Assessing restoration potential of a critically endangered vegetation type following alien acacia removal

The Fynbos vegetation of the Cape Lowlands is ecologically distinct from mountain Fynbos within the Cape Region of South Africa, but has been highly impacted by agriculture and urban development, while alien plants have invaded most of the remaining natural habitats. Cape Flats Sand Fynbos is a critically endangered lowland vegetation type containing many endemic and threatened species. 100 ha of this vegetation type which was invaded by alien Acacia saligna was cleared in 2012. The standard clearing methods utilised in Lowland Fynbos have resulted in poor native vegetation recovery. Therefore this study aimed to test novel passive (burning) and active (seed sowing) treatments on recovery of native vegetation. After two years all treatments resulted in different recovery trajectories, and modelling treatment responses showed these trajectories to be maintained in the long-term. The passive clearing without burning treatment resulted in herbaceous vegetation dominating, while the active treatment resulted in higher cover, species richness and density of non-sprouting shrubs. A follow-up sowing treatment involving seed pre-treated with smoke and heat improved shrub species richness and seedling density of certain species, especially Thamnochortus punctatus, a dominant structural component species. Therefore an active treatment involving sowing pre-treated seeds after clearing and burning results in best Fynbos recovery compared to either of the passive treatments tested. These restoration methods should be adaptable to other lowland vegetation types within the Fynbos region as well as other Mediterranean climate regions

Active seed sowing can overcome constraints to passive restoration of a critically endangered vegetation type

Invasive alien plants negatively impact ecosystems, but recovery of native vegetation may fail following standard methods of alien species removal alone. Alternative management actions may thus be required. Cape Flats Sand Fynbos is a critically endangered vegetation type in the Cape Floristic Region of South Africa which is threatened by Acacia saligna invasion, but standard clearing methods have failed to restore native vegetation structure. A restoration study was performed comparing passive treatments i.e. clearing without burning (stack-block) versus clearing and burning (burn-block), as well as active intervention by sowing seeds of native species, either initially after burning or a year later, in which seeds were either not pre-treated or pre-treated with smoke and heat exposure before sowing. After two years all treatments resulted in different recovery trajectories, although none resembled the reference condition. Clearing without burning facilitated recovery in less degraded areas with higher initial native shrub cover, but otherwise resulted in limited vegetation recovery. Limited recovery facilitated secondary invasion by herbaceous weeds. Active seed sowing resulted in the highest recovery of native shrub cover and diversity. These findings suggest that passive restoration is constrained by seed limitation, due to the lack of recovery of vegetation components under passive clearing treatment. Active sowing was able to partially overcome this constraint through improved recovery of total shrub cover. However, non-sprouting shrub cover was higher while resprouting shrubs and species of Restionaceae were lower compared to the reference condition. Pre-treatment of seeds before sowing improved establishment of some species. Active treatment involving sowing pre-treated seeds after clearing and burning therefore resulted in best fynbos recovery compared to either of the passive treatments tested. A decision tree has been developed based on these findings in order to guide best protocol for managers

Assessment of post-burn removal methods for Acacia saligna in Cape Flats Sand Fynbos, with consideration of indigenous plant recovery

The Greater Cape Floristic Region (GCFR) of South Africa is a biodiversity hotspot threatened by the impacts of habitat transformation and invasive alien species. Cape Flats Sand Fynbos (CFSF) is a critically endangered vegetation type occurring within the GCFR, and its largest remaining fragment is the focus of a large-scale invasive plant control and biodiversity restoration project. Acacia saligna is a highly problematic invasive in CFSF and the main target of the control. To mitigate damage caused by this species, stands are removed and burned, which stimulates both the large invasive seed-bank and the indigenous seed-bank in the soil. Although there are no clear methods on how to manage the re-invasion at this stage without damaging indigenous plant recovery, three post-burn removal methods have the potential to be effective: (1) cutting the Acacia saplings below the coppicing point, (2) cutting the saplings and applying herbicide to the stumps, and (3) foliar herbicide spray. The aims of this studywere to (i) find the most effective post-burn A. saligna control treatment, (ii) find the treatment that causes the least harm to indigenous plant recovery, (iii) determine the most cost-effective treatment, and (iv) establish which treatment is the most suitable for large-scale use. Cutting below the coppicing point of the A. saligna provided the most effective removal and was also the least damaging to indigenous vegetation recovery. The foliar spray treatment, however, saved the most time and costs. The best method is therefore dependent on the project goals, scale, and density of the A. saligna invasion. These results may be applicable to other types of fynbos and to other fire-stimulated invasive Acacia species

