Gender-specific characteristics of tree-ring growth and differential responses to climate change in the dioecious tree Populus cathayana in Xiaowutai Mountains,China

近年来逆境导致植物雌雄幼苗的生长出现差异被许多控制实验所证实, 而有关气候变化对雌雄异株植物成树生长的潜在影响尚未引起人们广泛的关注。为进一步揭示气候变化对雌雄植株树木径向和密度生长的不同影响, 该文通过树轮生态学的研究方法, 选择小五台山天然青杨(Populus cathayana)种群为研究对象, 对青杨雌雄植株近30年(1982-2011)的树轮生长特性及其与气候的相关性进行了分析。结果显示: 1)在近30年当地气温不断升高的气候条件下, 雌株的年轮最大密度和晚材平均密度均高于雄株(p < 0.05), 但雌雄植株的径向生长无显著差异; 2)雌雄植株年轮最大密度和宽度差值年表的变化趋势具有一致性, 但在年轮最大密度差值年表的变化上雄株波动幅度大于雌株; 3)青杨雌雄植株年轮密度差值年表对温度响应的月份明显不同。雌株年轮最大密度与当年8月的月平均最高气温显著正相关, 而雄株年轮最大密度与当年1月和4月的气温负相关; 4)生长季前的气候变化对青杨雌雄植株的径向生长均有明显的限制作用。此外, 当年6月的高温对于早材生长的限制作用特别明显。上述结果表明, 雌雄异株植物在树木年轮生长方面对全球气候变暖可能具有不同的响应机制, 雌株比雄株更侧重于密度生长。     

阿尔泰山西伯利亚落叶松径向生长对气候变化的分异响应

在全球气候变暖的背景下, 北半球中高纬度地区出现了树轮径向生长对气候变化的分异响应现象, 但是阿尔泰山优势针叶树种对气候因子响应的稳定性还存在不确定性。该研究选择阿尔泰山中段高海拔西伯利亚落叶松(Larix sibirica)样本建立了树轮宽度年表, 并对年表特征及树木径向生长-气候的动态关系进行了分析。结果表明: 生长季初期和中期的气温是研究区树木生长的主控气候因子; 树木径向生长与当年4月的气温显著负相关, 与当年6-7月的气温显著正相关; 研究区西伯利亚落叶松径向生长与当年4月和6-7月的气温发生了分异现象, 表现为随着气候变化, 树木径向生长对生长季初期由高温引起的干旱的响应敏感性越来越强, 而对生长季中期气温的敏感性表现出先减弱再增强的趋势。阿尔泰山西伯利亚落叶松径向生长对气候变化的响应比较敏感, 适合开展树木生长-气候变化的研究; 检验树木径向生长对气候变化分异响应为该区域基于树木年轮开展历史气候重建和提高未来森林生态系统发展趋势预测的准确性提供了科学依据。     

东北红豆杉雌雄植株径向生长对邻体竞争和气候因子的响应

通过树木年轮学方法, 研究了树木性别、大小、邻体竞争和气候因子(温度和降水)对东北红豆杉(Taxus cuspidata)径向生长的影响。研究表明, 性别和树木大小对东北红豆杉径向生长影响显著, 雄株的径向生长速率显著大于雌株(p=0.023)。东北红豆杉雌、雄植株径向生长速率均与邻体竞争强度显著负相关(p<0.05), 并且邻体竞争对雌株径向生长的负效应更大。树木气候学分析表明, 东北红豆杉雌、雄植株径向生长对气候因子的响应不同。雌株径向生长量与前一年8月、前一年10月平均温度显著负相关, 雄株径向生长量与月平均温度不显著相关。雌株径向生长量与当年1月的降水量显著负相关, 而雄株径向生长量与当年8月的降水显著负相关。     

阿尔泰山西伯利亚落叶松径向生长对气候变化的分异响应

在全球气候变暖的背景下,北半球中高纬度地区出现了树轮径向生长对气候变化的分异响应现象,但是阿尔泰山优势针叶树种对气候因子响应的稳定性还存在不确定性。该研究选择阿尔泰山中段高海拔西伯利亚落叶松(Larixsibirica)样本建立了树轮宽度年表,并对年表特征及树木径向生长–气候的动态关系进行了分析。结果表明:生长季初期和中期的气温是研究区树木生长的主控气候因子;树木径向生长与当年4月的气温显著负相关,与当年6–7月的气温显著正相关;研究区西伯利亚落叶松径向生长与当年4月和6–7月的气温发生了分异现象,表现为随着气候变化,树木径向生长对生长季初期由高温引起的干旱的响应敏感性越来越强,而对生长季中期气温的敏感性表现出先减弱再增强的趋势。阿尔泰山西伯利亚落叶松径向生长对气候变化的响应比较敏感,适合开展树木生长–气候变化的研究;检验树木径向生长对气候变化分异响应为该区域基于树木年轮开展历史气候重建和提高未来森林生态系统发展趋势预测的准确性提供了科学依据。     

