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1.
The composition and structure of tree stands near the timberline have been studied on different slopes and at different elevations in the Tylaisko-Konzhakovsko-Serebryanskii Massif, the North Urals. It has been found that the upper limits of tree stands with different degrees of canopy closure have risen considerably (by about 100 m of elevation) since the mid-19th century, although the formation of these stands started as early as the late 18th century. Woodless areas in the eastern part of the massif started to be colonized by Larix sibirica in the late 18th to early 19th centuries; those in the western part, by Picea obovata in the mid-19th century; and in the southern part, by Betula tortuosa in the late 19th century. Analysis of meteorological data provides evidence for warming and increasing humidity of the climate since the late 19th century. Favorable climatic changes that facilitated the expansion of the forest have taken place both in the summer (prolongation of the growing period) and in winter seasons (increase of air temperature and precipitation). The observed differences in the composition and dynamics of tree stands between the studied areas of the mountain range are most probably explained by different requirements of tree species for the depth of snow cover and the degree of soil freezing.  相似文献   

2.
贵州地区在小冰期的气候环境状况及其对人类活动的影响研究缺乏,综合历史文献资料分析与地质记录的研究仍有待加强。基于1470~1949年贵州地区旱涝历史文献资料重建该区干湿变化序列,然后运用互信息的相关分析方法对此序列进行检验,再通过小波分析探究其干湿变化过程与周期。同时,结合高分辨率石笋δ18O序列、海洋热状况和国家与地方政权的动荡情况,讨论其控制因子及其对人类活动的影响。研究表明:(1)贵州地区15世纪末期气候偏干,16世纪整体较湿润,在经历了17世纪前期的干旱期后,从17世纪中期至20世纪前期为一个长期较稳定的湿润期,与众多古环境研究记录较为吻合;(2)小波分析表明干湿变化具有128~155年、32~55年、11~20年的周期,反映其干湿变化主要受太阳活动控制;(3)贵州地区湿润程度受南亚夏季风强度、ENSO、AMO等因素影响,且对当地政治活动和地表生态环境产生了重要影响。  相似文献   

3.
Paleoethnobotanical materials and buried soils from the site of the ancient settlement of Idnakar and neighboring archaeological monuments were analyzed to reconstruct the agroecosystems of the 9th through the 13th centuries AD near the present-day city of Glazov. The results provided data on the main features of the agroecosystem structure and composition, climate, and agriculture in the Middle Ages.  相似文献   

4.
The periodicity of fires in larch forests of Evenkia and their relationship with landscape elements have been studied. Cross-sections with “burns” in them caused by past fires have been analyzed in 72 test plots; the fire chronology encompassed the period from the 15th to the 20th century. The between-fire intervals (BFIs) have been calculated by two methods: (I) on the basis of burns alone and (II) on the basis of burns and the start of growth of the new generation of larch after the earliest fire. The BFI depends on local orographic features; it is 86 ± 11 (105 ± 12), 61 ± 8 (73 ± 8), 139 ± 17 (138 ± 18), and 68 ± 14 (70 ± 13) years for northeastern slopes, southwestern slopes, bogs, and flatlands, respectively. The mean BFIs calculated by methods I and II are 82 ± 7 and 95 ± 7 years, respectively. The permafrost horizon rises at a mean rate of 0.3 cm per year after a forest fire. It has been shown that the number of fires regularly peaks at periods of 36 and 82 years. There is also a temporal trend in fire frequency: the mean BFI was approximately 100 years in the 19th century and 65 years in the 20th century.  相似文献   

5.
The structure of Siberian stone pine (Pinus sibirica Du Tour.) and Siberian larch (Larix sibirica Ledeb.) stands and specific features of their formation have been studies in the forest-tundra ecotone on the North Chuya Ridge (2235–2475 m a.s.l.). Changes in the structure of these stands along the transition from the upper boundary of closed forests to the high-mountain tundra have proved to have an ambiguous pattern. Both tree species form mixed clusters of similar-aged trees in the lower part of the ecotone but grow singly, in scatters, in its upper part. The formation of conifer stands (tree clusters) in the lower part of the ecotone, on the slopes of the Aktru River valley, began during climate warming in the second half of the 19th century. The expansion of confers to its upper part took place markedly later, in the early 20th century (Siberian larch) or even in the 1930s (Siberian stone pine).  相似文献   

