323 research outputs found

    Vegetation Dynamics at a Mojave Desert Restoration Site, 1992 to 2007

    Get PDF
    The Twist Hollow restoration site on BLM land near St. George, Utah, had been badly disturbed by sand mining, rock quarrying, dumping, off-road vehicles and target shooting prior to its closure and treatment. In December 1992 the site was sculpted and drill seeded with Indian ricegrass (Stipa hymenoides), sand dropseed (Sporobolus cryptandrus), galleta (Hilaria jamesii), gooseberryleaf globemallow (Sphaeralcea grossulariifolia) Palmer penstemon (Penstemon palmeri), fourwing saltbush (Atriplex canescens) and winterfat (Krascheninnikovia lanata) in an effort restore natural vegetation and desert tortoise habitat. Vegetation was sampled before and after treatment and subsequently monitored over a period of 14 years. With the exception of winterfat, all the seeded species established and increased in density and/or cover during the period 1993-1998. Cheatgrass (Bromus tectorum) also increased and became dominant during this period. Seeding was most successful on a rockier substrate where fourwing saltbush became a dominant shrub. Drought conditions after 1998 corresponded with declines in most seeded species while broom snakeweed (Gutierrezia sarothrae), hairy goldenaster (Chrysopsis villosa), desert globemallow (Sphaeralcea ambigua) and sandsage (Artemisia filifolia) increased through recruitment from surrounding vegetation. Sandsage was the dominant shrub of nearby undisturbed sandy sites and grew rapidly following establishment in a sandier portion of the treated area. Cheatgrass and other annuals fluctuated from year to year in the treated area but had lower density and cover than nearby untreated areas throughout the monitoring period. We conclude that the restoration project’s objectives have been met to varying degrees despite the limited persistence of the seeded species. Further research into management techniques aimed at reducing annual grasses and enhancing high-quality desert tortoise forage is recommended

    RCLUS, A NEW PROGRAM FOR CLUSTERING ASSOCIATED SPECIES: A DEMONSTRATION USING A MOJAVE DESERT PLANT COMMUNITY DATASET

    Get PDF
    This paper presents a new clustering program named RCLUS that was developed for species (R-mode) analysis of plant community data. RCLUS identifies clusters of co-occurring species that meet a user-specified cutoff level of positive association with each other. The "strict affinity" clustering algorithm in RCLUS builds clusters of species whose pairwise associations all exceed the cutoff level, whereas the "coalition" clustering algorithm only requires that the mean pairwise association of the cluster exceeds the cutoff level. Both algorithms allow species to belong to multiple clusters, thus accommodating both generalist and specialist species. Using a 60-plot dataset of perennial plants occurring on the Beaver Dam Slope in southwestern Utah, we carried out RCLUS analyses and compared the results with 2 widely used clustering techniques: UPGMA and PAM. We found that many of the RCLUS clusters were subsets of the UPGMA and PAM clusters, although novel species combinations were also generated by RCLUS. An advantage of RCLUS over these methods is its ability to exclude species that are poorly represented in a dataset as well as species lacking strong association patterns. The RCLUS program also includes modules that assess the affinity of a given species, plot, or environmental variable to a given cluster. We found statistically significant correlations between some of the RCLUS species clusters and certain environmental variables of the study area (elevation and topographical position). We also noted differences in clustering behavior when different association coefficients were used in RCLUS and found that those incorporating joint absences (e.g., the phi coefficient) produced more clusters and more even numbers of species per cluster than those not incorporating joint absences (e.g., the Jaccard index). In addition to the species association application described in this paper, the RCLUS algorithms could be used for preliminary data stratification in sample (Q-mode) analysis. The indirect link between sample plots and RCLUS species clusters could also be exploited to yield a form of "fuzzy" classification of plots or to characterize species pools of plots

    Molecular Biogeography of Tribe Thermopsideae (Leguminosae): A Madrean-Tethyan Disjunction Pattern with an African Origin of Core Genistoides

