Experimenting with methods to control Tradescantia fluminensis, an invasive weed of native forest remnants in New Zealand

Tradescantia fluminensis, commonly referred to as 'tradescantia', is an invasive weed of canopydepleted forest remnants. Previous research suggests that a reduction of tradescantia biomass to ~80 gm-2 (~40% cover) is compatible with native forest regeneration. I assessed herbicide application, hand weeding and artificial shading as methods for the control of tradescantia in two lowland podocarp/broad-leaved forest remnants in the lower North Island of New Zealand. Herbicide spray and hand weeding, applied to separate experimental plots, did not prevent re-growth of tradescantia after three successive treatments. Re-growth of tradescantia and invasion of other weeds were positively related to light availability, which increased in the more canopy-depleted areas, and negatively related to native forest regeneration measured two years after initial treatment. Artificial shading was the most effective method of control. The biomass of tradescantia was significantly reduced in artificially-shaded plots (2-5% full light; 81.3 ± 10.6 gm-2) relative to non-shaded plots (15-27% full light; 597.6 ± 6.6 gm-2; t4 = 17.38, P< 0.001) after 17 months. Native sub-canopy species were planted into tradescantia to achieve natural shading over large areas of forest. After 2.5 years, 61% of the saplings planted had emerged from the surrounding tradescantia

Incorporating novelty and novel ecosystems into restoration planning and practice in the 21st century

Novelty pervades the biosphere. In some cases, potentially irreversible abiotic and/or biotic changes have led to the crossing of thresholds and thus the formation of “novel ecosystems.” Their widespread emergence (particularly on land) and the presence of continued environmental change challenge a traditional restoration goal of restoring an historical ecosystem. Instead, we argue that restoration could broaden its frame of reference to consider how novel ecosystems might be used to maintain global biodiversity and provide ecosystem services and, in doing so, save potentially wasted efforts in attempting to fulfil traditional goals. Here we explore this contention in more depth by addressing: Are novel ecosystems innovative planning or lowering the bar? We show that novel ecosystems were not innovative planning in their original conception. On the contrary, they were recognized as ecosystems that were recalcitrant to traditional restoration approaches, coupled with an awareness that they had arisen inadvertently through deliberate human activity, either on- or off-site. Their recalcitrance to traditional restoration suggests that alternative goals may exist for these ecosystems using sometimes innovative intervention. This management may include biodiversity conservation or restoration for ecological function. We elucidate the latter aspect with reference to an experiment in the wheatbelt of Western Australia—The Ridgefield Multiple Ecosystem Services Experiment—the design of which has been informed by ecological theory and the acceptance of novelty as an ecosystem component. Although novel ecosystems do provide opportunities to broaden restoration planning and practice, and ultimately maintain and conserve global biodiversity in this era of environmental change, they necessarily “lower the bar” in restoration if the bar is considered to be the historical ecosystem. However, in these times of flux, such a bar is increasingly untenable. Instead, careful and appropriate interventions are required at local, regional, and global scales. These interventions need to take history into account, use ecological and evolutionary theory to inform their design, and be mindful of valid concerns such as hubris. Careful interventions thus provide an opportunity for broadening restoration’s framework to focus on maintaining global biodiversity and delivering ecosystem services as well as the traditional goals of restoring historical ecosystems

Effects of rodent poisoning on Powelliphanta traversi

Rat predation is a threat to lowland Powelliphanta traversi (giant predatory land snail), and we have shown that ‘press’ poisoning of rodents (rats and mice) using brodifacoum baits significantly reduces rat abundance relative to non-poisoned areas. The effect on P. t. traversi was evident by the increase in population size, mainly due to adult migration, and a decrease in rat-damaged shells, for areas where rat predation occurs. A longer-term study is required to determine whether prolonged rat control benefits P. t. traversi recruitment. Mouse control was inadequate with use of brodifacoum baits. We document a concomitant rise in bird predation of P. traversi when rat abundance was reduced, suggesting that control of both is necessary to make real conservation gains. However, mortality related to other factors was more common than that caused by predators, possibly due to the habitat drying out periodically. We suggest that low recruitment rates, predator targeting of juveniles (i.e. blackbirds, song thrush and possibly mice and hedgehogs) and poor habitat conditions are the main threats to survival of lowland P. traversi

