陕西大理河流域土地利用/覆被变化的水文效应

近年来,土地利用/覆被变化的水文效应研究已成为国际的前沿和重点。在大理河流域,LUCC(包括水土保持措施)对水循环和水量平衡产生了深远影响,该流域LUCC水文效应的研究势在必行。根据研究区1990年代三期土地利用数据分析了LUCC的时空变化特征,采用特征变量时间序列法及降水-径流模型对LUCC水文效应进行了研究。结果表明:流域土地利用类型以耕地和草地为主,近10年来,耕地和草地面积有所减少,而林地和建设用地面积持续增加;流域年径流和月径流演化过程均表现出明显的下降趋势;LUCC及水土保持具有减少流域年径流、汛期流量以及增加枯季流量的作用,相对于降水因素,人类活动对流域水文的作用占主导地位;在1990~2000年期间,主要由LUCC引起的年均径流减少量达2616.6×10⁴ m³,占该期间实测减水总量的62.19%。     

Estimating the spatial and temporal impacts of climate change on rainfall reliability: An example in a Mediterranean agricultural region

Rainfall is the major driver of crop growth in Mediterranean agricultural regions and its spatial and temporal distributions determine yield potential. This study uses a long term spatial archive of rainfall observations for the Eyre Peninsula (South Australia) to estimate the spatial and temporal impacts of climate change on wheat yield. The three step process involved: (1) cluster analysis and statistical comparison to spatially distinguish heterogeneous “hazardscapes” (places that represent the physical susceptibility to hazards (Khan, 2012)); (2) using historical rainfall reliabilities to estimate the probability of receiving rainfall within a range of predefined thresholds and season for each hazardscape; (3) applying 2030 and 2070 climate change projections to determine the potential future impacts on rainfall. Nine hazardscapes were spatially differentiated each having temporally different historical seasonal rainfall reliabilities. Variations over space and time mean that the impacts of climate change will be spatially explicit. Projected rainfall reductions for 2030 showed marginal impact on hazardscapes with low seasonal reliabilities, primarily in winter and spring. The 2070 projections showed that some hazardscapes were unlikely to receive past rates of rainfall thus limiting the ongoing prospects of current and perhaps the potential adoption of alternative rain-fed land uses. Reductions in rainfall for hazardscapes with higher historical rainfall reliabilities will cause negative impacts on crop development. The ability to quantify the potential spatial and temporal impacts of climate change on seasonal trends will inform land managers' climate change mitigation and adaptation pathways.     

典型岩溶农业区地下水质与土地利用变化: 以云南小江流域为例

1 Introduction Ecological environment such as water, soil, etc. are very fragile in the karst area because of the special geological background. With the fast increase of the population and rapid social and economic development in karst area, contradictio…     

Groundwater quality and land use change in a typical karst agricultural region: a case study of Xiaojiang watershed, Yunnan

Taking the typical karst agricultural region, Xiaojiang watershed in Luxi of Yunnan Province as a research unit, utilizing the groundwater quality data in 1982 and 2004, the aerial photos in 1982 and TM images in 2004, supported by the GIS, we probe into the law and the reason of its space-time change of the groundwater quality over the past 22 years in the paper. The results show: (1) There were obvious temporal and spatial changes of groundwater quality during the past 22 years. (2) Concentrations of,SO42-,NO3-,NO2-,Cl-,and the pH value, total hardness, total alkalinity increased significantly, in which NH4+,NO3-, and NO2- of groundwater exceeded the drinking water standards as a result of non-point pollution caused by the expansion of cultivated land and mass use of the fertilizer and pesticide. (3) Oppositely, Ca2+ and HCO3- showed an obvious decline trend due to forest reduction and degradation and stony desertification. Meantime, there was a dynamic relation between the groundwater quality change and the land use change.     

