Conservation efforts against the threats to native orchid’s species in China

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The Coelogyne nitida, native to China
The Bletilla striata (Chinese ground orchid)

The following will explore and explain the threats that native Orchid species within China face, and the various both successful and failed attempts at their conservation that have taken place in China, with emphasis on in the past two decades.

Introduction to Orchids

Orchid's in China

IUCN Red List Categories
Orchid adorned folding fan

Orchids, a group of plants in the family Orchidaceae, are a diverse taxa with thousands of species that originate from Asia [1]. They are among the largest families of flowering plants, with approximately 750 genera and 28,000 species worldwide. There are 1708 known species in 181 genera in China, including five new genera and 365 new species described over the last 21 years [2].

This rich diversity of species is valued in conservation, however, challenges in their conservation arise due to complex life history traits for reproduction and symbiotic relationships with fungi for germination [1]. They depend on mycorrhizal fungi for germination and some require trees or stone to grow on. Orchids unique requirement for life, and their history of being harvested for aesthetic value or medicinal use pose challenges for conservation. Orchids have a culturally rich history within China, with their cultivation beginning in the late Tang Dynasty [2]. Certain species have been used for medicinal purposes for 2000 years [2]. The demand on orchid species with high Chinese medicinal values (Gastrodia elata, Dendrobium offcinale) along with demands on species of cultural importance, (genus Cymbidium) are. factors contributing to wild populations diminishing [3].

Status of Orchids

China uses many ranking systems including the IUCN Red List and other rankings to denote at risk species. One of China's rankings, Plants Species with Extremely Small Populations (PSESP), has been used to described some orchid species. Some PSESP in the Yunnan and Hainan provinces have very little to no protection. The PSESP are different from naturally rare species as the small populations are due to recent declines from anthropocentric change [4].

Besides PSESP classification, the 2013 assessment of risk of extinction for known native orchid species in China indicated:

  1. 653 species were threatened
  2. 132 did not have enough data
  3. Four were classified as extinct [2]

Threats to Orchids

Approximately 90% of the 653 threatened species have been affected by habitat loss, deterioration, and/or fragmentation. Surveys have also suggested and concluded that the trade of wild-harvested orchids is very active in China [2].

Habitat Loss

Habitat loss is one of the biggest threats to orchid species due the specific conditions needed for survival. Orchids are sensitive to any changes in their habitat and therefore land use change poses a big threat to the conservation of orchids [4].

Industrial projects, like China’s largest hydropower project, cause the displacement and removal of orchids. Further, the value of orchids results in many being collected and translocated, or sold. At completion of the hydropower plant, 1000 orchid plants including 29 species and 16 genera were translocated [5].

Habitat Fragmentation

Habitat fragmentation due to increased urbanization is also a threat. Orchids have sensitive life histories and when disrupted due to separation in a viable habitat, they may not be able to reproduce or have access to the fungal associations needed for their life histories. Habitat is often the most vital factor in the restoration of at risk species and orchids are no different [4].

Over Picking

Orchids are a valuable ornamental piece, and therefore are profitable when traded [4]. They make up 85% of the planned banned for trade by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).[6] CITES is a piece of international legislation that aims to stop the trade of endangered and threatened species. This policy is important to the protection of orchid species, given the high number of orchids it makes illegal to trade [7].

Many businesses source their orchids from the wild as opposed to privately grown or conserved plants due to the costs. This is an unregulated practice and has allowed for a steep decline in wild populations [5].

Dendrobium devonianum is a species of orchid widely used in Southeast Asia for its medicinal benefits. It's stem has high levels of polysaccharides and dendrobine, providing anti inflammatory effects, digestive benefits, and ability to reduce blood sugar. This has led to mass picking and a grossly reduced natural population [6].

