New Knowledge in Dragon Tree Research

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

Deadline for manuscript submissions: closed (28 February 2023) | Viewed by 17989

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Guest Editor
Department of Forest Botany, Dendrology and Geobiocoenology (FFWT), Mendel University, Zemedelska 1, 61300 Brno, Czech Republic
Interests: forestry; woody plants ecology; dragon trees; frankincense trees; nature conservation; Socotra
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Guest Editor
1. Centre for Academic Heritage and Archives & Ghent University Botanical Garden, Ghent University, Ghent, Belgium
2. Department of Forest Botany, Dendrology and Geobiocoenology (FFWT), Mendel University, Brno, Czech Republic
Interests: taxonomy and systematics; aquatic biodiversity; biological invasions; Cladocera; evolution; biodiversity conservation
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Department of Environmental Biology, Sapienza University of Roma, 00815 Roma, Italy
Interests: biodiversity conservation; climate change impact; ecological restoration; plant species; vegetation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Only a few species among more than 60–100 species of the genus Dracaena reach the arborescent form. Arborescent dragon trees are Tertiary relict species, the ecosystems (woodlands and very rare forests) containing these life forms belong to one of the oldest surviving ecosystems around the world. Most species are endemic with limited (often island) distribution. Dragon trees are also an important source of non-timber products; the trees produce a red resin called dragon’s blood, which has been used for coloring and medical purposes since ancient times. Thus, these trees are considered to have high cultural and natural values. The main objective of the Special Issue is to present the latest results of research focused on species of the dragon tree group, and to determine main gaps for future investigation as the basis for conservation management. This Special Issue will accept studies from broad research topics related to dragon trees.

Please note that this Special Issue is organized in cooperation with the 2nd Dragon Tree Consortium World Conference and welcomes submissions from participants of this conference, held at Ghent University Botanical Garden, Ghent, Belgium, in September 2021. Further information is available at this link: https://fraxinus.mendelu.cz/tropicalforestry/friends-of-soqotra-dragon-tree-conference-ghent/.

Prof. Dr. Petr Maděra
Dr. Kay Van Damme
Prof. Dr. Fabio Attorre
Guest Editors

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Keywords

  • dragon tree group
  • taxonomy
  • evolution
  • morphology
  • anatomy
  • eco-physiology
  • growth
  • inventory
  • ecology
  • ethnobotany
  • resin
  • species specific relationships
  • nature conservation

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Published Papers (7 papers)

