Identifying pathways for managing multiple disturbances to limit plant invasions

Abstract

Summary1. Plant invasions are predicted to accelerate in a world with increased anthropogenic disturbance. Non-native species pre-adapted to these disturbances may especially be poised to invade novel communities. Conservation managers therefore need predictions of how to alter disturbances to maximize the persistence of native biodiversity. 2. We tested a multivariate hypothesis about the causal mechanisms underlying plant invasions in an ephemeral wetland in South Island, New Zealand, to inform management of this biodiverse but globally imperilled habitat. Our approach details among the first applications in ecology of Bayesian structural equation modelling, demonstrating its potential to inform management by disentangling the relative importance of strongly intercorrelated processes. 3. We found that invasion by non-native plants was lowest in sites where the physical disturbance caused by flooding was both intense and frequent. This effect was stronger than the positive response of non-native species to high soil N supply, which was positively related to flooding. 4. Sites flooded over a 4-year period had greater reductions in invasion than those associated with floods in the year prior to plot measurement because non-native species lacked traits for long-term persistence beneath water. Grazer exclusion had a small positive effect on invasion, as non-native species were preferentially selected by the herbivores at our site. 5. Our results show that only species adapted to the dominant disturbance regimes at a site may become successful invaders. Species native to ephemeral wetlands have specially evolved traits that allow them to persist and dominate in these sites. 6. Synthesis and applications. Predictions of invasions in a world of multiple disturbances clearly need to consider whether the evolutionary history of non-native species predisposes them to invade novel communities. Maintaining hydrological and nutrient regimes of ephemeral wetlands will limit the number of introduced species that are pre-adapted to become invasive.

The more we do, the less we gain? Balancing effort and efficacy in managing the Solidago gigantea invasion

“…In contrast to our findings, Tanentzap et al (2014)emphasised the importance of intensive disturbance regimes over intermediate ones in reducing invasion; we argue that the failure to substantially increase diversity and the associated increased potential for facilitating secondary invasion may outweigh the benefits gained by dramatically reducing the invaders’ abundance. In contrast to intensive treatments, management types with intermediate intensity have balanced effects: they decrease the invader's fitness, while potentially increasing the diversity of communities, which can be more effective for further sustainability in the invaded communities.…”

Invasive plant feedbacks promote alternative states in California vernal pools

“…Vernal pool ecosystems rely heavily on winter precipitation, experience relatively shallow inundation depths, and are attune to small variations in depth and duration (Holland & Jain ; Emery et al ; Gosejohan et al ) as well as inundation timing (Kneitel ). These inundation subtleties within the pool boundaries have been shown to exclude invasion by a number of species that are not adapted to such extreme conditions (Gerhardt & Collinge ; Tanentzap et al ). Our study demonstrated that the invasive pools contained the shallowest inundation depths regardless of variations in year.…”

Rapid change in forms of inorganic nitrogen in soil and moderate weed invasion following translocation of wet meadows to reclaimed post‐industrial land

“…A high groundwater table in the spring and in the first part of summer is a major disturbance factor in wet meadows. Maintenance of the hydrological and nutrient regimes of ephemeral wetlands limits the number of introduced species (Tanentzap et al, 2014). Adequate rewetting is necessary for the successful restoration of wetlands (Ramseier, Klötzli, Bollens, & Pfadenhauer, 2009).…”