Quantitative analysis of the dynamic change and spatial differences of the ecological security: a case study of Loess Plateau in northern Shaanxi Province

Using the theory and method of the ecological footprint, and combining the changes of regional land use, resource environment, population, society and economy, this paper calculated the ecological footprint, ecological carrying capacity and ecological surplus/loss in 1986-2002 on the Loess Plateau in northern Shaanxi Province. What is more, this paper has put forward the concept of ecological pressure index, set up ecological pressure index models, and ecological security grading systems, and the prediction models of different ecological footprints, ecological carrying capacity, ecological surplus and ecological safety change, and also has assessed the ecological footprint demands of 10,000 yuan GDE The results of this study are as follows： （1） the ecological carrying capacity in northern Shaanxi shows a decreasing trend, the difference of reducing range is the fastest; （2） the ecological footprint appears an increasing trend; （3） ecological pressure index rose to 0.91 from 0.44 during 1986-2002 on the Loess Plateau of northern Shaanxi with an increase of 47%; and （4） the ecological security in the study area is in a critical state, and the ecological oressure index has been increasing rapidlv.

Current situation and human health risk assessment of fluoride enrichment in groundwater in the Loess Plateau:A case study of Dali County,Shaanxi Province,China

This study aims to investigate the mechanisms and health risks of fluoride enrichment in groundwater in the Loess Plateau,China.By taking Dali County,Shaanxi Province,China as an example,this study obtains the following results through field investigation and the analyses of water,soil,and crop samples.(1)The groundwater can be divided into two major types,namely the Quaternary pore-fissure water and Karst water.The Karst area and sandy area have high-quality groundwater and serve as the target areas for optional water supply.The groundwater in the study area is slightly alkaline and highly saline.Meanwhile,high-fluoride groundwater is mainly distributed in the loess and river alluvial plains in the depression area of the Guanzhong Basin and the discharge areas of the groundwater,with the highest fluoride concentration exceeding seven times the national standard.(2)Fluoride in groundwater mainly originates from a natural source and human activities.The natural source refers to the fluoride-bearing minerals in rocks and soil,and the fluoride from this source is mainly controlled by natural factors such as climate,geologic setting,pH,specific hydrochemical environment,ion exchange,and mineral saturation.Human activities in modern life can be further divided into industrial and agricultural sources primarily.(3)The health risks of fluoride contamination are very high in the Loess Plateau,especially for children compared to adults.Meanwhile,the risks of fluoride exposure through food intake are higher than those through drinking water intake.The authors suggest selecting target areas to improve water supply and ensure the safety of drinking water in the study area.Besides,it is necessary to plant crops with low fluoride content or cash crops and to conduct groundwater treatment to reduce the fluoride concentration in drinking water.These results will provide a theoretical basis for safe water supply in the faulted basin areas in the Loess Plateau.

Change Characteristics and Cause Analysis of Summer Precipitation Anomaly in Loess Plateau of Northern Shaanxi Province

[ Objective] The research aimed to study change characteristics and formation cause of summer precipitation abnormality in Loess Plateau of northern Shaanxi Province. [ Method] Based on summer precipitation data at 15 observation stations in Loess Plateau of northern Shaanxi Province and NCEP/NCAR dataset from 1961 to 2008, change characteristics of summer precipitation in the region were investigated by using linear trend estimation and composite analysis. [Result] Summer rainfall had decrease trend in most parts of northem Shaanxi Province, but had increase trend in western and southern regions. The interannual and interdecadal variations were obvious. It had a large amount of precipitation from the mid- 1970s to the mid-1990s, while summer rainfall had decrease trend after the mid-1990s and increase trend in recent years. In wet years, it was a large positive anomaly zone from western Ural Mountains to northem Lake Baikal at middle and high latitudes, indicating that there was a blocking high over the Ural Mountains, while it was negative anomaly zone from northern Okhotsk Sea to Lake Baikal. From Northwest Pacific Ocean to Bo- hal Sea Bay and North China, it was a wide range of significant positive anomaly zone, which was favorable for Westem Pacific subtropical high ex- tending westward and northward. The analysis in dry years showed opposite circulation configuration. It was ＂ -, ＋, -＂ wave train distribution in middle and high latitudes and positive anomaly zone along the Sea of Okhotsk. Western Pacific subtropical high was also by south and east. Major water vapor was from southeast direction in wet years, and abundant water vapor caused more summer rainfall in northern Shaanxi. In dry years, water vapor was from westerly tuming southerly flow. It was weaker and by east. [ Conclusion] The research provided reference for reasonable utilization of summer precipitation in the zone.

