Abstract: Amaranthus retroflexus is native to America but a widely distributed exotic invasive weed in China. This paper summarized the researches on its seed biological characters, allelopathy, phenotypic plasticity, eco-physiological characters as a typical C₄ plant, competition with crops, invasive expansion process and limiting environmental factors in China, responses to increased UV-B radiation, and control methods. Some biological characteristics of A. retroflexus contribute to its strong invasion. A. retroflexus is a prolific seed producer, and its seeds can germinate over a wide range of temperature. A. retroflexus  has strong allelopathic effects on the growth of many crops, and exhibits high photosynthetic capacity no matter at high temperature and high light intensity or at low temperature and low light intensity. It can also show high phenotypic plasticity to the spatiotemporal changes of environmental conditions and adapt to a wide range of temperature and humidity, and thus, can invade many different types of habitats. Aiming at the deficiencies of the studies on A. retroflexus, following issues were proposed: 1) the adaptation mechanisms of A. retroflexus in response to large-range environmental gradient, 2) the responses of A. retroflexus to resources fluctuation in agroecosystem, 3) the allelopathic mechanisms of A. retroflexus, and 4) the effective integrated weed control techniques of A. retroflexus.

Key words: Changbai Mountain, Ecotone between forest and marsh, Regional climate change, Succession