A new 368-year tree-ring chronology (A.D. 1643–2010) has been developed in western North Dakota using plains cottonwood (Populus deltoids subsp. monilifera) growing on the relatively undisturbed floodplain of the Little Missouri River in the North Unit of Theodore Roosevelt National Park. We document many slow-growing living trees between 150–370 years old that contradict the common understanding that cottonwoods grow fast and die young. In this northern location, cottonwood produces distinct annual rings with dramatic interannual variability that strongly crossdate. The detrended tree-ring chronology is significantly positively correlated with local growing season precipitation and soil moisture conditions (r = 0.69). This time series shows periods of prolonged low radial tree growth during the known droughts of the instrumental record (e.g. 1931–1939 and 1980–1981) and also during prehistory (e.g. 1816–1823 and 1856–1865) when other paleoclimate studies have documented droughts in this region. Tree rings of cottonwood will be a useful tool to help reconstruct climate, streamflow, and the floodplain history of the Little Missouri River and other northern river systems.
Adaptive restoration of river terrace vegetation through iterative experiments
DelaCruz, M.P., V.B. Beauchamp, P.B. Shafroth, C. Decker, and A. O'Neill
Areal cover and occupancy of woody riparian species near 456 streamgages in the western United States were obtained from site visits during the growing seasons of 1996–2002. We made concomitant estimates of grazing intensity, channel stabilization and incision, gradient, sediment particle size, and nearby planting of Russian olive. The purpose of this publication is to describe the data set and make it available to other investigators in an electronic format.
Climate Change Effects on Western Riparian Forests: Flood Timing, Tree Seed Dispersal Timing, and Seeding Establishment
Comparative inventories in 1969 and 1970 and in 2008 of vegetation from 30 forest stands downstream of Garrison Dam on the Missouri River in central North Dakota showed (a) a sharp decline in Cottonwood regeneration; (b) a strong compositional shift toward dominance by green ash; and (c) large increases in invasive understory species, such as smooth brome, reed canary grass, and Canada thistle. These changes, and others discovered during remeasurement, have been caused by a complex of factors, some related to damming (altered hydrologic and sediment regimes, delta formation, and associated wet—dry cycles) and some not (diseases and expansion of invasive plants). Dominance of green ash, however, may be short lived, given the likelihood that the emerald ash borer will arrive in the Dakotas in 5–10 years, with potentially devastating effects. The prospects for recovery of this valuable ecosystem, rich in ecosystem goods and services and in American history, are daunting.
Ecosystem response to removal of exotic riparian shrubs and a transition to upland vegetation
In the Southwestern United States, two exotic plant invaders of riparian habitats are tamarisk (Tamarix ramosissima Ledebour, T. chinensis Loureiro, and their hybrids) and Russian olive (Elaeagnus angustifolia L.). These plants were introduced by humans throughout the Southwest around 1900, and their success spreading across the region has coincided with human land-management activities such as river regulation. Both tamarisk and Russian olive have invaded Canyon de Chelly National Monument in Arizona. We addressed three broad research topics: the history of invasion, seedling establishment requirements, and the effectiveness of exotic plant removals. Our results indicate that the majority of tamarisk and Russian olives established in the mid to late 1980s, long after the original plantings and dam construction in Canyon de Chelly. This suggests that exotic plant invasion is most closely tied to precipitation and available seedling habitat, rather than river regulation or purposeful plantings...
Biologically-mediated flux of trace metals from streams to riparian spiders: a large scale survey in mineralized alpine ecosystems
Kraus, J.M., R.B. Wanty, T.S. Schmidt, D.M. Walters, and C.A. Stricker
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Society of Environmental Toxicology and Chemistry, November 13-18, 2011, Boston, Massachusetts