Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Projets de développement → Projets de recherche pour le Développement → 2001 → DIFFUSE KNAPWEED (CENTAUREA DIFFUSA LAM.) INVASION ECOLOGY : ESTABLISHMENT, COMPETITION AND INTERACTIONS WITH THE NATIVE SOIL COMMUNITY

United States Department of Agriculture (USDA) 2001

DIFFUSE KNAPWEED (CENTAUREA DIFFUSA LAM.) INVASION ECOLOGY : ESTABLISHMENT, COMPETITION AND INTERACTIONS WITH THE NATIVE SOIL COMMUNITY

Knapweed Invasion Native

United States Department of Agriculture (USDA) Research, Education & Economics Information System (REEIS)

Titre : DIFFUSE KNAPWEED (CENTAUREA DIFFUSA LAM.) INVASION ECOLOGY : ESTABLISHMENT, COMPETITION AND INTERACTIONS WITH THE NATIVE SOIL COMMUNITY

Identification : COL00160

Pays : Etats Unis

Durée : Nov 1, 2001 à Jun 30, 2004

Domaine : Management of Range Resources ; Microorganisms, general/other ; Rangelands and grasslands, general

Partenaire : COLORADO STATE UNIVERSITY FORT COLLINS,CO 80523

Objectifs
The proposed research will be conducted to evaluate conditions under which the selected rangeland system either resists, or is susceptible to diffuse knapweed invasion. Achievement of the following objectives will provide information related to three components of diffuse knapweed ecology. First, this research will begin to define safe sites for diffuse knapweed emergence and establishment. Second, it will indicate whether or not disturbances that incorporate knapweed seed into the soil and/or reduce competition from established native vegetation are required for diffuse knapweed invasion of a semi-arid, foothills rangeland site. Finally, completion of the proposed research will provide information regarding the role of the soil community in knapweed invasion. The objectives of the proposed research are : 1.Determine the resistance of late-seral, undisturbed, semi-arid rangelands to diffuse knapweed invasion. 2.Determine how the removal of established, native vegetation, method of seeding and gap type affect seedling emergence and establishment of diffuse knapweed in a late-seral, semi-arid rangeland. 3.Quantify and compare the relative benefit that selected native plants and two species of exotic knapweeds derive from the native soil community in terms of germination and productivity. 4.Determine whether or not diffuse and spotted knapweeds maintain conditions in the soil community that preclude the establishment of native plants and promote regeneration of knapweed.

Descriptif
The first two objectives will be addressed by planting diffuse knapweed seed into a late-seral, native rangeland under combinations of treatment factors that alter ; 1) the location of the seed relative to established native plants (gap type), 2) competition from native vegetation, and 3) knapweed seed incorporation. The experimental design will be a factorial arrangement of three gap types (none, 5 cm, and 15 cm), two levels of native dominants (live and killed) and two levels of knapweed seeding (incorporated and not incorporated). This design will yield 12 treatment groups (3x2x2). Two hundred and forty diffuse knapweed establishment points will be randomly located along 20 transects in each of three blocks (720 establishment points total). Each establishment point will be randomly assigned to combinations of the twelve treatment groups, two runs (fall and spring), 10 transects, and 3 locations (12 treatments x 2 runs x 10 transects/run x 3 locations = 720 points). Ten-centimeter diameter rings centered at each establishment point will be used as markers. Treatments consist of all possible combinations of gap type (live bunchgrass, 5 cm diameter gap and 15 cm gap), presence/absence of established native vegetation (no glyphosate and glyphosate applied) and knapweed seed incorporation (incorporated, not incorporated). All treatments will be seeded to diffuse knapweed. Knapweed seed will be sown using two different methods. One method will involve dropping the seed from the air immediately over the establishment point, and leaving it where it falls without ensuring seed-to-soil contact. The other method will involve careful removal of litter or any other objects that would prevent seed contact with the soil, pressing the seed firmly into the soil and covering with approximately 5 mm of mineral soil. Diffuse knapweed will be planted in early fall, 2001 and again in early spring, 2002. The response variables measured in this study will include diffuse knapweed seedling emergence and seedling establishment. Greenhouse experiments will be conducted with container-grown plants of diffuse and spotted knapweed as well as two species of native plants to address objectives 3 and 4. One individual of each species (no competition) will be grown in a variety of different soil treatments. Objective 3 is to determine the relative benefit of the native soil community to the germination and growth of native and exotic plants. Therefore, soil treatments will consist of field-collected native soil (native soil community in-tact) and sterilized field-collected native soil. The relative benefit of the soil community will be determined for each species and comparisons will be made between species, and between groups of natives and exotics. For this experiment, treatments will consist of un-invaded native soil, soil from the perimeter of an old infestation and soil from the core of an old infestation. Soil community assays will be conducted immediately after collection to characterize the soil communities, and again after sterilization to determine the effectiveness of the sterilization procedure

Présentation : USDA

Page publiée le 3 décembre 2015, mise à jour le 29 octobre 2017