No abstract

Intensive monitoring of bird nests to measure reproductive success is time-consuming and may influence the fate of nests. Reproductive indices that do not require searching for and visiting nests may be reasonable alternatives to nest monitoring if they provide results similar to nest-searching efforts. We evaluated the reproductive index of Vickery et al. (1992) for estimating reproductive success of the dickcissel (Spiza americana) in northeast Kansas, USA. We used nest searching and Vickery et al.'s (1992) reproductive index to compare reproductive success on 20 plots (200 x 200 m). Daily nest survival (DNS) rates averaged 0.911 (SE = 0.011, n = 72 nests), and brownheaded cowbirds (Molothrus ater) accounted for 21% of all nest failures. Surveyors underestimated reproductive index ranks when compared to nest-searching efforts and were inaccurate in their assignment of reproductive success. In particular, surveyors reported successful nests on 3 study plots that fledged no young, probably because young dickcissels moved onto plots after fledging from their natal territories. Our results indicate that the reproductive index of Vickery et al. (1992) may be inappropriate for wary species or those heavily parasitized by brood parasites. We suggest that before relying on the index alone, investigators should use pilot trials to determine whether results from this index are concordant with results from intensive nest-searching efforts for species of interest.

Human activities, such as military off-road vehicular traffic, disturb ground and vegetation cover of landscapes and increase potential rainfall related runoff and soil erosion. On military lands, soil erosion is of major concern in order to sustain training lands and thus there is a need for land condition maps for planning training activities and land management. In this study, we presented a conditional co-simulation algorithm to generate annual time series maps of soil erosion status from 1989 to 2001 for an army installation. The spatial variability and temporal dynamics of land condition were analyzed. This algorithm modeled soil erosion as realizations of a random function by combining a set of permanent plot data and Landsat Thematic Mapper (TM) images. In addition to estimation maps of soil erosion status, we obtained the maps of uncertainties including the variance of each pixel estimate and the probability of poor land condition. The results and maps are useful tools for land managers and decision-makers to guide military training programs and to generate management plans for sustaining training lands.

Military training activities are known to impact individual species, yet our understanding of how such activities influence animal communities is limited. In this study, we used long-term data in a case study approach to examine the extent to which the local small landbird community differed between a site in northeast Kansas that experienced intensive disturbance from military training activities (Ft. Riley Military Installation) and a similar, nearby site that experienced minimal human disturbance (Konza Prairie Biological Station). In addition, we characterized how the regional pool of potential colonizers influenced local community dynamics using Breeding Bird Survey data. From 1991 to 2001, most species of small terrestrial landbirds (73%) recorded during breeding surveys were found at both sites and the mean annual richness at Ft. Riley (39.0 +/- 2.86 [SD]) was very similar to that of Konza Prairie (39.4 +/- 2.01). Richness was maintained at relatively constant levels despite compositional changes because colonizations compensated local extinctions at both sites. These dynamics were driven primarily by woodland species that exhibited stochastic losses and gains and were present at a low local and regional abundance. Our results suggest that military training activities may mimic natural disturbances for some species in this area because the small landbird community did not differ markedly between sites with and sites without extensive human disturbance. Although our results suggest that military training is not associated with large changes in the avian community, additional studies are needed to determine if this pattern is found in other ecological communities.

Grassland ecosystems evolved with natural disturbance events on multiple spatial scales in which focal, fine-scale soil disturbance by animals often was imbedded within large-scale grazing disturbance. The resulting plant communities adapted to both broad-scale and fine-scale disturbance that resulted in species-rich plant communities. These natural disturbance regimes have been largely replaced by anthropogenic disturbance. While we generally understand grassland response to modern grazing practices, we know much less about plant community response to soil disturbance imbedded within non-focal grazing. Therefore, we used a tracked vehicle to focally disturb soil in a North American mesic mixed prairie that was either undisturbed prairie or prairie with a recent history of disturbance from either grazing or haying. Successional trajectory and recovery time following focal soil disturbance was similar between grazed and hayed plant communities. Species composition did not differ (P \ 0.05) between grazed or hayed prairie and the respective undisturbed prairie. Plant species richness and bare ground increased (P \ 0.05) following focal soil disturbance in both grazed and hayed communities, but focal soil disturbance combined with either grazing or haying did not change either plant species richness or bare ground more than (P [ 0.05) focal soil disturbance alone. Also, the effect of focal soil disturbance was shortlived with recovery in two growing seasons. Our results suggest that anthropogenic focal soil disturbance is a reasonable mechanism to restore soil disturbance to the grassland ecosystem.