Germination in five shrub species of Maritime Pine understory—does seed provenance matter?

Abstract

Maritime Pine forests cover important mountain areas in Portugal and are known to be a particularly fire-prone forest type. Understory composition plays an important role in maintaining biodiversity and ecosystem services after recurrent wildfires. This study aims to improve the knowledge on the germination ecology of understory species of Maritime Pine forests, focusing on the importance of seed provenance, including in relation to germination enhancement by heating. The selected species were Cistus ladanifer L., Erica australis L., Erica umbellata L., Pterospartum tridentatum L. (Willk), and Genista triacanthos Brot. Seeds were collected from two or three distant populations. Besides a control treatment, two heating regimes were applied, i.e., 100°C during 5 min and 80°C during 30 min. Heating treatments significantly enhanced germination in four out of the five species. Differences between provenances were most evident for C. ladanifer and E. australis, especially following the heating treatments. Overall, the seeds from the southern provenances germinated better and, at the same time, were smaller. The present results confirmed that seed provenance should not be ignored as a key factor in germination ecology, so that further work is needed to untangle the roles of environmental and genetic factors in the observed differences between provenances.