With the proliferation of old fields and the decline of native grasslands in North America, non-indigenous grasses, which tend to colonize and dominate North American old fields, have become progressively more abundant. These new grasses can differ from native grasses in a number of ways, including root and shoot morphology (e.g., density of root mat, height of shoots), growth phenology (e.g., cool season vs. warm season growth), and plant-soil-water relations due to differences in photosynthetic physiology (C 3 vs. C 4 ). Woody plants have been slow to colonize some old fields in the prairie-forest border area of North America and it is hypothesized that non-indigenous grasses may be contributing to the poor establishment success of woody plants in this region, possibly through more intense competition for resources. To test this hypothesis, a multi-factorial field experiment was conducted in which water, nitrogen, and grass functional group (non-indigenous C 3 and native C 4 species) were manipulated in a study of survival of oak seedlings. The grass type variously affected some of the different growth measurements, however, the effects of grass type on seedling growth were small compared to the effects on seedling survival. The results showed that when grown under dry conditions, seedlings growing in non-indigenous grasses experienced up to a 50% reduction in survival compared to those growing in native grasses under the same conditions. Analyses of root and shoot competition showed that the cause for the reduced survival in the non-indigenous grasses was due primarily to underground processes. The findings confirmed our initial hypothesis that nonindigenous grasses are likely contributing to the poor establishment success of woody plants in these old fields. However, the explanation for the reduced oak seedling survival in non-indigenous grasses does not appear to be due to reduced resource availability since soil water levels did not differ between nonindigenous and native grass plots and other resource levels measured (light, NO 3 , and NH 4 ) were higher in non-indigenous grass plots under dry conditions. An alternative explanation is that the non-indigenous grasses modify the soil environment in ways that, under dry conditions, are deleterious to emerging oak seedlings. Since current climate projections for the upper Midwest are for hotter and drier summers, the results suggest that the resistance of these old fields to oak encroachment will likely increase in the future.

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Objective Current practice guidelines do not recommend benzodiazepines for acute management of anxiety disorders in pediatric patients. However, in procedural settings, benzodiazepines are commonly used to relieve acute pre-procedural stress. This meta-analysis examines the efficacy and tolerability of benzodiazepines as short-term anxiolytics in children. Method PubMed was searched for randomized controlled trials assessing the efficacy of benzodiazepines as short-term anxiolytics in pediatric patients. Twenty-one trials involving a total of 1,416 participants were included. A fixed effects model was used to examine the standardized mean difference of improvement in anxiety levels compared to control conditions. In stratified subgroup and meta-regression, the effect of the specific agent, dose, timing, and setting of benzodiazepine treatment was examined. Results A significant benefit was seen for benzodiazepines compared to control (standardized mean difference = 0.71 [95% confidence interval, 0.60–0.82], k = 24, z = 12.7, p<0.001). There was also funnel plot asymmetry in this meta-analysis, suggesting some evidence of publication bias. Moderator analyses found that when benzodiazepines were used in dental or non-operating room procedures, they were more effective than when they were used in operating room procedures (test for subgroup differences Q2 = 6.34, p=0.04). Tolerability analysis revealed there was no significant difference in the risk of developing irritability or behavioral changes between benzodiazepine and control groups. Conclusions Benzodiazepines are effective and well-tolerated when used as short-term anxiolytics in procedural settings for pediatric patients. Further research is needed to determine whether benzodiazepines are effective in pediatric anxiety disorders.