Surface Regional Heat(Cool) Island Effect and Its Diurnal Differences in Arid and Semiarid Resource-based Urban Agglomerations

With the rapid development of urban agglomerations in northwest arid and semiarid regions of China, the scope of the urban heat island(UHI) effect has gradually expanded and gradually connected, and has formed a regional heat island(RHI) with a larger range of impact to the regional environment. However, there are few studies on the heat island effect of urban agglomerations in arid and semiarid regions, so this paper selects the urban agglomeration of Hohhot, Baotou and Ordos(HBO) of Inner Mongolia, China as the study area. Based on the 8-day composite Moderate-resolution Imaging Spectroradiometer(MODIS) surface temperature data(156scenes in all) and land use maps for 2005, 2010, and 2015, we analyze the spatiotemporal distributions of regional heat(cool) islands(RH(C)I) and the responses of surface temperatures to land-use changes in the diurnal and interannual surface cities. The results showed that: 1) from 2005 to 2015, urban areas showed the cold island effect during the day, with the area of the cold island showing a shrinking feature;at night, they showed the heat island effect, with the area of the heat island showing a first decrease and then an increase.2) From 2005 to 2015, the land development(unutilized land to building land) brings the greatest temperature increase(ΔT = 1.36°C)during the day, while the greatest temperature change at night corresponds to the conversion of cultivated land to building land(ΔT =0.78°C) exhibited the largest changes at night. From 2010 to 2015, the land development(grassland to building land) bring the greatest temperature increase(ΔT = 0.85°C) during the day, while the great temperature change at night corresponds to the conversion of water areas to building land(ΔT = 1.38°C) exhibited the largest changes at night. Exploring the spatial and temporal evolution of surface urban heat(cool) islands in urban agglomerations in arid and semiarid regions will help to understand the urbanization characteristics of urban agglomerations and provide a reference for the formulation of policies for the coordinated and healthy development of the region and co-governance of regional environmental problems.

An overview of the spatial patterns of land surface processes over arid and semiarid regions

With data from the project Collaborative Observation of Semi-arid/Arid Regions in North China, collected during July and September 2008, the spatial patterns of land surface processes over arid and semiarid regions have been investigated based on the ordinary Kriging interpolation approach. Generally, for the radiation processes, downward and upward short-wave radiation have a uniformly increasing trend with latitude, but the spatial patterns of long-wave radiation present notable regional differences: both upward and downward long-wave radiation increase with latitude in the west of North China, while in the east they vary inversely with latitude, suggesting surface temperature and clouds respectively have feedbacks to the long-wave radiation in the west and east of North China. The surface net radiation basically has a negative latitudinal trend. Long-wave radiation budget plays an important role in the spatial pattern of surface net radiation, particularly in the east of North China, although short-wave radiation budget largely determines the magnitude of surface net radiation. For the energy processes, latent and sensible heat flux varies conversely with latitude: more available land surface energy is consumed by evaporating soil water at lower latitudes while more is used for heating the atmosphere at higher latitudes. A soil heat flux maximum and minimum are found in Loess Plateau and Qinghai Plateau respectively, and a maximum is seen in the northeast China.

Impacts of Climate Change on Net Primary Productivity in Arid and Semiarid Regions of China

