The Source of Groundwater Recharge Based on Entropy Theory in the Arid Areas of North China

Objective Any natural system is constantly exchanging material, energy and information with the environment, and all tkese processes follow the basic law of thermodynamics, with no exception of groundwater recharge and discharge process. On the basis of the principle of the first law of thermodynamics, the reverse geochemical simulation method is widely used in the study of groundwater recharge, runoff and drainage process. However, some studies only consider the material conservation in theprocess, but ignore the probability of the transformation.

LAND DEGRADATION AND ITS MANAGEMENT IN THE ARID AND SEMI ARID AREAS OF CHINA

hina is a large country with varied physical environments. Some of them are quite fragile and susceptible to land degradation, such as the arid and semiarid areas, as well as the slopeland of extensive mountain and hilly areas. Therefore, human actions play a significant role in desertification processes. It was estimated that there are 3,327,000 km 2 of desertified areas in China, in which 1,533,000 km 2 are desert, gobi and sandy desertified areas. Most of them are in arid, semiarid and dry sub humid areas in northern China. Soil salinization is another kind of land desertification. It was estimated that about one fifth of the 66,700 km 2 of farmlands have been affected by soil salinization to certain extent. Grassland degradation is also serious in China. The main problems are the reduction of bio mass, decline of preferred species and soil erosion induced by overgrazing. In Inner Mongolia the area of degraded grasslands occupies 43.8 percent of the total available area of the grasslands. The productivity of grasslands in Tibet has decreased by 20 - 50 percent [21]. Soil and water erosion is more serious in China. Based on remote sensing general survey initiated by Ministry of Water Resources in 1992, the total soil eroded area is 3,670,000 km 2, occupying 38.2 percent of the total territorial area, in which 1,790,000 km 2 is water eroded area and 1,880,000 km 2 is wind eroded area.

BASIC IDEA OF TOURIST'S ITINERARIES IN THE ARID AREA OF CHINA——Discussion of the Methodology for Designing the Itineraries in the Arid Area

The aspect discussed in the present paper should ont be identified strictly with the natu-ral and geogrophical arid areas in the whole China, but only referred to the seven provincesas Shaanxi, Gansu, Qinhai, Xinjiang and Inner Mongolia. According to the real conditions of the development of tourism which was formedobjectively in the arid areas, it is necessary to consider comprehensively the influence by

China Steps Up Anti-poverty Effort in Arid Western Areas

China＇s State Council, or the cabinet, has decided to further extend a program that involves special funds for infrastructure and other projects in three particularly add and poor areas in the country＇s remote northwest. While extending the program from 2009 to 2015, the government also decided to raise the annual total funding from 200 million yuan （29.2 million U.S. dollars） to 300 million yuan.

Spatio-temporal pattern and changes of evapotranspiration in arid Central Asia and Xinjiang of China

Accurate inversion of land surface evapotranspiration （ET） in arid areas is of great significance for understanding global eco-hydrological process and exploring the spatio-temporal variation and ecological response of water resources. It is also important in the functional evaluation of regional water cycle and water balance, as well as the rational allocation and management of water resources. This study, based on model validation analysis at varied scales in fiwe Central Asian countries and China＇s Xinjiang, developed an appropriate approach for ET inversion in arid lands. The actual ET during growing seasons of the study area was defined, and the changes in water participating in evaporation in regional water cycle were then educed. The results show the simulation error of SEBS （Surface Energy Balance System） model under cloud amount consideration was 1.34% at 30-m spatial scale, 2.75% at 1-km spatial scale and 6,37% at 4-kin spatial scale. ET inversion for 1980-2007 applying SEBS model in the study area indicates： （1） the evaporation depth （May-September） by land types descends in the order of waters （660.24 ram） 〉 cultivated land （464.66 mm） 〉 woodland （388.44 mm） 〉 urbanized land （168.16 mm） 〉 grassland （160.48 mm） 〉 unused land （83.08 mm）; and （2） ET during the 2005 growing season in Xinjiang and Central Asia was 2,168.68x108 m3 （with an evaporation/precipitation ratio of 1.05） and 9,741.03x108 m3 （with an evaporation/precipitation ratio of 1.4）, respectively. The results unveiled the spatio-temporal variation rules of ET process in arid areas, providing a reference for further research on the water cycle and water balance in similar arid regions.

IRRIGATING WARPED SOILS——ANTHROPOGENIC SOIL IN ARID AND SEMI-ARID REGIONS OF CHINA

The irrigating warped soils occur in the old irrigation areas of arid and semi-arid re-gions of China, and distributed from Zhangjiakou of Hebei province, through InnerMongolia Autonomous Region, Ningxia Hui Autonomous Region, Gansu province,Qinhai Province, down to Xinjiang Autonomous Region, including the arid subalpine rivervalleys in the western part of Tibet.

