Short-Term Effects of Contrasting Management Regimes on Plant Species Diversity, Herbage Production and Soil CO2 Emissions in Species-Rich Grasslands

Semi-natural grasslands are among the most plant-rich ecosystems worldwide, providing multiple ecosystem services but requiring site-specific management for their conservation. This study assessed short-term dynamics of plant biodiversity, herbage production, pastoral value and soil CO2 emissions under contrasting management regimes in Bromopsis erecta-dominated grasslands (2016–2018). A randomised complete block design tested three regimes: customary management (CST, two cuts per year), intensive utilisation (INT, four to six cuts per year) and abandonment (ABN, no cuts). Changes in species composition relative to CST were mainly associated with ABN, which increased the cover of Brachypodium rupestre, Dactylis glomerata and Cerastium arvense, while leading to a general decline in species associated with mowing. Diversity indices showed significant interactions with year and management: target species number differed only in the third year between INT and ABN, while richness and H′-index were lower in INT than in CST and ABN in the first year, reversing by the last year. Herbage production in ABN reached 6.8 t dry matter ha−1 in the third year (+180% vs. CST; +117% vs. INT), whereas pastoral value ranged broadly (13.4–57.1) with no significant differences among regimes. Cumulative soil CO2 emissions were highest in the first year (31.12 t CO2 ha−1 year−1) and declined to 17.5–19.3 t CO2 ha−1 year−1 in subsequent years, without significant management effects. Overall, short-term intensive utilisation does not negatively affect herbage production or soil CO2 emissions, although slight increases in annual mesophilic species may signal a shift towards nutrient-rich communities. Even short-term abandonment shows no major trade-offs, suggesting flexible management can support both biodiversity and farmer livelihoods while maintaining key ecosystem services.