Global change stressors alter resources and shift plant interactions from facilitation to competition over time
Alba, C., Fahey, C., & Flory, S. L. (2019). Global change stressors alter resources and shift plant interactions from facilitation to competition over time. Ecology, e02859. PDF.
Summary
Non-native plant invasions can have significant impacts on native ecosystems that may be exacerbated by climate change. Altered precipitation patterns, such as more frequent and severe drought, could increase susceptibility to plant invasion. But, the combined effects of drought and invasion on native communities are rarely tested experimentally. Fahey et al. 2018 and Alba et al. 2019 assess the individual and combined effects of drought and invasion by cogongrass (Imperata cylindrica) in longleaf pine forests of the southeastern U.S. Longleaf pine forests, which support high levels of diversity and endemism, were the dominant ecosystem in the southeastern U.S. but have been reduced to less than 3% of their historical extent.
Fahey et al. (2018) experimentally tested the independent and interactive effects of cogongrass invasion and drought on longleaf pine forest ecosystems. Individually, the effects of invasion (60% decline in native plant diversity) were more severe than the effects of drought (20% decline in native plant diversity). In combination, the invader ameliorated the drought by increasing soil moisture under drought conditions. As a result, plant diversity was reduced by 60% with invasion regardless of the drought treatment. Initially for longleaf pine survival, invasion and drought completely offset one another so that survival was equivalent in the invaded drought plots and the uninvaded ambient plots. However, Alba et al. 2019 showed that over time the invader goes from facilitating pine seedlings by retaining higher soil moisture to excluding pine seedlings in competition for light.
Take home points
Drought does not make the impacts of cogongrass invasion worse, but the effects of cogongrass are pretty bad to begin with.
Both invasion and drought severely reduce plant diversity and the survival of longleaf pines.
Management implications
Management strategies will need to consider plant invasion and altered precipitation regimes as barriers to restoration of natural ecosystems and forestry operations.
Long-term monitoring is important because the interactions between invaders and climate change factors may change over time.
Keywords
Climate Extremes; Competitiveness; Impact Study; Experiment; Invasive Plant; Terrestrial Habitat; Imperata cylindrica; Congograss