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JOCHEN SCHÖNGART BETTINA ORTHMANN† KLAUS JOSEF HENNENBERG† STEFAN POREMBSKI† MARTIN WORBES‡ 《Global Change Biology》2006,12(7):1139-1150
Most tropical regions are facing historical difficulties of generating biologically reconstructed long‐term climate records. Dendrochronology (tree‐ring studies) is a powerful tool to develop high‐resolution and exactly dated proxies for climate reconstruction. Owing to the seasonal variation in rainfall we expected the formation of annual tree rings in the wood of tropical West African tree species. In the central‐western part of Benin (upper Ouémé catchment, UOC) and in northeastern Ivory Coast (Comoé National Park, CNP) we investigated the relationship between climate (precipitation, sea surface temperature (SST)) and tree rings and show their potential for climate reconstruction. Wood samples of almost 200 trees belonging to six species in the UOC and CNP served to develop climate‐sensitive ring‐width chronologies using standard dendrochronological techniques. The relationship between local precipitation, monthly SST anomalies in the Gulf of Guinea, El Niño‐ Southern Oscillation (ENSO) and ring‐width indices was performed by simple regression analyses, two sample tests and cross‐spectral analysis. A low‐pass filter was used to highlight the decadal variability in rainfall of the UOC site. All tree species showed significant relationships with annual precipitation proving the existence of annual tree rings. ENSO signals could not be detected in the ring‐width patterns. For legume tree species at the UOC site significant relationships could be found between SST anomalies in the Gulf of Guinea indicating correlations at periods of 5.1–4.1 and 2.3 years. Our findings accurately show the relationship between tree growth, local precipitation and SST anomalies in the Gulf of Guinea possibly associated with worldwide SST patterns. A master chronology enabled the reconstruction of the annual precipitation in the UOC to the year 1840. Time series analysis suggest increasing arid conditions during the last 160 years which may have large impacts on the hydrological cycles and consequently on the ecosystem dynamics and the development of socio‐economic cultures and sectors in the Guinea‐Congolian/Sudanian region. 相似文献
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对大兴安岭北部樟子松树轮中的全木、综纤维素和α纤维素3种组分按早晚材分别测定稳定碳同位素(δ13C)值,分析比较早晚材两种材质的3种组分δ13C值差异,探讨其对气候环境变化的响应。结果表明:从组分来看,樟子松树轮综纤维素的δ13C指标更接近于α纤维素;从材质来看,樟子松树轮晚材不同组分的稳定碳同位素信号对气候环境变化响应的一致性和敏感程度要大于早材。樟子松树轮晚材的综纤维素δ13C指标是研究过去气候或环境变化的理想载体,而α纤维素在提取过程中很可能丢失了部分气候信息。 相似文献
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Christoph Nehrbass‐Ahles Flurin Babst Stefan Klesse Magdalena Nötzli Olivier Bouriaud Raphael Neukom Matthias Dobbertin David Frank 《Global Change Biology》2014,20(9):2867-2885
Tree‐rings offer one of the few possibilities to empirically quantify and reconstruct forest growth dynamics over years to millennia. Contemporaneously with the growing scientific community employing tree‐ring parameters, recent research has suggested that commonly applied sampling designs (i.e. how and which trees are selected for dendrochronological sampling) may introduce considerable biases in quantifications of forest responses to environmental change. To date, a systematic assessment of the consequences of sampling design on dendroecological and‐climatological conclusions has not yet been performed. Here, we investigate potential biases by sampling a large population of trees and replicating diverse sampling designs. This is achieved by retroactively subsetting the population and specifically testing for biases emerging for climate reconstruction, growth response to climate variability, long‐term growth trends, and quantification of forest productivity. We find that commonly applied sampling designs can impart systematic biases of varying magnitude to any type of tree‐ring‐based investigations, independent of the total number of samples considered. Quantifications of forest growth and productivity are particularly susceptible to biases, whereas growth responses to short‐term climate variability are less affected by the choice of sampling design. The world's most frequently applied sampling design, focusing on dominant trees only, can bias absolute growth rates by up to 459% and trends in excess of 200%. Our findings challenge paradigms, where a subset of samples is typically considered to be representative for the entire population. The only two sampling strategies meeting the requirements for all types of investigations are the (i) sampling of all individuals within a fixed area; and (ii) fully randomized selection of trees. This result advertises the consistent implementation of a widely applicable sampling design to simultaneously reduce uncertainties in tree‐ring‐based quantifications of forest growth and increase the comparability of datasets beyond individual studies, investigators, laboratories, and geographical boundaries. 相似文献