Climate Change

Climate change poses a huge threat to biodiversity globally. It's consequences can be seen in orchid populations in the Guangxi province of China. Orchids require certain climate conditions and the threat of global warming will certainly challenge these needs as it has caused a temperature increase of 0.5°C with projected temperatures continuing to rise. Impacts on precipitation will also cause stress to orchids as a predicted fall in soil moisture conditions will support less growth. These factors combined with the fact that many orchids require habitat on the tops of mountains, where conditions are likely to be changed, leave orchids with no where to go [8].

Conservation Efforts

Conservation Translocation

Conservation translocation refers to the assisted migration of a species to a new range to avoid threats from climate change or habitat loss. This method differs from reintroduction programs because it uses a new range of habitat rather than reintroducing seeds to the same historical ranges. Translocation can be more effective than reintroduction programs, with a survival rate of 80% versus 40% in one study. This is a promising method in the orchid conservation [4].

In another example, relocation placed more than half of the species out of their natural elevation range which allowed researchers to test assisted colonization. Most orchids subject to translocation were able to newly connect with root and mycorrhizal fungi. Certain species thrive in certain conditions and some require specific conditions to survive so proper location selection is integral to this methods success. Monitoring the survival of the plants allows researchers to establish appropriate location and methodologies for this new method [5].

Reintroduction Programs

Reintroduction programs, which grow species outside their natural environment and the integrate them back into the wild, offer promise in orchid conservation. One study found a survivorship of 60% in the second year of reintroduction. However, without the establishment of the symbiotic fungi, some species cannot germinate their seeds and thus cannot reproduce [4]. Reintroductions programs aim to relieve pressure from the most threatened species by reestablishing them in the wild using seeds germinated in more controlled climates [6].

Epiphytic Orchid (Bulbophyllum pulchellum)

By tending to the orchids complex life style and cycle, reintroduction programs aim to foster successful growth. Orchids critically rely on certain fungi to promote seed germination, so encountering these fungi directly correlates with increased orchid population growth and the success of reintroduction programs [6].

Different species of orchids require specific conditions for initial growth. Terrestrial orchids are able to thrive in laboratory like conditions unlike Epiphytic orchids. Adapting to live on the bark or rocks instead of soil complicates laboratory growth for epiphytic orchids, and transportation is often unsuccessful as the habitat switch is not straightforward. Reintroduction programs analyze the challenges of each species and introduce trials to mitigate their impacts [6].

A case study on Paphioepdilum spicerianum, a species with extremely small populations in the wild, has shown some success with reintroduction programs with a survival rate of 40%. As P. spicerianum preferentially grow on banks near streams, there is very limited habitat that can be used for reintroduction [4].

Although there are promising outcomes, reviews of these programs revealed a low success rates in the long term because of the orchids overall ability to survive. Reintroduced plants have significantly lower flowering and fruit rates, making programs assistance crucial [6]

Ex-Situ Conservation

Ex-situ conservation is a technique of conserving species outside of their natural habitats. It was officially adopted under the Convention on Biological Diversity signed in 1992 as a method of conservation. Examples of ex-situ conservation efforts are, zoological gardens or parks, botanical gardens, gene banks [9]. Ex-situ collections are also important to serve as a basis for reintroduction programs. Ex-situ conservation techniques should be viewed as a compliment to effective in-situ programs and other conservation measures but not a substitute. Conservation through reserves alone is unlikely to be able to protect and conserve all orchid species, but it nonetheless has an important role to play in orchid conservation [10].

Conservation using ex-situ methods in China has protected around 60% of vascular plant communities, of which orchids are a part of [4]. About 800 orchid species in China have living collections in major botanical gardens. They have become a major focus of conservation efforts at 20 public and academic botanical gardens. Five botanical gardens in South China are even well known for their work on ex situ orchid conservation, however, there is only one botanical garden in North China [2].

Orchids from South and East China, which are subtropical and tropical regions, are well protected in botanical gardens. There is a gap in the conservation of species in North China, the alpine and/or northern temperate regions. Among the 300 native orchid species in Northern China, only 50 species are included in living collections [2].

