Abstract. Secondary succession reflects, at least in part, community assembly-the sequences of colonizations and extinctions. These processes in turn are expected to be sensitive to the size of the site undergoing assembly and its location relative to source pools. In this paper we describe patterns of succession over 18 years in an experimentally fragmented landscape created in eastern Kansas, USA, in 1984. The design of the experiment permits one to assess the influence of patch size and landscape position on successional dynamics. The general trajectory of succession follows that typical of succession in much of the eastern United States. In the initial years of the study, there was relatively little effect of patch size or distance to sources. Here we show that spatial effects in this system have become increasingly evident with time, as gauged both by repeated-measures ANOVA and ordination techniques. Woody plants have colonized more rapidly (per unit area) on large and nearby patches. Species richness at a local (within-quadrat) scale in general has increased, with slightly greater richness in large than in small patches later in the study. Temporal stability in community composition has generally been greater in large patches. Spatial heterogeneity in community composition has increased during succession, but with different patterns in large and small patches. This long-term experiment suggests that landscape structure influences many aspects of community structure and dynamics during succession, and that such effects become more pronounced with the passage of time.

Plant litter may play an important role in herbaceous plant communities by limiting primary production and influencing plant species richness. However, it is not known how the effect of litter interacts with fertilization. We tested for the role of litter and fertilization in a large-scale experiment to investigate effects on diversity and biomass of plant species, growth forms, native vs. non-native groups, and abiotic ecosystem components (e.g., soil moisture, PAR). We manipulated plant litter (removed vs. left in situ) and nutrient availability (NPK-fertilized vs. unfertilized) for 4 years in 314-m 2 plots, replicated six times, in an old-field grassland. While many of our species-level results supported previously published studies and theory, our plant group results generally did not. Specifically, grass species richness and forb biomass was not affected by either fertilization or plant litter. Moreover, plant litter removal significantly increased non-native plant species richness. Relative to native plant species, all of our experimental manipulations significantly increased both the biomass and the species richness of nonnative plant species. Thus, this grassland system was sensitive to management treatments through the facilitation of non-native plant species. We coupled biotic and abiotic components within a nonmetric multidimensional scaling (NMS) analysis to investigate treatment effects, which revealed that specific treatments altered ecosystem development. These results suggest that fertilization and plant litter may have larger impacts on plant communities and on ecosystem properties than previously understood, underscoring the need for larger-scale and longerterm experiments.

No abstract

Abstract. Recent studies of nutrient additions to terrestrial ecosystems have focused on the ''aerial'' portion of the food web associated with living plants. These studies showed nutrient loading increased arthropod abundance and biomass, but decreased diversity. However, none of these studies explicitly examined nutrient loading effects on epigeal arthropods. To test nutrient loading effects on epigeal spiders and on individual species within a temperate-latitude grassland community, we used pitfall traps to sample spiders for four years within 24 large (314 m 2 ) plots in which we manipulated nutrients (NPK fertilizer) and plant litter (litter removed or left in place). We measured the diversity, abundance, biomass, and community structure responses of the spider community, and of wolf spiders (Lycosidae) and linyphiid spiders (Linyphiidae), as well as the abundance and biomass responses of the six most common species. We hypothesized increased nutrient loading would increase epigeal spider abundance and biomass but decrease diversity. Contrary to predictions, spider species richness, diversity, and biomass were not significantly affected by fertilization, while fertilization resulted in significantly increased abundance. Also contrary to predictions, plant litter did not affect any of these variables. Linyphiid spiders had the strongest responses to fertilization, with significantly increased abundance and biomass, and, contrary to predictions, increased species richness in fertilized plots. Wolf spiders responded more closely to predictions. Our results indicate that the epigeal spider community does not respond as would be predicted by biodiversity-productivity theory. This underscores the need to integrate the largely detritus-based epigeal community into current biodiversity-productivity theory.

The lomechusine genus Myrmedonota Cameron is recorded from North America for the first time. Myrmedonota is diagnosed, and two new species, M. aidani Maruyama & Klimaszewski, sp. nov., and M. lewisi Maruyama & Klimaszewski, sp. nov., are described and illustrated. Bionomical information is provided for both new species.