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We analyze temporal variations in the travel times of both P and S waves (Vp and Vs) for 14 months at Toyohashi (central Japan) with a continuously operating vibration source that could efficiently produce both P and S waves. Seismic waves produced by the source, which is called the accurately controlled routinely operated signal system (ACROSS), are recorded by three nearby seismic stations, and the travel time variation at each station is estimated using the transfer function calculated from the recorded data. Long-term variations in Vp and Vs are observed and can be interpreted by the change in fluid saturation and crack density of the subsurface rocks. The variation in fluid saturation and crack density are consistent with that in the groundwater level, which is measured at the station nearest to the ACROSS. Short-term responses to rainfalls are observed at the station nearest to the ACROSS system; the interpretation of the changes in crack density and saturation is inconsistent with the ground water observation, partly owing to the initial response to rainfall. This can be interpreted as an air–water mixture within pores or cracks on a fine scale. [ABSTRACT FROM AUTHOR]

In drained forest sites, ditch cleaning (DC) may be needed to restore the drainage function of ditches and maintain favourable growing conditions. The main aims of this study were (i) to estimate the growth responses of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst) stands following DC, and (ii) to test the hypothesis that stand stocking should be less than 150 m3 ha−1 at DC to obtain a growth response. This survey included 14 ditched stands in Sweden on both mineral and peat soils. The methodology was based on evaluating growth rates before and after the DC operation (growth ratio), reconstructing the growth by taking increment cores from the tree trunks. The measured growth was related to growth derived using a growth simulator as if DC had not been conducted. The results showed an average growth increase of 1.6 m3 ha−1 yr−1 for about 25 years after DC in the stands containing 50–200 m3 ha−1. The growth response appeared to be positively related to stand age, trees ha−1 and site index, and negatively related to stand volume, supporting the hypothesis that stand stocking is an important factor to consider when assessing the need for DC. [ABSTRACT FROM AUTHOR]

Persistent agricultural irrigation makes loess terrace prone to landslide hazards. Therefore， it is necessary to identify and monitor the potential landslides with effective ways. In this paper，the time series interferometric synthetic aperture radar (InSAR) analysis technique is utilized to analyze both descending and ascending Sentinel-1 data stacks covering the period from January 2016 to August 2018. Active slopes on the Heifangtai terrace and surrounding area in northwest China are identified. Comparison between time series InSAR measurements and GPS measurements is carried out. Time series displacement analysis reveals that agricultural irrigation poses a great threat to the stability of slopes at the terrace edge. Meanwhile，temperature variation related displacements are also identified on bridges across the Yellow River with high correlation. Our study confirms the effectiveness of time series InSAR method, which can play a significant role in the identification and prevention of loess landslides. [ABSTRACT FROM AUTHOR]

Intensive irrigation causes major consumption of ground water resources especially in India. Due to a large population base, the extraction of ground water for mechanized agriculture has significantly increased during the last few decades in the Bist Doab region of Punjab, India. This study analyses the spatial pattern of changes in ground water levels in the Bist Doab region during the 1998–2011 period. Using spatial interpolation, the ground water levels were interpolated for the whole region for each year. Spatial data on the intensity of irrigation and tubewell density were also mapped to analyse their trends. The results reveal the emergence of a zone of deepening water table in the south west portion of the Bist Doab. The ground water levels have dropped more than 20 meters from the surface in this area. Using these results, we classified the Bist Doab region into three zones (Zone 1, 2, and 3) for prioritizing ground water management initiatives. While agricultural water consumption provides one possible explanation for falling ground water levels in the area, other non‐anthropogenic factors may also play a role in such trends. Further research at the same scale is recommended in other parts of the Punjab State. [ABSTRACT FROM AUTHOR]

Field investigations and indoor experiment were carried out to clarify the effect of temperature and chlorophyll a concentration of the sediment, photon flux density, and ground water level on the absorption and emission of CO 2 from the surface sediment of the artificial salt marsh. The flux of CO 2 absorption was closely related to sediment temperature, chlorophyll a and photon flux density. On the other hand, flux of CO 2 emission changed depending on the sediment temperature and ground water level. The ground water level was thought to be indispensable for estimating CO 2 emission from the sediment of the intertidal zone of the salt marsh. Using equations of CO 2 flux with sediment temperature, chlorophyll a, photon flux density and ground water level, the total CO 2 absorption and emission of the artificial north salt marsh of Osaka Nanko bird sanctuary was estimated as ca. 23 tons (4.3 g CO 2 m −2 day −1 ) for absorption and ca.14 tons (2.6 g CO 2 m −2 day −1 ) for emission in May to September 2014. These results suggest that a net of 9 tons of CO 2 (1.7 g CO 2 m −2 day −1 ) was absorbed, and that this salt marsh performs the function of a CO 2 sink in high temperature seasons. [ABSTRACT FROM AUTHOR]

