Date of this Version
Natural Resource Report NPS/NRPC/NRR 2010/172 / NPS 656/100866, January 2010, xvii, 99 pages
This report was prepared under Task Agreement J6067070012 of the Great Plains Cooperative Ecosystem Studies Unit (Cooperative Agreement between the National Park Service and the University of Nebraska-Lincoln CAH6000060100).
Published by the United States Department of the Interior, National Park Service, Natural Resource Program Center, Fort Collins, Colorado
Also available at: http:snr.unl.edu/gpcesu
Please cite this publication as:
Narumalani, S., G. D. Willson, C. K. Lockert, and P. B. T. Merani. 2010. Niobrara National Scenic River condition assessment. Natural Resource Report NPS/NRPC/NRR—2010/172. National Park Service, Fort Collins, Colorado.
Niobrara National Scenic River spans a 122-km (76-mile) long reach of the Niobrara River in rural, north-central Nebraska. The scenic river encompasses 9,338 ha (23,074 acres) of land and water, all of which is in private ownership, except for about 320 ha (790 acres). Because the scenic river does not own land, it achieves management goals by coordinating and collaborating with federal, state, and local jurisdictions and private landowners.
The central Niobrara River Valley is often referred to as a “biological crossroads” with plant and animal species representative of northern boreal forest, eastern deciduous forest, rocky mountain coniferous forest, tallgrass prairie, Sand Hills prairie, and mixed-grass prairie. Important natural resources include the Niobrara River; tributary springs and waterfalls; diverse plant and animal communities including Pleistocene relicts; and sandy shorelines, sandbars, and wetlands.
This condition assessment was undertaken to provide NPS managers, interpreters, and planners with a concise synthesis, and “scorecard”, of the most current information on the natural resources in and around the scenic river. The assessment is divided into four sections: (1) Ecological Context provides an overview of the natural resources of the scenic river and region; (2) Natural Resource Condition identifies habitat indicators and associated measures, assigning a condition and trend score to each indicator; (3) Stressors and Management Strategies discusses stressors and proposes management strategies; and (4) Conclusion determines an overall condition and trend score for major habitats.
The major habitats in the scenic river—as identified by natural resource studies—are Niobrara River and tributaries; upland forest and savanna; spring branch canyon and riparian forest; grassland; and sandy shorelines, sandbars, and wetlands. These habitats provide the ecological framework for this assessment, and their condition and trend are assessed by a suite of biodiversity and process indicators. Indicator condition was characterized as poor (red box) or good (green box) and trend was characterized as deteriorating (down arrow), stable (horizontal arrow), improving (upward arrow), or no trend or insufficient data (no arrow). These characterizations were based on a comparison of reference and existing values for the measures of each indicator. The scored indicators and their condition and trend are:
aquatic macroinvertebrates good and no trend
cool-water fishes good and no trend
fish community good and stable
stream flow poor and deteriorating
elk good and improving
ponderosa pine poor and deteriorating
land cover (upland forest and savanna) good and improving
fire (upland forest and savanna) poor and deteriorating
paper birch poor and deteriorating
hybrid aspen poor and deteriorating
Bailey’s eastern woodrat good and no trend
grassland birds good and deteriorating
Sand Hills prairie good and deteriorating
land cover (grassland) good and improving
fire (grassland) poor and deteriorating
interior least tern and piping plover good and improving
purple loosestrife poor and improving
In addition, five indicators, river otter, spiny softshell turtle, bird hybridization, whooping crane, and sediment transport were included but not scored due to lack of site-specific information. They were discussed to highlight rare or unique resources and important information needs.
The scenic river’s long, narrow corridor and limited conservation ownership in the watershed makes it highly susceptible to stressors originating from adjacent lands. The major stressors emerging from this condition assessment are:
water diversion and withdrawal: water diversions from the Niobrara River and tributaries have significantly altered its runoff hydrology and may impact ecological processes and biota.
water quality degradation: fecal coliform and phosphorus are elevated in some tributaries possibly due to visitors hiking in streambeds.
visitor river floating: floater days in the scenic river increased substantially between 2005 and 2008 and recreational noise may impact waterbirds and other wildlife.
purple loosestrife infestation: herbicides and biocontrol appear to be successful in reducing infestations but the plant continues to invade new areas.
woodland expansion (fire suppression): fire suppression and changes in the grazing regime have allowed ponderosa pine and other woody plants to spread into grassland and to increase in woodland understory.
drought: with reduced stream flow due to water diversions, drought impacts on river ecological processes and biota may be more severe.
microclimate in birch stands: a key factor contributing to birch dieback may be increased frequency of thaw-freeze events.
spring branch hiking: visitors walking in the streambed of spring branch tributaries results in a variety of physical and biological impacts.
Other existing or potential stressors are leafy spurge infestation, common reed infestation, mountain pine beetle infestation, and emerald ash borer infestation.
Based on a subjective evaluation of the indicators of the major habitats, their condition and trend are:
Niobrara River and tributaries good and no trend
upland forest and savanna poor and deteriorating
spring branch canyon and riparian forest poor and deteriorating
grassland good and deteriorating
sandy shorelines, sandbars, and wetlands good and stable
Priority management strategies to address stressors include pursuing instream flow rights to the Niobrara River to protect recreational and fish and wildlife resources, continuing herbicide applications and biocontrol to reduce purple loosestrife infestations, supporting the use of prescribed fire and the monitoring of fire effects by cooperating private and public land owners, and stimulating birch seedling establishment via mechanical removal of surface litter and overstory canopy. Future stressors may include the mountain pine beetle and the emerald ash borer. Both species have the ability to substantially alter plant communities and their resident wildlife. In addition to the vital-signs monitoring that will be initiated in the near future by the Northern Great Plains Inventory and Monitoring Network, monitoring in cooperation with the Nebraska Game and Parks Commission should be considered for river otter, cool-water fishes, fish community, spiny softshell turtle, elk, and Bailey’s eastern woodrat. Important research needs include recreation impacts on spiny soft-shell turtles, reduced stream flow impacts on river morphology and biota, changes in bird hybridization rates and locations, and impacts of existing and potential invasive plants and insects.
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