Tree growth and delta C-13 among populations of Pinus greggii Engelm. at two contrasting sites in central Mexico
Garcia-G, R.; Gomez, A.; Lopez-U, J.; Vargas-H, J.; Horwath, W.R.
Forest Ecology and Management 198(1-3): 237-247
Basal area growth and carbon isotopic composition (delta(13)C) of three Pinus greggii Engelm. populations were correlated to climate variables at two contrasting common garden sites. The populations were Molango (MO), Pinon (PI) and Zimapan (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 delta(13)C content of 2.67parts per thousand compared to the HU site. Differences between sites in delta(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 delta(13)C observed at both test sites. At the site level, significant correlation between 613 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 delta(13)C and annual precipitation among populations was found at the two sites. Correlation between VC and basal area increment during a 5-year period was significant in MO and PI populations at the ME site, with correlations of r = -0.42 (P = 0.04) and r = -0.40 (P = 0.05), respectively. At the HU site only the PI population showed significant correlation between 613 C and basal increment (r = -0.43; P = 0.03). Differences in wood VC were consistently detected for the two contrasting environments. The results indicate that the wood 13(, signature provides a good integral index for screening R greggii Engelm. population adaptation for dry sites. reserved.