首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Large-scale river training works have been carried out in the Hunter valley since 1955 in response to flood-driven channel changes. Vegetation was planted on in-channel benches induced by river training works to consolidate the deposits and to increase channel boundary roughness. Exotic species of vegetation such as willows and poplars were previously used. In 1983, ten trial sites were planted with various species of native vegetation. Survival rates were evaluated in 1987 and 1997. The most successful species planted was Eucalyptus camaldulensis with an overall survival rate of 77 per cent in 1997. The Acacia species were found to be short-lived, exhibiting a significant decline in survival rates between 1987 and 1997. Survival rates for most species were higher on sand-bed than on gravel-bed sites. This difference may be attributed to better drainage on benches at the sand-bed sites. Investigations of flood disturbance showed that between 1983 and 1997 the sites were flooded between four and 13 times. The survival rates of Grevillea robusta and Eucalyptus melliodora trees were negatively correlated with the total number of recorded floods at each site. Poor natural regeneration of planted species is attributed to a combination of periodic flooding, intensive weed growth, low light intensities at ground level and grazing disturbance. These trials were not well designed for statistical analysis but provide valuable long-term information on the suitability of various species for planting in riparian rehabilitation programs. Such information is of relevance not only to river and catchment management authorities, but also to community groups.  相似文献   

2.
Pine stumps have been found preserved in blanket peats at altitudes of up to 793 m OD in Scotland. Radiocarbon dating by other researchers has demonstrated that these sites were not all contemporary, but most fall within the mid‐Holocene period. Palynological, dendrochronological and stable isotope analyses have previously been carried out on these fossil pine stumps, but not palaeoentomological analysis. This paper reports on the results of an analysis of the fossil beetle remains from two of these sites in the Cairngorms, Monaltrie Moss and a moss on the Mar Lodge estate. The insect faunas indicate that acidic wetland was colonised by pine trees, which developed into mature woodland. The dominance of saproxylic (deadwood) faunas in comparison to those associated with healthier trees suggests that the woodland was always under stress. The pine fauna at Mar Lodge was replaced by montane wetland species once the pine trees died out.  相似文献   

3.
This paper provides the results of the dendrochronological analyses of seven wood samples from the Ottoman fortress of Seddülbahir on the Gallipoli Peninsula or Turkey. It concludes that the trees were cut in the late spring of 1656. The data collected allows the first building phase of the fortress to be securely dated. By bringing together the dendrochronological results with various archival records about the fortress, a more precise building chronology for the fortress can be reconstructed. The probable initial period of construction was between 1656 and 1661.  相似文献   

4.
Core sampling is normally used for dendrochronological age determination of both timber and living trees. As core sampling can seriously damage artefacts, a photographic method was tried on 29 wooden objects made of Scots pine (Pinus sylvestris L.). These were photographed and tree‐ring sequences for dendrochronological analysis were measured on the photographs in the laboratory. Nine objects could be dated. The undatable objects had few tree‐rings or a non‐matching tree‐ring pattern. The region in Norway where the material had grown could be determined by matching against various regional chronologies.  相似文献   

5.
The dendrochronological studies were carried out on very well preserved sub-fossil pine wood found in the biogenic deposits of the Rucianka raised bog (NE Poland). Local floating chronologies, covering the period 990-460 cal BC, were dated on the basis of radiocarbon analyses. Growth depressions in annual treering widths indicated periodical deterioration of the environmental conditions, which affected tree growth. Identified germination and dying-off phases (GDO) should be related to the wetter climatic periods. The extinction of trees took place during periods of higher groundwater level which, in turn, caused favourable conditions for growth of young pines.  相似文献   

6.
Extracting cores from a tree using an increment borer has been standard practice in dendrochronological studies for a long time. Although empirical rules exist regarding how many samples to take and which methodology to apply, comparatively few studies provide quantification of the similarity of relative tree-ring-widths (TRW) around the stem circumference. The aim of this study was therefore to precisely measure the similarity of standardised TRWs around the stem circumference and to provide objective suggestions for optimal core sampling of Norway spruce (Picea abies Karst. [L.]) and European beech (Fagus sylvatica L.) growing in Central European temperate forests. A large sample of cross-sectional discs was used from Norway spruce and European beech trees growing on various slopes, at different altitudes and biogeographic regions across the Czech Republic and Slovakia. The similarity of TRWs measured in different coring directions was analysed by testing the relativized TRW around the trunk (rTRW). Comparison of rTRWs revealed no significant differences between coring directions, indicating that the relative increment was the same around the radius. The results also showed the high similarity between the rTRWs to be independent of both slope inclination and altitude. Moreover, the reconstruction of proportional tree diameters and basal areas backward in time from one core sample and one measurement of tree diameter (basal area) at the time of sample extraction is possible with reasonable precision.  相似文献   

