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Abiotic and Biotic Stress Responses in Trees Species

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A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecophysiology and Biology".

Deadline for manuscript submissions: 29 July 2025 | Viewed by 10471

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Special Issue Editors

Dr. Hou-Ling Wang

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Guest Editor

State Key Laboratory of Tree Genetics and Breeding, National Engineering Research Center of Tree Breeding and Ecological Restoration, College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China
Interests: abiotic stress; leaf senescence; drought; poplar; hormone regulation; genome editing
Special Issues, Collections and Topics in MDPI journals

Dr. Liu-Qiang Wang

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Guest Editor

State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China
Interests: abiotic stress; hormone regulation; tree genetic breeding
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Tree species, serving as foundational component of terrestrial ecosystems, play a crucial role in preserving biological diversity, regulating climate, conserving soil, protecting water sources, and maintaining ecological environments. Moreover, tree species provide wood and various wood-derived products. Yet, trees possess distinctive woody structures that necessitate the absorption of water and nutrients from the soil to support photosynthetic canopies that can reach heights of several tens of meters. The growth and development of trees are vulnerable to abiotic stress, including drought, soil salinity, heavy metal ion stress, and extreme temperatures. Furthermore, climate change, monocultures of forest trees, and anthropogenic activities have introduced risks to trees by exposing them to biotic stresses such as pests and diseases. This Special Issue aims to provide a comprehensive overview of the latest advancements in the research field of abiotic and biotic stress in tree species. This Special Issue aims to present selected contributions focusing on advancements in stress sensing, signaling transduction, phytohormone regulation, multilayered regulation of stress, multi-omics, and crosstalk regulation between abiotic and biotic stress.

Potential topics include, but are not limited to:

Stress sensing:

Drought;
Salinity;
Temperature;
Ionic stress;
Disease;
Pests.

Signaling transduction:

Reactive oxygen species (ROS) signaling;
Ca²⁺ signaling;
Protein phosphorylation or ubiquitination;
Systemic or local signaling.

Phytohormone regulation:

ABA-dependent or ABA-independent stress responses;
JA signaling and response to insects;
SA signaling and response to diseases;
ETH signaling and response to stress.

Multilayered regulatory of stress:

Chromatin-mediated regulation;
Transcriptional regulation;
Post-transcriptional regulation;
Translational regulation;
Post-translational regulation.

Multi-omics regulation of abiotic and biotic stress:

Genomics and transcriptomic regulation;
Proteomics;
Metabolomics;
Other-omics (lipidomics, glycomics, ionomics).

Crosstalk between abiotic and biotic stress responses:

Phytohormone mediates stress responses crosstalk;
MAP-kinase cascades mediate stress signaling crosstalk;
Roles of ROS between biotic and abiotic stress crosstalk.

Dr. Hou-Ling Wang
Dr. Liu-Qiang Wang
Guest Editors

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Keywords

drought
salt
cold
temperature
disease
pests
response
signaling
phytohormone

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Research

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20 pages, 24961 KiB

Open AccessArticle

Chromosome-Level Genome Assembly of Myricaria laxiflora and Identification of Candidate MylAP2/ERF Genes Involved in Flooding Stress

by Weibo Xiang, Linbao Li, Guoli Li, Guiyun Huang, Bicheng Dun, Junchen Wang, Huiyuan Chen, Xiaobo Ma, Haibo Zhang, Zhiqiang Xiao, Jihong Liu, Zhen Yang and Di Wu

