scholarly journals In Situ CO2 Efflux from Leaf Litter Layer Showed Large Temporal Variation Induced by Rapid Wetting and Drying Cycle

PLoS ONE ◽  
2014 ◽  
Vol 9 (10) ◽  
pp. e108404 ◽  
Author(s):  
Mioko Ataka ◽  
Yuji Kominami ◽  
Kenichi Yoshimura ◽  
Takafumi Miyama ◽  
Mayuko Jomura ◽  
...  
Keyword(s):  
Temporal Variation ◽  
Leaf Litter ◽  
Co2 Efflux ◽  
Litter Layer ◽  
Wetting And Drying ◽  
Wetting And Drying Cycle

scholarly journals Using Capacitance Sensors for the Continuous Measurement of the Water Content in the Litter Layer of Forest Soil

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Mioko Ataka ◽  
Yuji Kominami ◽  
Takafumi Miyama ◽  
Kenichi Yoshimura ◽  
Mayuko Jomura ◽  
...  
Keyword(s):  
Water Content ◽  
Output Voltage ◽  
Continuous Measurement ◽  
Calibration Line ◽  
Calibration Function ◽  
Litter Layer ◽  
Wetting And Drying ◽  
Study Sites ◽  
Water Holding

Little is known about the wetting and drying processes of the litter layer (Llayer), likely because of technical difficulties inherent in nondestructive water content (WC) monitoring. We developed a method for continuously measuring the WC of leaf litter (the “LWC method”)in situusing capacitance sensors. To test variants of this approach, five (for the LWC_5) or ten (for the LWC_10 method)Quercus serrataleaves were attached around capacitance sensors. The output voltage used for each LWC method was linearly correlated with the gravimetric WC (LWC_5:R2=0.940; LWC_10:R2=0.942), producing different slopes for each calibration line. Forin situcontinuous measurements of WC in theLlayer, two sensors were used, one placed on top of theLlayer and the other at the boundary between theLand mineral layers. The average continuous WC of theLlayer was then calculated from the output voltage of the two sensors and the calibration function, and this value was linearly correlated with the gravimetric WC(R2=0.697). However, because theLlayer characteristics (e.g., thickness, water-holding capacity, and species composition) may differ among study sites, appropriate approaches for measuring this layer’s moisture properties may be needed.

Does repeated wetting and drying accelerate decay of leaf litter?

1988 ◽  
Vol 20 (5) ◽  
pp. 647-656 ◽  
Author(s):  
Barry R. Taylor ◽  
Dennis Parkinso
Keyword(s):  
Leaf Litter ◽  
Wetting And Drying

scholarly journals Removal of Pharmaceuticals and Personal Care Products during Water Recycling: Microbial Community Structure and Effects of Substrate Concentration

2014 ◽  
Vol 80 (8) ◽  
pp. 2440-2450 ◽  
Author(s):  
Kathryn M. Onesios-Barry ◽  
David Berry ◽  
Jody B. Proescher ◽  
I. K. Ashok Sivakumar ◽  
Edward J. Bouwer
Keyword(s):  
Water Treatment ◽  
Microbial Communities ◽  
Personal Care Products ◽  
Treatment Plant ◽  
Soil Aquifer Treatment ◽  
Personal Care ◽  
Wetting And Drying ◽  
Biological Removal ◽  
Close Relatives ◽  
Wetting And Drying Cycle

ABSTRACTMany pharmaceuticals and personal care products (PPCPs) have been shown to be biotransformed in water treatment systems. However, little research exists on the effect of initial PPCP concentration on PPCP biotransformation or on the microbial communities treating impacted water. In this study, biological PPCP removal at various concentrations was assessed using laboratory columns inoculated with wastewater treatment plant effluent. Pyrosequencing was used to examine microbial communities in the columns and in soil from a soil aquifer treatment (SAT; a method of water treatment prior to reuse) site. Laboratory columns were supplied with different concentrations (0.25, 10, 100, or 1,000 μg liter−1) of each of 15 PPCPs. Five PPCPs (4-isopropyl-3-methylphenol [biosol],p-chloro-m-xylenol, gemfibrozil, ketoprofen, and phenytoin) were not removed at any tested concentrations. Two PPCPs (naproxen and triclosan) exhibited removals independent of PPCP concentration. PPCP removal efficiencies were dependent on initial concentrations for biphenylol,p-chloro-m-cresol, chlorophene, diclofenac, 5-fluorouracil, ibuprofen, and valproic acid, showing that PPCP concentration can affect biotransformation. Biofilms from sand samples collected from the 0.25- and 10-μg liter−1PPCP columns were pyrosequenced along with SAT soil samples collected on three consecutive days of a wetting and drying cycle to enable comparison of these two communities exposed to PPCPs. SAT communities were similar to column communities in taxonomy and phylotype composition, and both were found to contain close relatives of known PPCP degraders. The efficiency of biological removal of PPCPs was found to be dependent on the concentration at which the contamination occurs for some, but not all, PPCPs.

