昌岭山两个优势树种径向生长对气候变化的响应

在气候变暖背景下,树木径向生长对气候变化的响应存在不稳定性。利用采自祁连山东部余脉昌岭山两个优势树种油松和青海云杉的树轮样芯,建立树轮宽度标准年表,通过分析树轮宽度年表与气候要素的相关关系,探讨两个树种径向生长对气候变化的响应。结果表明：（1）油松年表比青海云杉年表包含更多的气候信息,其平均敏感度、标准差、信噪比和样本对总体的代表性等统计量均高于青海云杉标准年表。（2）气候要素对不同树种径向生长限制程度不同,油松径向生长主要与降水（前一年9月和当年3-8月）和气温（前一年9月）有关,但对降水的响应更为敏感,而青海云杉径向生长则受到气温（当年9月）和降水（前一年9月、当年3月和7月）的共同作用。（3）气温突变后,油松和青海云杉年表与各气温要素的相关性显著增强,而青海云杉年表与气温要素的相关性变化更明显,指示了青海云杉径向生长对气温的响应更不稳定。（4）生长季平均最低气温的升高诱导的干旱胁迫是油松和青海云杉树木径向生长-气温响应变化的主要原因。     

Host and non-host odour signals governing host selection by the pine shoot beetle, Tomicus piniperda and the spruce bark beetle, Hylurgops palliatus (Col., Scolytidae)

Abstract:  Tomicus piniperda and Hylurgops palliatus colonize susceptible host trees by responding to host-specific odour signals as well as by avoiding volatiles emanating from non-host conifers. In the field, the pine shoot beetle, T. piniperda , responded in high numbers to natural odour sources provided by their host tree, Pinus sylvestris , while the non-host conifers Larix decidua , Picea abies , or Pseudotsuga menziesii were significantly less attractive. In contrast, the spruce bark beetle, Hylurgops palliatus , preferentially responded to its main host, P. abies . Furthermore, T. piniperda attacks on P. sylvestris bolts decreased in presence of bark and wood particles from the non-host P. abies , whereas particles from P. menziesii appeared not to affect T. piniperda attacks. Apparently, tree-specific volatiles act at close range as specific signals that lead to the successful discrimination and colonization of the respective host tree species.     

Response of juveniles of seven forest tree species and their populations to different combinations of simulated climate change-related stressors: spring-frost,heat, drought,increased UV radiation and ozone concentration under elevated CO2 level

Journal of Plant Research - The study aimed to assess response of juvenile progeny of seven forest tree species, Pinus sylvestris, Picea abies, Betula pendula, Alnus glutinosa, Populus tremula,...     

Radial growth response of Pinus densiflora and Quercus spp. to topographic and climatic factors in South Korea

Aims This study aimed to develop radial growth models and to predict the potential spatial distribution of Pinus densiflora (Japanese red pine) and Quercus spp. (Oaks) in South Korea, considering topographic and climatic factors.Methods We used a dataset of diameter at breast height and radial growth estimates of individual trees, topographic and climatic factors in systematic sample plots distributed over the whole of South Korea. On the basis that radial growth is attributed primarily to tree age, we developed a radial growth model employing tree age as an explanatory variable. We estimated standard growth (SG), defined as radial growth of the tree at age 30, to eliminate the influence of tree age on radial growth. In addition, SG estimates including the Topographic Wetness Index, temperature and precipitation were calculated by the Generalized Additive Model.Important findings As a result of variogram analysis of SG, we found spatial autocorrelation between SG, topographic and climatic factors. Incremental temperature had negative impacts on radial growth of P. densiflora and positive impacts on that of Quercus spp. Precipitation was associated with positive effects on both tree species. Based on the model, we found that radial growth of P. densiflora would be more vulnerable than that of Quercus spp. to climatic factors. Through simulation with the radial growth model, it was predicted that P. densiflora stands would be gradually replaced with Quercus spp. stands in eastern coastal and southern regions of South Korea in the future. The models developed in this study will be helpful for understanding the impact of climatic factors on tree growth and for predicting changes in distribution of P. densiflora and Quercus spp. due to climate change in South Korea.     

