Weed control is challenging for Mississippi peanut producers. Research was established during 2017 and 2018 at the Delta Research and Extension Center in Stoneville, Mississippi, to evaluate herbicide programs for weed control and reducing weed seed production in Mississippi peanut production. Treatments were combinations of acetochlor, clethodim, flumioxazin, lactofen, paraquat, and S-metolachlor with their respective adjuvants if needed. Treatments were applied: PRE, early-POST (EPOST), and/or mid-post (MPOST). All treatments included a PRE application followed by (fb) application of EPOST and/or MPOST application. Flumioxazin PRE fb lactofen plus clethodim MPOST provided greatest weed control and peanut yield. This treatment provided 88 to 100% control of barnyardgrass, hemp sesbania, Palmer amaranth, pitted morningglory, and prickly sida. Additionally, this treatment reduced total weed seed production 88% compared to the nontreated control. Flumioxazin PRE fb lactofen plus clethodim EPOST fb acetochlor MPOST provided similar weed control and peanut yield as flumioxazin PRE fb lactofen plus clethodim MPOST. This treatment provided 88 to 100% control of all weed species present and reduced total weed seed production 93%. Sequential applications of PRE, EPOST, and/or MPOST herbicide treatments provided the best season-long control of weeds and weed seed suppression in Mississippi peanut.

Seed loss in canola (Brassica napus, Brassica rapa and Brassica juncea) leads to considerable loss of revenue and dispersal of canola seeds into the soil seedbank. Once canola seeds enter the soil seedbank a portion can become secondarily dormant and persist for many years creating volunteer weed problems in following crops. Reducing canola seed loss and seedbank persistence can be an important strategy to reduce the incidence of volunteer weeds. The primary hypothesis of this research was that canola seedbank addition and dormancy induction in the seed are affected by genotype and harvest method. To test this hypothesis, three studies were conducted with the following objectives: i) to determine canola seedbank addition from windrowing and direct-harvesting operations on commercial farms in western Canada, ii) to determine agronomic- and harvest-related factors that may increase seed loss in canola, iii) to determine the effect of stage of crop maturity at harvest on potential to develop seed dormancy in canola, iv) to evaluate canola genotypes and harvest methods to reduce canola seedbank addition. A total of 66 canola fields were surveyed across Saskatchewan in 2010 and 2011. Shattered seeds from these fields were sampled within 3 weeks of harvest by using a vacuum cleaner. Agronomic- and harvest-related data were collected for each field using questionnaires. In a separate small plot study the effects of harvest methods (windrowing and direct-harvesting) and pod sealant products (Pod-Stik® and Pod Ceal DC®) on seed loss in five canola genotypes (InVigor5440, RR45H26, InVigor5020, RR4362, and CL8571) were evaluated in 2010 and 2011. In both years, 6 harvest samples were collected weekly from InVigor5440 and InVigor5020 genotypes starting at early stage of crop maturity until harvest to assess the effect of seed maturity on dormancy induction. On commercial farms, the average seedbank addition was 5,821 viable seeds m-2, which was equivalent to 7.3% of the total seed yield. There was no difference in the reported yield and seedbank addition between windrowed and direct-harvested canola on commercial farms. But in the small plot study, windrowing resulted in higher seedbank addition. Higher seedbank addition was observed when the yield of canola was higher and when producers had a larger area seeded to canola. The observed seedbank addition was also higher in Roundup Ready genotypes and when a conventional combine harvester was used to harvest canola. Little primary dormancy and low potential to secondary dormancy induction was observed in InVigor5440 and InVigor5020 seeds at an early stage of crop maturity. But at full maturity seeds of both genotypes had no primary dormancy but showed high potential for secondary dormancy induction. This indicates that windrowing the evaluated genotypes at early stage of crop maturity lowered the potential for secondary dormancy induction. There were appreciable differences in seedbank addition among the evaluated canola genotypes but pod sealant products did not affect seed yield and seed shatter in canola. The results of this study suggest that canola seedbank addition can be minimized by growing genotypes having reduced seed loss and with the adoption of direct-harvesting operations.

