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Displaying items by tag: Wetland Restoration

Tuesday, 02 April 2019 07:28

There’s a road through these wetlands

Gordon Pilone tells the story of how Pohangina Wetlands, now protected by a QEII National Trust covenant, were created

In 1995 Gordon and Anne Pilone bought a lifestyle block in Pohangina Valley, retiring there from Palmerston North where Gordon, originally from California, had lectured on and researched microbiology at Massey University and Taranaki-born Anne had established the best veggie and landscape gardens in town, which would prove valuable experience later.

Beside the Pilone property, sheep and bulls were grazing on a very wet paddock with some remnant kahikatea (New Zealand white pine) and other wetland flora struggling to survive. This farmland, owned by Finnis Farming Company (John and Mary Culling), had historically challenged owners’ efforts to drain it. 

Across the road was the well-established Luttrells White Pine Gardens and Museum. The 
gardens had walking tracks but only one small pond to attract wetland wildlife. And so began Gordon and Anne’s long-term retirement project to create a large, mature wetland. They set up the Gordon and Anne Pilone Charitable Trust in August 2000, and were joined by farmer and orthotist Chris Pullar and accountant Ian Mackrell as trustees. A fifth trustee, naturalist Dr Liz Grant, joined later, contributing her expertise in visual design and entomology science. All are Ducks Unlimited members.

Shaping the wetlandsThe development took off in 2001 when the trust employed contractor Kevin Large with his digger and bully to create the first pond near the main entry gate along Pohangina Rd. This is now known as the kahikatea block. Progress was slow as the wet dirt, being moved to create a pond, was used to develop the head and track along the bund, but it needed time to dry to get access. 

Then in 2004 floods struck Pohangina Valley. Roads and bridges were washed away and Pohangina Rd was cut off when the culvert bridge at Sandy Creek was washed out. Pohangina Wetlands became even more soggy, but no damage occurred because the “wet” of the wetlands comes from aquifers and not directly from water flowing on the surface from creeks, streams or rivers. 

Development slowed down after the flood because Kevin was involved with clean-up work in the valley but activity continued with the planting of native grasses, bushes and trees, mostly by Anne. 

Because of the slope, all the surface water that overflows in the wet months flows to the southernmost part, the base of the damsite block. Until 2012, this water drained directly to the Weka St drain and the river. But Gordon found a way that this flow could be reused to establish a different habitat within the wetlands. 

In 2006, work began on the second block (damsite block) and the biggest pond (0.54ha), which includes a sizeable island and a subterranean island – sometimes visible in the drier seasons.

Work on the “big pond” was challenging and a large track-dump truck and extra help 
were required to take away the soil. It was also a large block (2.3ha) to plant out so Anne was flat out growing and planting and weeding. It is now maturing nicely and has a 

Once the damsite block was completed, Gordon convinced the other trustees that additional property would be fruitful for the future protection of the two main blocks. 

The kahikatea block formed an L-shaped property with the newly developed damsite block, and the triangular block nestled in the “L” was being used for grazing. In 2010 this land was bought and designated the Culling block. 

Instead of extensive pond development and native plantings, the block, essentially, is being allowed to “develop on its own”. Some earth was moved by Tim Luttrell with his small digger to provide a flow of surface water and a few flax, cabbage trees and Carex 
geminata (cutty grass, rautahi) have been planted among the rushes. 

The wetlands slope dramatically towards the Pohangina River, and the aquifer and surface water flows from north to south. This enabled the creation of ponds of varying depths and in the drier months, muddy areas form at the upside of the ponds. This habitat is invaluable because it attracts wading birds that feed in the “mudflats”. So watch out for pied stilts, heron, royal spoonbill, spur-winged plover, and dotterel.

Finnis Farming Co allowed the trust to acquire a small (0.2ha) parcel at the back of the damsite block from which Tim created a series of shallow ponds, with final exit of water overflowing to the Weka St drain. 

Retention of water in this block is being aided by the planting of raupo (bulrush, cat-tail). This will create a new habitat and will allow shy and uncommon wetland birds to be seen such as fernbird, crakes and bittern. Even if this is wishful thinking – because the area is small – raupo swamps are ideal as filters for water purification. 

Challenges along the way

Even with the best planning, things can go wrong and sometimes reworking is necessary, and costly. In 2006 it became noticeable that the big pond in the damsite block would not maintain its full overflow level for long after a wet period, but dropped quickly, exposing the subterranean island and pond bottom. 

