Ecological Restoration of the Wairio Wetland, Lake Wairarapa: Water Table Relationships and Cost-Benefit Analysis of Restoration Strategies

<p>The world’s wetlands are known for being highly productive environments and supporting significant numbers of fauna and flora species that rely on the wetland’s primary productions for survival. However, they were historically used by humans for hunting and fishing, wetlands were considered wastelands, best used when drained and filled for agricultural, industrial and residential development. Despite now having a greater understanding of wetlands and their ecological importance, degradation of wetlands continues, mainly due to anthropogenic activities. Wetland restoration involves reconstructing natural sites that have been degraded or completely lost and re-establishing their functions and values as vital ecosystems. Important restoration components include control of invasive weeds, emphasis on the presence of locally native species and restoration of the hydrological component. The Wairio wetland is part of the largest wetland complex in the southern North Island and supports a number of native flora and fauna, of national and international importance. Wairio wetland has been destroyed by the effects of partial draining, unnatural hydrological control, clearing of native forest, construction of Parera Road separating once joined wetlands and the establishment of invasive willow trees and agricultural grasses. The co-management by the Department of Conservation and Ducks Unlimited, commenced in 2005, has begun a positive shift for the wetland. However, issues still remain due to the majority of the wetland still being used for farming, so there is no continuity between the three fenced restoration stages; artificial hydrological flow and water storage; and established willow trees along the wetland boundary. Most ephemeral wetland vegetation displays a strong pattern of zonation, through a sequence from open water to dry land, which is correlated in some way with the duration and periodicity of water inundation. This hydrosere reflects differences in the degree of adaptation to aquatic life of different plant species. Two studies are reported here, conducted in two areas at the Wairio wetland over two desiccation periods. The first study conducted during 2010/2011 at stage one, focused on determining the environmental conditions of peak abundance and limits to distribution of key native and exotic plant species along an environmental (hydrological) gradient. The second study, conducted in 2012 at stage three, further investigated the effect of topsoil removal on the plant community and was a comparison study with the initial study at stage one. Results indicated that the Wairio wetland plant communities display strong zonation patterns progressing from aquatic species, to turf communities, to exotic grass species. Over the two desiccation periods studied it was found that the introduced species most abundant in low soil moisture were common pasture grasses, especially yorkshire fog (Holcus lanatus), brown top (Agrostis capillaris) and tall fescue (Schedonorus arundinaceus) as well as purple clover (Trifolium pratense) and the high soil moisture invasive competitor was water plantain (Alisma spp.). We also found that topsoil excavation impacts the plant community; topsoil scraping in the high soil moisture areas leads to a more native dominated plant community, with the dominant species being water plantain (Alisma spp.) and Isolepis prolifera, but scraping in relatively low soil moisture areas encourages the exotic grass weed species to grow. Wairio wetland on the Eastern shore of Lake Wairarapa has been adversely affected by anthropogenic activities since the 1960s. In 2005, Ducks Unlimited and the Department of Conservation signed a Land Management Agreement where Ducks Unlimited would commence the restoration of the wetland. Survival of trees planted during the first few years was variable. Here, I report on the design and monitoring of a large scale field experiment involving the planting of around 2,500 trees of eight native wetland tree species Dacrycarpus dacrydioides, Podocarpus totara, Cordyline australis, Olearia virgata, Pittosporum tenuifolium, Coprosma robusta, Coprosma propinqua and Leptospermum scoparium. The trees were subjected to different methods of site preparation and aftercare to determine the best combination of treatments for successful establishment of tree saplings. Treatments included the use or non-use of topsoil excavation, release spraying, weedmats, nurse trees (with two combinations of species) and different spacing between the nurse species. Survival and growth over the first six months was monitored. Preliminarily results showed survival of O. virgata and P. totara was influenced by surface water, but few immediate effects of treatments upon growth rates. Olearia virgata, however, grew best in wet areas that had been scraped free of topsoil or drier areas that had not been scraped. Monitoring over the next 18 months will give us a better understanding of which is the most costeffective combination of treatments. Early indications suggest high level survival under all treatments.</p>

Ecological Restoration of the Wairio Wetland, Lake Wairarapa: Water Table Relationships and Cost-Benefit Analysis of Restoration Strategies

