ecocline

An ecocline is a gradient of ecological conditions and community composition along an environmental gradient, in which species replacement occurs gradually rather than at a discrete boundary. Ecoclines arise when abiotic factors such as temperature, moisture, soil pH, nutrient availability, or salinity change steadily over distance, allowing successive communities or life-forms to be favored at adjacent points. They are observed in terrestrial, freshwater, and marine systems and can vary in width from meters to thousands of kilometers.

Common examples include altitudinal gradients in mountains, where forest types shift gradually from lowland forest to montane forest to subalpine zones; moisture gradients across deserts and grasslands; and depth-related or salinity gradients in aquatic systems such as lakes, estuaries, and coastal zones.

An ecocline implies that environmental conditions change continuously and that species respond in a graded fashion rather than with a sharp boundary. It differs from an ecotone, which denotes a transition zone between communities that may exhibit an abrupt change or a high rate of turnover over a short distance.

Researchers study ecoclines by sampling along transects, analyzing species turnover and community composition with ordination and regression techniques, and linking observed patterns to underlying environmental variables. Understanding ecoclines helps explain patterns of biodiversity, species distributions, and biogeographic boundaries.