When a tree falls, it becomes a nurse log for the next generation. In rain forests, a nurse log might have several saplings growing on it in a colonnade. In parks, this view is more common. This nurse log contains cleavers (Galium aparine), the taller plant with narrow leaves. It's called cleavers because there are tiny barbs on the leaves and seeds. Siberian miner's lettuce (Claytonia sibirica) is in the middle of the log. Fringecup (Tellima grandiflora) grows along the ground in the foreground. I think the moss is Menzies' Tree Moss (Leucolepis acanthoneuron).
Full size here.