Pterocarya & Juglandaceae

Since 2015 an extension of the Project Zelkova has been elaborated in order to explore and protect other genera and families of relict trees. The main focus is put on the genus Pterocarya and on the family Juglandaceae. The genus Pterocarya has six extant species with similar disjunctions as in Zelkova. Many highly isolated populations, especially for Pterocarya fraxinifolia, are very threatened and have been never collected and/or investigated.

Leading researchers: Sébastien Bétrisey and Yi-Gang Song

The project

The project Pterocarya comprises four main objectives: (1) Ex situ conservation of Pterocarya fraxinifolia and other relict trees of the Transcaucasia. (2) In situ conservation of Pterocarya fraxinifolia with pilot restoration sites in Georgia. (3) Phylogeographic analyses of the genus Pterocarya covering the whole distribution area of Pterocarya fraxinifolia and of the whole genus Pterocarya. (4) Production of a richly illustrated and detailed booklet on the conservation status and actions needed for the whole genus Pterocarya as well as on the diversity and importance of the whole Juglandaceae family. This part, including exchange and field work in Europe, Asia and America, will be carried out by the Zelkova team of the University of Fribourg in Switzerland.

The island of Cuba: a jewel of biodiversity

In October 2017, an expedition was carried out, in order to document both subspecies of Juglans jamaicensis, two of the most endangered and extraordinary members of the Juglandaceae family. While J. jamaicensis subsp. jamaicensis is still present in the Dominican Republic (more than twenty population) and in the center and east of Cuba, the species has almost completely disappeared from Puerto Rico (only one small population left known) and is under high pressure in Haiti, due to intense deforestation. The range of J. jamaicensis subsp. insularis is much smaller, the species is endemic to Cuba. It grows most exclusively in the western province Pinar del Rio. The two taxa usually come as isolated individuals or very small populations in semi-deciduous montane forest. The species often grow near streams or at the border between forested hills and cultivated lowland areas, involving high pressure from agriculture. Logging and ranching have also decreased the extension of their habitat.

With the help of local guides and forest specialists, we discovered an astonishing biodiversity and some small populations of J. jamaicensis in Viñales National Park in the west, and in the Escambray Mountains in the center of the island. Juglans jamaicensis is very scattered and needs urgent conservation action programs both in situ and ex situ.

Pterocarya forests in Xiaolong Mountain (China)

Exploring China’s unique tree diversity

Xiaolong Mountain National Nature Reserve is located in the western part of the Qinling Mountains (Gansu province in Central China). In August 2017, an expedition took place, in order to explore the Pterocarya forests of this area. It was organized and coordinated by Yi-Gang Song, our PhD student at the University of Fribourg and at the Shanghai Chenshan Botanical Garden. The Xiaolong National Nature Reserve, characterized by the transitional climate between the warm temperate and subtropical conditions, possess a very high biodiversity and stunning variety of natural habitats. Vast virgin forests with large pure Pterocarya hupehensis stands, have been found and studied during the expedition. Additionally, two further Pterocarya species (P. macroptera and P. stenoptera) have been observed in this area, mainly along rivers. Further interesting trees, co-occurring with Pterocarya, are Juglans mandshurica, Quercus dolicholepis, Q. spinosa, Zelkova sinica and Z. schneideriana.


One of the main diversity centers of Juglandaceae

In April 2017 our Zelkova-team organized a scientific expedition to Vietnam in order to explore and collect iconographic material of Juglandaceae of this fascinating country as well as to officially sign the Memorandum of Understanding (MoU) between the University of Fribourg (Switzerland) and the Vietnam National University of Forestry (VNUF). The ceremony took place on 11th of April 2017 in Hanoi and was accompanied by a meeting with the president of VNUF Prof. Tran Van Chu, Prof. Hoàng Văn Sâm (Director of International Cooperation Division at VNUF) and Prof. Gregor Kozlowski on behalf of the University of Fribourg.

Vietnam is one of the main centers of species and genera diversity of this relict tree family, with minimum 10 species representing 6 genera: Rhoiptelea chiliantha, Alfaropsis roxburghiana, Platycarya strobilacea, Engelhardia (2 spp.), Pterocarya (2 spp.) and Carya (3 spp.). Three regions were explored: Ba Vi National Park, Cuc Phuong National Park as well as Con Dao National Park.

We would like to thank our partners at the Vietnam National University of Forestry (VNUF) in Hanoi as well as all field guides and research assistants for their help in finding populations in topographically very difficult terrain. Special thanks go to Prof. Hoàng Văn Sâm and Pham Thanh Ha (VNUF) as well as the direction of the Con Dao National Park.


The United States: a hotspot of diversity for relict trees

A high diversity of Carya species across the East Coast

The genus Carya is quite common in temperate forests of the northeastern United States and also in the vicinity of swamp forests throughout the southeastern states. Our journey began in South Carolina, with the exploration of the Congaree National Park, one of the most important old growth bottomland hardwood forests still existing in the country. These complex ecosystems are seasonally flooded and represent a unique habitat for singular trees such as the bald cypress (Taxodium distichum) and the water tupelo (Nyssa aquatica). Our goal was to take pictures and gain knowledge and information on natural stands of water hickory (Carya aquatica) and nutmeg hickory (Carya myristiciformis), which are often present in less flooded parts of this type of forest.

