| 1. |
- Greaves, Ciara, et al.
(författare)
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Remarkably high blue ring occurrence in Estonian Scots pines in 1976 reveals wood anatomical evidence of extreme autumnal cooling
- 2023
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Ingår i: Trees. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 37:2, s. 511-522
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Tidskriftsartikel (refereegranskat)abstract
- ‘Blue rings’ (BRs) are visual indicators of less lignified cell walls typically formed towards the end of a tree’s growing season. Though BRs have been associated with ephemeral surface cooling, often following large volcanic eruptions, the intensity of cold spells necessary to produce BRs, as well as the consistency of their formation within and between trees still remains uncertain. Here, we report an exceptionally high BR occurrence within and between Scots pine (Pinus sylvestris L.) trees at two sites in Estonia, including the first published whole-stem analysis for BRs. Daily meteorological measurements from a nearby station allowed us to investigate the role temperature has played in BR formation since the beginning of the twentieth century. The single year in which BRs were consistently formed within and amongst most trees was 1976. While the summer of 1976 is well known for an exceptional heatwave in Northwest Europe, mean September and October temperatures were remarkably low over Eastern Europe, and 3.8 °C below the 1961–1990 mean at our sites. Our findings contribute to a better eco-physiological interpretation of BRs, and further demonstrate their ability to reveal ephemeral cooling not captured by dendrochronological ring width and latewood density measurements.
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| 2. |
- Marshall, John
(författare)
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Thermal imaging of increment cores: a new method to estimate sapwood depth in trees
- 2023
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 37, s. 349-359
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Tidskriftsartikel (refereegranskat)abstract
- The cells in tree sapwood form a network of interconnected conduits which enables the transport of water and nutrients from the tree roots to the canopy. Sapwood depth must be assessed when tree water use is estimated from sap flow velocities. However, current approaches to assess sapwood depth are either not applicable universally, or require expensive instruments, the application of chemicals or laborious field efforts. Here, we present a new method, which estimates sapwood depth by thermal imaging of increment cores. Using a low-cost thermal camera for mobile devices, we show that the sapwood-heartwood boundary is detectable by a sharp increase in temperature. Estimated sapwood depths agree with dye estimates (R-2 = 0.84). We tested our approach on a broad range of temperate and tropical tree species: Quercus robur, Pinus sylvestris, Swietenia macrophylla, Guazuma ulmifolia, Hymenaea courbaril, Sideroxylon capiri and Astronium graveolens. In nearly all species, the methods agreed within 0.6 cm. Thermal imaging of increment cores provides a straightforward, low-cost, easy-to-use, and species-independent tool to identify sapwood depth. It has further potential to reveal radial differences in sapwood conductivity, to improve water balance estimations on larger scales and to quickly develop allometric relationships.
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| 3. |
- Marshall, John
(författare)
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Tree-ring isotopic composition reveals intraspecific variation in water use efficiency of Ait. provenances grown in common gardens
- 2023
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Ingår i: Trees - Structure and Function. - 0931-1890 .- 1432-2285. ; 37, s. 1767-1780
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Tidskriftsartikel (refereegranskat)abstract
- Given the impacts of climate change on forest resources and considering the slowness of evolutionary processes in trees, a need arises to understand the interplay between tree species adaptation to climate, genetic variation, and their impact on tree growth and productivity. Broadening knowledge of the capacity of tree populations to respond to climate-related disturbances is a prerequisite for the development of resilience strategies, including assisted migration and climate-smart forestry. This study tests the physiological ability of different maritime pine provenances, comparing Mediterranean (Corsica, Sardinia, and Tuscany) and Atlantic (Portugal) provenances, to adapt to progressively drier conditions that have occurred in the last thirty years. Four provenance trials with randomized blocks of the five maritime pine provenances were used as test sites in Sardinia (Italy). Wood cores were collected from the 40-year-old plants. Cores were split into five-year segments to determine provenance-related variations in carbon and oxygen stable isotopes and provide information on long-term patterns in intrinsic water use efficiency (iWUE). The provenance x site interaction was the most important source of variation, meaning that the genotypes responded differently to the planting sites. Considering the main effects, both genotype and environmental conditions at the planting sites influenced stable isotope composition in tree rings. This suggests that iWUE was determined by phenotypic plasticity that differed among genotypes. In contrast, provenance responses were stable with time, and the provenance x site interaction was stable across time periods. These findings suggest that provenance selection to improve iWUE in maritime pine may need to consider site conditions but point more to soil conditions than to climate. In any case, they limit our ability to recommend maritime pine provenances based on iWUE until the missing site factors can be identified.
