Invasive species do not exploit early growing seasons in burned tallgrass prairies

Area of Science:

• Prairie Ecology
• Invasive Species Management
• Climate Change Ecology

Background:

• Native prairie ecosystems face threats from invasive species, necessitating effective management strategies.
• Prescribed burning is a known method for increasing native plant diversity and controlling invasive species.
• Climate change is altering growing season timing, potentially impacting invasive species success and management outcomes.

Purpose of the Study:

• To investigate the effects of prescribed burning and growing season start time on invasive species cover and frequency.
• To understand the interaction between burning and growing season phenology in prairie ecosystems.
• To assess the continued utility of prescribed burning as a conservation tool under changing climate conditions.

Main Methods:

• Analysis of 853 observations from 267 transects across 25 prairie sites in Minnesota (2010-2019).
• Estimation of the impact of burning, growing season start time, and their interaction on invasive species metrics.
• Focus on relative cover and frequency as measures of invasive species abundance and dominance.

Main Results:

• Prescribed burning significantly reduced the abundance of invasive cool-season grasses and overall invasive species cover.
• The suppressive effect of burning on invasive cover persisted over time, though frequency reduction was short-lived.
• Contrary to expectations, later growing season starts increased some invasive species abundance, while earlier starts slightly reduced burn effectiveness on key invasive grasses like Kentucky bluegrass and smooth brome.

Conclusions:

• Prescribed burning remains an effective conservation tool for managing invasive species in prairie ecosystems, even with earlier growing seasons.
• Changes in growing season timing due to climate change are unlikely to be the primary driver of increased invasion in these systems.
• Further research should explore abiotic factors influencing invasive species phenology and the interaction of burn characteristics with spring conditions.