In the context of human activities and climate change, understanding the regime shifts in vegetation ecosystems, particularly during degradation and restoration processes, is of paramount importance. Despite a series of studies indicating that human activities and climate change have led to significant changes in the interactions and feedback mechanisms within vegetation ecosystems, uncertainties still remain regarding the critical response and ecological threshold. Here, a systematic review is conducted based on the findings of prior studies. Firstly, we synthesize the theoretical understanding of ecosystem regime shifts, defined as transformations from linear and equilibrium states to nonlinear and dynamic non-equilibrium states. Simultaneously, the biophysical structure and function of vegetation are used to elucidate the underlying mechanisms of regime shifts within ecosystems. Secondly, we analyze the threshold effects within vegetation ecosystems and sort out potential driver-response curves that might lead to the occurrence of ecological threshold. Finally, the signaling features of vegetation under regime shifts are organized to include the critical slowing phenomenon, spatial relationship anomalies, and regular patches. In light of the existing research gaps and the identified future research focuses, this study promotes that the management of vegetation based on thresholds ought to be grounded on the understanding of the critical response mechanisms and nonlinear self-organizing processes occurring within ecosystems.