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1.
研究人工林径向生长与气候变化的关系对全球气候变暖背景下人工林合理经营有着重要的意义。该文对在辽东山区广泛栽培的黄花落叶松(Larix olgensis)和日本落叶松(Larix kaempferi)人工林, 运用树木年轮气候学方法建立了辽宁草河口和湾甸子林场落叶松人工林年表, 分析了落叶松径向生长对气候变化的响应以及气候条件、树种、立地条件和林分因子(林龄、密度、蓄积量等)的相对影响程度。结果发现在影响年轮-气候关系的因素中, 气象因子的潜在蒸发散(PET)的影响力最大; 林龄、密度和蓄积量同时也具有重要的影响作用。中龄落叶松人工林径向生长主要与气温呈正相关关系, 成熟落叶松人工林径向生长主要与气温呈负相关关系; 而其他因素, 如树种、立地条件等的影响作用不大。这表明在气候变暖背景下随着林龄增加, 林分会逐渐受到气温升高导致的水分亏缺的限制, 导致明显的生长下降趋势, 因而气候变暖对成熟落叶松人工林威胁更为严重, 所以要注重对成熟林的优先保护, 同时可以预测, 随着东北地区今后气候进一步变暖, 可能将逐步影响到林龄更小的林分的生长, 因此需要进一步研究如何在落叶松人工林经营中采取科学的措施来更好地应对未来气候变化。  相似文献   

2.
Climate warming and increasing aridity have impacted diverse ecosystems in the Mediterranean region since at least the 1970s. Pinus pinea L. has significant environmental and socio-economic importance for the Iberian Peninsula, so a detailed understanding of its response to climate change is necessary to predict its status under future climatic conditions. However, variability of climate and uncertainties in dendroclimatological approach complicate the understanding of forest growth dynamics. We use an ensemble approach to analyze growth-climate responses of P. pinea trees from five sites along a latitudinal gradient in Spain over time. The growth responses to April-June precipitation totals were stronger in the north than in the south. Since the 1950s, the sensitivity of growth to April-June precipitation increased in the north and decreased in the south. Meteorological drought usually started in May in the southern sites, but in June-July in the northern sites. The water deficit in the southern sites is thus greater and more limiting for tree growth, and this likely accounts for the lower growth sensitivity during these months. Our results indicate that P. pinea has a high degree of plasticity, suggesting the species will withstand changing climatic conditions. However, growth response to drought regimes varies among P. pinea populations, suggesting that different populations have different capacities for acclimation to warmer and drier climate, and this may influence future vegetation composition.  相似文献   

3.
Reports of forest sensitivity to climate change are based largely on the study of overstory trees, which contribute significantly to forest growth and wood supply. However, juveniles in the understory are also critical to predict future forest dynamics and demographics, but their sensitivity to climate remains less known. In this study, we applied boosted regression tree analysis to compare the sensitivity of understory and overstory trees for the 10 most common tree species in eastern North America using growth information from an unprecedented network of nearly 1.5 million tree records from 20,174 widely distributed, permanent sample plots across Canada and the United States. Fitted models were then used to project the near-term (2041–2070) growth for each canopy and tree species. We observed an overall positive effect of warming on tree growth for both canopies and most species, leading to an average of 7.8%–12.2% projected growth gains with climate change under RCP 4.5 and 8.5. The magnitude of these gains peaked in colder, northern areas for both canopies, while growth declines are projected for overstory trees in warmer, southern regions. Relative to overstory trees, understory tree growth was less positively affected by warming in northern regions, while displaying more positive responses in southern areas, likely driven by the buffering effect of the canopy from warming and climate extremes. Observed differences in climatic sensitivity between canopy positions underscore the importance of accounting for differential growth responses to climate between forest strata in future studies to improve ecological forecasts. Furthermore, latitudinal variation in the differential sensitivity of forest strata to climate reported here may help refine our comprehension of species range shift and changes in suitable habitat under climate change.  相似文献   

