Grasslands and open savannas are transitioning to shrub-dominated or tree-dominated landscapes. This phenomenon, often referred to as woody plant encroachment, is occurring globally. The outcomes of interactions among the various drivers of this change differ biogeographically; in semi-arid and subhumid regions they are often related to grazing-induced changes in fire regimes. Two important theoretical and conceptual frameworks are emerging that help us understand the underlying mechanisms of these transformations and inform approaches for maintaining and restoring grasslands and open savannas: alternative stable state theory (ASST) and pyric herbivory. Alternative stable state theory is a way of explaining, understanding, and predicting ecosystem state transitions in dual-life-form systems, and pyric herbivory is built on the notion that reciprocal, spatially distributed interactions between grazing and fire are a key to maintaining grassland and open savanna landscapes. Considered in tandem, ASST provides insights into rates and dynamics of grass–woody vegetation transitions, with pyric herbivory providing a conceptual basis for designing sustainable, site-specific management strategies. Future progress will hinge on experimental evaluations of these linked frameworks and their subsequent refinement over longer time frames in an adaptive management context.

草原和开阔的热带稀树草原正在过渡到以灌木为主或以树木为主的景观。这种现象通常被称为木本植物侵害，正在全球范围内发生。这种变化的各种驱动因素之间相互作用的结果在生物地理学上是不同的。在半干旱和半湿润地区，它们通常与放牧引起的火势变化有关。正在形成两个重要的理论和概念框架，它们可以帮助我们了解这些转变的潜在机制，并为维护和恢复草原和开阔的稀树草原提供途径：替代稳定状态理论（ASST）和and草性食草动物。替代的稳态理论是解释，理解和预测双生命形式系统中生态系统状态转变的一种方式，而草食性草食动物是基于这样的观念，即放牧和火之间的相互，空间分布的相互作用是维持草地和火力的关键。打开稀树草原景观。结合考虑，ASST提供了草木植被过渡的速率和动态的见解，而草食性草食为设计可持续的，针对特定地点的管理策略提供了概念基础。未来的进展将取决于对这些链接框架的实验评估以及它们在适应性管理环境中在更长的时间范围内的后续改进。