Quantifying soil, microbial, and plant community changes following wetland restoration on private land

<p>Extensive global and national wetland loss has reduced ecosystem services to people and undermines the sustainability of ecosystems. Restoration projects aim to regain the biophysical conditions of remnant wetlands that produce an abundance of ecosystem services. Ecological restoration practices manipulate community succession to enhance ecological functions, and these different successional stages may be reflected in the soil physio-chemical characteristics, plants, and soil microbes, which in turn produce a variety of ecosystem services. Considerable potential for wetland restoration on private property exists in New Zealand, but it remains unknown how successful restoration is when undertaken through a landholder’s own prerogative. Relative to restoration of public land, private restoration projects are often small scale, personally funded and preference driven. In this thesis, I quantify the outcomes of small-scale private wetland restoration projects by measuring changes in plant and soil microbial communities, and soil physiochemical characteristics. I explore the relationships among variation in plant, soil and microbial datasets and test for causes of this variation. Using a paired sampling design, I sampled 18 restored wetlands and 18 unrestored wetlands on private property in the Wairarapa region. I used a Whitaker plot design to sample wetland plant communities at multiple scales and took soil samples that I analysed for physio-chemical properties. Additionally, I quantified the biomass and community composition of the microbes in the soil samples using phospholipid fatty acid analysis. In my second chapter, I use linear mixed-effect models, principal components analysis, and non-metric multidimensional scaling to ask: How does wetland restoration alter the plant community, soil physio-chemical characteristics, and the soil microbial community? In my third chapter, I employ Procrustes analysis to look at the association of variation in plants, microbes, and soil characteristics to explore whether successional processes of these attributes are concurrent within wetlands. I then use hierarchical cluster analysis to determine which of the wetlands are at similar successional stages and identified site contexts and restoration treatments that were in common among similar wetlands. These analyses provide insight to the conditions that advance successional processes in restored wetlands. Specifically, I ask 1) How do plant, microbial, and soil characteristics co-vary during wetland restoration? 2) How do indicators of wetland succession respond to restoration? 3) Are different restoration practices and site contexts influencing wetland outcomes during restoration? Private wetland restoration enhanced succession in plant, soil, and microbial properties towards those more similar to undisturbed wetland conditions. Specifically, restoration added ~13 native plant species, increased totalfungal and arbuscular mycorrhizal biomass, and total microbial biomass by 25%. Restoration increased soil moisture by 93%, soil organic carbon by 20%, and saturated hydraulic conductivity by 27%. It also reduced bulk density by 0.19 g-1 cm3 and plant available phosphorus (Olsen P) by 23%. Procrustes analysis revealed a lack of congruence in the recovery of plant, microbial, and soil indicators of succession, signifying that the plant community succeeded faster than the microbial community and soil characteristics. Variation in soil and microbial properties separated restored wetlands into two groups of early and later succession wetlands, which was independent of the number of years since restoration began at the sites but corresponded to elements of wetland hydrology. Soil and microbial characteristics in hydrologically connected wetlands recovered more quickly following restoration than hydrologically isolated wetlands. Private restoration increased spatial heterogeneity of outcomes at the plot scale, which depended on site factors. My data suggests that private wetland restoration is effective in increasing plant, soil, and microbial characteristics that produce ecosystem services. Additionally, wetland restoration increased environmental heterogeneity and the capacity for ecosystem service delivery, which may contribute to increased resilience of the Wairarapa landscape.</p>

Project to Establish Growth & Mortality Rates of Three Carex Species in Two Planting Types at Thomas Dairy Site, Tigard, Oregon

Clean Water Services (CWS) currently increases the diversity of their wetland restoration projects using a plug planting method utilizing juvenile herbaceous plants. They have planted most of their projects using this method and plan to continue until a better one is discovered. According to the literature reviewed in this paper, juvenile plants are smaller and weaker than more mature plants and therefore have higher mortality rates. This paper is the culmination of work completed of phase 1 of this two-phase project. The objective of this project (both phases) was to design and establish a study that would test, in the field, two common wetland planting methods: installation of plugs of juvenile plants at a relatively high density and installation of containerized, more mature plants at a lower density. This study will examine three species of Carex frequently used in wetland restoration (Carex stipata, C. obnupta, and C. unilateralis) and compare the growth and mortality of mature versus juveniles of these species within Thomas Dairy Site in the Tualatin River Watershed. For phase 2, at Thomas Dairy Site, 13 randomly selected plots will each containing six subplots including a subplot planted with monocultures of each of the three plants, and two sizes (i.e., mature C. stipata, juvenile C. stipata, mature C. obnupta, juvenile C. obnupta, mature C. unilateralis, and juvenile C. unilateralis). These will be monitored for five years, during which mortality rates will be recorded once a year and total percent cover recorded three times a year. I hypothesize that the mature plants will have a higher percent cover after five years because juvenile plants are more susceptible to die over that timeframe and may have slower growth rates overall. Answering these questions will allow CWS and other wetland restoration managers to achieve greater plant coverage, reduce waste, and reduce costs.

