高山林线植被对气候变化十分敏感，已成为全球变化研究的热点。研究了大兴安岭北部大白山高山 林线的树木生长和群落璺新动态及其与气候变化、火干扰等因素的关系。结果表明，林线树木的生长对气候变化十分敏感，但其敏感性随着海拔的降低而减弱；在高 海拔，林线树木的径向生长与上年生长季后期（8月）降水负相关，而与上年初秋（9月）温度正相关，这些限制作用随着海拔的降低而逐渐消失；与此相反，低海 拔树木生长与当年冬末春初（3月）的温度负相关，但随着海拔上升这种限制作用消失。分析结果还表明，本地区的群落更新主要受火干扰驱动，而与气候变化没有 显著关系。不同树种在火灾后更新的时间存在差异，这种差异又因海拔的不同而异，反映出不同树种的更新策略及对环境变化适应能力的差异。大兴安岭北部的高山 林线在树木生长对气候变化的敏感性、与气候因子的关系及群落更新动态等方面均与干旱区林线有明显的差异，这些差异与气候条件、树种、更新驱动力等方面的不 同有密切的关系。

高山林线植被对气候变化十分敏感，已成为全球变化研究的热点。研究了大兴安岭北部大白山高山 林线的树木生长和群落璺新动态及其与气候变化、火干扰等因素的关系。结果表明，林线树木的生长对气候变化十分敏感，但其敏感性随着海拔的降低而减弱；在高 海拔，林线树木的径向生长与上年生长季后期（8月）降水负相关，而与上年初秋（9月）温度正相关，这些限制作用随着海拔的降低而逐渐消失；与此相反，低海 拔树木生长与当年冬末春初（3月）的温度负相关，但随着海拔上升这种限制作用消失。分析结果还表明，本地区的群落更新主要受火干扰驱动，而与气候变化没有 显著关系。不同树种在火灾后更新的时间存在差异，这种差异又因海拔的不同而异，反映出不同树种的更新策略及对环境变化适应能力的差异。大兴安岭北部的高山 林线在树木生长对气候变化的敏感性、与气候因子的关系及群落更新动态等方面均与干旱区林线有明显的差异，这些差异与气候条件、树种、更新驱动力等方面的不 同有密切的关系。

Reducing tree densities through silvicultural thinning has been widely advocated as a strategy for enhancing resistance and resilience to drought, yet few empirical evaluations of this approach exist. We examined detailed dendrochronological data from a long-term (>50 years) replicated thinning experiment to determine if density reductions conferred greater resistance and/or resilience to droughts, assessed by the magnitude of stand-level growth reductions. Our results suggest that thinning generally enhanced drought resistance and resilience; however, this relationship showed a pronounced reversal over time in stands maintained at lower tree densities. Specifically, lower-density stands exhibited greater resistance and resilience at younger ages (49 years), yet exhibited lower resistance and resilience at older ages (76 years), relative to higher-density stands. We attribute this reversal to significantly greater tree sizes attained within the lower-density stands through stand development, which in turn increased tree-level water demand during the later droughts. Results from response-function analyses indicate that thinning altered growth-climate relationships, such that higher-density stands were more sensitive to growing-season precipitation relative to lower-density stands. These results confirm the potential of density management to moderate drought impacts on growth, and they highlight the importance of accounting for stand structure when predicting climate-change impacts to forests.

植物群落是不同植物在长期环境变化中相互作用、相互适应而形成的组合。它提供着人类赖以生存的主要物质资源, 维系着地球生态系统的健康和功能, 也为各种动物和其他生物提供食物来源和栖息地, 是人类生存和发展不可或缺的物质基础, 具有不可替代的作用。我国植物群落类型多样, 在世界上首屈一指, 但我国至今尚没有一次全面和系统的植物群落清查, 不仅影响了人们对我国植物资源的了解、利用和保护, 也不利于我国生态学、环境科学和地理学等相关学科的发展。采用统一的方法体系和技术规范开展我国植物群落的清查工作势在必行, 并具有紧迫性。本文基于作者长期的野外工作实践和国内外的群落调查方法, 首先简要定义了与植物群落清查有关的重要概念, 在此基础上, 论述了调查样地的设置原则和体系、群落清查的技术指标和方法、主要优势种生态属性的测定方法和规范, 并介绍了大样地调查的主要步骤。通过本文的介绍、归纳和总结, 试图为制定我国植物群落清查的技术规范提供基础材料和技术储备。

