Climate response of Picea schrenkiana based on tree-ring width and maximum density

The effect of global warming on alpine forests is complex. It is crucial, therefore, to investigate the effects of climate change on the radial growth of trees at different altitudes. The tree growth–climate relationship remains poorly understood at large spatial scales in the Tianshan Mountains, China. Schrenk spruce (P. schrenkiana) is a unique tree species to this area. In this study, we collected tree-ring width and maximum density data from nine plots along an altitudinal gradient. Results showed that altitude affected both tree-ring width and maximum density. At high altitudes, tree-ring width was positively correlated with temperature in February of the current year. Tree-ring width was also positively correlated with precipitation in July of the previous year, and January and July of the current year, and negatively correlated with the monthly diurnal temperature range (DTR). At low altitudes, tree-ring width was negatively correlated with temperature in the early growing season and the growing season. Tree-ring width was positively correlated with precipitation in June and September of the previous year, and May of the current year. The tree-ring maximum density was positively correlated with temperature and the DTR of the growing season, and negatively correlated with precipitation in winter and growing season. Moving correlation analysis showed that the positive response of tree-ring width to precipitation in the growing season was enhanced over time at high altitudes. In the low-altitude trees, the negative response of tree-ring width to temperature in the growing season was reduced, while the positive response to precipitation in the growing season was enhanced. The positive response relationship between tree-ring maximum density and the temperature in July weakened over time. At low altitudes, the negative response of tree-ring maximum density to winter precipitation was strengthened, and a stable negative response to July precipitation was observed. As the climate becomes wetter and warmer in the Tianshan Mountains, our results suggest that the radial growth of trees may benefit at elevations above 2400 m a.s.l. There was no obvious elevation limit for the increase in tree-ring maximum density. These findings provide a basis for sustainable forest management under global climate change.     

呼伦贝尔沙地樟子松年轮生长对气候变化的响应

以内蒙古呼伦贝尔地区沙地樟子松为样本,建立了樟子松树木年轮宽度年表,应用相关分析和响应函数分析等年轮气候学方法,研究了樟子松径向生长对气候变化的响应。结果表明,樟子松年轮宽度与4月和6—9月平均温度呈显著负相关关系(P<0.05);与各月降水量多呈正相关关系,特别是与当年5—8月的月降水量呈显著正相关关系(P<0.05);树轮年表与前一年10月至当年10月的PDSI均呈显著正相关关系(P<0.05),其中与5月份PDSI的相关性最高。响应函数分析表明,年表与当年6—7月的平均气温、上一年10月和当年5—7月份的降雨存在显著的相关性,与5—7月份PDSI存在较显著的正相关性;综合来看,呼伦贝尔沙地樟子松生长同时受降水和温度的影响,其径向生长与气候因子间的关系属于降水敏感型,为区域降水重建提供了科学基础。     

内蒙古草原沙地白扦年轮生长指数的变异内蒙古草原沙地白扦年轮生长指数的变异

运用响应函数、相关函数、单年分析等树木年轮气候学的方法 ,研究了锡林河流域草原沙地上白扦年轮生长指数的变异。结果表明 :白扦的生长对环境的变化相当敏感 ,当年 9月至上年 8月的月平均温度和月降雨量解释年轮宽度方差量的约 70 % ;白扦当年的生长量与上年 9月、当年 2月、5月的降雨量之间具明显的正相关性 ,而与当年 5月的大气温度具显著负相关关系。由于沙地具有渗透性较强和防止土壤深层水分蒸发的特点 ,特别是上年 8～10月的降雨可部分保存于沙地内 ,便于植物下年利用。由此认为 ,在沿锡林河流域中部的沙带上 ,建立以现有白扦为分布中心的人工白扦林将是完全可行的     

