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Ex situ Conservation of Wild Plants in Beijing Botanical Garden, China

Volume 2 Number 2 - July 1993
Zhang Zhiming

Abstract

The introduction and cultivation of wild plants from northern China have been given priority in the Beijing Botanical Garden ever since the establishment of the Garden in 1955. An all-round collection of wild plants from northern China, began in the late 1970s, with the emphasis on ex situ conservation of germplasm resources of rare and endangered plants and of ornamental and economic plants of wild origin. Of the some 5,000 taxa of plants grown at present in the Garden, 1,620 are wild plants that came from northern China. Meanwhile, a seed bank has been established, preserving wild plant seeds of over 700 species and more than 1,000 accessions. Research on seed storage at normal temperatures in ultra-dry condition is underway.

Introduction

The loss of germplasm resources of plants of the world is most serious in the tropical and subtropical regions. In temperate regions of China, a densely populated region with relatively insufficient resources, the damage caused to wild germplasm resources is equally alarming. In several former forest regions of north-east China, no timber trees are available any more, due to over-exploitation in the past. For example, in the Xiao Xinganling mountains, the renowned homeland of Pinus koraiensis, the amount of growing stock has reduced by 85%, from 240,000,000 cubic metres in the 1950s to the present 35,000,000 cubic metres. Destruction of the forest environment seriously threatens the survival of many plants. In the mountains and grasslands of north and north-west China, excessive reclamation of land and over-grazing of pastures have resulted in serious soil erosion and brought devastation to the natural vegetation.

Exchange of seed and plant material without due caution and control between different areas of China and with other countries has brought in some harmful plants which have, in certain places, not only invaded farmland, but also have been replacing the natural vegetation.

Developments in modern biological science and technology have enabled human beings to recombine genes according to their needs, and to create artificial species of so-called "engineered plants". With this in mind, all living plants in nature, including many seemingly useless herbs and trees, are really treasures that need to be protected and conserved. Each plant holds a large amount of genetic information, and one plant species may have over 400,000 genes. The extinction of a single plant species, therefore, means the loss of more than 400,000 genes formerly available for human use.

Some of the plants that have become extinct in the wild can still be found in botanic gardens. There is no doubt that ex situ conservation of wild plants in botanic gardens and in situ conservation in nature reserves are of complimentary importance.

Ex Situ Conservation of Wild Plants

The Beijing Botanical Garden is located in temperate zone with a continental climate of a hot summer with heavy rains and a cold and dry winter. It is suited to the growth of wild plants of north, north-east and north-west China origin. Since the foundation of the Garden in 1955, the introduction and cultivation of wild plants from the three northern regions has been given priority, with the emphasis put on economic plants, such as wild fruit trees and food and oil woody plants. In response to the request of the Botanical Garden Work Commission of the Chinese Academy of Sciences, that botanic gardens belonging to the Academy should highlight regional characteristics, the Beijing Botanical Garden formulated in 1979 a policy to concentrate its efforts on introducing and cultivating wild plants from the three northern regions.

Later, the emphasis has been given to rare or endangered plants, wild flowers and important economic plants of the regions. Each year, 2 or 3 expedition teams were sent out to investigate and collect wild plants. So far the following mountains have been explored: Yanshan, Taihang, Qinling, Xiaolong, Guanqin, Wutai, Funiu, Jigong, Da xinganling, Xiao xinganling, Tianshan and Altai. Among the some 5,000 taxa of plants grown in the Garden, 32.4% (1,620), have been collected directly from the wild.

(1) Rare and Endangered Plants

The special significance of the conservation of rare and endangered plants in China can be shown by the fact that over 200 genera and 1,200 species of plants are endemic to this country. These plants belong to China but are also part of the natural wealth of the whole human race. We regard it our duty to protect and conserve them. Stimulated by the world movement on plant conservation, our Garden set up a team engaged in the research project for ex situ conservation or rare and endangered species in 1985.