Recent cooling and recession of Norway spruce (Picea abies (L.) Karst.) in the forest—alpine tundra ecotone of the Swedish Scandes

Abstract. Repeated crown condition surveys, 1974–94, of subalpine clonal groups of Norway spruce ( Picea abies (L.) Karst.) were carried out in the Swedish Scandes. Complementary analyses concerned radial and vertical growth, sexual regeneration and range limit responses of other plant species. Significant defoliation of spruce progressed linearly over the period of study, reaching cumulative values of about 85%. It is inferred that defoliation was preconditioned by decreasing radial growth since the thermal climax in 1937 and was proximately initiated by the extremely cold winter of 1965/66 and paralleled by consistently declining radial growth and staggering vertical increase. It appears that severe and prolonged ground freezing invoked winter desiccation (xylem cavitation), extensive needle loss and reduced radial growth. Hypothetically, from circumstantial evidence, these processes are interrelated in a positive feedback system, implying increasing sensitivity to climatic stress and decreasing ability to take advantage of positive climatic anomalies. Thus, the total demise of the supranival stems is cautiously predicted, by linear regression of the 20-yr defoliation pattern, to be less than a decade ahead. The recession of P. abies , clearly relevant in a landscape perspective, conforms with analogous responses of Pinus sylvestris L. and Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman and a significant altitudinal range-limit retraction of certain silvine field-layer species. The structural development examined in this study concurs with long-term climate cooling and cold events and strongly contrasts with simulations of the performance of this system in response to a putative enhanced'greenhouse'effect.     

Tree growth response to drought and temperature in a mountain landscape in northern Arizona, USA

Aim To understand how tree growth response to regional drought and temperature varies between tree species, elevations and forest types in a mountain landscape. Location Twenty‐one sites on an elevation gradient of 1500 m on the San Francisco Peaks, northern Arizona, USA. Methods Tree‐ring data for the years 1950–2000 for eight tree species (Abies lasiocarpa var. arizonica (Merriam) Lemm., Picea engelmannii Parry ex Engelm., Pinus aristata Engelm., Pinus edulis Engelm., Pinus flexilis James, Pinus ponderosa Dougl. ex Laws., Pseudotsuga menziesii var. glauca (Beissn.) Franco and Quercus gambelii Nutt.) were used to compare sensitivity of radial growth to regional drought and temperature among co‐occurring species at the same site, and between sites that differed in elevation and species composition. Results For Picea engelmannii, Pinus flexilis, Pinus ponderosa and Pseudotsuga menziesii, trees in drier, low‐elevation stands generally had greater sensitivity of radial growth to regional drought than trees of the same species in wetter, high‐elevation stands. Species low in their elevational range had greater drought sensitivity than co‐occurring species high in their elevational range at the pinyon‐juniper/ponderosa pine forest ecotone, ponderosa pine/mixed conifer forest ecotone and high‐elevation invaded meadows, but not at the mixed conifer/subalpine forest ecotone. Sensitivity of radial growth to regional drought was greater at drier, low‐elevation compared with wetter, high‐elevation forests. Yearly growth was positively correlated with measures of regional water availability at all sites, except high‐elevation invaded meadows where growth was weakly correlated with all climatic factors. Yearly growth in high‐elevation forests up to 3300 m a.s.l. was more strongly correlated with water availability than temperature. Main conclusions Severe regional drought reduced growth of all dominant tree species over a gradient of precipitation and temperature represented by a 1500‐m change in elevation, but response to drought varied between species and stands. Growth was reduced the most in drier, low‐elevation forests and in species growing low in their elevational range in ecotones, and the least for trees that had recently invaded high‐elevation meadows. Constraints on tree growth from drought and high temperature are important for high‐elevation subalpine forests located near the southern‐most range of the dominant species.     

Tricholoma matsutake Y1 strain associated with Pinus densiflora shows a gradient of in vitro ectomycorrhizal specificity with Pinaceae and oak hosts

Tricholoma matsutake produces commercially valuable yet uncultivable matsutake mushrooms during an ectomycorrhizal association with coniferous trees. In the Far East, most matsutake are harvested in managed Pinus densiflora forests. To determine whether T. matsutake has host plant specificity, we synthesized mycorrhiza in vitro between T. matsutake Y1 that originated from a P. densiflora forest and various Pinaceae and oak hosts. The strain Y1 formed a continuous Hartig net, a sign of ectomycorrhization, in the lateral roots of Pinus sylvestris, Pinus koraiensis, Pinus parviflora var. pentaphylla, Picea glehnii, Picea abies, and Tsuga diversifolia seedlings in vitro, which resembled those formed with the natural host Pinus densiflora. The strain conferred a discontinuous Hartig net with Pinus thunbergii, Picea yezoensis, Abies veitchii, and Larix kaempferi. However, no such development by this strain was observed on the roots of Quercus serrata, unlike T. bakamatsutake B1, a false matsutake that is symbiotic with oak trees. The data suggest that T. matsutake can be associated with diverse conifers but may establish ectomycorrhizal relationships only with specific host plant species.     

