- This 1,920-acre site and its surrounding landscape are characterized by steep, rugged terrain and narrow canyons that terminate at the edge of the Columbia River. The preserve contains one of the largest known populations of Thompson’s clover, a plant that is state-listed as “threatened,” and a population of longsepal globemallow, a state-listed “sensitive” plant. The preserve, which also contains grasslands and scattered ponderosa pine and Douglas-fir, is susceptible to-and has evolved with-frequent natural fires. The rare plants at this site are adapted to this fire regime. Thompson’s clover relies on fire to remove encroaching trees and reduce competition in its habitat, while fire and heat enhance seed germination for longsepal globemallow, resulting in dramatic increases on the preserve following the most recent wildfires in 1988 and 2014.