Age-related drought sensitivity of Atlas cedar (Cedrus atlantica) in the Moroccan Middle Atlas forests

Age-related tree responses to climate change are still poorly understood at the individual tree level. In this paper, we seek to disentangle the relative contribution of tree age to growth decline and growth–climate relationships in Atlas cedar (Cedrus atlantica Manetti) trees at the Middle Atlas Mountains, northern Morocco. Dendrochronological methods were applied to quantify growth–climate relationships using tree-ring width indices (TRWi) calculated for cedars of two contrasting age groups (old trees, age ≥150 years; young trees, age <150 years). TRWi–climate relationships were assessed at the site and tree levels by using response functions and linear mixed-effects models, respectively. Growth of the studied Atlas cedars was negatively affected by recurrent droughts and by the steep temperature rise since the 1970s. Response functions and mixed-effects models indicated that the decline in tree growth was mainly explained by diminishing precipitation. The negative association between cedar growth and temperature was stronger in old than in young trees. Vulnerability to temperature-induced drought stress in old cedar trees may lead to an impending growth decline. We argue that the age dependence of growth sensitivity to drought must be quantified and considered at the individual tree level when predicting the future dynamics and persistence of cedar forests in the Moroccan Middle Atlas.     

Age-dependent responses of tree-ring growth and intra-annual density fluctuations of Pinus pinaster to Mediterranean climate

Dendrochronology generally assumes that climate–growth relationships are age independent once the biological growth trend has been removed. However, tree physiology, namely, photosynthetic capacity and hydraulic conductivity changes with age. We tested whether the radial-growth response to climate and the intra-annual density fluctuations (IADFs) of Pinus pinaster Ait. varied with age. Trees were sampled in Pinhal de Leiria (Portugal), and were divided in two age classes: young (<65 years old) and old (>115 years old). Earlywood and tree-ring width of young P. pinaster trees were more sensitive to climate influence while the response of latewood width to climate was stronger in old trees. Young trees start the growing season earlier, thus a time window delay occurs between young and old trees during which wood cells of young trees integrate environmental signals. Young trees usually have a longer growing season and respond faster to climate conditions, thus young P. pinaster trees presented a higher frequency of IADFs compared with old trees. Most of the IADFs were located in latewood and were positively correlated to autumn precipitation. The radial-growth response of P. pinaster to climate and the IADFs frequency were age dependent. The use of trees with different age to create a tree-ring chronology for climate studies can increase the resolution of climatic signals. Age-dependent responses to climate can also give important clues to predict how young and old trees react to climate change.     

Tree age,site and climate controls on tree ring cellulose δ18O: A case study on oak trees from south-western France

A main concern of dendroclimatic reconstruction is to distinguish in the tree ring proxy the influence of the climate variables of interest from other controlling factors. In order to investigate age, site and climate controls on tree ring width and cellulose δ¹⁸O, measurements have been performed in nearby groups of young (145 years old) and older (310–405 years old) oak trees in south-western France, covering the period 1860–2010.Within a given site, inter-tree deviations are small, pointing to a common climatic signal. Despite a similar inter-annual variability, the average level of cellulose δ¹⁸O in the young tree group is ∼0.8‰ higher than in the old trees. Such offsets might be caused by different soil properties and differences in the fraction of the source water used by trees from different depths. The δ¹⁸O of water in the top soil layer is directly related to the current growing season precipitation, while deeper water can have a lower and more constant δ¹⁸O. Local cave drip waters at 10 m depth indeed show a constant isotopic composition, which corresponds to pluri-annual mean precipitation.A 2‰ increasing trend is observed in cellulose δ¹⁸O of young trees in the first 30 years of growth, during a period when no trend is visible in older trees. This increase can be quantitatively explained by humidity gradients under the forest canopy, and a changing microclimate around the crown as trees grow higher.While relationships between tree ring width and climate appear complex, the isotopic composition of cellulose is strongly correlated with summer maximum temperature, relative humidity and evapotranspiration (r ≈ 0.70). Weaker correlations (r ≈ 0.40) are identified with precipitation δ¹⁸O from a 15-year long local record and from the REMOiso model output. These results imply that leaf water enrichment has a stronger control on the inter-annual variability of cellulose δ¹⁸O than the δ¹⁸O of precipitation.This study demonstrates the suitability of oak tree ring cellulose δ¹⁸O for reconstructing past summer climate variability in south-western France, provided that the sampling and pooling strategy accounts for the fact that trees from different sites and of different age can introduce non-climatic signals.     