Encrypted accelerated least squares regression.

Information that is stored in an encrypted format is, by definition, usually not amenable to statistical analysis or machine learning methods. In this paper we present detailed analysis of coordinate and accelerated gradient descent algorithms which are capable of fitting least squares and penalised ridge regression models, using data encrypted under a fully homomorphic encryption scheme. Gradient descent is shown to dominate in terms of encrypted computational speed, and theoretical results are proven to give parameter bounds which ensure correctness of decryption. The characteristics of encrypted computation are empirically shown to favour a non-standard acceleration technique. This demonstrates the possibility of approximating conventional statistical regression methods using encrypted data without compromising privacy

Impacts of invasive alien trees on threatened lowland vegetation types in the Cape Floristic Region, South Africa

This study investigated the autogenic recovery potential of native vegetation after clearing of dense stands of invasive alien trees in two critically endangered vegetation types in South Africa's Cape Floristic Region: Cape Flats Lowland Fynbos and Swartland Alluvium Fynbos. Sampling was done in areas previously occupied by the invasive tree Acacia saligna and plantations of Pinus radiata and in a fynbos reference site. Treatments varied in terms of the length of invasion and management histories. Plots previously under pines recovered well in terms of indigenous perennial species richness, but indigenous species cover decreased with increasing number of planting rotations. Areas cleared of acacia recovered poorly in terms of indigenous species cover (after one cycle of invasion), and indigenous species richness exhibited a declining trendwith increasing cycles of invasion. Proteoid overstoreywas lost in all previously invaded/planted plots and this elementwill need to be re-introduced to areas after one cycle of invasion regardless of the invasive species. Acacias changed some abiotic variables after two cycles of invasion. Follow-up clearing generally promoted better vegetation recovery in terms of overall species richness and structure but care should be taken not to damage indigenous ericoid shrubs. Overall, acacia invasion caused a greater change in biodiversity and vegetation structure than pine plantations

Simulation of Beam-Beam Effects and Tevatron Experience

Effects of electromagnetic interactions of colliding bunches in the Tevatron had a variety of manifestations in beam dynamics presenting vast opportunities for development of simulation models and tools. In this paper the computer code for simulation of weak-strong beam-beam effects in hadron colliders is described. We report the collider operational experience relevant to beam-beam interactions, explain major effects limiting the collider performance and compare results of observations and measurements with simulations.Comment: 23 pages, 17 figure

The impact of pine plantations on fynbos above-ground vegetation and soil seed bank composition