<p>The world’s wetlands are known for being highly productive environments and supporting significant numbers of fauna and flora species that rely on the wetland’s primary productions for survival. However, they were historically used by humans for hunting and fishing, wetlands were considered wastelands, best used when drained and filled for agricultural, industrial and residential development. Despite now having a greater understanding of wetlands and their ecological importance, degradation of wetlands continues, mainly due to anthropogenic activities. Wetland restoration involves reconstructing natural sites that have been degraded or completely lost and re-establishing their functions and values as vital ecosystems. Important restoration components include control of invasive weeds, emphasis on the presence of locally native species and restoration of the hydrological component. The Wairio wetland is part of the largest wetland complex in the southern North Island and supports a number of native flora and fauna, of national and international importance. Wairio wetland has been destroyed by the effects of partial draining, unnatural hydrological control, clearing of native forest, construction of Parera Road separating once joined wetlands and the establishment of invasive willow trees and agricultural grasses. The co-management by the Department of Conservation and Ducks Unlimited, commenced in 2005, has begun a positive shift for the wetland. However, issues still remain due to the majority of the wetland still being used for farming, so there is no continuity between the three fenced restoration stages; artificial hydrological flow and water storage; and established willow trees along the wetland boundary. Most ephemeral wetland vegetation displays a strong pattern of zonation, through a sequence from open water to dry land, which is correlated in some way with the duration and periodicity of water inundation. This hydrosere reflects differences in the degree of adaptation to aquatic life of different plant species. Two studies are reported here, conducted in two areas at the Wairio wetland over two desiccation periods. The first study conducted during 2010/2011 at stage one, focused on determining the environmental conditions of peak abundance and limits to distribution of key native and exotic plant species along an environmental (hydrological) gradient. The second study, conducted in 2012 at stage three, further investigated the effect of topsoil removal on the plant community and was a comparison study with the initial study at stage one. Results indicated that the Wairio wetland plant communities display strong zonation patterns progressing from aquatic species, to turf communities, to exotic grass species. Over the two desiccation periods studied it was found that the introduced species most abundant in low soil moisture were common pasture grasses, especially yorkshire fog (Holcus lanatus), brown top (Agrostis capillaris) and tall fescue (Schedonorus arundinaceus) as well as purple clover (Trifolium pratense) and the high soil moisture invasive competitor was water plantain (Alisma spp.). We also found that topsoil excavation impacts the plant community; topsoil scraping in the high soil moisture areas leads to a more native dominated plant community, with the dominant species being water plantain (Alisma spp.) and Isolepis prolifera, but scraping in relatively low soil moisture areas encourages the exotic grass weed species to grow. Wairio wetland on the Eastern shore of Lake Wairarapa has been adversely affected by anthropogenic activities since the 1960s. In 2005, Ducks Unlimited and the Department of Conservation signed a Land Management Agreement where Ducks Unlimited would commence the restoration of the wetland. Survival of trees planted during the first few years was variable. Here, I report on the design and monitoring of a large scale field experiment involving the planting of around 2,500 trees of eight native wetland tree species Dacrycarpus dacrydioides, Podocarpus totara, Cordyline australis, Olearia virgata, Pittosporum tenuifolium, Coprosma robusta, Coprosma propinqua and Leptospermum scoparium. The trees were subjected to different methods of site preparation and aftercare to determine the best combination of treatments for successful establishment of tree saplings. Treatments included the use or non-use of topsoil excavation, release spraying, weedmats, nurse trees (with two combinations of species) and different spacing between the nurse species. Survival and growth over the first six months was monitored. Preliminarily results showed survival of O. virgata and P. totara was influenced by surface water, but few immediate effects of treatments upon growth rates. Olearia virgata, however, grew best in wet areas that had been scraped free of topsoil or drier areas that had not been scraped. Monitoring over the next 18 months will give us a better understanding of which is the most costeffective combination of treatments. Early indications suggest high level survival under all treatments.</p>

Taxonomic and phylogenetic composition show biotic resistance to exotic invasion in acid seep springs

Background Few studies have incorporated the evolutionary insights provided by analysis of phylogenetic structure along with community composition to assess the effects of exotic invasion on freshwater wetlands. Here, we assess the taxonomic and phylogenetic relationships among acid seep springs to investigate the potential homogenization or resistance of communities due to invasion of an exotic grass. Results Multivariate community analyses indicated differences in community and phylogenetic composition and dispersion among acid seep springs, associated with gradients in soil moisture, canopy cover, and phylogenetic diversity. By contrast, univariate analyses showed differences in taxonomic diversity but not phylogenetic diversity among acid seep springs. Conclusions Despite exotic invasion, individual acid seep springs remained taxonomically and phylogenetically distinct from each other. Taxonomic and phylogenetic diversity metrics revealed different aspects of composition, reinforcing the importance of including both in analyses of plant communities for understanding community assembly following exotic invasion and for management purposes. Within acid seep springs, taxonomic and phylogenetic composition appear to be driven more through environmental filtering by light and moisture than by the competitive effects following invasion of an exotic grass in support of Elton’s biotic resistance hypothesis.