Age structure and climate sensitivity of a high Andean relict forest of Polylepis rodolfo-vasquezii in central Peru

For a better understanding of forest ecology, tree-ring studies can provide information on climate sensitivity, tree growth patterns and population age structure that can inform about stand dynamics such as recruitment of new individuals, and other interspecific interactions related to competition and facilitation. Little is known about the ecology of the recently identified high Andean tree species Polylepis rodolfo-vasquezii. Here, we analyzed the relationship between tree size and age of two P. rodolfo-vasquezii forest stands located in the central Peruvian Andes at 11°S in latitude, and compared their growth patterns and climate sensitivity. We measured the height and diameter of each individual tree and collected tree core samples of living trees and cross sections of dead standing trees to generate two centennial tree-ring chronology at Toldopampa (1825–2015 CE) and at Pomamanta (1824–2014 CE) sites. The dendrochronological dates were evaluated by ¹⁴C analysis using the bomb-pulse methods analyzing a total of 9 calendar years that confirm the annual periodicity of this tree species. At the Toldopampa stand most trees ranged from 70 to 80 years old, with a 190-year old individual, being an older and better preserve forest than Pomamanta, with younger trees, probably because more human disturbances due to closer village proximity. No significant relationships were found between tree age and size in the oldest stand alerting that tree diameter should not be used as a metric for estimating tree ages as a general rule. The distinct growth patterns and the size-age relationship observed at the two forests may reflect distinct histories regarding human activities such as fire and logging. Nevertheless, both the Toldopampa and the Pomamanta tree-ring width chronologies exhibited common growth patterns and shared a similar positive response to temperature of the current growing season. Overall, our study confirmed the annual radial growth periodicity in P. rodofolfo-vasquezii trees using an independent method such as ¹⁴C analyses and a strong climate sensitivity of this tree species. These findings encourage the development of an extensive P. rodolfo-vasquezii tree-ring network for ecological and paleoclimate studies in the tropical Andes in South America.     

Climate–growth analysis of Qilian juniper across an altitudinal gradient in the central Qilian Mountains, northwest China

In the context of global warming, it is of high importance to assess the influence of climatic change and geographic factors on the radial growth of high-elevation trees. Using tree-ring data collected from four stands of Qilian juniper (Juniperus przewalskii Kom.) across an altitudinal gradient in the central Qilian Mountains, northwest China, we compared the radial growth characteristics and climate–growth relationships at different elevations. Results indicated that there was little difference in the tree-ring parameters of the four chronologies. Correlation analyses both for unfiltered and 10-year high-passed data of monthly climatic variables and chronologies were presented to investigate the climatic forcing on tree growth, and results revealed that the correlation patterns were consistent among the four sites, especially for high-passed data. We employed the principal components analysis method to obtain the first principal component (PC1) of the four chronologies and computed the correlations between PC1 and climate factors. The PC1 correlated significantly with winter (November–January) temperature, prior August and current May temperature, and precipitation in the previous September and current January and April, indicating that tree growth in this region was mainly limited by cold winter temperature and drought in early growing season and prior growing season (prior August and September). However, the climate–growth relationships were unstable; with an increase in temperature, the sensitivity of tree growth to temperature had decreased over the past few decades. Considering the instability of the climate–growth relationships, climate reconstructions based on tree rings in the study area should be approached with more caution.     

Effects of canopy position on climate-growth relationships of Qinghai spruce in the central Qilian mountains,northwestern China