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| 4. |
- Ogana, Friday Nwabueze
(författare)
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Vessel characterization and ring-width of a multipurpose agroforestry tree species (Garcinia kola.(Heckel)) and its relationship with climate in Nigeria
- 2024
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Ingår i: Trees - Structure and Function. - 0931-1890 .- 1432-2285. ; 38, s. 139-150
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Tidskriftsartikel (refereegranskat)abstract
- Tropical agroforestry species are characterized by irregular growth and fruiting pattern, this is because of seasonal differences in the region and unanticipated environmental changes. Tree-ring width features and vessel variables could have a direct relationship with environmental conditions and factors such as precipitation and temperature could impact the growth of the species. This is because, during stressful environmental conditions, tree species record environmental changes through their physiological adjustment. Therefore, wood anatomical and tree-ring width time series was developed for Garcinia kola, a multipurpose tropical species, from a humid forest zone and derived savannah, along two vegetation zones in Nigeria. The species forms rings characterized by marginal parenchyma. The mean tree-ring width (TRW) ranges from 2.63 and 2.30 mm in the humid forest zone and derived savannah, respectively while the vessel number (VN) and vessel density (VD) are 95, 93, and 9.46, and 10.28 N/mm(2) respectively. The results revealed that the radial growth of G. kola showed a positive relationship with the precipitation and the minimum temperature during the peak of the rainy season in derived savannah areas. The VN, RW, and TVA show a significant relationship with the mean annual maximum temperature in the Rainforest and derived savannah area. The vessels are more abundant in samples from the rainforest area than in the derived savannah area, the results revealed that the wood anatomical variables and TRW were sensitive to climatic variables. Hence, they could be good indicators for evaluating tropical tree responses to environmental changes in tropical agroforestry species.
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| 5. |
- Ramesh, Vetukuri
(författare)
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Exogenous melatonin-stimulated transcriptomic alterations of Davidia involucrata seedlings under drought stress
- 2021
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285.
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Tidskriftsartikel (refereegranskat)abstract
- Key message This study shows mitigating effects achieved by exogenously applied melatonin in drought-stressed Davidia involucrata seedlings and demonstrates the reprogramming of gene networks related to melatonin-mediated drought stress response. Drought stress can have adverse effects on endangered plant species such as the dove tree (Davidia involucrata Baill.). Despite significant advances in uncovering the roles of melatonin in abiotic stress tolerance, the function of melatonin in the dove tree during drought stress is unknown. Here, we show the effects of exogenously applied melatonin on drought damage to D. involucrata seedlings. Melatonin pretreatment of dove tree seedlings was correlated with reduced membrane lipid peroxidation, suppressed production of drought-induced reactive oxygen species (ROS), and improved antioxidant capacity. Comparative RNA-Seq-based transcriptome profiling was employed to dissect the mechanistic basis of melatonin in drought response. We found that melatonin pretreatment resulted in differential expression of 2737 genes (1849 up-regulated and 888 down-regulated) under drought stress. Further detailed analysis suggested that melatonin modulates D. involucrata response to drought through fine-tuning of multiple phytohormone signaling and synthesis pathways, including transcriptional stimulation of auxin signaling-related genes and brassinosteroid biosynthetic genes. Moreover, phenylpropanoid biosynthesis and glutathione metabolism pathways were activated by melatonin, which could be linked to the observed enhancement of ROS scavenging capacity in melatonin-pretreated D. involucrata seedlings under drought condition. Additionally, melatonin-mediated drought stress response may involve activation of calcium signaling via up-regulating gene expressions of CNGC, CaM/CML, and CDPK family members. Collectively, this study yields insights into transcriptionally regulatory mechanisms of melatonin action under drought stress and provides a potential strategy for ex situ cultivation and landscape application of endangered ornamental tree species particularly in the context of global climate change.
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| 6. |
- Rocha, Eva, et al.
(författare)
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Assessing urban climate effects on Pinus sylvestris with point dendrometers : a case study from Stockholm, Sweden
- 2023
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Ingår i: Trees. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 37:1, s. 31-40
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Tidskriftsartikel (refereegranskat)abstract
- Changes in surface properties of the urban environments significantly impact the local microclimate. While urban trees are known for providing important thermal regulation, the impact of urban climate on tree growth remains relatively unexplored. The present study focuses on the climate response and growth dynamics of urban Scots pine trees (P. sylvestris) in comparison to their rural counterparts. High-resolution monitoring of stem-radius variations using automatic point dendrometers was performed during the growing seasons (April–October) of 2017 and 2018 in Stockholm, Sweden. In 2018, the region experienced a severe and long-lasting summer drought. In May and July, temperatures were up to 5 °C higher relative to the reference period (1981–2010), and precipitation sums were below the reference period for the entire growing season. Our results show that the urban climate primarily impacts the daily water storage dynamics by decreasing the radius change amplitudes and delaying the time of maximum stem-water replenishment and depletion. Under standard climatic conditions, the warmer climate (1.3 °C) at the urban sites had a positive impact on radial growth increment. Drought periods significantly impact the climate–growth relationships. Stem shrinkage intensifies during the day, and lower growth rates were registered, resulting in reduced annual growth. The high-resolution monitoring provided valuable insights into daily and seasonal patterns of Scots pine stem-radius variations, showing that growth responses to increasing temperature are mainly controlled by moisture availability and site-specific conditions.
