Euryodendron excelsum 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Theales Theaceae

Scientific Name: Euryodendron excelsum Hung T.Chang

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C1+2a(i,ii); D ver 3.1
Year Published: 2017
Date Assessed: 2017-07-18
Assessor(s): Barstow, M.
Reviewer(s): Shen, S.
Euryodendron excelsum is a large tree species endemic to the Bajia region of Guangdong Province, China. The species was previously also found in Guangxi province but is now considered to be extinct from here, showing historical population decline. Consequently the species has a remaining estimated extent of occurrence (EOO) of less than 25 km2 and an area of occupancy (AOO) of just 0.036 km2. Rigorous population surveys in 2009 suggested that there were only 23 mature individuals remaining out of a population of 176 individuals in total. However, in 2017 the population is now only thought to contain 6 mature individuals. This shows there has been a decrease in mature individuals of nearly 70% between 2009 and 2017. The species is considered to persist within one location due to its small geographic range and although we do not know the remaining number of subpopulations, the largest one will contain no more than 6 mature individuals. The remaining population occurs in a fragmented habitat divided by roads, villages and agricultural space. Anthropogenic activities have led to the decline in the species native habitat which has not only caused the loss of individual trees but has also reduced the reproductive potential of the species as conditions are becoming more unfavourable for germination and survival past the sapling stage. Therefore the species lacks regeneration potential for the future. Euryodendron excelsum is globally assessed as Critically Endangered. Seed collections have been made from remaining adult trees and some seedlings have been reintroduced to the Bajia region and different conservation sites to limited success.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is endemic to China. It was previously found in both the Guangdong and Guangxi province, however, after extensive surveys in the early 2000's the species was found to be extinct within Guangxi. The only extant population of this species now resides in the Bajia region, south west of Yanchun County in Guangdong provinces (Shen et al. 2009a). Within this site individuals were found at an average altitude of 160 m asl (Shen et al. 2009b). In 2009, the population is split into 10 subpopulations with overall estimated EOO not exceeding 25 km2 (Shen et al. 2009a). The species AOO is not thought to exceed 0.036 km2 (Shen et al. 2009a) to 16 km2 (GeoCAT analysis). Due to this the species is considered to persist within one location.
Countries occurrence:
China (Guangdong, Guangxi - Regionally Extinct)
Additional data:
Estimated area of occupancy (AOO) - km2:0.036-16Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:9.458-25
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:1
Lower elevation limit (metres):110
Upper elevation limit (metres):178
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The species is very rare, with a small remnant population. Within the Baija region the population is split between 10 subpopulations which are fragmented by roads, agricultural land and villages. Fragments can be separated by 0.22 to 9.47 km (Shen et al. 2009b). In Shen et al. (2009b), the population is reported to persist of only 179 individuals and included just 23 adult trees. This population was unevenly split with two subpopulations containing over 50 individuals, while the remaining eight contained fewer than 20 individuals each (Shen et al. 2009b). The average population density for the area was 50 trees/ha however it varied from 4 trees/ha, in the least dense patches to 123 trees/ha in the most densely populated patches (Shen et al. 2009b). In 2009, within the two largest patches there were good signs of regeneration as seedlings were present however seven patches were found not to contain seedlings. Most individuals were found in the two smallest size classes, only representing 0–100 cm in height. Shen et al. (2009b) discuss an environmental sieve where few saplings progress through the size classes due to a unfavourable growth conditions and by being out competed by surrounding faster growing species. In 2017, it was reported that the species was down to just 76 individuals of which only six were mature (Dandan 2017). It is not known how these mature individuals are dispersed across the described 2009 patches but it is assumed that all remaining subpopulations will contain six or fewer mature individuals. The species has experienced historical population decline as it has been lost from the province of Guangxi and is continuing to experience loss of mature individuals. Between 2009 and 2017 it is calculated that the number of mature individuals declined by 70% which is likely to be within one generation of the species. There is a lack of regeneration and the remaining population has low genetic diversity (BGCI 2017).

