The effects of clipping and soil moisture on leaf and root morphology and root respiration in two temperate and two tropical grasses

Summary

This comparative study examined how clipping (simulating grazing) and soil moisture stress affected root respiration and morphological traits in two temperate C₃ grasses (Festuca idahoensis, Poa pratensis) and two tropical C₄ grasses (Andropogon greenwayi, Sporobolus kentrophyllus) collected from their native ecosystems. Clipping had minimal effects on most traits, but reduced soil moisture significantly lowered root respiration in all species and triggered species-specific changes in leaf and root morphology. The findings suggest that soil moisture, rather than defoliation alone, is the primary driver of root carbon dynamics and structural adaptation in these grass species.

Regional applicability

Whilst the study used grasses collected from Yellowstone (temperate C₃ species) and the Serengeti (tropical C₄ species), the experimental design was controlled (greenhouse setting) rather than field-based in UK conditions. The temperate C₃ species findings may be partially relevant to UK grassland ecology, but direct application to UK farming systems would require validation under local soil moisture regimes and grazing pressures.

Key measures

Mass-specific root respiration (μmol CO₂ g⁻¹ s⁻¹), shoot and root biomass, leaf photosynthesis, specific leaf area (SLA), specific root length (SRL), root to shoot ratio (R:S)

Outcomes reported

The study measured mass-specific root respiration, shoot and root biomass allocation, leaf photosynthesis, specific leaf area (SLA), and specific root length (SRL) in response to clipping and variable soil moisture. Species-specific morphological responses to moisture stress were documented, with reduced soil moisture lowering root respiration across all four grass species tested.

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