Incorporating spectral data into logistic regression model to classify land cover: a case study in Mt. Qomolangma (Everest) National Nature Preserve

Only few models for land-cover classification incorporated spectral data into ordinary logistic regression (OL model) in the Mt. Qomolangma (Everest) National Nature Preserve (QNNP) in China. In this study, spectral variables were incorporated into OL model and autologistic regression (AL) model to classify six main land covers. Twelve environmental variables and seven spectral variables of 10,000 stratified random sites in the QNNP were quantified and analyzed; OL model, AL model, OL model with spectral data (OLM model), and AL model with spectral data (ALM model) were estimated. The OLM and ALM models produced better estimates of regression coefficients and significantly improved model performance and overall accuracy for the grassland, sparsely vegetated land, and bare land compared with OL and AL models.     

The effects of land use on runoff and soil nutrient losses in a gully catchment of the hilly areas： implications for erosion control

1 Introduction Soiland waterlossisoneofthe worldwide environm entalissuesthreatening sustainable land use in semiarid areas.However,soiland water loss is highly variable in space and time,and its variability resultsfrom m any factorsoperating ata wide ran…     

外商直接投资技术溢出空间效应及其变化——基于中国地级市的实证研究

FDI(外商直接投资)对内资企业的技术溢出效应是国内外研究的重要话题,但相关文献多为静态研究.本文认为FDI的技术溢出存在时间效应,即FDI对内资企业的技术溢出或挤出效应,随着FDI进入东道国的时间推移而变化.利用2003-2007年中国工业企业数据库,以通信设备、计算机和其他电子设备制造业为例,对城市面板数据建立门槛回归模型,研究FDI技术溢出效应随时间变化的动态过程.结果表明,随着FDI进入东道国的时间推移,技术溢出效应的变化呈扁S曲线:初始,FDI对内资企业表现为明显的挤出效应;3～4年后,逐渐由挤出效应向溢出效应转变;随着时间的进一步推移,溢出效应减缓下降,最终表现为不明显的溢出或挤出效应.此外,对不同所有制的内资企业,FDI技术溢出效应随时间变化的动态过程不同.     

黄土丘陵小流域土地利用格局对径流与土壤养分流失的影响--土壤侵蚀控制的意义

Serious soil erosion is one of the major issues threatening sustainable land use in semiarid areas, especially in the Loess Plateau of China. Understanding the effects of land use on soil and water loss is important for sustainable land use strategy. Two sub-catchments: catchment A (CA) and catchment B (CB) with distinct land uses were selected to measure soil moisture, runoff and soil nutrient loss in Da Nangou catchment of the Loess Plateau of China. The effects of land use patterns on runoff and nutrient losses were analyzed based on soil moisture pattern by kriging and soil nutrients using multiple regression model. The results indicated that there were significant differences in runoff yield and soil nutrient losses between the two sub-catchments. With similar land uses, the CA produced an average sediment yield of 49 kg ha-1 and 22.27 kg ha-1 during two storm events.Meanwhile, there was almost no runoff in the CB with dissimilar land uses during the same events.Buffer zones should be established to re-absorb runoff and to trap sediments in catchment with similar land use structure such as the CA. Moreover, land use management strategy aiming to increase the infiltration threshold of hydrological response units could decrease the frequency of runoff occurrence on a slope and catchment scale.     

The effects of land use on runoff and soil nutrient losses in a gully catchment of the hilly areas: implications for erosion control

Serious soil erosion is one of the major issues threatening sustainable land use in semiarid areas, especially in the Loess Plateau of China. Understanding the effects of land use on soil and water loss is important for sustainable land use strategy. Two sub-catchments: catchment A (CA) and catchment B (CB) with distinct land uses were selected to measure soil moisture, runoff and soil nutrient loss in Da Nangou catchment of the Loess Plateau of China. The effects of land use patterns on runoff and nutrient losses were analyzed based on soil moisture pattern by kriging and soil nutrients using multiple regression model. The results indicated that there were significant differences in runoff yield and soil nutrient losses between the two sub-catchments. With similar land uses, the CA produced an average sediment yield of 49 kg ha-1 and 22.27 kg ha-1 during two storm events. Meanwhile, there was almost no runoff in the CB with dissimilar land uses during the same events. Buffer zones should be established to re-absorb runoff and to trap sediments in catchment with similar land use structure such as the CA. Moreover, land use management strategy aiming to increase the infiltration threshold of hydrological response units could decrease the frequency of runoff occurrence on a slope and catchment scale.