Classification of vegetative lagg types and hydrogeomorphic lagg forms in bogs of coastal British Columbia, Canada

Abstract

A “lagg” is usually defined as the confined transition zone along the outside margin of a raised bog, characterized by a fen or swamp plant community. It is an important landscape element for biodiversity and helps to maintain a high water table within the peat mass of a bog, but has received little research attention. Greater knowledge of the variability in laggs will improve designation of appropriate conservation sites and restoration of damaged bogs. We therefore examined the hydrological, hydro-chemical, vegetative, and peat characteristics of laggs of bogs in coastal British Columbia, Canada. The 17 studied lagg transects were classified into four vegetative lagg types: Spiraea Thicket, Carex Fen, Peaty Forest, and Direct Transition. These vegetative lagg types fell within two hydrogeomorphic lagg forms: confined or unconfined. The Spiraea Thicket and Carex Fen laggs were topographically confined at the bog margin and characterized by a higher water table and a smaller tree basal area compared to the unconfined Peaty Forest and Direct Transition laggs. Half of the studied laggs were unconfined, highlighting the importance of considering both confined and unconfined laggs in the delineation, conservation, and restoration of raised bog ecosystems.