Quercus ilex L. dieback has been reported in several Mediterranean forests, revealing different degree of crown damages even in close sites, as observed in two Q. ilex forest stands in southern ...Tuscany (IT). In this work, we applied a novel approach combining dendrochronological, tree-ring δ13C and genetic analysis to test the hypothesis that different damage levels observed in a declining (D) and non-declining (ND) Q. ilex stands are connected to population features linked to distinct response to drought. Furthermore, we investigated the impact of two major drought events (2012 and 2017), that occurred in the last fifteen years in central Italy, on Q. ilex growth and intrinsic water use efficiency (WUEi). Overall, Q. ilex showed slightly different ring-width patterns between the two stands, suggesting a lower responsiveness to seasonal climatic variations for trees at D stand, while Q. ilex at ND stand showed changes in the relationship between climatic parameters and growth across time. The strong divergence in δ13C signals between the two stands suggested a more conservative use of water for Q. ilex at ND compared to D stand that may be genetically driven. Q. ilex at ND resulted more resilient to drought compared to trees at D, probably thanks to its safer water strategy. Genotyping analysis based on simple-sequence repeat (SSR) markers revealed the presence of different Q. ilex populations at D and ND stands. Our study shows intraspecific variations in drought response among trees grown in close. In addition, it highlights the potential of combining tree-ring δ13C data with SSR genotyping for the selection of seed-bearing genotypes aimed to preserve Mediterranean holm oak ecosystem and improve its forest management.
Display omitted
•Two close Q. ilex stands differing in crown damage levels were studied.•Dendrochronology, tree-ring δ13C and SSR genotyping were applied.•Genetics showed intraspecific variations in drought response between the two stands.•The two Q. ilex populations differed in water use efficiency (WUE).
Provenance studies are an increasingly important analog for understanding how trees adapted to particular climatic conditions might respond to climate change. Dendrochronological analysis can ...illuminate differences among trees from different seed sources in terms of absolute annual growth and sensitivity to external growth factors. We analyzed annual radial growth of 567 36-year-old pitch pine (Pinus rigida Mill.) trees from 27 seed sources to evaluate their performance in a New Jersey Pine Barrens provenance experiment. Unexpectedly, missing rings were prevalent in most trees, and some years-1992, 1999, and 2006-had a particularly high frequency of missing rings across the plantation. Trees from local seed sources (55 km away from the plantation) had a significantly smaller percentage of missing rings from 1980-2009 (mean: 5.0%), relative to northernmost and southernmost sources (mean: 9.3% and 7.9%, respectively). Some years with a high frequency of missing rings coincide with outbreaks of defoliating insects or dry growing season conditions. The propensity for missing rings synchronized annual variations in growth across all trees and might have complicated the detection of potential differences in interannual variability among seed sources. Average ring width was significantly larger in seed sources from both the southernmost and warmest origins compared to the northernmost and coldest seed sources in most years. Local seed sources had the highest average radial growth. Adaptation to local environmental conditions and disturbances might have influenced the higher growth rate found in local seed sources. These findings underscore the need to understand the integrative impact of multiple environmental drivers, such as disturbance agents and climate change, on tree growth, forest dynamics, and the carbon cycle.
The loss of tropical forest resilience has been linked to increased climate variability and associated droughts, but the response of tropical trees to climate extremes remains poorly understood. This ...limits our ability to design effective forest adaptation strategies in the tropics. Here we analyse the potential of using young trees to analyse climate variability and extremes, which opens new avenues given the increasing area of secondary forests and tree plantations. We used annual tree diameter measurements and stem discs from 139 16-year-old trees belonging to five native species planted in the Sardinilla tree diversity experiment in Panama and compared three methods to determine annual radial growth. Employing inventory measurements, visual stem disc analysis, and wood density measurements, series of radial growth were calculated to compare relative growth during wet and dry extreme events, and to compute continuous climate-growth correlations. Our results show that annual radial growth data derived from wood density profiles are best suited for climate-growth relationships, as they could capture a common growth signal within the high intraspecific variability of young trees to seasonal climatic variables. Annual radial growth data derived visually and from inventories are still useful for quantifying growth responses during extreme drought. The highest similarity among methods to determine annual radial growth, combined with the strongest climate-growth relationships, were found for Cedrela odorata, a species that shows a pronounced decrease in water use and cambial dormancy during the dry season. Stem discs from young trees planted in tropical forest plantations may thus offer a suitable source for dendroecological analyses.
