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.
This paper concerns research of a wooden well excavated at Jikidoin (dining hall complex) of Saidaiji temple located in Nara, the former 8th century capital of Japan. It is an example of interdisciplinary research including dendrochronology, archeology, architectural history, philology, and archaeobotany.The well is comprised of 20 hinoki cypress (Chamaecyparis obtusa Endl.) boards, dendrochronological analysis was conducted to determine how and when it was built. As a result, it was discovered that the timbers were processed from trees felled in 767 A.D. It was also determined from the carpentry marks that remained on the surface of the boards, that the lumber was obtained all at the same time.Plant seeds, wooden cooking tools and dishes, mokkan (wooden tablets), pottery, etc., were found buried inside the well. The discovery of cultivated plant seeds and wooden tools proved the site was part of Jikidoin. Based on the age of mokkan and pottery, it is presumed that the well ceased to be used around the end of the 8th century A.D.The investigation revealed much information concerning its specific construction and when the well was abandoned. The study is a rare example among excavations in Japan that reveals the usage of the well, especially the specific date of construction, period of use, and abandonment.  相似文献   

2.
The structure named Rebel’s Rest was a two-story, Reconstruction-era house located on the campus of the University of the South in Sewanee, Tennessee, before being severely damaged by fire in July 2014. The house was constructed of squared timbers and round logs, with later additions built using sawn lumber. Dendrochronological analyses of timbers and logs salvaged from the house reveals wood from four genera: oak (Quercus spp.), tulip poplar (Liriodendron tulipifera L.), American chestnut (Castanea dentata [Marshall] Borkh.), and pine (Pinus spp.). We statistically and graphically crossdated a total of 251 samples (24,410 rings) with regional chronologies from the ITRDB, resulting in three dated chronologies comprised of oak (1645–1874), tulip poplar (1725–1865), and American chestnut (1710–1864). The majority of samples with cutting dates (95.6%) ended in years 1865–1866, confirming the historically reported construction date of 1866 for the initial structure. The cutting date analysis also confirms two rooms as later additions, Room M (1867) and Room B (1875). Based on ring count and the number of chronologies produced, this research represents the largest known dataset from a single historic structure in the Southeastern US.  相似文献   

3.
灌木年轮学研究进展   总被引:5,自引:4,他引:1  
芦晓明  梁尔源 《生态学报》2013,33(5):1367-1374
灌木往往分布在树线以上或以北的高海拔和高纬度地区以及干旱、半干旱区,是把传统上以乔木为主的树轮研究扩展至森林分布界限以外的唯一选择.尽管灌木具有以上研究潜力,迄今用于树木年代学研究的灌木种类仅有30种左右.介绍了灌木年轮研究方法,综述了过去几十年来环北极高纬度地区,干旱、半干旱区以及高海拔地区的灌木年轮研究的主要进展.主要研究进展如下:(1)发掘一些灌木的树木年代学潜力;(2)揭示限制灌木生长的主要环境因子,并尝试利用灌木年轮宽度等指标重建过去区域气候变化历史;(3)探讨全球变暖的背景下,灌木的生长或分布范围的变化;(4)通过人为控制增温来揭示变暖对灌木生理特征和生长的影响.这些研究展示了灌木在扩展传统乔木树轮研究网络方面的潜力,也是树木年代学研究中最有前景的研究方向之一.目前的灌木年轮学研究多集中于环北极苔原带.作为地球的第三极,青藏高原具有广泛的高山灌木分布,具有把青藏高原边缘区以乔木为主的树木年轮网络扩展至更高海拔和高原内部的潜力.青藏高原高山灌木的年轮学研究并没有引起足够的重视.青藏高原高山灌木的生长是如何适应极端环境条件的,全球变暖的背景下,青藏高原高山灌木的分布和生长正在发生哪些变化等,都有待深入研究.  相似文献   