Toxic metal enrichment characteristics and sources of arid urban surface soil in Yinchuan City, China

To investigate the environmental quality of the urban surface soil in Yinchuan City, the capital of Ningxia Hui Autonomous Region （Ningxia）, China, we sampled surface soil and measured the concentrations of 8 toxic metals （Pb, Cr, Cu, Zn, Co, Bi, Ni and V） using X-ray fluorescence spectrometry. The enrichment characteristics and sources of these toxic metals in the soil were analyzed by the enrichment factor （EF） and multivariate statistical analysis. The results showed that the mean concentrations of these toxic metals in the soil samples were 25.0, 109.1, 16.8, 26.0, 37.2, 2.7, 25.3 and 59.9 mg/kg for Pb, Cr, Cu, Zn, Co, Bi, Ni and V, respectively, which were 1.2, 1.8, 0.8, 0.4, 3.2, 8.7, 0.7 and 0.8 times of the corresponding background values of Ningxia soil, respectively. The variations of Pb, Zn, Co, Bi and Ni concentrations in the surface soil of Yinchuan were larger than those of the other metals. Our results also showed that the toxic metals investigated in the soil had different enrichment levels. Both Co and Bi were significantly enriched, whereas Cr was only moderately enriched in the soil. There was a deficiency or minimal enrichment of the other toxic metals in the soil. Source analysis results based on the concentration, enrichment characteristics and multivariate statistical analysis indicated that Cr, V and Ni originated from a combination of fossil fuel combustion, traffic pollution and natural occurrence. Pb, Cu and Zn were predominantly derived from natural and traffic sources, while Co and Bi primarily originated from construction sources.

Revisit of event-based rainfall characteristics at Shapotou area in northern China

Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosystem dynamics in these regions. Rainfall event timing and magnitude are important drivers of ecosystem processes and are instrumental in creating land-scape heterogeneity in arid and semi-arid regions. Rainfall event characteristics were analyzed using an automatic tip-ping-bucket rain-gauge record across the entire summer monsoon season from 2008 to 2015 at the arid desert area of Shapotou in the Tengger Desert, China. Changing the minimum inter-event time （MIT） from 30 min to 24 h alters the number of rainfall events from 64 to 25 for the event depth larger than 0.1 mm. The mean rainfall intensity declined from 0.95 mm/h to 0.53 mm/h, and the geometric mean event duration rose from 0.55 h to 4.4 h. The number of rainfall events, mean rainfall intensity, and geometric mean event duration differed under different criteria of individual rainfall depths, except that for an individual rainfall depth of 0.5, 1.0, and 5.0 mm. The aforementioned features differed only at the lowest range of the mean rainfall intensity and depth for MIT=3 and 6 h. These findings suggest that identification of event-based rainfall in this specific arid region can be better achieved by setting the MIT at six hours. The wide variation in rainfall event properties indicate the need for paying more attention to the proper selection and reporting of event criteria in studies that adopt event-based data analysis. This is especially true in quantifying effective rainfall for soil water replenishment in terms of rainfall depth and intensity with infrequent rainfall events.

基于生境及其植被特征的西北干旱半干旱区城市绿地生态设计途径

【目的】在地域自然资源的约束及可持续城市绿地建设的现实诉求下,探索能够指导西北干旱半干旱区城市绿地生态设计实践的方法策略,为该地区建立人工干预下的新城市生态过程提供支持。【方法】分别从中、小尺度对城市生境的异质性特征进行认知,并对其与城市绿地设计层级、内容的匹配性关系进行分析。【结果】构建出中小尺度城市绿地生态设计框架,并针对西北干旱半干旱区城市绿地建设,划分出4种典型城市绿地生态设计类型及其生态设计分区,提出相应的场地生境多样性优化设计、植物群落多样性设计和科普展示系统设计策略。【结论】将中、小尺度城市生境及其植被特征的形成与维持机制转化为城市绿地生态设计途径,可为西北干旱半干旱区城市绿地生态建设提供理论支持和技术指导。