In recent years, with the constant change in the global climate, the effect of climate factors on net primary productivity(NPP) has become a hot research topic. However, two opposing views have been presented in this research area: global NPP increases with global warming, and global NPP decreases with global warming. The main reasons for these two opposite results are the tremendous differences among seasonal and annual climate variables, and the growth of plants in accordance with these climate variables. Therefore, it will fail to fully clarify the relation between vegetation growth and climate changes by research that relies solely on annual data. With seasonal climate variables, we may clarify the relation between vegetation growth and climate changes more accurately. Our research examined the arid and semiarid areas in China(ASAC), which account for one quarter of the total area of China. The ecological environment of these areas is fragile and easily affected by human activities. We analyzed the influence of climate changes, especially the changes in seasonal climate variables, on NPP, with Climatic Research Unit(CRU) climatic data and Moderate Resolution Imaging Spectroradiometer(MODIS) satellite remote data, for the years 2000–2010. The results indicate that: for annual climatic data, the percentage of the ASAC in which NPP is positively correlated with temperature is 66.11%, and 91.47% of the ASAC demonstrates a positive correlation between NPP and precipitation. Precipitation is more positively correlated with NPP than temperature in the ASAC. For seasonal climatic data, the correlation between NPP and spring temperature shows significant regional differences. Positive correlation areas are concentrated in the eastern portion of the ASAC, while the western section of the ASAC generally shows a negative correlation. However, in summer, most areas in the ASAC show a negative correlation between NPP and temperature. In autumn, precipitation is less important in the west, as opposed to the east, in which it is critically important. Temperatures in winter are a limiting factor for NPP throughout the region. The findings of this research not only underline the importance of seasonal climate variables for vegetation growth, but also suggest that the effects of seasonal climate variables on NPP should be explored further in related research in the future.

Spatio-temporal Variations of Temperature and Precipitation During 1951–2019 in Arid and Semiarid Region, China

Understanding the spatio-temporal variations of temperature and precipitation in the arid and semiarid region of China(ASRC)is of great significance for promoting regional eco-environmental protection and policy-making.In this study,the annual and seasonal spatio-temporal patterns of change in average temperature and precipitation and their influencing factors in the ASRC were analyzed using the Mann-Kendall test,linear tendency estimation,accumulative anomaly and the Pearson’s correlation coefficient.The results showed that both annual average temperature and average annual precipitation increased in the ASRC during 1951–2019.The temperature rose by about 1.93℃and precipitation increased by about 24 mm.The seasonal average temperature presented a significant increase trend,and the seasonal precipitation was conspicuous ascension in spring and winter.The spatio-temporal patterns of change in temperature and precipitation differed,with the southwest area showing the most obvious variation in each season.Abrupt changes in annual and seasonal average temperature and precipitation occurred mainly around the 1990 s and after 2000,respectively.Atmospheric circulation had an important effect on the trends and abrupt changes in temperature and precipitation.The East Asian summer monsoon had the largest impact on the trend of average annual temperature,as well as on the abrupt changes of annual average temperature and precipitation.Temperature and precipitation changes in the ASRC were influenced by long-term and short-term as well as direct and indirect anthropogenic and natural factors.This study identifies the characteristics of spatio-temporal variations in temperature and precipitation in the ASRC and provides a scientific reference for the formulation of climate change responses.

干旱区土壤无机碳碳汇作用及其对固碳减排贡献研究进展

【研究目的】干旱区土壤无机碳作为全球碳循环举足轻重的组成部分,其碳汇效应不容忽视。【研究方法】本文查阅了大量国内外干旱区土壤无机碳的相关文献,重点对土壤无机碳汇确认、碳库组成、来源识别,以及碳汇影响因素进行了系统性归纳总结。【研究结果】干旱区无机碳汇效应伴随着干旱区负通量研究得到确认,但其碳库组成十分复杂,包括了液相碳库与固相碳库。其中液相储库主要以可溶性碳酸盐形式赋存于干旱区地下水体;固相储库则为以固相碳酸盐矿物的形式赋存在土壤中,依据不同成因来源分为成岩碳酸盐与成土碳酸盐,后者又细分为碳质成土碳酸盐与硅质成土碳酸盐。成土碳酸盐中的硅质成土碳酸盐具备真正长期稳定的碳汇效应。无机碳汇的影响因素复杂,包括了自然的气候、土壤性质与深度、生物作用、成土母质、土壤有机质等因素,以及土地利用与土地覆盖、农业管理措施等人为因素。【结论】干旱区土壤无机碳对全球碳循环研究极其重要,当前研究主要聚焦在土壤无机碳来源分辨,碳汇效应强度确认与固碳潜力量化,以及影响因素明确与人为干预的可能性评估等方面。在实现“双碳目标”驱动下,查清干旱—半干旱地区土壤无机碳源汇过程与影响因素必将是未来的研究热点,也是解决“碳失汇”科学难题的突破点,极大地推动全球碳循环研究。