Myxomycetes developed on litter of common Finnish trees in moist chamber cultures

Fallen leaves were collected from the Finnish trees Alnus gtutinosa & A. incana, Betula pendula & B. pubescens, Picea abies, Pinus sylvestris and Populus tremula , and used to establish 400 moist chamber cultures. From these emerged 132 specimens of Myxomycetes belonging to 14 species. One of them, Didymium dubium Rostaf. was also cultivated from spore to spore in artificial media. The three Arcyria species that emerged developed only on coniferous litter and the four Didymium species only on deciduous litter. Echinostelium minitum de Bary is the only myxomycete species that emerged on leaves of all the five trees.
Alnus litter gave rise to the greatest number of myxomycete specimens. Betula leaves seemed to be the most unfavourable of the substrates. The common species of Myxomycetes that have appeared only on bark of living trees in the moist chambers set up by the author include Paradiacheopsis fimbriata (G. Lister & Cran) Hertel and P. solitaria (Nann.–Brem.) Nann.–Brem. Species occurring only on deciduous leaves or grains are Didymium difforme (Pers.) S. F. Gray, D. dubium Rost. and D. squamulosum (Alb. & Schw.) Fr.     

Variation in tree growth sensitivity to moisture across a water-limited forest landscape

Water availability acts as a major constraint on productivity in many sub-humid forest regions. Precipitation can be an important limiting factor for tree growth in such areas, but the strength of the relationship can vary by habitat and species, as well as with tree size and local hydrology. We quantified the influence of past weather conditions on the growth of two conifer species (Pinus contorta and Picea glauca) across a water-limited forest landscape in western Canada. The two species differ in moisture requirements and are segregated across a local elevational gradient, and so we expected them to exhibit different sensitivities to precipitation. We also expected that larger trees and those more distant from creeks would have a stronger response to precipitation. A hierarchical Bayesian model fit to the annual ring widths of 387 trees showed that historical precipitation from 1951 to 2016 had a positive overall effect on radial growth. The magnitude of precipitation effects on radial tree growth varied with creek proximity (a proxy for the soil moisture provided by an elevated water table in the valley bottom) and tree size. Precipitation had a greater positive influence on the growth of larger P. glauca trees, as well as individuals of both species at far and intermediate distances from creeks. Precipitation had a weaker but still positive effect on P. glauca trees growing close to creeks. Tree growth rates may change with the predicted greater inter-annual variability of precipitation under climate change, but the magnitude of these responses appear to vary by species, size, and creek proximity. Overall changes in tree growth are expected to be relatively small as trees are well-adapted to cope with the variation in water availability across a moisture-limited landscape.     

Occurrence of epiphytic macrolichens in relation to tree species and age in managed boreal forest

For the maintenance of biodiversity some epiphytic macrolichens have been used to identify forests with high conservation value. To understand what these macrolichens indicate, we studied the relationships of tree species and age with the abundance of a set of 33 macrolichens (20 of them in use as indicator species) at 90 localities in a 150 km² area in south-central Sweden.
We sampled the four most common tree species Scots pine Pinus sylvestris. Norway spruce Picea abies , birch Betula spp, and aspen Populus tremula for macrolichens at 0-2 m from the base. Of the 33 target species we found 17, six of them were indicators in use for this region. In 30, out of 40 tested, cases there was a positive relation between lichen abundance and age of the tree.
On all tree species the number of the studied lichen species increased with age. The colonisation rate of the species was fastest on birch. All species occurring on birch were also found on at least one of the coniferous trees, while aspen had six species not found on other trees. Pine and spruce with a slow growth rate had more signal lichen species than fast growing trees.
We could not detect a competitive situation between common and rare species as the most abundant or largest lichens did not exclude other species. The length of the longest fruticose lichen was positively correlated with the number of species on the tree. Shade had a negative effect on the number of species.
We conclude that the indicator macrolichens encountered in this study showed a preference for old trees or aspens. This result, and the low number of indicator species, points at the importance of promoting these trees for the preservation of biodiversity in the boreal forest.     