4.
Temperature and its impact on fitness are fundamental for understanding range shifts and population dynamics under climate change. Geographic climate heterogeneity, behavioral and physiological plasticity, and thermal adaptation to local climates make predicting the responses of species to climate change complex. Using larvae from seven geographically distinct wild populations in the eastern United States of the non‐native forest pest Lymantria dispar dispar (L.), we conducted a simulated reciprocal transplant experiment in environmental chambers using six custom temperature regimes representing contemporary conditions near the southern and northern extremes of the US invasion front and projections under two climate change scenarios for the year 2050. Larval growth and development rates increased with climate warming compared with current thermal regimes and tended to be greater for individuals originally sourced from southern rather than northern populations. Although increases in growth and development rates with warming varied somewhat by region of the source population, there was not strong evidence of local adaptation, southern populations tended to outperform those from northern populations in all thermal regimes. Our study demonstrates the utility of simulating thermal regimes under climate change in environmental chambers and emphasizes how the impacts from future increases in temperature can vary based on geographic differences in climate‐related performance among populations.  相似文献   

5.
Altitudinal difference increases the complexity of the response of tree growth to climate change in the mountainous areas, and may change the carbon sequestration capacity of forests under the ongoing warming climate. In this work, four tree-ring width chronologies from Pinus henryi Mast. growing at different altitudes of Shiyan, the northern subtropical China were developed. Results of Pearson correlation analysis, factor analysis and redundancy analysis indicate that tree growth-climate response models can be divided into two types according to the altitudinal gradient: the high-altitude model, represented by SWDH and WDSH above 1330 m a.s.l., and the low-altitude model, represented by WDSL and DDZL less than 1070 m a.s.l. The biggest difference between the two models is that tree growth at the low altitudes shows significantly negative response to temperature in the previous September–December and current April–May, and positive response to moisture conditions from the previous September to current May, April–May in particular; while the high-altitude ones show consistently positive responses to temperature in current February–April, but no significant response to seasonal moisture condition. The existence of a temperature-related altitudinal threshold between 1070 m a.s.l. to 1330 m a.s.l. may change the hydro-thermal combination models above and below the threshold, thus lead to the change of climatic response models along altitude gradient. 30-yr moving correlation analysis reveals that the relationships between tree growth and the limiting climatic factors present evident altitudinal difference: gradually strengthened at the high altitudes but weakened at the low altitudes. It is distinct that water availability and demand are critical for the growth of low-altitude trees, and high-altitude trees show a stronger positive response to climate warming, therefore could be an important carbon sink in the future. In addition, future forest management should focus on the low altitudes and formulate effective protection strategies.  相似文献   

6.
To address the central question of how climate change influences tree growth within the context of global warming, we used dendroclimatological analysis to understand the reactions of four major boreal tree species –Populus tremuloides, Betula papyrifera, Picea mariana, and Pinus banksiana– to climatic variations along a broad latitudinal gradient from 46 to 54°N in the eastern Canadian boreal forest. Tree‐ring chronologies from 34 forested stands distributed at a 1° interval were built, transformed into principal components (PCs), and analyzed through bootstrapped correlation analysis over the period 1950–2003 to identify climate factors limiting the radial growth and the detailed radial growth–climate association along the gradient. All species taken together, previous summer temperature (negative influences), and current January and March–April temperatures (positive influences) showed the most consistent relationships with radial growth across the gradient. Combined with the identified species/site‐specific climate factors, our study suggested that moisture conditions during the year before radial growth played a dominant role in positively regulating P. tremuloides growth, whereas January temperature and growing season moisture conditions positively impacted growth of B. papyrifera. Both P. mariana and P. banksiana were positively affected by the current‐year winter and spring or whole growing season temperatures over the entire range of our corridor. Owing to the impacts of different climate factors on growth, these boreal species showed inconsistent responsiveness to recent warming at the transition zone, where B. papyrifera, P. mariana, and P. banksiana would be the most responsive species, whereas P. tremuloides might be the least. Under continued warming, B. papyrifera stands located north of 49°N, P. tremuloides at northern latitudes, and P. mariana and P. banksiana stands located north of 47°N might benefit from warming winter and spring temperatures to enhance their radial growth in the coming decades, whereas other southern stands might be decreasing in radial growth.  相似文献   

