A Simulation Study to Assess the Sensitivity of a Forest Health Monitoring Network to Outbreaks of Defoliating Insects

The sensitivity of the United States Forest Health Monitoring network to outbreaks of defoliating insects was examined by means of a simulation study. A model constructed specifically for the study was used to generate a wide variety of defoliation patterns in forested landscapes. Forest configuration was that of Minnesota, USA, as expressed by the GAP land cover classification. Combinations of model parameters were based on a Latin Hypercube sample. The relationship between the average number of plots defoliated and outbreak characteristics was then examined via multiple regression. Both theoretical and model results pointed to a strong, linear relationship between the average number of plots defoliated and outbreak size. Model results provided additional insight, suggesting a significant relationship between the average number of plots defoliated and other outbreak characteristics after outbreak size was taken into account.     

Some effects of acidic growing conditions on three emergent macrophytes: Zizania aquatica, Leersia oryzoides and Peltandra virginica

Transplants of Zizania aquatica L., Leersia oryzoides (L.) Shwartz, and Peltandra virginica (L.) Schott and Endl. were grown for ten weeks in simulated marsh conditions under acidic (pH 3.0, pH 4.0) treatment regimes and compared with controls (pH 5.6). Mortality was low in all treatments and nearly all plants of Z. aquatica and L. oryzoides flowered. Under acidic conditions, transplant height and root biomass of Z. aquatica were significantly reduced, with greater culm numbers and total lengths of inflorescences per flowering plant compared to controls. Shoot biomass of L. oryzoides transplants was significantly greater in the most acidic treatment (pH 3.0). Transplants of P. virginica grew slowly and did not flower during the experiment; heights and shoot biomass of P. virginica were significantly reduced with increased leaf chlorosis in acidic conditions.