Reductions in foliar Hemiptera in portions of a fescue grassland invaded by Smooth Brome (Bromus inermis)

Fescue grassland in Canadian prairie is characterized by Plains Rough Fescue (Festuca hallii), but the introduced exotic grass, Smooth Brome (Bromus inermis), is expanding therein. Hemiptera play an important role as herbivores in vegetation. In an invaded fescue grassland in Manitoba, 52 plant species had a combined average cover of 216%. Kentucky Bluegrass (Poa pratensis), another exotic grass, was most abundant at 64%, followed by B. inermis at 21% and the native grass F. hallii at 18%. Across 47 random sample points, B. inermis cover ranged from 0% to 180%. At these points, 2445 specimens of Hemiptera were collected by sweep net and divided into 99 morphologically distinct species. Bromus inermis cover had negative correlations with Hemiptera species richness and diversity, but not with abundance and biomass of Hemiptera. However, B. inermis cover was negatively correlated with abundance of two individual species of Hemipteran leafhoppers in the family Cicadellidae: Doratura stylata and Diplocolenus configuratus. Total graminoid cover had no significant correlation with any of the above Hemiptera variables. We conclude that feeding requirements deter some phytophagous Hemiptera from entering sections of fescue grassland invaded by B. inermis. In this way, invasion by B. inermis can be expected to modify ecosystem function by increasing feeding pressure on neighbouring natural vegetation and other introduced species.

Long-Term Seeding Outcomes in Slash Piles and Skid Trails after Conifer Removal

Conifer removal in interior woodland ecosystems of the western US is a common management treatment used to decrease fire hazard and shift woodlands to more historical states. Woody material is frequently removed by skidding material off site and via slash pile burning. Assessing the long-term outcomes of seeding treatments after such ground disturbing activities is critical for informing future management and treatment strategies. Using two designed experiments from a central Oregon juniper woodland, we resampled slash piles and skid trails 8 years after seeding. Our objectives were to assess the long-term vegetation response to conifer removal, ground disturbance, and seeding source (cultivar and local) in slash piles and skid trails. We found that seeded species persisted in the long term, but abundance patterns depended on the species, seed source, and the type of disturbance. In general, there were more robust patterns of persistence after pile burning compared to skid trails. Seeding also suppressed exotic grass cover in the long term, particularly for the local seed source. However, the invasion levels we report are still problematic and may have impacts on biodiversity, forage and fire behavior. Our short-term results were not predictive of longer-term outcomes, but short- and long-term patterns were somewhat predictable based on species life history traits and ecological succession. The use of a mix of species with different life history traits may contribute to seeding success in terms of exotic grass suppression. Lastly, our results suggest that locally adapted seed sources may perform as well or better compared to cultivars. However, more aggressive weed treatments before and after conifer removal activities and wider seeding application may be needed to effectively treat exotic grass populations.

IMPACT OF CLIMATE CHANGE ON THE POTENTIAL DISTRIBUTION OF NATIVE AND INVASIVE GRASSES IN THE CERRADO

Biological invasion, mainly by African grasses, is one of the main threats to the Cerrado's biodiversity. The objective of this study was to elucidate the distribution patterns of the exotic grass Melinis minutiflora and the native grass Trichanthecium cyanescens, in order to verify the areas of potential occurrence of these species and, thus, to infer if their potential distribution will be affected by climate changes. Species occurrence data and ten uncorrelated climatic variables referring to the forecasts for the current period and future forecasts (2050 and 2070) were used for the analysis of the modeling. The models indicated the existence of environmental suitability, with AUCs above 0.8 (good) being observed in M. minutiflora and above 0.9 (excellent) in T. cyanescens. It is concluded that climate change may have negative impacts on the geographic distribution of these species, reducing the area of environmental suitability for them. In addition, the species studied have similar areas of potential distribution and regularly overlap, which can make M. minutiflora a threat to the conservation of T. cyanences, due to the invasion potential of the first.