Changes in Ecosystem Service Values on the Loess Plateau in Northern Shaanxi Province,China

The Loess Plateau in northern Shaanxi Province of China covers Yulin, Yan＇an, and Tongchuan cities mainly. The kind of physiognomy is complicated and various, including the transitional region of the sand and wind, the hilly-gully fragile region, the pimple mound region from North to South. Large-scale land reclamation projects that are severely affecting these ecosystems have been implemented. In this paper, we reported an investigation to the changes in land use and ecosystem services on the Loess Plateau in northern Shaanxi Province from 1978 to 2000. We used three LANDSAT TM and/or ETM data sets to estimate the changes in the size of five land-cover/land-use categories, and we also used previously published value coefficients to estimate the changes in the value of ecosystem services delivered by each land category. Finally, we ranked the contribution of various ecosystem functions to the overall value of the ecosystem services, we have estimated that the annual value of the ecosystem services is 56.95 billon RMB yuan in the Loess Plateau in northern Shaanxi Province in 2000. In the region, from 1978 to 2000, the economic value of the fixing carbon was higher, the economic value of water conservation was the lowest, but the economic value of the NPP, fixing carbon, and supplying oxygen accounted for above ninety percent of the total value, obviously the vegetation created the biggest ecosystem service value. We can conclude that future land-use policy formulation should give precedence to the conservation of these ecosystems over uncontrolled reclamation, and that further land reclamation should be based on rigorous environmental impact analyses.

Migration and speciation transformation mechanisms of mercury in undercurrent zones of the Tongguan gold mining area, Shaanxi Loess Plateau and impact on the environment

In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment,the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess,alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province,and the following results were obtained:(1)The source of Hg in subsurface flow zone is mainly caused by mineral processing activities;(2)the subsurface flow zone in the study area is in alkaline environment,and the residual state,iron and manganese oxidation state,strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment;mercury in river alluvial or diluvial strata is mainly concentrated in silt,tailings and clayey silt soil layer,and mercury has certain stability,and the form of mercury in loess is easier to transform than the other two media;(3)under the flooding condition,most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed,and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection;(4)infiltration at the flood level accelerates the migration of pollutants to the ground;(5)the soil in the undercurrent zone is overloaded and has seriously exceeded the standard.Although the groundwater monitoring results are safe this time,relevant enterprises or departments should continue to pay attention to improving the gold extraction process,especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes,and intensify efforts to solve the geological environmental problems of mines left over from history.At present,the occurrence form of mercury in the undercurrent zone is relatively stable,but the water and soil layers have been polluted.The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links.The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.

New Thought of Meteorological Forecasting and Warning Models of Geological Disasters in Loess Plateau of North Shaanxi

The study established daily comprehensive precipitation equations and calculated respective critical daily comprehensive precipitation value of loess-collapse disasters and landslide disasters by dint of the geological disasters and corresponding precipitation data in 47 years.Considering geological disaster risk divisions,precipitation influence coefficient and daily comprehensive precipitation,hourly rolling daily-forecasting and hourly warning fine and no-gap models on the base of high temporal and spatial resolution rainfall data of automatic meteorological station were developed.Through the verifying of combination of dynamical forecasting model and warning model,the results showed that it can improve efficiency of forecast and have good response at the same time.