In-Situ Conservation

The dendrobium devonianum, native to southern China

In-situ conservation is defined as conservation in ecosystems and natural habitats, maintaining viable populations of species natural surroundings. This can be done in protected areas. It is concerned with the maintenance of diversity that is available in various ecological sites. In-situ conservation has certain limitations, for example, some the natural habitats or wild habitats are very risky when compared to relatively safe captive environment [9].

National nature reserves in China are known for their rich orchid diversity, with 2750 national and provincial reserves established across China in 2018. In-situ conservation in China is more effective, with around 1100 (65%) of species are protected in national nature reserves, and another 66 species found in provincial nature reserves [2][4]. The most effective approach to in-situ conservation takes into account the life history traits of orchids and roles of mycorrhizal fungi and pollinators [2].

In efforts to increase epiphytic seedings potential growth in the seedling stage, researchers developed a novel seed sowing technique [6]. Specifically for epiphytic orchids, the seedlings and required fungi are simultaneously sown on the tree bark [11]. This method of introducing epiphytic orchids ensures their access to fungi to increase the rate of successful germination

This methodology was first put in practice with the Dendrobium devonianum orchid. The increased use of this flower as medicine and a nutraceutical food in China resulted in a rapid decrease in the population. The fungi needed for growth requires specific placement directly connected to the orchid seed and the substrate. The fungi's mycelium is mixed with agar powder where the orchid seeds are placed. This mixture was immersed in water to retain moisture and placed throughout the ecosystem. The initial study was conducted in the Yunnan Province, and researchers successfully attached 182 seed packets to tree trucks and monitored their germination over 3 months. Results showed that 80% of packets produced seedlings with the actual germinated varying from 0-36%. After 6 years plants began to flower and produce fruits, indicating the entire life cycle had completed and the method was successful [6].

Conservation Case Study: Dendrobium aphyllum

This is the first study to report on cultivable mycorrhizal fungi extracted from germinated protocorms of D. aphyllum.

Xishuangbanna Tropical Botanical Gardens

The research was conducted at the Xishuangbanna tropical botanical gardens in Yunnan, China, where the Dendrobium aphyllum orchid are classified as endangered. This epiphytic orchid is heavily collected for medicinal and floricultural use and their primary habitat in Yunnan was rapidly converted to monoculture rubber plantations. The species requires precise conditions for growth and faces significant challenges and has been classified as endangered according to the Chinese Red List [12].

In order to preserve the genetic diversity of reintroduced orchids, seeds are the preferred method of growth for rare and endangered species. In the beginning stages of growth, seed germination and development require the support of fungi to thrive as fungi provides resources and nutrients directly [12].

The factors were accounted for in the study, as the fungi was germinated with the seeds directly, allowing the symbiotic relationship to be easily established. The relationship between fungi and orchids adapts greatly as the orchid moves through different life stages, making this tedious and difficult to get right. Other factors like environmental conditions and light exposure effect this relationship [12].

Methods

The Xishuangbanna tropical botanical gardens in Yunnan receive high levels of precipitation averaging 1,557 mm and reach an average high of 21.5°C and low of 7.5°C [12].

1. Seed Collection and Storage

Seeds were collected from plants in the in-situ conservation collection at the Xishuangbanna reserve [12].

2. Fungal Baiting

For the seeds, researchers used nylon packets with holes large enough for fungal hyphae to enter. The seeds were from seven different adult D. aphyllum populations, collected from various sites consisting of ex-situ and naturally growing plants. Seed packets were attached to moss covered bark which allowed protection from environmental conditions. Packets were later transported between sterilized wet moss back to the laboratory [12].

3. Isolation

The mycorrhizal fungi was isolated from the protocorms found in the seed baiting packets using the Zettler and Piskin method. The fungi was released when the protocorms were sterilized and broken open. After 5 days, the fungi was transferred again, and purified strains were then collected from the subcultured colonies and placed on Petri dishes [12].

4. Identification

The strains were then identified by their DNA. Purified strains were collected for a week in liquid PDA and seeds were then transferred to the fungi. Samples were randomly assigned a continuous dark treatment or a 12h dark and 12h light cycle. The samples were left for 39 days, and any samples containing alternate fungi strains were removed [12].

