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A project that began as an effort to rejuvenate and preserve 12 relict stands of aspen trees in and around Smith Falls State Park grew into something much larger that improved forest and grassland health throughout the park. It also spurred research that can guide future management and is providing interesting genetic background for these unique hybrids. Nebraska Game and Parks Commission horticulturists began recognizing the problem facing the aspens at Smith Falls, a hybrid between quaking and bigtooth aspens, even before the park opened in 1992. With natural fires controlled, invasive eastern red cedars were spreading through the forest understory and into adjacent grasslands, and in some places ponderosa pines had become too dense. This was the case not only in the park, but throughout the entire Niobrara River Valley, 76 miles of which below Valentine was designated in 1991 as a National Scenic River. The forest is comprised mainly of pine and oak, but a 30-mile reach that includes Smith Falls also includes stands of paper birch, a relict of the boreal forest, one of six ecosystems that meet here in what is considered a biological crossroads. Within that reach, aspens are known to grow only within a one- mile segment from just above the 200-acre park to the bend below it. Cedars and pines growing beneath and above the aspens inhibited the growth and survival of suckers, limiting regeneration in the stands, most of which consist of only a few old trees. Commission staff cleared cedars from beneath some stands in the mid-1990s. A decade later, the National Park Service took an interest in the aspens, and a partnership between the agencies and others was born, along with a plan to do more. Starting in 2008, staff from both agencies, as well as volunteers, used chainsaws to clear cedars and brush from beneath the aspen stands on the park, as well as those on adjacent land owned by The Nature Conservancy (TNC) and by Fred Krzyzanowski, who leases the land for Smith Falls State Park to the Commission. Knowing the aspens and the rest of the forest would benefit from a prescribed fire, the Commission sought and received $60,000 in grants from the Nebraska Environmental Trust, and additional funding from the Nebraska Forest Service, to hire a contractor to thin unwanted trees that would have made any burn unsafe. A skid-steer-mounted shear and grinder cleared every cedar that could be reached in 2010 and 2011. Additional work was done by hand in places the shear couldn't reach. The work reduced forest density by 50 percent or more. After scratching burn plans for two years because of weather that was either too dry or too wet, a TNC crew was finally able to burn the 65 acres that had been thinned in Smith Falls and another 3 miles of their Niobrara Valley Preserve downriver to Brewer Bridge. The results of both the thinning and the fire have been beneficial for the aspens, resulting in a substantial flush of suckers beneath the stands. Further work has been done to protect those suckers from browsing deer by erecting fence exclosures beneath the stands. A Park Service-funded study by James Robertson, a graduate student at the University of South Dakota, found that browsing severely limited the growth and survival of suckers that were not protected by fence or slash piles left when the stands were cleared. But the news is not all good for the Smith Falls aspens. Robertson's study examined the health of 10 of the 12 stands in 2013 and 2015, and found 80 mature trees, including dead or dying trees in all size classes. He found that the smaller, younger stands are stable to improving, but the older trees in larger stands continue to lose canopy and die, presumably the effect of competition for limited resources. Robertson said the conditions are similar to the Sudden Aspen Decline occurring across the range of quaking aspen, especially at the edges of their range, that is believed to be the result of a changing climate. A recent U.S. Geological Survey study documented warming temperatures in the spring-branch canyons along the river. The cool, moist microclimate in those north-facing canyons has supported paper birch, but that species is also in decline, a problem believed to be caused by drought and warm periods in early spring followed by late freezes. A study currently underway at the University of Minnesota will help determine if those same weather factors are affecting aspens. Hybrid aspens grown in greenhouses from cuttings taken at Smith Falls, as well as quaking and bigtooth aspens collected elsewhere in the northern Plains, are being subjected to extended drought and late freezes, conditions expected to increase, to see how each species responds. Nick Deacon, a post doctorate researcher leading the work, which also includes a genetic study of aspens from Nebraska, South Dakota, Iowa, Minnesota and Wisconsin, pr pr pr j oj oj ojec ec ec ec ec e t t th th th th th th th th th th th th th th th th t at at at at at at at at at at at at at beg egan an an an as an an an an eff ff ff ffor or or ort to to to rej ejuv uven en enat at ate an an and preser erve ve ve ve v 12 relict stands of aspen trees in and a fe fe fe few ol ol old tr tr tree ee ees. s. Com om om om i mi mi miss ss ss ssio io ion st staf af aff cl cl cl clea eare re re red ce ce ceda da dars rs rs fro ro rom beneath some stands in the mid-1990s. A decade later, the Aspens at Smith Falls g y suc pr pr p o ex e c by of S gro fen B Ro in 2 or you in l the sai occ the cha A wa the can in d wa A wil affe fro big are con re re r s th th th t e Ne Ne Many of the mature trees in aspen stands at Smith Falls State Park are in poor health, losing canopy and dying. 32 NEBRASKAland • OCTOBER 2016