Abstract:Ecotone is a unique landscape that displays special ecology attributes and service functions. Investigation of ecotone is significantly beneficial to both exploring novel ecological laws and conserving the vulnerable environment. An increasing attention to ecotone is evidenced by the average annual publication growth rate of 57% in the last 30 years. This paper presents the concepts of and the differences among ecotones, and its related terms (ecological boundary, transitional area, environmental gradient and edge). Specifically, ecotone is a region between two ecological systems with unique ecological properties, and ecological boundary is a generic term including all kinds of interfaces, while transitional area is a description of the scope between adjacent geographic zones. Edges and environmental gradient are terms not confined to ecological discipline. Furthermore, seven basic features of ecotone are summarized in brief as: high-biodiversity, rich ecotonal species, abundant exotic species, frequent material flows, sensitive temporal-spatial dynamics, structure heterogeneity and frangibility. Then, we introduced the published principals and hypotheses about ecotone as well as originally presented Gene Hybrid Zone Hypothesis, Habitat Pressure Hypothesis, and System Successsional Hypothesis to elucidate the mechanisms of ecotone. At last, research advances are discussed in four aspects: (1) The patterns of biodiversity development in ecotones. More and more researches have been exhibiting that ecotone creates genetic diversity although its species richness is still controversial. (2) Responses and feedback to global changes. Ecotone is very sensitive to global changes (warmer climate, disturbances, and biological invasion, etc.). The changes of landscape in ecotones are presumably due to the alteration of varied material flows. (3) Ecological design and management of ecotones. Many researches are performed on the functions of conduit, filter and barrier of ecotones, particularly in land/water interface. The uptake of nutrients by ecotones functions cleaning river water. (4) The models of ecotones and its integration. The dynamic of plants movement and the relationship of plants and soil in ecotones are simulated by kinds of ecotone models. However, integrated models are still deficient. We conclude that the highlights of future research should be ecotone theories, multi-scale models and multi-variable integrated analysis of ecotone patterns to discover ecological mechanisms of ecotone.