When walking along the track behind the head next to the drain, a wet patch was apparent so an exploratory ditch was dug along the pond below the base of the head. It exposed a cluster of rocks which seemed to form a drain into the head since water was trickling from them. It is likely this had been a very wet paddock, with drainage created from a ditch filled with rocks, and these were not noticed when the head of the big pond was developed. All agreed the remedy was to cut through the head and remove the rocks and rebuild it. 

During a trustee tour after the Eketahuna earthquake in January 2014, it was obvious the poplar pond in the kahikatea block was extremely low. This pond is where the “waterworks” pipe crossing the pond head with an upright was built to allow discharge of the pond water to different levels. We thought it would be clever to be able to control the water level and form new habitats (for example, exposed muddy areas) at will. Well, Mother Nature thought differently. 

The reason for the low water level became apparent when Anne found water leaking from the outlet side of the pond hidden in tall grass near the end of the pipe running through the head of the pond. On further inspection, there was a large crack in the plastic T-fitting at the base, which must have happened in the earthquake. 

The T-fitting was held snugly by two posts and apparently there was not enough “give” when the earthquake hit. The assembly was removed and the pipe carrying water through the head was capped off on the inlet side of the pond. We learnt that careful thought needs to be given to the design of piping in a wetlands system. 

Another example was during the development of the ponds in the kahikatea block. The main ponds there are connected by 110mm pipes allowing water to flow from one pond to the next underground rather than over the tracks, ensuring easier and drier access 
for visitors. 

Gordon had a bright idea to prevent clogging of the inlet of the pipes with surface debris: the inlets could be fitted with a short pipe at a 45-degree angle to submerge the inflow beneath the surface of the pond. Soon after this modification, he was surprised to find all the ponds had lower water levels than the expected overflow levels when the ponds were full. 

The penny dropped and it became obvious that the inlet-angled pipe also allowed for siphoning to occur when the flow was great enough to fill the pipe and continue to flow to the level of the submerged inlet. A lesson learnt.  And the solution was obvious, too – drill a hole at the attachment point of the angled pipe to allow the inflow of air, thus preventing siphoning. 

Some other “oops” happen unexpectedly and require major adjustments. In 2011 Gordon began to have cramps in the calves of both legs. Peripheral arterial clogging was advanced and in 2015 he had to have both legs amputated above the knees. Now wheelchair-bound, Gordon is no longer physically active in the wetlands development, but fortunately the main work is complete. 

Anne continues maintenance plantings

Tim Luttrell. 

The Pilone home could not be readily renovated for wheelchair living but, fortuitously, a cottage being built across the road by Tim and Carol Luttrell became available and was purposefully built for wheelchair use. You will still see Gordon in the wetlands, but not on his tractor mowing or on his bright orange Kubota RTV. 

Instead, he will be observing and taking pictures from a Timmobile, a mobility scooter renovated by Tim. So look out for Gordon on the tracks and have a chat, or come to the cottage across the road and say hi. 

Visitors always welcome

The wetlands were opened to visitors on the longest day in December 2005 and are always open to visitors at no charge. A brochure is available at the entry gate on Pohangina Rd. 

Probably one of the greatest joys in establishing a wetlands was seeing a kōtuku (white heron) visiting for a few hours in 2008. This has been a one-time event, though it may be that they visit when we are not in the wetlands. 

Another uncommon visitor is the New Zealand royal spoonbill (kōtuku ngutupapa). A young individual was seen for several days feeding in the shallow ponds. Some flock yearly at the Foxton beach estuary nearby. Since the first bird seen in March 2007, we have had increasing numbers visit and stay for several days, sometimes in flocks as big as 13. 

Another resident wetland bird that delights visitors is the dabchick (wewei). During breeding season, you can find one or two white striped headed chicks on the back of an adult with the mate diving and bringing food to the chicks. 

Luttrells wetlands and kahikatea bush 

Next door to Pohangina Wetlands and hidden by the magnificent tall stand of kahikatea is another developing wetlands area on the property of Tim and Carol Luttrell.

Luttrells White Pine Gardens and Museum is open any time by arrangement for a small fee. The complex is well-worth seeing and includes a walkway through kahikatea bush; tracks meandering around wetlands; and plenty of opportunity to view wetland wildlife and a comprehensive museum based on settlers in the valley. 

Pohangina Village residents are fortunate to have such an extensive wildlife habitat of 10ha (25 acres), combined, within walking distance of their homes. To assure it is kept in perpetuity for future residents, the Pilones and Luttrells have been granted Queen Elizabeth II National Trust covenants on the portion of their properties that constitute wetlands and bush. We are grateful and honoured that the QEII National Trust has regarded the properties as worthy of protection. 

