Seasonal Changes In Water Content Research Articles

Quantifying the contribution of matric suction on changes in stability and displacement rate of a translational landslide in glaciolacustrine clay

A study of factors impacting landslide displacement rates was conducted on the Ripley Landslide within the Thompson River valley in British Columbia, Canada for the International Programme on Landslides’ project #202. Seasonal and multiyear changes in atmospheric factors cause cyclic fluctuation of matric suction in the vadose zone through changes to the in situ water content. The ingress of moisture is shown to contribute to multiyear and seasonal loss of stability causing increasing landslide displacement rates, often disregarded in slope stability calculations. However, the water content in the unsaturated zone is important, especially in semi-arid to arid climates where the water table is low and large portions of the slope are unsaturated. Additional tools for studying long-term variations in climate and seasonal changes in water content are presented. These tools are used to characterize historical climate and compare several factors that have resulted in changing landslide displacement rates and magnitude. Infiltration of precipitation and snowmelt directly contributes to matric suction loss in the head scarp and is exacerbated by the presence of tension cracks. While groundwater levels are often correlated to changing displacement rates, changes in matric suction can also influence the rates of displacement. Climatic trends over subsequent years alter the long-term soil water accumulation which impacts rates of landslide displacement. By accounting for additional strength, or potentially a loss in strength due to increasing water content, it is possible to develop a more complete understanding of the mechanisms of climate change which drive displacement rates in the translational, metastable earthen slides that dominate the Thompson River valley. These mechanisms can be applied to comparable river valleys around the world.

De-coupling seasonal changes in water content and dry matter to predict live conifer foliar moisture content

Live foliar moisture content (LFMC) significantly influences wildland fire behaviour. However, characterising variations in LFMC is difficult because both foliar mass and dry mass can change throughout the season. Here we quantify the seasonal changes in both plant water status and dry matter partitioning. We collected new and old foliar samples from Pinus contorta for two growing seasons and quantified their LFMC, relative water content (RWC) and dry matter chemistry. LFMC quantifies the amount of water per unit fuel dry weight whereas RWC quantifies the amount of water in the fuel relative to how much water the fuel can hold at saturation. RWC is generally a better indicator of water stress than is LFMC. We separated water mass from dry mass for each sample and we attempted to best explain the seasonal variations in each using our measured physiochemical variables. We found that RWC explained 59% of variation in foliar water mass. Additionally, foliar starch, sugar and crude fat content explained 87% of the variation in seasonal dry mass changes. These two models combined explained 85% of the seasonal variations in LFMC. These results demonstrate that changes to dry matter exert a stronger control on seasonal LFMC dynamics than actual changes in water content, and they challenge the assumption that LFMC variations are strongly related to water stress. This methodology could be applied across a range of plant functional types to better understand the factors that drive seasonal changes in LFMC and live fuel flammability.

Seasonal changes in needle water content and needle ABA concentration of Japanese red pine, Pinus densiflora, in declining forests on Mt. Gokurakuji, Hiroshima prefecture, Japan

To evaluate the effects of air pollution on the decline of Pinus densiflora forests, various research has been conducted around Mt. Gokurakuji (34 degrees 23'N, 132 degrees 19'E, 693 m a.s.l.) north of the Seto Inland Sea, west Japan. To investigate the mechanisms responsible for decreases in photosynthesis (Pn) and stomatal conductance (gl), delta13C of needles and seasonal changes in the water content (WC) and abscisic acid concentration (ABA) of needles were measured in various stands. The delta13C values were less negative in declining stands and younger needles. ABA and WC were not correlated with each other. WC decreased consistently with needle age while the ABA showed a minimum in August and a smaller content in older needles. Monthly precipitation and the daily maximum vapor pressure were not correlated with ABA and WC. In declining stands, WC and ABA tended to be higher and lower, respectively, than in nondeclining stands. These results suggest that the trees in declining stands received less water stress than those in nondeclining stands and the differences in gl and delta13C are not caused by the difference in water stress. The possibilities of the effects of air pollution and the infection of pine-wood nematode on the physiological decline on the pine needles are discussed.