Subalpine tree growth on serpentine soil: a dendroecological analysis

In this study dendrochronological methods are used to investigate tree growth of several coniferous species growing on serpentine outcrops in the subalpine region. Though stands are thriving on the same parent material, almost barren sites covered with Scots pine trees (Pinus sylvestris/ L.) contrast sharply with adjacent dense stands composed of mixed coniferous species. To find a reasonable explanation for this vegetation pattern and to evaluate the influence of serpentine soil on radial tree growth annual variability in ring-widths was analyzed and compared between both types of stands. Tree-ring analyses show that sparse tree cover on steep slopes might be caused by environmental stress factors especially unfavourable physical soil properties such as instability and dryness. Several abrupt growth reductions followed by slow release in ring-widths indicate repeated mechanical injury to the root system due to soil erosion. On the other hand the aggravating impact of anthropogenic disturbances (tree felling) on this ecologically fragile serpentine area could be determined and dated. There was no evidence that radial tree growth of coniferous species at this site could be limited by toxic heavy metals in the soil.     

河北塞罕坝樟子松径向生长动态变化及其与气象因子的关系

树木是森林生态系统的基本组成, 其生长受气象因子的影响, 基于此, 该研究通过监测樟子松(Pinus sylvestris var. mongolica)的径向生长, 研究樟子松生长日动态规律、季节动态规律及其与气象因子的关系, 探讨河北塞罕坝地区樟子松森林生态系统对气候变化的响应机制。此外, 以往研究树木生长大多数基于树轮年代学, 缺少短期树木径向生长动态的研究。该研究利用径向生长记录仪监测河北塞罕坝机械林场内樟子松连续3年(2016-2018)的树干径向动态变化。结果表明: 由于树干的水分吸收与蒸腾作用, 樟子松树干径向昼夜变化呈现季节性规律, 可划分为4个阶段: 春季萌动期、夏季生长期、秋冬交替期和冬季休眠期。塞罕坝樟子松树干径向生长开始于每年4月初; 4月初至5月中旬为水分恢复阶段; 5月中旬至7月中旬为快速生长阶段; 7月中旬至10月中旬为缓慢生长阶段; 10月中、下旬生长趋于停止, 并有树干径向收缩现象。以一天为时间尺度, 在快速生长阶段(5月初至7月中旬)樟子松径向生长主要受空气温度的影响; 缓慢生长阶段(7月中旬至10月下旬)降水量、空气温度均影响樟子松径向生长。以15天为时间尺度, 温度对樟子松径向生长的影响显著。结果显示樟子松的生长动态规律及其影响因子, 为未来樟子松生理研究提供参考时间节点, 同时在极端低温与干旱的情况下, 为半干旱地区樟子松的生长状态提供参考依据。     

大兴安岭山地樟子松径向生长对气候变暖的响应——以满归地区为例

基于树木年代学的理论和方法,建立了大兴安岭满归地区樟子松年轮宽度年表,分析了标准化年表与该区主要气候因子(温度和降水)之间的相关关系,揭示了气候因子对树木径向生长的影响.结果表明:当年4-8月的各月平均温度是研究区樟子松径向生长的主要限制因子;4-8月各月温度的不断升高对樟子松径向生长产生了不利影响.利用4-8月平均温度的变化模拟樟子松径向生长变异(1958 -2008年),发现随着区域气候暖干化趋势的加强,该区樟子松生长将呈现出衰退的特征.     

Size-dependent responses to summer drought in Scots pine, Norway spruce and common oak

In this study, we provide a detailed analysis of tree growth and water status in relation to climate of three major species of forest trees in lower regions of Bavaria, Southern Germany: Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and common oak (Quercus robur). Tree-ring chronologies and latewood δ¹³C were used to derive measures for drought reaction across trees of different dimensions: growth reduction associated with drought years, long-term growth/climate relations and stomatal control on photosynthesis. For Scots pine, growth/climate relations indicated a stronger limitation of radial growth by high summer temperatures and low summer precipitation in smaller trees in contrast to larger trees. This is corroborated by a stronger stomatal control on photosynthesis for smaller pine trees under average conditions. In dry years, however, larger pine trees exhibited stronger growth reductions. For Norway spruce, a significantly stronger correlation of tree-ring width with summer temperatures and summer precipitation was found for larger trees. Additionally, for Norway spruce there is evidence for a change in competition mode from size-asymmetric competition under conditions with sufficient soil water supply to a more size-symmetric competition under dry conditions. Smaller oak trees showed a weaker stomatal control on photosynthesis under both dry and average conditions, which is also reflected by a significantly faster recovery of tree-ring growth after extreme drought events in smaller oak trees. The observed patterns are discussed in the context of the limitation-caused matter partitioning hypothesis and possible species-specific ontogenetic modifications.     

