Understanding the ecological processes that foster invasion and dominance by medusahead is central to its management. The objectives of this study were (1) to quantify and compare interference between medusahead and squirreltail under different concentrations of soil nitrogen (N) and phosphorous (P) and (2) to compare growth rates of medusahead and squirreltail under field soil N and P availabilities. We grew medusahead and squirreltail in an addition series in a greenhouse and applied one of four nutrient treatments weekly: (1) low N low P (no N or P added), (2) low N high P (added 250 ml of 600 µM P solution in the form of calcium phosphate), (3) high N low P (added 250 ml of 8,400 µM N solution in the forms of calcium nitrate and potassium nitrate), and (4) high N high P (added solutions as listed above for high N and high P). After 70 d density and biomass by species were sampled. We also grew individual medusahead and squirreltail plants in control soil conditions. Biomass, leaf area, and root length were determined for each species at 14-d intervals over 72 d. Regression models for medusahead and squirreltail suggested N appeared to be playing a much larger role than P in interference between the species. The high N treatment did not increase medusahead's interference ability relative to squirreltail as we had hypothesized. Medusahead typically imposed a two-to-seven-times stronger influence on interference relationships than squirreltail. Medusahead accumulated biomass, leaf area, and root length twice as fast as squirreltail. Results from our study suggest that medusahead seedlings will likely dominate over squirreltail seedlings. To restore squirreltail to medusahead-infested rangeland, medusahead densities should be reduced with integrated weed management strategies. On medusahead-free rangeland, prevention and early detection and eradication programs are critical.
PositionThe Intermountain Society of American Foresters promotes management of PinyonJuniper 1 (PJ) forests and woodlands for a variety of resource benefits. In some cases it will mean managing pinyon and juniper ecosystems for sustained woodland habitat and products where these species are the persistent and dominant vegetation type. In some cases this will mean removal of pinyon and juniper to favor other vegetation types where PJ has expanded into other ecotypes. In many cases it will mean managing for a mosaic of vegetation types and stand densities within the same watershed.Appropriate forest management and sound silvicultural tools should be used in PJ ecosystems to manage and sustain such systems in a healthy ecological condition while providing many values and benefits.Management goals for PJ forests and woodlands vary and are determined through a variety of land management planning processes for private, state and federally owned lands.Land managers are responsible for selecting appropriate, site-specific practices to accomplish the desired conditions. Professional foresters have experience and research to support effective use of silvicultural practices in PJ ecosystems. Skillful use of silvicultural practices, carefully attuned to the desires and needs of the landowner and to the ecology of the site, can more rapidly achieve and better maintain desired resource conditions with greater assurance of success than will acceptance of un-managed processes of change.Foresters must have the support of decision-makers to use silvicultural practices to improve ecological conditions and to manage vegetation for a variety of goals, including when hazardous fuel build-up poses risks to landscapes. Land managers are expected and encouraged to use professional knowledge, experience, and judgment to improve the health, productivity, and condition of PJ ecosystems for the benefit of humans, wildlife, and the health of the land for today and for future generations. 1 The PJ cover type, its distribution, and the species that compose it are described by Larson, Forest Cover Type 239, Pinyon-Juniper, pages 116-117 in Eyre, 1980.
Juniper (Juniperus spp.) encroachment into sagebrush (Artemisia spp.)-bunchgrass communities has reduced understory cover on millions of hectares of semiarid rangelands. Mechanical masticators shred trees to restore desirable vegetation and reduce the potential for catastrophic wildfire. Mechanical mastication where juniper density is high and perennial grass cover is low brings a risk of invasive weed dominance unless perennial species are established. To determine whether juniper mastication favors annual-or perennial-grass establishment, we compared seedling emergence, tillers, and aboveground biomass of cheatgrass (Bromus tectorum L.) and Anatone bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve). Comparisons were made among hand-planted rows between and under juniper canopies of masticated and adjacent untreated control areas at three locations in Utah. Bluebunch wheatgrass had 16% (95% CI: 11-21) and cheatgrass had 10% (95% CI: 5-15) fewer seedlings emerge per row in masticated than untreated areas (P , 0.001). However, bluebunch wheatgrass had 3.2 (95% CI: 2.0-5.2) times more tillers and 1.9 (95% CI: 1.6-2.2) times more aboveground biomass per row in masticated than untreated areas (P , 0.001). Similarly, cheatgrass had 2.3 (95% CI: 1.5-3.8) times more tillers, 2.0 (95% CI: 1.7-2.4) times more aboveground biomass, and 11.4 (95% CI: 6.3-20.7) times more spikelets per row in masticated than untreated areas (P , 0.001). This increased seedling growth in masticated areas was associated with increased inorganic nitrogen and soil water compared to untreated areas. Because mastication improves the growth of both cheatgrass and bluebunch wheatgrass seedlings, it could support dominance by either annual-or perennial-life forms. To avoid cheatgrass dominance where perennial understory cover is limited and cheatgrass propagule pressure is high, mastication should be accompanied by seeding desirable perennial species such as Anatone bluebunch wheatgrass.
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