Northwestern China has experienced dramatic climate change characterized by rapid warming since the 1980s with the warming trend substantially slowing after 2000. Qinghai spruce (Picea crassifolia Kom.), a key tree species in northwest China, has been predicted to be strongly coupled with climate change. However, how the trends in biomass growth change at different canopy positions under climate change and whether climate–growth responses vary with canopy position remain unclear. A total of 222 trees were sampled by a stand-total sampling strategy in the central Qilian Mountains. Trees were assigned to four canopy positions according to height and distance from neighbors: dominant, codominant, intermediate, and suppressed. Our results indicate that trees in dominant and codominant canopy positions dominate the decreasing trend in stand-level biomass from 1980 to 2000 and the increasing trend from 2000–2013, contributing 81.3 % and 86 %, respectively, whereas trees in the intermediate and suppressed canopy positions contributed less. This result was attributed to a more sensitive response of biomass growth in trees in dominant and codominant canopy positions to climate change. From 1980 to 2000, the stronger decreasing trend in biomass growth at dominant and codominant canopy positions is mostly accounted for by increasing temperature. A more pronounced water deficit might have restricted biomass growth more than that at the intermediate and suppressed canopy positions. However, from 2000 to 2013, drought stress was relieved and summer standardized precipitation evapotranspiration index became a leading factor, which promoted the recovery in biomass at dominant and codominant canopy positions. In a word, compared with intermediate and suppressed canopy trees, those in dominant and codominant positions are less resistant to drought, but dominant and codominant canopy position's biomass can recover more when drought stress is relieved. A more robust understanding of canopy-level growth response and resilience to climate change is crucial to fully understand forest growth dynamics under fluctuating climate conditions.     

Climate impact on growth dynamic and intra-annual density fluctuations in Aleppo pine (Pinus halepensis) trees of different crown classes

Mediterranean environments are of special interest for the study of the relationships between climate, growth and anatomic features. Dendrochronological techniques were applied at eight sampling sites that were selected throughout the natural distribution area of Pinus halepensis in the Iberian Peninsula. The objectives of this paper were: (i) to identify relationships between radial growth and climate for different crown classes of Aleppo pine (P. halepensis Mill.); (ii) to quantify the presence of intra-annual density fluctuations (IADFs) according to crown class and cambial age; (iii) to establish the relationships between IADFs and climate. In the more mesic sites, dominant trees showed higher climatic sensitivity than suppressed trees, while in the more xeric sites suppressed trees showed higher sensitivity than dominant trees. Tree-ring growth of both crown classes correlated positively with precipitation during and prior to the growing season. IADFs were more frequent in young than in old stands without differences between crown classes. Precipitation in April and December was positively correlated to the occurrence of IADFs, while precipitation in July correlated negatively. A higher frequency in IADFs occurred in the last 50 years, which coincides with the increase in drought events in the Iberian Peninsula.     

Sancho,the oldest known Iberian shrub

Cliffs are refuges for old trees and shrubs. In the Mediterranean Basin most dendroclimatic reconstructions have focused on high-elevation forests where tree radial growth is constrained by low temperatures in addition to drought stress. Old shrubs may provide longer ring-width series of hydroclimate proxies in low-elevation, drought-prone Mediterranean ecosystems where old trees are rare. To fill this research gap we investigated the maximum age and climate sensitivity of young, old, and recently dead Phoenician junipers (Juniperus phoenicea L.), growing on calcareous cliffs and nearby plains, in the Guara Natural Park (northeast Spain). The oldest living juniper was ¹⁴C-dated to be 927 years old, and it was named “Sancho” after Don Quixote’s squire. Based on ring counts, the maximum age was 655 years. The difference in age estimates between the ¹⁴C-dates and ring counts was 39 years indicating that ring counts underestimate age. This was due to missing and wedging rings making the cross-dating of old junipers unfeasible. Cool and wet conditions from May to July enhanced radial growth of young junipers. Old shrubs have a high dendroecological potential in Mediterranean sites where their growth is constrained by warm-dry conditions during the growing-season. Further techniques combining dendrochronological and wiggle-match ¹⁴C dating may allow reconstructing long-term hydroclimate in low-elevation Mediterranean areas.     

Climatic Stress during Stand Development Alters the Sign and Magnitude of Age-Related Growth Responses in a Subtropical Mountain Pine

The modification of typical age-related growth by environmental changes is poorly understood, In part because there is a lack of consensus at individual tree level regarding age-dependent growth responses to climate warming as stands develop. To increase our current understanding about how multiple drivers of environmental change can modify growth responses as trees age we used tree ring data of a mountain subtropical pine species along an altitudinal gradient covering more than 2,200 m of altitude. We applied mixed-linear models to determine how absolute and relative age-dependent growth varies depending on stand development; and to quantify the relative importance of tree age and climate on individual tree growth responses. Tree age was the most important factor for tree growth in models parameterised using data from all forest developmental stages. Contrastingly, the relationship found between tree age and growth became non-significant in models parameterised using data corresponding to mature stages. These results suggest that although absolute tree growth can continuously increase along tree size when trees reach maturity age had no effect on growth. Tree growth was strongly reduced under increased annual temperature, leading to more constant age-related growth responses. Furthermore, young trees were the most sensitive to reductions in relative growth rates, but absolute growth was strongly reduced under increased temperature in old trees. Our results help to reconcile previous contrasting findings of age-related growth responses at the individual tree level, suggesting that the sign and magnitude of age-related growth responses vary with stand development. The different responses found to climate for absolute and relative growth rates suggest that young trees are particularly vulnerable under warming climate, but reduced absolute growth in old trees could alter the species’ potential as a carbon sink in the future.     