长白山红松和鱼鳞云杉在分布上限的径向生长对气候变暖的不同响应

用树木年代学方法研究了近50年来气候变化对长白山自然保护区两种广泛分布的重要乔木树种红松(Pinus koraiensis)和鱼鳞云杉(Picea jezoensis var. komarovii)分布上限树木径向生长的影响, 发现红松年轮宽度具有与温度升高相一致的趋势, 而鱼鳞云杉年轮宽度则出现随温度升高而下降的“分离现象”。对水热条件的正响应是分布上限红松年表与温度保持一致的关键: 生长季的温度和降水的增加对上限红松的生长有促进作用, 且二者对树木生长的有利效应有相互促进的现象; 生长季的延长也有利于红松的生长。升温导致的水分胁迫是造成上限分布的鱼鳞云杉年轮宽度与温度变化趋势相反的重要因素: 分布上限的鱼鳞云杉年表与大多数温度指标均呈负相关关系; 随着温度升高, 年表与年降水量尤其是春季降水量的相关性逐渐由负转正; 各月的高温以及生长季中后期的少雨是形成上限鱼鳞云杉窄轮的主要气候因素, 而较低的各月温度以及生长季后期充足的降水则有利于上限鱼鳞云杉的生长; 此外, 生长季长度没有变化也可能是造成鱼鳞云杉年表序列对温度变化敏感性下降的重要因素。     

关帝山云杉次生林树木径向生长的空间关联及其影响因子

以关帝山4 hm²云杉次生林样地为研究对象,按照CTFS(Center for Tropical Forest Science)技术规范对样地树木进行连续定位监测。利用2010至2015年间样地主要树种生长量观测数据,结合地形、土壤等环境因子调查及采样测定数据,分析了树木种群径向生长的空间关联性及其随生境的变化,并探讨了树木种群径向生长的影响因素。结果表明,青杄、华北落叶松、红桦、白桦和辽东栎为云杉次生林主要树种,在样地4个生境型(山脊生境、低海拔缓坡生境、高海拔缓坡生境、低洼地陡坡生境)中均有分布且呈现不同的径级结构。标记相关函数分析显示,同一生境型中,5树种径向生长的空间关联性各异;对于同一树种,径向生长的空间自相关性不仅具有尺度依赖性,同时生境型的不同导致树木径向生长的空间关联性发生变化。线性混合效应模型分析显示,初始胸径对树木径向生长的显著正效应在样地各类生境型的所有种群中普遍存在;生物因子对树木径向生长的显著影响只在特定生境型的青杄种群中被检测到,表明树木径向生长受同种邻体影响,但其影响显著性因树种而异;环境因子中,海拔和凹凸度对树木径向生长呈显著负效应...     

The fate of alien conifers in long-term plantings in the USA

For more than 100 years, non-native conifers have been introduced into habitats in the USA that already support native conifers. These introductions have yielded few naturalizations and even less evidence of invasions. We investigated the specific fates of nine non-native conifers in an array of introduction sites across the USA (Priest River, Idaho, Wind River, Washington, Cedar Creek, Minnesota, and Nantucket Is. and Martha's Vineyard, Massachusetts) through tree-ring analyses, comparisons of growth with adjacent native conifer populations, and surveys for regeneration and spread. Most of the original non-native tree plantings have died (e.g. Abies veitchii , Pinus densiflora , and Pinus halepensis at Wind River, WA); a few have survived but display low vigour and are not regenerating (e.g. Larix decidua , Pinus mugo , and Picea abies stands at Priest River, ID). Pinus sylvestris recruitment is apparent at all sites examined. Pinus thunbergii appears to be invasive on Nantucket Is., although the native Bursaphelenchus xylophilus (pinewood nematode) causes high mortality in mature trees. Non-native Pinus spp. at the Eddy Arboretum, California and Pack Forest, Washington also experienced high mortality. Dendroclimatic analyses revealed no difference in the effect of climate on the annual growth of native and non-native conifers. Plantations of introduced conifers in the south-eastern USA have died en masse (e.g. Harrison Experimental Forest, Mississippi, Olustee Arboretum, Florida). Such widespread extirpations are in sharp contrast to the fate of native conifers in adjacent stands as well as the multiple cases of large-scale conifer invasions in the Southern Hemisphere. Given the diversity of alien plant species that have invaded the USA, the circumstances surrounding the lack of persistence of introduced conifers becomes an important line of inquiry for understanding the factors and circumstances that facilitate or thwart biological invasions.     

