Tall fescue and its close relatives in the Festuca-Lolium complex have a complicated and variable genetic makeup (see Chapter 2), which helps explain their wide range of adaptation and use. Tall fescue is native to Europe, northern Africa, and western and central Asia (see Chapter 1). It has been introduced to and successfully grown in North and South America, southern Africa, Australia, New Zealand, and eastern Asia. It is now one of the most widely grown temperate, perennial grasses in the world. Its adaptation and suitability are limited primarily by extremes of temperature, soil water availability, and physical and chemical characteristics of soils. Management also can limit or enhance persistence in areas of marginal suitability. Perennial ryegrass (L. perenne L.) often is the preferred pasture grass in cool, temperate, maritime climates; however, tall fescue might be preferred in some of these areas specifically for winter grazing. Tall fescue has a more extensive range of suitability in zones where water is less abundant or unevenly distributed and where hot summers occur. Tall fescue also has a more extensive range of suitability in zones where low winter temperatures occur. The use of tall fescue and its more arid-adapted relatives may increase as climate change brings higher temperatures and possibly more severe water-deficit stress to livestock-producing areas.
A new technique is demonstrated in this chapter. This method, involving modern spatial analysis modeling and mapping techniques, allows describing and delineating the environmental limits that define suitability zones for tall fescue in the United States and China. This technique may be applied to other countries where the required climatic and edaphic inputs are available. Although adaptation and suitability are terms often used nearly interchangeably, in this chapter we differentiate the two. Adaptation refers to the ability of tall fescue to persist through the normal fluctuation of environmental conditions prevailing in an area, while suitability refers to its potential to contribute significant annual yield to plant communities managed for forage. The Internet Mapserver application (http://gisdev.nacse.org/prism/forages/, verified 19 Mar. 2010), developed by the PRISM Group (http://prism.oregonstate.edu, verified 19 Mar. 2010), was used to create tall fescue suitability maps for combined components of climate and soil characteristics over a selected period of time.
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