Shei-Pa National Park's complex terrain is home to a wide range of plant species. Surveys have shown that 1,976 species of vascular plant grow within the park, 183 of them rare or very rare. The range of altitude in the park is from 760 meters above sea level in the valley of the Da-an River to 3,886 meters at the summit of Xue Mountain. The differences in altitude and temperature cause a diversity of microclimates, which range through warm-temperate, temperate and cool-temperate to cold-temperate and subarctic. As a result, there are many different types of forest cover, falling into the zones described briefly below:

Caudate-leaved Chinkapin ( Castanopsis carlesii)

Chinese Cork Oak ( Quercus variabilis)

This zone in Taiwan occurs at altitudes between 500 and 1,500 meters, where the climate is warm-temperate. The forest is of montane evergreen broad-leaved type, trees of Fagaceae family with Castanopsis species dominant. In the lower layer of trees Machilus species, of the Lauraceae family, are dominant.

Quercus Zone

This zone is found at altitudes from 1,500 to 2,500 meters, climate equivalent to that of temperate regions, with montane coniferous forest. Two subzones can be distinguished: the Quercus upper zone at 2,000 meters to 2,500 meters, the Quercus lower zone, below 2,000 meters. In the upper zone, the forest type is mixed coniferous broad-leaved, the trees belong to the Fagaceae family with Arishan Oak ( Cyclobalanopsis stenophylloides) dominant. In the Quercus lower zone, the principal species are Cyclobalanopsis spp. and Pasania spp. of the Fagaceae family, and Litsea spp. of the Lauraceae family. The Quercus zone is just at the level of the cloud and mist belt on the Taiwan mountains; because of this a type of forest cover occurs in which Taiwan Red Cypress ( Chamaecyparis formosensis) is dominant, or the cypress grows in community with various other trees, coniferous and broad-leaved, forming mixed coniferous forest. In areas where landslides or forest fires have disturbed the original tree cover a kind of forest may be seen in which Taiwan Red Pine ( Pinus taiwanensis) and Formosan Alder ( Alnus formosana) are the principal species.

Taiwan Red Cypress ( Chamaecyparis formosensis)

The name refers to mountain areas between 2,500 meters and 3,100 meters in height, where the climate is similar to that of cool-temperate regions, producing montane coniferous forest. In this zone Chinese Hemlock ( Tsuga chinensis) and Taiwan Spruce ( Picea morrisonicola) are the principal dominant species: the Tsuga is usually found on the south-facing slopes or along their crest, while the Picea prefers the damp and shady northern slopes and the valleys of creeks flowing southwards.

Common Machilus ( Machilus thunbergii)

The fruit of Arishan Oak ( Cyclobalanopsis stenophylloides)

The name refers to mountain areas between 3,100 meters and 3,600 meters high, with the climate of cold-temperate regions, and vegetation of sub-alpine coniferous forest type. The forest in this zone is frequently a pure stand of Taiwan Fir, or called Kawakami Fir ( Abies kawakami), which in Taiwan is a tree species of the forest line. The famous black forest of Xue Mountain is a pure Abies community, and the silver forest behind Sanlioujiou Cabin (369 Cabin) is the unusual scene left after an Abies forest was burned in a forest fire.

In this forest zone, there is another important tree species: Yushan Juniper ( Juniperus squamata). This Juniper can be found at higher altitudes than any other tree in Taiwan and is a timberline species. When it is growing in places exposed to the wind, the wind pressure causes it to develop as a thicket of dwarf shrubs, as in the Syueshan Glacial Cirques; but in places sheltered from the wind it can become a large tree, for instance at Cuei Pond near Xue Mountain, or in the area below the Main Peak of Xue Mountain. The Juniper forest at Cuei Pond is particularly impressive: beautiful old trees reaching up into the heavens.

The Alpine krummholz in autumn forms a picturesque scenery in high mountains.

Alpine Vegetation Zone

This means the zone above 3,600 meters, where the climate is that of subarctic regions, and the plants are those of an alpine vegetation zone. The vegetation is above the forest line; the wind is strong; the soil is thin; the scree is barren; moreover in winter the ground is covered with snow. A special effect of the wind's action is that the fragments of stone form scree slopes or level patches of scree. It is very difficult for plants to grow here; herb species survive best, and many form an Alpine herbs vegetation community.

In the lower sections of this zone, where the Alpine herbs community meets the forest line, geographical and climatic factors cause the trees to grow along the ground or in shrub form, forming Alpine Krummholz community. The principal members of this community are Yushan Juniper and Alpine Rhododendron.

Visitors to Shei-Pa National Park from some other countries may well be impressed and happy when they learn that within the park there is very little man-made woodland: all types of forest mentioned above are the natural pristine plant cover.

Taiwan Fir ( Abies kawakamii)

The flower of Taiwan Sassafras.

Plants found in Shei-Pa National Park that have points of particular interest include:

* Taiwan Sassafras ( Sassafras randaiense): only three members of this genus still exist on the planet. The Taiwan Sassafras is unique to this island; the other two are distributed over North America and Mainland China. The sassafras has been around on the planet since the Pliocene epoch of the Tertiary period (between 1.8 million and 2 million years ago), and its distribution has been used by scientists to study the movement of continental plates. The timber of this tree has a beautiful grain and in Taiwan has been much sought after for the making of furniture. Excessive logging has brought the species to the edge of extinction, and this in turn has depleted the food supply of larvae of the Broad-tailed Swallowtail Butterfly ( Agehana maraho). This rare butterfly is unique to Taiwan, and its larvae eat only the leaves of the Taiwan Sassafras. There are still forests of Taiwan Sassafras within Shei-Pa National Park, and in conserving this now rare tree, the park is also preventing a scarce and beautiful butterfly from becoming extinct.

* Syueshan Potentilla ( Potentilla tugitakensis) is a rare alpine found in small numbers with restricted distribution at altitudes over 3,500 meters in the Nanhu Mountain, Xue Mountain and Dabajian Mountain areas.

* Devol's Balsamine ( Impatiens devolii), which grows in the park close to Guanwu, is found nowhere else in the world . The plant is found in small numbers in only a small area. If not carefully protected, it is likely to go extinct.

The main reasons why a species may be rare are: a restricted habitat, poor inherent adaptability, destruction of ecosystems or habitats, and excessive hunting or felling by humans. Habitat destruction is often caused by man, and thus human activity is a major reason for species' becoming rare. The loss of a species from an ecosystem does not simply mean its destruction alone, but sets off a whole chain reaction. The park is a treasure house of genetic material. Therefore, we must take care of our biological resources, for when we are protecting rare species, we are also protecting the future of the human race.