Establishment of seedlings of big sagebrush subsequent to range weed control treatments limits the economic feasibility of such treatments for increased forage production. This study investigated the dynamics of seed production by this species as one step in understanding seedling establishment. Studies were conducted on five different ecological sites along the arid extremity of big sagebrush distribution in western Nevada. Demography, physical dimensional parameters, biomass, and community structure were determined for each site and related to seed production over a 4-yr period. In addition, seeds harvested from each site were used to grow plants that were transplanted to establish reciprocal gardens at all sites. Seeds were subsequently harvested from the plants in these gardens. The average stand studied was capable of producing about 50 million seeds/ha annually. The plant characteristics most closely correlated with seed production were leaf weight, canopy density, and root crown diameter. The stand that consistently had the highest average seed production had the lowest woody biomass accumulation rate. In reciprocal gardens, plants grown from this stand had the highest average seed production. Seed production of big sagebrush plants appears to be related to site characteristics, shrub biomass characteristics, and inherent genetic potential of the plants in a given collection.

The cohesion of the arthropod community associated with the rain forest tree Argyrodendron actinophyllum was studied in a warm subtropical rain forest in Australia. The distribution of most arthropods was contagious on the foliage of A. actinophyllum. Chewers and phloem-feeders were more clumped than epiphyte grazers and parasitoids. Arthropod predator-prey ratios were high and relatively constant over time, as revealed by measures of their activity. However, similar ratios in abundance and species-richness of arthropods foraging on foliage showed high variability in space and no consistent trends. Species associations on the foliage were difficult to predict and did not constitute either a single, well-united community or well-delimited subcommunitics. Most of the data suggest that on the foliage of A. actinophyllum, the cohesion of the arthropod community is not extremely strong. Apart from methodological constraints, possible reasons for this include the influence of host-tree phenology, and the high arthropod-diversity of the rain forest environment.