Forests 2025, 16(2), 295; https://doi.org/10.3390/f16020295 - 8 Feb 2025

Viewed by 587

Abstract

M. laxiflora is an endangered plant that grows in the Yangtze River floodplain of China and often suffers from flooding stress. Due to the lack of a reference genome for M. laxiflora, the molecular regulatory mechanism of waterlogging stress in this plant remains unclear. In this study, we report a high-quality reference genome of M. laxiflora with a size of 1.29 Gb. A total of 23,666 gene-encoding proteins and 5457 ncRNAs were predicted in this reference genome. A comparative genome analysis revealed that 902 and 4299 gene families significantly expanded and contracted, respectively, in M. laxiflora. The expansions of the 902 gene families were significantly related to the “response to stress”, “response to abiotic stimulus”, and “response to oxygen-containing compounds” pathways. In the M. laxiflora genome, 101 MylAP2/ERF genes were identified and divided into five subgroups. Several MeJA-, ABA-, and hypoxia-responsive elements were found in the promoter regions of these MylAP2/ERF genes. According to the transcriptome data analysis, 74 MylAP2/ERF genes responded to flooding stress. Moreover, three genes (MylAP2/ERF49/78/91) that belong to the same branch as the RAP2.2 gene exhibited different expression trends under flooding stress. Our results provide valuable information on the molecular regulatory mechanism of flooding stress in M. laxiflora. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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14 pages, 5604 KiB

Open AccessArticle

Dendroclimatology of Cedrela fissilis Vell. and Copaifera langsdorffii Desf. in an Urban Forest Under Cerrado Domain

by Larissa da Silva Bueno dos Santos, Letícia Seles de Carvalho, José Guilherme Roquette, Matheus Marcos Xavier de Souza, Gabriel Bazanela de Agostini, Ronaldo Drescher, Jaçanan Eloisa de Freitas Milani and Cyro Matheus Cometti Favalessa

Forests 2025, 16(2), 289; https://doi.org/10.3390/f16020289 - 8 Feb 2025

Viewed by 624

Abstract

The study is about the influence of climate change on tree growth in urban forests in Cuiabá, Mato Grosso, Brazil, using dendrochronology. The study focuses on two species, Cedrela fissilis Vell. and Copaifera langsdorffii Desf., both with dendrochronological potential. Samples were collected from an urban forest fragment, and local (temperature and precipitation) and global (ocean surface temperature—SST and Niño 3.4 index) meteorological data were analyzed to correlate with ring width. The methodology involved collecting, preparing, polishing, and marking the rings. The data series were analyzed using the COFECHA, Arstan, and CooRecorder programs to verify the accuracy of ring dating and SAS program for correlations with climatic variables. Both species exhibited good correlations between growth rings and climatic conditions. Cedrela fissilis and Copaifera langsdorffii were positively correlated with precipitation during the dry season and generally negatively correlated with temperatures. Negative correlations were identified with SST and Niño 3.4 for both species. These results are important for understanding how urban forests respond to climate change and how the study of growth rings can be used to predict the future impacts of these changes on plant species. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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18 pages, 4986 KiB

Open AccessArticle

Genome-Wide Investigation and Expression Analysis of AP2 Gene Subfamily Reveals Its Evolution and Regulatory Role Under Salt Stress in Populus

by Zhengbo Wang, Xiaolin Liang, Ziyuan Hao, Qi Feng, Hongying Li and Yingli Liu

Forests 2025, 16(1), 94; https://doi.org/10.3390/f16010094 - 8 Jan 2025

Viewed by 617

Abstract

The APETALA2/ethylene-responsive factor (AP2/ERF) is a well-researched superfamily of plant transcription factors. The APETALA2 (AP2) subfamily is essential for plant growth and development. However, a systematic analysis of the AP2 subfamily in poplar has yet to be conducted. This study identified 29 AP2 genes in the poplar genome, classifying them into three clades—euAP2, euANT, and basalANT based on evolutionary relationships. These genes are distributed across 12 chromosomes and one scaffold. Results from the syntenic analysis suggest that whole-genome duplication events are the primary factors driving the expansion of the AP2 subfamily in poplar. Cis-element analysis reveals that numerous PtAP2 genes possess hormone-related cis-elements. These genes also contain cis-elements linked to plant development and stress responses. PtAP2s from different clades exhibit significantly tissue-specific expression patterns in poplar. Gene expression levels in the euAP2 clade are significantly higher than in the euANT and basalANT clades across various tissues, with basalANT showing the lowest expression. Through RT-qPCR and recombinant Saccharomyces cerevisiae assays under salt stress, it was discovered that the majority of AP2 genes showed a negative response in salt stress regulation in poplar trees. In conclusion, this study offers valuable insights into salt tolerance in poplar trees and the role of AP2 genes under salt stress conditions. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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17 pages, 2925 KiB

