is almost at high elevation, was the highest in all six land use types, and the SOM content decreased in a following sequence: tea garden 〉 paddy field 〉 corn field 〉 banana garden 〉 cassava field 〉 sugarcane field. In addition, at the same elevation, the paddy field had the highest SOM content compared with other land use types. All these results demonstrate that paddy field is the most efficient and suitable land use type for SOM conservation at high, middle or low elevations in the fragile Hani terraced field. In order to protect soil quality and maintain the sustainable agricultural development, it is necessary to maintain or even to enlarge the area of paddy field in Yuanyang county, Yunnan Province, China.
基金supported by National Basic Research Program (Grant No.2010CB951102)National Natural Science Foundation of China (Grant No.50879005,40701003 and U0833002)+2 种基金Program for New Century Excellent Talents in UniversityProgram for Changjiang Scholars and Innovative Research Team in University (Grant no.IRT0809)the Fundamental Research Funds for the Central Universities (Grant No.2009SD-24)
文摘Soil nutrient concentrations in the top soils from two paddy terraces were determined in order to investigate spatial distributions of soil nutrients along the elevations on the Yunnan plateau of China during the fallow period.Results showed that soil nutrients in both terraces were higher than the reference concentrations except for SOC,TN,TP and Fe.Soil macronutrients didn't show significant differences in both terraces except for Mg and Ca,so did soil micronutrients except for Mn.Spatial distribution patterns of soil nutrients along the increasing elevations were different in both terraces.However,soil nutrients in both terraces were generally not significantly influenced by the elevations and soil pH values.The findings of this study can contribute to soil fertility management and ecological protection of Hani terraces.
基金supported by the National Department Public Benefit Research Foundation of China(grant No.201211077)National Natural Science Foundation of China(Grant No.40802033)
文摘The eolian deposits distributed in the river valleys in the eastern margin of the Tibetan Plateau (TP) are very useful in neotectonic and paleoclimatic studies. Firstly, the climate in the eastern margin of the TP is mainly controlled by the Indian summer monsoon, and detailed studies on the loess-paleosol sequences in this region can provide valuable terrestrial evidence of past changes in the Indian summer monsoon. Secondly, the river terraces in the eastern margin of the TP are considered to be a sensitive recorder of neotectonism to reflect the timing and amplitude of the TP uplift.
基金financially sponsored by the National Natural Science Foundation of China(Grant No.41301011,41301029,41201008)
文摘On the northern fringe of Mt. Huangshan, many fiver terraces are developed at the junction between mountains and plains. The fiver terraces are most typical in the Jingxian Basin, Anhui Province, where the Qingyijiang River, one of the longest tributaries of the lower Yangtze River, developed three staircase terraces. The topmost terrace (i.e., the T3 terrace) tread is 38 - 39 m above fiver level, and the top of the gravels is generally covered by 3 - 10.9 m of red clay deposits. Systematic magnetostratigraphy and electron spin resonance dating are used to research the timing of the establishment of the Qingyijiang River. The main results show that the topmost terrace developed no later than 900 kyr ago and that the appearance of the Qingyijiang River occurred correspondingly at least before 900 kyr ago on the northern fringe of Mt. Huangshan. In view of the almost synchronous age,the establishment of the Qingyijiang River was seemingly a response to the Mid-Pleistocene Revolution when the 100 kyr cycle commenced, and the Kunlun-Huanghe movement during the early- middle Pleistocene transition. In addition, the establishment of the Qingyijiang River possibly reflected the birth of the modem Yangtze River to some degree. Therefore the timing of the formation of the Yangtze River is restricted to no later than 900 kyr ago based on the appearance of the Qingyijiang River .
基金Science and Technology Planning Project of Yunnan Province,No.2007D199MNational Natural Science Foundation of China,No.40462002No.40161002
文摘Based on field landscape investigations, thermoluminescence (TL), magnetostratigraphy and Ioess-paleosol sequence, we found that there are at least four Yellow River terraces, whose ages are 0.86 Ma, 0.62 Ma, 0.13 Ma and 0.05 Ma, in Yuxi Fault-Uplift (from Sanmen Gorge to Mengjin) and at least three Yellow River terraces, whose ages are 1.24 Ma, 0.25 Ma and 0.05 Ma, in Huabei Fault Depression (from Mengjin to Kouma). All the terraces have a similar structure that several meters of paleosols directly develop on the top of fluvial silt. It shows that the Yellow River incised and consequently abandoned floodplain converted to terrace during the interglacial period. Therefore, there may be a link between the formation of terraces and glacial-interglacial climatic cycles. However, the differences in the Yellow River terrace sequences and ages between Yuxi Fault-Uplift and Huabei Fault Depression indicate that the surface uplift should play an important role in the formation of these terraces.