Most studies on riverine ground beetle assemblages last 1–2 years, and studies on carabids from lowland stream ecosystems are rare. In 1999, a 16-year study was launched to gain insight into the structure and diversity of carabid assemblages in a cross-section of four habitats located beside a 5 m wide stream: Meadow (wet meadow), Clumps (meadow scattered with birch and willow clumps farther from the river), Birch (birch stand), and Pine (pine stand located the farthest from the stream). The total number of 14, 216 individuals representing 118 carabid species were collected. Eleven functional carabid groups have been analysed. Principal response curve analysis showed significant differences existing during the whole study period among carabid assemblages from the four habitats. Generalised Linear Mixed Models analysis revealed a dependence of Chao2 estimator performance on temperature and ground water level, whereas life traits of carabids depended solely on the latter factor, affecting species composition (i.e., proportions of autumn and spring breeders, large and small zoophages, hemizoophages, forest, generalists and open area species, wingless species, hygrophilous, mesophilous and xerophilous species). The lower the ground water level, the higher was the proportion of late-successional species. Both Chao2 value and the proportion of late-successional species were growing with the increasing distance from the stream, peaking in the Pine habitat. Early-successional fauna dominated in streamside assemblages. IndVal analysis identified 1–9 characteristic species for each habitat type, mostly non-recurrent during the study period. Thus, species composition of riverine carabid assemblages should be studied for longer periods than 1–2 years to avoid accidental observations. [ABSTRACT FROM PUBLISHER]

The 21st century projections of ground water level and hydrothermal conditions in Lithuanian peatbog ecosystems. Geologija. Geografija. 2016. T. 2(3). ISSN 2351-7549. Peatlands play a very important role in the carbon sequestration process. However, human activity and ongoing global environmental change shifted peatlands from carbon sinks to source because warmer climates could accelerate the rate of production of carbon dioxide and methane from soils. The peatland ecosystems are very complex, but ground water level (GWL) and hydrothermal conditions (precipitation and evaporation) fluctuations are major drivers determining the state of the ecosystem. This research focuses on four peatbogs situated in different parts of Lithuanian: Aukšumala, Čepkeliai, Kerėplis, and Rėkyva. The future GWL tendencies are based on the relation to precipitation amount. Also, difference between precipitation and evaporation (P-E) was projected in near- (2016-2035) and long- (2081-2100) term future using four RCPs. The results revealed that the major changes in peatland ecosystems (for peat accumulation) covering the entire Lithuanian territory are predicted at the end of the 21st century. The most drastic changes in the peatlands will be related to major shifts in climate system (RCP8.5 scenario). Moreover, the major GWL and hydrothermal conditions changes are expected in the peatlands situated in the western part of Lithuania. [ABSTRACT FROM AUTHOR]

Peatlands play a very important role in the carbon sequestration process. However, human activity and ongoing global environmental change shifted peatlands from carbon sinks to source because warmer climates could accelerate the rate of production of carbon dioxide and methane from soils. The peatland ecosystems are very complex, but ground water level (GWL) and hydrothermal conditions (precipitation and evaporation) fluctuations are major drivers determining the state of the ecosystem. This research focuses on four peatbogs situated in different parts of Lithuanian: Aukšumala, Čepkeliai, Kerėplis, and Rėkyva. The future GWL tendencies are based on the relation to precipitation amount. Also, difference between precipitation and evaporation (P-E) was projected in near- (2016–2035) and long- (2081–2100) term future using four RCPs. The results revealed that the major changes in peatland ecosystems (for peat accumulation) covering the entire Lithuanian territory are predicted at the end of the 21st century. The most drastic changes in the peatlands will be related to major shifts in climate system (RCP8.5 scenario). Moreover, the major GWL and hydrothermal conditions changes are expected in the peatlands situated in the western part of Lithuania. [ABSTRACT FROM AUTHOR]

Abstract: This study examines the water level influence on the seismic response of sand deposits. The seismic ground response of a sand deposit for two cases was computed: groundwater level near the surface and at great depth. The ratio of soil factors computed for both cases evaluates the influence of having the water table near the surface. This parameter is small when the full range of periods is considered, but rises to ∼1.15 when narrowing the range of periods to 0.2–0.6s, corresponding to the plateau of Eurocode 8 ground type C response spectrum. So, the water level effect is of the same magnitude of the existing soil factor in seismic codes. [Copyright &y& Elsevier]

In this paper, the long-term consecutive differential interferometric synthetic aperture radar (SAR) technique is used to measure the volume change during land deformation. This technique was used to investigate the subsidence of Bandung city, Indonesia, by assessing the data from two Japanese L-band spaceborne SARs (Japanese Earth Resources Satellite 1 SAR and Advanced Land Observation Satellite Phased Array type L-band Synthetic Aperture Radar) during the periods of 1993-1997 and 2007-2010. The results are confirmed using GPS observation data, ground survey data, local statistics, ground water level trend data, and the geological formation of the study area. The obtained results reveal a close correlation between the subsidence measurements and changes in the ground water level due to water pumping, population growth, industry growth, and urbanization of the study area. [ABSTRACT FROM AUTHOR]