Aeolian dust transportation and deposition by near-surface winds in arid and semiarid China

Dustfall collections were carried out in April and May 2001 and in March 2002 at six sites in northern China.Our results showed that the total deposition of dust fractions 【250 μm in diameter and the deposition of Fe both decreased exponentially with increasing distances from the source areas,and that the half-attenuation distance (HAD) for dust deposition was about 229 km in this re-gion.The HAD was closely related to the grain-size distribution of the dust,and the 15 to 20 μm fractions had the longest HAD.However,the fractions 【15 μm in diameter can be easily adsorbed to coarse particles and deposited after only short distances,and the HAD for the fractions 15 to 100 μm in diameter showed a power relationship with the grain-size distribution.The HAD for Fe deposition was 233 km,which was a little longer than that of total dust deposition,which suggests that the Fe content is higher in fine particles than in coarse particles,as previous studies have suggested.In addition,our analysis showed that under the control of current climatic conditions,the coarse fractions in dust derived from northwestern China cannot be transported over long distances,instead,it is transported primarily by near-surface winds (【3 km above the ground).The Fe in aeolian dust generated from arid and semiarid regions of China and deposited in the North Pacific region is usually transported by the upper westerlies.

全球干旱/半干旱区年代尺度干湿变化研究的进展及思考

干旱/半干旱区气候变化研究一直是广泛关注的前沿科学问题,尤其是气候干湿变化规律及未来的发展趋势。过去大量的研究揭示了全球不同干旱/半干旱区的干湿变化事实和机理,取得了一系列重要进展,IPCC第6次评估报告明确指出未来全球干旱化将加剧,但也存在诸多问题没有得到一致的认识。本文将对全球变暖背景下有关干旱/半干旱区年代尺度干湿变化,特别是年代尺度干旱研究进行梳理,系统评述当前相关研究的现状并提出干旱/半干旱区研究所面临的关键科学问题。

A Case Study of the Impacts of Dust Aerosols on Surface Atmospheric Variables and Energy Budgets in a Semi-Arid Region of China

The authors present a case study investigating the impacts of dust aerosols on surface atmospheric variables and energy budgets in a semi-arid region of China. Enhanced observational meteorological data, radiative fluxes, near-surface heat fluxes, and concentrations of dust aerosols were collected from Tongyu station, one of the reference sites of the International Coordinated Energy and Water Cycle Observations Project (CEOP), during a typical dust storm event in June 2006. A comprehensive analysis of these data show that in this semi-arid area, higher wind velocities and a continuously reduced air pressure were identified during the dust storm period. Dust storm events are usually associated with low relative humidity weather conditions, which result in low latent heat flux values. Dust aerosols suspended in the air decrease the net radiation, mainly by reducing the direct solar radiation reaching the land surface. This reduction in net radiation results in a decrease in soil temperatures at a depth of 2 cm. The combination of increased air temperature and decreased soil temperature strengthens the energy exchange of the atmosphere-earth system, increasing the surface sensible heat flux. After the dust storm event, the atmosphere was dominated by higher pressures and was relatively wet and cold. Net radiation and latent heat flux show an evident increase, while the surface sensible heat flux shows a clear decrease.

