Heritage: 25,000 to 10,000 years ago
Late Pleistocene Environment: 25,000 to 10,000 years ago
The nearer we get to the present, the more detailed is the information we have about the history of the environment. The plants and animals which existed became increasingly like those which exist today. The basic geography and geology of the area has not changed significantly in the last 25,000 years. The primary exception to this is the existence of glaciers in the mountains above 5,000 feet and the existence of lakes and extensive marshes in the lowlands. In general the climate was much cooler and wetter. The John Day Valley itself probably had a larger river and a more extensive marshy shoreline. Upland valleys like Bear, Logan and Fox had extensive marshes with potholes and lakes. Just to the south of the Forest, the lakes of the Harney Basin were all joined together into a
The late Pleistocene vegetation differed from that of today primarily because it was adapted to a colder, moister climate. Sub-alpine and montane conifer forests of spruce, hemlock, larch, cedar, pine and fir covered the mountains and uplands. Mountain mahogany, wild cherry, buck brush and sage formed the forest understory. Grasses and sedges occurred both in forests and dry open areas. Cattails, tule, camas and other marsh plants dominated the well watered lowlands. Sage and juniper were much less common than they are today but they occurred in the same ecological niche, between the conifer forests and the grasslands. This niche was smaller because the cooler, wetter climate created larger wet lands and forests at the expense of the grasslands and juniper/sage steppe. The climate grew warmer and drier as it approached the Holocene and the grasslands and steppe increased at the expense of the forests and wet lands. These changes did not take place at the same time in all locations. Site specific environmental constraints such as aspect, nearness to water, elevation and local weather patterns all influenced the plant communities. An excellent example of this is the relic stand of cedar which exists in a deep, cool, and humid gulch on the north flank of Aldrich Mountain. The next nearest stand of this timber is located over 100 miles to the west. It is thought that during the Pleistocene these trees were fairly common in the Blue Mountains and that this stand survived the drying trend because of it's unique setting.
Although in many basic ways the plant communities of the late Pleistocene are similar to those of today, the animal communities which depended on them were quite different. Particularity distinctive were the large numbers of birds and mammals which went extinct at the end of the Pleistocene and in the early Holocene. These include the