4.
The Deason House is located in the heart of the Piney Woods region in the town of Ellisville, Mississippi. During the American Civil War, the Deason House became the epicenter for an event that started a rebellion against the Confederate government. On 5 October 1863, a Confederate deserter named Newton Knight allegedly shot and killed Confederate Major Amos McLemore in the Deason House, which eventually lead to the formation of the Free State of Jones. Despite the historical importance of the house, oral accounts and written documents have failed to provide accurate construction history of the structure. We coupled techniques of dendrochronology and geophysical survey to better understand the construction history of the Deason House and cultural activities of its inhabitants. We extracted 35 Pinus palustris (Mill.) timbers along the west-facing exterior weatherboards and from various logs within the second-floor attic, 25 of which were successfully crossdated against a P. palustris reference chronology located 15 km south in De Soto National Forest (1742–2013). The Deason House chronology anchored against the De Soto time series during the period 1742–1875 (r = 0.55, t = 4.01, p < 0.0001) and extended the reference chronology back to the year 1680 CE. Clustering of cutting- and near-cutting dates from timbers revealed 3 possible stages of construction. First, the house likely existed as a single-pen structure built in the winter of 1835/1836, based on two timbers with wane/bark that were affixed to the original chimney made of clay bricks fired on the homestead. Second, based on the clustering of 1855 cutting dates, we suggest this was the most likely time the original structure was expanded with a vestibule, porch, and larger 4-room house. Finally, six timbers revealed a back addition was constructed in the year 1866. Ground penetrating radar (GPR) helped provide evidence mentioned in written records that the back addition (1866) existed as the detached kitchen then was affixed to the structure ca. 1890. The GPR data revealed geophysical anomalies that indicated the original sites of the detached kitchen, water well, livestock pen, privies, and trash pit. Through the use of dendrochronological analyses and geophysical survey, we were able to provide an updated history of the Deason House construction dynamics and cultural activities of its inhabitants beyond the historical record.  相似文献   

5.
Historical dendroarchaeology uses annual tree-ring widths varied by climate to crossdate structures of potential historical significance. In the Southeastern U.S. Piedmont specifically, crossdating these structures can lead to a broader historical interpretation during and after the colonial era. Our study used historical dendroarchaeology to date the Graves Mill grist mill located in Madison County along the western edge of the Virginia Piedmont. The mill and mill site reflect a regional trend in eighteenth century land use as agriculture transitioned from tobacco to wheat production in response to demand from international markets, as well as the adverse impact of tobacco cultivation on piedmont soils. Mills in this region have also been subject to flooding events from storms, with events recorded in the colonial era to a recent record flood in 1995, as well as re-building with changes in mill technologies through time. In an effort to date this structure as part of its restoration, and to verify the repeatability of this dating, ring widths from six timbers from the upper stories were analyzed independently at tree-ring laboratories at the University of Tennessee, Knoxville and Rider University. Both laboratories identified an 1816 cutting date for these samples, supporting documentary evidence that the mill likely underwent modifications over time after it was initially constructed in the eighteenth century. The consistent crossdating of these samples highlights the usefulness of dendrochronology as a research tool in the Southeastern U.S. for interpreting historical structures and their surrounding historical context.  相似文献   

6.
Aotearoa New Zealand has a rich cultural heritage but dating wooden objects using classic dendrochronology is challenging due to a paucity of master tree-ring width chronologies for species commonly identified in the archaeological record. This paper explores the potential for using a stable isotopic approach to dendrochronology for matai (Prumnopitys taxifolia (D.Don) Laub.). A total of six annual stable oxygen isotope (δ18O) series for matai growing in the Pureora Forest Reserve, were analysed and their oxygen isotopes found to exhibit a level of coherence that enabled cross-dating. A provisional chronology covering the period 1930–2018 CE was developed and tested against a sample of matai from the Kauaeranga Valley (200 km to the north of Pureora) and a sample of miro (Prumnopitys ferruginea (D.Don) Laub.). Miro is another species common in the cultural archive, but also difficult to date using ring-width dendrochronology. Both the Kaueranga matai and Pureora miro samples cross matched against the site chronology at the correct position, but with weaker dating statistics (Student’s t: 4.26 and 4.11 respectively) compared to the results obtained for two (non-2019) sampled Pureora matai analysed in this study (Student's t: 6.80 and 5.66). These results nevertheless demonstrate the presence of a regional-scale dating signal which may be developed for future use as a precision dating tool.  相似文献   