6.
太湖流域的稻麦两熟复种大约产生于东晋南朝时期(317~589年),此后这一种植制度长期存在,并不断有所发展。考察发现,此一区域的稻麦两熟在历史上的大多数时候并无突出的季节矛盾,只是有两个时期例外。这两个时期一是明末清初,一是19世纪。太湖流域历史上突出的季节矛盾不由人口、品种等社会原因引起,而由气候变化这一自然因素导致。明末清初和19世纪分别是历史上最为寒冷的时期,是气候变冷造成了这一区域稻麦两熟突出的季节矛盾  相似文献   

7.
In the diurnal lepidopteran fauna of the northern taiga subzone in the western Russian Plain, the species inhabiting primary biotopic complexes typical of this subzone currently account for slightly more than 60% of the total species richness and abundance. A large part of the fauna is represented by the species of more southern origin, whose expansion to the northern taiga was caused by anthropogenic transformation of landscapes between the 12th and 20th centuries and recent climate warming.  相似文献   

8.
Changes in the altitudinal position of the timberline in high mountain areas of the Nether-Polar Urals and basic factors that influence such changes have been revealed on the basis of comparison of the age structure of Siberian larch (Larix sibirica) and arctic birch (Betula tortuosa) tree stands and photographs made in different years. On the mountain slopes studied, an upward shift of the timberline took place in areas covered in winter with thick snow (in the late 18th century), with Siberian larch being the pioneer species. Larch began colonizing areas with a thin snow cover in the 20th century. Birch appeared later and has since strengthened its positions. The increase in winter temperatures and precipitation facilitated the expansion of the forest.  相似文献   

9.
长江经济带城镇化的发展为工业化提供了强劲动力,但同时工业用水的猛增促使水资源供需矛盾更加尖锐以及水环境污染愈发严重。通过建立工业用水与城镇化之间的脱钩模型,利用“十一五”和“十二五”时期的面板数据,研究长江经济带各省市工业用水与城镇化的脱钩状态,并在此基础上借助对数迪氏指数法考察工业用水量的具体影响因素。研究发现:(1)2006~2015年长江经济带城镇化对工业用水总体呈现脱钩状态,但“十一五”期间表现为弱脱钩状态,而“十二五”期间表现为强脱钩状态;(2)长江经济带各省市脱钩关系存在较大的时空差异,长江三角洲经济区、长江中游经济区以及长江上游经济区明显处于不同的脱钩状态;(3)城镇化影响工业用水的四大效应中,技术效应抑制工业耗水,产出效应则促进工业耗水,而结构效应和人口效应对工业用水的影响随时空变化而变化。据此,提出通过技术节水提高工业用水的利用效率,因地制宜促进区域平衡发展等建议。 关键词: 城镇化;工业用水;脱钩模型;LMDI模型;长江经济带  相似文献   

10.
Studies on paleosols under an archaeological landmark of a rare type (a complex of kurgans with “whiskers”) dating from the Early Iron Age (the fourth century AD) have been performed in the steppe zone of the Transural Plateau. The size and shape of third-order soil polygons under stony ridges (“whiskers”) between the kurgans have been described in detail. The results have shown that the paleosol under the kurgans erected at the turn of the Late Sarmatian and Hun times (1600 years ago) is characterized by a higher humus content and deeper location of the carbonate horizon, compared to the recent soil. This indicates that an increase in atmospheric humidity took place in the fourth century AD.  相似文献   

11.
长江下游地区过去300年的气候变化   总被引:5,自引:5,他引:0  
采用重建的合肥年冬季温度序列和降水序列分析了长江下游地区过去300年的气候变化。在温度序列中,18世纪的大部分,19世纪中期和20世纪的温度较为温暖,最暖的十年出现于1990s,而最冷的年代为1870s,该温度序列与邻近其它地区重建的温度序列具有很好的一致性。降水序列显示年至多年尺度的气候波动,湿期发生于1730s-1760s,1844-1854年,1866-1910年,而干期出现于1806-1825年,1855-1867年,以及20世纪的大部分。温度和降水间的关系表明,在年至十年尺度上,该地区气候变化主要以暖干或冷湿为主。  相似文献   

