Information on the yield of grasses as the plants mature is useful to optimize grazing potential and quality hay production. The objectives of this study were to compare the yield and feeding value of 11 common prairie grasses over 2 yearly cycles of growth and determine which of the grasses may require supplementation to meet nutrient requirements of grazing cattle. Dry matter yield (DM), crude protein (CP), acid detergent fiber (ADF), calcium (Ca), and phosphorus (P) values were obtained for brome (Bromus inermis [L.]), creeping red fescue (Festuca rubra [L.]), crested wheatgrass (Agropyron cristatum [L.] Gaertn), intermediate wheatgrass (Agropyron intermedium (host) Beauv), meadow foxtail (Alopecurus pratensis [L.]), orchardgrass (Dactylis glomerata [L.]), pubescent wheatgrass (Agropyron trichophorum Link. richt), streambank wheatgrass (Agropyron riparium Scriba &Smith), slender wheatgrass (Agropyron trachycaulum Link Malte), tall fescue (Festuca arundinacea Schreb), and timothy (Phleum pratense [L.]) at weekly intervals from June to September, in 1992 and 1993. Most grasses reached maximum yields at week 8 in 1992 (drought year) and week 12 in 1993 (normal year). Herbage mass yields (g/0.25m2 at week 8 in 1992 (highest to lowest yielding) were crested wheatgrass (235), intermediate wheatgrass(210), pubescent wheatgrass(173), brome(161), slender wheatgrass(152), meadow foxtail(114), Tall fescue(110), timothy(101), orchardgrass(83), creeping red fescue(56), and streambank wheatgrass(50). Herbage mass yields pattern of the grasses in 1993 was similar to that in 1992 except for crested wheatgrass and brome which ranked first and fourth in 1992 but ranked fifth and second, in 1993, respectively. Quality declined in all grasses as they matured. The average CP content of grasses declined from 24% to 13% in 1992 and from 21.5% to 12.1% in 1993 but were adequate to meet crude protein requirements of growing, pregnant or lactating grazing cattle. The Ca levels in all grasses were adequate for all classes of cattle on pasture but the low P levels of 0.11% in both years indicate that growing, pregnant or lactating cattle grazing on these pastures would require P supplementation.

White-tailed deer (Odocoileus virginianus Zimm.) appear to concentrate foraging activity along the perimeters of warm-season food plots. Because of this, we tested the hypothesis that (1) providing travel lanes (i.e., rows not planted) free of vegetation within food plots will increase deer use of the plots and result in an equal spatial distribution of forage use within the plots, and (2) skip-row planting will result in increased yield and survival of lablab (Dolichos Lablab L.), an annual legume. During 1994 and 1995, lablab was established by planting (1) every row spaced 0.9 m apart (solid), (2) 2 rows and not planting 1 row (skip 1), and (3) 2 rows and not planting 2 rows (skip 2) in two 5-ha food plots. Planting scheme did not affect spatial patterns of food plot use by deer. Utilization was concentrated at food plot perimeters on 9 of 15 sampling dates. Food plot utilization by deer was greater in skip 2 treatments only during August 1995, possibly as a result of greater forage availability resulting from greater plant survival than solid rows. Deer foraging in food plots apparently shifted foraging activities to an area of greater forage availability as the resource supply was depleted. Skip-row planting had lower overall planting costs/ha than solid planting but maintained similar forage production per hectare.

The objective of many laboratory-germination experiments is to develop insight into the process of field establishment. It is relatively difficult, however, to infer potential field response from laboratory data given the enormous spatial and temporal variability in seedbed microclimate. Previous studies have attempted to survey large numbers of alternating day/night temperature regimes in order to estimate germination response to potential conditions of field microclimate. The objectives of this study were to estimate the errors associated with prediction of variable-temperature germination response from fewer, constant-temperature germination data. Non-dormant seeds of thickspike wheatgrass [Elymus lanceolatus (Scribn. and J.G. Smith) Gould], bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Love], Sandberg bluegrass (Poa sandbergii Vasey), and bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey] were germinated under constant, alternating-constant and sine-wave temperature regimes. Predicted and measured cumulative-germination response generally coincided to within a day for most temperature treatments except for the most slowly germinating subpopulations of seeds. Thermal response models can be parameterized from relatively few experimental data but provide predictive inferences relevant to a wide number of variable-temperature conditions.

The objective of this study was to compare intermediate wheatgrass establishment at 4 seeding rates, in combination with tillage and/or glyphosate (n-phosphomethyl glyine), in spotted knapweed infested rangeland. We hypothesized that the establishment of intermediate wheatgrass seedlings would be greatest at high seeding rates, while spotted knapweed density and biomass would be negatively impacted by intermediate wheatgrass densities. Glyphosate (1.16 liters a.i./ha; with and without), tillage (200 mm depth; with and without), and 4 seeding rates (0, 500, 2,500, 12,500 m-2) of intermediate wheatgrass seeds were factorially arranged in a randomized-complete-block design with 4 blocks at each of 2 sites in Montana. Treatments were applied in the fall of 1995. By the second growing season, intermediate wheatgrass failed to established in plots seeded with 500 seeds m-2, the currently recommended seeding rate. Increasing the seeding rate to 2,500 and 12,500 m-2 increased intermediate wheatgrass tiller density by 80 and 140 plants m-2, respectively, at Hamilton and 158 and 710 plants m-2, respectively, at Bozeman. At the highest seeding rate, combining tillage with glyphosate increased tiller density over 3 times more than other treatments where intermediate wheatgrass successfully established at Hamilton. However, neither tillage nor glyphosate affected intermediate wheatgrass density at Bozeman by the second growing season. In the first season, seeding rates of 0, 500, 2,500, 12,500 m-2 produced 214, 208, 176, and 114 knapweed plants m-2, respectively (LSD0.05 = 36.1) at Bozeman, but had no effect at Hamilton. Our revegetation study suggests that increasing intermediate wheatgrass seeding rates can facilitate their establishment in spotted knapweed infested rangeland. Using high seeding rates to control spotted knapweed and increase seedling establishment may enhance our ability to use revegetation as an effective weed management strategy.