Open AccessArticle

Simulated Warming Increases Litter Decomposition and Release Rates of Some Metallic Elements and Recalcitrant Components in Different-Aged Chinese Fir Plantations

by Lixian Zhang, Wenjuan Guo, Yulong Chen, Zhihao Li, Qi Liu, Kate V. Heal, Shubin Li and Lili Zhou

Forests 2024, 15(12), 2151; https://doi.org/10.3390/f15122151 - 6 Dec 2024

Viewed by 888

Abstract

With global warming, understanding the effect of elevated temperature on the decomposition of Chinese fir needle litter has significant implications for nutrient cycling, yield, and management of economically important Chinese fir plantations. We conducted simulated warming decomposition experiments in incubators at 25 °C, 30 °C, and 35 °C on Chinese fir needle litter from middle-aged, mature, and overmature stands. Changes in litter mass and concentrations of some metallic elements and recalcitrant components were measured in litter sampled at different decomposition time-steps up to 264 days (d). Warming to 35 °C significantly increased the mass loss rate of needle litter from overmature stands throughout the experiment (except at 72 d). The effect of warming on litter mass loss rate for middle-aged and mature stands was lower and is attributed to higher litter quality in these stands. Compared to 25 °C, warming to 30 °C and 35 °C increased the needle litter decomposition rate across all developmental stages by 17.3% and 48.3%, respectively. Potassium (K), calcium (Ca), and magnesium (Mg) were mostly released during needle litter decomposition in all Chinese fir developmental stages. Lignin, condensed tannins, total phenols, and cellulose were enriched in needle litter, while the release of hemicellulose from near the start of the decomposition experiment was attributed to its lower molecular weight compared with other carbohydrates in litter. Compared with 25 °C, warming to 35 °C increased the release rates from litter of K, Ca, and Mg by 14.7%, 24.6%, and 21.5%, and the release rates of lignin, total phenols, cellulose, and hemicellulose by 7.5%, 8.8%, 10.4%, and 13.7%. Needle litter iron (Fe), aluminum (Al), and sodium (Na) in different development stages and manganese (Mn) in the overmature stands were mostly enriched during the experiment. Warming significantly promoted the enrichment of Fe, Al (except for mature stands), and Na, and reduced the enrichment of Mn. In summary, the sensitivity of needle litter to temperature in overmature stands is higher than that in middle-aged and mature stands, suggesting that forest managers can extend the rotation length of Chinese fir plantations to increase the yield of large-diameter timber, litter decomposition, and ecosystem nutrient return. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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14 pages, 3326 KiB

Open AccessArticle

The bHLH Transcription Factor PubHLH66 Improves Salt Tolerance in Daqing Poplar (Populus ussuriensis)

by Dandan Li, Jindan Wang, Yuxin Pan, Hui Wang, Xinyao Dang, Shihao Zhao and Yucheng Wang

Forests 2024, 15(11), 2051; https://doi.org/10.3390/f15112051 - 20 Nov 2024

Viewed by 834

Abstract

Elevated salinity negatively impacts plant growth and yield, presenting substantial challenges to agricultural and forestry productivity. The bHLH transcription factor family is vital for plants to cope with various abiotic stresses. However, it remains uncertain whether bHLH transcription factors can regulate salt stress in Populus ussuriensis. In the following study, a salt-induced bHLH transcription factor PubHLH66 was identified from P. ussuriensis. PubHLH66 has a typical and conserved bHLH domain. Subcellular localization and yeast two-hybrid (Y2H) assays confirmed that it is a nucleus-localized transactivator and the activation region is located at the N-terminus. PubHLH66-OE and PubHLH66-SRDX transgenic P. ussuriensis were obtained through Agrobacterium-mediated leaf disc transformation. Morphological and physiological results demonstrated that PubHLH66-OE enhanced salinity tolerance, as indicated by reduced electrolyte leakage (EL), malondialdehyde (MDA), and H₂O₂ levels, along with increased proline contents and activities of peroxidase (POD) and superoxide dismutase (SOD). In contrast, PuHLH66-SRDX poplar showed decreased salt tolerance. Quantitative real-time PCR (RT-qPCR) confirmed that PubHLH66 enhanced salt tolerance by regulating the expression of genes such as PuSOD, PuPOD, and PuP5CS, resulting in reduced reactive oxygen species (ROS) accumulation and an improved osmotic potential. Thus, PubHLH66 could be a candidate gene for molecular breeding to enhance salt tolerance in plants. These results laid a foundation for exploring the mechanisms of salt tolerance in P. ussuriensis, facilitating the development of more salt-tolerant trees to combat the increasing issue of soil salinization globally. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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16 pages, 5251 KiB

