Is Empodisma minus the ecosystem engineer of the FBT (fen-bog transition zone) in New Zealand?

Abstract

The role of ecosystem engineers (EE) in the formation of ombrotrophic mires (bogs) from fens, called the fen-bog transition (FBT), can be best understood through categorization of the autogenic and allogenic processes causing bog initiation. Here we review these pathways, discuss the drivers of change in both cases, and tabulate an approach for distinguishing between them. We then compare the engineering ability of acknowledged and putative engineers against a number of characters which plants require to cross the FBT, and to stabilize occupancy on the bog side. While some Sphagnum spp. are accepted as the EE of the fen-bog transition in northern hemisphere bogs, they appear unimportant in New Zealand. Instead their role appears to be occupied by a restiad, Empodisma minus, a plant with leafless, wiry stems and capillaroid roots. Empodisma minus appears capable of engineering autogenic transitions from fen to bog across New Zealand, even more efficiently than Sphagnum. © 2010 The Royal Society of New Zealand.