When I was working on the Spirit in the Grass book with photographer Chris Harris, one of the ecologists on the project told me that the effects of sun and shadow at the level of individual pebbles and grass blades certainly was a thing in the grasslands but too minor to be measured or have any significant effect. I have been watching the grasslands daily for a decade now, and I tell you, I think that assessment was wrong. Take a look at one little rock in the grasslands below.
What a lovely rock! The lichens have left nitrogen for the grass pushing out from the rock to the left, and heat held by the rock has made a dome which covers the grass, the sagebrush buttercup and the clump of balsam root stalks to the rock’s right. Some plants make heat by creating a mounded shape in subarctic environments. Here, the rock takes over that work. This little community is living off the nutrients, heat, water and protection collected by and offered by the rock. What’s more, the mound of vole debris left at the top of the rock is also likely here because of the rock’s ability to heat up uinder the snow. It has shifted down against the rock and the balsam root by snow melt, which the rock has damned, and pushed onto the plant. As the soil around the rock would have thawed under the snow, again because of the rock, the balsam root would have grabbed most of it, even while the world in the open air was frozen. Notice as well the mariposa lily blade (the flower will follow in a couple months) to the flower left, just on the edge of the water pool this rock has created in a dry land, where any exposed water vanishes into the sky. This is not a pristine grassland. All that fine green grass and fine thatch should be a lichen crust on the soil, but even though this cheatgrass is stealing water and making a desert, the stone counters it enough to keep the grasslands alive. That’s one stone. There are billions of them. We’d be nowhere without these oldest of ancestors.