In 1989, the Botanical Garden Work Commission of the Chinese Academy of Sciences further specified that the conservation, utilization and study of wild plant germplasm resources of China, particularly those of rare and endangered plants, should be the major tasks of the botanic gardens belonging to the Academy. In the following years, extensive field investigations and collections were carried out by our staff in Tibai Mount of the Qinling mountains, the Xiaolong mountains of Tianshui, the Chanbai mountains in Jilin and the Taihang mountains in Henan, as well as other areas. Through these expeditions, 79 species endemic to the three northern regions were collected, amounting to 47% of the total 68 rare and endangered species of these regions. We studied their geographical distribution, ecological environment, biological characteristics and cultivation and propagation techniques.

The systematic study of Taihangia rupestris serves as a good example of this work. This species of the Rosaceae was first discovered in the Taihang mountains of Henan province and named by the late Professor T.T.Yu, taxonomist and the first director of the Beijing Botanical Garden. The genus to which this species belongs is monotypic, with a narrow, interrupted and scattered distribution and having only a limited number of plants left on cliffs. The plants do not set seed freely and thus the species is in danger of extinction. After several years work, the growth, development and propagation patterns of the species have been clarified; the factors threatening its survival have become known. We are now prepared to reintroduce plants back to their natural habitat.

(2) Wild Ornamental Plants

China is rich in native ornamental plants and has made a great contribution to the collection, introduction and cultivation of ornamentals from the mid-19th century until the beginning of this century. Large numbers of Chinese trees, shrubs and herbaceous plants with high ornamental value have been distributed and grown in botanic gardens, arboreta and many collections in foreign countries. Due to large area and the complex topography and climate of China, a large number of wild ornamental plants remain still hidden away in the depths of the forests and on the highland plateaus, places that are difficult for human exploration. In the three northern regions alone, there are, for example, 51 species of Rhododendron, 27 of Lilium, 83 of Rosa, 30 of Iris, 40 of Clematis yet to be explored and utilized. With this aim in mind, we made extensive introduction of plants in general and intensive introduction of certain families and genera in particular, with good results. At present, we have in our living collection 12 species of Clematis, 24 of Rosa, 13 of Lilium, 80 fern species, 40 of Begonia and 50 species of the Araceae. Seed germination testing, micropropagation, breeding for new varieties and other experiments and research have been carried out on many of these plant groups. Several hundred species, including Pulsatilla chinensis, Orychophragmus violcaus, Scabiosa tschiliensis, Lychnis fulgens, Androsace umbellata, Iris kaempferi, Liriope spicata, Oxytropis coerulea, Thalictrum contortum, Astilbe chinensis, and Lilium dauricum have been established well in our Garden. Over 50 species of ferns have been successfully propagated in vitro.

(3) Economic Plants

In general, few species of wild plants in China with obvious economic value have not yet utilized. The utilization of economic plants is closely associated with the social, economic, scientific and technological development, as well as with the raising of people's living standards. It is important to collect wild plants with potential economic value, or wild relatives and closely related species for the improvement of the quality of the corresponding cultivated plants. Obviously this should be based on the achievements of plant taxonomy, phytochemistry and other branches of botany. The range of our collection covers timber trees, fruit trees, oil-bearing plants, aromatic plants, plants for beverage, vitamins and for medicine. Of these, most abundant are medicinal plants, of which over 400 species amongst the nearly 500 species in our collection are of wild origin, and fruit plant resources, of which the important genera include Malus, Crataegus, Rubus, Vitis and Actinidia. All these plants represent important high quality material for the future development of agriculture, forestry and horticulture.

Seed Bank of Wild Plants

Plant germplasm resources can be effectively conserved only if the conservation of the species includes their full range of variation, including their ecotypes and phenological and geographical variants. However, the limited areas of most botanic gardens make it impossible to grow more than a few specimens of each of the wild plant species, let alone to include all their ecotypes and variants. The storage of seeds provides a convenient means for overcoming some of these problems and the long-term storage of plant genes. Furthermore, seed storage reduces the need for environmental requirements for example, specific soils, climate, living organisms and damage from human activities. Many more living seeds of plants of economic value or scientific significance can be kept in a seed bank, facilities which form an important part of ex situ conservation. At the Beijing Botanical Garden, when we collect living plants we also gather seeds. These are dried and sealed in aluminium foil packets and stored at an appropriate temperature. So far, seeds of about 700 species and 1,000 accessions have been collected and kept this way.