7.
Changes in climate could have far-reaching consequences for ecosystems sensitive to changes in temperature and precipitation, such as boreal permafrost peatlands and grassland/woodland boundaries. The long-term data from our studies in these ecosystems suggest that transient responses of permafrost and vegetation to climate change may be difficult to predict due to lags and positive feedbacks related to vegetation and disturbance. Boreal permafrost peatlands comprise an ecosystem with strong local controls on microclimate that influence the formation and thaw of permafrost. These local controls may preserve permafrost during the transient stages of climate warming, producing lagged responses. The prairie–forest border region of the northern Great Plains has experienced frequent change and has complex dynamics involving transitions in the grassland composition of prairie and in the degree of woodiness in bordering forests. Fire frequency interacts with fuel loading and tree recruitment in ways that affect the timing and direction of change. Lags and thresholds could lead to sudden large responses to future climate change that are not readily apparent from current vegetation. The creation of adequate models to characterize transient ecosystem changes will require an understanding of the linkages among processes operating at the scale of 10s of meters and over long time periods. Received 14 December 1999; accepted 7 July 2000.  相似文献   

8.
Reduction in body size is a major response to climate change, yet evidence in globally imperiled amphibians is lacking. Shifts in average population body size could indicate either plasticity in the growth response to changing climates through changes in allocation and energetics, or through selection for decreased size where energy is limiting. We compared historic and contemporary size measurements in 15 Plethodon species from 102 populations (9450 individuals) and found that six species exhibited significant reductions in body size over 55 years. Biophysical models, accounting for actual changes in moisture and air temperature over that period, showed a 7.1–7.9% increase in metabolic expenditure at three latitudes but showed no change in annual duration of activity. Reduced size was greatest at southern latitudes in regions experiencing the greatest drying and warming. Our results are consistent with a plastic response of body size to climate change through reductions in body size as mediated through increased metabolism. These rapid reductions in body size over the past few decades have significance for the susceptibility of amphibians to environmental change, and relevance for whether adaptation can keep pace with climate change in the future.  相似文献   

9.
Global warming affects breeding phenology of birds differentially with latitude, but there is contrasting evidence about how the changing climate influences the breeding of migrating songbirds at their northern breeding range. We investigate the effect of climate warming on breeding time and breeding success of European pied flycatchers Ficedula hypoleuca in Sweden during a period of 36 years using nest reports from bird ringing. To account for the latitudinal variation, we divided Sweden into three latitudinal bands (northern, intermediate, and southern). We applied a sliding window approach to find the most influential period and environment characteristics (temperature, vegetation greenness, and precipitation), using linear mixed models and model averaging. Our results show a long‐term advancement of breeding time related to increasing spring temperature and vegetation greenness during a period before hatching. Northern breeders revealed a larger advancement over the years (8.3 days) compared with southern breeders (3.6 days). We observed a relatively stronger effect of temperature and greenness on breeding time in the north. Furthermore, northern birds showed an increase in breeding success over time, while birds breeding at southern and intermediate latitudes showed reduced breeding success in years with higher prehatching temperatures. Our findings with stronger environment effects on breeding time advancement in the north suggest that pied flycatchers are more responsive to weather cues at higher latitudes. Breeding time adjustment and, potentially, low competition help explain the higher long‐term success observed in the north. Reduced breeding success at more southerly latitudes suggests an inability to match breeding time to very early and warm springs, a fate that with continued climate change could also be expected for pied flycatchers and other long‐distance migrants at their very northern breeding range.  相似文献   

10.
Complex non-linear relationships exist between air and soil temperature responses to climate change. Despite its influence on hydrological and biogeochemical processes, soil temperature has received less attention in climate impact studies. Here we present and apply an empirical soil temperature model to four forest sites along a climatic gradient of Sweden. Future air and soil temperature were projected using an ensemble of regional climate models. Annual average air and soil temperatures were projected to increase, but complex dynamics were projected on a seasonal scale. Future changes in winter soil temperature were strongly dependent on projected snow cover. At the northernmost site, winter soil temperatures changed very little due to insulating effects of snow cover but southern sites with little or no snow cover showed the largest projected winter soil warming. Projected soil warming was greatest in the spring (up to 4°C) in the north, suggesting earlier snowmelt, extension of growing season length and possible northward shifts in the boreal biome. This showed that the projected effects of climate change on soil temperature in snow dominated regions are complex and general assumptions of future soil temperature responses to climate change based on air temperature alone are inadequate and should be avoided in boreal regions.  相似文献   