The study examined the effect of variation in hydrology on seedling recruitment of shrubs, trees and herbs in peat bogs. The establishment of plants and hydrologic conditions were followed in two peatlands in the Polesie Zachodnie region, Eastern Poland. Meteorological conditions in the study sites ranged from very dry (2006) to very wet (2007) and strongly affected ground water level in the bogs. The emergence of woody species typical for advanced vegetation succession was higher in forest-bog, while the recruitment of typical peat bog plants was higher in open bog. Disturbance in the vegetation positively influence demergence of typical peat bog species and Betula pubescens, but the effect was only found in the dry year. Only in Pinus sylvestris did recruitment increase in wet seasons. The results suggested that an increase in the number of woody species in peat bogs may be enhanced during relatively wet seasons and that disturbance in the vegetation cover are not required for seedling recruitment of these plants. [ABSTRACT FROM AUTHOR]

As is known in the groundwater regime is influenced by precipitation, surface runoff and evaporation of soil moisture. In the arid climate for crop production in the initial phase of the plant the determining factor is the condition of aeration zone, which is determined by the level of groundwater. And in areas prone to soil salinity, groundwater regime is determined by the state of irrigated lands: the rise of level or increasing salinity pose a risk to soil salinity, soil salinity reduces the productivity of irrigated lands and irrigation water. Along with this assessment of groundwater regime, especially its state level under the influence of precipitation and runoff are difficult scientific problem. The solution of this important agricultural production is the subject of this Article. [ABSTRACT FROM AUTHOR]

The carbon balance of tropical peatlands was investigated using measurements of gaseous fluxes of carbon dioxide (CO2) and methane (CH4) at several land-use types, including nondrained forest (NDF), drained forest (DF), drained regenerating forest (DRF) after clear cutting and agricultural land (AL) in Central Kalimantan, Indonesia. Soil greenhouse gas fluxes depended on land-use, water level (WL), microtopography, temperature and vegetation physiology, among which WL was the strongest driver. All sites were CH4 sources on an annual basis and the emissions were higher in sites providing fresh litter deposition and water logged conditions. Soil CO2 flux increased exponentially with soil temperature ( Ts) even within an amplitude of 4–5°C. In the NDF soil CO2 flux sharply decreased when WLs rose above −0.2 and 0.1 m for hollows and hummocks, respectively. The sharp decrease suggests that the contribution of surface soil respiration (RS) to total soil CO2 flux is large. In the DF soil CO2 flux increased as WL decreased below −0.7 m probably because the fast aerobic decomposition continued in lower peat. Such an increase in CO2 flux at low WLs was also found at the stand level of the DF. Soil CO2 flux showed diurnal variation with a peak in the daytime, which would be caused by the circadian rhythm of root respiration. Among the land-use types, annual soil CO2 flux was the largest in the DRF and the smallest in the AL. Overall, the global warming potential (GWP) of CO2 emissions in these land-use types was much larger than that of CH4 fluxes. [ABSTRACT FROM AUTHOR]

The complexity of natural ecological systems presents challenges for predicting the impact of global environmental changes on ecosystem structure and function. Grouping of plants into functional types, that is, groups of species sharing traits that govern their mechanisms of response to environmental perturbations, reduce the complexity of species diversity to a few key plant types for better understanding of ecosystem responses. Chambers were used to measure CO2 exchange in grass and moss growing together in a mountain peatland in southern Germany to assess variations in their response to environmental changes and how they influence ecosystem CO2 exchange. Parameter fits and comparison for net ecosystem exchange (NEE) in two ecosystem components were conducted using an empirical hyperbolic light response model. Annual green biomass production was 320 and 210 g dwt m −2, whereas mean maximum NEE was –10.0 and –5.0 μmol m −2 s −1 for grass and moss, respectively. Grass exhibited higher light use efficiency (α) and maximum gross primary production [(β+γ)2000]. Leaf area index explained 93% of light use and 83% of overall production by the grass. Peat temperature at 10-cm depth explained more than 80% of the fluctuations in ecosystem respiration ( Reco). Compared to grass, moss NEE was more sensitive to ground water level (GWL) draw-down and hence could be more vulnerable to changes in precipitation that result in GWL decline and may be potentially replaced by grass and other vegetation that are less sensitive. [ABSTRACT FROM AUTHOR]

Water-level changes were observed in 107 wells at 67 monitoring stations in the southern coastal plain of Taiwan during the 2006 Mw 7.1 Hengchun earth quake doublet. Two consecutive coseismic changes induced by the earth quake doublet can be observed from high-frequency data. Observations from multiple-well stations indicate that the magnitude and direction of coseismic change may vary in wells of different depths. Coseismic rises were dominant on the south east side of the costal plain; whereas, coseismic falls prevailed on the north west side. In the transition zone, rises appeared in shallow wells whilst falls were evident in deep wells. As coseismic ground water level changes can reflect the tectonic strain field, tectonic extension likely dominates the deep subsurface in the transition area, and possibly in the en tire southern coastal plain. The coseismic rises in water level showed a tendency to decrease with distance from the hypocenter, but no clear trend was found for the coseismic falls. [ABSTRACT FROM AUTHOR]