植物群落是不同植物在长期环境变化中相互作用、相互适应而形成的组合。它提供着人类赖以生存的主要物质资源, 维系着地球生态系统的健康和功能, 也为各种动物和其他生物提供食物来源和栖息地, 是人类生存和发展不可或缺的物质基础, 具有不可替代的作用。我国植物群落类型多样, 在世界上首屈一指, 但我国至今尚没有一次全面和系统的植物群落清查, 不仅影响了人们对我国植物资源的了解、利用和保护, 也不利于我国生态学、环境科学和地理学等相关学科的发展。采用统一的方法体系和技术规范开展我国植物群落的清查工作势在必行, 并具有紧迫性。本文基于作者长期的野外工作实践和国内外的群落调查方法, 首先简要定义了与植物群落清查有关的重要概念, 在此基础上, 论述了调查样地的设置原则和体系、群落清查的技术指标和方法、主要优势种生态属性的测定方法和规范, 并介绍了大样地调查的主要步骤。通过本文的介绍、归纳和总结, 试图为制定我国植物群落清查的技术规范提供基础材料和技术储备。

Subtropical forests in montane ecosystems grow under a wide range of environmental conditions. However, little is known about the growth responses of subtropical trees to climate along ecological gradients. To assess how, and to what extent climate controls tree growth, we analyzed tree responses to climate for 15 chronologies from 4 different species (Schinopsis lorentzii, Juglans australis, Cedrela lilloi, Alnus acuminata) across a variety of environments in subtropical forests from northwestern Argentina (22-28A degrees S, 64-66A degrees W). Using correlation and principal component analysis, site and species differences in tree-growth responses to precipitation and temperature were determined along the elevation gradient from the dry-warm Chaco lowlands to the wet-cool montane Yungas. Our results show that species responses differ according to the severity in climate conditions along the elevation gradient. At sites with unfavorable conditions, mainly located at the extremes of the environmental gradient, responses of different species to climate variations are similar; in contrast, at sites with relatively mild conditions, tree growth displays a large variety of responses reflecting differences in both local environmental conditions and species physiology. Our research suggests that individualistic responses to environmental variability would determine differences in the type and timing of the responses of dominant trees to climate, which ultimately may shift species' assemblages in montane subtropical regions of South America under future climate changes.

Climatic warming during the last glacial 搃nterglacial transition (LGIT) was punctuated by reversals to glacial-like conditions. Palaeorecords of ecosystem change can help document the geographical extent of these events and improve our understanding of biotic sensitivity to climatic forcing. To reconstruct ecosystem and climatic variations during the LGIT, we analyzed lake sediments from southwestern Alaska for fossil pollen assemblages, biogenic-silica content (BSiO 2 %), and organic-carbon content (OC%). Betula shrub tundra replaced herb tundra as the dominant vegetation of the region around 13 600 cal BP (cal BP: 14 C calibrated calendar years before present), as inferred from an increase of Betula pollen percentages from << 5% to >> 20% with associated decreases in Cyperaceae, Poaceae, and Artemisia . At c . 13 000 cal BP, a decrease of Betula pollen from 28 to << 5% suggests that shrub tundra reverted to herb tundra. Shrub tundra replaced herb tundra to resume as the dominant vegetation at 11 600 cal BP. Higher OC% and BSiO 2 % values suggest more stable soils and higher aquatic productivity during shrub-tundra periods than during herb-tundra periods, although pollen changes lagged behind changes in the biogeochemical indicators before c . 13 000 cal BP. Comparison of our palaeoecological data with the ice-core d 18 O record from Greenland reveals strikingly similar patterns from the onset through the termination of the Younger Dryas (YD). This similarity supports the hypothesis that, as in the North Atlantic region, pronounced YD climatic oscillations occurred in the North Pacific region. The rapidity and magnitude of ecological changes at the termination of the YD are consistent with greenhouse experiments and historic photographs demonstrating tundra sensitivity to climatic forcing.