文摘Soil-erosion-induced land degradation is a great challenge in the Ethiopian highlands. Consequently, the government has invested in soil and water conservation measures to tackle the problem where farmland terracing is one of the commonly implemented measures in the country. The purpose of this study was to analyze the role of farmland terracing in maintaining soil fertility and to evaluate its performance within a terrace, across terrace age and slope of terrain. The study was conducted in the Lake Maybar watershed in Wello, northern Ethiopia. Composite topsoil samples were collected from plots representing four slope categories across the terrain and three positions within a terrace. The samples were analyzed for selected soil physico-chemical properties and statistically tested using ANOVA (analysis of variance). The study revealed that soil pH (△pH [H2O] = 0.6), exchangeable K+ (△K+ = 0.33 cmol(+)/kg) and clay (9%) content significantly increased towards the lower terrain position. Unlike other studies, all soil properties except bulk density (△ 0.40 g/cm3) showed non-significant differences within a terrace. Bench terrace formation reduced soil fertility gradients within a terrace for which it has been commented. Soil fertility also showed very slight change across terrace age, which indicates terracing reduced erosion-induced soil and nutrient loss. However, in order to optimize impact of farmland terracing on soil fertility maintenance, terracing should be complemented by fertility amendment considering site-specific conditions.
基金financially supported by the National Natural Science Fund, China (Grant Nos. 31200376, 41201586)the CAS Visiting Professor-Ship for Senior International Scientists (Grant No. 2013T2Z0011)
文摘The Hani Rice Terraces System, based on gravity-flow irrigation, is one of the Globally Important Agricultural Heritage Systems(GIAHS) pilot sites selected by FAO in 2010. The water resource plays an important role in the sustainable development of this system. The value of water conserved by the forest is influenced by natural, economic and social factors. In this paper, the water quality, per capita water resources, per capita GDP and population density are chosen as indices to construct an index system for a comprehensive evaluation of water resources value. The weights of these indices are 0.443, 0.31, 0.141 and 0.106 respectively, which are determined by the analytic hierarchy process(AHP) method. The water resources value has been assessed by the fuzzy comprehensive evaluation model. The results show that the water resources value in the Hani Rice Terraces System is 4.25 RMB/m^3. Evaluating the value of water resources in the Hani Rice Terraces System can provide a reference for ecological compensation, for raising public awareness of the importance of protecting the system, and ultimately achieving its sustainable development.
基金supported by the research program of Dongguk University
文摘The objectives of this study were to analyze the biodiversity of the Traditional Gudeuljang Irrigated Rice Terraces in Cheongsando, South Korea's representative GIAHS(Globally Important Agricultural Heritage System) site, with reference to position and land-use features, and to develop a plan to promote agricultural biodiversity in the region. We confirmed approximately 54,000 m2 of Gudeuljang paddy fields by an on-site survey. Of the Traditional Gudeuljang Irrigated Rice Terraces confirmed by onsite inspection, our survey showed that approximately 24,000 m2 are currently being used as paddy fields, approximately 15,000 m2 are being used as dry fields, and approximately 14,000 m2 are fallow. In terms of other non-agricultural land use, there was grassland, including graveyards; artificial arboreal land, such as orchards, rivers and wetlands, and man-made facilities, such as roads and residences. We also confirmed that the Traditional Gudeuljang Irrigated Rice Terraces had higher plant species diversity than conventional terraced rice paddies, and there was a difference in life form characteristics between the two types. Although the superficial topsoil structure is thesame for the Traditional Gudeuljang Irrigated Rice Terraces(TGIRTs) and conventional terraced rice paddies, it is thought that the differences in the subsurface structure of the TGIRTs contribute greatly to species and habitat diversity. However, the TGIRTs in Cheongsando are facing degeneration, due to damage and reduction in agricultural activity. The main cause is the reduction in the number of farming households due to an aging population in Cheongsando. In order to address this problem, we proposed a management plan, related to fallow paddy fields in South Korea, to initiate voluntary activities in the TGIRTs.