Habitat use of Tradescantia fluminensis by Powelliphanta traversi

This study was initiated owing to concern that removal of the invasive ground cover, Tradescantia fluminensis, might adversely effect the rare, giant predatory land snail, Powelliphanta traversi. Of 18 sites surveyed in the Horowhenua District, seven sites provide habitat for P. traversi and do not contain Tradescantia. Five colonies of P. traversi are affected by Tradescantia, these are: Waiopehu Scenic Reserve, Prouse’s Bush, Kimberley Scenic Reserve, Ohau River Bush, and Hillas Covenant. Tradescantia infestation at these sites varies from heavy (Prouse’s Bush) to forest edge only (Hillas Covenant). Overall, Tradescantia affects a small proportion of snail habitat in the Horowhenua District. Our study of P. traversi at Prouse’s Bush, using harmonic radar to follow long-term movements and cotton tracks for short-term movements, indicates that this snail commonly occurs under Tradescantia, sometimes exclusively, and that many of the snails move regularly between leaf litter and this weed. Moreover, Tradescantia provides an important refuge for juvenile snails at Prouse’s Bush. Hence, removing Tradescantia from this site would have a detrimental impact on P. traversi. Graduated control of Tradescantia and concomitant replacement with native ground cover could be of mutual benefit to P. traversi and other ground-dwelling invertebrates

Genetic differentiation, reproductive mode, and gene flow in the brooding coral Pocillopora damicornis along the Great Barrier Reef, Australia

The widespread and morphologically variable coral Pocillopora damicornis has been reported to exhibit huge variation in life-history traits (e.g. mode of reproduction, growth rate, longevity and dispersal) both locally and regionally throughout the Indo-Pacific Ocean. Dispersal may be achieved by the settlement of sexually or asexually generated brooded planula larvae, by broadcast spawning or more locally through asexual fragmentation of large colonies. In the present study, we conducted a hierarchical survey of allozyme variation within and among reef-crest sites on 3 mid-shelf reefs separated by up to 1200 km on the Great Barrier Reef (GBR), Australia. Our objective was to use allozyme data (1) to quantify local and regional patterns of variation in P. damicornis (along the northeastern coast of Australia), (2) to determine the relative contribution of sexual versus asexual production of planulae in P. damicornis, and (3) to estimate levels of gene flow among adjacent sites (>5 km apart) and among reefs separated by 500 to 1200 km. High levels of genotypic diversity in our samples of P. damicornis imply that dispersive propagules in this species are produced sexually rather than asexually along the length of the GBR. Corals at all sites displayed the same level of multi-locus genotypic diversity expected for randomly mating, sexually derived populations, and the majority of individual colonies possessed unique 7-locus genotypes. We also detected consistent deficits of heterozygotes within each collection (from 3 local sites on each of the 3 widely spaced reefs). This pattern is consistent with the predicted effects of sexual reproduction associated with some localised dispersal of gametes or larvae (although other explanations cannot be excluded). Furthermore, each reef was genetically subdivided, suggesting that larval recruitment was localised and that these populations are slightly inbred: hierarchical analysis of the standardised genetic variances (FST)(estimated as Weir & Cockerham's Θ) revealed that, although there was only moderate variation among all 9 sites (FST = 0.055 ± 0.029), more variation was found among sites within reefs (FSL= 0.035 ± 0.04 to 0.088 ± 0.033) than among distant reefs (FLT= 0.008 ± 0.014). This homogeneity of gene frequencies across widely separated reefs implies that reefs are connected by high levels of gene flow (Nem = ca 31) and that local populations of P. damicornis separated by >1000 km can interbreed sufficiently to maintain a consistent suite of life-history characters

Canary in the coal mine: Lessons from the Jarrah Forest suggest long-term negative effects of phosphorus fertilizer on biodiverse restoration after surface mining

Despite nutrient enrichment having widely reported negative impacts on biodiversity, fertilizer is routinely applied in post mining restoration to enhance plant growth and establishment. Focusing on surface mine restoration (predominately bauxite and mineral sands), we outline the long-term negative impacts of fertilizer, particularly phosphorus fertilizer, on plant community composition, species richness, fire fuel loads, and belowground impacts on nutrient-cycling. We draw from extensive research in south-western Australia and further afield, noting the geographical coincidence of surface mining, phosphorus impoverished soil and high plant biodiversity. We highlight the trade-offs between rapid plant-growth under fertilisation and the longer-term effects on plant communities and diversity. We note that the initial growth benefits of fertilisation may not persist in water-limited environments: growth of unfertilised forests can eventually match that of fertilised forest, throwing doubt on the premise that fertilisation is necessary at all

Evaluating conservation strategies for the endangered daisy Schoenia filifolia subsp. subulifolia (Asteraceae): fitness consequences of genetic rescue and hybridisation with a widespread subspecies