Variation Characteristics of Sunshine Hours and Its Reason Analysis over Loess Plateau of Shaanxi

[Objective] The research aimed to study variation characteristics of sunshine hours over Loess Plateau of Shaanxi during 1961-2010.[Method] By using the climate tendency rate,climate trend coefficient and linear correlation,the temporal and spatial variation characteristics of sunshine hours in Loess Plateau of Shaanxi in recent 50 years were analyzed.Moreover,the main reason for inducing variation of sunshine hours in the zone was discussed.[Result] In recent 50 years,the variation of annual sunshine hours in Loess Plateau of Shaanxi mainly presented decrease trend.The decrease zones were mainly located in windy desert region along the Great Wall line,central loess hilly region,most areas of plateau remains region and most areas of arid plateau region in north Weihe River.The increase zones were mainly located in west and northeast plateau remains region,southwest plateau remains region,some areas of arid plateau region in north Weihe River.Seen from four-season variation trend,except in spring,the sunshine hours in other seasons presented varying decrease trends.The decrease amplitude in summer was 24.34 h/10 a,and was the most significant.The second one was-16.62 h/10 a in winter.The decrease amplitude in winter was 3.55 h/10 a,and was unobvious.Seen from spatial variation,the annual sunshine hours presented significant increase trend in Mizhi of loess hilly region and significant decrease trend in Dingbian,Shenmu of windy desert region along the Great Wall line,Qingjian,Yanchuan of plateau remains region,Longxian,Fengxiang,Chunhua and Hancheng of arid plateau region in north Weihe River.There was no obvious variation trend in other research zones.The annual and four-season sunshine hours all presented negative correlations with rainfall,relative humidity,total cloud amount,low cloud amount,water vapor pressure and fog days.The sunshine hours presented positive correlation with visibility.The correlation coefficients between sunshine hours and relative humidity,rainfall,total cloud amount,water vapor pressure,fog days and visibility were all bigger in each region.[Conclusion] The research provided basis for analyzing climate variation over Loess Plateau of Shaanxi.

Characteristics of Wind Speed Profiles under Complex Terrain Conditions in Loess Plateau

To reveal the changing characteristics of wind speed with altitude in under complex terrain conditions in Loess Plateau in Northern Shaanxi, based on the complete data of wind speed profiles of six wind towers in the region in a year, the diurnal, monthly, and seasonal variations of wind shear index of the wind towers as well as the changes of wind shear index with wind speed under complex terrain conditions were studied. The results showed that the wind shear index of each wind tower was positive, showing that wind speed tended to increase with the rising of altitude in most areas of Loess Plateau in Northern Shaanxi; terrain had obvious effects on wind speed profiles. The wind shear index of the wind towers was small during the day and large at night; the differences between day and night in the wind shear index of various wind towers were different; there were obvious seasonal variations in the wind shear index of the wind towers under different terrain conditions. With the increase of wind speed, the wind shear index of each wind tower increased firstly and then decreased, but the peaks of wind shear index of various wind towers ap- peared in different wind speed ranges. When wind speed varied from 3 to 12 m/s, wind shear index was larger than the comprehensive wind shear index of the wind towers, which is beneficial to the improvement of power generation of a wind power plant. Wind shear index can be used to assess wind resources of a wind power plant.

The Cave Dwellings in Northern Shaanxi

Cave dwellings (or Yaodong in Chinese) are a unique style of traditional houses on the Loess Plateau of westerncentral China. They exhibit rich folk customs and a flavor of the surrounding environment. The soil of the Loess Plateau is thick and compact, making it the ideal place for building caves that are sturdy enough to last hundreds or even thousands of years without collapsing. Most cave dwellings have straight walls and low arched ceilings, with the walls reinforced with grass and mud. Cave dwellings are comfortable to live in, being cool in the summer and warm in the winter. Being cut into the mountain, the architecture blends in quite well with the surrounding natural environment, while the rust exterior exhibits the beauty of ingenuity.