Spatial variation in CO2 efflux from the soil in a mature beech forest ecosystem.

2021 ◽  
Author(s):  
Yihan Cai ◽  
Takahiro Nishimura ◽  
Hideyuki Ida ◽  
Mitsuru Hirota
Keyword(s):  
Spatial Variation ◽  
Temporal Variation ◽  
Forest Ecosystem ◽  
Linear Regression Analysis ◽  
Basal Area ◽  
Beech Forest ◽  
Controlling Factors ◽  
Spatial And Temporal Variation ◽  
Canopy Openness ◽  
Co2 Efflux

<p> Soil respiration (Rs) is the second largest carbon flux between the atmosphere and terrestrial ecosystem. Because of the large proportion, even small change in Rs would considerably impact the global carbon cycle. Therefore, it is important to accurately estimate Rs by taking its spatial and temporal variation into consideration. While the temporal variation of Rs and its controlling factors have been well-described, large unexplainable part still has been remained in the spatial variation of Rs especially in the forest ecosystems with complex structures. The objective of this study is to fill the knowledge gap about spatial variation of Rs and its controlling factors in a typical mature beech forest in Japan. Hypotheses of this study were, 1) Rs would show large spatial variation in the mature beech forest, 2) the spatial variation of Rs was mainly influenced by soil water content (SWC) and soil temperature (ST), 3) the two key factors were determined by the forest structures. This study was conducted in a 1- ha permanent study plot in the mature beech forest with significant gap-mosaic structures. To examine these hypotheses, Rs, SWC, ST and parameters related to forest structure, i.e. sum of basal area, diameter at breast height, number of trees, number of species within a radius of 5 m from the Rs measurement points, and canopy openness were measured at 121 points in different season between 2012 to 2013. In this study, all the measurements of Rs were conducted by using alkali-absorption technique.</p><p> Coefficient of variation of Rs was between 25 - 28 % which was similar to that of SWC in all the measurements. The spatial variation of Rs was relatively higher in July, August and September than that in June and October. There was no significant relationship in the spatial variation between Rs and ST in all the measurements, meanwhile, Rs was well explained by SWC in measurements conducted in August, September and October. Multiple linear regression analysis indicated that canopy openness and sum of basal area showed significant positive and negative correlation with SWC, respectively. And canopy openness explained SWC much more than sum of basal area did. This result suggested that SWC, the key factor determined the spatial variation of Rs, cannot be only explained by stems distribution and their characteristics, but also canopy architecture in the forest ecosystem.</p>

scholarly journals The Use of Geogrids in Mitigating Pavement Defects on Roads Built over Expansive Soils

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Richard Shumbusho ◽  
Gurmel S. Ghataora ◽  
Michael P.N. Burrow ◽  
Digne R. Rwabuhungu
Keyword(s):  
Seasonal Changes ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Real Field ◽  
Experimental Program ◽  
Swelling Potential ◽  
Swelling Behaviour ◽  
Wetting And Drying ◽  
Potential Benefits

This study was conducted to investigate the potential benefits of using geogrids in mitigating pavement defects notably roughness and longitudinal cracking on pavements built over expansive soils. The seasonal changes of expansive soils (periodic wetting and drying) cause detrimental effects on the overlying road pavements. Such detrimental behavior of expansive soils was simulated in a controlled laboratory environment through allowing cyclic wetting and drying of an expansive soil underlying a pavement section. The shrink/swell effects of the expansive soil subgrade were examined through monitoring its change in moisture, and measuring deformation of overlying pavement section. The experimental study suggested that a geogrid layer in a reinforced pavement section can reduce surface differential shrinking and swelling deformation resulting from underlying expansive soils by a factor of 2 and 3 respectively in comparison to unreinforced section. Given that an oedometer test which is typically used to predict swelling potential of expansive soils is known to overpredict in-situ soil swell, experimental program also investigated quantitatively the extent to which the oedometer can overestimate swelling behaviour of the real-field scenarios. It was found that oedometer percent swell can overpredict in-situ swelling behaviour of the expansive soil by a factor ranging between 2 and 10 depending upon the period over which the in-situ expansive soil has been in contact with water.