西北干旱半干旱区NDVI季节性变化及其影响因素

研究植被的动态变化及其影响因素,不仅能够揭示植被覆盖动态变化特征与气候变化之间的响应机制,同时对区域的植被恢复以及生态可持续具有重要意义。本文基于MODIS遥感卫星数据,借助变异系数、趋势分析、相关分析与Hurst指数探究了2000—2020年西北干旱半干旱区植被覆盖逐季变化特征、影响因素及未来趋势。结果表明:(1)归一化植被指数(Normalized DifferenceVegetationIndex,NDVI)空间变异程度在冬季偏高,且高波动主要分布在新疆与内蒙古大兴安岭的草地与未利用地区域。(2)NDVI随季节波动较大,在林地与耕地最为明显。(3)NDVI主要为改善趋势,其中,春季改善面积最大(84.63%),冬季最小(72.52%),且林地改善最为显著。(4)各季度NDVI均受地表温度与降水量影响(Significance=0.05),且夏季地表温度与冬季降水量逐年递增对植被生长具有抑制作用。(5)未来NDVI主要呈改善趋势。值得注意的是,退化区域零星分布于新疆塔里木盆地、准噶尔盆地等地区。本研究旨在为西北干旱半干旱区的生态修复与治理,以及局部气候暖湿化的应对提供理论参考。

Urban expansion and intra-urban land evolution as well as their natural environmental constraints in arid/semiarid regions of China from 2000–2018

Rapid urbanization has occurred in arid/semiarid China,threatening the sustainability of fragile dryland ecosystems;however,our knowledge of natural environmental constraints on multiscale urban lands in this region is still lacking.To solve this issue,this study retrieved 15-m multiscale urban lands.Results indicated that urban area increased by 68%during 2000–2018,and one-third of the increase was contributed by only three large cities.The coverage of impervious surface area(ISA) and vegetated area(VA) increased by 16.6%and 1.38%,respectively.Such land-cover change may be helpful in suppressing wind erosion and sand storms.We also found that the newly urban lands had relatively lower ISA and higher VA than the old urban lands,indicating an improved human settlement environment.Strong environmental constraints on urban expansion were identified,with cities in oasis urban environments(OUEs) that had water supply expanding 150% faster than cities in desert urban environments(DUEs).Urban development was also constrained by terrain,with 73% of the ISA expansion occurring in relatively flat areas.Overall,the aggregated pattern of urbanization and the increase in ISA and VA in the newly urbanized lands have improved water-use efficiency and ecological services and benefited desert ecosystem protection in arid/semiarid China.

半干旱雨养区小麦叶片光合生理生态特征及其对环境的响应

分析了黄土高原半干旱雨养农业区田间春小麦叶片光合生理生态特征及其对环境因子的响应。结果表明,天气晴朗时,净光合速率日变化呈典型的双峰曲线,有“午休”现象,上午明显高于下午,且不同生育期峰值出现的迟早不同。蒸腾速率日变化呈不明显的双峰型,其出现最大值的时间晚于净光合速率出现最大值的时间。在生长季节,叶片净光合速率、蒸腾速率和气孔导度均受到多个环境因子的共同影响。不同时期,起主导作用的环境因子不同,且同一个因子对几个生理指标的影响程度和强度都有差异,其中,光合有效辐射是对蒸腾速率影响最强烈的环境因子,湿度对光合作用的影响大于温度。受环境因子制约最为显著的生理指标是叶片的蒸腾速率和气孔导度。

中国北方半干旱和半湿润地区沙漠化的成因

通过对我国北方半干旱和半湿润地区沙质荒漠化的综合分析后认为，第四纪期间不同时间尺度沙漠化的成因是有差异的。1万年前的更新世期间，人类对生态环境的破坏作用甚微，沙漠化的出现和逆转主要受地球轨道要素制约的万年以上时间尺度的全球气候变化控制；1万年来的全新世特别是近2000年的历史时期，人类对生态环境的作用已越来越大，但沙漠化仍然主要受制于千年和百年尺度的气候波动；20世纪以来的现代时期，沙漠化过程既受数十年或数年的干湿气候波动作用，也受到人类不合理的经济活动的影响，但后者是主要的。