7.
The first European settlements accompanied by crop and livestock farming occurred approximately 7500 years ago. In this agrarian society, wood was one of the most important raw materials, most notably for construction, but only a little is known about wood use and woodworking technology. Hence, archaeological wooden finds are of particular importance. Dendroarchaeological studies combine the analysis of external and internal characteristics of archaeological wood: traces of tools on the wooden surfaces and the shape of timbers provide information about woodworking techniques, the tree rings allow dendrochronological dating and provide a paleoecological archive. In 2015 and 2016, two water wells with wooden linings from the Early Neolithic Period were discovered in the Czech Republic close to the towns of Velim (Bohemia) and Uničov (Moravia). The timbers were excellently preserved under waterlogged conditions. Here, we present a dendroarchaeological study including tree-ring and woodworking analyses. Furthermore, we consider former forest species composition. Overall, 15 lumbers from both wells were successfully dated by dendrochronology. The oaks used for the wells from Velim and Uničov were felled in 5196/5195 BCE and 5093–5085 BCE, respectively. Additionally, the taxa of 1859 wooden fragments, such as charcoals, branches and chips, were wood anatomically identified. The well lining from Velim with a hollowed tree trunk is already known from other Central European locations. In contrast, the construction from Uničov is unique for this period. Until now, the advanced construction design formed by four corner posts with longitudinal grooves and inserted horizontal planks was only known several thousands years later. The Early Neolithic wells from Uničov and Velim are the oldest archaeological discoveries of wooden artefacts in the Czech Republic that have been dendrochronologically dated. The tree-ring width series extend the Czech oak tree-ring width chronology more than 300 years into the past.  相似文献   

8.
Authenticity is the prime factor affecting the market value of a work of art. String instruments are among the most valued works of art, particularly those made by the old violin-making masters of northern Italy in the late 17th and early 18th centuries. However, it is difficult to verify the authenticity of string instruments on the basis of style and design alone, as these are often copied or forged. Uncertainties related to craftsmanship can lead to financial and legal controversy, sometimes with even millions of dollars at stake. The authenticity of the Stradivari “Messiah” has long been disputed. Controversies at the end of the 1990s concerning its craftsmanship have enhanced interest in dating this violin. After different dendrochronological analyses provided conflicting tree-ring dates for the front of the violin, a scientifically-sound dendrochronological study eventually established 1682 as terminus post quem, i.e., the year when the last ring of the violin front was formed, before which the violin could not have been made. This date is consistent with the attributed date of manufacture, 1716, supporting Antonio Stradivari as the maker of the “Messiah”. However, this controversial dating of the “Messiah” sent shockwaves through the violin community. Here, we present the main facts which played a role in this controversy and we show how dangerous the use of dendrochronology can be if investigators do not adhere to well-established techniques and are not versed scholars in the literature. Such controversies threaten the reputation of dendrochronology. Today, many false theories and conceptual mistakes continue to circulate in the violin community. A thorough and scientifically-sound dendrochronological analysis of the wood used to make the instrument is the only analysis that can objectively indicate, if not the exact year an instrument was made, at least the date before which it certainly was not made. Here, we describe the importance, in terms of acoustics, of the anatomical characteristics of the wood with which instruments are made and its possible geographical provenance. We review the dendrochronological studies undertaken to assess the authenticity of the instruments made by the old Italian masters. Such studies help to establish the earliest date the tree from which the wood was taken could have been felled, and to determine the source region of the wood. We present the main achievements and challenges that have arisen in the past 50 years of studying the authenticity of string instruments, and discuss the limitations and advantages of using dendrochronological methods to establish the provenance and time period in which a work of art was created. Finally, we describe needs of research in history, wood anatomy and dendrochronology, proposing several new methods that may open up new avenues of research and aid in the assessment of the authenticity of old string instruments.  相似文献   

9.
Charcoal piles have become a frequent subject of research in recent years as a better understanding of past human activities in forests is sought. The age of charcoal piles is usually determined by radiocarbon dating; dendrochronology is rarely used because of the small size of preserved charcoal remains and the insufficient number of visible tree rings. This paper presents the potential for dendrochronological and 14C method in research into charcoal piles. From 14 charcoal-burning sites in the Czech Republic, 214 pieces of charcoal were anatomically identified at the genus level and dendrochronologically analysed. Our results show that fir dominated in these charcoal remains, followed by oak, beech, spruce and pine. With an overall dendrochronological dating success of 24 %, fir charcoal was dated most often (65 %) with measurable tree rings ranging from 14 to 90. The oldest charcoals were dendrochronologically dated to summer 1682 CE; conversely, the youngest had end dates in the second half of the 19th century. The relatively poor dating success of oak charcoal very likely resulted from the use of branches for charcoal production rather than tree trunks. Based on an analysis of selected charcoal samples, we confirm that radiocarbon dating provided a very wide range of dates in the post-1650 CE period and the use of the wiggle-matching method was usually challenging because of short TRW series. Based on samples with preserved waney edges, we conclude that charcoal was more commonly made from wood felled in the summer than in the winter. Despite the relatively low level of success of dendrochronological dating, it seems more effective for dating charcoal than the 14C method, especially with samples from the last 350 years.  相似文献   

