106 research outputs found
Soil physical impacts and recovery rates following human-induced disturbances in the Ross Sea region of Antarctica
No full textWith increasing visitor numbers an understanding of the impacts of human activities on Antarctic soil environments has become an important issue. The overall objective of this thesis was to investigate soil physical impacts, and soil recovery rates, following human disturbance in the Ross Sea region of Antarctica. Visually disturbed and nearby control sites were assessed using a combination of techniques, including field-based visual site assessments, comparative photo-records, a desert pavement recovery assessment method, soil sampling, and soil dry bulk density measurements. An experimental soil disturbance trial was set up near Scott Base and bacterial DNA profiling was used to investigate the response of communities to removal of the top 2 cm of soil. Infra-red track counters were installed on Ross Island walking tracks to record visitor use over a two-year period.
Five case studies, from former research stations to field campsites, were investigated to assess the accuracy of the impacts predicted in environmental impact assessments and the observed impacts. In all cases there was a high level of consistency between predicted and observed impacts. It was apparent that the environmental impact assessment process raised environmental awareness of visitors; motivating them to avoid, remedy, or mitigate, their environmental impacts.
A field-based method was developed to assess desert pavement recovery and tested on 54 sites. Eleven criteria were used: embeddedness of surface clasts; impressions of removed clasts; degree of clast surface weathering; % overturned clasts; salt on underside of clasts; development of salt coatings; armouring per m2; colour contrast; evidence of subsidence/melt out; accumulation of salt on cut surfaces; and evidence of patterned ground development. Recovery criteria were assigned a severity rating on a scale from zero to four, and the Mean Recovery Index (MRI) of the site was calculated relative to an equivalent control. Five recovery stages were defined as recently or highly disturbed (MRI of 0-24%), through to indistinguishable from control site (MRI = 100%). Fifty of the 54 sites investigated were in an intermediate or higher stage of desert pavement recovery (MRI > 50%), 30 sites were in an advanced stage of recovery (MRI > 75%), and four sites were indistinguishable from adjacent control sites (MRI = 100%). Active surfaces, such as gravel beach deposits, aeolian sand, and alluvial fan deposits, recovered relatively quickly and had higher MRIs, whereas less active sites of higher intensity disturbances, such as bulldozed tracks at Marble Point, had lower MRIs, with only intermediate recovery up to 50 years after disturbance.
Following physical impacts such as foot and vehicle traffic the surface recovery recorded here was often greater than that predicted by previous researchers. At one-off campsites, footprints from dispersed trampling were undetectable within five years. At some sites walking tracks remained visible in the landscape 17 years after they were formed (due to surface recontouring and larger clasts concentrating along track margins). For steep slopes and sites where repeated visits occur, use of a single track is recommended. At sites where visually obvious impacts were remediated by replacing larger stones back in their original positions, ensuring that surface stones are placed with the weathered side up, and raking of gravel sand-sized displaced materials, visible evidence of former occupation was almost undetectable. Concentrating activity on young, active, and readily recoverable surfaces, or resilient bedrock, is recommended.
There were no significant changes in bacterial community structure in response to experimental removal of the top 2 cm of soil over a 35 day sampling period. Differences in bacterial community structure between samples correlated with differences in soil electricity conductivity (R2 = 0.55) and soil pH (R2 = 0.67), reflecting small scale (< 2 m) soil heterogeneity.