Despite the importance of soil characteristics for classifying riparian ecosystem types and evaluating ecosystem or range condition, little information exists on western riparian area soils or the factors that influence them. We examined the effects of drainage basin geology and water table depth on soil morphology and soil physical and chemical properties of meadow sites in central Nevada. We described and analyzed the soils of meadows that occurred in 4 drainages with different geology and that exhibited high water tables (0 to -20 cm from the surface), intermediate water tables (-30 to -50 cm), and low water tables (-60 to -80 cm). Pedons of high water tables sites had thick Oe horizons, dark, fine-textured A horizons, no B horizons, and lower C horizons high in coarse fragments. In contrast, pedons of low water tables sites were characterized by deep, dark and organic-rich A horizons, cambic B horizons, and deep rooting profiles. High water tables sites had higher organic matter, total nitrogen, cation exchange capacity, and extractable potassium, but lower pH than low water table sites. Also, high water table sites had lower percentage sand, lower bulk densities, and higher soil moisture retention. The importance of organic matter was evidenced by strong positive product moment correlations for organic matter and total nitrogen, cation exchange capacity, and extractable potassium. Significant differences in pH, extractable potassium and extractable phosphorus existed among drainages that were explainable largely from the parent materials. Drainages with chert, quartzite, and limestone had higher silt and clay, neutral pH, and high levels of extractable phosphorus. Drainages formed in acidic volcanic tuffs, rhyolites and breccia were characterized by coarser textured soils and low pH and extractable phosphorus. In riparian areas, soil water table depth interacts with soil parent material to significantly affect soil morphology and soil physical and chemical properties. Because these factors vary over both large and small spatial scales, differences among sites must be carefully interpreted when classifying ecosystems or evaluating ecosystem condition.

Aerial photos in Alberta are generally acquired according to topographic mapping and forestry specifications. The parameters for interpreting rangeland vegetation, such as silver sagebrush (Artemisia cana-Pursch), need to be explored and condensed into an operational specification. Five aerial films and 3 solar angles were evaluated by 7 photo interpreters to determine the optimal conditions for interpreting silver sagebrush at a scale of 1:20,000. Interpreter accuracy and preference are determined for the 2 experimental conditions as to determine operational specifications. Kodak Panatomic-X 2412 achieved the highest interpretation accuracies for silver sagebrush cover detection and plant density estimation (91.0% and 94.4% respectively), while Kodak Aerochrome Infrared 2443 and Agfa Avicolor H100 performed best for estimating plant vigor (92.7% and 93.7% respectively). Photo interpreters also chose Kodak Panatomic-X 2412 as the preferred film for interpreting silver sagebrush (7.7 on a scale of 10). Positive correlations were obtained between combinations of interpretation accuracy, interpreter film preference and photographic density range measurements, indicating the trends for higher accuracy and preference are associated with higher density ranges. Solar angles of 20 degrees, 37 degrees and 54 degrees were evaluated by photo interpreters with significant preference shown for 20(.). Recommendations for modifying Alberta's air photo operational specifications to include high resolution (Kodak Panatomic-X) imagery and decreasing the acceptable lower boundary for the operational solar angle from 30 to 20 degrees for interpreting silver sagebrush at the 1:20000 scale are proposed.

Net carbon exchange of terrestrial ecosystems will likely change as atmospheric CO2 concentration increases. Currently, little is known of the annual dynamics or magnitude of CO2 flux on many native and agricultural ecosystems. Remoteness of many ecosystems has limited our ability to measure CO2 flux on undisturbed vegetation. Today, many plant ecologists have portable photosynthesis systems with which they make single-leaf photosynthesis measurements. Utility of this equipment is enhanced when canopy-level CO2 flux is also measured. We designed a portable 1-m3 closed chamber for use in measuring CO2 exchange in short statured vegetation with widely varied canopy structure. The design includes external ductwork equipped with doors which are used to open the chamber for ventilation with outside air between measurements. The chamber was tested on a Wyoming big sagebrush (Artemisia tridentata ssp. Wyomingensis Nutt.)/Thurber's needlegrass (Stipa thurberiana Piper) community using 10 plots equally divided between shrub and interspace. The ductwork and doors provided adequate ventilation to allow consecutive measurements of CO2 flux without removing the chamber from the plot. The chamber could differentiate CO2 flux between plots with sagebrush and those with grass only, even at relatively low fluxes. Net CO2 uptake per unit ground area was greater (P = 0.04) on sagebrush-grass plots (7.6 +/- 1.4 micromoles m-2 s-1) than on interspace plots without sagebrush (3.1 +/- 1.0 micromole m-2 s-1). Chamber and leaf temperature increased by an average of 0.5 and 1.2 degrees C, respectively, during measurements.