长白山北坡不同年龄红松年表及其对气候的响应

运用树木年轮气候学方法,研究了长白山北坡红松(Pinus koraiensis)不同年龄年表特征及其与气候因子间的关系,以期揭示年龄因素对年表的潜在影响。结果表明,平均年龄为63a的红松低龄年表与平均年龄为184a的高龄年表对气候的响应明显不同:低龄红松径向生长与当年1、2月月平均温度负相关(P<0.05),同时也受到上年及当年多个月份的月平均最高温度或最低温度的影响,但与降水的相关性未达到显著水平;高龄红松径向生长则与月平均温度间的关系不明显,而与当年1、2、4、6、7、9月的月平均最高温度正相关,与当年4月、9月的月平均最低温度负相关,同时受到上年5月及当年5月月总降水量的影响。因此,年龄因素对红松年表的气候响应方面存在一定影响,且高龄年表对气候响应的敏感性更高,包含有更多的气候信息。     

近40年河北坝上地区杨树人工林径向生长对气候变化的响应差异

运用树木年轮气候学方法,研究近40年河北坝上地区健康和衰退小叶杨人工林径向生长对气候响应敏感性差异,揭示健康和衰退杨树生长与气候关系的时间变异规律。结果表明：（1）衰退杨树径向生长对温度、降水等气候因素响应较健康杨树敏感。衰退杨树年表中的气候信号较强,与当年生长季（4、8-10月）的气温因素呈显著负相关,与上一年休眠期（9月-当年1月）和当年生长季（7月）的降水和相对湿度呈显著正相关。健康杨树年表中气候信号较弱,主要与上一年冬季（12月）和当年生长季（4月）的气温因素呈显著负相关,与上一年生长末期（8-11月）降水和相对湿度呈显著正相关。（2）从各年表与帕默尔干旱指数（PDSI）的响应强度来看,衰退杨树生长更易受夏季干旱胁迫影响。衰退杨树年表与上一年9月-当年3月、6-10月的PDSI呈显著正相关,而健康杨树径向生长与PDSI呈弱的正相关。（3）1975-2017年间,随气温升高,健康和衰退杨树生长对温度的敏感性下降;健康杨树生长对降水和PDSI的敏感性较为稳定,适应能力强,而衰退杨树生长对降水和PDSI的敏感性增强,适应能力变弱。综上所述,干旱胁迫是限制衰退杨树生长的主要因素,而健康杨树生长受气候影响较弱,能适应当地气候条件。衰退杨树对气候变化响应较健康杨树明显,在气候变暖背景下,衰退杨树生长的气候限制因子由温度转变为水分,导致河北坝上地区遭受干旱灾害时发生退化的趋势更加明显。     

The climatic drivers of primary Picea forest growth along the Carpathian arc are changing under rising temperatures

Climatic constraints on tree growth mediate an important link between terrestrial and atmospheric carbon pools. Tree rings provide valuable information on climate‐driven growth patterns, but existing data tend to be biased toward older trees on climatically extreme sites. Understanding climate change responses of biogeographic regions requires data that integrate spatial variability in growing conditions and forest structure. We analyzed both temporal (c. 1901–2010) and spatial variation in radial growth patterns in 9,876 trees from fragments of primary Picea abies forests spanning the latitudinal and altitudinal extent of the Carpathian arc. Growth was positively correlated with summer temperatures and spring moisture availability throughout the entire region. However, important seasonal variation in climate responses occurred along geospatial gradients. At northern sites, winter precipitation and October temperatures of the year preceding ring formation were positively correlated with ring width. In contrast, trees at the southern extent of the Carpathians responded negatively to warm and dry conditions in autumn of the year preceding ring formation. An assessment of regional synchronization in radial growth variability showed temporal fluctuations throughout the 20th century linked to the onset of moisture limitation in southern landscapes. Since the beginning of the study period, differences between high and low elevations in the temperature sensitivity of tree growth generally declined, while moisture sensitivity increased at lower elevations. Growth trend analyses demonstrated changes in absolute tree growth rates linked to climatic change, with basal area increments in northern landscapes and lower altitudes responding positively to recent warming. Tree growth has predominantly increased with rising temperatures in the Carpathians, accompanied by early indicators that portions of the mountain range are transitioning from temperature to moisture limitation. Continued warming will alleviate large‐scale temperature constraints on tree growth, giving increasing weight to local drivers that are more challenging to predict.     