Between 2009 and 2017 the species has been subject to regeneration efforts. 2000 seedlings were propagated at Yunnan University and 300 of these were moved to the Bajia region with a 40% survival rate (Shen et al. 2013). The impact these efforts have had on population is unclear.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:6-23Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Yes
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:Euryodendron excelsum is a large perennial tree from 15 to 25 m high (Min et al. 2007). The species grows in forests on mountain slopes and valleys (Min et al. 2007). It is currently predominantly found in secondary and artificial forests (Shen et al. 2009b). The species is found in patches alongside Litsea sebifera, Cinnamomum camphora, Syzygium bullokii, Elaeocarpus sylvestris, Phoebe neurantha, Melia dubia, Schefflera insignis, and Cunninghamia lanceolata (Shen et al. 2009b). Seed is pollinated by birds however as there has been a decline in forest cover due to land conversion the number of birds present in the region is reducing and hence long distance seed dispersal is less common (BCGI 2017). The species flowers between September and November and fruits from October to February (Shen et al. 2009b). Seeds germinate best in shaded conditions in a high canopy forest (Shen et al. 2009a). This habitat type is now scarce and so germination and growth of seedlings has become limited. The species is considered to be slow growing (Shen et al. 2009a). Its remaining habitat is fragmented by agricultural expansion, road development and human settlements. It is subject to decline due to continued anthropogenic use of the forest and expansion of agricultural and settled areas into the forest.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):25-75

Use and Trade [top]

Use and Trade: This species is used for timber as it makes a good structural building material (Dandan 2017). The tree occurs within sacred groves.

Threats [top]

Major Threat(s): This species is threatened by anthropogenic activities. The development of infrastructure and the expansion of local villages and agriculture has caused the population to become fragmented. All remaining subpopulations of E. excelsum are now in close proximity to the villages, many of which still use the forest, maintaining the pressure on the species (Shen et al. 2009a,b). The species has a small remaining, reproductive population of between 7 and 23 mature individuals (Dandan 2017, Shen et al. 2009b). Many seedlings and sapling are not reaching maturity as they are out-competed by other species and the remaining habitat of the tree is not suitable to seed germination and early life growth (Shen et al. 2009a). This is a consequence of the reduction in canopy cover in forests due to anthropogenic activities. This change to the forest has also led to reduction in the availability of birds to disperse seed, reducing the species potential habitat range and the ability to outcross (Shen et al. 2009b). The species is also reported to have low genetic diversity (BGCI 2017) which increases the risk of inbreeding depression and reduce the adaptive potential of the species. The species is also potentially threatened by its use for timber but this requires confirmation.

Conservation Actions [top]

Conservation Actions: Following a seed collecting trip in 2009, this species has been propagated from seed at Yunnan University (Shen et al. 2013). Three hundred individuals were removed to Bajia and some were transplanted to Hekou county and Xishuangbana Botanical Garden. The survival rate varied from 40, 80 and 70% respectively (Shen et al. 2013). Adult trees found near to villages are often termed 'Sacred Groves' and are protected by the local villages (Shen et al. 2009b). Dandan (2017) reports the species is now found within the Yangchun Chuangzhang Nature Reserve which aims to protect the diverse and broadly endemic flora of the Bajia region. Partnerships between South China Botanic gardens, Yunnan University, local villages and the nature reserve are in place to try and conserve the remaining individuals and reintroduce the species. In China Euryodendron excelsum is listed as Critically Endangered (Ministry for Environmental Protection, China 2014). Conservation efforts should focus on the protection of the remaining habitat and mature individuals and assess the potential of reintroducing saplings to productive patches.

Citation: Barstow, M. 2017. Euryodendron excelsum. The IUCN Red List of Threatened Species 2017: e.T32348A2815634. . Downloaded on 18 December 2017.
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