Seasonal Changes in Water Content of Subsoil Beneath Old Slab-on-ground Structures in Finland

The objective of this study is to determine the normal level of water content of the subsoil beneath old slab-on-ground structures and discuss the impact of the thermal and moisture conditions. According to measurements, the water content of subsoil beneath a slab-on-ground structure equals or exceeds the hygroscopic equilibrium moisture content of the material in RH 100%. The high water vapor content with warm subsoil temperature can cause moisture damages to the floor covering. In fine-grained soils where capillary action is possible often some excess capillary water is detected at the samples. The amount of capillary bound water and risk for damage is dependent on distance from the ground water table.

防火的視点からみた各種樹葉の含水率に関する研究

There were some differences in the results of existing measurements on water content ratio of leaves. Therefore, the ratios of water content in 55 species of leaves were measured under the same conditions when leaf samples were taken. The result of measurement showed that there are differences in the water content between species and leaves. Next, seasonal changes in water content of leaves from 29 evergreen species were compared during summer and winter. As the result this comparison, it was found that the water content of leaves in Tokyo area is highest in summer. In addition to this, results of measurements assessing annual changes in water content of leaves from 6 broadleaf tree species indicated that the water content ratio in evergreen broad-leaved trees was at a minimum before coming into leaf during the winter and spring seasons. After showing the highest ratio of the season just after leaf flush, the ratio began gradually decreasing until the winter season. For deciduous broad-leaved trees, their ratio of water content has a tendency to be highest in April and drops temporarily in midsummer. Moreover, the results in this research and the results of existing measurements were integrated, the water content ratios of 178 species of trees were arranged and the tendency was grasped.

Model comparison of flow through a municipal solid waste incinerator ash landfill

The drainage discharge of a municipal solid waste incinerator (MSWI) bottom ash landfill was simulated using various modelling approaches. Two functional models including a neural networks approach and a hydrological linear storage model, and two mechanistic models requiring physical/hydrodynamic properties of the waste material, HYDRUS5 and MACRO (Version 4.0) were used. The models were calibrated using an 8-month data set from 1996 and validated on a 3-month data set from winter 1994/1995. The data sets comprised hourly values of rainfall, evaporation (estimated from the Penman–Monteith relationship), drainage discharge and electrical conductivity. Predicted and measured discharges were compared. The discharge predicted by the functional models more exactly followed the discharge patterns of the measured data but, particularly the linear storage model, could not cope with the non-linearity of the system that was caused by seasonal changes in water content of the MSWI bottom ash. The fit of the neural networks model to the data improved with increasing prior information but was less smooth than the measured data. The mechanistic model that included preferential discharge, MACRO, better modelled the discharge characteristics when inversely applied, indicating that preferential flow does occur in this system. However, even the inverse application of HYDRUS5 could not describe the system discharge as well as the linear storage model. All model approaches would have benefited from a more exact knowledge of initial water content.

Water relations of the freeze-tolerant New Zealand alpine cockroach Celatoblatta quinquemaculata (Dictyoptera: Blattidae)

Celatoblatta quinquemaculata is a freeze-tolerant alpine cockroach found on the Rock and Pillar Range, Central Otago, New Zealand. This study investigated seasonal changes in water content, as well as desiccation tolerance, and the relationship between desiccation and cold tolerance. Whole body water contents from field-fresh cockroaches collected over a 20 month period ranged from 69.9±1.0% fresh weight (FW) in February 1998 to 60.3±1.1% FW in July 1998. Water contents were significantly lower in winter than summer, and were positively correlated to microhabitat temperatures over the week preceding collection. Cockroaches survived the loss of up to 82% (mean: 56.7%±10.2) of their initial body water content, and the amount of water loss sustained was not dependent on the rate of water loss. Cockroaches did not suffer further mortality due to desiccation after removal to 99% relative humidity, but only regained lost water if given access to liquid water. Experimental dehydration did not enhance freeze-tolerance, but did slightly lower the supercooling point. It is concluded that reduction of body water content in winter may be a consequence of cold hardening responses, but desiccation does not constitute the cold hardening mechanism itself.