7.
The felling of the oak trees used to build the Karschau ship took place in or around the AD 1140s. The tree-ring curves from the oak planks from the Karschau Ship match best with site-means from Odense, a medieval town on the island of Funen, Denmark. New research being carried out by the author is allowing the determination of the provenance of ancient oak to a more local level. Through this dendrochronological research, it is now possible to differentiate between small regions of timber sources for shipbuilding, allowing a more nuanced interpretation.
© 2006 The Author  相似文献   

8.
J. HILLAM  I. TYERS 《Archaeometry》1995,37(2):395-405
Research into the dates of timber used for art-historical objects has provided a large data set on which to test standard dendrochronological techniques. Some 177 sets of tree-ring measurements, originally analysed by the late Dr J. M. Fletcher at Oxford University, have been re-examined independently in the tree-ring laboratories at the University of Sheffield and the Museum of London Archaeology Service. The results show a high level of agreement between the laboratories. In contrast, many of the dates produced by Dr Fletcher for the paintings are not confirmed. The two different approaches described here also resulted in remarkably similar internal groupings of the dated material. These groupings probably reflect the provenance of the timbers and suggest that two different areas of the eastern Baltic supplied the bulk of the material with smaller quantities of panels originating in Britain and central Europe.  相似文献   

9.
Abstract

Developing holistic accounts of indigenous peoples’ lifeways in colonial intercultural settings requires data that provide insights into patterns of landscape use and variations in social, economic, and cultural practices away from nodes of colonial activity. However, the mobile settlement patterns of some indigenous peoples mean that the data necessary for such investigations can be rare. In western Cape York Peninsula of northeastern Australia, culturally modified trees (CMTs) associated with the collection of wild honey or “sugarbag” provide opportunities to investigate indigenous patterns of landscape use and processes of economic change within colonial settings. Here we use CMT data to suggest that increased engagement with invader-settlers resulted in intensification of indigenous wild food production. This study exemplifies the complexity of socioeconomic shifts that accompanied European colonization worldwide, and illustrates how landscape-level data can provide information on the broader histories of indigenous peoples within colonial settings.  相似文献   

10.
Abundant wood remains and buried trees have been found in the western part of Lithuania near Zakeli?kiai and Lyduv?nai on Dubysa River (a tributary of Nemunas River) where deposits are rich in organic remnants and buried soils. In Zakeli?kiai and Skiru?iai sections of Dubysa River oxbow sediments were investigated by various methods (dendrochronological, carbonate, granulometric, pollen and mollusc fauna analysis). In addition, these sections were dated using the radiocarbon method. Samples were collected from deposits of Dubysa River outcrops. The studied oxbow lakes have existed for more than 5 thousand years (from ca. 4300 BC to 1000 AD). During this period organic rich deposits with trees and branches were formed in the oxbow lake. This indicates that at the end of Atlantic, during Subboreal and in the early Subatlantic periods there was a forest growing that contained mainly oaks which were falling down into an oxbow lake and later were covered by sandy and silty deposits. The granulometry of alluvial deposits, as well as the mixture of medium-grained sand and silt show different stages of Dubysa River palaeochannel formation: riverbed and oxbow lakes. Three climate warming cycles were revealed according to carbonate analysis data in all investigated sections. The rheophile thermophilous Holocene age molluscs species Bithynia tentaculata L., Unio cf. crassus Philipsson, Pisidium amnicum (Müller), Theodoxus fluviatilis (Linnaeus) have been found. The pollen composition and sequences have been divided into five local pollen assemblage zones (LPAZ) and described according to pollen spectra in each zone. In this way it is possible restore palaeoclimatic coherent evolution, trends and cyclical change.  相似文献   