黄连木雌雄植株径向生长的影响因子

采用树木年轮学方法,研究了性别、树木大小及气候因子(温度和降水)对雌雄异株树种黄连木径向生长的影响。结果表明:性别对黄连木径向生长无显著影响(P0.05),树木大小对黄连木径向生长影响显著(P0.05),且不同径级黄连木雌雄植株径向生长速率不同,径级10～15cm黄连木雌树径向生长速率显著大于雄树。与气候因子的相关分析表明,黄连木雌雄植株径向生长与气候因子的关系有一定共性,即均与当年3月的月均最低温度,当年11月的平均温度、月均最高温度和当年5月的月降水量呈显著正相关,而与当年5月的平均温度、月均最高温呈显著负相关;黄连木雌雄植株径向生长对气候因子的响应也存在一定的差异性,其中,雌株径向生长与当年1月平均温度呈显著负相关;黄连木雄树径向生长与当年4月的月均最低温度呈显著正相关,与当年7月的平均温度、月均最高温度呈显著负相关。     

罗霄山南部4个针叶树种生长特征及其气候响应对比分析

为了解影响罗霄山南部树木径向生长的主要气候要素, 该研究运用树木年轮气候学研究方法, 建立罗霄山南部4个针叶树种的树轮宽度标准化年表, 阐明影响该区域4个针叶树种径向生长的主要气候要素, 研究各树种在气温突变前后的径向生长特征及其对气候要素响应的异同。结果表明: 年表特征参数显示, 福建柏(Fokienia hodginsii)与其他树种相比, 其树轮宽度年表所包含的气候信息可能较少。与气候要素的相关分析显示, 铁杉(Tsuga chinensis)的径向生长同时受气温和降水的影响: 与上年10月的降水量呈显著正相关关系, 与气温的响应总体上呈负相关关系; 资源冷杉(Abies beshanzuensis var. ziyuanensis)仅与上年8月的降水量呈显著正相关关系; 马尾松(Pinus massoniana)与上年3月和当年1月的最高气温呈显著正相关关系, 与上年7月和当年8月的最低气温呈显著负相关关系; 福建柏仅与当年3月的降水量呈显著正相关关系。气温发生突变后, 4个树种树轮宽度指数的变化趋势相同, 均呈下降趋势, 除资源冷杉外, 各个树种的径向生长对气候要素的响应总体上有所增强, 且升温后产生的干旱胁迫抑制了各树种的生长。     

雌雄异株植物山杨的气候响应差异

本文通过建立长白山阔叶红松林内雌雄异株植物山杨树轮宽度序列及标准化年表,分析不同气候条件下的生长差异及其与气候因子的关系,以期揭示性别因素对植株径向生长 气候因子关系的影响.结果表明： 不同气候条件下雌雄植株年径向生长速率存在显著差异,对气候因子的响应也有所不同.1980年以前,山杨雌株年均生长速率显著高于雄株,雌株与生长季末低温、上年生长季末和当年生长季降水量呈显著负相关,山杨雄株则与当年生长季温度呈显著正相关.1980年（含）以后,温度明显上升,尤其是最低温度,植株生长速率出现下降趋势,雌株生长速率显著低于雄株;雌株对低温变化更敏感,与上年生长季末低温呈显著负相关、与春季低温呈显著正相关,雄株与低温的相关关系均未达到显著水平.低温对长白山地区山杨雌株生长具有重要影响,在降水基本保持不变的条件下,低温的上升将明显抑制山杨雌株的生长,而对雄株影响不显著.     