Context: To establish translocated populations of threatened plants with the genetic resources to adapt to changing environmental conditions, the source of propagation material is an important consideration. Aim: We investigated the fitness consequences of genetic rescue and admixture for the threatened annual daisy Schoenia filifolia subsp. subulifolia, and the common S. filifolia subsp. filifolia, to inform seed-sourcing strategies for translocations of the threatened subspecies. Methods: We evaluated genetic diversity of two populations of S. filifolia subsp. subulifolia and four populations of S. filifolia subsp. filifolia by using microsatellite markers. We grew seedlings from each study population and cross-pollinated inflorescences within and among populations of the same subspecies, and between subspecies. We evaluated the fitness consequences of each cross by using seed set, seed weight and seed viability. Key results: There was a lower genetic diversity in the small (10 000 plants, Nar = 4.42, He = 0.51) population of S. filifolia subsp. subulifolia, although none of the measures was significantly different, and seed fitness was slightly, although not significantly, reduced in interpopulation crosses compared with the small population. Genetic diversity was similar between the threatened and widespread subspecies; however, the subspecies were genetically divergent (Fst = 0.242–0.294) and cross-pollination between subspecies produced negligible amounts of seeds (<3% seed set). Conclusions: Although genetic rescue or admixture of S. filifolia subsp. subulifolia would not necessarily result in greatly increased levels of genetic diversity or seed fitness, we still consider it a potential option. Negligible seed set in crosses between subspecies indicates that deliberate hybridisation is not a possibility. Implications: Studies of fitness consequences of admixture or genetic rescue are rare yet critical to assessing the benefits of different translocation strategies

Threats to biodiversity from cumulative human impacts in one of North America's last wildlife frontiers

Land‐use change is the largest proximate threat to biodiversity yet remains one of the most complex to manage. In British Columbia (BC), where large mammals roam extensive tracts of intact habitat, continued land‐use development is of global concern. Extant mammal diversity in BC is unrivalled in North America owing, in part, to its unique position at the intersection of alpine, boreal, and temperate biomes. Despite high conservation values, understanding of cumulative ecological impacts from human development is limited. Using cumulative‐effects‐assessment (CEA) methods, we assessed the current human footprint over 16 regional ecosystems and 7 large mammal species. Using historical and current range estimates of the mammals, we investigated impacts of human land use on species’ persistence. For ecosystems, we found that bunchgrass, coastal Douglas fir, and ponderosa pine have been subjected to over 50% land‐use conversion, and over 85% of their spatial extent has undergone either direct or estimated indirect impacts. Of the mammals we considered, wolves were the least affected by land conversion, yet all species had reduced ranges compared with historical estimates. We found evidence of a hard trade‐off between development and conservation, most clearly for mammals with large distributions and ecosystems with high levels of conversion. Rather than serve as a platform to monitor species decline, we strongly advocate these data be used to inform land‐use planning and to assess current conservation efforts. More generally, CEAs offer a robust tool to inform wildlife and habitat conservation at scale

Phosphorus supply affects seedling growth of mycorrhizal but not cluster-root forming jarrah-forest species

Aims Fertiliser is often used to kick-start ecological restoration despite growing evidence of the potentially negative impacts on plant diversity. Jarrah (Eucalyptus marginata) forest species growing on nutrient (especially phosphorus) impoverished soils in southwestern Australia have a suite of adaptations for phosphorus (P) acquisition, including the formation of cluster roots, and associations with mycorrhizal fungi. Here we investigated how escalating P supply, along with a stoichiometric adjustment of nitrogen (N) supply, impacted the growth and nutrition of a wide range of jarrah forest seedlings. Methods In a pot experiment, we measured seedling biomass and nutritional responses of 12 jarrah forest species to a gradient of P supply in relation to N supply, and for the mycorrhizal species, inoculation with arbuscular mycorrhizal fungi. Results Three cluster-root forming species did not respond to increasing P, probably because they were reliant on seed P. Generally, mycorrhizal species showed a positive biomass response to increasing P when N was available. Mycorrhizas benefited seedling growth at low P (9 mg P added per kg of jarrah forest soil) when N was also available, and were parasitic to seedling growth at high P (243 mg P/ kg soil) without additional N. Conclusions These results highlight importance of P and N supply in determining the nature of the symbiosis between plants and mycorrhizal fungi. Since P supply has the potential to reduce plant growth, for a range of species, our results suggest careful consideration of fertiliser amounts for ecological restoration of ecosystems adapted to nutrient poor soils

Optical fiber fabrication using novel gas-phase deposition technique

We report a highly versatile chemical-in-crucible preform fabrication technique suitable for gas-phase deposition of doped optical fibers. Aluminosilicate and ytterbium-doped phosphosilicate fibers are presented demonstrating the technique and its potential for realizing complex fiber designs that are suitable for the next generation of high-power fiber devices. The results show aluminum-doped fiber with numerical aperture of 0.28 and ytterbium-doped fiber with a measured slope efficiency of 84% with respect to pump launch power