Annual radial growth of tropical ash (Fraxinus udhei (Wenz.) Lingelsh.) in two parks of the La Laguna Region

Abstract

Tropical ash, a riparian tree with high water demand, is widely planted in urban parks of the Comarca Lagunera Region. Two ring-width chronologies were developed from selected trees in the Guadalupe Victoria park (PGV, Spanish acronym) and the Venustiano Carranza forest (BVC, Spanish acronym) covering the periods from 1905 to 2012 and from 1960 to 2012, respectively. Series intercorrelation and mean sensitivity values –0.44 and 0.359 for PGV, and 0.49 and 0.439 for BVC, respectively– were within the normal range, indicating interannual variability in growth. No significant relationship was found between annual precipitation and ring-width indices (p>0.05), however, for particular years with a precipitation below the mean (170 to 175 mm), radial growth was above normal, a situation that may be due to additional water supply through surface or pressurized irrigation. On the other hand, radial growth was lower during certain specific years with above-average precipitation, a situation that may be ascribed to a reduction or absence of water supply. Ring-width series showed that radial growth was lower than normal for certain years due to a combination of water deficit and other disturbances such as the movement of earth for construction purposes and the paving of roads. Comparison of ring-width indices between sites shows differences in management. The recent drop in growth of the older tropical ash trees of PGV has made them more susceptible to attacks by insects and diseases favored by water deficit.