This dissertation grew from an investigation of the farm Doornkloof in Irene, Pretoria. The farm was home to General Jan Smuts and it is here that he wrote his seminal philosophical work “Holism and Evolution” and found his own grass specie Digitaria Smutsii. The theoretical investigation is rooted in the interpretation of Holism, as an architectural theory, which informs the proposed design intervention. This study is informed by an analysis of the area of Irene, its origins and its future growth lead to the development of a holistic framework. This study proposes to inform the future socio-economic and historical importance of the farm as open public space for the citizens of Tshwane and Irene. The research intervention proposes a new architectural programmatic typology that will celebrate the importance of the Bankenveld landscape. The systematic rehabilitation of the grassland landscape will be achieved by introducing small scale interventions. The series of design interventions will rehabilitate the existing historical layers of the site, create new interest in the farm, improve the economic position of the Jan Smuts Foundation (the owners of the farm) and protect the landscape for the future generation users. / Dissertation MArch (Prof)--University of Pretoria, 2012. / Architecture / unrestricted

Biological invasions have adverse economic, cultural, and ecological effects worldwide. Among the most impactful in North America is the invasion of Phragmites australis (Phragmites), a large-scale clonal grass that rapidly colonizes wetlands. Phragmites crowds out native plants and alters habitat for native fauna. In doing so, Phragmites also alters human access to water resources and has adverse economic effects, including decreasing property value, inhibiting recreational use, and limiting populations of game species. The efforts described in this dissertation are a component of a large, multidisciplinary effort to better understand the anthropogenic stressors to Chesapeake Bay, Maryland, at the land/water interface. Utah State University worked in collaboration with the Smithsonian Environmental Research Center and other academic and public organizations to address this problem from multiple directions. The diverse and extensive studies ranged from aquatic and avian faunal composition and submerged aquatic vegetation to our work on the invasive wetland grass, Phragmites. Having assessed the existing literature and its shortcomings, we conducted a large-scale, long-term study of the effects of Phragmites removal on the Bay. By removing Phragmites from plots in select sub-estuaries of Chesapeake Bay through herbicide spraying, leaving associated plots intact, and comparing both with native wetland conditions, we sought to better understand herbicidal management of Phragmites and the potential for wetland plant community recovery. Although sprayings decreased the relative cover, stem diameters, and stem densities of Phragmites, we found that herbicide treatment alone was not adequate to restore native plant communities or significantly affect seedbank composition. Our results demonstrate the resilience of Phragmites and call for a diverse range of control measures, including mowing, grazing, burning to expose the seedbank to germination, and—if economics allow—active revegetation to establish the desired plant community composition. This dissertation provides beneficial data for those who seek to manage Phragmites in wetland plant communities, but there is much work still to be done. The literature review, seedbank study, and community analysis included in this volume are components of a larger research program on Phragmites management. Future studies should, in particular, investigate revegetation and nutrient amelioration as means to recover pre-invasion vegetation.