半干旱区流域土壤养分分布特征及其与地形、植被的关系

以小流域为单元,以典型横断面为代表,初步分析了黄土高原半干旱区中连川小流域坡顶、坡面和坡脚不同部位土壤养分分布特征及其与地形和植被的关系。结果表明,中连川流域土壤养分全量和速效态都匮乏。在开垦利用条件下,0～20cm土层土壤有机碳、氮、磷、Olsen-P、硝态氮含量在不同坡位的高低顺序:坡面<坡顶<坡脚,显示了土壤养分坡脚富集、坡面和坡顶流失的特征。恢复地表植被后,土壤有机碳、氮的含量较相邻的农田显著提高。草本植被群落对土壤养分(0～20cm)的积累促进作用高于灌木。

干旱半干旱地区土壤微生物结皮的生态学意义及若干研究进展

土壤微生物结皮广泛存在于干旱半干旱地区 ,且具有重要的生态学意义。文章对微生物结皮的形成、发育过程的特点 ,以及它对微生境的影响 ,包括对土壤理化性质、风蚀水蚀的抗性、土壤水分时空分布特点、养分及微量元素地球生物化学循环等土壤学过程和对植被的影响与作用等方面的国内外研究进展进行了综述 ,并对一些有争议研究结论进行了分析 ;

沙坡头地区多年降水分布特征、趋势及其变率

应用Mann -Kendall秩统计法和回归分析法 ,检验时间序列上的年降水趋势 ;应用一阶自相关分析法 ,对沙坡头地区多年降水持续性特征进行统计分析。结果表明 ,5a滑动平均曲线所对应区间 196 7— 1972年以及1977— 1982年降水量大于多年平均值 ,而 1983— 2 0 0 0年降水量滑动平均值低于多年平均值的趋势明显。 195 5—1970年的分析时段内 ,降水量每连续递减两年后 ,将稍有回升 ,但总体上趋于下降。从滑动平均计算值来看 ,年降水分布存在时间序列上的非随机因素潜在振荡 ,5a滑动平均值突出了以年为时序单位的降水振荡模式。干旱时段的延长通常在多雨年之前或之后发生 ,尤其在 1978年经历高峰降水以后 ,直至 1985年 ,区内干旱时段的延长颇为显著。

干旱半干旱地区土壤矿物组成特征及其环境意义

对处于干旱、半干旱地区的甘肃省15个地点的灰钙土、栗钙土、黑垆土、灰褐土和黄绵土等不同类型土壤剖面进行了机械组成分析、矿物组成显微鉴定和粘土矿物X射线衍射分析．结果表明:土壤机械组成以粉砂为主,粘粒次之;栗钙土、灰钙土、黑钙土和灰褐土等干旱地区典型土壤中表层的粘粒质量分数相对较低,土壤原生矿物组成以石英为主,绿帘石等蚀变矿物质量分数较高,次生矿物含有较高的石膏和方解石等;粘土矿物主要为伊利石、绿泥石、高岭石和蒙脱石．土壤机械组成、矿物组成和粘土矿物组成表明:干旱、半干旱地区土壤为黄土母质,土壤形成条件为碱性环境、较弱的淋滤作用和干冷气候,近代强烈的风蚀作用(或沙尘暴)和大气污染对土壤有一定程度的改造．