11.
Large debris flows have destroyed the infrastructure and caused the death of people living in the Moxi Basin (Sichuan Province, Southwestern China). Inhabitants of the Moxi Basin live on the flat surfaces of debris-flow fans, which are also attractive for farming. During the monsoon season debris flows are being formed above the fans. Debris flows can destroy the houses of any people living within the fan surfaces. In order to prevent the adverse effects of flows, people plant alder trees (Alnus nepalensis) at the mouths of debris flow gullies running above debris flow fans. Alders are able to capture the debris transported during flow events. Trees are well adapted to surviving in conditions of environmental stress connected with abrupt transport and deposition of sediment from debris flows. Numerous wounds, tilting and bending of alder trees caused by debris flows only very rarely cause the death of trees. By dating scars and dating the time of alder tilting (through the analysis of annual rings), we have determined the frequency of debris flows occurring at the mouth of the Daozhao valley. In 1980–2012 within the studied debris-flow fan and the Daozhao gully, 2 large debris flow events occurred (1996, 2005) and some smaller events were probably recorded every 2–3 years.  相似文献   

12.
A detailed study of charcoal burning activities has been made for the Zoersel forest (Northern Belgium) based on an inventory of charcoal kiln remains, the analyses of wood charcoal and other charred botanical macroremains and radiocarbon dating of 10 of these kilns. Age determination of the youngest kilns was refined by dendrochronological analysis of trees growing on top of these kiln sites. The results show that, although many kilns were found, charcoal was produced in Zoersel only at certain moments during late and post-medieval times suggesting that charcoal burning was not a part of the regular management practice of these forests. The wood used for the production of charcoal mainly consists of taxa of alluvial (alder) forests while the kilns are situated on sites that currently are rather dry, with an oak dominated vegetation. For the older kilns, this contrast could be explained by an important change in local soil conditions. The younger kilns may be related to the conversion of alder woodland to grassland in the lower parts of the domain, with the kilns being constructed in the nearby dryer woodland areas.  相似文献   

13.
As part of a larger project promoting the development of historical dendrochronology in the Iberian Peninsula, ship‐timbers from the Arade 1 wreck (mostly planking and framing elements), stored at the DANS/IGESPAR in Lisbon, were examined. Of these, 52 samples were identified as deciduous oak (Quercus subg. quercus) and two as chestnut (Castanea sativa). Of 24 timbers selected for dendrochronological research, 23 could be dated, placing the origin of the wood in western France and the felling of trees between AD 1579 and 1583. Their homogeneity suggests they are part of the original construction, which probably took place shortly after AD 1583. © 2012 The Authors  相似文献   

14.
The forests of British North America were integral to Britain's maritime empire. Many of these timbers exist today as wooden beams and flooring at historical dockyards and garrisons such as the Royal Naval Dockyard of Bermuda. In this paper, we investigate what timbers from this Dockyard can tell us about interconnections and empire-building throughout the North Atlantic region. To do this we drew from approaches of critical physical geography, historical geography, and dendroprovenancing by using timber as a way to interrogate collaboratively the changes in—and connections across—socio-ecological landscapes. We examined HM Customs records between 1825 and 1850 to determine the flow of timbers to Bermuda. We then sampled timbers from buildings constructed between 1825 and 1853 and analyzed them using isotopic and dendrochronological techniques to establish the probable location of origin of the timber samples. HM Customs records showed that prior to the 1840s, timbers primarily came from British North America, whereas post-1840 timbers primarily came from the southeastern United States, with some still coming from Europe and British North America. To establish whether timber use by the Royal Navy and Royal Engineers matched the pattern in the customs documents, we looked to the dendrochronological records. Dendrochronologic evidence showed that military construction followed the same pattern, with buildings constructed pre-1840 using material from British North America and buildings constructed post-1840 using timbers sourced from the southeastern United States. Finally, using this information we explore some of the connections between regions, in terms of resource use, and the implications of those uses—for example, that the British Admiralty continued to benefit from the practices of slavery through the use of products produced from enslaved labour in other parts of the North Atlantic well after emancipation.  相似文献   

15.
16.
The study of tree rings has been used for over 100 years to inform climatic and geomorphological reconstructions. In mainland Australia, no tree species are currently recognised as providing reliable sources for such studies over extensive areas. Eucalyptus camaldulensis is a widely growing species with a growth pattern that is closely linked to high levels of available moisture, such as that associated with floods. The species therefore has the potential to provide palaeoclimatic information that may be of use in hydrological and geomorphological studies. This study initially examines the microstructure of samples of E. camaldulensis taken from the Barmah Forest to assess the applicability of the species to dendroecological investigation. It is found that samples of the species exhibit ring‐like structures, although there are areas of the samples that contain zones of growth without clear ring boundaries. The patterns of growth rings and zones are found to be common to many trees at a site, although the level of variability of pattern from tree to tree is high. Options for future development of the approach described here are to combine ring studies with isotopic‐based analysis to provide a combination of tree age and climatic history.  相似文献   