Quantifying the vertical distribution pattern of land-use conversion in the loess hilly region of northern Shaanxi Province 1995–2015

The mountainous and hilly region plays an important role in ecological safety and production in China. However, recent studies have poorly characterized the parallel structure of land use in the valleys of the mountainous and hilly region using topographic factors(e.g.elevation, slope, aspect). Here, the loess hilly region of northern Shaanxi Province is used as a representative case area to analyze the vertical distribution pattern of land-use conversion using the relative elevation concept and the HAND index. The differences in the vertical structure of land-use conversion between absolute elevation and relative elevation were compared. We found that the classifications of absolute and relative elevation had similar proportions of each relative elevation grade in each absolute elevation grade. Cropland,woodland, and grassland were distributed evenly in each grade of absolute/relative elevation,while water body, built-up land and unused land were more likely to spread in low grades of relative elevation than those of absolute elevation. The land-use conversion(i.e. loss of cropland and gain in woodland and built-up land) showed an apparently stepped distribution with relative elevation classification, suitable for revealing vertical distributions of land-use conversion in the loess hilly region. Cropland transformed to woodland was mainly distributed in high grade of relative elevation, decreasing with a decrease in grades, while built-up land transformed from cropland and grassland was mainly distributed in low grade of relative elevation, decreasing with increases in grades. The grade of relative elevation where cropland transformed to woodland descended with the implementation of the Grain for Green Project. Our results suggest that it is better to analyze the vertical distribution of land-use conversion with relative elevation classification in hilly regions.

陕北黄土高原景观生态质量时空分异及驱动力分析

景观生态质量是衡量生态系统稳定度的重要指标。基于景观稳定性、景观干扰度和恢复与重建力三个层面构建景观生态质量评估模型,探究了陕北黄土高原20 a来景观生态质量及时空变化,并利用地理探测器进行了驱动力分析。结果表明:陕北黄土高原景观生态质量呈现中南部高、西部及北部低的分布特征,空间相关性和异质性显著;景观生态质量等级在中等及以上的区域面积占比由40.0%上升至63.5%,景观生态质量明显改善,并呈现先下降后上升的变化趋势;区域景观生态质量受自然因子和人为因子的共同作用,NDVI和高程是主要驱动因子,且与降水、气温、GDP和人口密度等因素交互后驱动力增强。

黄土丘陵沟壑区村庄生态系统服务对人类福祉的影响机理——以陕西省米脂县为例

[目的]在生态脆弱区,探究村庄生态系统服务对人类福祉的影响机理,为推动区域可持续发展提供参考。[方法]以黄土丘陵沟壑区陕西省米脂县为例,基于生物物理指标、人类需求理论分别评估村庄服务与福祉,分析了两者的空间分布。基于结构方程模型揭示了村庄禀赋视角下村庄服务对福祉的影响机理。[结果](1)作物和肉类空间分布相近,水果供给呈集中分布;高土壤保持村庄分布于南部丘陵,水源涵养和生境质量均西部高于东部;景观美学东部高于西部,高休闲娱乐村庄集中于城镇区。(2)村庄各需求、福祉空间分布差异较大。高福祉村庄包括川道村、多数乡镇中心村、乡村振兴示范村;低福祉村庄主要位于东西部丘陵,需政府重点关注。(3)村庄服务对福祉产生正向影响,作物、肉类、水源涵养是影响村庄福祉的关键服务。村庄禀赋对服务、福祉产生正向影响,且村庄禀赋通过提高村庄ES间接改善村庄福祉水平。高程是关键的自然禀赋,非文盲率和老龄化率是关键的社会禀赋;距县城距离是关键的区位禀赋。[结论]村庄服务与福祉空间差异明显,禀赋—服务—福祉的影响路径显著。依据空间差异与路径差异施策,是提升生态系统服务福祉贡献的要求。

