Treesearch

Net CO(2) uptake in full sunlight, total leaf area (TLA), projected leaf area of detached leaves (PLA), and the silhouette area of attached leaves in their natural orientation to the sun at midday on June 1 (SLA) were measured for sun shoots of six conifer species. Among species, TLA/SLA ranged between 5.2 and 10.0 (x bar = 7.3), TLA/PLA ranged between 2.5 and 2.9 (x bar = 2.7) and PLA/SLA ranged between 2.0 and 3.7 (x bar = 2.2). These ratios were reflected in the ratios of net photosynthesis computed on the basis of the three measures of leaf area. The much smaller values for TLA/PLA...

We estimated the yearly snow accumulation to the Glacier Lakes Ecosystems Experiments Site (GLEES) for the winters of 1987-88, 1988-89, and 1989-90, using a simple degree-day model developed by J. Martinec and A. Rango. Comparisons with other data indicate that the estimates are accurate. In particular, a calibration with an intensive snow core-probe survey in 1989-90 agrees within the probable error of the survey, which was ± 6%.

Measurements of CO2 near the snow-soil interface showed elevated concentrations up to 2120 ppmv. Concentrations greater than 1700 ppmv were observed 0.45 m above the snowsoil interface. The increase in CO2 concentrations in the snow coincided with the beginning of melt. Measurements of the pH and alkalinity of the meltwater from the base of the snowpack were consistent with the measured CO2 levels. Decreases in pH at constant alkalinity of up to 0.8 units were associated with the excess CO2. The origin of the excess CO2 is uncertain but may be related to litter decomposition. Elevated...

To describe conditions in natural redds of steelhead trout (Oncorhynchus mykiss), we evaluated the particle size distribution of egg pockets, redd pits and tailspills, artificially constructed redds, and undisturbed substrate outside redds. Egg pockets were located in upper strata an average of 14.9 cm below the substrate surface. Egg pockets contained fewer fines (

Water potential was measured in five ponderosa pine (Pinus ponderosa Laws.) in each of four stands of different growing-stock levels at two locations in the Black Hills of South Dakota. Mean water potentials at dawn and midday varied significantly among growing-stock levels at one location, but differences were not consistent. Mean dawn and midday water potentials within growing-stock levels significantly decreased during the summer but showed minor increases during the overall decline. Stress levels were considered high enough to influence physiological functioning and, therefore,...

Bark temperatures on the north and south sides of five ponderosa pines (Pinus ponderosa Laws.) in each of four growing stock levels in two areas in the Black Hills of South Dakota were monitored periodically from May through August 1989. Temperatures were significantly different among growing stock levels and between sides of the tree. The magnitude of differences between the mean bark temperatures in partially cut stands and uncut controls was inversely related to stocking level. Maximum differences in mean bark temperatures among the growing stock levels occurred between 10:00 and 14:00,...

Concerns increase about the effects of emissions from biomass burning on global climate. While the burning of biomass constitutes a large fraction of world emissions, there are insufficient data on the combustion efficiency, emission factors, and trace gases produced in these fires, and on how these factors depend on the highly variable chemistry and burning condition of the fuel. Measurements made by satellites or aircraft can be used to estimate areas burned or ratios of specific emissions, but measurements close to the ground are needed to estimate actual amounts of fuel consumed, the...

Biomass burning on a global scale injects a substantial quantity of gaseous and particulate matter emissions into the troposphere. Some of these combustion products are known to accumulate in the atmosphere and are implicated in observed changes in tropospheric composition and chemistry. The practice of open burning of biomass has come under close examination as a result of its pollution potential. In the United States, most biomass burning is managed in order to limit pollutant release. Recently, it has been inferred that biomass burning may produce a net increase in the concentration of...

Emissions of trace gases and particulate matter from burning of biomass are generally factored into global climate models. Models for improving the estimates of the global annual release of emissions from biomass fires are presented. Estimates of total biomass consumed on a global basis range from 2 to 10 Pg (1 petagram = 1015 g) per year. New data are now available for emission factors for a range of vegetation types and burning conditions for the tropical, mid-latitude, and boreal forest regions. We estimate the total emissions of CO, CO2, CH4, non-methane hydrocarbons (NMHC), and...

Fire affects nutrient cycling and the physical, chemical, and biological properties of soils occupied by western montane forests. Combustion of litter and soil organic matter (OM) increases the availability of some nutrients, although others are volatilized (for example, N, P, S). Soil OM loss also affects cation exchange capacity, organic chelation, aggregate stability, macro pore space, infiltration, and soil microorganisms. Nitrogen replenishment must be emphasized when prescribed burning programs are planned or during rehabilitation following wildfires.