Experimental drought and plant invasion additively suppress primary pine species of southeastern US forests
NeSmith, J. E., Alba, C., & Flory, S. L. (2018). Experimental drought and plant invasion additively suppress primary pine species of southeastern US forests. Forest Ecology and Management, 411, 158-165. PDF.
Summary
Stress on native pine communities is expected to intensify due to increases in drought and plant invasion. However, it is unclear if these multiple stressors interact or are simply additive. Interactions could be synergistic (amplifying one another’s impacts) or offsetting (reducing one another’s impacts). To investigate the impacts of these multiple stressors, NeSmith et al. 2018 conducted a common garden experiment in which they added the invasive plant cogongrass (Imperata cylindrica), drought conditions, or a combination of drought and invasion to plots containing two economically important native pine species, South Florida slash pine (Pinus elliottii var. densa) and loblolly pine (Pinus taeda). For both pine species, they found drought had a negative effect on height, invasion had a negative effect on seedling survival, and the two stressors worked additively to negatively affect tree diameter. Although both pine species responded negatively to invasion and drought, individual responses varied with slash pine exhibiting greater negative effects to biomass than loblolly pine. While the authors did find some support that cogongrass could mitigate drought by increasing soil moisture (offsetting), other negative impacts of cogongrass (such as light competition) negated any positive impacts on pine growth and survival via drought mitigation. Therefore, the authors suggest the independent effects of stressors added together are likely indicative of how multiple stressors may impact native communities. While this study finds that climate change and invasion work independently to impact native pine forests, the magnitude of this impact is contingent on the species composition of the native community.
Take home points
Drought and plant invasion acted additively to negatively impact two native pine species, suggesting the independent effects of these stressors are a good metric for predicting impacts to native communities when both stressors are present.
Management implications
Consider native species’ distinct life histories when predicting impacts from climate change and plant invasion. In this study, the authors use a variant of Pinus elliottii that has a unique seedling life stage compared to the more widely distributed variant. Therefore, it may respond differently to the climate change and invasion stressors.
Plant drought tolerant variants of native species to help increase resilience in areas where increased drought is projected.
Communicate potential economic consequences (e.g., timber loss in impacted pine communities) to motivate land owners to remove invasive species.
Keywords
Climate Extremes; Range Expansion; Impact Study; Experiment; Invasive Plant; Terrestrial Habitat; Imperata cylindrica; Congograss