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The study describes main biotopes of Socotra Island. The biotopes were distinguished and described during complex field observations on more than 250 localities of Socotra between years 1999-2004. Classification of biotopes is based on differences in physiognomy, structure and species composition of the vegetation component of present biocoenoses....
Contexts in source publication
Context 1
... fimbriatum, Grewia turbinata, Euclea divinorum etc., in the shrub layer Croton socotranus, Jatropha unicostata, Acacia pennivenia, Adenium obesum ssp. socotranum, Trichocalyx spp., Vernonia cockburniana (Fig 6). Characteristics: deciduous woodlands of the first vegetation zone on the southern coast on loess substrates. ...
Context 2
... W2, S2, P3, B1 Distribution: particularly in the fourth vegetation zone; sporadically also in the fifth vegetation zone in the Haggeher Mts. Type and intensity of anthropogenic impacts: the most suitable areas for the pasture of donkeys, cows but also of sheep and goats; originally, vegetation of shrubs and forests occurred obviously there. (Fig. ...
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Citations
... Socotra holds an extremely varied terrestrial and marine biodiversity, with a high level of endemism, according to insular ''disharmony" (Whittacker and Fernandez-Palacios, 2007). The long separation and the bioclimatic features led to the evolution of tropical and arid ecosystems with forest biotopes holding relict plants such as Dracaena cinnabari and the various species of Boswellia (Habrová and Buček, 2013), shrubby habitats and rocky landscapes flooded by transient watercourses, sometimes with high energy. Longstanding studies on Socotra have permitted to improve the conservation of their ecological peculiarity ending up with the designation of ''World Heritage Site -UNESCO 2010" in 2008 The terrestrial vertebrates of Socotra Islands include 30 species of reptiles, 27 of which endemic to Socotra archipelago (Razzetti et al., 2011), more than 220 species of birds, eleven of which endemic Suleiman, 2013, 2014;Porter and Suleiman, 2020), and a few species of mammals, mostly domesticated, semidomesticated or commensal species, with the exception of Suncus madagascariensis (Coquerel, 1848) and Viverricula indica Geoffroy, 1803, probably accidentally introduced by human activities, and four bat species, only one of them endemic to Socotra (Wranik, 1998;Benda et al., 2017). ...
... In the last twenty years, considering the importance of conserving these endemic trees, inventories combining field and remote sensing data have improved our knowledge of Dracaena cinnabari distribution. Eleven types of habitats were distinguished in Socotra where Dragon's Blood Trees occur [12]. The first remote sensing data evaluated the Dragon's Blood Tree populations on Socotra Island [13], concluding that land cover classes with an occurrence of this tree species comprise a total of 7230 ha. ...
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 km 2) 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.
... Okurkovník se vyskytuje v nadmořských výškách od 5 do přibližně 500 m n. m. v prvním a druhém vegetačním stupni (Habrová 2004;De Sanctis et al. 2013). Typickými vegetačními formacemi, ve kterých se okurkovník vyskytuje, jsou "vysoké křoviny se sukulenty", "vádí" a "nízké křoviny s krotonem a dávivcem", i když se může vyskytovat i v jiných typech vegetace (plantáže datlovníku, dračincové lesy, kadidlovníkové lesy, řídké zakrslé křoviny, podhorské pastviny, podhorské křoviny a zastavěná území) (Habrová a Buček 2013;Král a Pavliš 2006). D. socotranus, podle Červeného seznamu IUCN zranitelný druh , nemá dře vo použitelné pro palivo nebo konstrukce (Olson 2003). ...
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... Dracaena occurrence in the Ma'ala's Highland published byAttorre et al. (2007) [ 70 ].The last D. cinnabari place name in the Hagher is close to D. cinnabari population but the name is for a place without D. cinnabari trees and they don't know presence of tree in the place, another D. cinnabari place name was also recorded from Hagher towards To'ahor's campsite-outside or study area (communication with local people).In all investigated areas, there are still preserved some plant species accompanying dragon´s blood tree woodlands as Boswellia ameero, B. elongata, Buxanthus pedicellatus, Commiphora planifrons, Euphorbia socotrana or Euryops arabicus[93][94][95][96][97][98][99]. Occurrence of these plants can serve as an indirect indicators of previous D. cinnabari distribution according to the plant communities.Generally, the D. cinnabari place names seem to be associated with the current and potential distribution.The similar result was obtained byPérez (2003) [ 92 ] for Dracaena draco on Gran Canaria, in his map, there are 42 phytotoponyms; 2 names associated with existing D. draco occurrence, others are close to the current distribution of individual trees or in area of potential distribution. ...