Findings

The dendrobium aphyllum, native to southern China

Research found the Tulasnella species supported germination and seedling development unlike Trichoderma which negatively impacted the process. The seeds were able to germinate with the absence of light, however, some species thrived in the dark while others thrived in the light. These findings partially supported the hypothesis that mycorrhizal fungi would enhance germination and seed development [12].

The orchid seed baiting technique was able to detect the required fungi and obtain endophytes to facilitate seed germination and protocorm development in native habitats. This method was more efficient than root-based fungal isolation in extracting seed–germination enhancing fungi [12].

Conservation programs need to maintain live cultures of the fungi being isolated and used for enhancement to allow for future testing on other species. Different fungi impact the development of the species differently and having the same strain for future tests is integral for efficient and successful conservation of Orchids [12].

Orchid Conservation Biology

Pollination

Orchid pollination is important for orchid conservation, especially in-situ. Some species require a functional group of pollinators while others require specific pollinators. Specialized pollinators for certain species of orchids include wasps, fruit flies, hoverflies, and dung flies, with the adian honey bee is the main pollinator of ten species. Pollinator attraction in 44 species relies on various deception mechanisms, such as general food deception, shelter imitation, and brood-site imitation [2].

Population genetics

A orchid populations genetic diversity is closely related to their strength, with low genetic diversity species having a potentially reduced chance of survival in changing environments. Understanding genetic diversity is crucial for understanding conservation strategies, as the major aims of conservation programs are to maintain genetic diversity within plant species. The good news is, most orchid species have a high genetic diversity and genetic differentiation among populations [2].

Mycorrhizal Fungi Importance and Dependency

Mycorrhizal fungi root tips

Mycorrhizal fungi play a crucial role in the orchid life cycle, distribution and abundance. Most terrestrial orchids depend either fully or partially these fungi for carbon and other resources. This fungi has been recognized as an important factor in determining an orchids ability to thrive or exist in a habitat. Many strains have been isolated and used for orchid seed germination or reintroduction [2].

Most orchids are photosynthetic at maturity and therefore their dependency on mycorrhizal fungi may be reduced once photosynthetic ability is gained. More than 100 species of orchid are achlor-ophyllous, meaning they are completely dependent on fungal partners [3]

To successfully conserve orchids like G. elata and restore orchid habitats, a pressing need arises to isolate, screen, and preserve compatible mycorrhizal fungi. Isolation of orchid mycorrhizal fungi is the first step in its applications for orchid commercial propagation and orchid conservation.[3]

For commercial production and conservation it's important to screen the compatible mycorrhizal fungi. It should have at least one of the following:

  1. Capable of stimulating seed germination
  2. Improving the growth of protocorms, young seedlings or juvenile plants
  3. Improving the growth and reproduction of adult plants. [3]

Conclusion

Orchid conservation has improved and many achievements have been made in China over the last few decades. Thanks to international legislation from CITES and monitoring from the IUCN, orchids are being looked after from others. Many orchids in China have been protected, rehabilitated, recovered or rescued through in-situ or ex-situ efforts. 50 endangered plant species are expected to be further rescued by these same measures between 2021 and 2025, including five orchid species. To effectively conserve orchids moving forward we need to understand the biology of each species, including pollination biology, mycorrhizal fungal associations, life cycles, and population dynamics [2].

Although the future of orchid status is somewhat unknown, there is hope for the promising conservation strategies that have allowed for orchids to become a center of national debate. The rich biodiversity of orchids needs to be preserved both in herbariums and in the conservation efforts that will hopefully restore historical habitats. There is also a hope for the focus on biodiversity hotspots in China, where species which all rely on the same geographic area may be saved from the threats of habitat loss and over picking [13].

There is future areas of study about orchids, such as pollination and inbreeding depressions. With a biodiversity crisis on our hands it is vital that we remain aware of the importance of each species and preserve the health of orchids so that they only remnants of them in the next 10 years are not pressed samples in a herbarium [13].