Based on the CRU data in Central Asia during the period of 1971 2000, in this paper the method of linear regression was used to analyze the climate change in Central Asia in recent 30 years. The results showed that the desert regions in Turkmenistan and Uzbekistan were the aridest areas with the highest temperature in Central Asia. Precipitation in Tajikistan and Kyrgyzstan in winter and spring was higher than that in summer and autumn, and temperature range was relatively low. In Kazakhstan, precipitation occurred mainly in summer, and it decreased from the west to the east; the range of temperature was high, and it was warmer in the west than that in the east. The annual range of temperature in Central Asia was low. There was a significant difference of climate between Xinjiang of China and the five countries in Central Asia, precipitation in Xinjiang occurred mainly in the Tianshan Mountains and in summer, where the warming trend was obvious, and the change trend of maximum and minimum temperature was opposite to that in the western part of Central Asia.

Based on the CRU data in Central Asia during the period of 1971 2000, in this paper the method of linear regression was used to analyze the climate change in Central Asia in recent 30 years. The results showed that the desert regions in Turkmenistan and Uzbekistan were the aridest areas with the highest temperature in Central Asia. Precipitation in Tajikistan and Kyrgyzstan in winter and spring was higher than that in summer and autumn, and temperature range was relatively low. In Kazakhstan, precipitation occurred mainly in summer, and it decreased from the west to the east; the range of temperature was high, and it was warmer in the west than that in the east. The annual range of temperature in Central Asia was low. There was a significant difference of climate between Xinjiang of China and the five countries in Central Asia, precipitation in Xinjiang occurred mainly in the Tianshan Mountains and in summer, where the warming trend was obvious, and the change trend of maximum and minimum temperature was opposite to that in the western part of Central Asia.

Abstract An overview is presented of the phenological models relevant for boreal coniferous, temperate-zone deciduous and Mediterranean coniferous forest ecosystems. The phenology of the boreal forests is mainly driven by temperature, affecting the timing of the start of the growing season and thereby its duration, and the level of frost hardiness and thereby the reduction of foliage area and photosynthetic capacity by severe frost events. The phenology of temperate-zone forests is also mainly driven by temperature. Since temperate-zone forests are mostly mixed-species deciduous forests, differences in phenological response may affect competition between tree species. The phenology of Mediterranean coniferous forests is mainly driven by water availability, affecting the development of leaf area, rather than the timing of phenological events. These phenological models were subsequently coupled to the process-based forest model FORGRO to evaluate the effect of different climate change scenarios on growth. The results indicate that the phenology of each of the forest types significantly affects the growth response to a given climate change scenario. The absolute responses presented in this study should, however, be used with caution as there are still uncertainties in the phenological models, the growth models, the parameter values obtained and the climate change scenarios used. Future research should attempt to reduce these uncertainties. It is recommended that phenological models that describe the mechanisms by which seasonality in climatic drivers affects the phenological aspects of trees should be developed and carefully tested. Only by using such models may we make an assessment of the impact of climate change on the functioning and productivity of different forest ecosystems.

We present an extensive new network of ring-width chronologies, comprising data from 100 sites within the Austrian Eastern Alps, made up of multiple tree species. Principal components analysis and cluster analysis were used to identify five separate high-frequency tree-growth signals from these data. Tree-growth variability at these sites is explained by site altitude and species differences that moderate the effects of the annually varying climatic forcing on tree growth. Recently developed, two-century long gridded climate data sets for the Greater Alpine Region were used to assess the relationship between climate and tree growth. Tree growth at low altitudes is controlled mainly by spring-summer moisture availability. At high altitudes precipitation is no longer a limiting factor and growth is mostly determined by summer temperature. In the intermediate altitudinal range, we did not find any direct relationships with specific climatic variables. High-altitude chronologies suitable for reconstructing past temperatures and low-altitude chronologies suitable for reconstructing past precipitation were identified.