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Research

23 pages, 4272 KiB  
Article
Transcriptomic Analysis Reveals the Involvement of Flavonoids Synthesis Genes and Transcription Factors in Dracaena cambodiana Response to Ultraviolet-B Radiation
by Yue-E Liang, Hao Zhang, Jiahong Zhu, Hao Wang, Wenli Mei, Bei Jiang, Xupo Ding and Haofu Dai
Forests 2023, 14(5), 979; https://doi.org/10.3390/f14050979 - 10 May 2023
Cited by 4 | Viewed by 1989
Abstract
Ultraviolet-B (UV-B) radiation is a major abiotic stress that dragon trees are exposed to during their growth and development; however, it is also an environmental signal perceived by plants that affects the flavonoid pathway. Previous studies have demonstrated that amounts of flavonoids are [...] Read more.
Ultraviolet-B (UV-B) radiation is a major abiotic stress that dragon trees are exposed to during their growth and development; however, it is also an environmental signal perceived by plants that affects the flavonoid pathway. Previous studies have demonstrated that amounts of flavonoids are contained in dragon tree resin, otherwise known as dragon’s blood. However, the traits and mechanism involved in the UV-B-mediated increase in flavonoids in dragon trees are still unknown. Here, we studied the response of Dracaena cambodiana under full solar UV-B radiation. The results showed that the contents of total flavonoids in D. cambodiana significantly increased after UV-B radiation exposure. Then, the transcriptome was used for determining the interactive mechanism of flavonoid accumulation and UV-B stress. Differential expression analyses identified 34 differentially expressed genes (DEGs) involved in flavonoid synthesis; specifically, 24 of the identified DEGs were significantly up-regulated after UV-B radiation exposure. In addition, 57 DEGs involved in Ca2+/kinase sensors, 58 DEGs involved in ROS scavenging and the plant hormone pathway, and 116 DEGs transcription factors in 5 families were further identified and analyzed. Finally, we deduced the potential mechanism of UV-B-promoting flavonoid formation to neutralize ROS damage derived from UV-B radiation in D. cambodiana based on the gene co-expression network and previous studies from other plants. Considering that wild dragon tree populations are currently highly threatened by anthropogenic and natural stressors, the interactive studies between D. cambodiana plants and UV-B radiation provide valuable information toward understanding the mechanism of dragon’s blood formation and help us reveal the evolution of D. cambodiana, with the eventual goal of aiding in the global conservation of this precious biological resource. Full article
(This article belongs to the Special Issue New Knowledge in Dragon Tree Research)
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11 pages, 6723 KiB  
Article
Age Estimation of Dracaena cinnabari Balf. f. on Socotra Island: A Direct Method to Determine Its Lifespan
by Lucie Bauerová, Petr Maděra, Martin Šenfeldr and Hana Habrová
Forests 2023, 14(4), 840; https://doi.org/10.3390/f14040840 - 20 Apr 2023
Cited by 2 | Viewed by 2409
Abstract
Background: Dracaena cinnabari is a monocot species that does not form annual tree rings; thus, its age can only be estimated. This species is threatened by low natural regeneration, with an evident absence of younger individuals most likely caused by overgrazing; therefore, knowing [...] Read more.
Background: Dracaena cinnabari is a monocot species that does not form annual tree rings; thus, its age can only be estimated. This species is threatened by low natural regeneration, with an evident absence of younger individuals most likely caused by overgrazing; therefore, knowing trees’ ages is important for possible conservation strategies; Methods: Data collection was conducted on the Firmihin Plateau on Socotra Island (Yemen) in 2021, and the diameter at breast height (DBH) of 1077 individuals was measured, the same as those established on monitoring plots 10 years before the current measurement. The 10-year radial stem increment and DBH obtained in 2011 served as a basis for the linear model from which the equations for the age calculation were derived. Results and Conclusions: A direct model of age estimation for D. cinnabari was developed. According to the fit model, the age in the first (10.1–15 cm) DBH class was estimated to be 111 years, while that in the last DBH class (90.1–95 cm) was estimated to be 672 years. The results revealed that the previously used indirect methods for D. cinnabari age estimation were accurate. Full article
(This article belongs to the Special Issue New Knowledge in Dragon Tree Research)
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17 pages, 16167 KiB  
Article
UAV Inventory of the Last Remaining Dragon Tree Forest on Earth
by Petr Vahalík, Kay Van Damme, Rostislav Nétek, Hana Habrová, Jana Tulková, Klára Lengálová, Lucie Zejdová, Elizaveta Avoiani and Petr Maděra
Forests 2023, 14(4), 766; https://doi.org/10.3390/f14040766 - 8 Apr 2023
Cited by 5 | Viewed by 2686
Abstract
The last remaining Dragon Tree Forest on Earth survives on a small plateau (Roqeb di Firmihin) in Socotra Island (Yemen). The Socotran Dragon’s Blood Tree (Dracaena cinnabari Balf. f.) is endemic to the Socotra Archipelago UNESCO World Heritage Site. Being a culturally [...] Read more.