References

  1. ↑ 1.0 1.1 Lui, Hong; Liu, Zhongjian; Jin, Xiaohua; Gao, Jiangyun; Chen, Yan; Liu, Qiang; Zhang, Di-Yang (March 2020). "Assessing conservation efforts against threats to wild orchids in China". Biological Conservation. 243 – via Elsevier Science Direct.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 Zhou, Zhihua; Shi, Ronghong; Zhang, Yu; Xing, Xiaoke; Jin, Xiaohua (22 June 2021). "Orchid conservation in China from 2000 to 2020: Achievements and perspectives". Plant Diversity. 43(5): 343–349.
  3. ↑ 3.0 3.1 3.2 3.3 Liu (2010). "Studies of mycorrhizal fungi of chinese orchids and their role in orchid conservation in china - A review". The Botanical Review. 76(2): 241–262.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 Ren, Hai (2020). Conservation and Reintroduction of Rare and Endangered Plants in China. Singapore: Springer. pp. 1–233. ISBN 9789811553011.
  5. ↑ 5.0 5.1 5.2 Liu, Hong; Gao, Jiangyun (29 August 2020). "Orchid Conservation Translocation Efforts in China". Conservation and Reintroduction of Rare and Endangered Plants in China: 205–224.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Shao, Shi-Cheng; Luo, Yang (04 December 2021). "Successful reintroduction releases pressure on China's orchid species". Trends in Plant Science. 27(3): 211–213. Check date values in: |date= (help)
  7. ↑ Hinsley, Amy; Nuno Ana; Ridout, Martin; St. John, Freya A. V.; Roberts, David L (November 2016). "Estimating the Extent of CITES Noncompliance among Traders and End-Consumers; Lessons from the Global Orchid Trade". Conservation Letters. 10: 602–609 – via Society for Conservation Biology.CS1 maint: multiple names: authors list (link)
  8. ↑ Liu, Hong; Feng, Chang-Lin; Luo, Yi-Bo; Chen, Bao-Shan; Wang, Zhong-Sheng; Gu, Hong-Ya (March 2010). "Potential challenges of climate change to orchid conservation in a wild orchid hotspot in Southwest China". The Botanical Review. 76: 174–192 – via Springer Link.CS1 maint: multiple names: authors list (link)
  9. ↑ 9.0 9.1 Kasso, Mohammed; Balakrishnan, Mundanthra (21 November 2013). "Ex Situ Conservation of Biodiversity with Particular Emphasis to Ethiopia". International Scholarly Research Notices. 2013.
  10. ↑ Seaton, Philip; Hu, Hong; Perner, Holger; Pritchard, Hugh (31 March 2010). "Ex Situ Conservation of Orchids in a Warming World". The Botanical Review. 76: 193–203.
  11. ↑ Shi-Bao, Zhang; Chen, Wen-Yun; Huang, Jia-Lin; Bi, Ying-Feng; Yang, Xue-Fei (10 November 2015). "Orchid Species Richness along Elevational and Environmental Gradients in Yunnan, China". PLOS One. 10(11).
  12. ↑ 12.00 12.01 12.02 12.03 12.04 12.05 12.06 12.07 12.08 12.09 12.10 Zi, Xiao-Meng; Sheng, Chun-Ling; Goodale, Uromi Manage; Shao, Shi-Cheng; Gao, Jiang-Yun (October 2014). "In situ seed baiting to isolate germination-enhancing fungi for an epiphytic orchid, Dendrobium aphyllum (Orchidaceae)". Mycorrhiza. 24(7): 487–499.
  13. ↑ 13.0 13.1 Seaton, Philip; Kendon, Jonathon P.; Pritchard, Hugh W.; Puspitaningtyas, Dwi Murti;, Marks, Tim R. (2013). "Orchid conservation: The next ten years". Lankesteriana. 13: 93–101.CS1 maint: multiple names: authors list (link)


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