长白山东坡不同海拔长白落叶松径向生长对气候变化的响应

为了解高山林线附近树木生长对气候变化的敏感性, 选取长白山东坡火山喷发后形成的过渡性植物群落长白落叶松(又称黄花落叶松) (Larix olgensis)林为研究对象, 并建立不同海拔高度长白落叶松的3个年轮宽度年表, 研究不同生境长白落叶松径向生长对气候变化的响应, 并利用冗余分析对不同海拔的年轮指数与气候因子的关系做进一步分析。主要结果如下: (1)高海拔年轮年表的统计特征更显著, 比低海拔径向生长对气候因子的响应更加敏感; (2)高海拔径向生长主要受上年生长季前期和生长季气温的限制, 尤其是上年6月和8月气温的限制作用, 低海拔径向生长主要与降水量有关, 受当年9月降水量和当年8月帕尔默干旱指数(PDSI)的共同影响; (3)林线内树木对气候响应的敏感性强于林线外, 林线外小生境的异质性及干扰事件频发可能掩盖了树木对气候因子的敏感性, 林线下方可能是检验林线处树木生长对气候响应平均状态的最佳位置; (4)不同海拔年轮年表与气候因子的冗余分析与响应函数分析的结果基本一致, 进一步证明了冗余分析可以有效地量化树轮指数与气候因子的关系。该研究为全球变暖背景下长白山东坡长白落叶松林的管理及该区域气候重建提供了基础数据。     

丛枝菌根真菌对不同性别组合模式下青杨雌雄植株根系生长的影响

丛枝菌根真菌(AMF)对雌雄异株植物根系生长, 尤其是对邻近生长的不同雌雄个体的影响还鲜有研究。该研究以泥土:河沙:蛭石体积比为1:1:1的混合物为培养基质, 分别在雄-雄、雌-雌和雄-雌3种组合栽培模式下对青杨(Populus cathayana)雌雄幼苗进行接种和不接种摩西球囊霉(Funneliformis mosseae)处理, 通过比较接种AMF与否雌雄植株根系在侵染率、生物量、形态、碳、氮含量等方面的差异来分析AMF对青杨雌雄幼苗根系生长发育的影响。结果发现: 与对照组相比, 接种AMF对3种栽培模式下青杨雌雄植株的侵染率、根干质量、根系形态(除分枝强度、比表面积)和碳、氮含量影响显著。此外, 不同性别组合模式对青杨雌雄植株的根干质量、根系形态和碳、氮含量影响显著。接种AMF后, 与雌-雌合栽模式下的雌株相比, 雄-雌合栽模式下雌株的根干质量、氮含量都有不同程度的提高, 根系形态发生改变; 而与雄-雄合栽模式下的雄株相比, 雄-雌合栽模式下雄株的相应指标出现降低或轻微增加。该研究表明AMF对不同性别组合模式下青杨植株根系生长具有显著促进作用, 尤其是雄-雌合栽模式下AMF接种最有利于雌株根系的生长发育。     

小五台山天然青杨林雌雄群体的生长差异

通过对小五台山天然青杨种群的野外调查,并使用胸径与株高的异速生长模型来分析其雌雄群体间的生长差异,以探究雌雄异株植物青杨在性成熟条件和形态特征中是否存在性间差异。结果表明:(1)在青杨生长过程中,胸径随年龄呈指数型增长,而株高随年龄呈对数型增长;(2)雌雄植株的性成熟条件不同。雌株进入性成熟阶段的最低年龄和胸径都小于雄株;(3)青杨高径生长过程存在性别差异。雌株的异速生长指数显著大于雄株(P=0.024)。表明天然青杨种群中雌株一般性成熟较早,成熟后营养生长偏重于胸径增粗;而雄株性成熟较晚,营养生长偏重于植株增高。相对于雄株,雌株具有较高的树干机械强度。     

中国祁连山西段青海云杉树轮密度记录的气候信号

树轮气候学是研究过去气候变化的重要手段之一。以往研究表明,树轮密度是生长季温度的重要代用资料。本文建立了祁连山西段青海云杉132～135年的树轮最大密度年表、树轮最小密度年表、树轮晚材平均密度年表和树轮早材平均密度年表,比较了不同密度年表指示的最优气候信号及其季节组合,评估了其作为气候代用资料的潜力与价值。结果表明:树轮晚材平均密度和树轮早材平均密度对于树木生长季气候信号的响应远低于树轮最大密度和树轮最小密度;树轮早材平均密度和树轮最小密度与帕尔默干旱指数有很强的联系,表明树轮早材平均密度和树轮最小密度有成为干旱代用指标的潜力。     