Infrared track counters recorded: 5084 passes on the Scott Base to McMurdo Station walking track, 2842 on the Wind Vane Hill walking track, 3561 on the Round Observation Hill walking track, and 10936 on the Up Observation Hill track between January 2009 and January 2011. On the Crater Hill summit walking track there were 693 passes in 2009. Higher counts were recorded on all tracks in the 2010/2011 summer season, compared with the 2009/2010 summer, and the highest frequency of visitors occurred on Sundays in the summer months. Peak daily counts at the Wind Vane Hill track coincided with the arrival of tourist ships. There was no relationship between the number of passes on the track and the measured impacts, indicating that higher usage of a formed track had little cumulative impact. Track width and track incision were related to the slope of the terrain, with tracks traversing flatter areas generally wider (R² = 0.85) and less incised (R² = 0.96) than those traversing steeper hillsides. Soil dry bulk density was higher in the walking tracks compared with the adjacent control areas (p <0.05)
Investigation of air and soil climate across the latitudinal and altitudinal gradient of the Ross Sea region of Antarctica
No full textA soil climate station network in the Ross Sea region of Antarctica comprises; Cape Hallett (72.19°S, 2 m asl), Granite Harbour (77°S, 6 m asl), Victoria Valley (77.19°S, 408 m asl), Marble Point (77.25°S, 55 m asl), Bull Pass East (77.30°S, 833 m asl), Wright Valley (77.31°S, 155 m asl), Mt Fleming (77.32°S, 1690 m asl), Scott Base (77.50°S, 51 m asl), Minna Bluff (78.30°S, 28 m asl), and Darwin Glacier (79.50°S, 333 m asl). Variables measured include air and soil temperatures to 1.2 m depth, and wind speed and direction. The overall objectives of this study were to; investigate the trends in air and soil temperatures across latitudinal and altitudinal gradients from Cape Hallett (72°S) to Darwin Glacier (79.5°S), and from sea level to the edge of the Polar Plateau; quantify the cumulative number of days when air and soil temperatures were ≥0°C; and to analyse the wind data to characterise the wind regime at each site and to investigate storm events and diurnal patterns.
Mean annual air temperatures were, from warmest to coolest: Cape Hallett ( 15.3°C), Granite Harbour ( 16.6°C), Marble Point ( 17.6°C), Darwin Glacier ( 18.2°C), Minna Bluff ( 18.3°C), Scott Base ( 19.1°C), Wright Valley ( 19.6°C), and Victoria Valley ( 22.4°C). Two stations had a warming trend (P<0.05); Marble Point (in air, and in soil at 7.5 and 120 cm depth) and Granite Harbour (in soil at 5.5 cm depth). No significant trends of warming or cooling were observed at the Cape Hallett, Darwin Glacier, Minna Bluff, Scott Base, Wright Valley, Victoria Valley, or Mt Fleming sites. Shallow soil temperatures were warmer than air temperatures, apparently due to heating from solar radiation in summer, and snow insulation in winter.
The mean cumulative days/summer with air temperature ≥0°C ranged from: Wright Valley (33.3), Victoria Valley (22.3), Granite Harbour (10.4), Marble Point (9.7), Minna Bluff (7.6), Darwin Glacier (7.3), Scott Base (4.2), to Mt Fleming (0.0). In shallow soil (~5 cm depth), the mean cumulative number of days/summer with T≥0°C were: Wright Valley (69.8), Granite Harbour (69.6), Marble Point (55.5), Minna Bluff (52.8), Victoria Valley (50.2), Scott Base (34.6), Cape Hallett (32.2), to Mt Fleming (0.0). At the mid-depth soil (~20 cm depth), the overall cumulative numbers of days with T≥0°C were: Granite Harbour (65.5), Wright Valley (52.0), Marble Point (44.7), Minna Bluff (31.6), Cape Hallett (22.5), Scott Base (13.9), Victoria Valley (1.8), and Mt Fleming (0.0). There was no increasing or decreasing trend in the days with air or soil T≥0°C over the record period.
Mean annual wind speeds were: Darwin Glacier (45 kmhr-1), Minna Bluff (42 kmhr-1), Mt Fleming (29 kmhr-1), Scott Base (17 kmhr-1), Wright Valley (14 kmhr-1), Marble Point (12 kmhr-1), Victoria Valley (8 kmhr-1), and Granite Harbour (7 kmhr-1). The highest recorded mean hourly wind speed was 169 kmhr 1 at Minna Bluff in 2009. There was increasing wind speed with increased latitude (R2=0.59), but no relationship between wind speed and altitude. Controls on wind speed and direction were likely to be a combination of altitude, latitude, local topography, and cyclonic storms
Environmental Assessment of the Effects of Leachate Irrigation and Seepage from the Paokahu Landfill, Gisborne, New Zealand.