Open AccessArticle

Identification of Picea mongolica LEA Gene Family Implicates PmLEA25 in Drought Resistance

by Yaping Wang, Jiaqi Li and Yu’e Bai

Forests 2024, 15(11), 1988; https://doi.org/10.3390/f15111988 - 11 Nov 2024

Viewed by 905

Abstract

Picea mongolica is a rare and valuable tree species in China, having high tolerance for drought, cold, and sand burial. The late embryogenesis abundant protein (LEA protein) is a crucial transcription factor that plays a key role in both plant embryonic development and stress response. LEA genes have, however, not yet been reported in P. mongolica. In this study, through the analysis of genome data from Picea abies and transcriptome data from P. mongolica, a total of 49 PmLEAs were discovered and categorized into eight subfamilies based on their Pfam domain and phylogenetic relationship. RNA-Seq research revealed that 37 PmLEAs were differentially expressed at various stages of embryonic development. Using qRT-PCR, we found that most PmLEAs responded strongly to drought stress, with genes in the same subfamily exhibiting identical expression patterns. In particular, PmLEA25 is the most highly induced by drought treatment. Furthermore, we heterologously transformed PmLEA25 into Arabidopsis. The overexpression of PmLEA25 remarkably increased the germination rate, root length, and antioxidant capacity in Arabidopsis under drought treatment, compared with WT. The results serve as a point of reference for gaining a deeper comprehension of the function of PmLEA25 in the molecular process of stress resistance in P. mongolica. Additionally, they offer significant genetic materials for the purpose of breeding stress-resistant spruce species. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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14 pages, 6742 KiB

Open AccessArticle

Exploring Functional Gene XsPDAT1’s Involvement in Xanthoceras sorbifolium Oil Synthesis and Its Acclimation to Cold Stress

by Juan Wang, Hongqian Ren, Zetao Shi, Fesobi Olumide Phillip, Sisi Liu, Weiyang Zhang, Xingqiang Wang, Xueping Bao and Jinping Guo

Forests 2024, 15(10), 1822; https://doi.org/10.3390/f15101822 - 18 Oct 2024

Viewed by 856

Abstract

Phospholipid: diacylglycerol acyltransferase (PDAT) is crucial in triacylglycerol (TAG) synthesis as it represents the final rate-limiting step of the acyl-CoA-independent acylation reaction. PDAT not only regulates lipid synthesis in plants, but also plays an important function in improving stress tolerance. In this study, the full-length coding sequence (CDS) of XsPDAT1, totaling 2022 base pairs and encoding 673 amino acids, was cloned from Xanthoceras sorbifolium. The relative expression of XsPDAT1 was significantly and positively correlated with oil accumulation during seed kernel development; there were some differences in the expression patterns under different abiotic stresses. Transgenic Arabidopsis thaliana plants overexpressing XsPDAT1 were obtained using the Agrobacterium-mediated method. Under low-temperature stress, the transgenic plants exhibited a smaller decrease in chlorophyll content, a smaller increase in relative conductivity, and a larger increase in POD enzyme activity and proline content in the leaves compared with the wild type. Additionally, lipid composition analysis revealed a significant increase in unsaturated fatty acids, such as oleic (C18:1) and linoleic (C18:2), in the seeds of transgenic plants compared to the wild type. These results suggest that XsPDAT1 plays a dual role in regulating the ratio of fatty acid composition and low-temperature stress in plants. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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14 pages, 11795 KiB

