Freshwater repo – marshes, fens, swamps and bogs – have unique characteristics. Plant ecologist and repo expert Bev Clarkson tells us how hydrology, nutrients and gumboots provide clues to wetland types.
Questions for discussion:
- What role do nutrients play in determining the types of vegetation that grow in repo?
- Why do you think Bev uses gumboots (rubber boots) to help people understand the differences between wetland types?
Transcript
Dr Beverly Clarkson
There are different wetland types around New Zealand, and the different wetland types have different environmental conditions, different hydrology, different nutrients.
Succession is the change of plants according to the environmental conditions. When there’s a disturbance, there’s usually quite a bit of nutrients around, so the plants that come in usually are adapted to high nutrients. But in time, once the nutrients wind down, other plants are more successful at surviving in that area. So the lower nutrient-demanding plants will replace the higher nutrient-demanding plants. So therefore, there will be a change in vegetation type.
And normally succession is marshes that are quite high in nutrients, and they’re quite dry, through to swamps, which have more water and they’re slightly high in nutrients, through to fens through to bogs. And bogs are the oldest wetland type – they’ve developed peat, they’re very low in nutrients, they’re rain fed. So they only get their water and their nutrients from rain, they don’t get any input from groundwater or run-off.
The differences between the main wetland types – the marsh, fen, swamp and bog – can be determined by the gumboot test. Marshes, which are dry in summer, we can walk across those in sneakers. Swamps are quite wet, so we’ll probably need quite high waders – waist waders or thigh waders. Bogs are the other extreme. The water is held up within the peat, so the water table is just at or below the surface, so we can walk across those in Red Band and shallow gumboots. Fen are somewhere in between, where you’ll get wet patches and dry patches. So you can use, for example, South Island gumboots, which are up to the knees.
Acknowledgements
Photo of raupō plants, wire rush Empodisma robustum and Empodisma minus and giant cane rush, Dr Beverley Clarkson, Manaaki Whenua – Landcare Research
Close-up photo of flowering raupō, M Denyer
Sphagnum moss photo, Sarah Richardson, CC BY-NC 4.0
Sourced from iNaturalistNZ
Whangamarino marsh, Kerry Bodmin, NIWA; Lake Brunner marsh photo, Brain Sorrell, NIWA; Whatipu swamp photo, Dr Monica Peters, NZ Landcare Trust; bands of willow colonising former shorelines at Waimarino wetland, Lake Taupō, Tongariro Natural History Society; and Waipapa mire (fen) at Pureora Forest Park, Waikato and Awarua Bog, Dr Beverley Clarkson, Manaaki Whenua – Landcare Research. Chapter 3, Wetlands Restoration: A handbook for New Zealand freshwater systems