No full textPaokahu landfill operated near Gisborne from 1977 to 2002. About 1 million cubic metres of mixed domestic and industrial (predominantly food processing) wastes were disposed of at the site. The Paokahu landfill is located on the Poverty Bay Flats on low lying flat ground, which was originally the base of a tidal lagoon. A 300m wide band of costal dunes separates the landfill from the Poverty Bay coast. The landfill covers an area of approximately 20 Ha and is unlined but fully capped. Leachate is collected in a cut-off drain which surrounds three quarters of the landfill. Disposal of the leachate is by spray irrigation onto the landfill cap with 13,000 - 15,000 m3 of leachate irrigated annually. The site is currently used for grazing sheep.
The overall aim of this study was to improve our understanding of the effect that Paokahu landfill is having on the environment and to determine if the current management practices are sustainable. Specific objectives were to collate and review all the groundwater and leachate monitoring data held by Gisborne District Council to determine if the landfill was affecting the local groundwater and to investigate the effect of leachate irrigation on the landfill cap's soil and vegetation.
The groundwater monitoring data showed the local groundwater was generally affected by salt water intrusions giving the groundwater high anion and cation concentrations. There was no evidence of a leachate plume originating from the landfill and no conclusive evidence of leachate contamination in any of the groundwater monitoring bores.
The leachate had a high electrical conductivity (mean = 9350 Scm-1) and high soluble salts content (mean values, Na = 845 gm-3, K= 496 gm-3, Ca = 240 gm-3, Mg = 127 gm-3, Cl =1346 gm-3). Heavy metals were present in low concentrations and Semi Volatile Organic Compounds were no longer present in the leachate. Cation and anion concentrations were generally higher in the groundwater than in the leachate. The main risk to groundwater quality from leachate contamination was from ammonical nitrogen and nitrate.
The leachate irrigation had caused an increase in soil cation concentrations particularly Na in the landfill cap. However, the soil Exchangeable Sodium Percentage of 1.5 - 2.9, leachate Sodium Adsorption Ratio (6.5) and Electrical Conductivity of (4317 S cm-1) and silty soil material of the landfill cap indicated that soil swelling and dispersion was unlikely to occur in irrigated areas of the landfill cap. Dispersion index testing supported this conclusion with no significant increase in aggregate dispersion under the irrigated areas of the landfill compared to the non-irrigated areas. Soil metal concentrations were low and there was no significant difference in soil heavy metal concentrations between the irrigated and non-irrigated areas of the landfill cap. Leachate Mn concentrations (mean = 1.39 g m-3) were high enough to be potentially toxic to plants, but the soil pH (7.4) and Ca (46.7 me/100g) content mean that Mn toxicity is unlikely to occur. Leachate irrigation appears sustainable under current conditions
Changes in carbon and nitrogen stocks following conversion of plantation forest to dairy pasture on Vitrands (Pumice Soils), New Zealand
No full textBetween 1990 and 2010 some New Zealand plantation forests underwent deforestation to establish dairy farms. The main area of land-use conversion to pasture is to the north of Lake Taupo in the Central North Island (Figures 1 and 2). Pinus radiata (radiata pine) plantations were established in the late 1920s-early 1930s because the Vitrands (Pumice Soils) predominant in the Central North Island were deficient in Co and other trace elements, causing a fatal stock disease in sheep and cattle known as ‘bush sickness’. Bush sickness was subsequently rectified in the mid-1930s with the regular addition of Co, so pastoral farming became viable. The high price of milk solids has recently led to renewed interest in dairying. Recent studies have shown carbon can accumulate following deforestation and establishment of pasture (Fearnside and Barbosa, 1998; Murty et al. 2002; Hedley et al. 2009). However, more information on the rate of accumulation of carbon after deforestation is needed. Increases in soil carbon can improve physical and chemical soil properties, and is an important store of global carbon
Soil and permafrost distribution, soil characterisation and soil vulnerability to human foot trampling, Wright Valley, Antarctica
No full textSoils and shallow permafrost in Wright Valley, Antarctica were mapped at a scale of 1:50 000 to depict their spatial distribution, and sampled to determine the main drivers for the soil classification.