The last remaining Dragon Tree Forest on Earth survives on a small plateau (Roqeb di Firmihin) in Socotra Island (Yemen). The Socotran Dragon’s Blood Tree (Dracaena cinnabari Balf. f.) is endemic to the Socotra Archipelago UNESCO World Heritage Site. Being a culturally important and endangered tree species, its conservation is a priority. Despite this, a complete inventory of the Firmihin Dracaena forest (14.9 km2) has never been attempted before. We applied the use of unmanned aerial vehicles (UAVs) for the first time in conserving the Socotran Dragon’s Blood Tree. A pair of UAVs (small drones) were used during field surveys in 2021 to spatially describe individual tree positions, tree density, mortality, and the forest age structure. Aerial images were processed into a single orthophoto image of high spatial resolution (8 cm/pixel) used for detailed analysis. We applied image-enhancement techniques, used object-based classification, and corrected every entry manually during the inventory process. In total 35,542 individual living trees and 2123 uprooted trees were inventoried. The mean age of the forest, based on crown age (derived from crown size) was estimated at an average of ca. 300 years (291.5 years) with some individuals older than 500 years. Our analysis reveals that the trajectory of recent cyclones and the average direction of fallen trees in Firmihin are correlated, suggesting that intensified winds (as a result of global warming) catalyze the decline of the overmature forest. Our study illustrates the use of UAVs in collecting crucial data for the conservation and threat assessment of endangered tree species in Socotra, and regular drone inventories could be applied (e.g., after future cyclone events or landslides) to better evaluate the status of these vulnerable island ecosystems. Full article
(This article belongs to the Special Issue New Knowledge in Dragon Tree Research)
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12 pages, 3578 KiB  
Article
Identifying Suitable Restoration and Conservation Areas for Dracaena cinnabari Balf.f. in Socotra, Yemen
by Marcelo Rezende, Petr Maděra, Petr Vahalík, Kay Van Damme, Hana Habrová, Tullia Riccardi, Fabio Attorre, Michele De Sanctis, Grazia Sallemi and Luca Malatesta
Forests 2022, 13(8), 1276; https://doi.org/10.3390/f13081276 - 12 Aug 2022
Cited by 4 | Viewed by 2624
Abstract
We examine the distribution of Dracaena cinnabari, the Socotran Dragon’s Blood Tree, an endangered species endemic to the island of Socotra (Yemen)—and we propose an accessibility approach to its conservation, taking the proximity of local communities and land users into account. Using [...] Read more.
We examine the distribution of Dracaena cinnabari, the Socotran Dragon’s Blood Tree, an endangered species endemic to the island of Socotra (Yemen)—and we propose an accessibility approach to its conservation, taking the proximity of local communities and land users into account. Using the present occurrence of D. cinnabari, we applied a machine learning algorithm (random forest classifier) to estimate the potential distribution of the species across the island (overall validation accuracy of 0.91) based on available climatic and physiographic parameters. In parallel, we used an accessibility methodology to generate a map of the energy cost of accessing potential areas from the villages. This community-focused accessibility map, combined with the potential distribution map of Dracaena cinnabari, could contribute to decision-making processes related to long-term ecological restoration and reforestation activities. With our case study, we wish to emphasize that user-focused efforts and the implementation of sustainable land practices should play key roles in conserving endangered tree species. Full article
(This article belongs to the Special Issue New Knowledge in Dragon Tree Research)
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12 pages, 781 KiB  
Article
Nomenclature Notes and Typification of Names in Dracaena (Asparagaceae, Nolinoideae)
by Zhiyong Zhang, Muhammad Idrees, Xu Zheng, Yongqing Jiao and Zakaria H. Prodhan
Forests 2022, 13(8), 1237; https://doi.org/10.3390/f13081237 - 4 Aug 2022
Viewed by 2002
Abstract
Two new names, Dracaena neoparviflora and Dracaena ridleyii are proposed as replacement names for the illegitimate names D. parviflora Baker, and D. nutans Ridl., respectively, the latter being a later homonym of D. parviflora Willd. ex Schult.f., and D. nutans H.Jaeger. Lectotypes are [...] Read more.
Two new names, Dracaena neoparviflora and Dracaena ridleyii are proposed as replacement names for the illegitimate names D. parviflora Baker, and D. nutans Ridl., respectively, the latter being a later homonym of D. parviflora Willd. ex Schult.f., and D. nutans H.Jaeger. Lectotypes are designated for D.cambodiana, D. interrupta (synonym of D. camerooniana), D. oddonii (synonym of D. camerooniana), D. cantleyi, D. cinnabari, D. cuspidibracteata (synonym of D. congoensis), D. haemanthoides, D. litoralis (synonym of D. braunii), D. parviflora, D. novoguineensis, D. nutans, D. petiolata, D. reflexa var. linearifolia, D. reflexa var. angustifolia, D. steudneri, D. tessmannii (synonym of D. mannii), and D. viridiflora. The second-step lectotypications are made for D. camerooniana, D. bushii, D. glomerata, D. papahu (synonym of D. steudneri), D. talbotii (synonym of D. bicolor), D. vaginata (synonym of D. viridiflora), and D. xiphophylla. A neotype is designated for the name Aletris arborea (basionym of D. arborea). Full article