加气对西北旱区膜下滴灌棉花光合及水分利用效率的影响

为探明西北旱区滴灌棉花适宜的加气灌溉模式,试验以不加气灌溉为对照(CK),设置5个加气灌溉处理:苗期加气(AS)、蕾期加气(AB)、花铃期加气(AF)、蕾期加气+花铃期加气(ABF)、苗期加气+蕾期加气+花铃期加气(AW);研究了不同生育期加气灌溉对西北旱区棉花光合作用及水分利用效率的影响.结果表明,与CK相比,所有加气处理的光合特性及地上部生物量都显著提高,其中处理AW较CK的净光合速率显著增加22.68%,蒸腾速率显著增加41.19%,气孔导度显著增加33.42%,胞间CO 2浓度显著降低16.22%;花铃期加气灌溉使西北旱区棉花地上部茎、叶、蕾/铃干物质累积量分别显著增加29.26%,11.15%和33.41%.不同生育期加气灌溉下,棉花光合特性、地上部生物量以及产量最优的处理为AW和AF,且差异不具有统计学意义;但是处理AF的水分利用效率最高,为1.51 kg/m 3,显著高于处理AW.因此,从高效节水增产的角度考虑,在棉花花铃期进行加气(AF)可作为西北旱区膜下滴灌棉花的最佳加气灌溉模式.

我国西北干燥区地面气象站观测环境代表性思考

气候观测环境代表性和观测资料质量是开展大尺度气候变化监测和研究的前提。为了解我国干燥区气象观测环境变化和台站代表性,对河西走廊和北疆9个国家级气象站观测环境开展了调研。结合先前研究结果,从气候变化监测和研究的视角,提出了针对西北干燥区地面观测站代表性问题的几点思考。目前我国西北地区气象站地面观测,对于干燥区的城市和绿洲区域气候及其变化,具有较高的代表性,但对更广大的荒漠和半荒漠背景气候及其变化,代表性仍显不足。早期研究中指出的北疆等地区城镇站地面气温序列负向城市化影响,应与观测场周围局地甚至区域尺度绿洲扩大有直接联系,较难反映绿洲以外干燥区地带性气温变化。针对地面观测环境调研发现的问题及其思考,提出几点建议,希望对未来国家基准气候站网设计和建设提供一定参考。

西北干旱荒漠地区退耕还林还草工程综合效益评价

为对西北干旱荒漠地区新一轮退耕还林还草工程的实施提供科学指导,以吐鲁番市为研究区域,建立包含表征该区域特点的15个指标的综合效益评价指标体系,基于云模型与变异系数法组合确定指标权重,运用比重法无量纲化指标数据,采用加成综合法进行退耕工程综合效益评价分析,并通过灰色系统预测模型GM(1,1)对2021—2025年生态效益、经济效益、社会效益和政策响应指数进行了预测。结果表明:(1)在2004—2019年,综合效益指数逐年提高,新一轮退耕提升幅度是前一轮的两倍。(2)森林覆盖率提高、水土流失治理面积扩大、农民人均纯收入增加和人均林业产值增加,是生态效益和经济效益提高的主要因素。(3)退耕工程的实施促使产业结构和就业结构呈良性发展趋势。退耕所涉农户再退耕意愿的提升巩固了退耕成果,使其具有长效性。(4) 2021—2025年的生态效益、经济效益、社会效益和政策响应指数预测值均呈上升趋势,且经济效益指数>政策响应指数>生态效益指数>社会效益指数。依据预测结果,西北干旱荒漠地区在新一轮退耕工程的实施中应以生态建设为重点,加强生态补偿和乡村振兴战略的有效衔接,促进农业转移人口市民化,实现生态、经济、社会和政策响应间的协调发展。

干旱地区“代表性人口格网数据集”精度研究——以甘宁青地区为例

高精度的人口格网数据集在风险评价、灾害应急、生态环境保护、区域发展与规划等领域具有重要价值。输入数据精度和模型选择的不同导致其具有不同的特点与优势,因此评价代表性数据集的精度,分析数据集的适用条件意义重大。研究评估了世界人口(WorldPop)数据集和世界第四版网格化人口(GPWv4)数据集在中国西北干旱地区甘肃省、宁夏回族自治区和青海省的精度;以中国人口普查数据的最佳可用单位(乡镇行政区划)为研究单元,将WorldPop和GPWv4数据集与2020年第七次人口普查数据进行相关性分析,计算统计误差和相对误差的空间分布,定量地评价各个数据集的精度;通过目视估计定性地分析数据集的映射性能,最后讨论了数据集的误差来源。统计误差结果表明:WorldPop数据集的精度更高,其相关系数(r)、均方根误(RMSE)、平均绝对误差(MAE)和平均绝对百分比误差(MAPE)分别达到0.76、23016、0.73和0.60,而GPWv4数据集的上述统计结果分别为0.70、22297、0.75和0.58。同时,由相对误差的空间分布可知,WorldPop数据集准确估计的区域更多。目视估计结果表明:2种人口格网数据集的映射性能类似,都具有东部人口稠密、西部人口稀疏的特点。针对干旱地区人口格网数据集精度的评价研究,有利于分析数据集的误差来源,指导数据集的合理使用。在未来研究中,使用人类生活的辅助数据,生成干旱地区特有的人口分布模式,从而提高西北干旱区域人口数据集的精度。