In the cold desert of Wright Valley the Gelisol order of Soil Taxonomy was used to classify the soils. Soils on younger surfaces, associated with Lower Wright Glacier, Upper Wright Glacier and alpine glaciers, contain massive ice within 100 cm of the soil surface and are classified as Glacic Haplorthels or Glacic Haploturbels where there is field evidence of cryoturbation. As a generalization, at either end of the valley, soil moisture recharge from moist coastal air masses (eastern end) and blowing snow drifts maintain the depth to permafrost in which ice-cement occurs at 70 cm, are classified as Salic or Typic Anhyorthels or, where there is field evidence of cryoturbation, Anhyturbels.
While mapping soils in Wright Valley, the distribution and nature of the shallow permafrost were also investigated. Three classes of permafrost were established to coincide with definitions or conditions within Soil Taxonomy viz: permafrost with ice-cement at 70 cm, and massive ice.
A definition for a petrosalic horizon is proposed based on the properties of a salic horizon and the indurated nature of petrocalcic/petrogypsic horizons. The horizon is likely to occur only in the cold desert climate zones of Antarctica.
A rapid method to determine soil vulnerability to human foot traffic was developed. As vulnerability is the product of disturbance and rehabilitation, the method is based on the disturbance of 10 foot prints at a site multiplied by a soil rehabilitation factor based on the soil weathering stage. Although fine-grained aeolian sands are easily disturbed they also rehabilitate rapidly in the windy conditions of Wright Valley. In contrast, old stable soils have a tight cobbly desert pavement with reddish desert varnish and often show less foot print disturbance. When cobbles are overturned, however, fresh rock with thick salt accumulations and without desert varnish is exposed. It takes much time for the desert varnish to re-establish.
The spatial distribution of Soil Taxonomy soil classes, nature of the permafrost and soil vulnerability to human traffic are presented as three separate maps at 1:50 000 scale and as live GIS files
Impacts of conversion from forestry to pasture on soil physical properties of Vitrands (Pumice Soils) in central North Island, New Zealand
No full textTens of thousands of hectares of land have been converted from plantation forest to pasture in the central North Island of New Zealand between 2000 and 2010. The land use change was driven by the perceived better long term returns from dairy farming compared with forestry. Pumice Soils (NZ Soil Classification, equivalent to Vitrands in Soil Taxonomy) in the central North Island are formed on pumice deposited mainly from the AD 232 ± 5 Taupo volcanic eruption. The texture of Pumice Soils (Figure 1) varies from silt to coarse gravel and they have weak structure and erode easily when disturbed. Water holding capacity may be low but increases as the organic matter content of the topsoil is built up
Human,climatic and oceanographic influences on the marine environment of Pohnpei, Federated States of Micronesia
No full textFile PB200200 could not be included in folder EFR1. Full data available on disc with print copy held at the University of Waikato Library.Coral reefs and marine resources are culturally, as well as economically, vital to Pohnpei, situated in the Federated States of Micronesia (FSM). Farming and fishing are the main sources of livelihood for most Pohnpeian communities. Pohnpei has eleven Marine Protected Areas (MPAs) where nine are situated in the Pohnpei Island Lagoon and two MPAs on the outer low-lying atolls. Like many other Pacific Island countries Pohnpei is on the verge of creating more MPAs. However, the marine environment continues to be significantly threatened by human and natural influences. The recognised threats are yet to be methodically investigated.
This thesis used a combination of sediment, coral, fish, climatic, and oceanographic data, and focused on the Pohnpei Lagoon, examining a range of natural and human issues in the marine environment both at the local level (focusing on that within the Pohnpei Lagoon) and regional level (focusing on the western Pacific region).
Evidence from historical, archaeological, and modern experience has influenced various marine impacts that have altered the coastline and the marine environment of the Pohnpei Lagoon. Humans have greatly impacted on the coral diversity and fish populations in the Pohnpei Lagoon by over-fishing and contributing to accelerated sediment inputs. My study findings shows that that increased sea surface temperature (SST) caused by El Ni o events is not the only cause of coral bleaching, but also cooling of SST, and other human factors. However, when corals bleach they recover by symbiont shuffling . This is an ingenious way in which corals host one or more varieties of their zooxanthelle (Symbiodinium symbiont clades) that are more tolerant of the stress caused by increased SST and human factors.