(This article belongs to the Special Issue New Knowledge in Dragon Tree Research)
12 pages, 10313 KiB  
Article
Effect of Different Presowing Treatments to Break Seed Dormancy and Seed Collection Methods on the Germination of Dracaena steudneri Schweinf. Ex Engl.
by Shiferaw Alem Munie, Hana Habrová, Kateřina Houšková and Lukáš Karas
Forests 2022, 13(8), 1232; https://doi.org/10.3390/f13081232 - 3 Aug 2022
Cited by 2 | Viewed by 2024
Abstract
Research Highlights: This study is focused on the germination of Dracaena steudneri Schweinf. Ex Engl. seeds using different presowing treatments. Background and Objectives: The study aimed to overcome the problem of breaking seed dormancy, to facilitate artificial regeneration for conservation and development purposes. [...] Read more.
Research Highlights: This study is focused on the germination of Dracaena steudneri Schweinf. Ex Engl. seeds using different presowing treatments. Background and Objectives: The study aimed to overcome the problem of breaking seed dormancy, to facilitate artificial regeneration for conservation and development purposes. The objectives of this study were (1) to evaluate the effect of different seed treatments in breaking seed dormancy of D. steudneri and (2) to assess the effect of the seed collection method (seeds collected on the ground vs. from the tree) on the germination of the seed. Materials and Methods: experimental study with different seed-dormancy-breaking treatments was carried out in a greenhouse and seed laboratory. T testing and one way analysis of variance (ANOVA) were used to analyse the data. Results: The applied seed treatments (hot water, cold water, sodium hypochlorite and nicking) did not improve the germination of the species, nor the breaking of seed dormancy. One-way ANOVA results also showed no significant differences between the different seed treatments and the control on the mean germination of the species in the greenhouse (p < 0.05). The t test result also revealed no significant differences in the mean germination between fallen seeds collected from the ground and in the tree crown (p < 0.05). The tetrazolium test results showed that the percentage of nonviable seeds was greater than that of the viable seeds. Conclusion: The different treatments for breaking seed dormancy did not improve the germination of seeds in the greenhouse (ranging from 0%–7%) nor in the seed laboratory (0%), which might be due to the intermediate characteristics of the seeds of this species. Therefore, we recommend that more research is undertaken on the seed ecophysiology of the species, in order to understand the mechanisms controlling its seed germination. Full article
(This article belongs to the Special Issue New Knowledge in Dragon Tree Research)
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11 pages, 1973 KiB  
Communication
Characterization of the Complete Chloroplast Genome Sequence of the Socotra Dragon`s Blood Tree (Dracaena cinnabari Balf.)
by Konrad Celiński, Joanna Sokołowska, Hanna Fuchs, Petr Maděra and Justyna Wiland-Szymańska
Forests 2022, 13(6), 932; https://doi.org/10.3390/f13060932 - 14 Jun 2022
Cited by 3 | Viewed by 2719
Abstract
The Socotra dragon`s blood tree (Dracaena cinnabari Balf.) is endemic to the island of Socotra in Yemen. This iconic species plays an essential role in the survival of associated organisms, acting as an umbrella tree. Overexploitation, overgrazing by livestock, global climate change, [...] Read more.
The Socotra dragon`s blood tree (Dracaena cinnabari Balf.) is endemic to the island of Socotra in Yemen. This iconic species plays an essential role in the survival of associated organisms, acting as an umbrella tree. Overexploitation, overgrazing by livestock, global climate change, and insufficient regeneration mean that the populations of this valuable species are declining in the wild. Although there are many studies on the morphology, anatomy, and physiology of D. cinnabari, no genomic analysis of this endangered species has been performed so far. Therefore, the main aim of this study was to characterize the complete chloroplast sequence genome of D. cinnabari for conservation purposes. The D. cinnabari chloroplast genome is 155,371 bp with a total GC content of 37.5%. It has a quadripartite plastid genome structure composed of one large single-copy region of 83,870 bp, one small single-copy region of 18,471 bp, and two inverted repeat regions of 26,515 bp each. One hundred and thirty-two genes were annotated, 86 of which are protein-coding genes, 38 are transfer RNAs, and eight are ribosomal RNAs. Forty simple sequence repeats have also been identified in this chloroplast genome. Comparative analysis of complete sequences of D. cinnabari chloroplast genomes with other species of the genus Dracaena showed a very high conservativeness of their structure and organization. Phylogenetic inference showed that D. cinnabari is much closer to D. draco, D. cochinchinensis, and D. cambodiana than to D. terniflora, D. angustifolia, D. hokouensis, and D. elliptica. The results obtained in this study provide new and valuable omics data for further phylogenetic studies of the genus Dracaena as well as enable the protection of genetic resources of highly endangered D. cinnabari. Full article
(This article belongs to the Special Issue New Knowledge in Dragon Tree Research)
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