11.
Current methods of assessing climate-induced shifts of species distributions rarely account for species interactions and usually ignore potential differences in response times of interacting taxa to climate change. Here, we used species-richness data from 1005 breeding bird and 1417 woody plant species in Kenya and employed model-averaged coefficients from regression models and median climatic forecasts assembled across 15 climate-change scenarios to predict bird species richness under climate change. Forecasts assuming an instantaneous response of woody plants and birds to climate change suggested increases in future bird species richness across most of Kenya whereas forecasts assuming strongly lagged woody plant responses to climate change indicated a reversed trend, i.e. reduced bird species richness. Uncertainties in predictions of future bird species richness were geographically structured, mainly owing to uncertainties in projected precipitation changes. We conclude that assessments of future species responses to climate change are very sensitive to current uncertainties in regional climate-change projections, and to the inclusion or not of time-lagged interacting taxa. We expect even stronger effects for more specialized plant–animal associations. Given the slow response time of woody plant distributions to climate change, current estimates of future biodiversity of many animal taxa may be both biased and too optimistic.  相似文献   

12.
Under climate change, modifications on plants’ growth are expected to be the strongest at species margins. Therein, tree acclimation could play a key role as migration is predicted to be too slow to track shifts of bioclimatic envelops. A requirement is, however, that intra-population genetic diversity be high enough for allowing such adaptation of tree populations to climate change. In this study, we tested for the existence of relationships between genetic diversity, site environmental conditions, and the response of annual tree growth to climate of Pinus cembra at its southern limit in the Alps. Site-specific climatic and environmental factors predominantly determined the response of trees along the precipitation gradient. The growth-climate interactions were chiefly linked to mean annual precipitation and temperature, slope and tree-size, and less to genetic diversity. We show that genetic background of Pinus cembra has exclusively indirect modulating power with limited effects on tree-ring formation, and within the southern limit in the Alps, genetic variability is not necessarily well expressed in the patterns of annual tree growth. Our results may imply little adaptive capacity of these populations to future changes in the water balance.  相似文献   

13.
伊春地区红松和红皮云杉径向生长对气候变化的响应   总被引:1,自引:0,他引:1  
树木生长-气候关系对准确评估气候变化对森林生态系统影响、预测森林生产力与植被动态及揭示树木对气候变化的响适应策略至关重要。在全球变暖背景下,升温可能会对树木的生长产生影响,从而改变区域森林生态系统的生产力或碳储量。本研究利用生长-气候响应函数、滑动相关分析等树木年轮学方法,探讨伊春地区阔叶红松林内红松和红皮云杉径向生长的主要限制因子及两者径向生长对快速升温(1980年后)响应的异同。结果表明:1980年前红松径向生长有明显加速的趋势,红皮云杉上升趋势较弱;而1980年后红松径向生长趋势显著下降,红皮云杉则下降不明显。红皮云杉径向生长与上一年9月及当年6月平均气温显著负相关,而红松径向生长与上一年12月及当年1月、4月和6月最低气温显著正相关。1980年快速升温后,高温对两树种生长的抑制作用增强,尤其是红松。生长季末(9月)降水对红松和红皮云杉的限制作用由升温前的负相关转变为升温后的显著正相关。温度是限制红松和红皮云杉径向生长的主要气候因子,降水影响相对较弱;其中红松径向生长对气候变化的响应比红皮云杉更敏感。快速升温后,红松和红皮云杉生长-气候关系的变化可能与升温导致的暖干旱化有关。若气候变暖持续或加剧,二者径向生长的气候限制因子也将由温度转变为水分;红松和红皮云杉会出现生长衰退,尤其是红松。  相似文献   

