Season of prescribed fire determines grassland restoration outcomes after fire exclusion and overgrazing

Fire exclusion and mismanaged grazing are globally important drivers of environmental change in mesic C4 grasslands and savannas. Although interest is growing in prescribed fire for grassland restoration, we have little long-term experimental evidence of the influence of burn season on the recovery of herbaceous plant communities, encroachment by trees and shrubs, and invasion by exotic grasses. We conducted a prescribed fire experiment (seven burns between 2001 and 2019) in historically fire-excluded and overgrazed grasslands of central Texas. Sites were assigned to one of four experimental treatments: summer burns (warm season, lightning season), fall burns (early cool season), winter burns (late cool season), or unburned (fire exclusion). To assess restoration outcomes of the experiment, in 2019, we identified old-growth grasslands to serve as reference sites. Herbaceous-layer plant communities in all experimental sites were compositionally and functionally distinct from old-growth g...

火抑制与管理失当的放牧是全球湿润型C4草原（mesic C4 grasslands）与稀树草原（savannas）环境变化的重要驱动因素。尽管学界对用于草原修复的计划火烧（prescribed fire）关注度与日俱增，但关于火烧季节对草本植物群落恢复、乔灌木侵占以及外来禾草入侵的长期实验证据仍十分匮乏。我们在德克萨斯州中部长期受火抑制且过度放牧的草原中开展了一项计划火烧实验（2001年至2019年间共实施7次火烧）。实验样地被分为4种处理组：夏季火烧（暖季，雷电季）、秋季火烧（早凉季）、冬季火烧（晚凉季）以及未火烧组（火抑制）。为评估本实验的修复效果，我们于2019年选取了成熟原始草原作为参照样地。所有实验样地的草本层植物群落在组成与功能上均与原始成熟草原存在显著差异……