The conductive dusty ionosphere of Saturn

2021 ◽  
Author(s):  
Oleg Shebanits ◽  
Lina Hadid ◽  
Hao Cao ◽  
Michiko Morooka ◽  
Michele Dougherty ◽  
...  
Keyword(s):  
Temporal Variation ◽  
Dusty Plasma ◽  
Local Time ◽  
Equatorial Region ◽  
In Situ Measurements ◽  
Ionospheric Dynamo ◽  
Magnetometer Data ◽  
Remote Measurements

<p>Cassini’s Grand Finale orbits brought us historical first in-situ measurements of Saturn’s ionosphere, showing that it contains dusty plasma in the equatorial region. We present the Pedersen and Hall conductivities of the top ionosphere (10:50 – 12:17 Saturn Local Time, 10N – 20S planetocentric latitude), derived from particle and magnetometer data. We constrain the Pedersen conductivities to be at least 10<sup>-5</sup> – 10<sup>-4</sup> S/m at ionospheric peak, a factor 10-100 higher than estimated previously by remote measurements, while the Hall conductivities are very close to 0 or in fact negative. We show that this is an effect of dusty plasma. Another effect is that ionospheric dynamo region thickness is increased to 300-800 km. Furthermore, our results suggest a temporal variation (decrease) of the plasma densities, mean ion masses and consequently the conductivities over the period of one month.</p>

scholarly journals Spatial and temporal variation of CO<sub>2</sub> efflux along a disturbance gradient in a <i>miombo</i> woodland in Western Zambia

2011 ◽  
Vol 8 (1) ◽  
pp. 147-164 ◽  
Author(s):  
L. Merbold ◽  
W. Ziegler ◽  
M. M. Mukelabai ◽  
W. L. Kutsch
Keyword(s):  
Soil Respiration ◽  
Soil Temperature ◽  
Temporal Variation ◽  
Carbon Content ◽  
Ecosystem Respiration ◽  
Spatial And Temporal Variation ◽  
Co2 Efflux ◽  
Forest Reserve ◽  
Disturbance Gradient ◽  
Total Ecosystem Respiration

Abstract. Carbon dioxide efflux from the soil surface was measured over a period of several weeks within a heterogeneous Brachystegia spp. dominated miombo woodland in Western Zambia. The objectives were to examine spatial and temporal variation of soil respiration along a disturbance gradient from a protected forest reserve to a cut, burned, and grazed area outside, and to relate the flux to various abiotic and biotic drivers. The highest daily mean fluxes (around 12 μmol CO2 m−2 s−1) were measured in the protected forest in the wet season and lowest daily mean fluxes (around 1 μmol CO2 m−2 s−1) in the most disturbed area during the dry season. Diurnal variation of soil respiration was closely correlated with soil temperature. The combination of soil water content and soil temperature was found to be the main driving factor at seasonal time scale. There was a 75% decrease in soil CO2 efflux during the dry season and a 20% difference in peak soil respiratory flux measured in 2008 and 2009. Spatial variation of CO2 efflux was positively related to total soil carbon content in the undisturbed area but not at the disturbed site. Coefficients of variation of efflux rates between plots decreased towards the core zone of the protected forest reserve. Normalized soil respiration values did not vary significantly along the disturbance gradient. Spatial variation of respiration did not show a clear distinction between the disturbed and undisturbed sites and could not be explained by variables such as leaf area index. In contrast, within plot variability of soil respiration was explained by soil organic carbon content. Three different approaches to calculate total ecosystem respiration (Reco) from eddy covariance measurements were compared to two bottom-up estimates of Reco obtained from chambers measurements of soil- and leaf respiration which differed in the consideration of spatial heterogeneity. The consideration of spatial variability resulted only in small changes of Reco when compared to simple averaging. Total ecosystem respiration at the plot scale, obtained by eddy covariance differed by up to 25% in relation to values calculated from the soil- and leaf chamber efflux measurements but without showing a clear trend.

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