Long-term growth decline in Toona ciliata in a moist tropical forest in Bangladesh: Impact of global warming

Tropical forests are carbon rich ecosystems and small changes in tropical forest tree growth substantially influence the global carbon cycle. Forest monitoring studies report inconsistent growth changes in tropical forest trees over the past decades. Most of the studies highlighted changes in the forest level carbon gain, neglecting the species-specific growth changes which ultimately determine community-level responses. Tree-ring analysis can provide historical data on species-specific tree growth with annual resolution. Such studies are inadequate in Bangladesh, which is one of the most climate sensitive regions in the tropics. In this study, we investigated long-term growth rates of Toona ciliata in a moist tropical forest of Bangladesh by using tree-ring analysis. We sampled 50 trees of varying size, obtained increment cores from these trees and measured tree-ring width. Analyses of growth patterns revealed size-dependent growth increments. After correcting for the effect of tree size on tree growth (ontogenetic changes) by two different methods we found declining growth rates in T. ciliata from 1960 to 2013. Standardized ring-width index (RWI) was strongly negatively correlated with annual mean and maximum temperatures suggesting that rising temperature might cause the observed growth decline in T. ciliata. Assuming that global temperatures will rise at the current rate, the observed growth decline is assumed to continue. The analysis of stable carbon and oxygen isotopes may reveal more insight on the physiological response of this species to future climatic changes.     

川西亚高山不同海拔岷江冷杉树轮碳稳定同位素对气候的响应

树木年轮(简称树轮)碳稳定同位素技术是研究树轮气候学的一种有效方法。利用四川卧龙亚高山暗针叶林不同海拔高度岷江冷杉树轮样本资料,提取该树轮稳定碳同位素(δ13C)和去趋势序列(DS),研究其树轮碳稳定同位素序列对气候要素(降水、月平均温度和月平均相对湿度)的响应关系,初步揭示了在全球气候变化背景下,川西亚高山森林岷江冷杉树木生长对气候因子变化(气候变暖、降水减少等)的响应方式。主要结论有:(1)岷江冷杉树轮δ13C组成变化范围为-23.33‰—-26.31‰,平均值为-24.91‰,变异系数为-0.011—-0.038,并表现出较强的一阶自相关;其对环境变化有较好的指示作用,表明岷江冷杉树轮δ13C组成在年际变化中较为稳定。(2)低海拔的岷江冷杉树轮δ13C分馏主要与当年8月月平均相对湿度和当年12月月平均温度相关性显著(P0.05);高海拔岷江冷杉树轮δ13C分馏主要与上一年8月月平均相对湿度和当年4月月平均温度相关性显著(P0.05);中海拔的岷江冷杉树轮δ13C分馏主要与上一年1、11月月平均温度和当年2、11月月平均温度相关性显著(P0.05),冬季温度是中海拔区岷江冷杉树木生长的限制因子,且具有明显的"滞后效应"。川西卧龙亚高山暗针叶林岷江冷杉树木径向生长主要受到气温的制约,从生物学基础上阐明了树木生长与环境的关系,冬季温度的升高,有利于植物生长期的提前,植物生长旺盛,抗旱能力减弱;同时证明了建群种岷江冷杉对雨水的依赖很小,这有利于植物生存,且维持了该植物群落的稳定性。该研究弥补了我国青藏高原高海拔地区气象台站稀少、观测资料时间短缺,为预测未来气候变化对岷江冷杉树木径向生长变化提供了科学的依据。     

Xylem traits of peatland Scots pines reveal a complex climatic signal: A study in the Eastern Italian Alps

