Resource competition in plant invasions: emerging patterns and research needs

Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species

Building Partnerships to Promote Economic and Social Wellbeing and Learning

The paper describes, three initiatives that illustrate ways in which governments can intervene to promote social objectives are described in this paper: Raploch Urban Regeneration in Scotland; the Drugs Round Table in St Kilda, Vic; and Loch Lomond and the Trossachs National Park in Scotland. The paper discusses the conditions that are necessary to achieve effective partnership formation

Evaluation of Parametric Limitations in Simulating Greenhouse Gas Fluxes from Irish Arable Soils Using Three Process-Based Models

The senior author gratefully acknowledges the funding by the Science, Technology, Research and Innovation for the Environment (STRIVE) Programme of the Irish Government under the National Development Plan 2007-2013 and the Department of the Environment, Heritage and Local Government. The authors would like to thanks Phillip O’Brien (EPA) for extending technical and relevant support; Mike Williams, Mike Jones and Matt Saunders (TCD), Komsan Rueangritsarakul and Mohamed Helmy (UCD) for supplying experimental data for modelling work; as well as Tom Bolger and Tommy Gallagher (UCD) for providing administrative support.Peer reviewedPublisher PD

Isolated Lumbar Extension Resistance Training Improves Strength, Pain, and Disability, but Not Spinal Height or Shrinkage (“Creep”) in Participants with Chronic Low Back Pain

Objective. Loss of disc height is commonly associated with chronic low back pain (CLBP). Isolated lumbar extension (ILEX) exercise for the lumbar extensors is recommended to treat CLBP and is suggested such exercise might promote disc healing and regeneration. This study examined a 12-week ILEX intervention on indirect determination of disc height and shrinkage through seated stadiometry, strength, pain, and disability. Design. A quasi-experimental wait-list controlled design was used. Nine participants underwent pretesting (T1), a 12-week control period, retesting (T2), a 12-week intervention period, and finally posttesting (T3). Seated stadiometry, ILEX strength, pain, and disability were measured at each time point. Results. No significant repeated-measures effects for any seated stadiometry variables occurred. Significant improvement across the intervention period (T2 to T3) was found for strength (P <0.0001; effect size [ES] = 2.42). Change in pain was not significant for repeated effects (P = 0.064); however, ES for the intervention period (T2 to T3) was moderate (ES = −0.77). Change in disability was significant between time point T1 and T3 (P = 0.037) and ES for the intervention period (T2 to T3) was large (ES = −0.92). Pain and disability achieved minimal clinically important changes. Conclusions. This is apparently the first study to examine disc change in vivo after exercise in CLBP. Results of the present study, though supporting ILEX resistance training to improve strength, pain, and disability, did not find any effect on spinal height

Spatially Related Sampling Uncertainty in the Assessment of Labile Soil Carbon and Nitrogen in an Irish Forest Plantation

The importance of labile soil carbon (C) and nitrogen (N) in soil biogeochemical processes is now well recognized. However, the quantification of labile soil C and N in soils and the assessment of their contribution to ecosystem C and N budgets is often constrained by limited information on spatial variability. To address this, we examined spatial variability in dissolved organic carbon (DOC) and dissolved total nitrogen (DTN) in a Sitka spruce forest in central Ireland. The results showed moderate variations in the concentrations of DOC and DTN based on the mean, minimum, and maximum, as well as the coefficients of variation. Residual values of DOC and DTN were shown to have moderate spatial autocorrelations, and the nugget sill ratios were 0.09% and 0.10%, respectively. Distribution maps revealed that both DOC and DTN concentrations in the study area decreased from the southeast. The variability of both DOC and DTN increased as the sampling area expanded and could be well parameterized as a power function of the sampling area. The cokriging technique performed better than the ordinary kriging for predictions of DOC and DTN, which are highly correlated. This study provides a statistically based assessment of spatial variations in DOC and DTN and identifies the sampling effort required for their accurate quantification, leading to improved assessments of forest ecosystem C and N budgets.University College DublinChina Scholarship Council (CSC

Biological invaders: Always the bad guys?