Field leaching and degradation of atrazine in a gradationally textured alkaline soil

The leaching and degradation of atrazine to 40 cm was monitored over a 1-year period, following a spray application in May 1991, at a field site on a highly alkaline sandy loam cropping soil with a soil pH ≥8·5. To account for gradational changes in soil texture and pH with depth, separate dose response curves of an oat bioassay for each 10-cm soil-sampling interval were used, to quantify the soil concentrations of the herbicide. Throughout the trial the movement of atrazine was not observed to exceed beyond 40 cm with total rainfall of 386 mm. The only significant leaching of the herbicide was detected in late winter 1991, when approximately 30·5% of the applied amount leached from the 0–10 cm to 10–20 cm soil layer, with trace amounts detected at greater depths. This leaching occurred during a period of rainfall of 50 mm when soil water contents in the 0–10 cm to 10–20 cm soil layers were at an optimum, and it was deduced that the extent of the leaching, when evaluated with other studies, was influenced by the pH of the soil. Atrazine recovery decreased exponentially with sampling time. The data fitted a first-order exponential function (R2 = 0·99), with a half-life time for degradation of 62 days. The good fit of the data to this function also indicated that the rate of degradation was apparently independent of seasonal changes in water content and soil temperature. From this, it was inferred that any lowering to the rate of degradation, owing to decreasing soil water contents in spring–summer, was offset with compensating rises in soil temperature. Edaphic conditions in this spring–summer period approximate those in other studies where chemical hydrolysis was an important process of breakdown of atrazine. The degradation of the herbicide was almost complete by the end of the trial in late May 1992. An applied amount of 2·7% remained in the 10–20 cm soil layer, which corresponded to a residue level of 0·02 µg atrazine/g soil. This residue level is well below the recorded phytotoxic threshold of select cultivars of wheat, barley, and lucerne.

Troubled waters: Environmental applications of electrical and electromagnetic methods

The relatively new subdiscipline of environmental geophysics has grown enormously in the last five years. The size and diversity of the field, and the associated literature, is such that it is extremely difficult to keep up with even a small portion of the field. Electrical and electromagnetic (E & EM) methods, including ground penetrating radar and time-domain reflectometry, play a central role in environmental geophysics. One reason for the utility of E & EM methods in groundwater studies is the similarity in the way that current flow and fluid flow depend on the connectivity and geometry of the pores in soils and rocks. Another reason is the influence of the pore water quality on the geophysical response. More than any other geophysical technique, E & EM methods are directly affected by the presence of conductive pore fluids in the subsurface, such as leachates from landfill sites and sea water invading a coastal groundwater supply that has been placed under stress because of population expansion. The chloride ion is one of the most electrically active of the naturally-occurring ions, and allows us to detect sea water incursion; leachates from landfill sites contain the by-products of organic decay, such as acetic acid, which are generally less conductive than chloride, but nonetheless enhance the pore water and formation electrical conductivities. Landfill leachate plumes are thus easily mapped. The shallow subsurface electrical and dielectric properties exhibit hysteresis due to seasonal changes in water content; the physical properties will be different for the same degree of saturation, depending on whether the water level is rising or falling. Topographic effects are also important; an empirical correction method works well to remove a background trend in the conductivity due to changes in elevation. Heterogeneity and anisotropy of the electric properties may be related to similar effects in the hydraulic properties. New technology and the adaptation of existing technology has lead to the development of fresh instruments, such as electrode arrays towed across the ground, resistivity logging while drilling, fast-rise time TEM, NMR combined with TEM, electric quadripole, et cetera. The applications of E & EM methods cover a wide range of geographic areas and groundwater problems, but have had particularly wide use for groundwater exploration in arid and semi-arid regions, for mapping and monitoring salt-water incursion in susceptible aquifers, and for mapping and monitoring contaminants.