Background
In this study, we present and analyze toponyms referring to Socotra Island’s endemic dragon’s blood tree (Dracaena cinnabari) in four areas of the Socotra Archipelago UNESCO World Heritage site (Republic of Yemen). The motivation is understanding of the past distribution of D. cinnabari trees which is an important part of conservation efforts by using ethnobotanical data. We assumed that dragon’s blood trees had a wider distribution on Socotra Island in the past.
Methods
This research was based on field surveys and interviews with the indigenous people. The place names (toponyms) were recorded in both, Arabic and indigenous Socotri language. We grouped all toponyms into five different categories according to the main descriptor: Terrain, Human, Plant, Water and NA (unknown). In addition, this study identified current and historical Arabic names of dragon’s blood trees of the genus Dracaena, through literature review.
Results
A total of 301 toponyms were recorded from the four study areas in Socotra Island. Among names related to plants, we could attribute toponyms to nine different plant species, of which six names referred to the D. cinnabari tree, representing 14.63% of total phytotoponyms in the category. Three historical naming periods prior to 2000 could be identified. The most commonly used Arabic name for dragon’s blood trees (D. cinnabari, D. serrulata. D. ombet) appears to be “ahrieb” "إعريهب", its resin “dum al-akhawin” “دم الأخوين”, while derived (mixed-cooked) products are called “edah” “إيدع”; while regionally different names can be found.
Conclusion
The place names that refer to D. cinnabari are herein suggested to represent remnant areas of once large populations. The toponyms may therefore support known hypotheses based on climate models that D. cinnabari had a wider distribution on Socotra Island in the past. This study also confirmed the historical importance of dragon’s blood
... This is only related to the productivity of such ecosystems and not to an increase in their biodiversity. The lowland areas are often actually strongly degraded, locally affected by overgrazing resulting in only a few browsetolerant or inedible species (Miller and Morris 2004;Van Damme and Banfield 2011;Scholte et al. 2011;Habrová and Buček 2013). Moreover, a significant reduction of productivity can be also caused by increasing soil erosion, which can be further exacerbated by landslides, in the steeper areas determined by the synergistic effect of heavy rainfalls and overgrazing (Fig. 8). ...
... Similar effects are known in islands in the Pacific, where the combination of prolonged drought, intensified rainfalls and grazing lead to erosion and desertification (Wairiu 2017). Soil erosion processes and strong degradation in Socotra have already been identified in local areas (Pietsch and Morris 2010;Habrová and Buček 2013), but this is the first time that the potential effect is shown at the scale of the entire Island. ...
Socotra, the largest of four islands in the Socotra archipelago (Yemen), is characterized by high geo-morphological and biological diversity. Traditional management of land resources has been impacted by cultural shifts, globalization and urban expansion. In addition, the island has been affected by climate impacts, such as droughts and recent cyclones causing significant economic and environmental damage. Our study presents an analysis of the dynamics of the vegetation on the island for the period 2001-2019 and highlights the status of different landscapes. We used Earth Observation techniques and the Normalized Difference Vegetation Index to assess land productivity dynamics basing on vegetation indexes derived from average resolution satellite images. The results show that although the arid landscapes of Socotra seem resilient, over 30% of the central mountainous areas of the Hageher (hosting a unique and high biodiversity) are decreasing in productivity , whereas in the lowlands (where plant diversity is relatively lower) productivity has increased significantly for the same time period, up to 40% in some areas. Given the difference in biological diversity of the sites, this study can help prioritize conservation areas and activities, which are crucial for Socotra's terrestrial environment. The methodology applied could be replicated for continuous monitoring in the future.
... Over large areas, there are small relict, isolated populations; while in other areas, D. socotranus is relatively abundant ). The typical land cover classes in which D. socotranus individuals are found are High Shrubland with Succulents, Wadi, and Low Croton-Jatropha Shrubland, although it can also be found in other vegetation types (Date Palm Plantations, Dracaena Woodland, Frankincense (Boswellia spp.) woodland, Sparse Dwarf Shrubland, Submontane Grassland, Submontane Shrubland, and Urban land; (Habrová and Buček 2013;Král and Pavliš 2006). Based on the vegetation units defined by De , D. socotranus has been found in Sterculia africana woodland, Boswellia elongata woodland, Croton socotranus shrubland and Jatropha unicostata-Adenium obesum shrubland. ...