陇东旱塬区复种马铃薯栽培模式筛选

为研究陇东旱塬区冬油菜收获后复种马铃薯不同栽培模式对其产量及经济效益的影响,采用单因素试验区组设计,以陇薯7号原种马铃薯品种为试验材料,共设计8种栽培模式。通过对不同模式下马铃薯农艺性状、商品率、产量及经济效益的比较,筛选出最佳的冬油菜茬复种马铃薯栽培模式。结果表明,秸秆带状覆盖、平作起垄、垄沟种植3个栽培模式表现较好,667 m^(2)产量分别为2292.81、1917.63、1655.46 kg,比对照露地平作分别增产41.27%、18.15%和2.00%。

晋西黄土区不同入渗水量下刺槐林地优先流特征

为探究晋西黄土区刺槐林地是否存在土壤优先流及不同入渗水量条件下对优先流发育程度的影响,以山西吉县蔡家川小流域刺槐人工林为研究对象,结合野外染色示踪试验与室内图像处理的技术方法,获取垂直剖面染色形态特征图像并进行特征值的提取,选取基质流深度、染色面积比、优先流比、长度指数、平均最大染色深度和染色面积比变异系数6个特征指标,基于均方差决策法定量分析不同入渗水量条件下的优先流发育情况。结果表明:(1)刺槐人工林土壤水分入渗过程中存在优先流现象,随入渗水量的增加,优先路径逐步向侧向发展,优先流斜侧入渗现象明显;(2)染色面积比随土层深度的增加呈非线性减小趋势,水分呈现非均匀下渗现象;入渗水量为75mm时的优先流比达到47.11%,优先流发育程度最高;(3)3种入渗水量条件下的平均最大染色深度分别为25.33、32.20、38.87cm,与入渗水量的大小呈正相关关系,表明入渗水量的增加可以促进水分向深层运动,有利于优先路径的开启;(4)入渗水量与优先流评价指数之间呈正相关关系,优先流评价指数75 mm(0.81)>50 mm(0.39)>25 mm(0.36),入渗水量增加促使优先流发育程度更高。

陇中黄土高原不同类型土壤团聚体稳定性及抗蚀性研究

以陇中黄土高原地区黄绵土(LS)、灰钙土(CS)、红黏土(RC)和灌淤土(SS)四种典型土壤为研究对象,探讨不同土壤类型农田土壤团聚体稳定性和抗侵蚀能力。本研究采用干筛-湿筛法得到不同粒级团聚体比例,来计算水稳性团聚体平均质量直径(MWD)、几何平均直径(GMD)、颗粒分形维数(D)、团聚体破坏率(PAD)、>0.25 mm占比[M_((w>0.25))]和土壤可蚀性因子K值。结果表明,水稳性团聚体平均质量直径红黏土和灌淤土显著性大于黄绵土和灰钙土,几何平均直径红黏土>灌淤土>黄绵土>灰钙土,分别为0.41、0.30、0.23和0.21 mm,各土壤类型间差异性显著;颗粒分形维数灰钙土最大,红黏土最小,分别为2.97和2.90;湿筛对土壤团聚体的破坏率红黏土和灌淤土显著小于黄绵土,黄绵土最大;>0.25 mm水稳性团聚体占比最大的是红黏土,为45.87%,灌淤土次之,黄绵土最小,为23.53%。相关性分析结果表明,土壤团聚体稳定性各指标间的相关性良好,其中MWD与GMD、M_((w>0.25))呈极显著正相关(p<0.01),与D、K呈极显著负相关(p<0.01),与PAD呈显著负相关(p<0.05);GMD与其他土壤团聚体各项指标均表现出极显著相关性(p<0.01);土壤有机质与土壤稳定性各指标之间也呈现出极显著相关性(p<0.01)。结论表明,土壤抗蚀性红黏土灌淤土较好,黄绵土居中,灰钙土最差。研究结果可为陇中黄土高原地区不同土壤类型农田土壤抗侵蚀能力提供参考,对黄土高原土壤水土保持功能的提升及水土保持效应的持续稳定发挥具有重要意义。