Long-term climate reconstructions are frequently based on tree-ring high-resolution proxies extracted from subfossil peatland trees. Peatlands are peculiar ecosystems characterized by high moisture in the upper soil part which creates a harsh living environment for trees. The climate mostly indirectly influences tree growth determining seasonal variations in the water table level. Within this framework, the aim of this study was to investigate climate responses of trees (Pinus sylvestris L.) growing inside and outside a Southern Alpine peat bog, by using tree-ring and wood anatomical traits (e.g. tracheid number and dimension, cell-wall thickness). Our results showed differences in the xylem structure and climate signal recorded by peatland and mineral soil trees. Peatland trees were characterized by narrow rings and tracheids with thinner cell wall. Summer temperature and precipitation were the major drivers of xylem formation in peatland trees. At intra-annual level wood anatomical traits revealed a complex within-ring signal during the growing season. The multi-parameters approach together with the high-resolution gained by using tree-ring sectors allowed us to obtain new detailed information on the xylem development of peatland trees and climate drivers that influenced it.     

利用树木年轮重建赣南地区1890年以来 2-3月份温度的变化

采用树木年轮气候学方法,利用江西赣南地区马尾松(Pinus massoniana)的年轮宽度资料,分析了马尾松径向生长与气候要素变化的相关及响应关系,结果表明赣南地区马尾松径向生长与当年2—3月份的平均温度相关性最高。在响应分析的基础上,重建了江西赣南地区1890年以来2—3月份温度的变化历史。重建序列显示在过去119a中研究区存在3个较为明显的冷期(1892—1906年、1918—1922年、1944—1957年)和3个明显的暖期(1909—1917年、1959—1968年和1998—2008年)。     

Response of regional tree-line forests to climate change: evidence from the northeastern Tibetan Plateau

Tree-ring width and age structure of Juniperus przewalskii (Qilian juniper) forests were analyzed for four tree-line sites in Qilian and Anyemaqen Mountains, northeastern Tibetan Plateau, to investigate their relationships to climate change. Tree-line growth on Qilian Mountain was mainly limited by temperature at the low-frequency band. However, tree-line growth in the Anyemaqen Mountain was highly correlated with the current growing season temperature at the high-frequency band, and with the previous growing season precipitation at the low-frequency band. A temperature-stressed growth pattern at colder western sites and a moisture-stressed growth pattern at the warm, drier eastern tree-line sites were detected. The number of surviving trees in the tree-line ecotone was not clearly correlated with temperature before the 1900s. An unprecedented rise in the number of trees coincided well with the rapid global warming after the 1900s.     

Does resin tapping affect the tree-ring growth and climate sensitivity of the Chinese pine (Pinus tabuliformis) in the Loess Plateau,China?

Resin tapping could affect water and nutrient transport processes in Chinese pine trees, rendering them more vulnerable to extreme climatic events, such as drought, and affecting the ecological function of forests in semi-arid regions. This study evaluated how resin tapping affects the tree-ring growth and climate sensitivity of Chinese pine in the Loess Plateau. We compared tree-ring growth patterns between the tapped and untapped faces of tapped trees, and investigated tree-ring growth and its response to climate between tapped and untapped trees in a forest stand during the 1967–2017 period. Tapped trees showed asymmetrical growth patterns after resin tapping, with narrower rings near the tapped face and wider ones near the untapped face. Furthermore, tapped trees had inter-annual variations consistent with those of untapped trees except for the years 2000 and 2001, with significantly lower values following resin tapping, and tree-ring growth then returning to normal. The climate response analysis indicated that the tree-ring growth of both tapped and untapped trees was negatively affected by monthly mean temperatures during the early growing season (May to July) in the post-resin-tapping period. Furthermore, tree-ring growth in tapped trees also revealed significant correlation with water vapour deficit and the Palmer drought index, which indicates that tapped trees are more vulnerable to drought. Further studies based on stable isotopes (i.e. δ¹³C, δ¹⁸O, and δ¹⁵N) could improve our understanding of the physiological mechanisms that regulate the effects of resin tapping on tree-ring growth.     