12.
A fire at the Windscale plant at Cumbria in the UK between the 10th and the 11th of October 1957 resulted in the first publicised release of radioactivity to the wider environment. The cloud of contamination passed to the southeast of England before travelling northwards on the 14th of October as a result of weather fronts in Europe. Monitoring of radioactive fallout in Norway was at the time conducted by the Norwegian Defence Research Establishment (FFI) using a network of air and precipitation monitoring stations. This article presents results from these monitoring activities which were originally contained in laboratory journals and a series of internal reports produced by FFI. Although mainly classified during the 1950s and 1960s, recent years have seen the incremental declassification of these reports and as the 50th anniversary of the accident approaches, a distillation and reanalysis of this information has been conducted. Results indicate that radioactivity from Windscale was first detected at Bergen and Sola in the south west of Norway and a little later at Vaernes, significant amounts of radioactivity being deposited at these locations during the second and third weeks of that month. Results relating to concentrations of activity in air and precipitation and fallout levels are presented for the relevant period and discussed in relation to fallout levels in Norway during the period 1957-1960.  相似文献   

13.
At the beginning of the nineteenth century, a significant change in sedimentation took place along the middle course of the Obra River (W Poland): a “natural” channel bed was replaced by three artificial canals. Before that time the Obra River bed had been characterized by various river patterns (braided, meandering and disappearing in wetlands). GPR (ground-penetrating radar) surveys and the analysis of satellite and aerial images were carried out to retrace the natural river course near the village of Kopanica. The GPR, ground-truthed with core data, revealed that at least two types of the river pattern had been functioning here before the period of the hydrotechnical works: a large-scale meandering pattern (width-to-depth (w/d) ratio ranging from 15 to 40) and a relatively smaller-scale multi-channel pattern (w/d = 11–22). Possibly, the transformation was caused by forming a series of large floods followed by in-channel aggradation and avulsions. Next, the multi-channel pattern was artificially transformed into the North Obra Canal. This paper discusses possibilities of a creation of network of channels that were active after the construction of the North Obra Canal in the beginning of the nineteenth century. Such intervention would increase natural values of the presented section of the Obra valley. The presented study also shows that a detailed analysis of history and evolution of a given river course is needed before undertaking any restoration works.  相似文献   

14.
The undulating loess Kanczuga Plateau, 250–270 m a.s.l., is located in the temperate climatic zone of Central Europe, within the northern foreland of the Carpathians. It is dissected by a network of valleys 30–60 m deep, infilled with several metres of complex minerogenic and organic deposits which started to accumulate during the early Holocene. The southern side of one of these valleys is dissected by several dry valleys. The mouth sections of these valleys have buried surface comprising peat and/or organic silts, overlain by sandy–silty alluvium. 14C dates indicate that the alluviation of these valley floors, which proceeded from the headwaters to the mouth sections, began in the 1100 ad. The gradual intensification of soil erosion in the upper part of the catchment and associated sedimentation probably encompassed only a few centuries, with greatest alluviation during the Little Ice Age. This plateau, which is under the influence of more continental climatic conditions than the low-mountain and upland regions of Western Europe, features more climatic contrasts. Here environmental changes triggered by land use were superimposed on climatic change. The most intensive processes of soil erosion and sediment transfer as well as alluviation, coincided with the first phase of cooling during the Little Ice Age. It was the final stage of the intensification of these processes, probably more intensive than its initial phase in the eleventh century, caused primarily by deforestation resulting from the development of agriculture.  相似文献   

15.
The spatiotemporal dynamics of forest-tundra communities in the 20th century have been studied in the timberline ecotone of the Polar Urals. Maps reflecting the distribution of different types of forest-tundra communities have been made, and data on the morphological and age structure of tree stands have been obtained for three time sections (the mid-1910s, 1960s, and 2000s). They show that open and closed forests have markedly expanded due to natural afforestation of the tundra and increase in the density and productivity of existing forest stands. The unidirectional pattern of plant community transition (from the tundra to closed forests) and meteorological data provide evidence that this transition has been conditioned by climate warming and increasing humidity recorded during the past 90 years.Translated from Ekologiya, No. 2, 2005, pp. 83–90.Original Russian Text Copyright © 2005 by Shiyatov, Terentev, Fomin.  相似文献   

16.
以吴越文化区内国家首批公布的241个传统村落为研究对象,运用空间分析法,利用ArcGIS 10.2等软件探究吴越文化区内传统村落的空间分异规律及其在不同空间尺度上的分布特征。结果表明, 吴越地区传统村落分布南多北少、西多东少,呈集聚分布,传统村落的高密度集聚区与热点区分布相似:(1)西部的皖南山区和西南部的浙南山地地区为高密度集聚区,其中黄山市歙县、黟县,丽水市松阳县及上饶市婺源县均为二阶热点区;(2)在文化亚区尺度上,新安文化亚区密度最大,越文化亚区分布数量最多;在聚落景观区尺度上,传统村落集中于皖南古徽州聚落景观区、浙中丘陵盆地聚落景观区和浙南中山聚落景观区;(3)地形、中心城市影响以及历史文化因素为影响传统村落分布的3个因素。 关键词: 传统村落;空间分布;乡村振兴战略;影响因素;吴越文化区  相似文献   