10.
This paper examines the effect of different levels of protection from predation on feral house mice. Mice were contained in eight 50×50 m outdoor enclosures. Enclosures allowed access to a suite of freeliving vertebrate predators from the surrounding area, including feral foxes, feral cats and Australian raptors. A 10–15% cover of small, felled cypress pine trees was added in strips to low grassland to increase habitat complexity. Mice were not protected from predation when compared with low grassland pens, possibly because predators were able to focus their hunting activity in the strips. However, when felled trees were covered with wire netting, hence providing higher quality refuge, mouse populations achieved higher densities than in low grassland pens. A predator exclusion treatment was used to confirm the refuge effect was due to a reduction in the impact of predation. Survival rates under the different treatments were generally consistent with population level responses, with mice having lower survival in low grassland pens than in high refuge pens. This is the first study with mammals that confirms the importance of refuges from predators for prey populations.  相似文献   

11.
A dendroarchaeological survey of a traditional Nuu-chah-nulth plank house at Kiix?in, the former capital of the Huu-ay-aht First Nations, on the west coast of Vancouver Island British Columbia, was undertaken in the summer of 2002. Standardized dendroarchaeological techniques were employed to collect and analyse increment core samples collected from the house known as Quaksweaqwul. Floating ring-width series were compared to a locally prepared Western redcedar (Thuja heterophylla) master tree-ring chronology (1511–2002 AD) to determine when the trees used to construct the house were felled. The findings of the survey indicate that Quaksweaqwul was built after the 1835 AD growth year. As the amount of perimeter wood loss due to weathering and preparation is difficult to ascertain, no precise felling or construction date can be presented.

The results of this survey provide insights into Huu-ay-aht First Nations history and offer direct evidence for the general state of preservation of individual house posts and beams at Kiix?in. Additionally, the successful dating of a traditional First Nations village using a dendroarchaeological approach highlights the potential this technique may hold for developing similar insights at other sites along Canada's Pacific Coast.  相似文献   


12.
Tectona grandis (teak) is an important commercial tree species that is widely used in tropical dendrochronology due to the formation of climate-sensitive annual growth rings. However, young trees growing in plantation conditions exhibit poor ring visibility during the first years of growth, limiting the dendrochronology application. In the present study, we use x-ray densitometry to determine the wood density profile between and within annual rings and at the sapwood-heartwood boundary in trees from fast-growth plantations. The resulting wood density profiles (WDP) can be categorized as uniform, stable growth, unstable growth, and false. The annual ring boundaries were indistinct in trees less than 8 years old. In mature trees, the annual ring boundaries are more defined. In relation to the sapwood-heartwood boundary, the WDP showed a decrease in the wood density; however, this decrease is influenced by the annual ring boundary when the two boundaries coincide. The identification of annual rings in trees growing in fast-growth plantations should be combined with X-ray densitometry and visual identification if wood density data are necessary for deriving other analysis, as climate change, from annual ring.  相似文献   

13.
树木年轮分析在全球变化研究中的应用   总被引:11,自引:2,他引:9  
树木年轮的宽度、密度、图像分析、同位素含量等都与气候因子温度、湿度以及大气成分的变化成复杂的相关关系。本文总结了树木年轮分析的几种主要研究方法以及在全球气候变化、大气污染以及重建大气CO2浓度中的应用,同时利用树木年轮分析对全球变化研究中存在的问题、争议等作了简要的探讨,并对未来全球变化中的年轮年代学研究的方向作了展望。  相似文献   

14.
Radiocarbon (14C) has been used to date carbon-rich objects in Earth science, archeology, and history since the 1940s. New methods, using spikes in 14C caused by solar proton events, can be used to annually date wood when crossdating is not possible, such as when sample size is low, samples are floating in time, or external disturbances lead to insecure dates. Here, we use a spike in radiocarbon during a solar energetic particle (SEP) event in 774/775 CE to confirm crossdating of a poorly-replicated King Billy pine (Athrotaxis selaginoides) chronology. Low sample depth between 1498 and 1523 CE (two trees) prevented confident dating of the early period of the chronology. Three core samples with strong correlation with the master chronology that likely included the 774/775 CE Miyake SEP event were identified for radiocarbon isotope analysis. We sectioned segments centered on the estimated 774/775 CE date and then isolated the holocellulose in each sample. Samples were sent to an accelerator mass spectrometry (AMS) for radiocarbon measurements. The AMS data confirmed the crossdating accuracy of the tree ring series and reinforces the applicability of this technique to anchor poorly dated tree ring series in time. In addition, we found sample processing with a microtome proved superior for holocellulose extractions and yielded more accurate 14C measurements. We recommend sampling with a microtome, processing at least three samples per year, and including sample masses greater than 100 ug C to confirm dating using radiocarbon spikes.  相似文献   

