Elevated CO2 and aboveground-belowground herbivory by the clover root weevil.

Area of Science:

• Ecology
• Environmental Science
• Agronomy

Background:

• Rising atmospheric carbon dioxide (CO(2)) may increase plant productivity, potentially leading to nitrogen limitation in terrestrial ecosystems.
• Legumes, like white clover (Trifolium repens), may mitigate nitrogen limitation through enhanced biological nitrogen fixation.
• The impact of elevated CO(2) on plant-herbivore interactions, particularly belowground, remains understudied.

Purpose of the Study:

• To investigate the effects of elevated CO(2) on the clover root weevil (Sitona lepidus), a key pest of white clover.
• To understand how elevated CO(2) influences the interaction between white clover, its nitrogen-fixing root nodules, and Sitona lepidus larvae.
• To assess the implications of these changes for biological nitrogen fixation under future climate scenarios.

Main Methods:

• Controlled environment experiment exposing white clover to elevated CO(2) (700 µL L⁻¹) and Sitona lepidus.
• Quantified changes in foliar and root C:N ratios, root mass, and nodule abundance.
• Assessed adult weevil feeding rates, egg production, and larval recovery and survival.

Main Results:

• Elevated CO(2) increased white clover root mass (85%) and nodule abundance (220%), but decreased foliar quality.
• Adult weevils consumed more leaf tissue but laid fewer eggs under elevated CO(2).
• Larval survival and abundance significantly increased under elevated CO(2), correlated with enhanced nodulation.

Conclusions:

• Elevated CO(2) disadvantages adult Sitona lepidus but benefits larvae due to increased root nodule availability.
• Enhanced nodulation under elevated CO(2) could increase biological nitrogen fixation in white clover.
• Increased Sitona lepidus larval populations may offset potential benefits of enhanced nitrogen fixation for agriculture and ecosystems.