Dendrochronologia最新文献

Tree-ring stable isotopes are typically measured in latewood cellulose to mitigate potential carry-over effects from previous year storage pools. The isotopic composition of individual tree-ring segments is thought to include considerable intra-annual variability. This sampling strategy may be complicated by steep intra-annual isotope gradients that can rival the inter-annual variability, however. Consistent sampling of latewood material may not always be possible due to low sample availability or high prevalence of narrow rings or low amounts of latewood because of species-specific changes in ring width. Therefore, years that contain samples with higher portions of non-latewood (earlywood) material may influence the final chronology of isotopic variability. Here, we analyze the potential influence that changing earlywood and latewood components of individual tree rings can have on stable carbon and oxygen records from Quercus spp. and Pinus heldreichii chronologies. Analysis of stable isotopes in oak tree rings with varying amounts of latewood show no statistically significant differences in the range of isotopic composition, nor any major differences when considering the same calendric year. Similar results were found for the pine data, when comparing stable isotope measurements with earlywood-to-latewood ratio and maximum density. We argue that this simple approach should be applied to any long-term tree-ring stable isotope record in order to provide a better understanding of the potential biases that could arise from previously recorded intra-annual variability in the wood.

Forest growth is driven by climate variability at continental to regional scales, but other factors play major roles at local scales (0.1–1 ha). Topography impacts on tree growth responses to climate stressors, including drought, by modifying radiation, evapotranspiration rates and the access to soil moisture. However, there is a lack of studies investigating how topographical factors (elevation, aspect, slope) affect climate-growth relationships considering both continuous (tree-ring width) and discrete wood-anatomical features (e.g., intra-annual density fluctuations–IADFs). Here, we investigated how topography modulated the influences of climate and drought on semi-arid Juniperus thurifera forests from north-eastern Spain. We compared two stands located in valley bottoms and two stands located in steep slopes. Radial growth was measured using dendrochronology which also allowed quantifying latewood IADFs. A proxy of topographic influence (incident radiation) was calculated. In addition, the Vaganov-Shashkin (VS) model was used to infer the main climatic constraints of growth at intra-annual scales. We found that junipers growing in valley bottoms were taller and produced more IADFs than junipers growing in steep slopes, but responded less to precipitation variability. This was confirmed by the VS model which showed that low soil moisture in June limited growth, particularly in steep-slope sites and during dry periods. Wet-cool late-summer conditions induced the formation of IADFs. The topoclimatic modulation of growth was explained by the interaction between incident radiation and tree age. Furthermore, climate-growth associations are changing as temperatures rise. Drought impacts on growth are strengthening, but less responsive junipers growing in valley bottoms may be buffered against intensified aridification.

Understanding the relationship between stem diameter micro-variation (SDMV) and stem water status and revealing the mechanism regulating stem water are essential for elucidating environmental adaptation and water use strategies in forest trees. Here, we report the results of the year-round monitoring (November 2018–October 2019) of SDMV and xylem sap flow obtained using high-resolution dendrometers and Granier-type thermal dissipation probes, respectively, in mature trees of three species in the semiarid Loess Plateau region: Quercus liaotungensis, Platycladus orientalis, and Robinia pseudoacacia. The year-round trend for the variations in stem diameter can be divided into phases of a decreasing period and a relatively stable period in the non-growing season, and a progressive rise and fluctuating plateau throughout the growing season. The observed interspecific differences in the time to full recovery from the water deficit state corresponded to species phenology and soil moisture conditions. These differences were manifested as the responses of sap flux density (F_d) and tree water deficit (TWD) to variations in soil water content during the growing season. Q. liaotungensis implements stomatal regulation early to avoid drastic water loss in the trunk, P. orientalis maintains a relatively stable F_d at the expense of increased TWD under soil drought, and R. pseudoacacia maintains relatively low stomatal conductance under soil drought with an increase in TWD. The results revealed that SDMV is determined by the stem water status and species-specific strategies for water use, which could provide beneficial information for forestation practices in semiarid regions.

