Stem-Diameter Age Relationships of Tamarix ramosissima in Central Utah

Abstract

The stem-diameter age relationships of salt cedar from 15 study sites in central Utah were investigated. Age prediction equations were generated and found significant (p<.OOl). Within restricted geographic areas the stem ages of salt cedar could be estimated with fair reliability, but with substantial geographic separation results were less accurate. The impact of salt cedar invasion over prolonged periods of time was also assessed. Results indicated that the longer the community has been occupied by salt cedar the more xeric the habitat becomes. Saltcedar (Tamarix ramosissima) is a vigorous invader of pastures, moist lowlands and stream banks throughout much of the southwestern United States (Tomanek and Ziegler 1960). It is also found in dense thickets through much of central Utah (Christensen 1962). Saltcedar has the highest transpiration rates of any North American phreatophyte (Kiegler 1968) and can depress the water table often by as much as 1.2 to 2.1 m/ yr (Horton 1964). Although studies have been made of the distribution and naturalization of saltcedar (Christensen 1962, and Horton 1964), and of its ecology and habitat requirements (Tomanek and Ziegler 1960, Carman 1979), much less is known of its stem diameter: age relationship and/or population dynamics. Studies of the growth rings of trees have been used extensively for dating (Douglas 1935, Glock 1937) reconstructing past climates (Fruits 1971, Harper 1979, Schulman 1956, Stockton and Meko 1975) and interpretation of successional dynamics (Burkhardt and Tisdale 1969, Barney 1972). Data on shrubs are relatively rare (Ferguson 1958, 1959; Ferguson and Humphrey 1959) but should be equally valuable. Brotherson et al. (1980b) included saltcedar in their study of the size and age relations of 8 major tree species of Navajo National Monument, Ariz. The present study considers the stem diameterage relationship of saltcedar from 15 sites in central Utah and compares these relationships with the Arizona saltcedar population.