Tree growth and d 13 C among populations of Pinus greggii Engelm. at two contrasting sites in central Me ´xico Ricardo Garcı ´a-G a , Armando Go ´mez a,* , Javier Lo ´pez-U a , Jesu ´s Vargas-H a , William R. Horwath b a Colegio de Postgraduados, Programa Forestal, IRENAT, Km 36.5 Carr. Mexic-Texcoco, CP 56230 Montecillo, Mexico b Department of Land, Air and Water Resources, Soils and Biogeochemistry Section, University of California, Davis, USA Received 6 August 2003; received in revised form 27 October 2003; accepted 21 April 2004 Abstract Basal area growth and carbon isotopic composition (d 13 C) of three Pinus greggii Engelm. populations were correlated to climate variables at two contrasting common garden sites. The populations were Molango (MO), Pin ˜o ´ n (PI) and Zimapa ´n (ZI), all native to the state of Hidalgo. The test sites included a low-precipitation (800 mm) and high-elevation site (2600 masl) at Metepec, Mexico (ME), and a high-precipitation (1833 mm) and low-elevation site (1440 masl) at Huauchinango, Puebla (HU). The MO population had the highest variation in productivity with 15 m 3 ha 1 per year at the HU site and 7.7 m 3 ha 1 per year at the ME site. The PI population had the best tree growth at the ME site with an estimated production of 11 m 3 ha 1 per year. Trees at the ME site showed an average elevated d 13 C content of 2.67% compared to the HU site. Differences between sites in d 13 C were explained by differences in precipitation and altitude, which influenced water status and gas exchange processes in the different populations. Changes in soil water potential during the dry season matched differences in d 13 C observed at both test sites. At the site level, significant correlation between d 13 C and mean annual temperature were observed only at the HU plantation. Correlations for the HU site significantly improved when temperatures of the driest period of the year were considered. No significant correlation between d 13 C and annual precipitation among populations was found at the two sites. Correlation between d 13 C and basal area increment during a 5-year period was significant in MO and PI populations at the ME site, with correlations of r ¼0.42 (P ¼ 0.04) and r ¼0.40 (P ¼ 0.05), respectively. At the HU site only the PI population showed significant correlation between d 13 C and basal increment (r ¼0.43; P ¼ 0.03). Differences in wood d 13 C were consistently detected for the two contrasting environments. The results indicate that the wood 13 C signature provides a good integral index for screening P. greggii Engelm. population adaptation for dry sites. # 2004 Elsevier B.V. All rights reserved. Keywords: 13 C= 12 C; Subtropical pines; Mexican pines; Water use efficiency; Forest plantations 1. Introduction Tree growth and carbon isotopic composition (d 13 C) are two variables strongly influenced by site water availability (Leavitt, 1993). Some studies indi- cate that stem diameter growth and d 13 are related (Dupouey et al., 1993; Livingston and Spittlehouse, 1996; Walcroft et al., 1997; Gomez et al., 2002). These findings suggest that foresters could take advantage of this relationship to develop extensive methods that allow assessments of tree growth in forest plantations using retrospective information of d 13 C signatures Forest Ecology and Management 198 (2004) 237–247 * Corresponding author. Tel.: þ52-595-95-20200x1475/1467; fax: þ52-595-95 20256. E-mail address: agomezg@colpos.mx (A. Go ´mez). 0378-1127/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2004.04.007