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CURATOR
A pinboard by
Rebekah Grieger

PhD candidate, Griffith University

PINBOARD SUMMARY

Globally coastal wetlands are being threatened by the effects of climate change. Rising sea levels, increased temperatures, and increased severity of storms are known to have detrimental effects on mangrove forests and saltmarsh ecosystems worldwide. However, much less is known about coastal freshwater wetlands (especially in Australia) and even less in known about the effects that a changing climate will have. Coastal freshwater wetlands are wetlands in the coastal vicinity that are dominated by freshwater flows and have little tidal influence; e.g. forested swamps and coastal lagoons. Very little study has been conducted on these systems (apart from work in North America) and they are rapidly vanishing due to clearing for agriculture and urban development. Identifying the resilience of vegetation in these systems is vital to understanding their restoration potential and their future distribution within the coastal landscape. My research aims to 1) investigate the vegetation distribution of coastal freshwater wetlands within Queensland, Australia, 2) investigate the role of the soil seed bank in vegetation dynamics, 3) investigate the restoration potential of species emerging from the soil seed bank and, 4) identify the influence that climate change will have on vegetation dynamics and regeneration.

4 ITEMS PINNED

Coastal Freshwater Wetland Plant Community Response to Seasonal Drought and Flooding in Northwestern Costa Rica

Abstract: Wetlands in tropical wet-dry climates are governed by distinct and extreme seasonal hydrologic fluctuations. In this study, we investigated the plant community response to seasonal flooding and drought in Palo Verde Marsh, Costa Rica. Climate change models for the region predict reduced rainfall and a drier wet season which would likely alter seasonal hydrologic cycles and prompt vegetation change. We quantified compositional change following disturbance emphasizing seasonal differences in plant life-form abundance across life history stages via standing vegetation, seed bank, and seedling recruitment measurements. Whereas the dry season standing vegetation was dominated by emergent species, aquatic species (floating-rooted, free-floating, and submerged life forms) were more dominant during the wet season. Seed bank and seedling recruitment measurements indicated that many species are resilient with life history traits that enable them to respond rapidly to extreme hydrologic filters. Interestingly, species richness was highest during seasonal flooding. Our results highlight the importance of early-wet season rainfall for plant regeneration and community change. Our findings also indicate that a drier future would likely have a large impact upon wetland plant communities with a decrease in species richness and an increase in the abundance of drought-tolerant emergent species.

Pub.: 05 May '11, Pinned: 31 Aug '17

Processes Contributing to Resilience of Coastal Wetlands to Sea-Level Rise

Abstract: Abstract The objectives of this study were to identify processes that contribute to resilience of coastal wetlands subject to rising sea levels and to determine whether the relative contribution of these processes varies across different wetland community types. We assessed the resilience of wetlands to sea-level rise along a transitional gradient from tidal freshwater forested wetland (TFFW) to marsh by measuring processes controlling wetland elevation. We found that, over 5 years of measurement, TFFWs were resilient, although some marginally, and oligohaline marshes exhibited robust resilience to sea-level rise. We identified fundamental differences in how resilience is maintained across wetland community types, which have important implications for management activities that aim to restore or conserve resilient systems. We showed that the relative importance of surface and subsurface processes in controlling wetland surface elevation change differed between TFFWs and oligohaline marshes. The marshes had significantly higher rates of surface accretion than the TFFWs, and in the marshes, surface accretion was the primary contributor to elevation change. In contrast, elevation change in TFFWs was more heavily influenced by subsurface processes, such as root zone expansion or compaction, which played an important role in determining resilience of TFFWs to rising sea level. When root zone contributions were removed statistically from comparisons between relative sea-level rise and surface elevation change, sites that previously had elevation rate deficits showed a surplus. Therefore, assessments of wetland resilience that do not include subsurface processes will likely misjudge vulnerability to sea-level rise.AbstractThe objectives of this study were to identify processes that contribute to resilience of coastal wetlands subject to rising sea levels and to determine whether the relative contribution of these processes varies across different wetland community types. We assessed the resilience of wetlands to sea-level rise along a transitional gradient from tidal freshwater forested wetland (TFFW) to marsh by measuring processes controlling wetland elevation. We found that, over 5 years of measurement, TFFWs were resilient, although some marginally, and oligohaline marshes exhibited robust resilience to sea-level rise. We identified fundamental differences in how resilience is maintained across wetland community types, which have important implications for management activities that aim to restore or conserve resilient systems. We showed that the relative importance of surface and subsurface processes in controlling wetland surface elevation change differed between TFFWs and oligohaline marshes. The marshes had significantly higher rates of surface accretion than the TFFWs, and in the marshes, surface accretion was the primary contributor to elevation change. In contrast, elevation change in TFFWs was more heavily influenced by subsurface processes, such as root zone expansion or compaction, which played an important role in determining resilience of TFFWs to rising sea level. When root zone contributions were removed statistically from comparisons between relative sea-level rise and surface elevation change, sites that previously had elevation rate deficits showed a surplus. Therefore, assessments of wetland resilience that do not include subsurface processes will likely misjudge vulnerability to sea-level rise.