我国干旱半干旱区气候变化特征及其对干湿波动的影响

气候干湿状况是表征区域气候特征的重要指标,是在全球气候变暖背景下,水循环与陆面蒸散发作用的综合结果。本文从湿润度指数入手,结合降水与潜在蒸散的时空变化,分析了我国干旱半干旱区气候特点与干湿变化特征及对土壤湿度的影响。分析发现:近50年来,我国干旱与半干旱区均呈变湿趋势。干旱区与半干旱区潜在蒸散与降水月差值在年内出现时间上存在不一致,且干旱区明显大于半干旱区;3~9月为干旱气候区潜在蒸散与降水差值大值期,3~6月半干旱区潜在蒸散明显大于降水,7月起差值明显减小。作用分析表明,在干旱区,降水对湿润度指数的影响更大,而对于半干旱区,降水与潜在蒸散作用相当。长期以来,我国整个干旱与半干旱区大部分土壤湿度在逐渐变干,尤其是农业耕作层的浅层土壤,几乎全区域一致呈现变干趋势,说明我国干旱半干旱区农牧业生产存在较大的潜在干旱风险。

内蒙古罕山华北落叶松径向生长特征及水热环境响应

[目的]以内蒙古罕山保护区为例,系统探讨我国北方半干旱区华北落叶松树干径向生长的变化规律及与环境因素(温度、降水等)的关系,为进一步认识半干旱区树木生长对气候变化的响应提供理论基础。[方法]在通辽市扎鲁特旗罕山国家级自然保护区,运用点触式树木径向生长测量仪对4株样树的径向生长开展了高分辨率的连续监测,并同步监测温度、降雨、土壤水分等环境因子,分析树木径向生长动态特征及影响因素。[结果]研究表明:华北落叶松径向生长具有白天收缩、夜间膨胀的日变化特征。在5—6月的树干收缩膨胀现象较7—9月更明显,且夜间膨胀量大于日间收缩量;在整个生长季尺度,华北落叶松的径向生长始终受到土壤温度的显著影响,但在不同生长阶段,土壤含水量是影响树干径向生长的重要因子。在极端丰水年(2021年)的生长季中的降雨高峰期之前(5月初—6月中),径向生长已达全年生长量的45%以上,说明土壤水分对径向生长的影响更直接,夏季降水量的直接影响较小,而冬季积雪在春季融化后的土壤水分供应则是决定径向生长的关键因子。[结论]在内蒙古半干旱地区,当年降水量对华北落叶松径向生长的直接贡献相对较小,主要是通过转化成土壤水的形式间接影响树木生长;土壤温度和土壤水分是影响径向生长的重要因子,在土壤水分未得到降雨有效补充的生长季初期,树木径向生长主要依靠土壤水的前期存量。

A data envelopment analysis of agricultural technical efficiency of Northwest Arid Areas in China

Severe resource shortage and waste of resource in agricultural production make it necessary to assess efficiency to increase productivity with high efficiency and ensure sustainable agricultural development. This paper adopted an input-oriented data envelopment analysis(DEA) method with the assumption of variable returns to scale to evaluate agricultural production efficiency of 100 major irrigation districts in Northwest China in 2010.Major findings of this paper were as follows: firstly, the average value of total technical efficiency, pure technical efficiency and scale efficiency of those irrigation districts in Northwest China were 0.770, 0.825 and 0.931,respectively; secondly, 30% of irrigation districts were technically efficient, while 42% and 32% of them showed pure technical and scale efficiency respectively. Among inefficient decision-making units, total technical efficiency score varied from 0.313 to 0.966, showing significant geographical differences, but geographical differences of pure technical efficiency was more consistent with that of total technical efficiency; thirdly, input redundancy was evident. Inputs of agricultural population, irrigation area,green water, blue water, consumption of fertilizer and agricultural machinery could be reduced by 34.88%,40.19%, 43.85%, 47.10%, 41.53% and 42.21% respectively without reducing agricultural outputs. Furthermore,irrigation area, green water and blue water had relatively high slack movement though Northwest China which is short of water resources. Based on these results, this paper drew the following conclusions: First, there is huge potential for Northwest China to improve its agricultural production efficiency, and agro-technology not input scale had greater influence on improvement. Second, farmers needed proper guidance in order to reduce agricultural inputs and it is time to centralize agricultural management for overall agricultural inputs regulation and control.