14.
Alpine treeline ecotones are considered early-warning monitors of the effects of climate change on terrestrial ecosystems, but it is still unclear how accurately treeline dynamics may track the expected temperature rises. Site-specific abiotic constraints, such as topography and demographic trends may make treelines less responsive to environmental fluctuations. A better understanding on how local processes modulate treelines’ response to warming is thus required. We developed a model of treeline dynamics based on individual data of growth, mortality and reproduction. Specifically, we modeled growth patterns, mortality rates and reproductive size thresholds as a function of temperature and stand structure to evaluate the influence of climate- and stand-related processes on treeline dynamics. In this study, we analyze the dynamics of four Pyrenean mountain pine treeline sites with contrasting stand structures, and subjected to differing rates of climate warming. Our models indicate that Pyrenean treelines could reach basal areas and reproductive potentials similar to those currently observed in high-elevation subalpine forest by the mid twenty-first century. The fastest paces of treeline densification are forecasted by the late twenty-first century and are associated with higher warming rates. We found a common densification response of Pyrenean treelines to climate warming, but contrasting paces arise due to current size structures. Treelines characterized by a multistratified stand structure and subjected to lower mean annual temperatures were the most responsive to climate warming. In monostratified stands, tree growth was less sensitive to temperature than in multistratified stands and trees reached their reproductive size threshold later. Therefore, our simulations highlight that stand structure is paramount in modulating treeline responsiveness to ongoing climate warming. Synthesis. Treeline densification over the twenty-first century is likely to occur at different rates contingent on current stand structure and its effects on individual-level tree growth responses to warming. Accurate projections of future treeline dynamics must thus incorporate site-specific factors other than climate, specifically those related to stand structure and its influence on tree growth.  相似文献   

15.
根据兴安落叶松在大兴安岭山脉的分布特征,沿纬度设置了9个采样点,分析了兴安落叶松径向生长对气候因子响应的空间差异和时间动态。结果表明:总体上所有采样点的兴安落叶松径向生长与夏季(6—8月)标准化降水蒸散指数(SPEI)及降水量、2月SPEI及降水量呈正相关,与3月温度呈负相关。在空间上,南部年均温较高区域的兴安落叶松径向生长与2月SPEI呈显著正相关,在北部年均温较低的区域与3月温度呈显著负相关。在时间上,兴安落叶松生长-气候关系不稳定。随着温度升高,在年均温较高区域,夏季SPEI和降水量对树木生长的正效应以及夏季温度的负响应显著增强;在年均温较低区域,树木生长与3月温度负响应增强更明显。这表明气候变化改变了树木生长-气候关系,而且存在明显空间差异。在未来气候暖干化的背景下,大兴安岭兴安落叶松径向生长会受到抑制,在年均温较高且降水量较少的南部地区会因夏季水分亏缺和冬季干旱而衰退,温度较低的北部地区则可能因冬季干旱和冬季变暖而使生长受到抑制。  相似文献   

16.

Background

Chagas disease kills approximately 45 thousand people annually and affects 10 million people in Latin America and the southern United States. The parasite that causes the disease, Trypanosoma cruzi, can be transmitted by insects of the family Reduviidae, subfamily Triatominae. Any study that attempts to evaluate risk for Chagas disease must focus on the ecology and biogeography of these vectors. Expected distributional shifts of vector species due to climate change are likely to alter spatial patterns of risk of Chagas disease, presumably through northward expansion of high risk areas in North America.

Methodology/Principal Findings

We forecast the future (2050) distributions in North America of Triatoma gerstaeckeri and T. sanguisuga, two of the most common triatomine species and important vectors of Trypanosoma cruzi in the southern United States. Our aim was to analyze how climate change might affect the future shift of Chagas disease in North America using a maximum entropy algorithm to predict changes in suitable habitat based on vector occurrence points and predictive environmental variables. Projections based on three different general circulation models (CCCMA, CSIRO, and HADCM3) and two IPCC scenarios (A2 and B2) were analyzed. Twenty models were developed for each case and evaluated via cross-validation. The final model averages result from all twenty of these models. All models had AUC >0.90, which indicates that the models are robust. Our results predict a potential northern shift in the distribution of T. gerstaeckeri and a northern and southern distributional shift of T. sanguisuga from its current range due to climate change.