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| 7. |
- Sierra, Carlos
(författare)
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Intra-annual isotope variations in tree rings reveal growth rhythms within the least rainy season of an ever-wet tropical forest
- 2022
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 36, s. 1039-1052
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Tidskriftsartikel (refereegranskat)abstract
- Key message Isotope variation (delta O-18) in wood suggests new insights on growth rhythms in trees growing in tropical forest with extremely high precipitation, without seasonal droughts or flooding. It is well known that growth-limiting factors such as seasonal droughts can induce periodicities in woody tissue formation of tropical trees. In regions without seasonal droughts or flooding but sufficient water for photosynthesis (ever-wet tropical forests), rhythmic growth has been previously reported; however, triggering factors remain little explored. Our objective was to establish tree-ring frequency and probable growing season by analysis of the intra-annual variability of isotopic ratios in cellulose (delta O-18(cellulose) and delta C-13(cellulose)) and relationships with environmental variables in two tree species (Humiriastrum procerum and Virola dixonii) growing in an ever-wet tropical forest (Choco region of Colombia, precipitation 7200 mm year(-1), mean annual temperature 25.9 degrees C), located close to the Pacific Ocean at ca 3 degrees 57 ' 12.54 '' N-76 degrees 59 ' 27.96 '' W. Here, we report annual rhythmic growth evidenced by radiocarbon analysis, leaf phenology, dendrometer records, and stable-isotope variation in cellulose. All evidence points to the probable growing season occurring during the least rainy months for both species. While intra-annual delta O-18(cellulose) values follow a rhythmic variation, delta C-13(cellulose) variations show a less clear pattern, probably due to deciduity and remobilization of non-structural carbon stored in previous growing stages. Furthermore, delta O-18(cellulose) covary with relative humidity, vapor pressure deficit, short-wave solar radiation, and temperature during the least rainy months. In contrast, delta C-13(cellulose) values were not significantly correlated with environmental variables. Our results show that stable-isotope variations in tree rings, even under ever-wet conditions, are valuable for understanding drivers of tropical tree growth in such conditions.
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| 8. |
- Tigabu, Mulualem
(författare)
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Calcium-mediated adaptive responses to low phosphorus stress in Chinese fir
- 2020
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 34, s. 825-834
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Tidskriftsartikel (refereegranskat)abstract
- Key message Ca2+ induces adaptive response to low P stress through increased root growth and expansion, but plays minor or no role in remobilization of P in leaf tissues or in maintaining membrane integrity. The role of calcium (Ca2+) in signaling environmental stress has been demonstrated; however, its role in signaling low phosphorus (P) stress and subsequent adaptive responses in trees are largely unexplored. The aim of this study was to examine the effects of Ca2+ application on root growth and expansion, seedling growth, remobilization of P, and maintaining membrane integrity in leaf tissues. Thus, a sand culture experiment was set up with five Ca2+ concentrations (0, 1, 3, 5, and 10 mmol/L Ca(NO3)(2)center dot 4H(2)O) under two P treatments (0.0 and 1.0 mmol/L KH2PO4). After 4 months, growth attributes, P and Ca2+ accumulations, and biochemical responses were determined. Results showed that (1) low P seedlings supplied with 5 mmol/L Ca2+ produced longer roots, larger root surface area, higher root diameter, and larger root volume than the control; (2) seedling height and root collar diameter were positively affected by addition of 3 and 5 mmol/L Ca2+ into the growing media, and whole plant biomass of low P seedlings supplied with 5 mmol/L Ca2+ was significantly higher than the control; (3) whole plant P accumulation was higher in 3 and 5 mmol/L Ca2+ treatments in low P seedlings, whereas whole plant Ca2+ accumulation increased linearly with increasing Ca2+ concentration; and (4) the effects of Ca2+ on malondialdehyde and soluble protein contents and acid phosphatase activity did not show consistent trend with increasing or decreasing Ca2+ concentration. In conclusion, Ca2+ induces adaptive response to low P stress through increased root growth and expansion, but plays minor or no role in remobilization of P in leaf tissues or in maintaining membrane integrity.
