Genetic and temporal plastic variation in bud burst, bud set and flower opening responses of local versus non-local provenances of Prunus spinosa in a provenance trial

Natural populations of woody species are adapted to local growth conditions. Non-local provenances may sense the difference between the local environment and the site conditions at their origin. To study the impact of provenance selection of planting stock in (re)forestation and landscape plantings, the variation in the adaptive traits bud burst, bud set, flower opening, leaf morphology and height increment was examined within and between local and non-local provenances of Prunus spinosa in a provenance trial, located in Flanders (northern part of Belgium), during two consecutive years (shrubs were three and four years old) which contrasted strongly in spring temperatures. Five Flemish provenances were included together with three commercially available provenances originating from Wallonia (southern part of Belgium), Hungary and Spain. When comparing the two observational years, the Spanish provenance showed a plastic temporal response in bud burst, while the Hungarian provenance and to a lesser extent the Walloon provenance responded plastically in bud set. The Hungarian provenance flushed first in 2013 but was not the first to flush in 2014, whereas in 2014 flowers opened first. The rank order among the provenances in flushing was not maintained in flower opening although both phenophases occur congruently. Wide-leaved shrubs tended to flush and flower slightly earlier and to grow slightly quicker compared to narrow-leaved shrubs, possibly as a result of historical hybridisation processes. Height increment did not vary significantly between the Flemish and commercial provenances, except the Hungarian provenance, which showed a slightly retarded youth growth. The different responses between local and non-local provenances may indicate maladaptation of the latter.