A robust ecosystem requires a functionally heterogeneous community of organisms with a wide range of traits that permits broad resource partitioning. Understanding community diversity patterns can help investigate drivers of community assembly and how different metrics reflect the success of restoration in grassland or weed control in cropland. The objectives of my study were to identify assembly drivers influencing community taxonomic, phylogenetic, and functional diversity. The first study examined the effect of different ecotypes of dominant species on grassland community diversity along a spatial aridity gradient during restoration. This study showed that ecotype significantly affected species richness and shaped taxonomic, phylogenetic, and functional diversity. Accordingly, restorations should consider ecotypic variation as a critical biological filter to community assembly in grassland ecosystems. Given the community response across the tallgrass prairie, restoration practitioners should draw attention to regional sources of dominant species because ideal ecotypic sources can affect species richness and even sustain the phylogenetic and functional patterns. The restoration efficacy of existing ecosystems should be evaluated to large-scale diversity patterns to detect gaps and limitations that will reveal which diversity components to highlight for further restoration investment. The second study investigated temporal variations in diversity metrics among dominant species ecotypes and a drought treatment on the importance of external and internal filters in shaping the assembly of grassland communities. In this study, species richness decreased significantly during the early stages of restoration while phylogenetic and functional diversity was maintained over eight years. I also found no significant effect of experimental drought treatment on community biodiversity. Moreover, ecotypic variation as an internal filter played a key role in grassland assembly but the external filter was less strong because of high trait overlap among species within a community. In general, this study highlighted the consequence of integrating both interspecific and intraspecific trait variabilities and the value of concentrating on functional traits to comprehend better how trait variability is coupled with species coexistence. Future investigations are necessary to examine the distinctive origins of variability in plant traits and how they contribute to grassland community assembly. The third study focused on whether weed management tactics such as a glyphosate-resistant (GR) cropping system were beneficial to control weed diversity in the soil seedbank of the agroecosystem. Both phylogenetic and functional diversity of the soil seedbank was relatively stable with different GR cropping systems across six years. The neutral assembly of the soil seedbank may imply that the belowground weed community could be restrained by stochastic mechanisms, such as dispersal and demographic stochasticity of seeds, during agricultural activities. Therefore, I recommend integrated weed management with a sustainable perspective to fight against the evolutionary feedback due to weed herbicide resistance. While the GR cropping system still seems beneficial, future weed control cannot overlook the extensive impact of GR systems on biodiversity variations, the shifts in weed composition, and the resistance evolution of weed species to herbicides in the agroecosystem.

Cattle grazing has been a historic use of rangelands in Utah since Pioneer settlement in the mid 1800's. Wright fishhook cactus is a small globose cactus endemic to an area of 280,000 ha in south-central Utah and was listed as endangered in October of 1979, by the U.S. Fish and Wildlife Service (USFWS). By 2010, concerns were expressed that soil compaction in proximity to the cactus posed a threat to this species, though there was no empirical data to support such concern. In order to assess the impact of cattle traffic on Wright fishhook cactus, we used an imprint device to simulate a cow track's impact. We applied a treatment of either zero, one, or four hoof imprints within 15 cm evenly of 146 cacti within the same population cluster on the same day. We monitored subsequent plant survival as well as reproductive success. Each cactus in the study was visited multiple times and all developed seed was collected. We found that cattle traffic of any amount had no effect on plant survival or seed production and therefore concluded that cattle traffic poses no threat to Wright fishhook cactus. The status of this cactus yields no justification for changing the historic land management use of cattle grazing on these rangelands. Seedbank abundance and location has not been examined for any species within the genus Sclerocactus. Over a one-day period, we took 500 soil samples from various locations near the cactus and potential nurse-plants. We found that approximately 1% of annual seed production makes it into the seedbank, a number in line with other species in the Cactaceae family. Seedbank densities were highest immediately adjacent to, and downslope from, parent plants. Understanding the dynamics of the seedbank of this species could lead to more informed management practices.