基金This work was supported by the National Natural Science Foundation of China(Grant No.41672348,41931286,52008246).
文摘A combined survey including infrared thermography(IRT)and field-laboratory tests were conducted to analyze the thermal responses and thermal properties of loess on a landslide-prone loess slope in the Heifangtai terrace in Northwest China aiming at preliminarily demonstrating the potential of IRT as a complementary technique to the investigation of irrigation-induced loess landslides.Multitemporal thermographic surveys corresponding to various solar radiation intensities during the afternoon were carried out on the landslide-prone loess slope.Accordingly,the spatiotemporal distribution of the thermal responses within the observed slope surface was analyzed qualitatively and quantitatively.Meanwhile,field and laboratory investigations were also performed on the thermal properties of different landslide materials.The results indicate that loess,a landslide-prone deposit that usually has a relatively high water content,exhibits different thermal properties and anomalies,including a lower surface temperature and greater thermal inertia,compared to surrounding zones without landslides.The groundwater table and corresponding seepage line could also be obtained by determining the potential boundary between the thermal response distribution of landslide scarps and that of saturated deposits in the presence of landslides.The results of these investigations are expected to provide insight for future endeavors combining infrared thermography with other efficient survey methodologies(e.g.,InSAR,which can monitor the active displacement of a loess slope)to evaluate the activity of this kind of excessive irrigation-induced loess landslide.
基金supported by the National Natural Science Foundation of China(41977258)the China Geological Survey(DD20190310,DD20221761)the National Key R&D Program of China(2018YFC1504704).
文摘The Luan River is the most important water system in north-eastern Hebei Province,China and is located in the transitional zone of the Eastern Yan Mountains,North China Plain and Songliao Plain.The well-developed river terraces of its tributary,the Yixun River,provide excellent information for studying neotectonics and climate change.There are seven terraces in the lower reaches of the Yixun River,numbered T7-T1.The optically stimulated luminescence dating results of 23 samples show that terraces T7-T2 formed at 111.36±5.83 ka,78.20±4.45 ka,65.29±4.15 ka,56.44±3.07 ka,40.08±2.66 ka,and 13.14±0.76 ka,respectively.A comparison with the oxygen isotope curves of deep-sea sediments reveals that the sediment formation of each terrace corresponded to cold periods of marine isotope stages MIS 4 and MIS 2 and the relatively cold periods of MIS 5e,MIS 3,and MIS 1.Since the Late Pleistocene,the incision rate of the Yixun River has ranged from 0.371-1.740 mm/a.During the formation of T7-T6,T5-T4,T4-T3,and T3-T2,the incision rate was low.However,in the two stages during which T6-T5 and T2-T1 formed(13.14±0.76 ka to 0.58±0.08 ka and 10.79±0.64 ka to 0.16±0.01 ka),these rates reached 1.554 mm/a and 1.592-1.740 mm/a,respectively.At approximately 30 ka,the activity of the Langying Fault increased,leading to footwall uplift.The river gathered in the north of Langying to form the ancient Erdaowan Lake,which resulted in the drying of the river in the lower reaches of the Yixun River during the last glacial maximum without forming river deposits.In the Early Holocene,headward erosion in the lower reaches of the Yixun River was enhanced,which resulted in the disappearance of the lake,and incised meandering formed due to increased neotectonism.Based on the analyses of river incision and the formation of ancient lakes and incised meandering,it was inferred that there have been three periods of strong tectonism in the river basin since the Late Pleistocene.
基金Project(51178423)supported by the National Natural Science Foundation of China
文摘For fully understanding the hydrological dynamics of an infinite terraced slope, the infiltration process was studied by employing the Green and Ampt infiltration model. The limit equilibrium method and the Mohr-Coulomb failure criterion were adopted to derive a stability model for the infinite terraced slope subjected to an intense rainfall. Numerical simulation was performed for verifying its applicability. The results of numerical simulation indicate that a set of stepped wetting fronts are found during infiltration, and the infiltration of terraced slope covered by coarse-textured soils can be approximated as one-dimensional infiltration. The potential sliding surfaces from the numerical method are all parallel to the slope line, and the proposed model and framework can provide an approximate method of estimating how the infiltration affects the stability of an infinite terraced slope.