•We compared three methods for quantifying radial growth in tropical tree species.•Using inventory and tree-ring based estimates we identified dry climate extremes.•Tree-ring width derived from wood density provided climate-growth relationships.•Tropical trees from plantations can be used to assess growth responses to droughts.
Small islands that depend on limited freshwater resources are at significant risk from seasonal drought, which poses a major threat to both their ecosystems and communities. Christmas Island, located ...in the eastern Indian Ocean, presents an example for which severe drought conditions during the wet season not only affects its freshwater resources but also biodiversity on the island, including the migration pattern of the iconic red crab species. However, short-term instrumental climate records on this island make it hard to quantify drought variability and assess its associated risks. Tree growth is affected by drought via reduced soil moisture, and hydroclimate reconstruction from tree-ring chronologies can therefore provide longer-term information on historical variability of dry and wet periods. Here, we reconstructed the wet season (December-May) self-calibrating Palmer Drought Severity Index (scPDSI) for Christmas Island using 64 remote tree-ring chronologies from Asia, Australia, and New Zealand. scPDSI was reconstructed using the Point-to-Point Regression (PPR) method and compared with regional marine coral proxies for independent verification. The remote tree-ring chronologies explained more than 66 percent of scPDSI variance (R-squared) over the calibration period. The trees identified as significant predictors in the regression model were primarily located in areas affected by the Indo-Pacific climate drivers including the Indian Ocean Dipole (IOD). The reconstructions span 1540 CE to 2000. During the first four centuries of this period, the frequency of extreme (5th percentile) droughts and pluvial events rarely exceeded one event per 13 years. In contrast, the frequency of both extremes experienced an unprecedented increase during the 20th century, and with a notable shift towards dry conditions. These findings highlight a significant shift towards more frequent and severe dry conditions during the wet season on Christmas Island, posing a challenge to water resource management and potentially threatening the island's ecosystem and services to the community.
Stable oxygen isotopes measured in tree rings are useful for reconstructing climate variability and explaining changes in physiological processes occurring in forests, complementing other tree-ring ...parameters such as ring width. Here, we analyzed the relationships between different climate parameters and annually resolved tree-ring δ(18)O records (δ(18)O(TR)) from white spruce (Picea glauca MoenchVoss) trees located near Tungsten (Northwest Territories, Canada) and used the NASA GISS ModelE2 isotopically-equipped general circulation model (GCM) to better interpret the observed relationships. We found that the δ(18)O(TR) series were primarily related to temperature variations in spring and summer, likely through temperature effects on the precipitation δ(18)O in spring, and evaporative enrichment at leaf level in summer. The GCM simulations showed significant positive relationships between modelled precipitation δ(18)O over the study region and surface temperature and geopotential height over northwestern North America, but of stronger magnitudes during fall-winter than during spring–summer. The modelled precipitation δ(18)O was only significantly associated with moisture transport during the fall-winter season. The δ(18)O(TR) showed similar correlation patterns to modelled precipitation δ(18)O only during spring–summer when water matters more for trees, with significant positive correlations with surface temperature and geopotential height, but no correlations with moisture transport. Overall, the δ(18)O(TR) records for northwestern Canada reflect the same significant large-scale climate patterns as precipitation δ(18)O for spring–summer, and therefore have potential for reconstructing past atmospheric dynamics in addition to temperature variability in the region.
REPLY TO MANNING Pearson, Charlotte; Salzer, Matthew; Wacker, Lukas ...
Proceedings of the National Academy of Sciences,
08/2020, Letnik:
117, Številka:
31
Journal Article
•We used dendrochronology for simulating groundwater level fluctuations.•Tree-rings extent changes with groundwater fluctuations in alluvial aquifer.•Integration of dendrochronology and ANN has high ...efficiency in groundwater simulation.•We will find more exact results in the site with more groundwater fluctuations.•The simulated groundwater level can be applied to evaluate droughts.
Groundwater is the most important water resource in semi-arid and arid regions such as Iran. It is necessary to study groundwater level fluctuations to manage disasters (such as droughts) and water resources. Dendrochronology, which uses tree-rings to reconstruct past events such as hydrologic and climatologic events, can be used to evaluate groundwater level fluctuations. In this study, groundwater level fluctuations are simulated using dendrochronology (tree-rings) and an artificial neural network (ANN) for the period from 1912 to 2013. The present study was undertaken using the Quercus Castaneifolia species, which is present in an alluvial aquifer of the Caspian southern coasts, Iran. A multilayer percepetron (MLP) network was adopted for the ANN. Tree-ring diameter and precipitation were the input parameters for the study, and groundwater levels were the outputs. After the training process, the model was validated. The validated network and tree-rings were used to simulate groundwater level fluctuations during the past century. The results showed that an integration of dendrochronology and an ANN renders a high degree of accuracy and efficiency in the simulation of groundwater levels. The simulated groundwater levels by dendrochronology can be used for drought evaluation, drought period prediction and water resources management.
