毛乌素沙地微地形对土壤凝结水分布的影响

为研究毛乌素沙地微地形对土壤凝结水分布的影响,在宁夏盐池荒漠生态系统定位观测站进行野外试验,以当地典型微地形—沙丘为研究对象,采用微渗仪称重法测量沙丘各观测点的凝结水量,同步观测各观测点的气象因子,研究凝结水在沙丘不同坡位的分布及受气象因子影响的变化规律。结果表明:雨前各坡位凝结速率和日均凝结水量均显著低于雨后(P≤0.05)。雨前各坡位的凝结速率差异不显著,平均凝结速率为0.007mm/h,阴坡和阳坡日均凝结水量均随坡位的升高而减小,且与坡位高度呈显著的线性相关关系(P≤0.05),雨前阳坡的日均凝结水量为0.073mm,多于阴坡的0.059mm,坡顶的凝结水量最少(0.041mm)。雨后阴坡的凝结速率和凝结水量随坡位的升高而增多(不包括坡顶),阳坡的凝结速率和凝结水量日均值随坡位的升高而减少,凝结水量与坡位的高度呈显著线性负相关关系(P≤0.05)。雨后阴坡的日均凝结水量为0.310mm,高于阳坡的0.259mm,坡顶的日均凝结水量最少(0.151mm)。雨后,随着时间的推移,各坡位的日凝结水量先增多后减少,第3日凝结水量最多,此后凝结水量逐渐减少,直至趋于稳定。研究结果可为毛乌素沙地的土壤水分平衡和水资源评价提供理论依据,并为该地区的生态恢复提供重要理论支撑。     

库布齐沙漠不同发育类型人工结皮对露水凝结作用的比较研究

露水的形成是干旱、半干旱地区生态系统中重要的环境因子.以库布齐沙漠不同发育类型的人工结皮为研究对象,通过每天野外跟踪观测人工结皮的露水凝结量,比较人工结皮露水凝结量的大小及其凝结能力的差异性.试验以人工蓝藻结皮(ACC)、人工藻结皮(AAC)、人工苔藓结皮(AMC)以及自然苔藓结皮(NMC)和流沙(SS)为材料,并以绒布-平板露水测定法(CPM)为参照,试验时间为42 d.结果表明,CPM法测定的日平均露水凝结量为0.02～0.35 mm,ACC露水凝结量为0.012～0.191 min,AAC为0.032～0.230 mm,AMC为0.048~0.274 mm,NMC为0.056～0.304 mm,SS为0.003～0.083 mm.露水凝结量随结皮的发育状况而存在显著差异,露水凝结量大小依次为NMC>AMC>AAC>ACC>SS.结果还发现.人工结皮的形成明显促进了荒漠地表对露水的吸收和保持,结皮能够比沙表面凝结更多的露水,且结皮的露水千化过程比沙表面更慢.推测结皮藻丝体的发育及其胞外分泌物是结皮凝结较多露水的重要原因,同时依赖于结皮表面的微气候环境.本研究揭示了露水在维系结皮生存中的生态学意义,表明人工结皮具有较好的水土保持功能,同时有利于更好地理解生物结皮对露水的凝结机制与吸收利用情况,并为荒漠化地区有限水源条件下人工结皮利用露水等非降雨型水分进行野外生存提供重要的理论支持和试验依据.     

1989—2019年库布齐沙漠植被覆盖度的时空变化

[目的]探究库布齐沙漠近1989—2019年植被覆盖度的时空动态变化规律,为库布齐沙漠植被恢复及生态建设提供理论参考和基础数据。[方法]以1989—2019年每5 a为1期(共7期)的Landsat影像为数据源,结合归一化植被指数(NDVI)像元二分法模型,利用ENVI 5.3和ArcGIS 10.2分析库布齐沙漠1989—2019年植被覆盖度(FVC)时空动态变化特征。[结果](1)在时间变化上,近30 a间库布齐沙漠植被覆盖度整体呈增长趋势,平均植被覆盖度由0.104增长到0.243。在空间分布上,库布齐沙漠植被覆盖度呈现由西向东、向北增加的特征。(2)库布齐沙漠植被覆盖在1999—2004年和2009—2014年均呈现退化趋势,平均植被覆盖度分别减少0.053和0.054,退化面积分别为3 870.22和6 093.59 km~2,退化程度均以植被覆盖度减少10%～30%为主。[结论] 1989—2019年库布齐沙漠植被覆盖度总体有所改善,未来该区生态修复重点关注低植被覆盖区域。     

