Alternate successional pathways
This looping, 5-part slide show takes several repetitions to fully digest. The blocks represent an acre, about 200 feet on a side. Since spruces can reach 200 feet on stream deposits, an alluvial forest acre could be visualized as a cube 200 feet on a side. As you watch the trees rise and fall (to flooding and logging), notice that the upper, streamside forest never enters the shady, depauperate understory stage so dreaded by wildlife ecologists.
Here’s a pdf showing the same acre-block comparison, with more detailed annotation. Uplands versus bottoms.