Fencing-driven soil seed bank alterations: reduced precipitation sensitivity and hints of management-induced retrogressive succession in alpine grasslands

Background and aims

The degradation of the alpine grasslands on the Qinghai-Tibet Plateau has been mitigated in some regions, while it persists to varying degrees in others. Soil seed banks (SSBs), reflecting the past, present, and future potential of plant communities, are critical for restoration. This study assessed fencing, a nature-based solution, addressing regional biases and limited cross-regional synthesis in prior research.

Methods

Paired plots of free grazing and fenced grazing were established through field sampling. Community and SSB characteristics were compared between fenced and grazed areas using vegetation and seed bank surveys, seed germination experiments, and statistical analyses. Structural equation modeling (SEM) was employed to identify regulatory pathways influencing seed density under both management regimes.

Results

Fencing increased seed density (346–20,961 seeds/m²) compared to grazed areas (346–14,378 seeds/m², p < 0.05). The Sørensen similarity index indicated altered community structure and retrogressive succession (fenced: 0.803; grazed: 0.766). Fencing raised the importance value (IV) of Poaceae by 8.70% but reduced non-grass species richness and IV by 8.13%. SEM explained 95.04% (fenced) and 97.30% (grazed) of seed density variation, with fencing weakening seed density response to precipitation.

Conclusions

Fencing significantly affects SSBs by altering seed density, community structure, composition, and diversity. These changes reduce the sensitivity of SSBs to precipitation and may contribute to retrogressive succession in alpine grasslands. This study provides theoretical support for utilizing SSBs as a target for nature based solution to restore degraded alpine grasslands on the Qinghai-Tibet Plateau.