Ecology of seed germination of Pinus sylvestris L. at its southern, Mediterranean distribution range

Abstract

Seed germination of Pinus sylvestris L. in south eastern Spain was studied under field and growth chamber conditions to assess the effect of the most representative microhabitats of these forests. Under growth chamber conditions, germination was high (almost 95%) in the litter from all microhabitats. Germination under field conditions was highest (up to 95%) in shade-free microhabitats and therefore higher soil temperature (e.g. areas of bare soil and meadows), and lowest (down to 62%) in microhabitats with dense canopy shade and thus lower soil temperature (e.g. under the canopy of pines and under the canopy of juniper). Nevertheless, germination was high also in shaded microhabitats in a year with high rainfall during the germination period, supporting the hypothesis that germination was determined by a combination of appropriate levels of soil temperature, moisture, and light intensity. In contrast, biotic speciesspecific characteristics of the microhabitat were not relevant. Germination may thus reach high percentages in all the microhabitats of the understory during rainy years that ensure appropriate soil moisture during the germination period. However, during dry years germination will concentrate in sunny microhabitats because they reach higher soil temperature early in the season before soil desiccation. These patterns have implications for forest management and stand regeneration via direct seeding.