We conducted a study throughout Socotra Island (Yemen) to investigate the distribution, population structure and regeneration potential of the endemic and threatened tree species Dendrosicyos socotranus, the Cucumber Tree. In total, 163 live trees (excluding seedlings) were found in all (24) investigated locations, covering an area of 96 km2. The height, stem circumference, fertility and coordinates of each tree were measured and data regarding the ecotope, land cover and natural regeneration were recorded. We estimated that there could be more than 6400 Cucumber Tree individuals among the populations on Socotra Island. The majority of the trees occur in the “high Shrubland with succulents” and “wadi” land cover classes. In general, the fertility of the trees is good, and natural regeneration occurred in 77% of the locations with adult trees; it was found that 16% of the individual trees regenerated. Our study, collecting data on the regeneration of the species and estimating the size of local populations for the first time, can be used for local conservation and future monitoring of this important, endangered Socotran endemic.
... Socotra hosts 843 vascular plant species (Brown and Mies 2012;Řepka et al. 2017), of which 37% are endemic (Miller and Morris 2004;Banfield et al. 2011). Tree species are distributed according to the geoclimatic features of the island Habrová and Buček 2013): in the basal areas, among the Croton socotranus shrubland, scattered trees of the rare Commiphora ornipholia, Euphorbia arbuscula, and Dendrosicyos socotrana are found. Hilly areas and escarpments host deciduous woodlands characterized mainly by Boswellia ameero, Boswellia elongata, Boswellia socotrana, Commiphora parvifolia, and Sterculia africana var. ...
Socotra Island, in the western Indian Ocean, harbors high biodiversity and endemism and makes up the largest part of the Socotra archipelago UNESCO World Heritage site. Its climatic, pedological, and geomorphological characteristics, together with the long geological isolation and inaccessibility, led to the flourishing of unique tree diversity, with great cultural and ecological value. Lately, trees on Socotra are facing new threats linked to the abandonment of traditional management practices, climate change impacts, and growing human pressure. This study assesses the relative influence of environmental factors and human activity as drivers of tree cover and density, which can be used to support land management policies for the conservation of this key local resource. Tree cover and density were assessed on a total of 3600 plots of 0.5 ha each, laid on a regular grid covering the entire area of the island through Collect Earth, a free open source software tool that allows an augmented visual interpretation of high-resolution satellite images. A total of 770,000 trees, with an average of 2.14 trees/ha, were estimated on the island. The collected data was validated by ground surveys in 26 plots. The relative influence of selected predictors (seven environmental, two anthropic) on tree cover and density was analyzed through logistic and survival regression. Tree cover and density were found to be impacted positively by steeper slopes, higher rainfall, and marked precipitation seasonality and negatively by relatively warmer temperatures and a higher sand content in the soil. Distance of each plot from the nearest road and settlement was calculated and neither of these anthropic predictors emerged as significant, indicating that the limited number of trees present are not currently as affected by anthropic pressure, but, instead, their presence is mostly limited by the harsh climatic and pedological factors. However, as human population and development increase, periods of drought rise, and extreme and random climatic events intensify, these additional stresses on the environment could negatively impact the availability of natural resources in the terrestrial environment. Lastly, potential recommendations to the existing conservation policies and Socotra Conservation Zoning Plan are discussed based on the results.
... Socotra is the largest island of the Socotra Archipelago situated at the boundary between the Arabian Sea (Gulf of Aden) and the Indian Ocean. The island's area of 3600 km 2 is covered by a very diverse vegetation (Miller et al. 2004;Kürschner et al. 2006;De Sanctis et al. 2013;Habrová and Buček 2013) corresponding to an arid tropical climate (Culek et al. 2006;Scholte and De Geest 2010). The vegetation of Socotra Island is composed of more than 850 plant species, of which 37% are endemic (Miller et al. 2004;Kilian and Hein 2006;Brown and Mies 2012;Řepka et al. 2017). ...