黑龙江漠河兴安落叶松与樟子松树轮生长特性及其对气候的响应

树木年轮 (简称树轮 ) 气候学是监测与重建全球气候变化的重要方法之一。针叶树树轮的生长能反馈出气温的变化, 在高纬度地带尤为明显。该文分析了生长在我国最北部的兴安落叶松 (Larixgmelinii) 与樟子松 (Pinussylvestrisvar.mongolica) 的树轮密度和宽度的特性。落叶松最大密度、晚材平均密度、早晚材宽度和轮宽都远高于樟子松。樟子松的所有密度变量的样本方差都明显高于兴安落叶松, 宽度变量的样本方差却明显低于兴安落叶松。两树种密度变量的差值年表显著相关, 宽度变量之间没有显著相关关系。落叶松与樟子松的晚材密度的形成受 7、8月的最高温控制。另外, 樟子松的晚材还与生长季节的长短相关。落叶松的年轮宽度对生长季节开始前的温度敏感, 而樟子松的轮宽对气候变量没有很好的响应。结果表明, 落叶松与樟子松的树轮最大密度都与生长季后期的温度显著相关, 两树种的树轮信息对气候变化的重建有很大的潜力。     

A tree-ring densitometric transect from Alaska to Labrador

We describe a recently completed network of densitometric tree-ring time series representing various aspects of tree-growth for up to 200 years at 69 sites spread across the northern North American conifer zone from Yukon to Labrador. Duplicate cores, from 12 to 15 trees per site, provide time series for a suite of growth parameters including earlywood (spring), latewood (summer) and total (annual) ring widths and mean earlywood, mean latewood, minimum and maximum ring density. These data form the basis for extensive analyses of intra- and inter-site parameter comparisons and regional climate/tree-growth comparisons. Five large-scale regional chronologies do not suggest that any anomalous growth increases have occurred in recent decades, at least on these regional scales, despite the observed changes in atmospheric composition and climate.     

Climate–tree growth relationships of longleaf pine (Pinus palustris Mill.) in the Southeastern Coastal Plain, USA

Knowledge of tree growth/climate response relationships is important to dendroecological studies and dendroclimatic reconstructions, particularly in the Southeastern Coastal Plain where few such studies have been attempted. To this end, we developed tree-ring chronologies of total ring width, earlywood width, and latewood width from longleaf pine (Pinus palustris Mill.) at three sites in the Southeastern Coastal Plain to examine the climate–growth relationships for this tree species. The length of these chronologies is unprecedented for southern pine chronologies in the Southeast. We compared the tree-ring chronologies to monthly temperature, precipitation, Palmer drought severity index (PDSI), and Palmer hydrological drought index (PHDI) data from the pertinent climate divisions. We found that PDSI and PHDI have the highest correlation with longleaf pine growth, and the strongest relationships between longleaf pine growth and these variables occur between July and November. Precipitation in the spring and summer was also positively related to growth at all sites. The relationship between temperature and growth was the weakest among all climate variables, but warm summer temperatures had a consistent, negative relationship with longleaf pine growth. The climate signal in the latewood was generally more robust than for total ring width and earlywood width.     

X-ray microdensitometry applied to subfossil tree-rings: growth characteristics of ancient pines from the southern boreal forest zone in Finland at intra-annual to centennial time-scales

A collection of subfossil wood of Pinus sylvestris (Scots pine) was exposed to X-ray densitometry. The collection of 64 samples from the southern boreal forest zone was dendrochronologically cross-dated to a.d. 673-1788. Growth characteristics were determined by performing density profiles including the following parameters: minimum density, earlywood and latewood boundary density, maximum density, earlywood width, earlywood density, latewood width, latewood density, annual ring width and annual ring density. Seven out of the nine parameters were found to contain non-climatic growth trends and six were found to be heteroscedastic in their variance. Tree-specific records were indexed, to remove the non-climatic growth trends and stabilize the variance, and combined into nine parameter-specific tree-ring chronologies. Growth characteristics of the pines changed in parallel with the generally agreed climatic cooling from the Medieval Warm Period to the Little Ice Age: pine tree-rings showed decreasing maximum densities from the period a.d. 975-1150 to a.d. 1450–1625. A concomitant change in the intra-annual growth characteristics was detected between these periods. The findings indicate that not only the trees growing near the species’ distributional limits are sensitive to large-scale climatic variations but also the trees growing in habitats remote from the timberline have noticeably responded to past climate changes.     