Despite a long history of discussion of ‘non‐stationarity’ in dendrochronology, researchers and modellers in diverse fields commonly rely on the implicit assumption that tree growth responds to ...climate drivers in the same way at any given time. Synthesising recent work on drought legacies and other climate‐related phenomena, we show tree growth responses to climate are temporally variable, and that abrupt variability is commonly observed in response to diverse events. Thus, we put forth a ‘growth‐climate sensitivity’ framework for understanding temporal variability (including non‐stationarity) in the sensitivity of tree growth to climate. We argue that temporal variability is ubiquitous, illustrating limits to the ways in which tree growth is often conceptualised. We present two conceptual hypotheses (homoeostatic sensitivity and dynamic sensitivity) for how tree growth sensitivity to climate varies, and evaluate the evidence for each. In doing so, we hope to motivate increased investigation of the temporal variability in tree growth through innovative disturbance or drought experiments, particularly via the inclusion of recovery treatments. Focusing on growth‐climate sensitivity and its temporal variability can improve prediction of the future states and functioning of trees under climate change, and has the potential to be incorporable into predictive dynamic vegetation models.
We present a new perspective on the sensitivity of tree growth to climate: that it is not constant across time. While many models implicitly treat tree growth response to climate as temporally invariant, we argue that trees respond differently to equal climate forcings at different times. We refer to this in the manuscript as the “temporal variability in tree growth sensitivity,” and discuss the evidence and potential mechanisms of variable growth‐climate sensitivity.
Black spruce trees growing on warming permafrost lean in all directions due to soil movement, forming a “drunken” forest. Two hypothetical drivers of drunken forest development are (i) loosening of ...the soil foundation induced by permafrost degradation in warm summers and (ii) mound rising induced by freezing soil in winter. However, no evidence has previously clarified whether recent tree leaning is related to climate warming or is part of a natural hummock formation process. Here, we provide evidence that tree leaning and soil hummock formation have accelerated due to climate warming. We find that trees’ leaning events synchronize with the development of soil hummocks as recorded in tree rings with lignin‐rich cells. Tree leaning is caused by mound rising in winter due to refreezing of soil following deep thaws in summer, rather than by loosening of the soil foundation in summer. Hummock formation shifted from periodic events before 1960 to continuous mound rising in the warmer succeeding 50 years. Although soil change is generally a slow process, recent permafrost warming has induced rapid hummock formation, which threatens the stability of drunken forests and organic carbon in soil hummocks based on shallow permafrost table.
We found that tree leaning and soil hummock formation have accelerated due to recent climate warming. Development of the drunken forest is caused by the growth of soil hummocks before 1960, but hummock formation shifted from periodic events to continuous mound rising in the warmer succeeding 50 years. Recent warming threatens the stability of drunken forests and organic carbon stored in soil hummocks even in the continuous permafrost area.
On tree longevity Piovesan, Gianluca; Biondi, Franco
The New phytologist,
August 2021, Letnik:
231, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Summary
Large, majestic trees are iconic symbols of great age among living organisms. Published evidence suggests that trees do not die because of genetically programmed senescence in their ...meristems, but rather are killed by an external agent or a disturbance event. Long tree lifespans are therefore allowed by specific combinations of life history traits within realized niches that support resistance to, or avoidance of, extrinsic mortality. Another requirement for trees to achieve their maximum longevity is either sustained growth over extended periods of time or at least the capacity to increase their growth rates when conditions allow it. The growth plasticity and modularity of trees can then be viewed as an evolutionary advantage that allows them to survive and reproduce for centuries and millennia. As more and more scientific information is systematically collected on tree ages under various ecological settings, it is becoming clear that tree longevity is a key trait for global syntheses of life history strategies, especially in connection with disturbance regimes and their possible future modifications. In addition, we challenge the long‐held notion that shade‐tolerant, late‐successional species have longer lifespans than early‐successional species by pointing out that tree species with extreme longevity do not fit this paradigm. Identifying extremely old trees is therefore the groundwork not only for protecting and/or restoring entire landscapes, but also to revisit and update classic ecological theories that shape our understanding of environmental change.
PDF
