Data from: Past tree influence and prescribed fire mediate biotic interactions and community reassembly in a grassland-restoration experiment

1.Woody plant encroachment of grasslands is occurring globally, with profound ecological consequences. Attempts to restore herbaceous dominance may fail if the woody state is resilient or if intervention leads to an alternate, undesirable state. Restoration outcomes often hinge on biotic interactions – particularly on priority effects that inhibit or promote community reassembly. 2.Following experimental tree removal from conifer-invaded grasslands, we documented substantial variation in community reassembly associated with the changing abundance of the native clonal sedge Carex inops L.H. Bailey subsp. inops. We explored possible mechanisms for this variation, focusing on the nature and timing of interactions between the meadow community and Carex and on how past tree influence and prescribed fire mediate the outcomes of these interactions. 3.Meadow species increased after tree removal, but less so in burned than in unburned plots. Carex expanded dramatically after fire, particularly where past tree influence had been greater. 4.Meadow species and Carex developed an increasingly negative association over time; preemption was reciprocal, but offset in time and space. Meadow species inhibited Carex through vegetative recovery in areas of limited or recent tree influence, irrespective of fire. Carex inhibited meadow reassembly in areas of greater tree influence, but only with burning. 5.Synthesis and applications. Tree removal and fire imposed across a range of altered meadow states yielded varying outcomes, reflecting biotic interactions and species’ regenerative traits that inhibited or promoted reassembly. Fire tended to destabilize the remnant meadow community and, in areas more degraded by encroachment, stimulated release of Carex, which inhibited reassembly. Knowledge of the context-dependence of biotic interactions can enhance the effectiveness of restoration by establishing the bounds within which treatments produce desirable or undesirable outcomes.

1. 全球范围内正发生草原木本植物入侵（woody plant encroachment），其带来了深刻的生态后果。若木本群落仍具恢复力，或干预措施引发了另一种不理想的群落状态，恢复草本优势度的尝试往往会失败。群落重建（community reassembly）的成败通常取决于生物相互作用——尤其是那些抑制或促进群落重建的优先效应（priority effects）。
2. 本研究针对针叶树入侵的草原开展了伐除试验，随后记录到群落重建过程中存在显著差异，这与本地克隆性薹草（Carex inops L.H. Bailey subsp. inops）的丰度变化密切相关。我们探究了造成这种差异的潜在机制，重点关注草甸群落与该薹草之间相互作用的本质与时机，以及过往树木的影响和控制性火烧（prescribed fire）如何调控这些相互作用的结果。
3. 伐除树木后，草甸物种的丰度有所提升，但火烧样地的提升幅度低于未火烧样地。该薹草在火烧后出现了爆发式扩张，尤其在过往受树木影响更为严重的区域。
4. 随着时间推移，草甸物种与该薹草之间的负相关关系逐渐增强；二者存在相互的生态位优先占据（preemption）现象，但在时间与空间上存在偏移。在树木影响有限或新近受树木影响的区域，草甸物种通过营养体恢复抑制该薹草的生长，这一效应不受火烧的影响。而在受树木影响更为严重的区域，该薹草会抑制草甸群落的重建，但仅在火烧处理下才会出现这一现象。
5. 总结与应用。在一系列受干扰的草甸状态下开展伐树与火烧干预，得到了多样化的干预结果，这反映了抑制或促进群落重建的生物相互作用与物种再生性状（regenerative traits）的作用。火烧往往会破坏残存草甸群落的稳定性；而在受木本入侵破坏更为严重的区域，火烧会刺激该薹草的增殖，进而抑制群落重建。明晰生物相互作用的情境依赖性（context-dependence），可通过明确干预措施催生理想或非理想结果的边界条件，提升生态恢复工作的成效。