Effects of global climate change on apple 'Golden Delicious' phenology - based on 50 years of meteorological and phenological data in Klein-al Tendorf

Meteorological and phenological analogue data were digitised and correlated to a) assess whether and when the climate had changed at Klein-Altendorf, and b) examine its impacts on fruit growing. Meteorological data over 50 years (1958-2007) came from the research centre’s own weather station and included air and soil temperature as well as precipitation records. Phenological data over 50 years on filing cards were calendar dates of full bloom, harvest and leaf drop, as well as late frost and consequent yield loss, for a range of apple and pear cultivars, using only bearing fruit trees at the time. This involved 1) the use of several generations of fruit trees/orchards and 2) use of original pome varieties, which existed as bearing trees since 1958, and were replanted after the orchard had been grubbed. Analysis and correlation of the meteorological data from the last 50 years showed two distinct climate phases in Klein-Altendorf, an earlier 30 year period (1958-1987) with a temperature of -0.42°C below the long term, 50-year average of 9.40°C, followed by a 20 year period of a +0.60°C temperature rise (1988 to date). A comparison of the phenological data of phase 2 (1988 to date) with phase 1 (1958-1987) showed 10 days earlier full bloom, 11 days earlier harvest and 4 days earlier leaf drop in the later phase, resulting in a 5 day longer growing period for cultivar ’Golden Delicious’ at Klein-Altendorf. An extended vegetation period offers the possibility for growing later-ripening varieties. There was no change in the amount of annual precipitation of 594 mm in Klein-Altendorf over the 50 years of observation and records, but the relative distribution changed slightly from about 50 mm less precipitation in the summer during the fruit growing period to the spring period.