    Get PDF
    Thermopsideae has 45 species and exhibits a series of interesting biogeographical distribution patterns, such as Madrean-Tethyan disjunction and East Asia-North America disjunction, with a center of endemism in the Qinghai-Xizang Plateau (QTP) and Central Asia. Phylogenetic analysis in this paper employed maximum likelihood using ITS, rps16, psbA-trnH, and trnL-F sequence data; biogeographical approaches included BEAST molecular dating and Bayesian dispersal and vicariance analysis (S-DIVA). The results indicate that the core genistoides most likely originated in Africa during the Eocene to Oligocene, ca. 55-30 Ma, and dispersed eastward to Central Asia at ca. 33.47 Ma. The origin of Thermopsideae is inferred as Central Asian and dated to ca. 28.81 Ma. Ammopiptanthus is revealed to be a relic. Birth of the ancestor of Thermopsideae coincided with shrinkage of the Paratethys Sea at ca. 30 Ma in the Oligocene. The Himalayan motion of QTP uplift of ca. 20 Ma most likely drove the diversification between Central Asia and North America. Divergences in East Asia, Central Asia, the Mediterranean, and so forth, within Eurasia, except for Ammopiptanthus, are shown to be dispersals from the QTP. The onset of adaptive radiation at the center of the tribe, with diversification of most species in Thermopsis and Piptanthus at ca. 4-0.85 Ma in Tibet and adjacent regions, seems to have resulted from intense northern QTP uplift during the latter Miocene to Pleistocene

    Phylogeny of Salsoleae s.l. (Chenopodiaceae) based on DNA sequence data from ITS, psbB-psbH, and rbcL, with emphasis on taxa of northwestern China

    Get PDF
    To reconstruct phylogeny and verify the monophyly of major subgroups, a total of 52 species representing almost all species of Salsoleae s.l. in China were sampled, with analysis based on three molecular markers (nrDNA ITS, cpDNA psbB psbH and thcL), using maximum parsimony, maximum likelihood, and Bayesian inference methods Our molecular evidence provides strong support for the following: (1) Camphorosmeae is nested within Salsoleae s.l. instead of the previously suggested sister relationship. (2) Tribe Salsoleae s.I is monophyletic and is composed of three monophyletic subunits, Caroxyloneae, the Kali clade, and Salsoleae s.str (3) Climacoptera is separated from Salsola s I It does not form a monophyletic group but is split into two monophyletic parts, Climacoptera I and Chmacoptera II (4) Halogeton is clearly polyphyletic, as are Anabasis and the genus Salsola s.l. (5) Caroxylon, Halo.xylon, Kali, and Petrosnnonia are well-supported monophyletic genera. Additional evidence is needed regarding the monophyly of Halimocnemis, which remains unclear

    Predasjon i norsk næringsliv : utfordringer ved kostnadsestimering.

    Get PDF
    Denne utredningen tar for seg utfordringer som oppstår ved beregning av kostnader i forbindelse med mistanke om utnyttelse av dominerende stilling i form av rovprising. Til dette formålet har jeg sett på hvilke regler som ligger til grunn for regulering av dominante aktører og jeg har sett på hovedelement fra kostnadsregnskapet som er nødvendig for utføre teste den norske lovgivningen krever i dag. Utfordringen som ligger i kostnadstestene har jeg belysts ved å se på kostnadsestimering i luftfarten

    Factors Associated with Work Participation and Work Functioning in Depressed Workers: A Systematic Review

    Get PDF
    Background Depression is associated with negative work outcomes such as reduced work participation (WP) (e.g., sick leave duration, work status) and work functioning (WF) (e.g., loss of productivity, work limitations). For the development of evidence-based interventions to improve these work outcomes, factors predicting WP and WF have to be identified. Methods This paper presents a systematic literature review of studies identifying factors associated with WP and WF of currently depressed workers. Results A total of 30 studies were found that addressed factors associated with WP (N = 19) or WF (N = 11). For both outcomes, studies reported most often on the relationship with disorder-related factors, whereas personal factors and work-related factors were less frequently addressed. For WP, the following relationships were supported: strong evidence was found for the association between a long duration of the depressive episode and work disability. Moderate evidence was found for the associations between more severe types of depressive disorder, presence of co-morbid mental or physical disorders, older age, a history of previous sick leave, and work disability. For WF, severe depressive symptoms were associated with work limitations, and clinical improvement was related to work productivity (moderate evidence). Due to the cross-sectional nature of about half of the studies, only few true prospective associations could be identified. Conclusion Our study identifies gaps in knowledge regarding factors predictive of WP and WF in depressed workers and can be used for the design of future research and evidence-based interventions. We recommend undertaking more longitudinal studies to identify modifiable factors predictive of WP and WF, especially work-related and personal factors