Parameter-specific hydroclimatic sensitivity of a low-elevation network of living and historical tree-ring series from north-eastern Austria

Compared to the alpine regions of Austria, the eastern part of the country is overall warmer and drier with some tree species growing at the dry limit within their ecological range. This suggests that tree rings may be a valuable proxy for hydroclimatic variability. In this study, we develop ring-width, earlywood-width and latewood-width chronologies obtained from drought sensitive living trees and historical timber from one of the driest and warmest regions of Austria, the Weinviertel. For this, samples of four different tree species − fir (Abies alba Mill.), spruce (Picea abies (L.) Karst.), oak (Quercus petraea Liebl., Q. robur L., Q. cerris L.), and pine (Pinus sylvestris L., P. nigra Arnold) were collected from 88 sites (23 forest stands and 65 historical constructions). 1589 samples (oak: 592 samples, pine: 577, spruce: 212, fir: 208) were dated. Dendro-provenancing was required to ensure that only regional material has entered the chronologies. According to the analyses, historical pine and oak wood were nearly 100% regional, while spruce and fir wood were imported to a great extent with only 44% spruce and 35% fir confirmed to be regional. Because site conditions of historical wood samples are unknown but can have a significant influence on tree growth, changes to site replication over time were important in the assessment of chronology reliability. We also controlled for potential artificial increases in sample depth when more than one construction element is made from a single trunk.We assessed the pine (1584-2011 AD) and oak (1244-2011 AD) chronologies’ potential for reconstructing past hydroclimatic variability by means of response functions in a 17-months window from previous June to current October with climate data from three weather stations (Vienna, Retz, Brno) from 1897 to 2010 AD. The highest seasonal response coefficients are for oak and pine ring width (∼0.43) with respect to aggregated March to July precipitation totals and Thornthwaite climatic water balance. These chronologies reveal a high potential for estimating past changes in regional-scale moisture availability during the earlier growing season.     

Climatic effect of atmospheric CO2 doubling on radial tree growth in south eastern France

The climatic effect of a doubling of atmospheric CO₂ on radial growth of trees was studied in ten populations of three species in south eastern France using an Atmospheric General Circulation Model (AGCM) predicting a 3°C increase of mean temperature and a light rise of precipitation. Results are based on empirical growth climate models, involving an Artificial Neural Network (ANN) technique. Only two of the studied populations, on the boundaries of their ecological area, are sensitive to the climatic variations. One is the larch ( Larix decidua Mill.) population located at 2300 m on elevation (near the timberline) which shows a radial growth increase. The other is the most southern French Scots pine ( Pinus sylvestris L.) population which reacts with a severe growth rate reduction.     

Changes in environmental controls on the growth of Abies alba Mill. in the Vosges Mountains, north-eastern France, during the 20th century

Aim  To analyse the radial growth of silver fir ( Abies alba Mill.) in north-eastern France in relation to soil, climate and interspecific competition factors and to check the temporal stability of their effects during the 20th century.
Location  The Vosges Mountains, located in north-eastern France.
Methods  Data were collected from 143 plots regularly distributed over three altitude ranges (from 330 to 1100 m), three humus forms (moder to mull) and seven types of stands, including a pure stand of silver fir and six mixed stands containing this species. For each plot, an index of mean radial growth of silver fir was calculated, independent of tree age and calendar year of ring formation. Relationships between radial growth and ecological factors were analysed using linear mixed-effects models.
Results  Radial growth of silver fir is low in the presence of Picea abies or of a high density of other dominant trees . Low aluminium concentration and good nitrogen supply, measured by the soil C:N ratio, are correlated with high radial growth. Water reserves, related to available water storage capacity and to lateral run-off, are also correlated with high radial growth. Analysis of environmental effects during the 20th century showed that growth was strongly correlated with nitrogen supply at the start of the century, and with aluminium toxicity and climate at the end of the century. The radial growth of trees located on sites with low nitrogen supply was lower before 1970 than that of trees located on nitrogen-rich soils. At the end of the century, radial growth of silver fir was the same for all levels of nitrogen nutrition.
Main conclusions  Our results indicate that nitrogen supply was a limiting factor for the mean radial growth of silver fir before the 1970s. Eutrophication during the 20th century may then have eliminated limitation by nitrogen.