Quantifying soil, microbial, and plant community changes following wetland restoration on private land

<p>Extensive global and national wetland loss has reduced ecosystem services to people and undermines the sustainability of ecosystems. Restoration projects aim to regain the biophysical conditions of remnant wetlands that produce an abundance of ecosystem services. Ecological restoration practices manipulate community succession to enhance ecological functions, and these different successional stages may be reflected in the soil physio-chemical characteristics, plants, and soil microbes, which in turn produce a variety of ecosystem services. Considerable potential for wetland restoration on private property exists in New Zealand, but it remains unknown how successful restoration is when undertaken through a landholder’s own prerogative. Relative to restoration of public land, private restoration projects are often small scale, personally funded and preference driven. In this thesis, I quantify the outcomes of small-scale private wetland restoration projects by measuring changes in plant and soil microbial communities, and soil physiochemical characteristics. I explore the relationships among variation in plant, soil and microbial datasets and test for causes of this variation. Using a paired sampling design, I sampled 18 restored wetlands and 18 unrestored wetlands on private property in the Wairarapa region. I used a Whitaker plot design to sample wetland plant communities at multiple scales and took soil samples that I analysed for physio-chemical properties. Additionally, I quantified the biomass and community composition of the microbes in the soil samples using phospholipid fatty acid analysis. In my second chapter, I use linear mixed-effect models, principal components analysis, and non-metric multidimensional scaling to ask: How does wetland restoration alter the plant community, soil physio-chemical characteristics, and the soil microbial community? In my third chapter, I employ Procrustes analysis to look at the association of variation in plants, microbes, and soil characteristics to explore whether successional processes of these attributes are concurrent within wetlands. I then use hierarchical cluster analysis to determine which of the wetlands are at similar successional stages and identified site contexts and restoration treatments that were in common among similar wetlands. These analyses provide insight to the conditions that advance successional processes in restored wetlands. Specifically, I ask 1) How do plant, microbial, and soil characteristics co-vary during wetland restoration? 2) How do indicators of wetland succession respond to restoration? 3) Are different restoration practices and site contexts influencing wetland outcomes during restoration? Private wetland restoration enhanced succession in plant, soil, and microbial properties towards those more similar to undisturbed wetland conditions. Specifically, restoration added ~13 native plant species, increased totalfungal and arbuscular mycorrhizal biomass, and total microbial biomass by 25%. Restoration increased soil moisture by 93%, soil organic carbon by 20%, and saturated hydraulic conductivity by 27%. It also reduced bulk density by 0.19 g-1 cm3 and plant available phosphorus (Olsen P) by 23%. Procrustes analysis revealed a lack of congruence in the recovery of plant, microbial, and soil indicators of succession, signifying that the plant community succeeded faster than the microbial community and soil characteristics. Variation in soil and microbial properties separated restored wetlands into two groups of early and later succession wetlands, which was independent of the number of years since restoration began at the sites but corresponded to elements of wetland hydrology. Soil and microbial characteristics in hydrologically connected wetlands recovered more quickly following restoration than hydrologically isolated wetlands. Private restoration increased spatial heterogeneity of outcomes at the plot scale, which depended on site factors. My data suggests that private wetland restoration is effective in increasing plant, soil, and microbial characteristics that produce ecosystem services. Additionally, wetland restoration increased environmental heterogeneity and the capacity for ecosystem service delivery, which may contribute to increased resilience of the Wairarapa landscape.</p>

Ecological restoration of Wairio Wetland, Lake Wairarapa: The response of native wetland vegetation to eutrophication and revegetation management strategies

