NPS photo

Cleome thrives in the clay rich soils at the Painted Hills.

After a tour around the 3 units of the John Day Fossil Beds, visitors can soon understand why names like gooserock, twickenham, sorefoot, drinkwater, and badlands are needed to describe the 80 plus soils types found on the monument.

With strong influences from the millions of years of geologic changes that have occurred in the region, these soils have developed in the recent past under a semi-arid climate and a grassland/sagebrush steppe vegetation community.

Erosion by physical, chemical, and climatic factors combined with the additions of organic matter from animals, plants, and microorganisms living both within and above the earths surface all combine in the natural process that develops soils.

Hard parent material like the basalt layers, so common to the monument, will take many years to break down to soil size particles. On the other hand, the soft tuffs and claystones from ancient volcanic ash may easily erode and be exposed to weatherization, but their chemical and other properties resist the development of soil properties needed for plants and microorganisms to become established.

Other factors limiting the development of soils include the limits that the 9-16 inch rainfall puts on weatherization of parent material and on plant establishment, and the very steep slopes (2% to 120% on some of the rock outcroppings) that allow erosion by water and wind to quickly remove any developing soils to other locales.

The John Day Fossil Beds has several extensive areas in the Sheep Rock and Painted Hills Units of exposed tuffs and claystones that only support a few very specialized plants.

The rest of the monument is covered with healthy native plant communities, each adapted to the soil types, aspects, topography, and availability of water unique to that particular point on the earth's surface. These plant communities range from cottonwood/sedge/basin wildrye communities in the deposited silts and loams along the rivers edge; to greasewood and saltgrass on the alluvial fans; to mountain mahogany/Idaho fescue/hedgehog cactus in the high elevation rocky outcroppings.

Cryptobiotic crusts comprised of algae, lichens, mosses, microfungi, and bacteria are also important components of many of the plant communities. They are often seen as a black crust or covering on the soils beneath the plants. These small organisms play an integral role in binding and protecting the soils from erosion, in fixing nitrogen for the plants to use, in storing water, and in the nutrient cycling process that further develops the soils.