Pub.: 08 Jul '16, Pinned: 31 Aug '17

Integration, synthesis and climate change adaptation: a narrative based on coastal wetlands at the regional scale

Abstract: The idea that integration and synthesis are critical for designing climate change adaptation and mitigation is well entrenched conceptually. Here, we review the concepts of adaptation, synthesis and integration and apply them to the case study of coastal wetlands in South East Queensland, Australia. The distribution and condition of coastal wetlands will change as climate changes. This will create conservation challenges and economic costs, but these can be minimised by drawing from a broad sectoral perspective in undertaking adaptation planning and by ensuring integration into policy. Our review indicates that adaptations to sea level rise that are focussed on wetland and biodiversity conservation are likely to have impacts for urbanisation patterns. Planning regulations that provide spatial buffering around wetlands may give rise to more compact urban forms that may lead to reductions in the cost of defence against sea level rise, reduce energy usage per person and provide more green space. However, more compact urban forms could exacerbate heat island effects and place greater burden on the economically disadvantaged as, for example, single-family homes become more expensive. Planning for climate change needs to balance these equity and cross-sectoral issues in order to reduce the likelihood of unforeseen negative consequences.

Pub.: 23 Dec '11, Pinned: 31 Aug '17

Factors affecting soil seed banks of riparian communities in an agricultural ecosystem: potential for conservation of native plant diversity

Abstract: Do agricultural land use and nitrogen (N) enrichment have negative effects on riparian soil seed banks? What is the potential of the soil seed bank for the conservation and restoration of native riparian plant diversity? Are non-native dominant grass species affected by agriculture and do they affect species richness?South Nation River watershed (an agricultural watershed), Ontario, Canada.We examined the riparian above-ground vegetation at 24 sites located across a large (~4000 km2) North American watershed and identified the corresponding soil seed bank composition from soil cores using the seedling emergence method. The above-ground vegetation and soil seed bank species compositions were compared in terms of species richness, percentage of non-native species and a floristic quality index. Factors affecting these descriptors of plants communities (concentration of in-stream nitrate and percentages of surrounding natural habitat and annual crop land) were assessed. The effects of agriculture on two dominant non-native grasses species and their effects on species richness were also assessed.In total, 274 plant taxa were identified, including 181 taxa in the soil seed bank and 231 taxa in the vegetation. Overall species richness was high in both the soil seed bank and above-ground vegetation and was unaffected by measures of agricultural intensity (surrounding annual crop land and N enrichment). Above-ground vegetation species richness was strongly negatively affected by the widespread and dominant non-native grasses, Phalaris arundinacea and Bromus inermis, whereas soil seed bank species richness was unaffected. The community compositions of both the soil seed bank and vegetation were negatively affected by the loss of natural habitat and by N enrichment. In fact, an increase in the percentage of non-native species and a decrease in floristic quality were observed along a gradient of agricultural intensity.Species richness of the soil seed bank demonstrated resilience to invasions by P. arundinacea and B. inermis, and the soil seed bank showed good potential for conservation of taxonomic diversity. However, the loss of natural habitat and N enrichment had negative effects on the soil seed bank community composition that may lead to an eventual decline in above-ground species richness.

Pub.: 25 May '17, Pinned: 31 Aug '17