15.
A recent report by Mondino and Avalle (2009) was widely distributed that demonstrated a re-dating of the famous “Messiah” violin, a violin attributed to Antonio Stradivari with a label date of 1716. An outermost ring date of 1844 is instead suggested rather than dates in the 1680s reported in previous studies. Mondino and Avalle suggest that this outermost ring date supports the attribution of the violin to Jean-Baptiste Vuillaume, a prolific French instrument maker who was well known for his copies of famous instruments. The statistical techniques and exercises used by Mondino and Avalle, however, are problematic and do not support this revised outermost date for the “Messiah” violin. Raw measurement data with original trends are used in their statistical crossdating, properties previously shown to hinder precise crossdating. They then substantiate their re-dating with polynomial trend curves, which has ever been accepted practice in dendrochronology. Furthermore, the authors use re-scaled correlation coefficients and t-values which artificially inflate the strength of the relationship between tree-ring series that are being statistically crossdated. Using the exact same tree-ring data, but using accepted techniques in statistical crossdating (e.g., the removal of all low-frequency trends and autocorrelation), we could not verify the revised dating of the “Messiah” violin. We urge caution for those who intend to use the SynchroSearch software, book, and lesson plans developed and distributed by Mondino and Avalle. This study illustrates the adverse effects possible in dendrochronology when investigators do not adhere to accepted and time-tested techniques, and are not versed in the extensive literature that highlights issues commonly encountered in statistical crossdating.  相似文献   

16.
The dendrochronological potential of short-lived species has had varying degrees of success in the past. Where there has been a level of success with short sequenced assemblages, the focus has been on visual comparisons, based on the occurrence of signature rings. Of vital importance to alder’s ability to be cross-correlated is that it produces a significant amount of distinguishable signature rings. Between 2012 and 2013, a large artificial island (crannog) of medieval date was excavated at Drumclay, County Fermanagh, Northern Ireland, and revealed a site of significant longevity, dating from the 9th century AD to the Post-Medieval period. This excavation exposed a vast number of well-preserved waterlogged archaeological features, resulting in the retention of over 9,000 individual wood samples. Oak timbers were used scarcely in the construction of the crannog, with the dominant wood species identified during excavation being alder. While the oak timbers have proved successful in providing spot dates and indicating phases of activity, the full chronological potential of the wood assemblage lies in the ring patterns of the principal species, alder, particularly with respect to understanding construction phases and site evolution. Previous failures to build chronologies using alder have been attributed to the short-lived and site specific nature of the species. Here, we test whether the measurement of large numbers of samples from a single context within a single site overcomes the limitations posed by alder. We measured the ring-widths of 90 alder samples from archaeological features within the crannog’s infrastructure to test if a robust context chronology could be built. The average ring sequence length ranged from 30 to 60 rings, with one timber extending to 108 rings. Visual correlations were used to aid ring pattern matching in conjunction with statistical correlation. We used radiocarbon wiggle-matching to test the robustness of our constructed chronology and to anchor it to an absolute timescale. Our results to date show that problems of autocorrelation can arise when long alder sequences (>100 rings) are used in conjunction with short sequences (30 to 60 rings). Establishing a rigorous protocol for sample selection has enabled us to develop a more statistically refined methodology that has produced t-values as high as 8.3. We show that in order to construct the best possible alder chronology, multiple ring patterns need to be examined from each context. We recommend examining short-lived assemblages on their own merits; the best approach in these cases is not to look for the longest sequences but instead to focus on the those from the mean sequence range.  相似文献   

