No description available.

This study looks at relationships along the hydrologic gradient between and within six pools; including the vegetation community, soil characteristics and hydrology. Pool conditions were monitored weekly throughout the 2011 and 2012 growing seasons. Each pool was equipped with permanent platinum-tipped redox probes to quantify the severity and duration of soil reduction. We described and analyzed 12 soil profiles in each pool, distributed in summit/upland, basin, and rim/transition positions as defined by the high water line. The pools were systematically surveyed for understory vegetation during the 2012 growing season. Vegetation patterns varied between study areas. No clear pattern of unique vegetation was evident from an ordination of the gradient communities. Time series redox potential data showed a visual relationship to water table fluxuation, but also a dampening effect from soil organic matter content in the basin positions.

Northern peatlands have acted as persistent sinks of CO2 throughout the Holocene largely owing to their ability to maintain shallow water table depths that limit decomposition rates and supports the growth of keystone vegetation including Sphagnum mosses. There is concern, however, that the future success and ecosystem function of these northern peat deposits may be at risk to climate change, where temperatures and evaporation rates are predicted to increase substantially in the next century. While numerous studies have examined the hydrology and carbon dynamics in large expansive peatland systems where a water table (WT) is ever-present, relatively little research has been done on small scale peat-accumulating systems where their vulnerability remains unknown. One region where a broad spectrum in the scale of peat accumulation is present is in the bedrock depressions of Canadian Shield rock barrens, which are of special importance as many peat deposits here provide habitat to species at risk including the Blanding’s Turtle and the Massassauga Rattlesnake. This study examines the controls that govern water storage dynamics and moss water availability in 18 different peat-accumulating depressions that vary in size, catchment area, and sediment composition. The magnitude of WT variability was often several times greater in shallower bedrock depressions (<50 cm deep) as compared to deeper ‘bogs’ (>60 cm deep). The magnitude of depression WT variability appeared to be closely linked to the WT depth (WTD), the relative proportions of different sediment types within the depression, and the depth dependant specific yield (Sy) of each sediment type. Sites which contained large fractions of Polytrichum moss or mineral soil – which were more common in shallow depressions ¬¬– had the greatest WT variability due to the lower porosity and Sy of this sediment as compared to Sphagnum peat. Sphagnum dominated ‘vernal pools’ (30-50 cm deep) had a WT variability two to three times greater than Sphagnum dominated bogs at WTDs > 20-25 cm, which may be related to exceptionally high ash concentrations near the base of vernal pools which reduced peat porosity and Sy as compared to more organic-rich peat. As compared to bogs, pits (<15 cm deep) and vernal pools had greater rates of WT decline during drying intervals, deeper average WTDs when a WT was present, and extended periods of WT absence during the summer months. As such, moss growing in pits and vernal pools generally had lower near-surface water availability as compared to bogs, though the importance of depression depth in determining the timing of moss stress is also dependant on the hydrophysical properties (Kunsat and moisture retention) of the moss species in question. WT dynamics and moss water availability were generally weakly correlated to depression catchment size, although during wetter periods of the year the rate of WT recession was moderated in pits and vernal pools which had an upslope depression that could provide sustained water inputs for multiple days after rainfall. The results of this study suggest that depression depth may be a first order control in determining peatland vulnerability to future regime shifts induced by external forcings or disturbances. Furthermore, this study suggests that systematic differences may exist between the hydrophysical properties of peat in shallow vs. large bedrock depressions, potentially resulting from contrasts in fire frequency/severity, and/or the degree of humification/compression among geological settings. / Thesis / Master of Science (MSc) / Canada is home to one of the largest reservoirs of organic carbon stored on land in the world, in unique ecosystems called peatlands. Peatlands are formed in wetland environments where a thick layer of organic matter has accumulated over time due to the average rate of vegetation growth on the surface of peatlands exceeding the rate of decomposition of the underlying organic matter. This net accumulation of organic matter over time has caused peatlands to act as a long term sink of carbon dioxide, which is a greenhouse gas that is a primary driver of global warming. The ability of peatlands to have slow decomposition rates and support the growth of key peatland vegetation, most notably various species of ‘peat moss’, is highly dependent upon their ability to keep their water table (i.e. the surface below which pore spaces in the organic matter are saturated with water) close to their growing surface. There is concern, however, that a warmer and dryer climate in the future could cause deeper water table positions in peatlands, thereby increasing decomposition rates, decreasing the growth rate of peat moss, and potentially turning peatlands into a net source of carbon dioxide. Most peatland studies to date, however, have focused on water storage/movement and carbon exchange in large, deep peatland systems, whereas relatively little research has been conducted on smaller peatlands. As such, the vulnerability of these smaller peatlands to future climate change remains uncertain. One region where peatlands exist over a wide range of different sizes and landscape positions is in bedrock depressions of the Canadian Shield, which are of special interest as they also provide habitat for species at risk including the Blanding’s Turtle and the Massassauga Rattlesnake. This study looked at how the water table positions and water availability to different species of peat moss compared over the growing season between 18 peatlands of different sizes and landscape position (i.e. peatlands with a relatively ‘small’ and ‘large’ area upslope of them). This study finds that deeper peatlands (with organic matter layers > 60 cm deep) usually had a shallower water table over the summer months than shallower peatlands (< 50 cm deep), primarily due to differences in the properties of the organic matter underlying their growing surfaces. Furthermore, each of the 12 studied peatlands < 50 cm deep lost their water table for a considerable amount of time during the summer (when their water table position dropped below the underlying bedrock of the depression), whereas each of the six peatlands > 60 cm deep had a water table present for the entire growing season. Surprisingly, a peatland’s position on the landscape seemed to have a relatively minor effect on determining the depth/presence of its water table. As deeper peatlands usually had a water table that was closer to the growing surface and was always present, more moisture was available to the peat moss growing at their surface than for peat moss in shallower depressions, though this moisture availability also depended upon the growth form of the different species of peat moss (some species of peat moss were better at accessing subsurface water than others). Through its impact on water table positions and moisture availability for peat moss, peatland depth is likely a primary control governing peatland vulnerability climate change, with shallower peatlands being more vulnerable to warmer and dryer conditions in the future.