Pine plantations and pine invasions have numerous impacts on native ecosystems in the Fynbos biome of South Africa. The severity of these impacts greatly determines the extent of potential ecosystem recovery after the pines are felled. The recovery potential of fynbos after felling of pine plantations of varying longevity and the subsequent application of ecological burns was investigated in the Helderberg Nature Reserve, Western Cape Province, South Africa. Above-ground vegetation, soil seed bank and abiotic variables were sampled across three treatments (reference fynbos and sites that had been under pines for 30 and 50 years respectively) using 1 m2 quadrats placed along 50 m line transects. The soil seed bank samples were smoke treated and then monitored in a greenhouse to determine the soil seed bank species and growth form composition. Areas previously under 30 year old pine plantations had high native species and growth form density (number of species/growth forms per unit area) and similar plant density (number of individuals per unit area) to the reference fynbos areas. Conversely, areas previously under 50 year old pine plantations had significantly lower native species and growth form density and plant density than the reference fynbos andwere dominated by alien species. In addition, areas previously under 50 year old pine plantations had lower species diversity than the reference fynbos areas and areas previously under 30 year old pine plantations which were found to be similar to one another. Felled pine plantations were shown to minimally impact on soil abiotic variables, with only soil temperature and pH showing significant differences. Therefore, areas previously under 30 year old pine plantations have higher recovery potential following pine removal than 50 year old plantations, owing to the depleted native soil seed bank in the latter. Consequently, active restoration may be needed to re-introduce the missing long-lived growth forms and to prevent soil erosion. Pine plantation and invasion management in the Fynbos biome should aim to fell pines before the native seed bank is depleted to maintain the recovery potential of fynbos and prevent the need for active restoration

An eight-year climatology of the martian northern polar vortex

The martian polar atmosphere is characterised by the presence of polar vortices, regions of cold and isolated air over the winter poles common to planetary atmospheres. The polar vortices have important meteorological effects via their interactions with atmospheric tracers and the broader circulation. In turn, they have been shown to be affected by large atmospheric dust loadings such as from dust storms. We make use of an extensive reanalysis dataset of Mars’ weather and climate (Open access to Mars Assimilated Remote Soundings; OpenMARS) to investigate the seasonal and interannual behaviour of Mars’ northern polar vortex over eight recent martian years, Mars Years (MY) 28–35 (2006–2021). We find that the northern polar vortex shows a high degree of interannual repeatability in its structure and evolution, with the key exception of during the presence of large (regional and global scale) dust storms. Such storms cause significant perturbations to the northern polar vortex, compressing it towards the pole and reducing its radius. However, not all dust storms have equal impacts. We find that the seasonal timing of large dust storms appears to be the key factor determining their impacts on the northern polar vortex. Storms occurring closer to southern summer solstice have greater impacts than those occurring closer to equinox. We propose that this seasonal dependence is due to the structure of the background meridional circulation, which is at its greatest strength and latitudinal extension around southern summer solstice. The enhancement of this existing circulation by dust-induced heating allows greater impacts if the circulation is already stronger and more latitudinally extended, and impacts are likewise lesser if the storm occurs during a period with a weaker and less latitudinally extended circulation

What is embodiment? a psychometric approach

What is it like to have a body? The present study takes a psychometric approach to this question. We collected structured introspective reports of the rubber hand illusion, to systematically investigate the structure of bodily self-consciousness. Participants observed a rubber hand that was stroked either synchronously or asynchronously with their own hand and then made proprioceptive judgments of the location of their own hand and used Likert scales to rate their agreement or disagreement with 27 statements relating to their subjective experience of the illusion. Principal components analysis of this data revealed four major components of the experience across conditions, which we interpret as: embodiment of rubber hand, loss of own hand, movement, and affect. In the asynchronous condition, an additional fifth component, deafference, was found. Secondary analysis of the embodiment of runner hand component revealed three subcomponents in both conditions: ownership, location, and agency. The ownership and location components were independent significant predictors of proprioceptive biases induced by the illusion. These results suggest that psychometric tools may provide a rich method for studying the structure of conscious experience, and point the way towards an empirically rigorous phenomenology

Laser-sheet imaging of HE-driven interfaces

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors made substantial progress in developing the MILSI (Multiple Imaging of Laser-Sheet Illumination) technique for high explosive (HE)-driven fluid interfaces. They observed the instability, but have not yet measured the instability growth rate. They developed suitable sample containers and optical systems for studying the Rightmyer-Meshkov instability of perturbed water/bromoform interfaces and they successfully fielded the new MILSI diagnostic at two firing-site facilities. The problem continues to be of central importance to the inertial confinement fusion (ICF) and weapons physics communities