17.
《Dendrochronologia》2006,23(3):195-201
A dendroarchaeological survey of a traditional Nuu-chah-nulth plank house at Kiix?in, the former capital of the Huu-ay-aht First Nations, on the west coast of Vancouver Island British Columbia, was undertaken in the summer of 2002. Standardized dendroarchaeological techniques were employed to collect and analyse increment core samples collected from the house known as Quaksweaqwul. Floating ring-width series were compared to a locally prepared Western redcedar (Thuja heterophylla) master tree-ring chronology (1511–2002 AD) to determine when the trees used to construct the house were felled. The findings of the survey indicate that Quaksweaqwul was built after the 1835 AD growth year. As the amount of perimeter wood loss due to weathering and preparation is difficult to ascertain, no precise felling or construction date can be presented.The results of this survey provide insights into Huu-ay-aht First Nations history and offer direct evidence for the general state of preservation of individual house posts and beams at Kiix?in. Additionally, the successful dating of a traditional First Nations village using a dendroarchaeological approach highlights the potential this technique may hold for developing similar insights at other sites along Canada's Pacific Coast.  相似文献   

18.
基于树木年代学的理论和方法,建立了大兴安岭满归地区樟子松年轮宽度年表,分析了标准化年表与该区主要气候因子(温度和降水)之间的相关关系,揭示了气候因子对树木径向生长的影响.结果表明:当年4-8月的各月平均温度是研究区樟子松径向生长的主要限制因子;4-8月各月温度的不断升高对樟子松径向生长产生了不利影响.利用4-8月平均温度的变化模拟樟子松径向生长变异(1958 -2008年),发现随着区域气候暖干化趋势的加强,该区樟子松生长将呈现出衰退的特征.  相似文献   

19.
A detailed dendrochronological survey was performed on the medieval roofs of the Church of Our Lady (CoOL) in Damme, Belgium. Seen its complex architectural history, special attention was paid to the identification of consecutive building phases, based on combined architectural historical research and tree-ring dating. In total 64 increment cores were taken throughout the roof structures of the CoOL. All roof timbers are made of European oak (Quercus robur/petraea), of which only few have surviving sapwood or bark. Tree-ring dating confirms the late 13th/early 14th century construction date of the roofs. For all chronologies that were composed, the highest correlation values are found with reference chronologies covering the catchment area of the river Meuse. From the dating results of the timbers of the CoOL it becomes clear that the same timber source was used for nearly a century. On several of the examined roof timbers, rafting joints were observed, demonstrating that the timbers were indeed tied together as a raft and floated down the river.By implementing sapwood estimates in a Bayesian chronological model (OxCal), tree-ring series with surviving sapwood from coeval roof structures were combined in order to narrow down the time range for the felling date. Based on the refined interpretation of the felling dates, several consecutive building phases can now be identified and dated, leading to a new interpretation of the architectural history of the CoOL. Intriguingly, a marked interruption in building activities is observed around 1300. Probably this is related to the instable political situation at that time, caused by the armed conflict that emerged between the Count of Flanders and the king of France. Since Damme served as the outport of the riotous city of Bruges, it was alternately seized by the French and Flemish, both consuming considerable amounts of timber and other building materials for military fortifications. Potentially this led to a shortage in building materials and provoked a stop in building activities.This paper demonstrates the power of Bayesian models to refine the interpretation of dendrochronological dates in architectural analyses of medieval historical buildings.  相似文献   

20.
Dendrochronology is developing outside temperate and boreal regions. Over the past decade substantial progress has been made in Mediterranean and wet tropical regions. However, research in dry tropical regions, notably those of sub-Saharan Africa, has remained fragmentary. Here, we try to identify the unique challenges and opportunities of dendrochronology in the dry tropics. First, we briefly review the status of dendrochronology outside temperate and boreal regions with an emphasis on sub-Saharan Africa. Subsequently, we focus upon one of those areas where dendrochronology in the dry tropics is at the forefront of scientific advance: Ethiopia. A detailed review of tree ring studies in the lowlands and highlands highlights the complexity of ring formation and made us identify four major types of growth ring expression: anatomically not distinct rings, multiple rings per year, annual rings and multiple missing rings. This complex tree growth behaviour is associated with large-scale variations in precipitation regime (unimodal to multimodal) and relatively small-scale variations in tree sensitivity to water availability. Literature results are used to develop a scheme that can be used to predict differences in growth ring formation along gradients in these two factors. Because of the exceptional growth sensitivity of and the importance of local site conditions (topography, biological factors, etc.) for most trees sampled, those growing at the limits of their ecological amplitude are prone to possess multiple rings per year or multiple missing rings. In such circumstances, site selection should not always take place at the limits of the ecological amplitude of a species, but may sometimes have to be diverted to more mesic environments. Successful studies are now appearing, such as those reporting correlations between tree ring chronologies and Blue Nile river flows.  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