In river ecology the description and understanding of near-natural ecosystem functionality is a difficult task to achieve as the majority of river floodplains have been intensively impacted by human activities. This work addresses ecological functionality of a relatively unimpacted large river system, focussing on the lateral dynamic and connectivity mechanisms driving aquatic vegetation processes. Macrophytes were found to be very patchily distributed at the riverscape scale, being mainly confined to low energy lateral habitats in the floodplain, such as backwaters. Backwaters provided favourable conditions for plants to colonise and recruit and contributed highly to species diversity and productivity at the floodplain scale. Differences between backwaters were attributed to the frequency of connectivity with the main channel during flood events. Nevertheless, the ecological mechanism driving diversity through flooding appears not to be related to flow disturbance. Biomass produced in backwaters was found to remain stable after potentially scouring floods. Therefore the hypothesis that flood disturbances promote species diversity through the removal and destruction of biomass and rejuvenate communities such that species coexistence is increased was rejected. Rather, it appears that diversity in backwaters increases along a temporal gradient as a response to the input of colonists and their accumulation overtime through successive flood inputs. Despite the apparently non-destructive effect of floods on macrophyte biomass, backwaters appear to have a significant role in exporting large amounts of plant propagules from the site of production. Backwaters represented a net source of propagules which highly enriched the main channel pool of potential colonists. However, whereas propagules could be dispersed for long distances in flood flows the probability for them to reach a suitable downstream habitat was extremely low. This work showed that dispersal at baseflow and entry to backwaters through the downstream end after short dispersal drift provided a greater chance of successful colonisation despite the individually much shorter distance moved. Backwaters were demonstrated to be rather isolated aquatic habitats, even though they experience hydrological connectivity, suggesting that primary colonisation of these sites is a limiting step. Instead, colonisation was shown to rely primarily on propagules generated internally by established plants. Whereas colonisation could occur via internal re-organisation of existing plant propagules, the backwater seed bank could also contribute to the macrophytes species established in backwaters. Such contribution was consistently low to medium along a gradient of disturbances and connectivity and showed independence from such river flow processes. Species richness was found to be higher in the established species than in the seed bank, suggesting that asexual reproduction is prioritised by aquatic vegetation in riverine backwaters. The occurrence or persistence of macrophyte species in backwaters depends upon rhizome and plant shoot regeneration. The lack of influence of connectivity revealed that plants may originate from both in situ and externally waterborne vegetative propagules derived from other upstream backwaters. This research demonstrated that the lateral dynamic and associated connectivity are major components of river floodplain ecology which generate a wide spectrum of habitats and have a controlling effect on vegetation processes. Therefore a naturally dynamic ecological state is required to support ecosystem functionality in large river floodplains and especially to maintain a high level of species diversity, productivity and colonisation of backwaters by macrophytes.

In this study three aspects of sexual reproduction in Everglades plants were examined to more clearly understand seed dispersal and the allocation of resources to sexual reproduction— spatial dispersal process, temporal dispersal of seeds (seedbank), and germination patterns in the dominant species, sawgrass (Cladium jamaicense). Community assembly rules for fruit dispersal were deduced by analysis of functional traits associated with this process. Seedbank ecology was investigated by monitoring emergence of germinants from sawgrass soil samples held under varying water depths to determine the fate of dispersed seeds. Fine-scale study of sawgrass fruits yielded information on contributions to variation in sexually produced propagules in this species, which primarily reproduces vegetatively. It was hypothesized that Everglades plants possess a set of functional traits that enhance diaspore dispersal. To test this, 14 traits were evaluated among 51 species by factor analysis. The factorial plot of this analysis generated groups of related traits, with four suites of traits forming dispersal syndromes. Hydrochory traits were categorized by buoyancy and appendages enhancing buoyancy. Anemochory traits were categorized by diaspore size and appendages enhancing air movement. Epizoochory traits were categorized by diaspore size, buoyancy, and appendages allowing for attachment. Endozoochory traits were categorized by diaspore size, buoyancy, and appendages aiding diaspore presentation. These patterns/trends of functional trait organization also represent dispersal community assembly rules. Seeds dispersed by hydrochory were hypothesized to be caught most often in the edge of the north side of sawgrass patches. Patterns of germination and dispersal mode of all hydrochorous macrophytes with propagules in the seedbank were elucidated by germination analysis from 90 soil samples collected from 10 sawgrass patches. Mean site seed density was 486 seeds/m2 from 13 species. Most seeds collected at the north side of patches and significantly in the outer one meter of the patch edge (p = 0.013). Sawgrass seed germination was hypothesized to vary by site, among individual plants, and within different locations of a plant’s infructescence. An analysis of sawgrass fruits with nested ANOVAs found that collection site and interaction of site x individual plant significantly affect germination ability, seed viability, and fruit size (p < 0.050). Fruit location within a plant’s infructescence did not significantly affect germination. As for allocation of resources to sexual reproduction, only 17.9% of sawgrass seeds germinated and only 4.8% of ungerminated seeds with fleshy endosperm were presumed viable, but dormant. Collectively, only 22% of all sawgrass seeds produced were viable.