Seasonal field analyses of water and fat content in the long‐lived millipede Polyzonium germanicum (Diplopoda, Polyzoniidae)

Two hundred and seventy‐nine Polyzonium germanicum individuals of various stadia were collected seasonally in winter, late spring‐early summer (the breeding period) and early autumn. Fresh weight, dry weight and defatted dry weight were determined for each specimen. Seasonal changes in water content and fat content, expressed as percentages of defatted dry weight, were analysed in relation to body size and sex. Changes in water content were more pronounced in the smallest individuals (juveniles), whereas changes in fat content were more pronounced in the largest (adults). Seasonal fluctuations in water and fat content were similar in both sexes despite the sexual dimorphism of body weight. The results suggest the following relationships within the species life‐cycle: (i) water content increases during the warm months (up to 295% for juveniles in early autumn), which coincides with the moulting period, (ii) Fat content increases subsequently to moulting; overall maxima are reached in early autumn (population mean = 62–5%), as well as in early summer for the young, (iii) Both water and fat content decrease (to about 150% and 50%, respectively) in winter; however, there is no evidence of starvation–at least in ovigerous females which increase in dry weight during that season, (iv) Fat content strongly decreases (below 30% in the largest specimens) in adults of both sexes during the breeding period.

Seasonal changes in fat and water content in field populations of olive psylla Euphyllura olivina Costa (Homoptera Psyllidae)

The seasonal changes in water content and fat content of olive psylla, Euphyllura olivina in the field were investigated in two successive years. The overwintering adults of olive psylla had more fat than spring and summer generation adults. There was a steady increase in % fat contents of females from mid-October to early January. The % fat of both sexes decreased sharply in May, June and July. There was a gradual reduction in % water content from mid-June to early October and then decreased steadily until early November. The % water in the overwintering adults ranged from 57.5 to 45% and became constant around 52.5% of live body weight in February and March. Seasonal changes in % water was positively related to population changes of olive psylla. The % water in olive psylla was negatively related to the fat content.

Relationship of Air Temperature to Water Content and Supercooling of Overwintering Peach Flower Buds

Abstract In overwintering flower buds of ‘Redhaven’ peach [Prunus persica (L) Batsch], seasonal changes in the supercooling point were correlated significantly with seasonal changes in water content of the whole flower bud and its parts, the flower primordium within the flower bud and the vascular traces just below the flower primordium. Both the supercooling point and the water content of the whole flower bud and its parts were correlated significantly with the 2- and 5-day mean air temperature preceding collection. Controlled-temperature studies with ‘Siberian C’ and ‘Redhaven’ revealed that the water content of the flower primordium and vascular traces and not that of the whole flower bud was critical to the level of supercooling attained. Supercooling of the flower primordium appeared to be related directly to its water content. Water content of the vascular trace appeared to be important during the initial stages of freezing for preventing spread of the ice boundary into supercooled regions of the flower primordium. Water content of the 2 critical tissues appeared to be determined by migration from and to these tissues during freezing and thawing. During freezing, water was lost from the flower primordium and vascular traces by migration to the flower bud scales which appeared to act as an ice sink. After prolonged exposure to freezing outdoors, water was also lost to the exterior of the flower bud. After thawing, the flower primordium and vascular traces regained water content by transfer from the ice sinks within the flower bud and sources external to the flower bud. Loss of flower bud hardiness occurred during storage at 0°C for 10 days, which was not due to change in water content of the flower bud or its parts. The excised flower buds of the hardier ‘Siberian C’ supercooled to a lower temperature than excised flower buds of the less hardy ‘Redhaven’ at equivalent water content.