Tallgrass prairie in the Flint Hills region of Kansas is characterized by considerable topographic relief coupled with variation in soil properties. These topoedaphic gradients, together with variation in fire regimes, result in temporal and landscape‐level variability in soil resource availability and plant responses. Nitrogen usually is considered to be the nutrient most limiting to primary productivity in tallgrass prairie, but few studies have addressed how N availability varies seasonally, or across the landscape and with fire frequency. We measured soil inorganic N, in situ net N mineralization, aboveground net primary productivity (ANPP), and N mass on plots either fertilized with N in 1993 or in 1994, or unfertilized, in uplands and lowlands of two annually burned and two long‐term unburned sites during the 1994 growing season. In addition, our study was conducted in the year following record rainfall, allowing us to assess the potential for high precipitation amounts to affect subsequent N cycling and plant production. Both fire treatment and topography affected soil N availability. In general, N mineralization was greater on unburned than on burned sites and was up to five times greater on uplands than lowlands. Total extractable soil N was highest early in the season and least at midseason, and it also tended to be higher in unburned sites than burned sites on unfertilized plots. Added N increased ANPP, but there were no differences between plots fertilized in 1994 and those fertilized in 1993. In general, patterns of ANPP on control plots were consistent with known production responses to topography and burning (higher in annually burned sites and in lowland sites) but were inversely related or unrelated to patterns of N availability (higher in unburned sites and at upland topographic positions). Potential loss of N by volatilization during spring burning was greater than in years with normal rainfall amounts and represented a significant portion of aboveground plant N mass. Potential N losses did not appear to limit ANPP or N availability in the current growing season. Our results suggest that different factors control soil N mineralization and plant productivity, which explains, in part, why patterns of ANPP are not well correlated with patterns of N availability in tallgrass prairie ecosystems.

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This study evaluated germination and establishment characteristics of native legumes, which may hold potential for development as water-efficient cover crops in Kansas. Twenty-three species were subjected to hot water scarification, cold-moist stratification, and no pretreatment and allowed to germinate on moist filter paper under ambient laboratory conditions for 16 days. In the field, 1 m 2 plots were planted with 1.1 grams of seed of each of 23 native species and five introduced species at three planting dates, two in the fall and one in early spring. Seedlings were counted in late June. The effect of seed treatment on germination in the lab was highly species dependent. Hot water scarification had positive (4 species), neutral (16 species), or negative (3 species) effects on early germination (day 2), though fewer differences were seen on day 16. Stratification rarely had significant negative consequences and also affected both the rate and total amount of germination. Both species and planting date had significant effects on establishment in field plots. Establishment of all species was most successful with spring planting. Because of extremely dry conditions, this trend could be attributable to moisture availability. Though these results are preliminary, the lack of germination inhibition and successful establishment of some of the species in the field indicates that this is Rita J. Schartz is affiliated with the a promising direction of future research for new cover crops for harsh conditions. [Article copies available for a fee from The Haworth Document Delivery Service: