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Bog vegetation, which is dominated by Sphagnum mosses, depends exclusively on aerial deposition of mineral nutrients. We studied how the main mineral nutrients are distributed between intracellular and extracellular exchangeable fractions and along the vertical physiological gradient of shoot age in seven Sphagnum species occupying contrasting bog microhabitats. While the Sphagnum exchangeable cation content decreased generally in the order Ca2+ ? K+, Na+, Mg2+ > Al3+ > NH4+, intracellular element content decreased in the order N > K > Na, Mg, P, Ca, Al. Calcium occurred mainly in the exchangeable form while Mg, Na and particularly K, Al and N occurred inside cells. Hummock species with a higher cation exchange...
The long-term preservation of national park ecosystems requires scientific knowledge about populations, communities, and the ecological processes upon which sustainable ecosystems depend. Unfortunately, national parks in the United States have a well-documented history of indifference, if not hostility, to the support of basic research. Numerous external reviews have criticized the lack of institutional support for science, blaming it in large part on the traditional emphasis of the National Park Service (NPS) on scenery and tourism management. However, recent efforts to improve the support for science in the U.S. national parks have been most encouraging. These include a long-sought Congressional mandate to support...
Pulses of water availability characterize semiarid and arid ecosystems. Most precipitation events in these ecosystems are small (?10 mm), but can stimulate carbon flux. The large proportion of carbon stored belowground and small carbon inputs create the potential for these small precipitation events to have large effects on carbon cycling. Land-use change can modify these effects through alteration of the biota and soil resources. The goal of our research was to determine how small precipitation events (2, 5, and 10 mm) affected the dynamics of soil carbon flux and water loss in previously cultivated Conservation Reserve Program (CRP) fields and undisturbed shortgrass steppe. Total carbon loss and duration of elevated...