Time-course growth chamber studies were conducted on little mallow
(Malva parviflora L.) to determine whether sublethal doses of lactofen
(1'-(carboethoxy)ethyl-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-
nitrobenzoate) would enhance uptake of glyphosate (N'-(phosphonomethyl)
glycine) by altering membrane permeability. Lactofen-induced membrane
peroxidation was determined by harvesting leaf discs, measuring stress
ethylene evolution, and recording increases in...
Field, screenhouse, and laboratory experiments were conducted to
study weed interference in rice grown on hydromorphic soils at the
International Institute of Tropical Agriculture (IITA) at Ibadan, Nigeria.
Rice and weeds emerged at the same time, 1 week after planting.
Weed dry weight was significantly reduced when the crop was...
Water potential, leaf conductance, growth, nitrogen
content, and seedling survival of Wyoming Big Sagebrush
(Artemisia tridentata ssp. wyomingensis) following
defoliation of the herbaceous understory were assessed
during two growing seasons. Precipitation was 107% and 63%
of the long-term mean (283 mm) in 1989 and 1990,
respectively, which presented an opportunity...
In the Northwest Great Basin, aspen (Populus tremuloides) communities uniquely contribute to the biodiversity of a semi-arid, sagebrush-dominated landscape. In this same region, western juniper (Juniperus occidentalis) is encroaching into aspen stands. This study determined the timing, extent, and some of the effects of this expansion. Aspen stands below 2,133...
Transition matrix models are one of the most widely used tools for assessing population viability. The technique allows inclusion of environmental variability, thereby permitting estimation of probabilistic events, such as extinction. However, few studies use the technique to compare the effects of management treatments on population viability, and fewer still...
Dry coniferous forests in the western United States are experiencing severe wildfires, insect outbreaks, forest disease epidemics and a growing presence of invasive species. Policies strongly emphasize reducing hazardous fuels at the Wildland Urban Interface (WUI) where communities and forests intersect. However, these areas present restoration challenges as they tend...
Computer simulations and experiments were used to determine
the basis for skewness and inequality in size structures
(frequency distributions of Individual plant sizes) prior to
self-thinning mortality. In simulated stands, density-dependent
neighborhood heterogeneity caused variability in the growth rate
of individuals with the same size, and such variability caused
skewness...
Two research questions are posed: (1) How have ecosystem conditions changed through time in southwestern Oregon? (2) How have culture-driven and climate-driven processes contributed to ecosystem change in southwestern Oregon? A brief introduction to the Little River study area is followed by a cultural and ecological history of the watershed....
The relationship between annual foliage production and nitrogen and water stress was examined in 14 naturally regenerated, mid-rotation ponderosa pine stands in central Oregon. Current-year and older foliage masses, and foliage nitrogen contents and concentration were estimated from 132 destructively sampled trees. Litterfall mass and nitrogen retranslocation rates from senescing...