    Models of <i>KPTN</i>-related disorder implicate mTOR signalling in cognitive and overgrowth phenotypes

    Get PDF
    KPTN-related disorder is an autosomal recessive disorder associated with germline variants in KPTN (previously known as kaptin), a component of the mTOR regulatory complex KICSTOR. To gain further insights into the pathogenesis of KPTN-related disorder, we analysed mouse knockout and human stem cell KPTN loss-of-function models. Kptn -/- mice display many of the key KPTN-related disorder phenotypes, including brain overgrowth, behavioural abnormalities, and cognitive deficits. By assessment of affected individuals, we have identified widespread cognitive deficits (n = 6) and postnatal onset of brain overgrowth (n = 19). By analysing head size data from their parents (n = 24), we have identified a previously unrecognized KPTN dosage-sensitivity, resulting in increased head circumference in heterozygous carriers of pathogenic KPTN variants. Molecular and structural analysis of Kptn-/- mice revealed pathological changes, including differences in brain size, shape and cell numbers primarily due to abnormal postnatal brain development. Both the mouse and differentiated induced pluripotent stem cell models of the disorder display transcriptional and biochemical evidence for altered mTOR pathway signalling, supporting the role of KPTN in regulating mTORC1. By treatment in our KPTN mouse model, we found that the increased mTOR signalling downstream of KPTN is rapamycin sensitive, highlighting possible therapeutic avenues with currently available mTOR inhibitors. These findings place KPTN-related disorder in the broader group of mTORC1-related disorders affecting brain structure, cognitive function and network integrity.</p

    The Cool Little Kids randomised controlled trial: Population-level early prevention for anxiety disorders

    Get PDF
    Background: The World Health Organization predicts that by 2030 internalising problems (e.g. depression and anxiety) will be second only to HIV/AIDS in international burden of disease. Internalising problems affect 1 in 7 school aged children, impacting on peer relations, school engagement, and later mental health, relationships and employment. The development of early childhood prevention for internalising problems is in its infancy. The current study follows two successful &lsquo;efficacy&rsquo; trials of a parenting group intervention to reduce internalising disorders in temperamentally inhibited preschool children. Cool Little Kids is a population-level randomised trial to determine the impacts of systematically screening preschoolers for inhibition then offering a parenting group intervention, on child internalising problems and economic costs at school entry.Methods/Design: This randomised trial will be conducted within the preschool service system, attended by more than 95% of Australian children in the year before starting school. In early 2011, preschool services in four local government areas in Melbourne, Australia, will distribute the screening tool. The &asymp;16% (n&asymp;500) with temperamental inhibition will enter the trial. Intervention parents will be offered Cool Little Kids, a 6-session group program in the local community, focusing on ways to develop their child&rsquo;s bravery skills by reducing overprotective parenting interactions. Outcomes one and two years post-baseline will comprise child internalising diagnoses and symptoms, parenting interactions, and parent wellbeing. An economic evaluation (costconsequences framework) will compare incremental differences in costs of the intervention versus control children to incremental differences in outcomes, from a societal perspective. Analyses will use the intention-to-treat principle, using logistic and linear regression models (binary and continuous outcomes respectively) to compare outcomes between the trial arms.Discussion: This trial addresses gaps for internalising problems identified in the 2004 World Health Organization Prevention of Mental Disorders report. If effective and cost-effective, the intervention could readily be applied at a population level. Governments consider mental health to be a priority, enhancing the likelihood that an effective early prevention program would be adopted in Australia and internationally.<br /
    corecore