Stem flow is the water from precipitation that is intercepted by plant canopies and conveyed down the outside of stems to wet the soil at the base of the plant. For western juniper (Juniperus occidentalis Hook.) trees, stem flow was only a small fraction of the precipitation intercepted by the canopy. However, this moisture may be important in the nutrient flux of the trees. The first stem flow in the fall after the summer drought was enriched in nitrate-nitrogen although the quantity of nitrogen per unit area was small. The combination of favorable moisture and temperature conditions at the base of the tree leads to litter decay and nitrification. The root system of the trees had many fine roots in the area that received stem flow. Canopy interception and stem flow should be taken into consideration in application of soil active herbicides for control of western juniper.
Quadratic response surface analysis was applied to data of seed germination in relation to temperature. Analysis of these data is the comparing of several levels of quantitative factors. In such situations, multiple-comparison procedures, such as Duncan's multiple range test, are inappropriate. The data were the germination percentages of four species at 55 constant or alternating day and night temperature regimes. A quadratic response surface was developed for each species using multiple-regression techniques. Estimated germination values and their confidence limits were derived from the quadratic response surface of each species for each cold-period temperature through a series of warm-period temperatures. Many parameters were synthesized from the response surfaces to evaluate germination of the four species in relation to temperature. These comparisons form a statistically valid basis from which to select the most adapted plant species and predict the best time for planting or applying weed-control treatments.
Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker] is the dominant forage species on millions of hectares of rangeland in the western United States. Revegetation of degraded rangeland by seeding Indian ricegrass has been generally unsuccessful because of low seed germination. Our purpose was to evaluate the influence of acid seed scarification on germination of Indian ricegrass seeds. Seeds of ‘Paloma’ and ‘NezPar’ Indian ricegrass were scarified in sulfuric acid (H2SO4) from 0 through 45 min at 5‐min intervals. Without scarification, germination of the seeds of these two cultivars was less than 10%. Seedlots from 1 to 11 years old were treated. Germination data were used to develop regression equations for the relationship between duration of acid seed scarification and germination for each cultivar. Seeds of Paloma Indian ricegrass required 25 to 35 min of scarification, whereas seeds of NezPar required 15 to 25 min scarification. The relative composition and morphological forms of the seed may explain the difference in duration of required scarification. The scarified seeds were incubated at 55 constant and alternating temperatures to obtain data with which to construct quadratic response surfaces for temperature‐germination profiles. Even with scarification, the seeds of the two cultivars produced mean germination for the profiles of only 9 to 31%. The dormancy of Indian ricegrass seeds is controlled by complex interacting factors. Acid scarification is a very imprecise tool for enhancing the germination of dormant seeds of Indian ricegrass.
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