台灣植物誌 第二版 Flora of Taiwan, 2nd edition Vol. 1
Introduction to the flora of Taiwan, 1:
geography, geology, climate, and soils
HSIEH Chang-Fu and SHEN Chung-Fu
(Including three figures on pages 4-A, 4-B, and 4-C, respectively.)
1. GEOGRAPHY AND GEOLOGY
The plants treated in the present flora are those growing naturally in the province of Taiwan, or the Taiwan region in other words. This geographic region is composed of Taiwan Islands, Penghu Islands, and Tiaoyutai Islands. The Taiwan Islands have 13 subsidiary islets. These islets are scattered offshore Taiwan in all directions but are absent in Taiwan Strait in the west, where the Penghu Islands stand. The Taiwan Island is about 130-200 km east of Fujien province on mainland China, and is about 360 km north of Luzon Island of the Philippines with Bashi Channel, Batan Islands, Balintang Channel, and Babuyan islands situated in between.
Lying between Asian continent and Philippine Sea basin, the NNE-SSW trending island Taiwan is geographically commonly regarded as a constituent of the island-arc system along the western edge of the Pacific Ocean. Geologically, this island is a late Cenozoic orogenic belt connecting Ryukyu Island-arc to the north and Philippine Island-arc to the south; it took shape following a vigorous orogeny (Penglai Orogeny) initiating a few million years ago at the site of thick (over 10,000 m) Cenozoic geosynclinal deposition on a pre-Tertiary metamorphic basement. A great amount of Tertiary sediments have been subjected to induration or metamorphism. On the other hand, large intrusive rocks are rare, and volcanic rocks are only found along the western and eastern margin of the island. Earthquakes happens frequently nowadays, some of them are severe; this indicates that this island remains in young tectonic adjustments. [For a topographic map of Taiwan see Figure 1 of this introductory series on page 18-A; a geologic map appears as Figure 2 of this series on page 18-B.]
Taiwan looks somewhat like a well-developed storage root of sweet potato. Extending 394 km along its longest axis (ca. 25°0' N to 21°5' N) and stretching 140 km at its broadest transection, this island measures about 35,800 km2. The Tropic of Cancer neatly slices through its middle part. With 30% of its area strongly undulating between 1000-3000 m above sea level, Taiwan is by no means low-lying. Peaks above 3,000 m in elevation amount to more than 200 in number; all of them are located within the so-called Central Range (in broadest sense). This lofty range runs basically following the axis of the island. Causally speaking, however, it is the physical setting and orientation of this range that has cast the outline of Taiwan. The collective name Central Range refers to four mountainous regions. It is first divided as a western part and an eastern one by a very long Lishan Fault. The lofty western part is further broken by a prominent topographic break to result in the Hsueshan Range in the north and Yushan Massif in the south. The eastern part appears to comprise two ranges: the lofty Backbone Range (= Central Range in narrow sense) immediately east of the Lishan Fault and a lower Eastern Taiwan Schist Range. Among the famous peaks of the Central Range as a whole are Yushan (3950 m alt., Yushan Massif), Hsueshan (3931 m, Hsueshan Range), Hsioukuluanshan (3883 m, Backbone Range), Nanhutashan (3797 m, Backbone Range), etc. Though comparatively lower in elevation, the slopes of the Eastern Taiwan Schist Range are mostly very steep or even precipitous.
The Hsueshan Range, Yushan Massif, and Backbone Range are built mainly of Paleogene slate, phyllite, argillite, and sandstone, in contrast with the schist, marble, and gneiss that are the major components of the Eastern Taiwan Schist Range. The geologic Upthrust Slate Belt is geographically corresponding to the lofty region of the main divide and the western mountains of the Central Range as previously defined. It is essentially a sub-metamorphosed, thick, monotonous succession of marine argillaceous sediments lying unconformably on a metamorphic basement. Though sparse, the various marine fossils containing in these argils clearly indicate a duration of sedimentation from Eocene to early Middle Miocene. Though customarily grouped in the same geologic belt, the notable difference between the western subbelt (Hsueshan Range plus Yushan Massif) and the eastern one (Backbone Range) in lithology and the grade of metamorphism may have stratigraphic and geotectonic significance and thus may eventually prove the existence of two distinct lithotectonic zones (Ho C-S, 1982; but also see Lu C-Y & Hsu KJ, 1992, in a different context). The geologic Paleozoic-Mesozoic Basement Belt refers to an extensive outcrop of a complex group of strongly metamorphosed volcanic rocks, limestones, and clastic sedimentary rocks that essentially constitute the Eastern Taiwan Schist Range geographically. This metamorphic complex ("Tananao Schist" stratigraphically) is generally considered to have formed between late Paleozoic and early Mesozoic or even late Mesozoic, based chiefly on some Permian marine fossils found in this region and the generally very high grade of metamorphism. This ancient complex is also traditionally believed to extend westward to be the basement of the Tertiary fold-thrust region of western Taiwan (see below).
Immediately west of the Central Range are Alishan and Chialishan Ranges, where the interbedded Neogene shale, siltstone, and sandstone rise to 1000-1500 m alt. This Western Foothills Zone is geologically equivalent to the Western Fold-thrust elt.
The thick (to 8000 m in eastern part) shallow marine to shelf clastic sediments in this miogeosynclinal basin are Late ligocene to Late Pleistocene in age.
Further west, largely unconsolidated Quaternary sediments lie conformably on the Neogene sedimentary strata (see above) that extends from the Western Fold-thrust Belt in the east to the Taiwan Strait in the west. These basically unfolded surface layers appear as the low-lying lateritic terraces in the northern part and Western Coastal Plain in the central and southern part of western Taiwan. These lowlands altogether occupy about one third of the island. They have been subjected to the eaviest utilization in