<p>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 nor negative effect on the plant community at Wairio with no significant changes in the 15 species recorded at the site. These results contrast other studies that have reported increases in biomass, reductions in biodiversity and common/introduced species outcompeting rare/native species. The short duration of the experiment and summer drought conditions may have obscured the above-ground visual responses of the plant community to nutrient addition; therefore further continuation of this experiment is advised. Previous low success rates of native tree plantings at Wairio Wetland have significantly hindered revegetation efforts at the site. Therefore the second study, conducted between July 2011 and January 2014 in Stage 3 of the wetland, further investigates the effects of various management treatments on establishment of native woody vegetation. The study involved monitoring 2,368 planted trees of eight native wetland tree/shrub species, including; Cordyline australis, Dacrycarpus dacridioides, Olearia virgata, Podocarpus totara, Coprosma robusta, Coprosma propinqua, Leptospermum scoparium, and Pittosporum tenuifolium. The trees were subjected to various planting treatments including the excavation or retention of topsoil, presence or absence of weedmats and presence or absence of nurse trees with spacing of 0.75m or 1.5m. Survival and growth of each tree was measured every six months over the 30 month experimental period. Results showed that interspecific competition and hydrology appeared to be the main processes influencing the establishment of native plantings at Wairio Wetland, with plant mortality greatest in the first year after planting. Waterlogging, in particular, was detrimental to establishment of all species at the site except D. dacridioides. Topsoil excavation and the planting of nurse trees at 1.5 m spacing was the most effective management treatment combination promoting survival of plantings at Wairio. However, the success of management treatments varied greatly between species at the site and had different impacts on plant growth. Topsoil excavation was beneficial to survival of D. dacridioides and C. robusta but detrimental to growth of C. australis, O. virgata, C. propinqua, P. tenuifolium and L. scoparium. The concurrent planting of nurse trees with focal trees was beneficial to the survival of D. dacridioides, growth of P. totara, and survival and growth of C. australis. The planting of nurse trees further apart at 1.5 m compared to 0.75 m had a positive effect on the survival of C. propinqua and P. tenuifolium, and survival and growth of L. scoparium. Weedmats were beneficial to survival of O. virgata and growth of L. scoparium but detrimental to growth of D. dacridioides. These management treatments can be used in future revegetation efforts at Wairio Wetland, and potentially in other wetland restoration projects throughout New Zealand.</p>

Ecological restoration of Wairio Wetland, Lake Wairarapa: The response of native wetland vegetation to eutrophication and revegetation management strategies

<p>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 nor negative effect on the plant community at Wairio with no significant changes in the 15 species recorded at the site. These results contrast other studies that have reported increases in biomass, reductions in biodiversity and common/introduced species outcompeting rare/native species. The short duration of the experiment and summer drought conditions may have obscured the above-ground visual responses of the plant community to nutrient addition; therefore further continuation of this experiment is advised. Previous low success rates of native tree plantings at Wairio Wetland have significantly hindered revegetation efforts at the site. Therefore the second study, conducted between July 2011 and January 2014 in Stage 3 of the wetland, further investigates the effects of various management treatments on establishment of native woody vegetation. The study involved monitoring 2,368 planted trees of eight native wetland tree/shrub species, including; Cordyline australis, Dacrycarpus dacridioides, Olearia virgata, Podocarpus totara, Coprosma robusta, Coprosma propinqua, Leptospermum scoparium, and Pittosporum tenuifolium. The trees were subjected to various planting treatments including the excavation or retention of topsoil, presence or absence of weedmats and presence or absence of nurse trees with spacing of 0.75m or 1.5m. Survival and growth of each tree was measured every six months over the 30 month experimental period. Results showed that interspecific competition and hydrology appeared to be the main processes influencing the establishment of native plantings at Wairio Wetland, with plant mortality greatest in the first year after planting. Waterlogging, in particular, was detrimental to establishment of all species at the site except D. dacridioides. Topsoil excavation and the planting of nurse trees at 1.5 m spacing was the most effective management treatment combination promoting survival of plantings at Wairio. However, the success of management treatments varied greatly between species at the site and had different impacts on plant growth. Topsoil excavation was beneficial to survival of D. dacridioides and C. robusta but detrimental to growth of C. australis, O. virgata, C. propinqua, P. tenuifolium and L. scoparium. The concurrent planting of nurse trees with focal trees was beneficial to the survival of D. dacridioides, growth of P. totara, and survival and growth of C. australis. The planting of nurse trees further apart at 1.5 m compared to 0.75 m had a positive effect on the survival of C. propinqua and P. tenuifolium, and survival and growth of L. scoparium. Weedmats were beneficial to survival of O. virgata and growth of L. scoparium but detrimental to growth of D. dacridioides. These management treatments can be used in future revegetation efforts at Wairio Wetland, and potentially in other wetland restoration projects throughout New Zealand.</p>

Hydrological and chemical characteristics of Matthews Lagoon and Boggy Pond, Wairarapa: Essential information for the decision making process of wetland restoration

<p>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 ten 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 different 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 are located at the eastern edge of Lake Wairarapa in the Wellington Region. They formed as a result of the deposition of sanddunes 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% 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% 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.</p>

Hydrological and chemical characteristics of Matthews Lagoon and Boggy Pond, Wairarapa: Essential information for the decision making process of wetland restoration

<p>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 ten 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 different 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 are located at the eastern edge of Lake Wairarapa in the Wellington Region. They formed as a result of the deposition of sanddunes 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% 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% 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.</p>