The recognised natural climatic variability, particularly the El Ni o/Southern Oscillation (ENSO), may pose a significant threat to the Pohnpei Lagoon. El Ni o events are associated with: a change in trade winds and stronger wind gusts attributed to typhoons; lower rainfall causing drought; a decrease in SST attributed to cooling of the marine environment; increase of salinity in marine estuaries affecting development and recruitment of marine species communities; and a steep fall in sea level exposing corals to other elements. The various on-going human threats and El Ni o-like conditions have caused giant clams (Tridacna gigas) to become extinct, have endangered herbivorous fish populations, and caused coral bleaching by cooling of SST.
Although high SSTs are normally blamed for coral bleaching, the last major bleaching event in Pohnpei (2002) was likely to be due to a reduction in salinity (freshwater runoff and lower sea level), and there has been strong recovery. However, decreasing water temperatures rather than increases of SSTs may contribute to coral bleaching in the Pohnpei Lagoon and the Micronesian region. The Micronesian region appears to have suffered relatively few episodes of regional coral bleaching events. This is due to the Western Pacific Warm Pool (WPWP) where sea surface temperatures exceed 29 C but also where various feedback mechanisms limit the maximum SSTs.
The management aims of Pohnpei's MPAs are to move forward, while still respecting traditional practices. However, a lack of scientific monitoring, technical support and funding restricts our understanding of human and natural influences on the existing MPAs and the Pohnpei Lagoon. With respect to our policy makers the findings of the present research have implications on the future work in Pohnpei's marine environment and for policy makers, to make more-informed decisions before establishing new MPAs.
My key recommendations were: 1.) Integrate coral and fish monitoring during and after El Ni o events to understand El Ni o effects on the Pohnpei environment. 2.) Undertake herbivorous fish investigation into their populations inside and outside the MPAs. 3.) Do not cut down vegetation along coastline areas, as it prevents erosion 4.) Investigate Symbiodinium coral clades in Pohnpei Lagoon and the outer low-lying atolls
Visual recovery of desert pavement surfaces following impacts from vehicle and foot traffic in the Ross Sea region of Antarctica
No full textSites of past human activity were investigated to assess the visual recovery of the desert pavement following impacts from human trampling and vehicle traffic. Visually disturbed and nearby control sites were assessed using comparative photographic records, a field-based Visual Site Assessment, and Desert Pavement Recovery Assessment. Sites included: vehicle and walking tracks at Marble Point and Taylor Valley; a campsite, experimental treading trial site, and vehicle tracks in Wright Valley; and vehicle and walking tracks at Cape Roberts. The time since last disturbance ranged from three months to over 50 years. This investigation also attempted to determine what has the greatest lasting visual impact on soil surfaces in the Ross Sea region: dispersed trafficking or track formation? Walking tracks remained visible in the landscape (due to larger clasts concentrating along track margins) long after the desert pavement surface had recovered. However, randomly dispersed footprints were undetectable within five years. For many sites, allowing widespread trampling will give lower medium-term visible impact than concentrating traffic flow by track formation. For steep slopes and sites where repeated visits occur, use of a single track is recommended. Some 1950s vehicle tracks remain visible in the Antarctic landscape, but where visually obvious impacts were remediated, evidence of former occupation was almost undetectable
Nitrogen leaching from effluent irrigated pasture
No full textThe surface waters of the Taupo region are of high quality and are sensitive to inputs of nitrogen. To reduce the amount of nitrogen discharged to surface water, the Taupo District Council (TDC) has employed a land treatment scheme (LTS), where treated municipal wastewater is irrigated onto ryegrass pasture. To limit the possibility of nitrogen pollution, regulations govern the amount of effluent that TDC may irrigate. This study reports the results from the first year of a five year trial where nitrogen leaching from the Taupo LTS was measured.
To measure nitrogen leaching from the Taupo LTS, 48 intact monolith lysimeters were installed beneath effluent irrigation from two centre pivot irrigators. Four treatments based on nitrogen loading rates were trialled, nominally no-N (0 kg N ha-¹yr-¹), low-N (350 kg N ha-¹yr-¹ or less), mid-N (between 350 and 450 kg N ha-¹yr-¹), and high-N (greater than 450 kg N ha-¹yr-¹). Leachate was collected at least monthly and analysed for total nitrogen (TN), nitrate/nitrite nitrogen (NO₃-N), ammoniacal nitrogen (NH₄-N), dissolved organic nitrogen (DON), and total Kjeldahl nitrogen (TKN). The pasture was removed from the lysimeters to determine dry-matter production and pasture nitrogen concentration to calculate nitrogen uptake.