The IBPGR has determined that 8% moisture content and -10øC are the optimal storage conditions for the long-term storage of resources of cultivated varieties. Taking this as a standard, we reduce the moisture content of most seeds to around 5% and then put them in freezers with a temperature of -20øC for long-term storage. Some seeds can not be dried and kept at very low temperature without losing their vitality. These are sealed in packets immediately after being collected and stored at temperatures between 0-5øC. For small seeds, 50-100g. of each accession is usually put into storage. For medium-sized seeds 200-300g. and for large seeds 500-800g are stored. The number of seeds maintained of species with extra large seeds is never less than 300.

We are currently investigating the ultra-dry storage of seeds at normal temperature as part of a project sponsored by IBPGR (International Board for Plant Genetic Resources). The seeds have their moisture reduced to 1-3% and are stored at normal temperature for long periods without losing vitality. Marked progress has been made in this research on certain types of seeds.

Discussion

The Beijing Botanical Garden lies in the transitional area between the Yanshan Mountains in the north and the west, and the North China plain in the south and the east. It is favourable for the growth of numerous plant species and makes the Garden an ideal sites for ex situ conservation of wild plants from the three northern regions. However, due to its limited area, human and material resources, it is impossible to conserve in the Garden all the plant species that are suitable for growth there, or to maintain the required number of individual plants of each of those species that are conserved. Some experts suggest that the number of individuals required for the adequate conservation of a representative sample of a species is 10-20 for trees, 40-50 for shrubs and 100-200 for herbs. Accordingly, we have made our Garden's policy for ex situ conservation as follows:

  1. To collect and conserve selected rare and endangered species and economically important plant groups. Based on our work on wild fruit tree resources in the past decades, we have chosen the Rosaceae, which is composed of numerous temperate fruit plants and landscape and ornamental plants, as the family on which we concentrate our efforts in collection and conservation.
  2. To put more emphasis on the collection and conservation of shrubs, climbers and perennial herbs such as Rosa, Rubus, Spiraea, Cornus, Thymus, Ribes, Paeonia, Cotoneaster, Berberis, Vitis, Syringa, Lonicera, Weigela, Clematis, Iris, Lilium, Tulipa, Festuca and Poa. as these plants occupy relatively small areas and many of them can be accommodated in the shade of tall tress or form multilayered artificial vegetations incorporating various species of trees, shrubs and herbaceous plants.
  3. To collect and conserve different geographical or ecological races within species. The number of individuals of each race is usually not less than 5 (trees), 10 (shrubs) or 20 (herbs).

These guiding principles may seem, from scientific point of view, less effective in conserving the genetic diversity of plants but, in our opinion, are more realistic to follow in practice under our conditions, and are justified for following reasons.

  1. Although the current serious genetic erosion of wild plants demands urgent measures to be taken to conserve, both in situ and ex situ as many diverse plants as possible in as large areas as possible. It is simply impractical to conserve all the genes of every plant species. Even under natural conditions, plant species, populations and individuals are undergoing changes, under the pressure of environmental shifts. The plants that do not adapt will die out and the fittest can survive and gain a chance of evolving further.
  2. The limit to the number of plant species and quantity of individuals that can be practically conserved in any one area can be supplemented through the co-ordination of botanic gardens and their efforts situated in various climatic zones by forming co-operative conservation networks. Their joint efforts can ensure that the living materials in their collections are duplicated or made complementary, and nothing important is omitted.
  3. The establishment of seed bank of wild plants, as well as the conservation collection of other propagules such as spores, in vitro cells, tissues and plantlets have, to a certain degree, made up the quantitative insufficiency of living plants cultivated in the limited areas of botanic gardens.