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"Invasions"
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Pinus contorta invasions increase wildfire fuel loads and may create a positive feedback with fire
Invasive plant species that have the potential to alter fire regimes have significant impacts on native ecosystems. Concern that pine invasions in the Southern Hemisphere will increase fire activity and severity and subsequently promote further pine invasion prompted us to examine the potential for feedbacks between Pinus contorta invasions and fire in Patagonia and New Zealand. We determined how fuel loads and fire effects were altered by P. contorta invasion. We also examined post-fire plant communities across invasion gradients at a subset of sites to assess how invasion alters the post-fire vegetation trajectory. We found that fuel loads and soil heating during simulated fire increase with increasing P. contorta invasion age or density at all sites. However, P. contorta density did not always increase post-fire. In the largest fire, P. contorta density only increased significantly post-fire where the pre-fire P. contorta density was above an invasion threshold. Below this threshold, P. contorta did not dominate after fire and plant communities responded to fire in a similar manner as uninvaded communities. The positive feedback observed at high densities is caused by the accumulation of fuel that in turn results in greater soil heating during fires and high P. contorta density post-fire. Therefore, a positive feedback may form between P. contorta invasions and fire, but only above an invasion density threshold. These results suggest that management of pine invasions before they reach the invasion density threshold is important for reducing fire risk and preventing a transition to an alternate ecosystem state dominated by pines and novel understory plant communities.
Journal Article
Mutualistic Interactions and Biological Invasions
Mutualisms structure ecosystems and mediate their functioning. They also enhance invasions of many alien species. Invasions disrupt native mutualisms, often leading to population declines, reduced biodiversity, and altered ecosystem functioning. Focusing on three main types of mutualisms (pollination, seed dispersal, and plant-microbial symbioses) and drawing on examples from different ecosystems and from species- and community-level studies, we review the key mechanisms whereby such positive interactions mediate invasions and are in turn influenced by invasions. High interaction generalization is \"the norm\" in most systems, allowing alien species to infiltrate recipient communities. We identify traits that influence invasiveness (e.g., selfing capacity in plants, animal behavioral traits) or invasibility (e.g., partner choice in mycorrhizas/rhizobia) through mutualistic interactions. Mutualistic disruptions due to invasions are pervasive, and subsequent cascading effects are also widespread. Ecological networks provide a useful framework for predicting tipping points for community collapse in response to invasions and other synergistic drivers of global change.
Journal Article
Alien invaders : species that threaten our world
Explores the history of alien invaders--plants, animals, bacteria, or viruses that are deliberately or accidentally introduced to a new habitat, and subsequently explode in numbers causing harm to property and wildlife; features case studies of such species; and discusses what can be done to halt the progress of alien invaders.
Book
Key moments from the third day of the Russian invasion of Ukraine
On Feb. 26, explosions and widespread damage were seen on the streets of Ukraine as Russia continued its country-wide attack.
Streaming Video
Biden: Russian forces ‘intend to attack Ukraine’
On Feb. 18, President Biden said that Russia has plans to attack Ukraine “in the coming days,” targeting Ukraine's capital, Kyiv.
Streaming Video
'Ukraine has tried to turn itself in porcupine': How Ukraine could defend against Russia invasion
Washington Post opinion columnist James Hohmann tells reporter Libby Casey how Ukraine could try to defend itself against a Russian invasion.
Streaming Video