The Role of Light and Soil Moisture in Plant Community Resistance to Invasion by Yellow Starthistle (\u3ci\u3eCentaurea solstitialis\u3c/i\u3e)

To resist establishment by an invasive plant, a community may require one or more species functionally similar to the invader in their resource acquisition pattern. In this study, communities consisting of native winter annual forbs, non-native annual grasses, native perennials, or a combination of the two native communities were established with and without Centaurea solstitialis to determine the effect of soil moisture and light availability on plant community invasion resistance. The annual plant communities were unable to resist invasion by C. solstitialis. In the native winter annual forb community, senescence in late spring increased light penetration (\u3e75%) to the soil surface, allowing seeded C. solstitialis to quickly establish and dominate the plots. In addition, native annual forbs utilized only shallow soil moisture, whereas C. solstitialis used shallow and deep soil moisture. In communities containing native perennials, only Elymus glaucus established well and eventually dominated the plots. During the first 2 years of establishment, water use pattern of perennial communities was similar to native annual forbs and resistance to invasion was associated with reduced light availability during the critical stages of C. solstitialis establishment. In later years, however, water use pattern of perennial grass communities was similar or greater than C. solstitialis-dominated plots. These results show that Central Valley grasslands that include E. glaucus resist C. solstitialis invasion by a combination of light suppression and soil water competition. Spatiotemporal resource utilization patterns, and not just functional similarity, should be considered when developing restoration strategies to resist invasion by many non-native species

Herbicide Management of Threespike Goosegrass in California Orchards

Threespike goosegrass (Eleusine tristachya) is a difficult-to-control perennial grass of increasing concern for orchard production systems in the Central Valley of California, USA. This grass has a bunch-type growth habit when tillered, which can interfere with orchard operations, particularly nut pickup from the ground at harvest. From 2016 to 2019, herbicide efficacy on threespike goosegrass was evaluated in a walnut (Juglans regia) orchard in Chico, CA, USA; an almond (Prunus dulcis) orchard in Livingston, CA, USA; and a prune (Prunus domestica) orchard in Orland, CA, USA. At each location, two independent experiments were conducted to evaluate 12 preemergent (PRE) herbicide treatments and eight postemergent (POST) treatments over several years, for a total of 16 trials. PRE herbicides were applied in January according to the region’s typical winter orchard management practices. One treatment included an additional sequential application in March to extend residual activity later into the warm season when threespike goosegrass germinates or resumes growth. In separate studies, POST control of established stands of threespike goosegrass was evaluated in May and June of each year. Each trial was conducted in a randomized complete block design with four replications. Threespike goosegrass control was visually estimated monthly for 5 months after the PRE treatments or at weekly intervals for 5 weeks following POST treatments. The most effective PRE treatment was a sequential application of indaziflam in January, followed by a March application of pendimethalin, providing 90% or greater control of threespike goosegrass 5 months after treatment across all sites and all years. Of the POST treatments, the three graminicides outperformed the other treatments with 73% to 91% control overall sites and years at 5 weeks after treatment. Fluazifop had the highest control ratings (85% to 91%) among the graminicide herbicides but was not always statistically better than clethodim or sethoxydim (74% to 83% control). Glyphosate alone resulted in unacceptable control (33% to 51%) regardless of rates tested, experimental sites, or years. Together, these results confirm grower reports of poor glyphosate performance on threespike goosegrass but suggest that effective herbicide programs can be developed to manage threespike goosegrass using PRE herbicides and POST graminicides registered in California orchard crops

Stinkwort is rapidly expanding its range in California

Stinkwort (Dittrichia graveolens) is a Mediterranean native that has become a weed in areas of Europe as well as in Australia. This strongly aromatic weed was first reported in California in 1984 in Santa Clara County, and it had spread to 36 of the 58 California counties by 2012. Stinkwort is not palatable to animals, and can be poisonous to livestock and cause contact allergic dermatitis in humans. In California, this weed is found primarily along roadsides. However, the biology of this annual plant suggests that it could also invade open riparian areas and overgrazed rangelands. Stinkwort has an unusual life cycle among annual plants: Unlike most summer or late-season winter annuals, stinkwort flowers and produces seeds from September to December. Such basic biological information is critical to developing timely and effective control strategies for this rapidly expanding weed

Stinkwort is rapidly expanding its range in California

Stinkwort (Dittrichia graveolens) is a Mediterranean native that has become a weed in areas of Europe as well as in Australia. This strongly aromatic weed was first reported in California in 1984 in Santa Clara County, and it had spread to 36 of the 58 California counties by 2012. Stinkwort is not palatable to animals, and can be poisonous to livestock and cause contact allergic dermatitis in humans. In California, this weed is found primarily along roadsides. However, the biology of this annual plant suggests that it could also invade open riparian areas and overgrazed rangelands. Stinkwort has an unusual life cycle among annual plants: Unlike most summer or late-season winter annuals, stinkwort flowers and produces seeds from September to December. Such basic biological information is critical to developing timely and effective control strategies for this rapidly expanding weed