Age dynamics of genetic variation in an isolated population of chalk pine Pinus sylvestris var. cretacea Kalenicz. ex Kom. from Donbass

Based on analysis of variation at ten allozyme loci in three age groups (25–35, 40–80, and more than 100 years of age) of plants and in seed embryos, demographic dynamics of the gene pools was studied in a small (60.5 ha) isolated relict population of chalk pine Pinus sylvestris var. cretacea Kalenicz. ex Kom. from the steppe zone of Ukraine. The observed grenotype proportions in these tree groups were shown to fit Hardy-Weinberg expectations, while in the embryos of their seeds, an excess of homozygotes was observed at five to nine loci. The mean observed heterozygosity in the sample of old (>100 years of age) trees (H _O = 0.225) was substantially lower than in trees of the two other age groups (H _O = 0.307; 0.311), but significantly higher than in the corresponding embryo samples (H _O = 0.183–0.207). No allele and genotype heterogeneity of the maternal trees and embryos of their seeds was found. However, heterogeneity was high when the progeny of trees of different ages, particularly in pairs with old trees, were compared.     

Effect of maternal age on the outcomes of in vitro fertilization and embryo transfer (IVF-ET)

This is a retrospective, observational study to evaluate the effect of maternal age on the outcomes of in vitro fertilization and embryo transfer (IVF-ET). 11830 IVF-ET cycles from 10268 women were included. Four groups of different maternal age periods were compared. The groups were 21?C30 years old group (4549 cycles), 31?C35 years old group (4424 cycles), 36?C40 years old group (2429 cycles), and over 40 years old group (428 cycles). The mean starting dose of Gn and mean total dose of Gn in each cycle were significantly higher (P<0.01), while the mean retrieved oocyte number was significantly lower (P<0.01) in groups of higher maternal age period than those in each of the lower groups. The biochemical pregnancy rate and the clinical pregnancy rate were significantly lower (P<0.01), while the miscarriage rate was significantly higher (P<0.01) in groups of higher maternal age period than those in the lower groups. No difference was found in two-pronuclear zygotes (2PN) rate and good quality embryo rate among different groups. Birth defect rate was also comparable in the born babies in different groups. In the group with patients?? age over 40 years old, the pregnancy rate was 26.87%, the clinical pregnancy rate was 19.39%, while the miscarriage rate after clinical pregnancy was 36.14%. To draw the conclusion, patients with higher maternal age had worse IVF outcomes. In women of fertile age, patients between 20 and 30 years old have the best IVF outcomes. Patients over 40 years old have poor IVF outcome and high miscarriage rate, which suggested the necessity of preimplantation genetic screening (PGS).     

INFLUENCE OF SITE AND STAND FACTORS ON THE DISTRIBUTION OF CRUSTOSE LICHENS OF THE CALICIALES IN A SUBOCEANIC SPRUCE FOREST AREA IN CENTRAL NORWAY

The distribution of crustose Caliciales has been surveyed in 100 spruce forest patches in Sør-Trøndelag, central Norway. Relationships between occurrence of the species and a number of site and stand variables were analysed by detrended correspondence analysis (DCA) and direct gradient analysis. Species diversity was significantly higher in old forests and in forests at higher altitudes compared to young forests and forests at lower altitudes. Old trees and snags are considered to be the most important structural components in old forests promoting species diversity of the Caliciales. Threatened or vulnerable species, such asChaenotheca gracillima, Cybebe gracilenta, Sclerophora coniophaeaandS. peronellawere confined to forest on rich soils showing no correlation with forest stand age.Chaenotheca brachypodaandC. trichialiswere found to be the most typical old forest species among the Caliciales. Humidiphilous species are considered to be less affected by forestry in a humid climate. A change in forestry practice towards methods imitating the natural dynamic processes is considered necessary to maintain species diversity of the Caliciales in boreal forests.     

