No abstract

Populations of invasive alien plants create disruptive plant communities that are extremely adaptable, imposing severe ecological impacts on agriculture, biodiversity and human activities. To minimise these impacts, prevention and effective weed management strategies are urgently required, including the identification of satellite populations before they invade new areas. This is a critical element that allows weed management practices to become both successful and cost-effective. Mimosa pigra L. (Giant sensitive plant) is an invasive weed that has spread across various environments around the world and is considered one of the world’s top 100 most invasive plant species. Being adaptable to a wide range of soil types, in addition to its woody protective prickles and low palatability, M. pigra has quickly spread and established itself in a range of habitats. Current control methods of this species include biological, chemical and physical methods, together with attempts of integrated application. Reports suggest that integrated management appears to be the most effective means of controlling M. pigra since the use of any single method has not yet proved suitable. In this regard, this review synthesises and explores the available global literature and current research gaps relating to the biology, distribution, impacts and management of M. pigra. The contribution of this work will help guide land managers to design appropriate and sustainable management programs to control M. pigra.

Amaranthus retroflexus L. (Amaranthaceae), Redroot pigweed, is native to North America, but has become a weed of agriculture worldwide. Previous research into competition with food crops found it significantly reduces yields. Additionally, taxonomy, biomass allocation, physiological responses to light intensity, water stress, elevated CO2, and herbicide resistance have been investigated. To extend other research findings, we investigated growth and biomass yield in response to (i) soil moisture stress, and (ii) drought and elevated CO2. Additionally, we investigated seed germination rates following exposure to three elevated temperatures for two different time periods. Overall, moisture stress reduced plant height, stem diameter, and number of leaves. Elevated CO2 (700 ppm) appeared to reduce negative impacts of drought on biomass productivity. Heating seeds at 120 °C and above for either 180 or 300 s significantly reduced germination rate. These results inform an understanding of potential responses of A. retroflexus to future climate change and will be used to predict future occurrence of this weed. The finding that exposing seeds to high temperatures retards germination suggests fire could be used to prevent seed germination from soil seed banks, particularly in no-till situations, and therefore may be used to address infestations or prevent further spread of this weed.

Acacia longifolia subsp. longifolia is native to South-eastern Australia and has naturalised in many regions across the globe, including in Portugal, Spain, and South Africa invading extensive areas. Prolific seed production and a long-lived seedbank are considered key factors that enhance its invasiveness. Yet, the effects of different factors on germination are still underexplored. Seeds were collected from Portuguese and Australian populations, and germination was evaluated under different temperature regimes, photoperiods, pH levels, salt stress, osmotic potential and burial depths. Findings show both populations share some similar patterns but also reveal important differences related to their germination. Higher temperatures induce increased germination rates while the photoperiod has no effect on germination. Both populations had quicker seed emergence under dark conditions. Seeds from both populations decrease germination rate under increasing salt-stress and show a wide range of pH tolerance, but Australians seeds are more tolerant to increase of both parameters. Seeds from the Portuguese population are bigger and germinated from deeper depths than the Australian. Our results may provide information to improve management of this species seedbank. Germination can prevent by, tillage or other interventions that help to increase burial depths; adding lime (to increase the soil alkalinity) can reduce its germination rate in both geographical ranges.