Spatio-Temporal Relationship between Water Depletion and Root Distribution Patterns of \u3ci\u3eCentaurea solstitialis\u3c/i\u3e and Two Native Perennials

In a 2-year field study, we quantified lateral root growth patterns and soil water depletion dynamics in the invasive annual Centaurea solstitialis and two native perennials, Elymus glaucus and Grindelia camporum. Centaurea solstitialis produced lateral roots most actively from early April to mid-June, during the late rosette to spiny seedhead stage while both root growth and water depletion were completed before flowering. In the wet year, roots were evenly distributed throughout the soil profile to 180 cm deep. Lack of deep soil moisture recharge in the second year restricted root distribution to shallow soil depths (\u3c 60 cm). In contrast to C. solstitialis, living roots of the native perennials persisted throughout the year. Elymus glaucus roots were most abundant (47% of total roots) in the upper soil profile (≤ 60 cm) in the wet year, but most abundant (55%) in the lower profile (≥ 150 cm) in the dry year. However, the distribution of G. camporum roots was comparable between the 2 years. This indicates that in years with little to no deep soil moisture recharge, C. solstitialis roots are distributed in the shallow soil profile similar to annual grasses, whereas in wetter years it is similar to deep-rooted perennial species. We also show that C. solstitialis impacts grassland communities by depleting soil moisture during the short period of lateral root growth from the late rosette to the spiny stage. Therefore, control of C. solstitialis early in the season is critical during native plant restoration where success depends upon available soil moisture

The Role of Light and Soil Moisture in Plant Community Resistance to Invasion by Yellow Starthistle (\u3ci\u3eCentaurea solstitialis\u3c/i\u3e)

To resist establishment by an invasive plant, a community may require one or more species functionally similar to the invader in their resource acquisition pattern. In this study, communities consisting of native winter annual forbs, non-native annual grasses, native perennials, or a combination of the two native communities were established with and without Centaurea solstitialis to determine the effect of soil moisture and light availability on plant community invasion resistance. The annual plant communities were unable to resist invasion by C. solstitialis. In the native winter annual forb community, senescence in late spring increased light penetration (\u3e75%) to the soil surface, allowing seeded C. solstitialis to quickly establish and dominate the plots. In addition, native annual forbs utilized only shallow soil moisture, whereas C. solstitialis used shallow and deep soil moisture. In communities containing native perennials, only Elymus glaucus established well and eventually dominated the plots. During the first 2 years of establishment, water use pattern of perennial communities was similar to native annual forbs and resistance to invasion was associated with reduced light availability during the critical stages of C. solstitialis establishment. In later years, however, water use pattern of perennial grass communities was similar or greater than C. solstitialis-dominated plots. These results show that Central Valley grasslands that include E. glaucus resist C. solstitialis invasion by a combination of light suppression and soil water competition. Spatiotemporal resource utilization patterns, and not just functional similarity, should be considered when developing restoration strategies to resist invasion by many non-native species

Herbicide-Assisted Restoration of Great Basin Sagebrush Steppe Infested With Medusahead and Downy Brome

Downy brome or cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae) are the most problematic invasive annual grasses in rangelands of the western United States, including sagebrush communities that provide habitat to sage grouse. Rehabilitation of infested sites requires effective weed control strategies combined with seeding of native plants or desirable competitive species. In this study, we evaluated the effect of three fall-applied pre-emergence herbicides (imazapic, rimsulfuron, and chlorsulfuron+sulfometuron), and one spring-applied postemergence herbicide (glyphosate) on the control of downy brome and medusahead and the response of seeded perennial species and resident vegetation in two sagebrush communities in northeastern California. All pre-emergence treatments gave >93% control of both invasive species at both sites in the first year. Glyphosate was less consistent, giving >94% control at one site and only 61% control of both species at the other site. Imazapic was the only herbicide to maintain good control (78-88%) of both species 2 yr after treatment. No herbicide caused detectible long term damage to either perennial grasses or annual forbs, and imazapic treatment resulted in an increase in resident native forb cover 3 yr after treatment. Broadcast seeding with or without soil incorporation did not result in successful establishment of perennial species, probably due to below-average precipitation in the year of seeding. These results indicate that several chemical options can give short-term control of downy brome and medusahead. Over the course of the study, imazapic provided the best management of both invasive annual grasses while increasing native forb cover.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202