Geology topics

T. Shaffer

Publications and source records attributed to T. Shaffer.

2 recordsLinked to original sources

USGS2010

Discussion of "Natural hydrograph of the Missouri River near Sioux City and the least tern and piping plover" by Donald G. Jorgensen

The author analyzed stream-flow data from a single gauging station to predict preengineering flooding frequency for "sandbar islands adjacent to stream gauge on the Missouri River at Sioux City." He predicted dates that sandbars would be exposed and discussed his results relative to reproduction by least terns (Sternula antillarum) and piping plovers (Charadrius melodus). His analysis predicted sandbar inundation during nesting and concluded that "successful migrations of age-zero juveniles leading to recruitment would not have resulted from the use of the sandbar islands for attempted reproduction most years in the Sioux City area." We argue that the author (1) overlooked published historical records of breeding terns and plovers on the Missouri River and nearby systems, (2) inaccurately portrayed inundation for Missouri River sandbars and the importance of high flows for forming sandbars, and (3) underestimated these species' ability to withstand periodic reproductive failures. We conclude that the data do not support the author's contention that the preengineered Missouri River was "unfriendly" to terns and plovers.

Iowa↗

USGS2006

Community maturity, species saturation and the variant diversity- productivity relationships in grasslands

Detailed knowledge of the relationship between plant diversity and productivity is critical for advancing our understanding of ecosystem functioning and for achieving success in habitat restoration efforts. However, effects and interactions of diversity, succession and biotic invasions on productivity remain elusive. We studied newly established communities in relation to preexisting homogeneous vegetation invaded by exotic plants in the northern Great Plains, USA, at four study sites for 3 years. We observed variant diversity-productivity relationships for the seeded communities (generally positive monotonic at three sites and non-monotonic at the other site) but no relationships for the resident community or the seeded and resident communities combined at all sites and all years. Community richness was enhanced by seeding additional species but productivity was not. The optimal diversity (as indicated by maximum productivity) changed among sites and as the community developed. The findings shed new light on ecosystem functioning of biodiversity under different conditions and have important implications for restoration. ?? 2006 Blackwell Publishing Ltd/CNRS.

Ecology Letters↗