It’s the edges, the margins, that always contain the most diversity. Large expanses of unbroken landscape take a portion of their character from their scale, a vastness, that the uninterested can often view as monotonous. Seemingly endless expanses of ocean, desert, prairies even forests, can lull some into indifference, a kind of blindness, in which they lose interest and fail to see the intricacy and richness of that which surrounds them….By overlapping two different landscapes places can take on a complexity that neither has alone…and may even arouse many of those inured to the natural world surrounding them. Two different landscapes sharing a common edge can form ecotones, where each landscape contributes species in patterns not found across the vastness of each alone. Cut a river through an arid landscape and it becomes altogether different often with stark changes within a few feet. Such is the arid canyon landscape of the Deschutes River immediately north of Bend, OR.
This is a typical community on the upslope side of the trail, native bunch grasses, Balsam, with other wildflowers and Bitterbrush and Sagebrush between widely spaced Pine.
Looking down slope from the trail and across the river you can see how abrupt the landscape changes as your move up and away from the river’s influence.
Gravity is the dominant force in any canyon, it’s what causes the water to flow which carves down through the earth’s sloping surface, cutting through rock and carrying the debris ultimately out to sea. The younger rock high up on the canyon’s rim erodes and along with the power of the freezing and thawing of ice fractures and splits away rock to tumble down into the canyon creating a slope of unconsolidated rock which itself is worn away by the river. The falling rock varies widely in size with massive rocks like this one bounding down until slope and friction bring it to a stop.
Rock and soil continue to wear away creating slopes that vary with the nature of the falling/collecting material, slopes that have a characteristic ‘angle of repose’. If the material falling away from the rim is roughly the same, so will be the angle of repose over time. Finer soils fill in the gaps and plants take root.
Ponderosa Pine dominates the next swath, top to bottom. As the river ‘digs’ deeper, the canyon broadens mainlining this general slope. The soils vary depending on the composition of the many layers of rock built up here. In general trees require deeper soils.
Rock is never just rock. There is chemistry going across their surfaces and are often covered with life, species dependent upon their composition, area climate and exposure. Only the newest rock, that recently cleft or fractured open, that is relatively free from life.
While this rock may look like it came to a stop against this tree, this Pine is relatively young and likely germinated at the rock’s base. The young tree may have benefited from the extra water afforded the site by the rock’s sloping surface and may have also helped shade/cool the soil slowing the possible desiccation of the tree. Successful plants take every advantage afforded them.