Ongoing climate change can have varying impacts on tree growth within the growing season and across their elevation ranges, with important implications for forest ecosystem functions and services. However, our knowledge of these effects on climate-sensitive Himalayan forests is still limited. Here, we explore the elevational changes in climatic factors driving long-term changes in the radial growth of Himalayan Hemlock (Tsuga dumosa), including recent responses to unprecedented climate warming in the central Himalayas. We evaluated several growth parameters, including total ring width, earlywood width, adjusted latewood width, and maximum latewood density, in unique > 400-year-old forests along an elevational gradient of 2500–3100 m on the southern slopes of Dhaulagiri, Nepal. Our findings show that changing climatic conditions, characterized by increasing temperatures and variable precipitation patterns, had a more detrimental effect on Tsuga growth at the edge of its elevation range compared to the optimal mid-elevation zone. Specifically, at lower elevations, the combination of spring and preceding autumn warming restricted earlywood growth, while warmer temperatures in late summer stimulated growth at the mid-elevation site by alleviating the cool growth-limiting conditions caused by high monsoonal precipitation. Furthermore, increased spring temperatures enhance latewood density, while summer warming promotes latewood growth at higher elevations. Additionally, we observed that the recent rise in autumn temperatures has begun to impede Tsuga growth across all elevations. In conclusion, our study reveals that the growth of Tsuga trees is influenced by multiple climatic factors that vary within the growing season and across different parts of its elevation range. Recent spring warming has constrained growth in lower elevations, while higher previous autumn temperatures have reduced growth at both higher and lower boundaries of the species' range. These findings contribute to a better understanding of the complex relationship between climate change and tree growth dynamics, particularly in vulnerable Himalayan forests.

Fire-resistant species may have an essential ecological role in the natural regeneration process of degraded landscapes. Moquiniastrum polymorphum is a ruderal and fire-resistant species that occupies fire-disturbed areas in Brazilian Atlantic Forest. Evaluating a species’ growth sensitivity to fire and climate can help understand its complex successional process. In the present study, we used dendrochronology to describe the radial growth trajectories of M. polymorphum in a fire-disturbed area in the Atlantic Forest (Poço das Anta Biological Reserve), detect post-fire effects on the species’ growth, and investigate climate-growth relationships. We described the long-term growth trend of the species, it increased in the first years and was constant in the following years. The chronology was positively correlated with precipitation and negatively correlated with temperature at the end of the rainy season. Our results reveal that M. polymorphum did not reduce its growth after fire events. When observing through an epoch perspective, fire can even be positive to the species growth. These growth results indicated species fire resistance, which likely provides a resilient tree cover after forest fires and allows disturbed Atlantic Forest environments to break grass-fire cycles. This resistance may have a direct relationship with the opportunistic characteristic of the species in fire-prone areas in the Atlantic Forest. However, we highlight the critical role this species plays in the natural regeneration of burned sites in the Atlantic Forest.

The escalating decline in growth trends of European beech (Fagus sylvatica) observed across its distribution area pose a major ecological and economic challenge for countries with a high proportion of beech, such as Slovenia. In this study, the effects of climate change were examined at a high-resolution scale, encompassing the large climatic, orographic, and ecological variability of beech forests in Slovenia. Using basal area increment data (BAI) from a tree-ring network (48 sites in Slovenia), modelled climate data, and generalized linear mixed models (GLMM), we found an average growth decline of 11% between the 1953–1985 and 1986–2018 subperiods, affecting 90.5% of the forest stands. Based on climate data, we defined two contrasted marginal areas of beech presence (warm and cold) and analysed the growth changes over time. The warm marginal areas, which predominate near the geographical margin of beech distribution with a sub-Mediterranean climatic regime, were most affected by growth decline, threatening the survival of beech populations in the area. In contrast, cold marginal areas, mainly at high elevations in the Alps, where beech growth had previously been limited by low temperatures, turned out to be the only ones where growth of beech increased under prevailing warming conditions. Consequently, high elevation regions harbour climatic potential for increased beech growth performance, and may represent areas of future expansion of the species.

