Andrew T. Smith and Xie Yan
There have been many attempts to describe China’s diverse landscape. Conventionally, China has been divided into three
major physical geographic regions: the Tibetan Plateau, northwest arid China, and eastern monsoon China.
The Tibetan Plateau is one of the highest and most remote landscapes on Earth. The plateau averages between 3,000 and 5,000 m in elevation and encompasses roughly a quarter of China. The word “plateau” is a misnomer, as this area is crisscrossed by numerous impressive mountain chains, such as the Anyemaqin Shan, Bayan Har Shan, and Tanggula Shan, and many smaller spur ranges. Nevertheless, approximately 70 percent of the plateau is composed of alpine meadow or semisteppe vegetation. The Qaidam Basin, an interesting area of tectonic collapse, is found at the northern extreme of the plateau at an elevation of only 2,600 m.
The arid northwest encompasses about 30 percent of China and represents an eastern extension of the great Eurasian deserts and grasslands. One of the world’s most desolate deserts, the Taklimakan (translation: “those who go in do not come out alive”) lies north of the Tibetan Plateau and the Kunlun range. The cooler Dzungarian Basin, China’s secondlargest desert, lies in the far northwest. Various smaller deserts extend to the east, increasingly interspersed with semidesert and temperate steppe grasslands. Finally, the rocky Gobi Desert occupies the northern part of China and extends into Mongolia. Two of Asia’s major mountain ranges break up this barren expanse in the northwest: the Tian Shan and the Altai. One can stand below sea level in Turpan Pendi and clearly see the snow-capped top of Bogda Feng (in a spur of the Tian Shan) at 5,445 m.
Eastern monsoon China comprises about 45 percent of the country but is home to roughly 95 percent of China’s human population. This land is crossed by major rivers that originate on the Tibetan Plateau, most notably the Huang He (Yellow River) and the Yangtze. Almost all of the arable land has been converted to agriculture, and much of the original forest habitat has been destroyed. Most of this landscape is low in elevation and consists of broad alluvial valleys, coastal plains, and modest ancient mountain ranges. The south is seasonably humid, and the plains are punctuated by dramatic limestone pillars. The climate becomes increasingly temperate toward the north, with deciduous trees giving way to expansive coniferous forests in the far northeast.
These physical geographical regions, however, do not adequately define the major bio-geographic divisions in China. Bio-geographically, China’s flora and fauna have been affected by both historical factors (their derivation from two formerly isolated bio-geographic realms—the Palaearctic and the Indo-Malayan) and their relative ability to colonize new habitats.
The southern boundary of the Palaearctic realm in China and adjacent countries was analyzed by Hoffmann (2001),
particularly with regard to the distribution of mammals. He found extreme compression of the zone of overlap between the Palaearctic and Indo-Malayan realms along the southern boundary of
western China, as this region is defined by high altitudinal relief. In contrast, in areas of low relief (such as in eastern central China), the zonation is determined more by latitude than
altitude, and there is a broad latitudinal band of overlap between forms that originated from the Palaearctic and Indo-Malayan realms (Hoffmann 2001). In the south this zone extends from about
28° N on the coast to roughly 25° N in the area in northern Yunnan where the three great rivers (Yangtze, Mekong, Salween) lie in close proximity. The northern edge of this zone essentially
follows the Yangtze River from the east coast to the area where the three great rivers come together (Hoffmann 2001). This description contrasts with previous opinions that the southern limit of
the Palaearctic in China largely corresponds to the latitude of the Huang He in eastern China.
A sensitive and objective approach to understanding the zoogeography of Chinese mammals has been developed recently by Xie et al. (2004a). They defined 124 biogeographic units in China based on a comprehensive suite of factors (altitude, landform, climate, vegetation, hydrology, etc.) and then overlaid maps of 171 diagnostic mammal species on these units. A statistical analysis identified aggregations of biogeographic units based on mammal distributions, and this information was used to create cluster dendrograms. This analysis produced a classification of the boundaries dividing the mammal fauna at different spatial scales across China. A similar analysis was performed on 509 representative plant species.
The biogeographical divisions of mammals and plants in China determined by the methodology outlined above contrast significantly with the commonly used physical geographical regions for China. Additionally, there are distinctive differences between the biogeographical divisions using the plant and mammal data. Four major biogeographical divisions occur in China based on vegetation: northeast, southeast, southwest, and northwest. These in turn can be broken down into 8 subareas and 27 regions . Compared with the physical geographical regions, the major divisions based on plants separate the arid northwest into a western and eastern section, and eastern monsoonal China into a northern and southern part. The southwest China biogeographical region for plants is basically similar to the Tibetan Plateau physical geographic region, although both the northern and southern boundaries of the biogeographical region are found farther south than the physical geographical region.
There are three major biogeographical divisions for mammals . As for plants, the mammals have distinctive western and
eastern distributions in the arid northwest geographical region; the divisional boundary for mammals occurs farther west than that for plants . The mammals also separate eastern monsoonal China
into northern and southern areas, and the boundary for mammals is further south than that for plants. In the large arc from northwest to southeast China, there is a single mammal biogeographical
boundary compared with two for plants. Mammals in the interior drainage area on the Tibetan Plateau have northern affinities. The southeastern plateau region shows a continuous extension in
faunal affinities to the southeast, maintaining a mammal fauna more similar to that of monsoonal southeastern China.
In northwest China the montane forests and grasslands of the Tian Shan and Altai mountains clearly are distinct from the surrounding arid landscape. The Altai shows clear ties to the fauna of Russia’s boreal forest. As a result, Zhang and Zhou biogeographically linked the Altai with the Greater Xing’an mountains of northeast China. However, more than twice as many Altai mammals occur simultaneously in the Tian Shan mountains and the arid Dzungarian Basin as in the Greater Xing’an mountains.
In northeast China there are distinct differences in vegetation between the Greater and Lesser Xing’an mountains, whereas mammal distributions are similar between these ranges, and the area can be classified as a single region.
Overall, the analysis of Xie et al. (2004a) demonstrates that the ability to colonize varies between plants and animals, producing distinctive differences in the cluster analysis and the designation of major biogeographic areas in China. While plant distributions tend to be closely tied to prevailing environmental conditions, mammals generally exhibit broader geographic tolerance. Additionally, mammal distributions appear to be truncated by major rivers and mountain chains, whereas these do not appear to be as stringent barriers to plant distributions. Thus plant divisions appear to be more reliable than those of mammals as a general descriptor of China’s biogeography.
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