Old field (ecology)

Old field is a term used in ecology to describe lands formerly cultivated or grazed but later abandoned. The dominant flora include grasses, heaths and herbaceous plants, with encroaching woody vegetation. It represents an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community. The concept of climax communities has been challenged in recent years.

Old field sites are often marginal lands with soil quality unsuitable for crops or pasture. Examples include abandoned farmlands in central Ontario, along the edge of the Canadian Shield.