The availability of both ancient and modern wood samples enables the Chinese fir (Cunninghamia lanceolata) in Central East China to become a potential tree species for dendroclimatic reconstruction over the Common Era. However, the potential of using tree-ring α-cellulose oxygen isotope ratios (δ¹⁸O_TRC) in Chinese fir for the purposes of cross-dating and climatic reconstruction remains unexplored. Here we presented three δ¹⁸O_TRC chronologies (1954–2006 CE) for the whole-ring (δ¹⁸O_WR), earlywood (δ¹⁸O_EW), and latewood (δ¹⁸O_LW) in Chinese fir. The results indicated that the δ¹⁸O_WR had the highest correlation among individual trees. Using the δ¹⁸O_WR instead of the conventionally employed TRW can facilitate the cross-dating procedure. The δ¹⁸O_WR, δ¹⁸O_EW, and δ¹⁸O_LW exhibited the strongest relationships with the hydroclimate variables during the entire (June–September), early (June–July), and late (August–September) summer, respectively. The climate conditions preceding the growing season had a stronger influence on δ¹⁸O_EW than δ¹⁸O_LW. Using the δ¹⁸O_WR and δ¹⁸O_EW to reconstruct the hydroclimate variations may result in greater bias than the use of δ¹⁸O_LW. Our study demonstrated that the δ¹⁸O_TRC in Chinese fir from Central East China has the potential for cross-dating and summer hydroclimate reconstruction.

Pathogen-caused wood decay is believed to be one of a major cause of decreasing tree vitality and increased susceptibility to external biotic and abiotic damaging agents. Using data collected from twenty decay-affected different maturity Norway spruce (Picea abies (L.) Karst) stands, this study aims to explore the interaction between butt rot and crown defoliation and radial increment as indicators of tree vitality. Study results indicate that vitality decline among butt rot-affected Norway spruce is expressed as a significant reduction in radial increment and considerably greater levels of crown defoliation. Decayed Norway spruce trees were found to have higher crown defoliation than undecayed spruce trees. Additionally, a radial increment reduction in the last five years and the last twenty years of the increment sequence was found when decayed Norway spruce tree growth was compared to undecayed. Severely defoliated trees were observed only among decayed trees, and this made up only 1% of the population, indicating that butt rot acts as a predisposing or inciting factor for the decline of Norway spruce. A stand age-dependent relationship was also found among visually healthy undecayed spruce trees, indicating that spruce trees show signs of increasing defoliation as part of the ageing process. Among decayed Norway spruce, no such relationship was found, indicating changes in the effect-response framework for decayed trees. Naturally, both decayed and undecayed trees showed a negative correlation between the level of crown defoliation experienced and the radial increment for the last five years before increment sequencing.

Russia, the country with the most forested area, significantly influences global climate, carbon, and water dynamics. In addition, a considerable part of the Russian forests is in remote regions with a low direct anthropogenic disturbance, but at the same time, recently experiencing unprecedented warming. This combination of factors makes Russia a hotspot for dendrochronological and dendroanatomical studies, providing a valuable perspective on the consequences of climate change in a global context. Dendroanatomy is a powerful dendrochronological tool that provides a robust insight into xylem traits, their relation to climate conditions during tree-rings formation, and the cell structure-function relationship over time (tree life span). Although dendroanatomy in Russia has been gaining momentum lately, there is a long tradition of characterizing and modeling wood anatomical traits, including the development of novel methodologies, hardware and software since the mid-20th century. Unfortunately, in many cases, these advances have been hidden from the international readership because most of them were published in Russian. This descriptive inventory presents an overview of dendroanatomical studies carried out in Russia since the mid-20th century. It focuses on different periods and topics to facilitate its accessibility and highlight its contribution to the global dendrochronological community.

A missing ring occurs when the radial growth of a tree is disturbed when the plant is under stress (e.g., extreme drought, fire, insect attack, frost) as a result of inhibition of cambial activities. Missing rings have been detected in several tree species in different parts of the world, and this phenomenon may be an indicator of imminent tree death. However, we still lack an in-depth understanding of the characteristics and causes of missing rings and their relationship with tree mortality. In this study, we examined missing ring occurrence in Qilian juniper (Juniperus przewalskii Kom.), one of the most long-lived tree species in China, growing in an extremely harsh environment on the Northeastern Tibetan Plateau. The results showed that the missing ring rate was sensitive to drought events during the period 1500–2000 AD, with extreme values of missing ring rate occurring in certain drought years, such as 1665, 1687, 1715, 1824, 1918, etc. In addition, climate warming in recent decades did not lead to an increase in the missing ring rate of Qilian juniper, which may be related to the improving regional water conditions on the plateau. The missing ring rate of Qilian juniper was related to the age of the tree, i.e., it increased first in younger trees and then decreased, with the highest missing ring rate occurring in trees about 800-years-old. Furthermore, trees that eventually died had a higher rate of missing rings before their death than those that survived, suggesting that missing rings have the potential to predict tree mortality. However, the relationship between tree mortality and missing ring rate is a very complex issue and requires further study.