芦芽山华北落叶松(Larix principis-rupprechtii)树轮宽度年表对气候因子的响应

在芦芽山地区采集3个不同海拔的华北落叶松(Larix principis-rupprechtii),在传统去趋势的基础上,采用"signal-free"方法对拟合曲线进行修正,避免了中等频率的气候信息引起的拟合偏差,最终建立3个不同海拔树轮宽度标准年表(STD)。同时以10a为界对上述年表进行滤波处理,得到3个低频年表。年表特征值表明,随着海拔升高,年轮平均轮宽变窄,敏感性和高频信息增强,低频信息减弱,这可能与逐渐恶劣的生境有关。中、低海拔年表的低频信息更一致,中、高海拔的高频信息更接近,而高、低海拔无论是标准年表还是高频、低频年表相似性均较差。树轮气候响应分析显示,低海拔STD年表与5月最低温负相关最为显著,STD和低频年表均与5、6月份土壤温度显著负相关,说明生境暖干,树木主要受生长季的干旱胁迫;中海拔STD年表与当年5月最高温正相关最为显著,STD和低频年表与土壤温度相关均不显著,说明生境逐渐变得冷湿,生长季的低温成为树木生长的限制因子;高海拔STD年表与气象要素相关不显著,低频年表与当年4月土壤温度正相关,说明高海拔最为冷湿,并有季节性冻土分布,生长季的土壤低温成为树木生长的限制因子。因此,全球变暖的趋势将更有利于高海拔树木的生长,而低海拔树木的干旱胁迫进一步加剧。     

Tree-ring distinctness,dating potential and climatic sensitivity of laurel forest tree species in Tenerife Island

Macaronesian laurel forests are the only remnants of a subtropical palaeoecosystem dominant during the Tertiary in Europe and northern Africa. These biodiverse ecosystems are restricted to cloudy and temperate insular environments in the North Atlantic Ocean. Due to their reduced distribution area, these forests are particularly vulnerable to anthropogenic disturbances and changes in climatic conditions. The assessment of laurel forest trees’ response to climate variation by dendrochronological methods is limited because it was assumed that the lack of marked seasonality would prevent the formation of distinct annual tree rings. The aims of this study were to identify the presence of annual growth rings and to assess the dendrochronological potential of the most representative tree species from laurel forests in Tenerife, Canary Islands. We sampled increment cores from 498 trees of 12 species in two well-preserved forests in Tenerife Island. We evaluated tree-ring boundary distinctness, dating potential, and sensitivity of tree-ring growth to climate and, particularly, to drought occurrence. Eight species showed clear tree-ring boundaries, but synchronic annual tree rings and robust tree-ring chronologies were only obtained for Laurus novocanariensis, Ilex perado subsp. platyphylla, Persea indica and Picconia excelsa, a third of the studied species. Tree-ring width depended on water balance and drought occurrence, showing sharp reductions in growth in the face of decreased water availability, a response that was consistent among species and sites. Inter-annual tree-ring width variation was directly dependent on rainfall input in the humid period, from previous October to current April. The four negative pointer years 1995, 1999, 2008 and 2012 corresponded to severe drought events in the study area. This study gives the first assessment of dendrochronological potential and tree-ring climate sensitivity of tree species from the Tenerife laurel forest, which opens new research avenues for dendroecological studies in Macaronesian laurel forests.     