Higher atmospheric CO2 concentrations (ca) can under certain conditions increase tree growth by enhancing photosynthesis, resulting in an increase of intrinsic water-use efficiency (iWUE) in trees. However, the magnitude of these effects and their interactions with changing climatic conditions are still poorly understood under xeric and mesic conditions.We combined radial growth analysis with intra- and interannual 020713C and 020718O measurements to investigate growth and physiological responses of Larix decidua, Picea abies, Pinus sylvestris, Pinus nigra and Pseudotsuga menziesii in relation to rising ca and changing climate at a xeric site in the dry inner Alps and at a mesic site in the Swiss lowlands.iWUE increased significantly over the last 50 yr by 809000929% and varied depending on species, site water availability, and seasons. Regardless of species and increased iWUE, radial growth has significantly declined under xeric conditions, whereas growth has not increased as expected under mesic conditions. Overall, drought-induced stomatal closure has reduced transpiration at the cost of reduced carbon uptake and growth.Our results indicate that, even under mesic conditions, the temperature-induced drought stress has overridden the potential CO2 090004fertilization090005 on tree growth, hence challenging today's predictions of improved forest productivity of temperate forests.

黑龙江黑河为我国红松(Pinus koraiensis)分布的北界，在研究红松林的生长、演替、分布，及其对气候变化的响应上有独特的意义。该文通过研究胜山保护区内阔叶红松林的演替系列(软阔叶林、硬阔叶林、阔叶红松近熟林和成熟林4个阶段)，分析了树木径向生长与气候变化的关系在不同演替阶段的差异。结果表明：从演替早期的软阔叶林到晚期的红松成熟林，年表统计特征表明树木径向生长对气候波动的敏感性逐步降低。对年轮-气候关系的分析结果也表明气候对树木径向生长的影响随着演替的进展呈现规律性的变化。上年6月和12月的气温与红松成熟林的径向生长显著正相关，表现出明显的“滞后效应”。红松成熟林的轮宽指数与当年6月气温显著负相关，而与当年6月降水量显著正相关，反映出生长季水分对红松生长的限制。上述这些限制作用均随着演替的进展而增强，但在演替的早期影响不显著。相反，上年6月降水量与软阔叶林的生长显著负相关，但该限制作用在演替的中晚期消失。这些差异反映出随着演替的进展，优势树种对水分的需求逐步提高。滑动相关分析表明研究区近几十年明显的气候干暖化趋势对各林型的生长兼具有利和不利的影响。不同因素综合作用下，软、硬阔叶林阶段生长尚未产生清晰的长期变化趋势。但由于水分对红松林生长的限制作用增强，红松林生长明显下降。今后气候进一步干暖化可能对红松林的生长、恢复演替和分布有不利影响。

黑龙江黑河为我国红松(Pinus koraiensis)分布的北界，在研究红松林的生长、演替、分布，及其对气候变化的响应上有独特的意义。该文通过研究胜山保护区内阔叶红松林的演替系列(软阔叶林、硬阔叶林、阔叶红松近熟林和成熟林4个阶段)，分析了树木径向生长与气候变化的关系在不同演替阶段的差异。结果表明：从演替早期的软阔叶林到晚期的红松成熟林，年表统计特征表明树木径向生长对气候波动的敏感性逐步降低。对年轮-气候关系的分析结果也表明气候对树木径向生长的影响随着演替的进展呈现规律性的变化。上年6月和12月的气温与红松成熟林的径向生长显著正相关，表现出明显的“滞后效应”。红松成熟林的轮宽指数与当年6月气温显著负相关，而与当年6月降水量显著正相关，反映出生长季水分对红松生长的限制。上述这些限制作用均随着演替的进展而增强，但在演替的早期影响不显著。相反，上年6月降水量与软阔叶林的生长显著负相关，但该限制作用在演替的中晚期消失。这些差异反映出随着演替的进展，优势树种对水分的需求逐步提高。滑动相关分析表明研究区近几十年明显的气候干暖化趋势对各林型的生长兼具有利和不利的影响。不同因素综合作用下，软、硬阔叶林阶段生长尚未产生清晰的长期变化趋势。但由于水分对红松林生长的限制作用增强，红松林生长明显下降。今后气候进一步干暖化可能对红松林的生长、恢复演替和分布有不利影响。