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| 9. |
- Tigabu, Mulualem
(författare)
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Genetic diversity and population structure of Pinus halepensis Mill. in Jordan revealed by simple sequence repeats
- 2022
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 36, s. 977-989
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Tidskriftsartikel (refereegranskat)abstract
- Key message Pinus halepensis populations in Jordan maintained a moderate level of genetic diversity with considerable intra-population than inter-population differentiation due to long-distance zygotic and gametic gene flows among populations. The genetic diversity and structure of 156 germplasm samples collected from four natural and five planted Pinus halepensis Mill. populations in Jordan were investigated using simple sequence repeat markers. These fragmented stands represent the easternmost edge of the species natural range of distribution in the Mediterranean basin. Our study revealed relatively high expected heterozygosity and Shannon's diversity index (He = 0.574, I = 1.124). Genetic diversity parameters, Na, Ne, He, and I slightly increased in planted populations compared to natural populations. The AMOVA and population genetic differentiation index (Fst) analysis revealed higher level of intra-population differentiation than inter-population differentiation. The UPGMA cluster analysis and genetic structure analysis revealed two sub-groups, which were not consistent with the geographic distribution pattern. Furthermore, the population genetic distance was not correlated with geographic distance (rxy = - 0.507; p = 0.197; R-2 = 0.2568; y = 60.323x + 8.7366). It can be concluded that Jordan's Aleppo pine populations maintained a moderate level of genetic diversity with marked intra-population than inter-population differentiation. The low genetic differentiation among natural populations can be attributed to an effective gene flow among populations.
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| 10. |
- Vasaitis, Rimvydas
(författare)
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Long-term pathological consequences of resin tapping wounds on stems of Scots pine (Pinus sylvestris L.)
- 2022
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 36, s. 1507-1514
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Tidskriftsartikel (refereegranskat)abstract
- Key message After 5-6 decades since inflicting resin tapping wounds, overmature (> 120 years old) Pinus sylvestris stems remain undecayed and vigorous. Overmature trees of Pinus sylvestris bearing large wounds made by resin tapping decades ago are still present in woodlands of south-eastern Baltic Sea region. The aim of the present study was to investigate health condition of those trees focusing on fungal infections and to estimate impact of the injury on radial stem growth. The study was conducted in Latvia in three overmature stands of P. sylvestris, resin-tapped in 1950-1970 s. On the studied ninety 120-167-year-old trees, exposed sapwood constituted from 1140 to 7755 cm(2) per individual stem. Of the 127 wounds sampled, 52 (41%) showed wood discoloration. The discoloration in its extent was limited, expanding beyond wound margins approx. 1 (max 3) cm in radial, and 6-7 cm in longitudinal directions. Of the 127 wood samples/wounds subjected to fungal isolations, 96% resulted in fungal growth, yielding 236 fungal isolates that represented 47 fungal taxa. The most common among macro-fungi was basidiomycete Porodaedalea pini, which was isolated from 9% of stems. The fungus is currently classed not as a tree pathogen, but instead as an indicator species for woodland sites to be considered for nature conservation. Data from tree ring widths have revealed that tree reacted to the resin tapping injury by increasing radial increment of the un-affected part of the circumference of the stem. Current study demonstrated that even on the long term, resin tapping has little influence on health condition and vitality of P. sylvestris, even at the very old age. This should be considered as a supporting message in case resin taping practices in the region are to be revived.
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| 11. |
- Wiström, Björn, et al.
(författare)
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Intraspecific drought tolerance of Betula pendula genotypes: an evaluation using leaf turgor loss in a botanical collection
- 2021
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 35, s. 569-581
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Tidskriftsartikel (refereegranskat)abstract
- Key message The results showed a significant relationship between the potential evapotranspiration of the provenance collection site and the leaf turgor loss point and significant positive differences in drought tolerance between provenances and subspecies of B. pendula. The ecosystem services provided by urban trees make substantial contributions to the quality of urban living and securing resilience towards the challenges posed by a changing climate. Water deficits are a major abiotic stress for trees in urban environments and, in many regions, this stress is likely to be amplified under future climate scenarios. Although wide variation in drought tolerance exists at the species level, many species also show substantial intraspecific variation in drought tolerance. The aim of this study is to evaluate how drought tolerance, inferred from the water potential at leaf turgor loss point (psi(P0)), varies in Betula pendula from different geographical origins and determine if the observed drought tolerance can be related to the local climate and seasonal water balance from the provenance of origin, despite the trees now being established in similar soil and climatic conditions within a single botanical collection. Six subsp. betula, five subsp. mandshurica and two subsp. szechuanica were evaluated, giving a total of 12 different provenances. The results showed a significant relationship between the potential evapotranspiration of the provenance collection site and the leaf turgor loss point and significant positive differences in drought tolerance between provenances and subspecies of B. pendula. By directing efforts towards identifying more drought-tolerant genotypes, it will be possible to diversify the palette of trees that could confidently be integrated by urban tree planners and landscape architects into the urban landscape. The results of this study on different ecotypes of B. pendula clearly show that it is possible to find more drought-tolerant plant material.
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