Open AccessArticle

Molecular Cloning of QwMYB108 Gene and Its Response to Drought Stress in Quercus wutaishanica Mayr

by Xuefei Zhao, Ying Sun, Yong Wang, Di Shao, Gang Chen, Yiren Jiang and Li Qin

Forests 2024, 15(9), 1557; https://doi.org/10.3390/f15091557 - 4 Sep 2024

Viewed by 793

Abstract

Drought is a significant environmental limiting factor that restricts the growth of Quercus wutaishanica Mayr. The MYB transcription factor plays a wide role in controlling the growth of plants. In this study, the QwMYB108 gene was cloned and the bioinformatics was analyzed, and we examined how QwMYB108 responded to various gradient drought stresses. The results demonstrated that QwMYB108 encoded 275 amino acids using an 828 bp open reading frame. Subcellular localization indicated that the gene was located in the nucleus. Phylogenetic analysis showed that QwMYB108 was close to Q. robur, and that the highest level of expression was found in leaves, which was significantly different from other tissues. The expression of QwMYB108 increased as the stress degree rose when drought stress was present, and there was a significant difference between severe drought stress and other gradient stress. In this study, the function of QwMYB108 in drought stress response was investigated, and the drought response function gene of Q. wutaishanica was further explored to provide a theoretical basis. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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11 pages, 2647 KiB

Open AccessArticle

Deciphering the Regulatory Mechanism of PmMYB21 in Early Flowering of Prunus mume through Dap-Seq and WGCNA Analysis

by Xi Yuan, Ran He, Hui Zhang, Dongyan Liu, Donghuan Liu, Zhihong Niu, Yu Zhang and Xinli Xia

Forests 2024, 15(8), 1300; https://doi.org/10.3390/f15081300 - 25 Jul 2024

Viewed by 1197

Abstract

Prunus mume Siebold & Zucc (mei) is a horticulturally important fruit tree that undergoes anthesis in winter. Therefore, its flowering process is challenged by low-temperatures conditions. The transcription factor (TF) MYB21 is pivotal in regulating the flowering process, and particularly functions in petal expansion and filament elongation. However, the regulatory mechanism of PmMYB21 in mei remains unknown. To breed early-flowering cultivars, a deeper understanding of PmMYB21-regulated genes is essential. We employed DNA affinity purification sequencing (Dap-seq) to identify downstream genes bound by PmMYB21. The results revealed the promoter region is the primary binding region of PmMYB21, and the AGTTAGGTARR motif (motif1) is the predominant binding sequence type. Our analysis identified 8533 genes that are potentially bound by PmMYB21 with the motif1 sequence type, within the promoter region. These genes are involved in biological processes critical to flowering. Further refinement of candidate genes was achieved through Weighted Gene Co-expression Network Analysis (WGCNA), which identified the co-expressed genes of PmMYB21 during flowering activity. Integrating Dap-seq and WGCNA data, we narrowed down the candidate gene list to 54, with a focus on 4 MADS-box genes and 2 hormone signaling genes that are crucial to the flowering process under low-temperature conditions. This study offers valuable insights into the molecular underpinnings of PmMYB21’s role in the low-temperature flowering regulation of mei, paving the way for the development of new cultivars adapted to early blooming. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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18 pages, 3901 KiB

Open AccessArticle

Physiological Response to Low-Temperature Stress and Cold Resistance Evaluation of Ziziphus jujuba var. spinosa Clones from Different Provenances

by Biao Li, Yuncheng Zhang, Ying Kang, Yijin Wang, Ruilin Liu, Qingbai Liu and Shengjun Dong