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Matthias Saurer Renato Spahni David C. Frank Fortunat Joos Markus Leuenberger Neil J. Loader Danny McCarroll Mary Gagen Ben Poulter Rolf T.W. Siegwolf Laia Andreu‐Hayles Tatjana Boettger Isabel Dorado Liñán Ian J. Fairchild Michael Friedrich Emilia Gutierrez Marika Haupt Emmi Hilasvuori Ingo Heinrich Gerd Helle Håkan Grudd Risto Jalkanen Tom Levanič Hans W. Linderholm Iain Robertson Eloni Sonninen Kerstin Treydte John S. Waterhouse Ewan J. Woodley Peter M. Wynn Giles H.F. Young 《Global Change Biology》2014,20(12):3700-3712
The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree‐ring sites located across Europe are investigated to determine the intrinsic water‐use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000. The results were compared with simulations of a dynamic vegetation model (LPX‐Bern 1.0) that integrates numerous ecosystem and land–atmosphere exchange processes in a theoretical framework. The spatial pattern of tree‐ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south‐to‐north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil‐water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase in iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation–climate feedbacks are currently still poorly constrained by observational data. 相似文献
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Christine R. Rollinson Yao Liu Ann Raiho David J. P. Moore Jason McLachlan Daniel A. Bishop Alex Dye Jaclyn H. Matthes Amy Hessl Thomas Hickler Neil Pederson Benjamin Poulter Tristan Quaife Kevin Schaefer Jörg Steinkamp Michael C. Dietze 《Global Change Biology》2017,23(7):2755-2767
Ecosystem models show divergent responses of the terrestrial carbon cycle to global change over the next century. Individual model evaluation and multimodel comparisons with data have largely focused on individual processes at subannual to decadal scales. Thus far, data‐based evaluations of emergent ecosystem responses to climate and CO2 at multidecadal and centennial timescales have been rare. We compared the sensitivity of net primary productivity (NPP) to temperature, precipitation, and CO2 in ten ecosystem models with the sensitivities found in tree‐ring reconstructions of NPP and raw ring‐width series at six temperate forest sites. These model‐data comparisons were evaluated at three temporal extents to determine whether the rapid, directional changes in temperature and CO2 in the recent past skew our observed responses to multiple drivers of change. All models tested here were more sensitive to low growing season precipitation than tree‐ring NPP and ring widths in the past 30 years, although some model precipitation responses were more consistent with tree rings when evaluated over a full century. Similarly, all models had negative or no response to warm‐growing season temperatures, while tree‐ring data showed consistently positive effects of temperature. Although precipitation responses were least consistent among models, differences among models to CO2 drive divergence and ensemble uncertainty in relative change in NPP over the past century. Changes in forest composition within models had no effect on climate or CO2 sensitivity. Fire in model simulations reduced model sensitivity to climate and CO2, but only over the course of multiple centuries. Formal evaluation of emergent model behavior at multidecadal and multicentennial timescales is essential to reconciling model projections with observed ecosystem responses to past climate change. Future evaluation should focus on improved representation of disturbance and biomass change as well as the feedbacks with moisture balance and CO2 in individual models. 相似文献
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The availability of exactly dated tree‐ring chronologies is limited in tropical regions. However, these chronologies could contribute widely to studies of the influence of natural and human‐induced factors on tropical forests. We examine the potential for building a chronology based on three sites in the miombo woodland of western Zambia. Brachystegia spiciformis Benth., a dominant species from this vegetation type, is used. Response of the chronology to several climatic factors is examined. All specimens showed very clear growth rings, and cross‐dating between radii of a tree was successful for all trees. Site chronologies could be constructed after cross‐dating of growth ring series of individual trees. The mean growth ring curves of the three