近几十年来冀西北山地白桦次生林径向生长对气候变化的响应

研究不同海拔高度天然次生林径向生长特征及其对气候变化的响应, 揭示影响山地树木径向生长的主要因子, 对于研究气候变化对温带森林生态系统适应性生长、演替和可持续经营的影响具有重要意义。该研究以冀西北山地次生林优势树种白桦(Betula platyphylla)为对象, 于研究区海拔1 350、1 550、1 750、1 950 m处分别设置样地, 采集样木树芯和圆盘, 运用树木年轮气候学方法建立白桦天然次生林标准年表, 并将年轮宽度指数与气候因子进行相关、多元逐步回归分析。主要结果: (1) 1960-2018年研究区气候呈变暖变干趋势, 其中1960-1989年为平稳期, 1989-2018年为快速期。(2)白桦次生林径向生长在1989年发生改变, 年轮宽度指数呈现“增长-下降”的“Λ”形生长趋势。(3)在气候变化平稳期, 白桦次生林径向生长在低海拔样地(B1350、B1550)与气温(平均气温、最高气温、最低气温)呈正相关关系, 在高海拔样地(B1750、B1950)与上年和当年生长季降水量呈显著正相关关系; 在气候变化快速期, 低海拔样地(B1350、B1550)白桦次生林径向生长与生长季气温、生长季潜在蒸散发(ET₀)呈负相关关系, 高海拔样地(B1750、B1950)白桦次生林径向生长与生长季及生长季末期ET₀呈负相关关系。 (4)在气候变化平稳期, 温度对B1350、B1550、B1750样地白桦次生林径向生长的贡献率分别为76%、54%、51%, 水分的贡献率为24%、46%、49%; 在气候变化快速期, 温度对B1350、B1550、B1750样地树木径向生长的贡献率分别为58%、41%、38%, 水分的贡献率为42%、59%、62%; 高海拔B1950样地树木生长始终受水分因子的控制。     

北亚热带马尾松年轮宽度与NDVI的关系

北亚热带地处暖温带向亚热带的过渡地区,对环境变化较为敏感。因此,研究北亚热带马尾松年轮宽度与森林NDVI的关系对于揭示陆地生态系统对全球气候变化的响应具有重要意义。以马尾松自然分布北界的南郑县和河南省鸡公山自然保护区为研究地点,利用北亚热带马尾松年轮宽度指数和1982-2006年逐月NOAA/AVHRR的归一化植被指数(NDVI)数据及气候数据,在分析年轮宽度及NDVI与气候因子关系的基础上,重点讨论了北亚热带马尾松径向生长与NDVI之间的关系。结果表明:北亚热带NDVI受水热条件的共同控制,其中与月均温相关性较强,且以正相关为主,与月降水量和干旱度指数多负相关;马尾松的径向生长与上一生长季的温度呈正相关,降水和干旱度指数为负相关,当年生长季内的温度和降水以促进作用为主,而与干旱度指数的关系在两地区内相反;南郑县和鸡公山地区年轮宽度与NDVI年值之间关系均不显著(P>0.05)。单月来讲,南郑县3、4、12月NDVI值与年表显著相关,鸡公山地区9月份的NDVI值与差值年表RES相关性最大;南郑县树木生长受温度影响最大,而鸡公山地区受温度和降水的综合作用。因此,在北亚热带地区,长时间序列的年轮宽度数据并不能很好反应NDVI的长期变化,利用树轮宽度指数来重建北亚热带地区NDVI需要进一步研究。     

Significant Mean and Extreme Climate Sensitivity of Norway Spruce and Silver Fir at Mid-Elevation Mesic Sites in the Alps

Climate forcing is the major abiotic driver for forest ecosystem functioning and thus significantly affects the role of forests within the global carbon cycle and related ecosystem services. Annual radial increments of trees are probably the most valuable source of information to link tree growth and climate at long-term time scales, and have been used in a wide variety of investigations worldwide. However, especially in mountainous areas, tree-ring studies have focused on extreme environments where the climate sensitivity is perhaps greatest but are necessarily a biased representation of the forests within a region. We used tree-ring analyses to study two of the most important tree species growing in the Alps: Norway spruce (Picea abies) and silver fir (Abies alba). We developed tree-ring chronologies from 13 mesic mid-elevation sites (203 trees) and then compared them to monthly temperature and precipitation data for the period 1846–1995. Correlation functions, principal component analysis and fuzzy C-means clustering were applied to 1) assess the climate/growth relationships and their stationarity and consistency over time, and 2) extract common modes of variability in the species responses to mean and extreme climate variability. Our results highlight a clear, time-stable, and species-specific response to mean climate conditions. However, during the previous-year''s growing season, which shows the strongest correlations, the primary difference between species is in their response to extreme events, not mean conditions. Mesic sites at mid-altitude are commonly underrepresented in tree-ring research; we showed that strong climatic controls of growth may exist even in those areas. Extreme climatic events may play a key role in defining the species-specific responses on climatic sensitivity and, with a global change perspective, specific divergent responses are likely to occur even where current conditions are less limited.     