陕北黄土高原气象要素对植被覆盖的空间分异影响及风险探测

陕北黄土高原地处我国西北生态环境脆弱区,近年来受退耕还林(草)影响,区域植被覆盖变化显著,与气象要素的响应关系也呈现出了复杂的空间分异性和不确定性,亟待厘清。以不同地貌分区为响应单元,探究了陕北黄土高原变绿前后(1982—1992年与2005—2015年)NDVI指数的时空演化特征,分析了植被覆盖变化与气象要素之间的分异性响应关系,并透过最优参数的地理探测器模型(OPGD)探测了气象要素变化对植被覆盖演变的交互影响及风险。研究结果表明:(1)陕北黄土高原及各地貌分区在研究期内NDVI指数均呈显著上升趋势,且阶段化分异明显;各地貌区气温和实际蒸散发量在高原变绿前后趋势变化差异明显,1982—1992年主要呈不显著增加趋势,而2005—2015年则表现为不显著减少趋势;两个时期降水量的空间异质性较为显著,其中北部地区为持续增加趋势,而南部地区则由减少逆转为增加趋势。(2)不同地貌区NDVI指数与气温和蒸散发均呈正相关,且蒸散发与NDVI的相关性强于气温;相对高原变绿前,2005—2015年NDVI指数对各气象要素的响应强度均有所增大。(3)OPGD因子检测结果显示5km空间网格是评价气候变化对陕北黄土高原植被覆盖变化影响的最佳空间尺度,各地貌分区对NDVI指数变化影响最大的气象因子依次为:气温(黄土塬)、降水(盖沙黄土丘陵)、蒸散发(黄土峁状丘陵)、降水(黄土梁状丘陵)、降水(黄土宽谷丘陵)、蒸散发(风沙丘陵)、降水(土石丘陵);交互探测表明气象因子间的交互作用对NDVI指数的空间分异具有协同增强性,但不同时期各地貌区的主导交互因子略有差异。(4)风险探测发现不同实际蒸散发量对NDVI指数的影响有显著空间差异。(5)陕北黄土高原的植被覆盖变化并不能简单归因于退耕还林(草)等生态修复措施,而应是多要素耦合驱动的结果,气象要素在其中扮演了不可忽视的作用。

人水共生理念下传统窑洞聚落景观理水智慧研究——以陕北地区为例

中国传统聚落景观营建素有将人水共生作为古人聚居选址及农耕生产的理念和举措。因此,在聚落选址之初,古人对自然山水环境的寻找、观察及借用的用心程度甚至超过聚落后期的建设过程。为了更好地保护和传承半干旱区传统窑洞聚落景观理水智慧,避免本土理水营建技术的消失与断代,以陕北黄土高原区传统窑洞聚落为研究对象,从人水共生哲学思想出发,结合DIKW层次结构模型,构建传统聚落理水智慧解析路径与方法。从聚落选址布局理水智慧、人居营建理水智慧、农耕生产理水智慧和自然生态理水智慧4个方面,开展陕北传统窑洞聚落景观理水智慧的提取与体系构建。以期为当前我国半干旱地区乡村聚落生态人居景观营建和水基础设施建设提供理论与经验借鉴。