Responses of desertification to variations in wind activity over the past five decades in arid and semiarid areas in China

There have been significant variations in wind activity over the past five decades in arid and semiarid areas in China.High wind activity occurred from the 1960s to the 1970s,but wind activity has de-creased continuously from the 1980s to the present;as a result,the potential sand transport during the latter period was only 20%-50% of the values during the 1960s and 1970s.Phases of high wind activ-ity were highly consistent with the trends in desertification over the past five decades in arid and semiarid areas in China,but spring precipitation was also a significant factor:rapid desertification during the 1960s and 1970s was due to high wind activity,generally combining with low spring pre-cipitation;subsequent rehabilitation since the 1980s has resulted from the combined effects of low wind activity and higher spring precipitation.Therefore,although modern desertification and rehabili-tation processes are being more or less affected by human activities,both processes appear to be more strongly controlled by climate change.

中国西部干旱区生态环境演变过程

根据湖沼沉积、黄土沉积和冰积等地质记录,运用地理信息系统、遥感、生态景观学等方法,从万年、千年和百年及百年以下四个时间尺度对中国西部干旱区生态环境演变过程进行研究。结果表明,全新世以来,中国西部干旱区的气候变化经历了多次的相对暖干和相对冷湿交替变化,变化历程较为复杂。早全新世、中全新世、晚全新世气候特点因地因时而异,但总体特征以干旱化为主,280～350a来,降水量有明显的减少趋势,并表现出显著的周期性。但在近半个世纪以来,中国天山地区的气候变化特征表现为气温升高,降水量增加。总的来说,从20世纪80年代以来,新疆的气候趋于好转,植被覆盖状况改善明显,山地森林、草甸、人工绿洲的面积均呈增加趋势。研究结果还表明,在一定尺度的气候背景条件下,地表的植被覆盖对调节绿洲区域气候有着积极的作用,可增加局部地区的降水。

中国干旱半干旱区潜在植被演替

研究中国干旱半干旱区植被背景,成为其生态环境建设方面的基础性和指导性的工作。潜在植被作为一种与所处立地达到平衡的演替终态,反映的是无人类干扰的情况下,立地所能发育形成的最稳定成熟的一种顶极植被类型,是一个地区现状植被的发展趋势,对本地区植被生态的恢复和重建具有重要的指导意义。以综合顺序分类法为基本理论方法,在GIS研究方法支持下,采用中国干旱半干旱区119个气象观测站1961—2005年的年降水数据与115个气象观测站1961—2005的>0℃年积温数据,以15a的年平均数据为时间周期,对中国干旱半干旱区潜在植被的演替进行了分析,得出了以下结论:在中国干旱半干旱区,潜在植被类型之间发生了复杂的演替过程。1961—1975年间,分布在中国干旱半干旱区的潜在植被有10种类型,由于气候变化,到20世纪90年代后期仅剩6种类型。在潜在植被类型之间的转化特征与数量方面,表现出3种特点,稳定减少、稳定增加与波动性变化。在潜在植被类型地理分布格局变化与发展方向方面,演替明显的地区主要有:吐鲁番盆地、锡林郭勒高原北部、呼伦贝尔高原、太平岭地区;在发展方向上,潜在植被的空间变化方向(演替方向)均异。潜在植被类型演替的驱动因素主要是气候变化条件下,影响植被分布的水热条件发生了改变。

西北地区沙丘凝结水形成机制及对生态环境影响初步探讨

西北地区沙漠及荒漠化地区,包气带的水分来源除来自大气降水外,还来自凝结水,凝结水对包气带中水分的保存、运移及荒漠植被生态起到至关重要的作用。作者在甘肃省河西走廊高台县西的流动沙漠边缘的半固定沙丘上,采用TSCⅡ智能化土壤水分快速测试仪,SN2202数字温度计、CENTER1300相对湿度仪进行了凝结水观测试验。对沙丘表层0～30cm范围内的气温、地表温度、地温和含水量进行连续观测,每2h观测一次,试验历时5d。试验结果表明,在西北沙漠、荒漠化地区有凝结水存在,它的形成不仅对包气带中水分的保存及分布起着重要的作用,并且对维系荒漠化地区的植被生态系统的稳定至关重要。并对凝结水形成机制进行了初步探索;初步确定,日气候变化造成的地表温度与地温温差是凝结水形成的主控因素,包气带中的含水量分布则控制着凝结水的多寡,凝结水主要出现在干沙层与湿润砂层界面上。