In this study, I used restriction fragment length polymorphism (RFLP) analysis (DNA fingerprinting) to study the genetic population structure of wood frogs, Rana sylvatica, collected as egg masses from vernal pools within the Massachusetts Audubon Society Lincoln Woods Wildlife Sanctuary in Leominster, MA. The average genetic relatedness of sibling individuals, non-sibling individuals from within the same pool, and individuals from pools of close (5 m), far (200 m) and distant (40 km) spatial separations was calculated. The goal was to use genetic relatedness to estimate the breeding patterns of R. sylvatica and use that information to make general management recommendations that could be applied to other vernal pools breeders. I detected relative differences in genetic similarity between individuals from pools only 5 meters apart, however over a larger distance of 200 meters no significant genetic differences were present. This suggests that although wood frogs are known to be highly philopatric, they may use information other than simply proximity to their natal pool when choosing breeding sites. Factors such as species composition, water chemistry and heterogeneity of the landscape between pools may influence breeding site choice. Also, contrary to the findings of recent studies, the distance between vernal pools may not be the best indicator of the genetic similarity of the individuals they host. Pools in close proximity to one another may host genetically distinct populations, and therefore management decisions should be made on a pool-by-pool basis. Consequently, when managing populations of R. sylvatica, and possibly other vernal pool breeders, taking into account parameters other than simply the spatial separation of pools within an array may avoid decisions that could result in the loss of genetic diversity.

Zugl.: Freiburg (Breisgau), Univ., Diss.

The number of California vernal pools and vernal lakes are diminishing. Through the present study, this investigator hopes to increase the understanding of vernal pool biota, as well as the awareness that these unique habitats need protection. Other studies of California vernal pools have emphasized their flora, their plankton and their physicochemical aspects. The purpose of this investigation is to survey the insects and other macrofauna found in two vernal lakes of eastern Stanislaus County, to examine the phenology of the insects within one of these lakes, and to compare the insect taxa found in these vernal lakes to those reported from studies of similar vernal pools.

Vernal pools are small, seasonally filling wetlands found throughout forests of north eastern North America. Vernal pools have been proposed as potential 'hot spots' of carbon cycling. A key component of the carbon cycle within vernal pools is the decomposition of leaf litter. I tested the hypothesis that leaf litter decomposition is more rapid within vernal pools than the adjacent upland. Leaf litter mass losses from litterbags incubated in situ within vernal pools and adjacent upland habitat were measured periodically over one year and then again after two years. The experiment was carried out at 24 separate vernal pools, over two replicate years. This is a novel degree of replication in studies of decomposition in temporary wetlands. Factors influencing decomposition, such as duration of flooding, water depth, pH, temperature, and dissolved oxygen were measured. Mass loss was greater within pools than adjacent upland after 6 months, equal after 12 months, and lower within pools than adjacent upland after 24 months. This evidence suggests that vernal pools of Central Ontario are 'hot spots' of decomposition up to 6 months, but not after 12 and 24 months. In the long term, vernal pools may reduce decomposition rates, compared to adjacent uplands.

Ephemeral wetlands provide numerous ecosystem services, but are disappearing due to urbanisation and habitat fragmentation. Knowledge is required to conserve these systems, but ephemeral wetland research in South Africa is lacking. As primary producers, microalgae provide a key link between the biotic and abiotic components of aquatic ecosystems. Despite their importance, there is a paucity in information concerning microalgal dynamics in ephemeral wetlands. The aim of this study was to understand the spatial and temporal dynamics of microalgae in ephemeral wetlands of the Nelson Mandela Bay Metropole. The research followed a funnel-based approach that assessed 35 wetlands at a regional level, followed by a temporal assessment of six wetlands, monitored biweekly, monthly or quarterly. Thereafter, a case study at local scale was carried out to address wetland connectivity and Hydrogeomorphic unit trends. The research culminated in a benthic flux chamber experiment, addressing the influence of microalgal-mediated processes on wetland development for a month post inundation. Phytoplankton biomass showed strong regional associations with rainfall zone, with Chl a concentrations of 17; 4.6; and 25 µg.L-1 in the high, intermediate and low rainfall zones, respectively. The MPB communities in Seeps, Depressions and Wetland flats, comprised between 45 and 60 % diatoms, whilst other microalgal groups were dominant in the water columns (> 90 %). Phytoplankton and MPB interactions facilitated significant night-time NH4+ and SRP effluxes, (1.5 and 0.4 mg.m-2.h-1, respectively) four days post inundation. High Silica uptake in the latter stages, was attributed to an increase in diatom abundance. Within the chambers, MPB growth was continuous whilst phytoplankton exhibited cyclical growth as the system approached dynamic equilibrium. This study demonstrated the importance of nutrient cycling in structuring aquatic food webs, and indicated the sensitivity of ephemeral wetlands to environmental perturbations.

No description available.