SCRUBLAND

area of low, evergreen, leathery-leaved, and often aromatic shrubs (or scrubs), commonly called Mediterranean vegetation. Scrublands are limited primarily to seacoast regions that have dry, hot summers and cool, wet winters. Scrublands are found along the seacoasts of the Mediterranean Sea, western and southern Australia, and on the western coasts of both North and South America, in latitudes between 30 and 40 both north and south of the equator. These regions have a cover of dense vegetation that thrives during the winter months when there is adequate rainfall and temperatures during the night rarely fall below 10 to 15 C (50 to 60 F). Except for a very few common plant genera, the scrublands in each continent produce different flora. The western coast of North America, particularly California, produces a kind of scrubland called the chaparral. The annual rainfall there varies between 250 and 500 mm (10 and 20 inches), and the summer is very dry. Annual plants like goldfields, tree poppies, and forget-me-nots are produced, along with perennials like the scrub oak, sages, mountain lilacs, and in drier inland regions, chamise and ribbon-woods. Along the lower slopes of mountains bordering the Mediterranean Seai.e., in North Africa, Greece, southern France, Spain, and the western coast of the Middle Eastare found scrublands called the macchie, which are dominated by mints, laurels, myrtles, brooms, rosemary, thyme, and olive and fig trees. Much of the original macchie has been transformed by human irrigation practices into crop-producing lands. The world's most extensive scrublands are found in Australia, which also provides the richest variety of scrubland flora. Scrublands predominate in those areas of western Australia that receive between 380 and 1,000 mm (15 and 40 inches) of rainfall annually. These scrublands support a total of about 1,000 species of scrubs, including members of the pea family, myrtles, sundews, and shrubby species of eucalyptus and acacia. Scrublands in general do not change much in the course of a year. Most scrubland plants are evergreens, and the only marked change they undergo during seasonal variation pertains to leaf colour. During the dry summer months the leaves are olive green, but they are replaced by bright green new foliage during the wet months of winter. The growing season in scrublands is usually confined to the wet winter months, when temperatures rarely fall below freezing. The favourable winter climate allows seeds to germinate after sufficient rain has fallen. The most pronounced seasonal changes in the flora of scrublands are provided by annual plants, which complete their growing cycle during winter, before the onslaught of parched summer conditions. Long periods of drought common to scrublands can kill many plant species that are not sturdy enough to thrive in desertlike conditions. The droughty summer months also make scrublands prone to fires, which sweep across the coastal plains and slopes, burning to their forest or desert boundaries. The fires do not eradicate most of the flora, however, because most scrubs sprout from their crown roots close to the ground and thus can usually regenerate themselves in one or two years. Scrublands are not hospitable environments for most animals. The vegetation is dense, making it difficult for medium-sized and large mammals to travel through, and most of the aromatic herbs and scrubs are disagreeable or even toxic to many animals. Small seed-eating animals such as pocket mice and kangaroo rats may be found in scrublands, however. Insects, insect-eating birds, and reptiles also forage in scrublands, though they prefer to dwell in more habitable environments. Figure 1: Worldwide distribution of scrubland vegetation. also called shrubland, heathland, or chaparral, diverse assortment of vegetation types sharing the common physical characteristic of dominance by shrubs. A shrub is defined as a woody plant not exceeding 5 metres (16.4 feet) in height if it has a single main stem, or 8 metres if it is multistemmed. The world's main areas of scrubland occur in regions that have a Mediterranean climatei.e., warm temperate, with mild, wet winters and long, dry summers. These areas include southern Australia, the Mediterranean region, California, Chile, and South Africa. Other scrublands are found in the semiarid tropics and in the Arctic, but smaller areas also occur in many other places. Australia, primarily because of its dry, variable climates, probably has the greatest expanse and range of scrublands. Their distribution is shown in Figure 1. Jeremy M.B. Smith Additional reading Mediterranean scrublands are exhaustively treated in two works: Francesco di Castri and Harold A. Mooney (eds.), Mediterranean Type Ecosystems: Origin and Structure (1973); and Francesco di Castri, David W. Goodall, and Raymond Specht (eds.), Mediterranean-Type Shrublands (1981). Valuable regional accounts can be found in the essays collected in R.M. Cowling (ed.), The Ecology of Fynbos: Nutrients, Fire, and Diversity (1992); and R.H. Groves (ed.), Australian Vegetation, 2nd ed. (1994). Jeremy M.B. Smith