<p>  </p> <p>Annual bluegrass (<em>Poa annua</em> L.) is the most troublesome weed in turfgrass systems and the second most troublesome weed across all grass crops. Controlling annual bluegrass is exceptionally complicated due to its high genetic adaptability to new environments. Additionally, prolific seed production allowed the rapid development of herbicide resistance to 12 herbicide modes of action. Experiments were initiated with the goal to better understand annual bluegrass ecology and resistance to ethofumesate. A dose-response experiment was initiated in 2022 to determine the potential level of ethofumesate resistance in annual bluegrass collected from seed production systems. Seed from 55 annual bluegrass populations was obtained from three sources: seed production fields (31 populations), seed cleaning process (6 populations), and seed testing prior to retail distribution (18 populations). </p> <p>Individual seedlings (2–3 tillers) were treated with ten doses of ethofumesate: 0, 0.6, 1.1, 2.8, 5.6, 8.4, 11.2, 16.8, 22.4, and 44.8 kg ai ha−1; with 1.1 to 2.2 kg ha−1 as the label application rates for perennial ryegrass (<em>Lolium perenne</em> L.). The resistance to susceptible ratio of populations across all sources ranged from 0.48 to 5.48. The most resistant populations from production fields, removed during the seed cleaning process, or found in seed testing lots had ED50 values of 12.1, 13.1, and 9.4 kg ai ha−1, respectively. Further, 68% of the populations found in production fields had ED50 higher than 6 kg ai ha−1, which indicates that annual bluegrass resistance is common in grass seed production. A garden study was initiated in November 2020 to assess the development, reproduction, and survival of ten annual bluegrass populations in Indiana. Annual bluegrass plants were maintained in the absence of turf competition and not subjected to typical turfgrass management practices including irrigation, mowing and fertilization. Data collected in included growth rate, biomass production, ground cover, morphology, flowering time, seed production and morphology, and both winter survival and subsequent summer survival of plants. Principal component analysis indicated that certain populations grouped together based on their development, morphology, stress tolerance, and seed production. Plants from the cooler climates (OR, PA, and IN) were characterized by higher growth rates and biomass compared to southern ecotypes. These three populations survived the longest during the summer, with the PA population averaging the highest ground cover of 276 cm2 on 23 July 2021. Plants from warm climates (AL, FL, NC, SC, TN, TX) had poor summer survival. Additionally, the FL population had the highest winterkill of 68%, followed by TX at 45%. The NJ population was distinct from other populations, and plants had robust aboveground biomass and high seed production. The results indicate that the development, reproduction, and survival of different annual bluegrass biotypes are dependent on the climate of origin. A third experiment was designed to understand patterns of germination and seed longevity in populations from five climates across the U.S. at two depths of burial. Seed was retrieved in 6-month intervals up to 24 months. Seed viability by depth (surface vs. 5-cm deep) of burial differed only 18 months after the initiation of the study. However, seed viability did differ among populations on each date of seed retrieval. Viability was low ranging from 0.21 to 0.91%, and populations originating from cool climates (New Jersey, Pennsylvania, and Oregon) generally had higher viability than populations originating from warmer climates. Annual bluegrass seed tested in this study typically had low levels of survival (<0.5%); however, all populations retained some level of viability 24 months after burial, which would allow future reproduction of this troublesome weed. Overall, this research determined that herbicides alone will likely be ineffective at controlling annual bluegrass and that knowledge of the development, reproduction, and survival of local annual bluegrass populations should be factored into an integrated weed management strategies created for each site. </p> <p>  </p>

No description available.