绿洲——荒漠交错带活化沙丘的植物群落特征分析

以民勤绿洲-荒漠交错带活化沙丘上的植物群落为对象,研究了活化沙丘不同部位的沙地植物群落物种组成、结构和多样性的变化。研究结果表明:从活化沙丘的下部、中部、丘顶,到背风坡的中部、下部,再到丘间低地,每一个生境对应着不同的群落类型。各部位不仅植物种类和数量存在差异,而且群落结构差异明显,其中丘顶为一年生草本植被构成,而丘间低地处只有灌木。群落物种多样性与相似性指数表明,从沙丘下部到丘顶再到丘间地,生态因子的差异对物种的分布格局产生了影响,从而导致了群落结构和功能发生了变化。活化沙丘植被简单,退化严重,需加强保护,防止继续退化。     

山区植被覆盖度变化的地形分异特征——以贵州开阳县为例

植被覆盖度是生态恢复的重要指示器,研究其变化特征可为资源合理利用、生态恢复提供科学参考。以贵州省开阳县为研究区,基于landsat4-5 TM,Landsat8 OLI遥感影像,获取2002年、2019年30 m分辨率植被覆盖度数据,从阴坡与阳坡视角研究山区植被覆盖度变化和地形分异特征。结果表明:(1)2002—2019年阴坡与阳坡植被覆盖度总体呈南高北低分布,期间阴坡与阳坡植被总体处于恢复趋势。(2)研究时段内阴坡与阳坡植被覆盖度随海拔上升表现为增加趋势; 海拔小于600 m的地区阳坡和阴坡植被覆盖度差距最大; 2019年二者植被覆盖度在海拔小于600 m的地区下降明显,高于800 m的地区均有较大提升。(3)阴坡和阳坡植被覆盖度随坡度增加总体呈上升趋势,坡度大于35°后二者差异增强; 植被覆盖度增量随坡度增加总体表现为上升—下降特点。(4)阴坡和阳坡植被覆盖度随地形起伏度增加呈上升趋势。2002年阳坡各等级地形起伏度的植被覆盖度总体高于阴坡,2019年二者植被覆盖度差异性随地形起伏度上升而增强。综上,阴坡和阳坡植被覆盖度与海拔、坡度、地形起伏度呈正相关关系,二者在不同等级地形梯度上具有较大差异性。地形因子对山区阴坡、阳坡植被覆盖度的影响是多方面的,不仅从海拔和坡向上影响水热组合条件,也从坡度和地形起伏度上影响人类对山区林地资源的开发利用。     

砒砂岩-黄土沟谷土壤含水量的时空变化

以晋、陕、蒙交界地区常见的砒砂岩-黄土丘陵沟谷为研究对象,分别于2005年7月和lO月对沟谷不同部位土壤含水量进行了测定.结果表明,其时空变化特征明显.(1)沟谷不同部位土壤平均含水量大小为7月份:沟谷底部14.44%,阳坡顶部9.29%,阴坡顶部9.01%,阴坡中部8.25%,阳坡中部6.36%;10月份:沟谷底部9.96%,阴坡顶部9.81%,阳坡中部9.48%,阴坡中部9.09%,阳坡顶部8.06%.(2)砒砂岩平均含水量季节变幅小,属稳定型;黄土及有冲积层的黄土平均含水量季节变化较大,属波动型.(3)在砒砂岩剖面上,泥岩含水量显著大于砂岩,砒砂岩坡面平缓的地段贮水能力比陡的地段大.(4)在黄土剖面上,明显出现土壤干层现象,在夏季、秋季降雨较少的情况下,土壤水分会严重降低,土壤水分处于负补偿状态,土壤干层距地表更深.在半干旱地区的砒砂岩-黄土丘陵沟壑区,黄土剖面土壤干层的发生是一个自然现象,随降雨量的多寡,呈消长状态.     

基于3S技术的库布齐沙漠抛物线形沙丘形态变化研究

以库布齐沙漠南缘典型抛物线形沙丘为研究对象,利用差分GPS实测数据,通过GIS空间插值生成DEM,提取地形因子和形态参数.利用多期高分辨率遥感影像,获取环境本底,同时结合气象数据,对抛物线沙丘形态变化进行分析.结果表明,沙丘平面形态呈U型,丘臂指向W;纵剖面上迎风坡较缓,背风坡较陡,横剖面不对称;沙丘平均移动速度为11.69 m/a;沙脊线所夹中轴线走向为WNW-ESE,与盛行风或合成输沙方向一致;油蒿灌丛分布在两翼及其间平坦地,植被盖度年均减少0.95％;在长期合成风的作用下,沙丘向前移动,两丘臂间的油蒿灌丛发生阶段性的自然恢复.     