太行山南麓不同径级栓皮栎生长对气候要素及干旱事件的响应

为评估径级对树木的气候-生长关系的影响,建立太行山南麓低海拔地区栓皮栎全轮、早材、晚材宽度年表,对比两个径级栓皮栎人工林径向生长对气候响应的敏感性差异,使用叠加时代分析揭示干旱事件对不同径级栓皮栎的影响,为气候变化背景下研究区栓皮栎人工林可持续经营提供参考数据。结果表明: 大径级栓皮栎全轮、晚材年表的平均敏感度高于小径级栓皮栎年表,但小径级栓皮栎早材年表的平均敏感度高于大径级栓皮栎早材年表。晚材是树轮气候响应最敏感的组分。两径级栓皮栎标准年表指数对当年气候因子的响应模式相似。小径级栓皮栎全轮、晚材生长对当年6—8月的气候因子更敏感,其早材对生长季之前(1—2月)气候因子更敏感;而大径级栓皮栎早材对去年的气候因子更敏感,有更强的滞后效应。研究区栓皮栎对干旱非常敏感,干旱年份两径级栓皮栎全轮、晚材的径向生长量显著低于上一年,且大径级栓皮栎的减少幅度更高,但干旱后大径级栓皮栎生长恢复程度更高。     

Linkages between forest growth,climate, and agricultural production are revealed through analysis of seasonally-partitioned longleaf pine (Pinus palustris Mill.) tree rings

We established a five-century long tree-ring chronology partitioned between earlywood and latewood growth to examine intra-annual climate response and attempt to establish linkages to agricultural production. Longleaf pine earlywood and latewood width chronologies spanned the period 1491–2017 (527 years) and constitute one of the longest records achieved for this species. High monthly correlations were found between latewood growth and summer-fall Palmer Drought Z-Index. Correlations were consistently significantly positive for June through October. Intra-annual growth of earlywood and latewood were positively correlated for the full period of record, but exhibited variability in correlation strength through time. Conversely, earlywood and prior-year latewood were also frequently correlated, but correlations were found to switch between positive and negative association, possibly in response to Atlantic Ocean temperatures. Annual yields of major crops are coupled with latewood growth, representing a new and potentially valuable proxy for linking agricultural yields to climate proxies over multiple centuries.     

Tree-ring growth and intra-annual density fluctuations of Pinus pinaster responses to climate: does size matter?

Dendroclimatology generally assumes that climate–growth relationships are age and size independent. However, there is evidence that climate response can be unstable across different age/size classes. In addition, the occurrence of some anatomical features, such as intra-annual density fluctuations (IADFs), is age dependent. The present study investigates whether the climate–growth responses and the occurrence of IADFs in an even-aged stand of Pinus pinaster Ait., growing under Mediterranean climate, are also size-dependent. We randomly selected 60 P. pinaster trees falling within two stem diameter classes: small (<27 cm) and large (>35 cm). Tree rings were crossdated, measured and IADFs identified according to their position within the ring. The residual chronologies of both size classes were strongly correlated, suggesting a common signal. In fact, similar growth–climate relationships were observed in large and small trees. The frequency of IADFs was higher in large than in small trees, suggesting that IADFs were more likely to occur in wider rings of fast-growing trees. In both size classes, most of the IADFs were found in latewood. Latewood IADFs were triggered by the combination of dry June, wet September, and warm December, whereas IADFs located at the end of earlywood were triggered by previous winter precipitation and favorable conditions before summer (high precipitation for large trees and lower temperature for small trees). Our results suggest that IADFs can be a mechanism used at the individual level for adaptation to drought in P. pinaster. The climatic signal of IADFs between earlywood and latewood was mediated by stem size suggesting that future tree-ring studies should include trees stratified by size to better estimate the sensitivity of IADFs to climate.     

Dendroclimatic signals deduced from riparian versus upland forest interior pines in North Karelia, Finland

Radial growth of boreal tree species is only rarely studied in riparian habitats. Here we investigated chronologies of earlywood, latewood, and annual ring widths and blue intensity (BI; a surrogate to latewood density) from riparian lake shore and upland forest interior pines (Pinus sylvestris L.) growing in boreal forest in eastern Finland. Riparian and upland chronologies were compared to examine differences in the pine growth variability and growth response to climatic variation in the two habitats. It was found that the climatic variables showing statistically significant correlations with the tree-ring chronologies were related to snow conditions at the start of the growing season. Deeper snowpack led to reduced upland pine growth, possibly due to delayed snowmelt and thus postponed onset of the growing season. Warm late winters were followed by increased riparian pine growth because of earlier start of the snow-melt season and thus a lower maximum early summer lake level. Moreover, riparian pines reacted negatively to increased rainfall in June, whereas the upland pines showed a positive response. Latewood growth reacted significantly to summer temperatures. The BI chronology showed a strong correlation with warm-season temperatures, indicating an encouraging possibility of summer temperature reconstruction using middle/south boreal pine tree-ring archives.