For the second part of our expedition, we benefited from close partnerships with the Arnold Arboretum of the Harvard University, which holds probably the most comprehensive ex-situ collection of the genus Carya in the world. Thanks to the help of Michael S. Dosmann, curator of the living collections, we were able to visit and document a part of this extraordinary collection. We then visited some natural stands of Carya (C. ovata, C. glabra and C. cordiformis) in the Blue Hills Reservation with the help of Irina Kadis and Kathryn Richardson from the Arnold Arboretum, who organized our expedition.

Royal Botanic Garden Edinburgh – the paradise of Pterocarya researchers

Understanding the ecology of a species requires expeditions to its country of origin and visiting its wild populations. However, field explorations are often cost- and time-consuming, especially when lacking a solid background on the species that we want to study. The Royal Botanic Garden in Edinburgh offers a unique alternative and allows studying different species of the genus Pterocarya found in its ex-situ collections. In 2016 we have visited the garden twice and been able to observe the most important criteria of differentiation between the species (especially terminal buds, leaflet and nuts) and bring back numerous pictures and knowledge, which will be very helpful for future expeditions in wild populations of Pterocarya in Asia. We would like to thank warmly Peter Brownless of the Royal Botanic Garden of Edinburgh for his precious help and advice.

Juglandaceae of Neotropis: Alfaroa and Oreomunnea

In April 2016 our Zelkova-team organized a scientific expedition to Costa Rica in order to explore and collect iconographic material of poorly documented Juglandaceae of Neotropis. Costa Rica is a center of species diversity for two genera of this family: Alfaroa (minimum 4 species) and Oreomunnea (2 species). They are typical elements of mountain forests and are growing often together with some other trees belonging to temperate families and genera (e.g., Quercus, Alnus, etc.).

We would like to thank all field guides and research assistance for their help in finding populations in topographically very difficult terrain. Special thanks go to Bryan Finegan, Leonel Coto and Diego Delgado (CATIE, Turrialba) for finding Alfaroa manningii and Oreomunnea mexicana as well as to Erick Viquez for A. williamsii and A. costaricensis.

Workshop "Relict trees in peril"

Between the 4th and 7th of July 2016 a workshop entitled “Relict trees in peril: conservation challenges and research projects across Eurasia” organized by our Zelkova-team took place in Tbilisi, Georgia (in collaboration with the Ilia State University, National Botanic Garden of Georgia and Batumi Shota Rustaveli State University). Invited speakers from Switzerland, Italy, Poland, Iran, Azerbaijan, China, Vietnam and Japan as well as Georgian scientists presented their research projects and conservation actions carried out in different countries and regions from the Mediterranean to Eastern Asia. The symposium was followed by a scientific expedition to Western Georgia in order to visit natural populations of Zelkova carpinifolia and Pterocarya fraxinifolia and to discuss with local stakeholders the long term conservation of the relict forests of the Colchis region. The participants visited the Ajameti Nature Reserve, one of the best preserved forest fragments dominated by Zelkova carpinifolia in the Colchis region as well as as the Kolkheti National Park with its riparian Pterocarya-forests, rivers, wetlands and mires.

Expedition to the Kolkheti National Park

The road that joins Eastern adn Western Georgia crosses rich historical cities and unique Monastery and links the Great Caucasus to the very touristic shore of the Black Sea. The Balck Sea coastal region hosts thousands of tourists and only few natural habitats have been preserved in this area. The establishment of the Kolkheti National Park in 1999 was a very strong and positive sign for the conservation of the last lowland forests and wetlands of the whole region. Izolda Matchutadze (Batumi Shota Rustaveli University) gave us the opportunity to explore the most remote areas of the Kolkheti National Park. The use of a small boat is necessary to follow the course of the rivers and reach pristine vegetation established in riparian corridors. Nowadays, Kolkheti National Park is facing many challenges, such as impact of intensive tourism, poor socio-economic conditions of local communities and invasive species. The variety of habitats included in the National Park (wetlands, forests, mires, sand dunes, etc.) and various economic interests make the long term conservation of the park very complex. A global management plan is currently under preparation. The conservation team of the University of Fribourg will participate in this great effort and is drawing up an ambitious conservation project of reforestation and restauration of degraded riparian habitats with Pterocarya fraxinifolia.

Establishment of a riparian forest protected area in Eastern Georgia.

One of the most remarkable stands of P. fraxinifolia in Eastern Georgia can be found in a vast and preserved floodplain near the small village of Lapankuri. The great dynamic of the Lopota river coming from the Great Caucasus allows the development of a singular riparian forest. In that particular area, P. fraxinifolia does not only grow along the main rivers and adjacent channels, but forms an original and vast forest spread deep into the land. This particular forest requires special protection status, in order to prevent further damages, especially plantation of maize and logging. We have also visited the magnificent Batsara-Babaneuri Protected Areas, home of the most important and preserved Zelkova carpinifolia forest for the Western Caucasus. The strict limitation of human activities within the perimeter of the Reserve is the only way to save relict flora vegetation and endemic fauna.

Exploring Cuc Phuong National Park, Vietnam
Collaboration with Niigata University in Japan