Invasive species are recognized as one of the major environmental problems worldwide and responsible for a myriad of impacts on ecosystems and ecosystem processes. Although many invasive species exert a range of detrimental effects a more nuanced approach is now emerging, which acknowledges that they can make a positive or beneficial contribution (Schlaepfer et al., 2011; Vimercati et al., 2020, 2022; Mantoani et al., 2022). Clearly, a positive impact may not always be beneficial (Vimercati et al., 2022) and nutrient enrichment due the introduction of an alien nitrogen-fixing plant species, for instance, could result in the loss of important resident species with low nutrient requirements

The Effect of Cutting and Waterlogging on Plant-Related CO2 and N2O Fluxes Associated with the Invasive N-Fixing Species Gunnera tinctoria

The overall impact that plant invasions have on greenhouse gas emissions (GHG) by plant-mediated effects and how these interact with environmental and management factors is largely unknown. To address this, we report on the effects of leaf removal and waterlogging, either singularly or in combination, on the fluxes of CO2 and N2O associated with the invasive species Gunnera tinctoria. Both the removal of leaves with and without flooding resulted in higher CO2 emissions due to reductions in photosynthesis. Whilst waterlogging alone was also associated with a reduction in photosynthesis, this was slower than the effect of leaf removal. Significant N2O emissions were associated with intact plants, which increased immediately after leaf removal, or seven days after waterlogging with or without leaf removal. We found positive correlations between CO2 and N2O emissions and petiole and rhizome areas, indicating a size-dependent effect. Our results demonstrate that intact plants of G. tinctoria are a source of N2O emissions, which is enhanced, albeit transiently, by the removal of leaves. Consequently, management interventions on invasive plant populations that involve the removal of above-ground material, or waterlogging, would not only reduce CO2 uptake, but would further compromise the ecosystem GHG balance through enhanced N2O emissions.Brazilian Council of Science and Technology (CNPq

Interspecific Variations in the Growth, Water Relations and Photosynthetic Responses of Switchgrass Genotypes to Salinity Targets Salt Exclusion for Maximising Bioenergy Production

The expansion in the cultivation of bioenergy crops to saline lands is of importance for ensuring food security as long as high productivity is maintained. The potential of switchgrass to grow under saline conditions was examined in three genotypes from a early seedling growth to full maturity at 50, 100, 200 and 300 mM of sodium chloride (NaCl). The carbon assimilation rates were generally lower and correlated to stomatal closure in plants exposed to salinity in all the tested genotypes. Based on the results of ion concentrations in different parts of the plant, switchgrass genotypes differed in their responses to NaCl. The Alamo genotype excluded salt from the roots, whereas Trailblazer and Kanlow accumulated it in the root, stem and leaf tissues. The increased leaf salt concentration was accompanied by a higher proline concentration in the 200 and 300 mM NaCl treatments toward the end of the experiment. Overall, Alamo showed the highest yields at all salinity levels, indicating that excluding salt from the roots may result in a better performance in terms of biomass production. The accumulation of salt observed in Kanlow and Trailblazer resulted in lower yields, even when other mechanisms, such as the production of salt glands, were observed, especially in Kanlow. These results suggest that the Alamo genotype has the ability to maintain high yields under saline conditions and that this characteristic could be further exploited for maximizing bioenergy production under saline conditions.This work was funded by the FP7 OPTIMA project ‘Optimization of Perennial Grasses for Biomass production (Grant Agreement 289642)’

Monitoring of Engineering Applications

This paper presents a license monitoring system implemented at CERN in the Computing for Engineering (CE) group of the Information Technology (IT) division. The system gathers statistics on the use of the different software products supported by the group on both Windows and Unix platforms. The web is used for all aspects of the project; data presentation and associated interfaces. The system is completely automated. Manual intervention is required only when there are new products to be monitored. Certain technical details of this work have been reported elsewhere