sites were significantly similar, allowing for the construction of a regional chronology. Correlation function analysis between the tree‐ring chronology and regional climatic variables revealed that climate at the core of the rainy season, in December and January, has an explicit influence on tree growth. Where precipitation and relative humidity in these months influence tree growth positively, temperature correlates in a negative way. Some 20 percent of the variance in the B. spiciformis tree‐ring chronology is accounted for by wet season rainfall. The successful cross‐dating and correlation between a tree‐ring chronology and climate demonstrated in this study indicate annual ring formation in B. spiciformis trees and sensitivity to climatic conditions. 相似文献
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Short records of naturally fluctuating Pacific salmon (Oncorhynchus spp.) populations elicit challenges for the long‐term management of North American fisheries. A dendrochronologic approach was used to reconstruct long proxy histories of regional Pacific salmon populations returning to streams along west central British Columbia coastlines. Tree rings from five tree species collected at 18 sites were found to be sensitive to interannual fluctuations in large‐scale ocean and atmospheric circulation patterns. Using a regional network of climate‐sensitive ring‐width and ring‐density tree‐ring chronologies in linear regression models, multi‐century long‐term abundance records for populations of sockeye, chinook, chum and pink salmon were generated. Models explained between 27% and 39% of the variability in escapement records and were more proficient at capturing trends than annual magnitudes. The reconstructions vary in length, dating from 1400, 1536 and 1638 ad and extending to 2009 ad . Notable fluctuations in salmon abundance over the past six centuries are described, with significant population collapses shown to occur during the early 1400s, the late 1500s, the mid‐1600s, the early 1700s, the early 1800s and parts of the 1900s. These models are the first to utilize climate‐sensitive tree‐ring records to reconstruct regional abundance histories and thus contribute potentially valuable information for salmon fisheries managers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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树木生长受到气候因子、随年龄增长的内在生长趋势、环境干扰和其他扰动信号的影响。目前存在不同的去趋势方法对树木年轮进行去趋势以识别树木生长中的气候信号。以往的研究多基于单个方法识别树轮气候信号,而不同去趋势方法识别的树轮气候信号可能会有一定的差别。为了对比不同去趋势方法对树轮气候信号识别的影响,我们基于国际年轮数据库网站获取中国西部地区68个点的树轮宽度数据,采用最常用的\"signal-free\"方法（SsfCrn）、线性和负指数函数法（std）、67%样条函数法（spline）、firedman方法、以及基于经验模式分解去趋势方法（EEMD）5种去趋势方法分别建立树轮年表,并对比分析同一地点的不同年表对气候响应的异同。结果表明：不同去趋势方法得到的年表对温度、降水以及相对湿度等气候因素的响应具有明显差异。其中,SsfCrn去趋势方法建立的年表对温度（月平均温、月最低温、月平均最低温）响应中相关最高的样点在所有样点中占比最高;EEMD去趋势方法建立的年表对降水量、相对湿度和月最高温响应中相关最高的样点在所有样点中占比最高;firedman去趋势方法建立的年表对月平均最高温响应中相关最高的样点在所有样点中占比最高。研究结果表明SsfCrn,EEMD和firedman方法在识别树轮气候信号方法具有一定的优势。在不同研究区域中,不同去趋势方法建立的年表对不同气候条件响应有差异,因此选择不同的去趋势方法识别树木生长趋势,分析哪种方法可以更好的反应气候变化对树木生长的影响显得尤为重要。 相似文献
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CHRISTOPHER T. COLE JON E. ANDERSON RICHARD L. LINDROTH DONALD M. WALLER 《Global Change Biology》2010,16(8):2186-2197
As atmospheric CO2 levels rise, temperate and boreal forests in the Northern Hemisphere are gaining importance as carbon sinks. Quantification of that role, however, has been difficult due to the confounding effects of climate change. Recent large‐scale experiments with quaking aspen (Populus tremuloides), a dominant species in many northern forest ecosystems, indicate that elevated CO2 levels can enhance net primary production. Field studies also reveal that droughts contribute to extensive aspen mortality. To complement this work, we analyzed how the growth of wild aspen clones in Wisconsin has responded to historical shifts in CO2 and climate, accounting for age, genotype (microsatellite heterozygosity), and other factors. Aspen growth has increased an average of 53% over the past five decades, primarily in response to the 19.2% rise in ambient CO2 levels. CO2‐induced growth is particularly enhanced during periods of high moisture availability. The analysis accounts for the highly nonlinear changes in growth rate with age, and is unaffected by sex or location sampled. Growth also increases with individual heterozygosity, but this heterozygote advantage has not changed with rising levels of CO2 or moisture. Thus, increases in future growth predicted from previous large‐scale, common‐garden work are already evident in this abundant and ecologically important tree species. Owing to aspen's role as a foundation species in many North American forest ecosystems, CO2‐stimulated growth is likely to have repercussions for numerous associated species and ecosystem processes. 相似文献
