The Wairio Wetlands were on the list for the 200 members of the New Zealand Farm  Forestry Association being hosted by the  Wairarapa branch for their 55th annual conference.

Our own DU member and director, John Dermer is  currently their national president. Wairarapa Farm Forestry president Stu Orme, and secretary Shane Atkinson, were thoughtful enough to  write to Jim Law and thank him for hosting their field trip to Wairio:

“We would like to thank you for the effort you put in to host our field trip to the Wairio wetlands. Your restoration project directly addresses all three themes of our conference and is an  outstanding example of a local initiative on a grand scale. Lake Wairarapa dominates the  whole of the lower valley and the re-creation of wetlands along the degraded eastern  boundary is a task with very long-term benefits. All our visitors enjoyed their trip. Thank you again.” 

John Dermer said that all 200 of the NZFF conference attendees visited Wairio. 

“We visited Castle Point Station in the north and down to the southern end to Prinoa Station and Waiorongomai on our last day with a look at Wairio and a talk from Jim Law.”

John said that once again he was struck by the sheer size of the Wairio Wetland although it was living up to its name, 'dry water' at the time. “Jim told us about the weed issues, mainly tall fescue, which makes getting trees established more difficult and the answers we are trying to find. One thing I noticed was how well plants are managing on the piles of soil excavated,  so my main question is Why not do more? “There must be a shallow water table underneath so why aren’t we digging deeper? “What is the point of digging holes so shallow they don’t hold water?” John said there is no way he would site his maimai on this bit of dry wetland. He said  he is sure the Farm Foresters were impressed, and they certainly asked lots of questions.

John Dermer

The Wario Wetland has come in for some close scrutiny by Victoria University Student Bridget Johnson who is this year studying towards an MSc in Ecological Restoration. The overall title of her thesis is  “Ecological restoration of the Wairio Wetlands, Lake Wairarapa: vegetation dynamics and succession”. 

A Summer Scholarship meant she was able to do 10 weeks of research in her chosen field at Wario  with the title for that part of her research being “Temporal & Spatial Patterns of Wetland Vegetation during the Summer Desiccation Period at Wairio Wetlands, Wairarapa”. In addition to the summer  scholarship, Bridget has started preparing a second site at Wairio for a large scale experimental  project where around 2400 trees have been planted.

The summer study programme provided an introduction to the Wairio Wetland for Bridget where she  continues the research for her thesis on factors contributing to wetland restoration. Flight, with help from Jim Law, has been able to follow Bridget’s research so far.

A poster she produced she said was just a snap shot of some of that research. “Due to the limiting  size of the poster, I only talked about rare species vulnerability.” All the summer scholars got to  show their posters at a poster evening. Her poster included the following information plus a number  of illustrations.

Introduction

Small in size, New Zealand’s native wetlands plant species are repeatedly outcompeted by more  aggressive weeds. The surrounding vegetation invades when wetland plants are most vulnerable,  during the desiccation (dry) period. A number of threatened low-lying plants (Pratia and Glosso) inhabit the Wairio Wetlands. To conserve these native plants a greater understanding is required of their optimal conditions and their spatial and temporal dynamics. “My aim was to investigate the temporal scale of the native species, and which abiotic factors affect their spatial distribution.”

Methods

Vegetation composition was sampled in 20 quadrants over a 10 week summer period. The quadrants were set five metres apart along two 50 metre perpendicular transects. The first transect followed a moisture gradient, whilst the other ran parallel. Additional abiotic variables were measured, such  as soil moisture, soil pH, percentage open ground, sunshine hours and rainfall. Water Plantain was  chosen as a comparative species as it is a common invader and an indicator of high soil moisture.

Discussion

The rare species are restricted to a small band of high moisture sites. A smaller number of invasive species can grow in these moist soils, so there are fewer competitors for the natives. In drier soils, the invasive species can spread easily, giving the vulnerable natives little chance of survival. This means the natives have truly specialised ecological requirements, as their time frame of existence  and habitat preference is small. This is a contributing factor to what makes them vulnerable. Further research can be expanded from this study, for example: Should water plantain (and other invasive high moisture soil species) be managed to decrease the competition on the native species?  Illustrations on the poster included Glasso, Pratia and Water plantain. Glosso and Pratia grow in soil with high moisture content and Water plantain grows more abundantly in high moisture soil but is adaptable to a greater variance of soil moisture. Bridget said the native species emerge later in the summer season, whereas water plantain is a  consistent species. When the natives start emerging they have a higher percentage cover than the invasive water plantain.

“I would like to thank Dr Stephen Hartley, Tony Silbery (Department of Conservation Wairarapa), Jim Law (Ducks Unlimited) and Don Bell (Greater Wellington Regional Council) for their technical  support,” said Bridget.

References: New Zealand Plant Conservation. 2010.