运用树木年轮气候学方法,研究了不同纬度阔叶红松林红松径向生长趋势及其与气候因子的关系,以期揭示不同纬度红松径向生长对气候因子响应的差异以及气候变化影响下红松的动态特征、适应性及敏感性.结果表明：不同纬度红松径向生长对当地气候因子的响应存在差异,最南部的白石砬子自然保护区红松径向生长与生长季的平均相对湿度呈显著正相关,与平均最高气温呈显著负相关.中部的长白山自然保护区的低海拔区域红松径向生长与生长季的水分因子（降水、相对湿度和帕尔默干旱指数PDSI）呈显著正相关,而与平均最高气温呈显著负相关;凉水自然保护区红松径向生长与生长季的水分因子（相对湿度和PDSI）呈显著正相关,与气温因子（平均气温和平均最高气温）呈显著负相关.而最北部的胜山自然保护区红松径向生长则与大部分月份的气温因子呈显著正相关.当年6月气候因子是影响所有纬度红松径向生长的关键气候因子,4个样地都与当年6月平均最高气温呈显著负相关.在气温不断上升的近40年,最南部的红松径向生长呈显著下降趋势,最北部呈显著上升趋势,中部的变化不显著.如果未来气温升高而降水不变,红松分布区可能缩小.

运用树木年轮气候学方法,研究了不同纬度阔叶红松林红松径向生长趋势及其与气候因子的关系,以期揭示不同纬度红松径向生长对气候因子响应的差异以及气候变化影响下红松的动态特征、适应性及敏感性.结果表明：不同纬度红松径向生长对当地气候因子的响应存在差异,最南部的白石砬子自然保护区红松径向生长与生长季的平均相对湿度呈显著正相关,与平均最高气温呈显著负相关.中部的长白山自然保护区的低海拔区域红松径向生长与生长季的水分因子（降水、相对湿度和帕尔默干旱指数PDSI）呈显著正相关,而与平均最高气温呈显著负相关;凉水自然保护区红松径向生长与生长季的水分因子（相对湿度和PDSI）呈显著正相关,与气温因子（平均气温和平均最高气温）呈显著负相关.而最北部的胜山自然保护区红松径向生长则与大部分月份的气温因子呈显著正相关.当年6月气候因子是影响所有纬度红松径向生长的关键气候因子,4个样地都与当年6月平均最高气温呈显著负相关.在气温不断上升的近40年,最南部的红松径向生长呈显著下降趋势,最北部呈显著上升趋势,中部的变化不显著.如果未来气温升高而降水不变,红松分布区可能缩小.

In most dendrochronological studies, climate rowth relationships are established on dominant trees to minimize non-climatic signals. However, response to environmental factors may be affected by tree-size, which begs the question of the representativeness of dominant trees on the stand level. To highlight the variations in climate rowth relationships among sizes and species, under a wide range of ecological conditions (climate and soil properties), 61 pure even-aged stands were sampled across France. At each stand, two tree-ring chronologies were established from 10 big- to 10 small-diameter trees. Our objectives were, (1) to assess variations in climate sensitivity between the two size-diameter classes, and (2) to investigate the role of species and ecological conditions on these variations. The climate-growth relationships were evaluated from 122 tree-ring chronologies (1 220 trees) through extreme growth years and correlation function analyses. Sensitivity to climate of shade-intolerant and moderately shade-tolerant species ( Picea abies (L.) Karst., Pinus sylvestris L. and Quercus petraea (Matt.) Liebl.) remained constant between the size-diameter classes for both temperature and hydric balance, while the shade-tolerant species Abies alba Mill. and Fagus sylvatica L. displayed significant differences, with larger trees being more sensitive to summer drought than smaller trees. This difference increased with increasing climatic xericity. Our results suggest that, for shade-tolerant species, (1) big trees could be more sensitive to climatic change especially under xeric climate, and (2) future tree ring studies should include trees stratified by size to produce unbiased estimation of sensitivity to climate.