Now that the future of the two wetlands are secure, it is interesting to speculate what form of management might develop for their continued maintenance. Pohangina Wetlands, now under the auspices of the Gordon and Anne Pilone Charitable Trust, already has some long-term management permanency in the “turnover” of trustees, as well as financial assurance as the beneficiary of the Pilone estate. The Luttrell wetlands and kahikatea bush belong to the family, but the long-term future is unclear. 

As the two properties are beside each other, separated only by a road, and wildlife interaction is seamless, it seems logical that the two properties be managed as one. In Manawatu, there already are open space properties being managed by some level of government using subcontracted maintenance. This might be considered for the future management of the “Pohangina Village Wetlands”. 

We look forward to seeing you in the “wetlands a road runs through”.

Visit for more information. 



Published in Issue 176
Wednesday, 16 January 2019 09:08

Nurse trees give saplands a headstart

Stevie Waring has been looking into the benefits of nurse trees in wetlands restoration at Wairio.

Wetlands are ecologically important, biologically rich habitats that support a vast range of habitats for plants, animals and soil microbes.

Swamps are a category of wetland that are dominated by flood-tolerant trees, which thrive in soils that are nutrient-rich, but occasionally boggy or flooded.

Historically, New Zealand’s swamps were dominated by large podocarp trees,especially kahikatea andtotara, but these were targeted as valuable timber throughout the 19th century. Thereafter, land conversions for urban expansion and agriculture
continued to degrade swamps. A primary goal of wetland restoration is to revegetate sites with native trees.

However, up to 70 per cent of sapling trees can die within the first year of planting. The death of trees increases the financial costs of wetland restoration while reducing the benefits to nature and the morale of project participants. Put simply, dead trees reduce the feasibility of restoration of wetland swamps.
The survival and growth of sapling trees planted in wetland restoration projects depends on the interplay of many site factors including water levels, soil biology and fertility, wind exposure, herbivores and locations of nearby trees and plants.

Nearby plants can affect the earlier years of a sapling’s life. For example, highly competitive perennial grasses can shade and outcompete the saplings for light and soil resources. On the other
hand, having neighbours may benefit the sapling.
Nurse effects are positive interactions between plant species whereby an older ‘nurse’ tree facilitates the establishment of a sapling. Nurse trees can help saplings in a variety of ways, for example by sheltering a sapling from wind, frost, extreme heat, or intense sun. The deep root systems of nurse trees can draw up nutrient rich water from deeper soil, enhancing water availability to the shallow root systems of the saplings.
Nurse trees can also provide a source of beneficial fungal spores. Arbuscular mycorrhizal fungi (AMF) form mutually beneficial relationships with trees.

In exchange for sugars made by the plant in photosynthesis, AMF provide the plant with soil nutrients. Because sapling establishment is influenced by nurse trees over such a wide range of site conditions, nurse effects may be particularly important for trees.

Little is known about how nurse trees affect establishing saplings in wetland restoration. Can strategically planting saplings near nurse trees increase their survival and growth rates? Or are other
site factors such as soil moisture more important for sapling survival?

In my MSc thesis, in the Centre for Biodiversity and Restoration
Ecology at Victoria University, I sought to identify how nurse
trees improve establishment of two podocarp tree species
planted as part of a wetland swamp forest restoration.

In collaboration with Ducks Unlimited and the Department of Conservation, I monitored the survival and growth of kahikatea
(Dacrycarpus dacrydioides) and totara (Podocarpus totara) saplings planted with or without an established nurse trees at the Wairio wetland. The wetland connects a large, ecologically, culturally and recreationally important wetland complex that spans the Wairarapa valley. However, the increased nutrient inputs from livestock and chemical fertilisers and the introduction of pasture plant species have led to a weed-dominated environment.

During restoration, highly competitive perennial grasses can shade and outcompete the newly planted, slowgrowing podocarps. In addition, the complex hydrology of the site leads to species-specific spatial patterns of mortality and growth.

In my studies, I tested whether the presence of a woody nurse tree
(manuka, pittosporum or coprosma) influenced the survival and growth of kahikatea and totara over the critical first year of establishment. I monitored soil moisture, the pH and oxygen status of soils, root-available nutrients, and soil carbon content under saplings planted with and without nurses. I also quantified the abundance of spores of AMF fungi under all saplings.