半干旱盐渍化地区果园土壤盐分离子相关性研究

以甘肃省秦安县兴国镇郑川村果园土壤为研究对象,利用统计分析的方法对500个土样盐分离子含量的相关性进行了研究。结果表明:该研究区土壤阴离子主要是HCO3-、SO42-,阳离子主要是Na+。CO32-与HCO3-、Mg2+之间存在着显著的负相关,与Na+之间存在着极显著的正相关;HCO3-与Cl-之间存在着极显著的负相关,与Mg2+之间存在着极显著的正相关;Cl-与SO42-、Ca2+、Mg2+、Na+之间存在着显著的正相关,其中与Ca2+、Na+之间存在着极显著的正相关;SO42-与Ca2+、Mg2+、Na+之间存在着极显著的正相关;Ca2+与K+之间存在着极显著的正相关,与Na+之间存在着显著的负相关;Mg2+与K+之间存在着显著的负相关;K+与Na+之间存在着极显著的负相关。通过对盐分离子的聚类分析发现,Cl-、Mg2+、CO32-、Ca2+、K+和HCO3-在该区土壤中有着相似或相近的运移特征。对相关分析和偏相关分析这两种分析方法所得结果进行了对比分析,它们之间存在着明显的差异,偏相关分析能进一步消除由于其他变量的影响,因而能够更加准确地刻化多元变量其中的两个变量之间的相关性。

辽西半干旱区小麦、玉米水肥耦合效应研究

采用 3 12 D最优饱和设计和二次通用旋转组合设计 ,通过 8年连续试验 ,对辽西半干旱区影响农业生产的水、肥因素的耦合作用进行了田间试验 .讨论分析了N、P、水及其耦合作用对作物产量的影响 .施N、施P、灌水和覆盖秸秆的合理匹配能够明显提高作物产量 ,否则 ,不仅增加成本 ,而且由于加重作物的水分或养分胁迫 ,造成减产 .根据试验结果进行了生产要素的产量效益分析 ,提出了该地区小麦、玉米生产的水肥最佳经济配比 :小麦为生育期供水 12 0 .2mm ,N 5 8.5kg·hm-2 ,P2 O512 3 .0kg·hm-2 ;玉米为生育期灌水 173 .3mm ,N 2 5 6.5kg·hm-2 ,P2 O585 .5kg·hm-2 ,覆秸秆 85 0 9.5kg·hm-2 .

辽西半干旱区秋后覆膜保墒对翌年春玉米生长发育的影响

针对辽西半干旱地区春旱严重、降雨资源年内分布不均的气候特点,在秋收后、霜冻之前进行灭茬覆膜处理,试验对旱地雨水资源跨时间调节。翌年春季土壤含水量、玉米生长状况及产量的试验结果表明,秋覆膜处理的耕层土壤含水量比未覆膜处理高出60%,播种15d后玉米出苗率达到85%,抽穗期玉米株高比未覆膜处理高33cm、径粗增加0.42cm,秋收时玉米穗重比未覆膜处理提高了49.62%。研究表明,春墒秋保、跨时间调控农田水分状况是北方干旱半干旱地区有效的农业节水措施。

旱作条件下披碱草属植物叶的生理生化特征分析

在无控制的野外旱作条件下,比较了披碱草属6种野生植物在内蒙古干旱与半干旱区生理生化特性,并对同一地区引种的不同种及分布于不同地区的同一种植物进行了对比分析。结果表明,材料XJE1和XJP5能够保持较好的水分状况,具有较高的相对含水量,而GSD4保水能力不及其他几种材料;BJT3和XJP5叶绿素含量较高,而GSD4叶绿素含量较低。渗透调节物质Pro以BJT3、XJP5和GSS2显著高于其他材料,而MDA含量以BJT3相对较高,比XJE1高近3倍;保护酶SOD活性以材料GSD4较高,其次为BJT3,GSS2较低,POD活性以XJP5较高,其次为BJT3,NMN6较低。经隶属函数综合分析发现,披碱草属6种植物中,除GSD4和NMN6之间隶属函数值差异不显著外,其他材料之间都比较显著,其隶属度值由大到小的顺序为XJP5>BJT3>XJE1>GSD4>NMN6>GSS2。并且来自同一地区的披碱草属2种不同植物的生理特征表现一定的趋同,而来自不同地区的同一种植物表现出一定适应性分化。这些结果都表明,植物为了适应不同的生态环境,各种生理生化指标都会进行相应的调节,共同起作用来保护植物免受伤害。