The effect of climate on radial growth of Quercus liaotungensis forest trees in Loess Plateau, China

Annual ring growth of Quercus liaotungensis trees in natural forests bounded by desertified region in the Loess Plateau of China was investigated for the evidence of climatic influence. Increment cores were sampled and cross-dated for 120 trees from six stands 0.5–2.5 km apart. Site tree-ring chronologies were created using general dendrochronological techniques. The results of correlation analyses between tree-ring indices and monthly climatic variables indicated that radial growth was positively correlated with precipitation in September of the previous year and that from April to June of the current year. Ring widths were negatively affected by temperature during spring and summer. In contrast, mild temperature in the previous October showed a positive influence. The results suggest that precipitation is important in the early growing season when soil and air are dry, and that high temperatures tend to reduce radial growth in this region. September rainfalls and a warm October may provide conditions that facilitate carbon storage, favor soil microbial activity, and promote root growth and shoot maturation against detrimental effects of stresses in the following seasons. There were also some differences among plots in the effects of both climatic variables probably as a result of different structures and geographical conditions that modified microenvironments. The results may contribute to the reforestation management of the area. It is expected that Q. liaotungensis forests should be ecologically established in this region on shady and half-shady slopes where air and soil drought stresses are not serious.     

秦岭中西部油松径向生长对气候因子的响应差异研究

在气候变暖背景下,树木径向生长对气候因子的响应会随区域干湿变化而有所差异。秦岭属于气候敏感区和生态脆弱区,南北气候特征差异明显,分析气候变化背景下树木径向生长对气候因子及干旱事件的响应,对准确预测未来气候变化对树木生长的影响至关重要。为探究该地区不同干湿环境下油松对气候因子及干旱事件响应的特点及差异,共采集秦岭中西部南北坡共4个样点的油松树轮样芯,利用树木年轮生态学的方法,分析各地油松年表与气候因子之间的关系,通过计算抵抗力、恢复力、恢复弹力等指标探究树木径向生长对干旱事件的应对能力,结果表明：1)在西部和北坡的3个样点,油松径向生长主要与前一年7—9月、当年5—7月的气温呈显著负相关,与当年5月降水呈显著正相关,在中部南坡油松径向生长主要与当年2—4月、9月气温呈显著正相关,与当年4月降水呈显著负相关;2)生长季气温升高所引发的水分亏缺,是研究区西部和北坡油松径向生长受限制的主要原因,且中部南坡油松生长受气温和干旱因子的制约要明显弱于其它3个样点;3)西部北坡油松对干旱的抵抗能力、恢复能力及恢复弹力均弱于西部南坡及中部北坡油松。在未来对研究区树木的管理与保护工作中,应更加关注西部北坡...     

川西亚高山不同年龄紫果云杉径向生长对气候因子的响应

运用树木年轮气候学的基本方法,建立王朗自然保护区紫果云杉在集中分布上限区域的年轮宽度年表,选取差值年表分析不同年龄云杉的径向生长同逐月气候因子的相关及响应关系,结果显示:幼龄组云杉年表的敏感度高于中龄组和老龄组云杉,幼龄组云杉对生长季前及生长季的气温状况显著正相关;中龄组云杉年表仅与当年4月份和7月份的月平均最低气温显著正相关;老龄组云杉的年轮宽度指数同上年生长季(上年8月份)的月平均气温和月平均最低温显著负相关,上年生长季高温的"滞后效应"在老龄组云杉体现的更为突出;幼龄组与中龄组云杉对当年6月份降水持续增加显示出明显的负相关关系,上年12月份的降水会对幼龄组和老龄组云杉径向生长不利。研究表明幼龄组云杉包含的气候信息要优于中龄组和老龄组云杉,在该区域进行相关研究时应根据研究需要选取不同年龄跨度的云杉年表。