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Brian J. McGill 《Journal of Plant Ecology》2012,5(1):46
Aims A common assumption in ecology is that where a species is found to be most abundant must correspond to the environmental context in which the species performs the best (i.e. optimal niche space). This assumption is central to common conservation and management tools such as habitat suitability assessment and species distribution modeling. I test this hypothesis.Methods I use the US Forest Inventory Assessment data for the abundance of trees across eastern North America. I use the FORAST tree-ring dataset for ontogenetic growth rate (tree-ring increment), a measure of niche performance and correlated with intrinsic rate of increase, r .Important findings I find that across 15 species, there are significantly more negative correlations than expected by chance. This negative correlation between abundance and performance across space contradicts common assumptions but is consistent with an inclusive niche structuring of the community. 相似文献
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Two fundamental axes – space and time – shape ecological systems. Over the last 30 years spatial ecology has developed as an integrative, multidisciplinary science that has improved our understanding of the ecological consequences of habitat fragmentation and loss. We argue that accelerating climate change – the effective manipulation of time by humans – has generated a current need to build an equivalent framework for temporal ecology. Climate change has at once pressed ecologists to understand and predict ecological dynamics in non‐stationary environments, while also challenged fundamental assumptions of many concepts, models and approaches. However, similarities between space and time, especially related issues of scaling, provide an outline for improving ecological models and forecasting of temporal dynamics, while the unique attributes of time, particularly its emphasis on events and its singular direction, highlight where new approaches are needed. We emphasise how a renewed, interdisciplinary focus on time would coalesce related concepts, help develop new theories and methods and guide further data collection. The next challenge will be to unite predictive frameworks from spatial and temporal ecology to build robust forecasts of when and where environmental change will pose the largest threats to species and ecosystems, as well as identifying the best opportunities for conservation. 相似文献
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Andrés Holz Sarah J. Hart Grant J. Williamson Thomas T. Veblen Juan C. Aravena 《Journal of Biogeography》2018,45(5):1140-1152
Aim
We examined whether and how tree radial‐growth responses to climate have changed for the world's southernmost conifer species throughout its latitudinal distribution following rapid climate change in the second half of the 20th century.Location
Temperate forests in southern South America.Methods
New and existing tree‐ring radial growth chronologies representing the entire latitudinal range of Pilgerodendron uviferum were grouped according to latitude and then examined for differences in growth trends and non‐stationarity in growth responses to a drought severity index (scPDSI) over the 1900–1993 AD period and also before and after significant shifts in climate in the 1950s and 1970s.Results
The radial‐growth response of P. uviferum climate was highly variable across its full latitudinal distribution. There was a long‐term and positive association between radial growth and higher moisture at the northern and southern edges of the distribution of this species and the opposite relationship for the core of its distribution, especially following the climatic shifts of the 1950s and 1970s. In addition, non‐stationarity in moisture‐radial growth relationships was observed in all three latitudinal groups (southern and northern edges and core) for all seasons during the 20th century.Main conclusions
Climate shifts in southern South America in the 1950s and 1970s resulted in different responses in the mean radial growth of P. uviferum at the southern and northern edges and at the core of its range. Dendroclimatic analyses document that during the first half of the 20th century climate‐growth relationships were relatively similar between the southern and northern range edges but diverged after the 1950s. Our findings imply that simulated projections of climate impacts on tree growth, and by implication on forest ecosystem productivity, derived from models of past climate‐growth relationships need to carefully consider different and non‐stationarity responses along the wide latitudinal distribution of this species. 相似文献17.