Effluent irrigation significantly increased pasture growth and nitrogen leaching compared to the un-irrigated treatments (P<0.001). The mean rate of pasture growth from the irrigated treatments was 15,800 ± 1,700 kg DM ha-¹yr-¹, but there were no significant difference between the rate of pasture growth between the irrigated treatments. The pasture of the high-N treatments had a significantly higher nitrogen concentration than the low-N treatments (P<0.001), consequently the high-N treatment removed 390 kg N ha-¹, compared to 310 kg N ha-¹ removed from the mid-N and low-N treatments. On average, the pasture removed 84 % of the nitrogen that was irrigated.
After 12 months, the no-N treatments leached 5 ± 3 kg TN ha-¹, the low-N treatment leached 15 ± 1 kg TN ha-¹, the mid-N treatment leached 17 ± 8 kg TN ha-¹, and the high-N treatment leached 26 ± 4 kg TN ha-¹. The high-N treatments leached significantly more TN than the low-N (P<0.005), but there was no significant difference in TN leached between the high-N and mid-N, or the mid-N and low-N treatments. The TN leached was poorly correlated with the rate of effluent irrigation. TN leached was positively correlated with the volume of water that drained through the soil (R2=0.7). The nitrogen in the leachate of the irrigated treatments comprised on average, 53 % NO₃-N, and 45 % DON, while the leachate of the un-irrigated treatments comprised, on average, 26 % NO₃-N and 72 % DON. NH₄-N accounted for approximately 2% of all nitrogen leached. Most of the NO₃-N leached throughout the year was leached after rain during summer and autumn. The mean concentration of NO₃-N leached from the irrigated treatments was 1.3 g N m-³. The concentration of NO₃-N in the leachate never exceeded Ministry of Health guidelines (11.3 g N m-³). The mean concentration of DON leached from the irrigated treatments was 1.2 g N m-³.
Removing nitrogen in the pasture is the solution to avoid excess nitrogen leaching from the Taupo LTS. There is potential to recover more nitrogen in the pasture by improving the pasture cover and frequency of harvest
Evaluation of land in Wairoa District for potential horticultural development
No full textThe Wairoa District, on the East Coast of the North Island of New Zealand has less horticultural development than areas to the north and south. The objective of this study was to provide information to help inform landowners who may wish to invest in horticulture which could improve the economic situation of the district.
Field work involving local scale climate mapping and soil characterisation of areas with potential for horticulture in Wairoa District was completed in 2017. Constructed climate and topographical maps with existing soil maps were evaluated against known crop growth requirements to produce crop potential maps identifying areas with potential for crop production. Horticultural crops included in this study include kiwifruit, apples, cherries. Alternative crops include hemp and poppies.
Between mid-April – 31 October 2017, 45 portable iButton temperature loggers were deployed throughout Land Use Capability classes 1-3 in the Wairoa District and were set to record hourly temperature. When regressed against nearby climate stations, long term (18 -26 years) temperature datasets were derived from the short term iButton datasets. MODIS satellite images were also analysed to help identify areas prone to frost. From the long-term datasets local scale chill hour, growing degree days and October frost risk maps were constructed for the Wairoa District. For the central area from Wairoa to Frasertown, chill hours were estimated to range between 600 – 900, growing degree days 1300 – 1400 and October frost risk less than 25%.
From four representative soil types, horizon samples were taken to determine the soils physical properties including each horizons Total Available Water Holding Capacity (TAWHC). Horizon TAWHC for each soil type were summed to give TAWHC to 1 meter which along with 21 years of estimated daily rainfall and potential evapotranspiration were used in a soil water balance model to estimate seasonal crop irrigation requirements. Irrigation estimates for kiwifruit compared well against published values ranging between mean 204 – 247 mm.
The crop potential maps with seasonal crop irrigation estimates can enhance a land owner’s ability to make informed decisions resulting in economic benefit to whanau, community and the Wairoa District
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