17.
Changes in the vegetation and fire regimes in the central East European Plain during the second half of the Holocene have been reconstructed based on the results of paleobotanical analysis and radiocarbon dating of material from a section of peat deposit in the Mordovia State Nature Reserve. It has been shown that birch–pine forests were widespread in the region between 7000 and 5000 yr BP, with the frequency of fires in that period being high (the fire return interval ranged from 10–20 to 100 years). Beginning from 5000 yr BP and to the early 20th century, broadleaf forests were dominant, with the fire return interval increasing to 300–500 years or longer.  相似文献   

18.
The purpose of this study was to investigate the climate change impacts, vulnerability and adaptive capacity of the electrical energy sector in Cyprus. Spatial vulnerability of the island was assessed using the degree-day indicator to investigate heating and cooling demands in the near future using daily temperature projections from regional climate models (RCMs). Using daily electrical energy consumption data for the present climate, an impact model linking consumption and temperature was constructed and this relationship was projected to the future climate using the data from the RCMs and assuming the same technology use. Our impact model results showed that for the period between November and April (‘cold period’), a decreasing trend in electrical energy consumption is evident due to warmer conditions in the near future, while for the period between May and October (‘warm period’), an increasing trend in electricity consumption is evident as warmer conditions dominate by 2050. Regarding the spatial vulnerability assessment, the cooling degree-day indicator testified that major increases in cooling demand, between 100 and 200 degree-days, are expected in inland and southern regions during the summer in the near future. In addition, increases of about 20–50 degree-days are anticipated during autumn. Conversely, energy demand for heating is projected to decrease during spring and winter, especially in the higher elevation parts of the island. More precisely, reductions of about 30–75 degree-days are projected during spring, while greater reductions of about 60–90 degree-days are expected during winter in heating demand, especially for in the near future. The ability of the energy sector to adapt and follow these changes was deemed to be satisfactory reducing the overall vulnerability of the sector to future climate change.  相似文献   

19.
Between the tenth and twentieth century the population of Paris city increased from a few thousand to near 10 million inhabitants. In response to the growing urban demand during this period, the agrarian systems of the surrounding rural areas tremendously increased their potential for commercial export of agricultural products, made possible by a surplus of agricultural production over local consumption by humans and livestock in these areas. Expressed in terms of nitrogen, the potential for export increased from about 60 kg N/km2/year of rural territory in the Middle Ages, to more than 5,000 kg N/km2/year from modern agriculture. As a result of the balance between urban population growth and rural productivity, the rural area required to supply Paris (i.e. its food-print) did not change substantially for several centuries, remaining at the size of the Seine watershed surrounding the city (around 60,000 km2). The theoretical estimate of the size of the supplying hinterland at the end of the eighteenth century is confirmed by the figures deduced from the analysis of the historical city toll data (octroi). During the second half of the twentieth century, the ‘food-print’ of Paris reduced in size, owing to an unprecedented increase in the potential for commercial export associated with modern agricultural systems based on chemical N fertilization. We argue that analysing the capacity of territories to satisfy the demand for nitrogen-containing food products of local or distant urban population and markets might provide new and useful insights when assessing world food resource allocation in the context of increasing population and urbanization.  相似文献   

20.
Analysis of observational phenological data has indicated that the length of the vegetation period (VP), here defined as the time between leaf onset and leaf colouring (LC), has increased in the last decades in the northern latitudes mainly due to an advancement of bud burst. Analysing the patterns of spring phenology over the last century (1880–1999) in Southern Germany showed that the strong advancement of spring phases, especially in the decade before 1999, is not a singular event in the course of the 20th century. Similar trends were also observed in earlier decades. Distinct periods of varying trend direction for important spring phases could be distinguished. Marked differences in trend direction between early and late spring phases were detected, which can be explained by different trends in March and April mean temperatures. The advancement of spring phenology in recent decades is part of the multi-decadal fluctuations over the 20th century that vary with the species and the relevant seasonal temperatures. However, for all Natural Regions in Germany, spring phases were advanced by about 5–20 days on average between 1951 and 1999, LC was delayed between 1951 and 1984, but advanced after 1984 for all considered tree species and the length of the VP increased between 1951 and 1999 for all considered tree species by an average of 10 days throughout Germany.  相似文献   

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