施氮对陇中黄土高原旱作麦田N_(2)O和CO_(2)排放的影响

【目的】探究陇中黄土高原半干旱区旱作麦田土壤N_(2)O和CO_(2)排放对不同施氮量的响应,阐明旱作麦田N_(2)O和CO_(2)排放特征及其主要影响因素,以期为该地区旱作麦田温室气体减排和氮肥管理提供依据。【方法】以陇中黄土高原旱作麦田为研究对象,采用大田定位试验和室内指标测定相结合的方法,布设CK(不施肥)、LN(低量氮肥)、MN(中量氮肥)和HN(高量氮肥)共4个施氮梯度,分析不同施氮量对旱作麦田土壤硝态氮(NO_(3)^(-)-N)、铵态氮(NH_(4)^(+)-N)、有机碳(SOC)、土壤温度、含水量及土壤N_(2)O和CO_(2)排放的影响。【结果】0~10 cm土层土壤中,HN、MN、LN较CK处理,NO_(3)^(-)-N平均含量增幅为21.55%、26.06%和34.11%;NH_(4)^(+)-N平均含量增幅为21.77%、31.42%和39.20%;SOC平均含量增幅为20.43%、25.80%和35.9%。HN、MN、LN较CK处理,N_(2)O累计排放量增幅为78.63%、130.47%、217.51%;CO_(2)累计排放量增幅为5.73%、10.63%、21.75%。皮尔逊相关关系表明,不同施氮处理中,麦田0~10 cm土层土壤中NO_(3)^(-)-N、NH_(4)^(+)-N和SOC平均含量与N_(2)O、CO_(2)累计排放量呈极显著正相关关系(P<0.001),土壤温度与N_(2)O和CO_(2)累计排放量呈显著正相关关系(P<0.05),土壤含水量与N_(2)O累计排放量呈显著的负相关关系(P<0.05),与CO_(2)累计排放量相关关系不显著。【结论】施氮可以增加黄土高原旱作麦田表层土壤中NO_(3)^(-)-N、NH_(4)^(+)-N和SOC含量,进而增加了N_(2)O和CO_(2)累计排放量,是该地区麦田N_(2)O和CO_(2)排放的主要驱动因子,表层土温和土壤含水量也一定程度上影响着N_(2)O和CO_(2)的排放。

陕北黄土高原沟壑区文物遗产时空分布规律研究

揭示陕北黄土高原沟壑区文物遗产的分布特征,为该地区历史文化时空变迁研究与历史文化空间格局的凝炼提供借鉴。研究将文物遗产按照其所承载的内涵分为聚居型、人文型、防御型与近现代文物遗产四类,运用地理信息技术分析其空间分布特征,结合历史、文化、社会等时空变迁脉络研究陕北黄土高原沟壑区文物遗产的时空分布规律及其影响因素,指出河流道路的位置与走向对聚居型文物遗产的分布具有较大影响,自然山川的形势决定了人文型文物遗产的选址与布局,政治军事活动推动了防御型遗产“由点至带”的发展演变。

陕西黄土高原苹果园土壤水分分异特征

采用定点监测法,对陕西省不同区域、生长年限、立地类型以及乔矮化果园的土壤水分分异特征进行研究。结果表明:陕西苹果园由南向北土壤贮水量逐渐降低,土壤水分亏缺加重;在干旱季节,北部丘陵沟壑区果园土壤水分亏缺度高达18.5%～47.5%,黄土残塬区为7.8%～20.3%,关中平原仅有1.2%～6.3%;在生长季内,随土壤深度增加,土壤含水量变异程度减弱;北部丘陵沟壑区的变化主要发生在2.2m以上土层内,CV值达12.67%～35.32%;黄土残塬区主要在1.8m以上土层内,CV值11.72%～24.54%;关中平原主要在1.2m以上土层内,CV值13.63%～20.76%;同一区域的果园土壤剖面贮水量随果树年龄增大而下降;在北部丘陵沟壑区,坡地的土壤水分含量最高,台地次之,梯田地相对较低;在残塬沟壑区,塬地的土壤水分含量最高,川地次之,台地相对较低;同一密度矮化果园的土壤含水量高于乔化果园,但栽培密度大的矮化果园土壤贮水量低于密度小的乔化果园。