A "forgotten forest" of small tree species require conservation efforts similar to those needed to protect taller trees, a charity has said.
Moray-based Trees for Life said some species such as dwarf birch were becoming scarce in the UK.
The charity has included what it calls "wee trees" in projects to restore ancient woodland, and to plant a million trees across Scotland.
Other small, upland species include rowan and eared willow.
As part of the conservation effort, scientists have sequenced the entire genetic code - the genome - of a dwarf birch from Trees for Life's Dundreggan Estate in the Highlands.
The charity said the work by Queen Mary University of London would aid its efforts to restore areas of ancient Caledonian woodland on the estate in Glen Moriston.
Alan Watson Featherstone, executive director of Trees for Life, said: "This is a tremendous breakthrough.
"Together with our woodland restoration work at Dundreggan, where we have one of the greatest concentrations of dwarf birch in Scotland, it will do much to benefit the conservation of this important species."
Richard Buggs, lead scientist on the genome project, said: "Increasing our understanding of tree genomes is essential for our long-term ability to conserve and grow tree species in the UK."
Trees for Life said small tree species represented a "forgotten forest" in the UK.
It said healthy populations of dwarf birch benefited birds such as black grouse, ptarmigan and golden plover on upland moors.
Rowan grows at a higher altitude than any other tree in the UK and occurs at almost 1,000m (3,280ft) in parts of the Highlands, according to Trees for Life.
It said eared willow grows in moist, slightly acidic soils throughout Scotland, including the Western Isles, Orkney and as far north as North Voe on mainland Shetland.