DECIDUOUS AND EVERGREEN HABIT FOR CRETACEOUS POLAR CONIFERS?

For most of the geological past high latitude regions were covered by dark dense forests. These forests would have significantly modified both the polar and global climate due to their low albedo and their effect on the land-surface heat budget and hydrological cycle. The leaf life span of conifers and their deciduous or evergreen habit would have played a significant part in this feedback. However, in the past this habit has been difficult to assess in fossil floras. A new technique that characterises the cell patterns within growth rings in fossil wood, developed by Falcon-Lang, can be used to determine whether fossil conifers were deciduous or retained their leaves for several years. This technique has now been applied to Early Cretaceous conifer wood from Svalbard. Analyses of tree taxa and growth rings indicate that the conifers, including for example Piceoxylon, Cedroxylon and Juniperoxylon, grew under strongly seasonal and often variable climates. The conifers had an evergreen habit, even though they lived at palaeolatitudes of ~70°N. This would have primed them for photosynthetic activity as soon as ambient conditions, especially light, reached suitable levels and was likely to have been an important strategy for survival.