乌兰布和沙漠沿黄河区域下垫面特征及风沙活动观测

为明确乌兰布和沙漠沿黄河区域下垫面特征与风沙活动特点,该文对该地区的沙丘形态、粒度特征、风速、输沙率与风沙流结构及其相互关系进行了野外调查与室内分析。结果表明:研究区横向沙丘平均宽-高比约为12.75。沙丘表面平均粒径与分选系数呈现出由丘间地至落沙坡逐渐减小的趋势,偏度则呈现出增大趋势。沙丘各部位粒度累计分布曲线均为正偏、单峰态分布。在净风与起沙风环境下,仅丘间地与沙丘顶部风速廓线呈对数形式分布;迎风坡坡脚处风速廓线多呈幂函数分布;落沙坡与背风坡坡脚处风速廓线分布形式不统一。无论在高风能环境下还是低风能环境下,从丘间地至背风坡坡脚,沙丘断面近地表风速呈减小(至迎风坡坡脚),增大(迎风坡坡脚至丘顶),再减小(丘顶至落沙坡),再增大(落沙坡至背风坡坡脚)趋势。沙丘顶部是风沙活动最为强烈的部位,沙丘各部位90%以上的输沙量集中到10cm高度以下;沙丘各部位的风沙流结构均服从三次函数分布。最后,该文针对该区域下垫面与风沙活动的特点和危害,提出相应的防治对策,以期对该区域风沙危害的防治提供参考。     

策勒绿洲-沙漠过渡带不同沙丘的沉积物粒度特征及沉积环境

[目的]通过对策勒绿洲—沙漠过渡带不同沙丘类型下风沙沉积物粒度、磁化率分布特征及环境敏感粒级组分进行分析,探讨不同沙丘类型下风沙沉积物相关参数及分布规律。[方法]基于绿洲—沙漠过渡带4种沙丘各部位粒度数据及磁化率数据,采用数理统计方法进行相关性分析。[结果]4种沙丘在不同地貌部位表层的沙物质粒级含量有所差别,回涡、灌丛、新月形及风影沙丘表面沙物质主要由极粗粉砂、极细砂、细砂组成,百分含量总和由小到大依次为96.71%,97.54%,98.48%,98.65%。4种不同沙丘表面沙物质分选性均为分选中度好。不同沙丘的峰态平均值介于0.93～1.02,属于中等峰态,从总体上分析4种沙丘的峰态值从迎风坡底到顶部逐渐增大,顶部到背风坡底部逐渐减小。新月形沙丘偏度值最小,偏度值介于-0.03～0.01,主要表现为对称,风影、回涡及灌丛沙丘偏度值介于-0.04～0.44,为对称和正偏。风影、灌丛及新月形沙丘表面沙物质平均粒径与偏度值呈极显著正相关(p<0.01),表明沙粒平均粒径愈粗愈趋向正偏。风影、回涡及新月形沙丘表面沙物质偏度与峰态呈极显著正相关(p<0.01),沙物质分选性愈差,就...     

库姆塔格沙漠沙丘的粒度特征

通过两次野外实地调查取样和室内分析,结果表明:库姆塔格沙漠中沙丘形态丰富多样,金字塔(星形)沙丘、线形沙垄、格状沙丘、羽毛状沙丘在这里都有分布。组成金字塔沙丘、线形沙垄、格状沙丘、羽毛状沙丘羽轴的沙粒中0.25~0.063 mm颗粒占绝大多数,其次是0.5~0.25 mm和1~0.5 mm的颗粒,形成羽毛状沙丘羽枝的颗粒在暗带以2~0.5 mm的颗粒为主,在明带以0.5~0.063 mm的颗粒为主,各沙丘沙粒的分选性较好。由于各自形成地形、气候等条件的差异,各沙丘类型沙粒粒径在沙丘不同部位都有各自的特点。金字塔沙丘东北坡沙粒粒径从顶部到基部保持一致,南坡和西北坡从顶部到基部沙粒逐渐变粗;线形沙垄除西南坡基部较粗外,其它部位沙粒粒径分布一致;格状沙丘格子外部坡面沙粒相对格子内部坡面的同一部位沙粒要粗;新月形沙丘基部和顶部沙粒较粗,而中部颗粒较细;羽毛状沙丘“羽轴”沙粒分布与新月形沙丘相似,“羽枝”由较粗和较细沙粒含量高低间隔分布形成。     

Transformation of the Bryansk Paleosol in Microdepressions in the Center of the East European Forest-Steppe during the Maximum of Valdai Glaciation and in the Holocene

Eurasian Soil Science - Recent and Late Pleistocene soils of the central forest-steppe in the East European Plain have been studied. The main objective of the work is to reveal changes in the...     