Romano Foti Manuel del Jesus Andrea Rinaldo Fernando R. Miralles‐Wilhelm Ignacio Rodriguez‐Iturbe 《Ecohydrology》2015,8(2):204-213
In the context of climatic uncertainty and potential climatic change, incorporating climatic variability and change in eco‐hydrological analysis, as well as understanding the impact of such variability on ecosystems, is of crucial importance. The latter is particularly true for those complex ecosystems, such as wetlands, which cradle large varieties of species, many of which rare or endangered. Focusing on the Everglades wetlands, we investigate the presence of non‐stationary elements in the seasonal cycle of precipitation, temperature and stage level and examine their correlation and potential impact on the ecosystem's flora and fauna. To this aim, we revisit demodulation techniques and demonstrate their validity for the diagnosis of long‐term trends in the amplitude and phase of seasonal patterns of hydrologic series. We then analyse historical records of fauna and flora components of the Everglades in order to reveal potential relationships with hydrological trends. We observe that the seasonal patterns of all the time series analysed are non‐stationary. In addition, we observe that the amplitude of seasonal oscillations of all hydro‐climatic drivers is strongly correlated with anomalies in records of wading birds population and plant carbon assimilation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Per E. Bodin Mary Gagen Danny McCarroll Neil J. Loader Risto Jalkanen Iain Robertson Vincent R Switsur John S. Waterhouse Ewan J. Woodley Giles H. F. Young Paul B. Alton 《Global Change Biology》2013,19(6):1709-1719
Accurate modelling of long‐term changes in plant stomatal functioning is vital to global climate change studies because changes in evapotranspiration influence temperature via physiological forcing of the climate. Various stomatal models are included in land surface schemes, but their robustness over longer timescales is difficult to validate. We compare the performance of three stomatal models, varying in their degree of complexity, and coupled to a land surface model. This is carried out by simulating the carbon isotope ratio of tree leaves (δ13Cleaf) over a period of 53 years, and comparing the results with carbon isotope ratios obtained from tree rings (δ13Cstem) measured at six sites in northern Europe. All three stomatal models fail to capture the observed interannual variability in the measured δ13Cstem time series. However, the Soil‐Plant‐Atmosphere (SPA) model performs significantly better than the Ball‐Berry (BB) or COX models when tested for goodness‐of‐fit against measured δ13Cstem. The δ13Cleaf time series simulated using the SPA model are significantly positively correlated (P < 0.05) with measured results over the full time period tested, at all six sites. The SPA model underestimates interannual variability measured in δ13Cstem, but is no worse than the BB model and significantly better than the COX model. The inability of current models to adequately replicate changes in stomatal response to rising levels of CO2 concentrations, and thus to quantify the associated physiological forcing, warrants further investigation. 相似文献
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Natural influences as well as human activities have changed forest environments. As a result, growth conditions have changed with time. The annual and periodic growth of needles, shoots, tree rings and volume growth vary considerably over time. The variation in ring width and volume increment of Norway spruce correlates with precipitation and air temperature. High air temperature and low precipitation during the vegetation period reduce growth rate and increase tree mortality even in some areas where average precipitation is high and average air temperature is relatively low. 相似文献
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Oleksandra Hararuk Elizabeth M. Campbell Joseph A. Antos Roberta Parish 《Global Change Biology》2019,25(4):1222-1234
Atmospheric CO2 concentrations are now 1.7 times higher than the preindustrial values. Although photosynthetic rates are hypothesized to increase in response to rising atmospheric CO2 concentrations, results from in situ experiments are inconsistent in supporting a CO2 fertilization effect of tree growth. Tree‐ring data provide a historical record of tree‐level productivity that can be used to evaluate long‐term responses of tree growth. We use tree‐ring data from old‐growth, subalpine forests of western Canada that have not had a stand‐replacing disturbance for hundreds of years to determine if growth has increased over 19th and 20th centuries. Our sample consisted of 5,858 trees belonging to five species distributed over two sites in the coastal zone and two in the continental climate of the interior. We calculated annual increments in tree basal area, adjusted these increments for tree size and age, and tested whether there was a detectable temporal trend in tree growth over the 19th and 20th centuries. We found a similar pattern in 20th century growth trends among all species at all sites. Growth during the 19th century was mostly stable or increasing, with the exception of one of the coastal sites, where tree growth was slightly decreasing; whereas growth during the 20th century consistently decreased. The unexpected decrease in growth during the 20th century indicates that there was no CO2 fertilization effect on photosynthesis. We compared the growth trends from our four sites to the trends simulated by seven Earth System Models, and saw that most of the models did not predict these growth declines. Overall, our results indicate that these old‐growth forests are unlikely to increase their carbon storage capacity in response to rising atmospheric CO2, and thus are unlikely to contribute substantially to offsetting future carbon emissions. 相似文献