Conclusions/Significance

The results of this study provide baseline information for monitoring the northward shift of potential risk from Chagas disease in the face of climate change.  相似文献   

17.
Climate change has been unprecedented in the last half-century. Tree growth dynamics and responses to climate warming at different elevations vary by study area due to regional diversity in site-specific climatic conditions in the central Hengduan Mountains. A. georgei is the dominant species in high-elevation montane forests in the central Hengduan Mountains. To study the response of A. georgei radial growth to climate and identify tree growth trends at different elevations, tree-ring width chronologies at four elevations across the subalpine A. georgei forest belt were built and growth-climate relationships were analyzed. The primary findings of this study were as follows: (1) radial growth rates of A. georgei decreased with elevation; (2) warming alleviated the limitation of low temperatures and abundant precipitation on tree radial growth at the highest sampling site; and (3) unlike at other elevations, the trend of trees basal area increment (BAI) at the lowest sampling site showed a significant decline over the past 20 years. This suggests the presence of an elevational inflection point, likely between 3800 m and 4000 m, where tree growth trends diverge. These results confirmed that A. georgei at higher elevation in the central Hengduan Mountains currently benefits from higher temperatures. However, the effects of drought on A. georgei at lower elevations would cause radial growth to decrease with climate warming. Therefore, it is critical to establish effective management strategies based on how A. georgei responds to climate change at various elevations.  相似文献   

18.
The larch forests at the southern limit of the Siberian boreal forest in Central Asia have repeatedly experienced strong recent growth declines attributed to decreasing summer precipitation in the course of climate warming. Here, we present evidence from the southernmost Larix sibirica forests in eastern Kazakhstan that these declines are primarily caused by a decrease in effective moisture due to increasing summer temperatures, despite constant annual, and summer precipitation. Tree-ring chronologies (>800 trees) showed a reduction by 50–80% in mean ring width and an increase in the frequency of missing rings since the 1970s. Climate-response analysis revealed a stronger (negative) effect of summer temperature (in particular of the previous year’s June and July temperature) on radial growth than summer precipitation (positive effect). It is assumed that a rise in the atmospheric vapor pressure deficit, which typically increases with temperature, is negatively affecting tree water status and radial growth, either directly or indirectly through reduced soil moisture. Larch rejuvenation ceased in the 1950s, which is partly explained by increasing topsoil desiccation in a warmer climate and a high drought susceptibility of larch germination, as was demonstrated by a germination experiment with variable soil moisture levels. The lack of regeneration and the reduced annual stem increment suggest that sustainable forest management aiming at timber harvesting is no longer feasible in these southern boreal forests. Progressive climate warming is likely to cause a future northward shift of the southern limit of the boreal forest.  相似文献   

19.
基于建立的小兴安岭南麓红松树轮宽度标准年表,分析红松径向生长与该地区温度和降水间的关系以及1982年升温突变对此相关性的影响。结果表明:6月平均温度与树轮宽度年表在变暖前后始终呈极显著负相关,是该地区红松径向生长的主要限制因子。基于此构建的区域1843—1982年6月平均温度重建方程稳定可靠。重建温度序列的偏暖时期和偏冷时期分别持续7年和29年,偏暖时段为1915—1921年,偏冷时段为1880—1891年和1932—1948年。小波分析结果显示6月平均温度存在2—7a周期变化。空间相关分析结果表明重建温度序列能很好的代表小兴安岭南麓及附近区域的温度变化。本研究拓展了研究区现有的气候数据,可为掌握小兴安岭气候变化规律和科学预测未来气候提供数据支撑。  相似文献   

20.
Forests modify their productivity, composition, and distribution in response to global change. We studied the radial growth trends of the Western Mediterranean oak Quercus pyrenaica over the last two centuries to analyze whether trees exhibited instability in productivity in response to climatic changes. Trees were sampled to build annual growth chronologies following climatic gradients of increasing moisture availability and decreasing temperature with altitude and latitude. The species’ response to climate showed high variability linked to local climatic conditions. The strength in the positive response of trees to moisture availability was inversely related to precipitation (that is, enhanced by higher water stress) whereas high temperature in the growing season was positive for tree-growth only at cold sites. The oldest ages of trees expanded back to the late 1500 s. These old-growth trees were located at the coldest sites and exhibited a long-term increase in productivity starting 150 years ago which could express a dominant positive effect of warming temperatures since the mid 1800 s at cold-humid sites. Conversely, trees at dry sites exhibited negative growth trends. Particularly low elevation stands located at latitudes below 40° displayed enhanced growth constraints with the increase in water stress around 1970, which suggests vulnerability of Quercus pyrenaica at the sampled altitudinal dry edge. The response of trees to future changes in climate should be monitored, particularly in threatened transitional zones.  相似文献   

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