川西米亚罗林区不同海拔岷江冷杉生长对气候变化的响应

为分析青藏高原东缘半湿润区树木生长与气候关系随海拔变化的规律,于川西米亚罗林区分别在高、中、低海拔选取3个采样点,共采集132棵岷江冷杉年轮样芯,建立了最长达170a(1842-2011年)3个海拔高度的差值年表.岷江冷杉年轮指数与气候因子的相关分析表明:随海拔高度降低,温度与生长的负相关呈增加趋势.高海拔岷江冷杉径向生长与前—年冬季最低温呈显著正相关,中低海拔与当年春季均温、最高温和年均最高温呈显著负相关.低海拔岷江冷杉与当年4月降水呈显著正相关,随海拔升高降水与岷江冷杉生长的相关性降低.中低海拔岷江冷杉年表与4、5月帕尔默干旱指数(P DSI)呈显著正相关,表明在中低海拔存在春季干旱胁迫,抑制了岷江冷杉的生长.另外,大龄树木比小龄树木对气候变化的响应更敏感.     

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.     

Rapid warming induces the contrasting growth of Yezo spruce (Picea jezoensis var. microsperma) at two elevation gradient sites of northeast China

Accurately assessing the impact of climate changes on tree growth or forest productivity is vital to better understand global carbon cycles. Here, we carried out dendroclimatological research on Yezo spruce (Picea jezoensis var. microsperma) along an elevation gradient in two sites to investigate the effect of rapid warming on spruce growth in northeast China. Results indicated that trees at two low-elevation sites had significantly wider ring widths and higher basal area increment (BAI) compared with high-elevation sites. Ring widths and BAI of Yezo spruce at low elevations showed a clear growth increase during the 1940s–1970s followed by a significant decline after 1980. However, trees at high elevations showed a relatively stable growth during the 1940s–1970s followed by a significant increase after 1980. Rapid warming after 1980 increased the radial growth of Yezo spruce at high-elevation sites, but reduced tree growth at low-elevation sites. Winter precipitation and growing season temperature were positively correlated with radial growth of Yezo spruce at high elevations, but negatively correlated with tree growth at low elevations. A clear pattern of growth and growth-climate relationship changed in 1980. The temperature threshold for determining the impact of climate on Yezo spruce could change with latitude or site. Difference in drought caused by warming may be the main reason for the opposite response of tree growing at different altitudes in northeast China. The mechanism of rapid warming driving contrasting growth at different elevations should also be investigated in other tree species in NE Asia. In the context of future climate warming, our findings are of great significance for tree growth in assessing forest dynamics and carbon cycling.     

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。     

Differences in metabolite profiles between blood matrices,ages, and sexes among Caucasian individuals and their inter-individual variations

Endobiotic metabolites are associated with biological processes in the body and therefore may serve as biomarkers for disease states or therapeutic efficacy and toxicity. However, information is limited regarding how differences between blood matrices, patient backgrounds, and sample handling affect human metabolite profiles. Our objective was to obtain metabolite profiles from Caucasian individuals, based on different matrices (plasma and serum), subject backgrounds (male/female and young/old), and storage conditions (2 or 10 freeze–thaw cycles). In total, 297 metabolites were detected by LC/MS and GC/MS, and more than 75 % of them were highly represented in all sample groups. The multivariate discriminant analysis (OPLS-DA as a model) singled out the matrix type as the most important variable influencing global metabolic profiles; that is, more than 100 metabolites were significantly different based on the matrix type. The influence of subject backgrounds on global metabolic profiles was consistent between plasma and serum. Age-associated differences were more predominant in females than males, whereas gender-associated differences were more prevalent in young subjects than old individuals were. The relative standard deviation of metabolite levels in subjects with the same background ranked from 0.1 to 1.5. Moreover, the changes of metabolite levels caused by freeze–thaw cycles were limited, and the effect was more prominent in plasma than serum. These data demonstrate the impact of matrix, age, gender, and freeze–thaw cycles on the metabolite profiles and reveal metabolites affected by these factors. Thus, our results provide would useful fundamental information for exploring and qualifying biomarkers for clinical applications.