Changes in the structure of the rhizosphere complex of actinomycetes in the ontogenesis of winter rye

Changes in the taxonomic structure of actinomycetes in the rhizosphere of winter rye (Secale cereale L.) growing on acid soddy-podzolic soil were studied. During the first stages of ontogenesis of winter rye, the rhizosphere complex of mycelial prokaryotes was characterized by a relatively level generic structure (with respect to the indices of abundance and frequency of particular genera), low values of the species diversity, and low domination frequency of the species from the Streptomyces genus. The numbers and species diversity of the streptomycetes increased during the further growth of the winter rye, so that streptomycetes became a dominant group in the complex of the rhizosphere actinomycetes. According to the two-way ANOVA, the population density of the Micromonospora and the Streptosporangium genera in the rhizosphere was mainly dictated by the winter rye variety, whereas the population density of the streptomycetes depended on the particular stage of the winter rye development. The differences between the actinomycetal complexes characteristic of different varieties of winter rye at the early stages of its development was leveled by the end of the winter rye growth.     

Evolution of forest pedogenesis in the south of the forest-steppe of the Central Russian Upland in the Late Holocene

The Late Holocene stage of forest pedogenesis has been studied on the interfluves along river valleys in the forest-steppe zone of the Central Russian Upland. The development of gray forest soils from the former chernozems as a result of the Late Holocene advance of forest vegetation over steppes is discussed. It is argued that the climatic conditions of the Subatlantic period were unstable, so that multiple alternation of forest and steppe vegetation communities took place. This specified a complex character of soil evolution upon contrasting substitution of forest pedogenesis for steppe pedogenesis. On the interfluves near the natural drainage network (balkas, ravines, and steep slopes of river valleys), the climate-driven dynamics of forest and steppe vegetation with corresponding changes in the character of pedogenesis could take place during the entire Holocene, which is reflected in a lower thickness of humus profiles and deeper leaching of carbonates from chernozems of the Early Iron Age in comparison with their analogues formed under steppe cenoses in central parts of the interfluves. Two variants of the evolution of gray forest soils can be suggested: the pulsating evolution typical of balkas and interfluves near river valleys and the continuous progressive evolution typical of automorphic (plakor) positions in central parts of the interfluves.     

Accumulation of chemical elements in the raised peatbogs of the subtaiga Trans-Urals in the Holocene

The results of studying the variability of the geochemical parameters of the layers of the Sartamskii upland peatbog in the south of Tyumen oblast based on the radiocarbon time scale are given. Four basic types of peat and stages of peat deposits formation in the Holocene are distinguished: the organomineral layer of the sediments in a paleolake (up to 5065 ± 60 years ago), the low moor layer (4300–4900 years ago), the transitional layer (3100–4300 years ago), and the high moor peat (250–3100 years ago). The upper peat layer (last 200–300 years) significantly differs from its main portion; in particular, it is characterized by an increased ash content and the accumulation of a number of elements. The relationship between the various characteristics of the deposit is analyzed using principal component analysis, and the conditions of the formation of the peat deposit in different time periods are estimated, including the climatic conditions (in relative units). The anthropogenic signal of the accumulation of some elements in wetland systems is identified.     

论图书馆数字馆藏资源建设中亟待解决的问题

论述数字馆藏的产生、概念和特点,分析数字馆藏资源建设中存在的问题,探讨数字馆藏资源建设中应采取的策略。     

Variations in the composition of the sap of zea mays with the increase in osmotic pressure of the nutritive solution

The alterations are studied which are produced in the content of mineral elements and organic fractions of sap with the increase in the osmotic pressure of the nutritive solution at levels of 2.0; 3.5 and 5.0 atm., obtained through the addition to the nutritive solution either of magnesium sulphate or PEG‐4000.

