Publications

Accelerated nitrogen (N) inputs can drive nonlinear changes in N cycling, retention, and loss in forest ecosystems. Nitrogen processing in soils is critical to understanding these changes, since soils typically are the largest N sink in forests. To elucidate soil mechanisms that underlie shifts in N cycling across a wide gradient of N supply, we added 15NH415NO3 at nine treatment levels...

We used a simple model of carbon–nitrogen (C–N) interactions in terrestrial ecosystems to examine the responses to elevated CO2 and to elevated CO2 plus warming in ecosystems that had the same total nitrogen loss but that differed in the ratio of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN) loss. We postulate that DIN losses can be curtailed by higher N demand...

We examined diet of introduced Bullfrogs (Rana catesbeiana) and three native frog species (Rana limnocharis, Rana nigromaculata, and Bufo bufo gargarizans) co-occurring at a group of ponds on Daishan Island, east of China, to gain insight into the nature of potential interactions between Bullfrogs and native frog species. For postmetamorphic Bullfrogs, aquatic prey items dominated...

Taxonomic relationships among red tree voles (Phenacomys longicaudus longicaudus, P. l. silvicola), the Sonoma tree vole (P. pomo), the white-footed vole (P. albipes), and the heather vole (P. intermedius) were examined using 664 base pairs of the mitochondrial cytochrome b gene. Results indicate specific differences among red tree voles, Sonoma tree voles, white-footed voles, and...

Invasion of the exotic annual grass Bromus tectorum into stands of the native perennial grass Hilaria jamesii significantly reduced the abundance of soil biota, especially microarthropods and nematodes. Effects of invasion on active and total bacterial and fungal biomass were variable, although populations generally increased after 50+ years of invasion. The invasion of Bromus also...

We studied the relationship between microclimate and nest-site selection in the Pohnpei Micronesian Kingfisher (Todiramphus cinnamominus reichenbachii) which excavates nest cavities from the mudlike nest structures of arboreal termites (Nasutitermes sp.) or termitaria. Mean daily high temperatures at termitaria were cooler and daily low temperatures were warmer than at random sites in...

We examined nest-site spacing and selection of nesting cliffs by Peregrine Falcons (Falco peregrinus) in central West Greenland. Our sample included 67 nesting cliffs that were occupied at least once between 1972 and 1999 and 38 cliffs with no known history of Peregrine Falcon occupancy. We measured 29 eyrie, cliff, and topographical features at each occupied nesting cliff and unused...

Introduced American bullfrogs (Rana catesbeiana) come in contact with native amphibians on four continents and are well established in lowlands of western North America. To date, research on the effects of introduced bullfrogs on native frogs has focused on competition and predation, and is based largely on larval interactions. We present observations of interspecific amplexus between...

No abstract available.

Red brome [Bromus madritensis subsp. rubens (L.) Husn.] is a Mediterranean winter annual grass that has invaded Southwestern USA deserts. This study evaluated interactions among 13 Sonoran Desert annual species at four densities of red brome from 0 to the equivalent of 1200 plants m−2. We examined these interactions at low (3 μg) and high (537 μg NO3− g soil−1) nitrogen (N) to evaluate...

The Amphibian Research and Monitoring Initiative (ARMI) began in 2000 as an attempt by the United States Geological Survey to determine the status and trends of amphibians on federal lands in the United States and its territories. ARMI research focuses on determining causes of declines, if observed, developing new techniques to sample populations and analyze data, and disseminating...

No abstract available.