Forests 2024, 15(7), 1130; https://doi.org/10.3390/f15071130 - 28 Jun 2024

Cited by 4 | Viewed by 1223

Abstract

To investigate the low-temperature adaptability of different provenances of Ziziphus jujuba var. spinosa, we used 21 clones from seven provenances as experimental materials and observed the changes in physiological and biochemical indicators and the characteristics of anatomical structures under low-temperature stress. A comprehensive evaluation of their cold resistance was conducted using the membership function method. As the temperature decreased, the relative electrical conductivity (REC) of clone 89 became stable and had the lowest LT₅₀ value (−44.04 °C). The cold-resistant Z. jujuba var. spinosa had a higher bound water/free water (BW/FW) ratio and antioxidant enzyme activity and accumulated large quantities of osmotic regulatory substances. Higher xylem, phloem, and xylem–cortex ratios and greater conduit density enhanced the cold resistance of Z. jujuba var. spinosa. The membership function values of clones 89, 90, 91, 604, and 612 were greater than 0.6, indicating that they could be evaluated as resources with the potential for low-temperature resistance. The cold resistance rankings for the different provenances were as follows: Kazuo, Liaoning > Jiaxian, Shaanxi > Fuxing, Heibei > Changqing, Shandong > Neiqiu, Heibei > Yanchuan, Shaanxi > Xiaxian, Shanxi. These results provide a scientific basis for the rapid and accurate identification of cold resistance in Z. jujuba var. spinosa resources and the breeding and cultivation of new cold-resistant varieties of this subspecies. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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20 pages, 4032 KiB

Open AccessReview

Climatic Influence on Growth Performance of Abies spectabilis in the Himalayas

by Krishna Prasad Pandey, Camilla Wellstein, Achim Bräuning and Dinesh Raj Bhuju

Forests 2025, 16(3), 473; https://doi.org/10.3390/f16030473 - 8 Mar 2025

Viewed by 874

Abstract

Climate change has affected forest ecosystems across the world over the past century. However, its impact is particularly high in the Himalayas due to increasing temperatures, extreme precipitation events, and regional droughts. In this context, a review of the current stage of research was deemed necessary to understand the adaptation of a key conifer species to climate variability in the Central Himalayas. Hence, we conducted a systematic review of published peer-reviewed journal articles addressing the growth performance of Abies spectabilis (D. Don) Spach in the Central Himalayas. From this review, three main patterns of climate response have emerged: a positive correlation of radial tree growth with temperature of the current and previous growing seasons, tree growth limitation by winter temperature, and by temperature or moisture in the pre-monsoon season. Overall, results indicate an elevation-dependent temperature sensitivity, a crucial role of moisture availability, and seasonal shifts in climate–growth relationships, reflecting the species’ adaptability to changing climate conditions. Our review revealed that studies on elevation-dependent adaptation of wood anatomical traits by A. spectabilis are still rare. The tree-ring growth of this species shows a complex response to climate variability, with increasing as well as decreasing growth trends across its distribution range. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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21 pages, 6718 KiB

Open AccessReview

Early Warning Signs in Tree Crowns as a Response to the Impact of Drought

by Goran Češljar, Ilija Đorđević, Saša Eremija, Miroslava Marković, Renata Gagić Serdar, Aleksandar Lučić and Nevena Čule

Forests 2025, 16(3), 405; https://doi.org/10.3390/f16030405 - 24 Feb 2025

Viewed by 497

Abstract

The interaction between trees’ water needs during drought and the signals that appear in their canopies is not fully understood. The first visually detectable signs, which we describe as early warning signals in tree canopies, are often not noticeable at first glance. When these signs become widely apparent, tree decline is already underway. In this study, we focus on identifying early visible signs of drought stress in the tree crowns, such as very small leaves, premature needle/leaf discolouration and abscission, and defoliation. We provide guidance on recognising initial signs, offer specific examples, and comprehensively analyse each signal. Our focus is on signs in the tree crowns that appear during intense and prolonged droughts, which we confirmed by calculating the Standardised Precipitation Evapotranspiration Index (SPEI). Our findings are based on 20 years (2004–2024) of continuous fieldwork and data collection from permanent sample plots in Serbia, which was conducted as part of the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). We also conducted a comprehensive review of the literature and key findings related to the early signs we address. This research was further motivated by the signs observed in the tree crowns during the summer of 2024 due to extreme climatic events, which classify this year as one of the hottest recorded in Serbia. However, we still cannot conclusively determine which specific trees will die back based solely on these early warning signals, as some trees manage to withstand severe drought conditions. Nonetheless, the widespread appearance of these indicators is a clear warning of significant ecosystem instability, potentially leading to the decline of individual trees or larger groups. Full article

(This article belongs to the Special Issue Abiotic and Biotic Stress Responses in Trees Species)

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