This article presents the methodological approach of age estimation of juvenile Socotra dragon’s blood trees (Dracaena cinnabari Balf. F., DBT) for the first time. To date, only the model for the age estimation of the tree crown after the first flowering event has been published. The DBTs were measured on Socotra Island (Yemen), on the Firmihin Plateau. A set of three indirect growth models was used for the estimation of the juvenile phase duration. The first model shows the relationship between the proportion of stem cavities and diameter at breast height (DBH). The second model describes the relationship between the DBH and stem height of juvenile trees. The third model expresses the radial stem increment with an increasing number of branch orders. The first model estimates the ratio of the stem cavity and secondary vascular tissue. The second model serves to retrospectively estimate the DBH of the tree at the time of the first flowering event according to the height of the stem. Extrapolation of the third model enabled us to estimate the duration of the juvenile phase that corresponds to the thickness of the secondary vascular tissue. A non-destructive methodology for juvenile DBT age estimation was developed, although the calculated absolute values are not precise. The same approach can also be used for the other arborescent dragon tree species. The validity of our assumption should be verified by repeated measurements on trees from different age groups. And thus, more precise model with less uncertainty about the parameter estimates could be obtained in the future.
... The montane and high-montane vegetation with D. cinnabari is found on limestone foothills and granite peaks above 700 m a.s.l., where the temperature drops during the late afternoon and evening leads to the regular formation of clouds. The interception of horizontal precipitation from clouds and monsoon mist together with dewfall substantially enhance the available moisture leading to the formation of lush vegetation where dragon trees grow as scattered emergents overlooking a dense species-rich shrub layer [194][195][196]. The findings by Rejžek et al. [28] indicate that D. cinnabari acts as an ecosystem engineer, i.e., a key species that alters the abiotic environment, controls the availability of resources, and facilitates the growth of other species. ...
This article is a broad review focused on dragon trees—one of the most famous groups of trees in the world, well known from ancient times. These tertiary relicts are severely endangered in most of the area where they grow. The characteristic features of the dragon tree group are described and the species belonging to this group are listed. This review gathers together current knowledge regarding the taxonomy, evolution, anatomy and morphology, physiology, and ontogeny of arborescent dragon tree species. Attention is also paid to the composition, harvesting, medicinal, and ethnobotanical use of the resin (dragons’ blood). An evaluation of population structure, distribution, ecology, threats, and nature conservation forms the final part of the review. In the conclusions we recommend further avenues of research that will be needed to effectively protect all dragon tree species.
... Most authors have described the vegetation of Socotra Island in the context of altitudinal vegetation zones (Kürschner et al., 2006;Král and Pavliš, 2006;Brown and Mies, 2012;Malatesta et al., 2013;Habrová, 2004;Habrová and Bu cek, 2013) using a combination of field observations and remote sensed data (Table 1). Brief description of the vegetation in Socotra Island according to altitudinal zones. ...
The Socotra Archipelago contains islands of high conservation importance. Since 2003, the Socotra Archipelago is a UNESCO Man and Biosphere Reserve and since 2008 it was officially listed as a UNESCO Natural World Heritage Site. In addition, the Socotra Archipelago contains currently the only Ramsar Site of Yemen (Detwah Lagoon), and it has been declared as one of 200 WWF Global Ecoregions for its unique terrestrial ecosystems (xeric shrublands), the status indicated as critical/endangered by WWF. Even the freshwater ecosystems that harbor several endemics have been given a special status, as Socotra is recognized as one of the globally outstanding Freshwater Ecoregions of the World. Socotra is also part of the Horn of Africa Biodiversity Hotspot as recognized by Conservation International, and listed as a Centre of Plant Diversity by Plantlife International, ranked among the richest yet most threatened biodiversity areas on the Planet. The Archipelago was declared as its own Ecologically or Biologically Significant Marine Area (EBSA) at the Convention of Biological Diversity (CBD) meeting in 2016, and the same year as an Endemic Bird Area by BirdLife International, which listed several Important Bird Areas (IBAs) for the Archipelago. A number of endemic plants and vertebrates from Socotra have been included in the IUCN Red List, but updates are needed and very few of the many endemic invertebrates have been listed. However, the biodiversity of Socotra is increasingly affected by impacts that affect ecosystems globally, such as unsustainable resource use and global warming which are now visible in the islands. We discuss the main threats and list some general conservation needs in the Socotra Archipelago.