Overall, I found that kahikatea saplings survived better than totara saplings, especially in very wet areas, but they were slower growing. Kahikatea did not benefit from nurse effects, rather it was frequently the only tree species capable of tolerating the wettest environments. In contrast, totara survived better than kahikatea in the drier areas of the wetland and grew on average 24cm taller in the presence of a nurse tree. The positive effect of a nurse tree on totara growth occurred regardless of the nurse species. Nurse trees increased the availability of mineral nutrients to totara. This suggests that the enhanced pull of deeper soil water by the large root systems of nurse trees increases the availability of mineral nutrients to totara saplings.
Finally, I found that the abundance of AMF spores varied with soil moisture, with the wettest areas having fewer spores. Moreover, the growth of both kahikatea and totara were positively related to numbers of AMF spores. These results suggest plants and  beneficial mycorrhizal fungi respond  similarly to patterns of wetland hydrology, and the availability of AMF inoculum is unlikely to limit the establishment of kahikatea and totara.  From this we have learnt that respecting the hydrology is key to revegetation 
for slow-growing podocarps; kahikatea will tolerate wetter soils, while totara should be planted in drier areas. If you want to establish totara in a restoration project, we recommend planting fastgrowing nurse trees three to five years in advance. 
At Wairio, nurse plants were four years old when the podocarps were planted, and totara tended to grow best where the nurse trees were largest. Planting around existing native trees and the development of expanding ‘tree islands’ over time should enhance podocarp survival during ecological restoration. • Stevie Waring and her supervisor, Dr Julie Deslippe, work at the Centre for Biodiversity and Restoration Ecology  at Victoria University, Wellington. They  wish to acknowledge the generous support of the Inshallah Trust.
Are you interested in helping with more research like this? 
We are looking to collaborate with Wairarapa farmers with restored or unmanaged wetlands to better understand the benefits  that wetlands provide. Please visit  our website, Wetlands for People and Place, to learn more. Contact Julie Deslippe at Julie.Deslippe@ or Stephanie Tomscha at This email address is being protected from spambots. You need JavaScript enabled to view it. to get involved.


Published in Issue 175

Essential information for the decision making process of wetland restoration.

Abstract: Cheng Shi.

Wetlands are areas where lands transition  to water bodies. Because of this special geomorphological setting, wetlands play important roles in flood control, nutrient retention, and water storage. In New Zealand, less than 10 percent of the original wetlands have survived since human settlement. Many of the remaining wetlands are still under threat from water quality degradation, invasive species, and changes in hydrological regime. 

Wetland restoration is the process of bringing the structure and function of a wetland back to its original state. Although specific objectives may vary between projects, three major objectives of wetland restoration are restoration of wetland function, restoration of wetland structure, and restoration of traditional landscape and land-use practices.  In order to ensure the success of a wetland restoration project, a good understanding of the hydrological process in the wetland is the first step. 

Boggy Pond and Matthews Lagoon on the eastern edge of Lake Wairarapa in the Wellington Region were formed as a result of the deposition of sand dunes on the eastern shore and changes in river courses between floods. They were modified by a series of engineering works under the lower Wairarapa valley development scheme in the 1980s. 
As a result, Matthews Lagoon now receives agricultural outputs from surrounding farms; it is affected by water pollution and invasive plant species. 

Boggy Pond is cut off from Lake Wairarapa and surrounding wetlands by a road and stopbank, leaving a more stable water level compared to its original state. To analyse the water and nutrient balance in these two wetlands, factors such as surface flows, surface water levels, groundwater levels, rainfall, climate data, and water quality were assessed at various monitoring stations in this study. It is believed that Matthews Lagoon and Boggy Pond have completely different water regimes. Matthews Lagoon receives surface inflow from the Te Hopai drainage scheme and discharges to Oporua floodway, but Boggy Pond only has rainfall as the water input. 

The results from the water balance analysis seem to support this assumption. An unexpected finding in Matthews Lagoon suggests that water might bypass the main wetland, creating a shortcut between the inlet and outlet. As a result, the nutrient removal ability was considerably weakened by this bypass because of the short water retention time. 

In Boggy Pond, there may be an unknown water input which could adversely affect the 
water quality and natural water regime. Boggy Pond is expected to have better water quality than Matthews Lagoon as the latter receives agricultural drainage from surrounding farms. The results from water quality monitoring also support this hypothesis. The nutrient balance in Matthews Lagoon showed very limited removal ability for phosphate but much higher removal rate for nitrate. The removal rate in summer for phosphate was less than 5 percent while in winter more phosphate was discharged from Matthews Lagoon than it received from Te Hopai drainage scheme. For nitrate pollutants, the removal rate was as high as 17 percent even in winter. 

Some recommendations are given on the restoration of these two wetlands. First, set proper objectives according to their different functions. Second, enhance the nutrient removal ability of Matthews Lagoon by harvesting plants, removing old sediments, and creating a more evenly distributed flow across the wetland throughout the year. Third, restore the natural water level fluctuations and improve water quality in Boggy Pond by identifying any unknown water inputs first.

To view Cheng Shi’s full thesis go to:


Published in Issue 162
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