17.
The presented studies were carried out in order to check the usefulness of subfossil wood for stable isotope analysis. The aim of research was also to define the optimal method of subfossil samples preparation. Subfossil samples used during the presented studies are a part of the multicentury dendrochronological scale. This chronology originates in an area situated around a small mountain lake — Schwarzersee, in Austria. The obtained results of stable carbon isotope measurements confirmed that the method of α-cellulose extraction by the application of acidic sodium chlorite and sodium hydroxide solutions removes resins and other mobile compounds from wood. Therefore, in the case of the analysed samples, the additional chemical process of extractives removing was found to be unnecessary. Studied wood samples contained an adequate proportion of α-cellulose similar to the values characteristic for the contemporary trees. This proved an adequate wood preservation which is essential for the conduction of isotopic research.  相似文献   

18.
ABSTRACT

Cities can be considered as engines of the knowledge-based economy, because they are the primary sites of knowledge production activities that subsequently shape the rate and direction of technological change and economic growth. Patents provide rich information to analyse the knowledge specialization of specific places, such as technological details and information on inventors and entities involved. The technology codes attributed at the level of individual patent documents can be used to indicate the diversity and scope of the knowledge claims underlying a specific invention. In this study we introduce tools for portfolio analysis in terms of patents that provide insights into the technological specialization of cities. The mapping and analysis of patent portfolios of cities exploits data derived from the Unites States Patent and Trademark Office (USPTO) and dedicated tools (at https://leydesdorff.net/software/patents/). The results allow policy makers and other stakeholders to identify promising areas of further knowledge development, including smart specialization strategies.  相似文献   

19.
Vegetation structure and composition during the pre‐ and early‐European period in Australia is often proposed as a benchmark against which to measure the effects of modern landscape management practices. However, little quantifiable information exists for that historical period. One potential source of information is the land survey record, used in this study to provide estimates of tree densities that existed during the period 1870 to 1900 in part of central New South Wales. Estimates were obtained for 23 parishes in the north Lachlan River valley, between the towns of Condobolin and Tottenham. Densities were calculated from portion corner to nearest tree data obtained from historical survey plans, using the plotless, closest individual method. Densities ranged from 6.0 to 31.4 trees per hectare for parishes with enough data points for reliable calculation. These figures would account for trees of a diameter large enough to be blazed with a survey mark. Any smaller trees would be additional and, although no quantitative data existed for this, qualitative evidence suggested that the figures obtained were more likely to be underestimates due to the presence of such small trees. The study area was predominantly covered by woodlands which varied in density across the landscape, in comparison to the modern landscape where much of the native vegetation has been cleared for agriculture. Although the tree density figures should be considered to be indicative rather than precise, they provide quantifiable historical figures for past conditions in an area where the historical record is otherwise sparse. Such information is valuable for interpreting ecological changes brought about by modern land management.  相似文献   

20.
The paper deals with dendrochronological and radiocarbon dating of subfossil trunks found in the basin of the Morava River. The research into subfossil trunks had been conducted in the Czech Republic in the past but the research stopped in 2001. 160 records of measurements of subfossil, predominantly oak trunk samples, are preserved from that time. Three years ago the research was reopened and again the most trunks were found in the basin of the Morava River. 92 samples of oak trunks and 7 samples of other tree species (poplar, elm, maple, beech) were taken from selected sites. The samples were processed in compliance with the standard dendrochronological methodology. To date the samples, Czech, Austrian, Polish and German standard chronologies were used. In cases when the dendrochronological dating was unsuccessful, the samples were sent for radiocarbon dating. In total, 35 samples were dated, mainly by the radiocarbon method. Subfossil trunks from gravel pit Tovačov were dated and classified into 4 different periods, the oldest being from 2780–2190 BC. In Osek nad Bečvou, the samples were taken from two sites. Whereas from the 4 trunks taken in the river channel each was from a different period, the trunks from the gravel pit come from 981–1015 AD. The trunks found in the Morava River basin near Strážnice were dated to the 10th–15th century. In the future, we expect to extend the amount of the acquired samples with the aim to create a link to the existing standard chronology or to create a long floating average treering curve.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号