AbstractsBiology & Animal Science

Wetlands are highly productive ecosystems that support abundant native fauna and flora and provide many essential functions and services, for example water purification, erosion stabilisation, floodwater storage, groundwater recharge, peat accumulation and biogeochemical cycling. Despite the vast benefits they provide, worldwide loss and degradation of wetlands still continues, mainly due to agriculture, urban development, population growth and exploitation. Wetland disturbance can cause altered hydrological regimes, invasive species introduction, soil and water eutrophication, habitat fragmentation, and reductions in native fauna and flora leading to an overall reduced functionality. Ecological restoration is an active practice commonly undertaken in degraded wetlands to re-establish ecosystem functioning, and most commonly includes revegetation, reconstruction of hydrology, weed control, pest management, and native species reintroductions. Wairio Wetland located on the eastern shores of Lake Wairarapa forms a part of Wairarapa-Moana, the largest wetland complex in the lower North Island of New Zealand. Wairio Wetland was historically an abundant kahikatea swamp forest, with a diverse range of waterfowl, waders and freshwater fish. However, the wetland was adversely affected by draining from the Lower Wairarapa Valley Development Scheme (LWVDS) during the 1960’s and 1970’s, the construction of Parera Road, and invasion of willow tree seeds planted in the Wairarapa Valley for erosion control. Draining of the wetland, division from nearby lagoons and ponds, nitrogen and phosphorus build-up in waterways and exotic weed invasion all contributed to the poor state of the wetland. In 2005, Ducks Unlimited (DU) in conjunction with the Department of Conservation (DOC) and various members of the local community formed the Wairio Wetland Restoration Committee, with aims to manage and restore the wetland to its natural pre-settlement state. Restoration activities undertaken at the site that have included native tree planting, earthworks, weed control, pest management and fencing sections of the site to exclude cattle, have been met with mixed success over the years. This thesis reports on two studies undertaken at Wairio Wetland with aims to inform future restoration efforts at the site. The committee have proposed to divert nutrient rich water through Wairio Wetland to increase filtration and improve the water quality of Lake Wairarapa. However, the effects of nutrient loading on established plant communities at the site are unknown. Therefore the first study, conducted between December 2012 and May 2013 in Stage 2 of the wetland, examined the effects of fertiliser addition on biomass, structure and diversity of a wetland plant community. Different levels of phosphate and nitrate fertiliser were applied to 50 plots (4m2) of vegetation at the site with percent cover, and average height of respective species recorded every four to five weeks. Results showed that the addition of phosphorous and/or nitrogen had neither a positive…