Through the effect of the osmotic pressure, the transformations are modified of the nitrogen and mineral phosphorus at organic fractions experience a series of modifications which produce different values in the Nm%TSN and Pm%TSP ratios with respect to control. Through action of the specific effect of magnesium sulphate, the reducing sugars concentrations in sap having an important increase.     

Seasonal changes in the communities of microorganisms and algae in the litters of tree plantations in the steppe zone

Specific structural and dynamic parameters of communities from various ecological and trophic groups of microorganisms and algae in the litter of artificial tree stands were studied using the example of the Staro-Berdyansky Forest in the steppe zone of Ukraine. The composition of the communities was shown to vary by seasons and depend on the forest-forming woody species. In spring, in all the litters, the maximal number of actinomycetes and aminotrophs was recorded; in the leaf litter, the number of phosphate-mobilizing organisms was also the largest. In summer, the development of cellulolytic organisms, ammonifiers, and nitrogen-fixers was intensified; in autumn, the number of micromycetes and oligotrophic organisms decreased. The composition of dominants, the species richness of algae and their abundance also varied by seasons. Representatives of the Chlorophyta division predominated. The highest species richness of algae was characteristic of the spring litter samples, and their number, for the spring and autumn ones. The positive correlation was established between the numbers of micromycetes and oligotrophs, micromycetes and algae. The negative correlation was found between the numbers of micromycetes and actinomycetes, cellulose-decompose bacteria and algae in the litters.     

Changes in the physical properties of soils in the Kamennaya Steppe under the impact of shelterbelts

The physical properties of ordinary chernozems and meadow-chernozemic soils under different land management practices (maple, larch, birch, and pine sections of the shelterbelts; continuous (since 1959) fallow; and arable field (since 1952)) were studied in the Kamennaya Steppe. The soils had favorable physicochemical properties, light clayey texture, and high microaggregation independently from the type of land management. The long-term impact of the shelterbelts improved the soil structure in the upper part of the humus horizon: the content of agronomically valuable aggregates increased, the content of coarse aggregates (>10 mm) decreased, the aggregation coefficient increased by 3.7–4.3 times, and the water stability of the aggregates became by 8–12% higher. The soils under the shelterbelts were characterized by minimum values of the bulk density and solid phase density and by maximum values of the total, active, and air porosities. At the same time, no considerable differences between water reserves in the studied range of soils were detected. The ratio of the optimum productive water range to the active (productive) water range (OPWR/AWR) within the upper soil meter varied from 0.42–0.44 to 0.45–0.54. This points to changes in the character of perched water: the content of intra-aggregate capillary-perched water decreases, and content of film perched water increases down the soil profile.     

近50年博斯腾湖水位变化特征分析

以干旱区博斯腾湖为研究对象,依据博斯腾湖1956—2012年期间的水位监测数据,采用小波分析及MannKendall(M-K)趋势检验等统计学方法,揭示了近50a博斯腾湖水位变化趋势及规律。结果显示:博斯腾湖1956—2012年水位变化分为3个阶段下降(1956—1987年)—上升(1988—2002年)—下降(2003—2012年),其中1956—1987年水位下降了3.39m;1988—2002年上升了3.7m;2003—2012年再次下降了3.21m。水位总体上呈现出显著的下降趋势,且通过了α=0.05时的显著性检验。就其周期性变化规律而言,博斯腾湖水位存在18a的主周期,而38a的周期由于水位资料序列有限难以确定,需要更长的资料序列进行分析验证。     

Quality of used-snow discharged in the ST-Lawrence river,in the region of the Montreal Harbor

Snow disposal creates problems each year in Montreal. Snow dumping in water courses is favored due to both esthetic and economic considerations. Used snow must be considered as a potential pollutant. Its impact on the aquatic receiving environment is not well known. With river dumping in progress, snow samples were collected at 3 sites: Concorde Bridge, and at piers 30 and 52 in Montreal Harbor. Analysis of 28 routine parameters demonstrated that the quality of snow ultimately dumped in the river varies considerably according to its sources and the time it remains in the streets. Used-snow from residential areas was shown to be less polluted than the snow from commercial areas. Furthermore, from the total number of sampled districts, used-snow dumped at pier 30 appears to be relatively more polluted as it originated from downtown areas where vehicle circulation is more dense. Heavy metals in particles sizes between 0.45 and 63 μm represented more than 70% of the measured suspended solids which reflects the risk of bioaccumulation via benthic organisms. Principal component analysis of present data suggests that with analysis of chlorides, suspended solids and Pb alone, it is possible to approximately determine the quality of used-snow.