Increasing Soil Depth (increasing + soil_depth)

Distribution by Scientific Domains

Selected Abstracts

Soil production in heath and forest, Blue Mountains, Australia: influence of lithology and palaeoclimate

Marshall T. Wilkinson
Abstract An Erratum has been published for this article in Earth Surfaces Processes and Landforms 25(13) 2005, 1683,1686. Recent determinations of soil production from in situ cosmogenic nuclides indicate that production decreases exponentially with soil depth. This contrasts with a long-held assumption that maximum soil production occurs under a soil cover of finite depth. Sites in the Blue Mountains, Australia, show a sharp decrease of soil depth where vegetation changes from forested plateau surfaces to heath-covered spurs, and bands of bare rock in the heath suggest that soil production depends on presence of a finite depth of soil. The substrate varies from hard ferruginized sandstone to soft saprolite. In situ 10Be determinations indicate that apparent rates of erosion and soil production are greater under the relatively thin heath soil than under the thicker forest soil but, in contrast to other studies, these sites do not show significant depth-dependence of apparent soil production. The pattern reflects both hardness variation in the rock substrate and the effect of Late Quaternary climatic change. Optically stimulated luminescence (OSL) dating indicates that soil ,30 cm depth is of Holocene age whereas the deeper soil is substantially older. The age-break coincides with a stone line interpreted as a former surface lag deposit. Assuming that pre-Holocene soil depths were 30 cm less than today, recalculated soil production tends to decrease with increasing depth. Soil production at this site requires soil cover but bare rock patches and vegetation comprise a shifting mosaic. In the long term, average rates of erosion and soil production decrease with increasing soil depth. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Woody plants modulate the temporal dynamics of soil moisture in a semi-arid mesquite savanna,

ECOHYDROLOGY, Issue 1 2010
Daniel L. Potts
Abstract Climate variability and human activities interact to increase the abundance of woody plants in arid and semi-arid ecosystems worldwide. How woody plants interact with rainfall to influence patterns of soil moisture through time, at different depths in the soil profile and between neighboring landscape patches is poorly known. In a semi-arid mesquite savanna, we deployed a paired array of sensors beneath a mesquite canopy and in an adjacent open area to measure volumetric soil water content (,) every 30 min at several depths between 2004 and 2007. In addition, to quantify temporally dynamic variation in soil moisture between the two microsites and across soil depths we analysed , time-series using fast Fourier transforms (FFT). FFT analyses were consistent with the prediction that by reducing evaporative losses through shade and reducing rainfall inputs through canopy interception of small rainfall events, the mesquite canopy was associated with a decline in high-frequency (hour-to-hour and day-to-day) variation in shallow ,. Finally, we found that, in both microsites, high-frequency , variation declined with increasing soil depth as the influence of evaporative losses and inputs associated with smaller rainfall events declined. In this case, we argue that the buffering of shallow soil moisture against high-frequency variations can enhance nutrient cycling and alter the carbon cycle in dryland ecosystems. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Micro-scale Systematic Sampling of Soil: Heterogeneity in Populations of Fusarium oxysporum, F. solani, F. roseum and F. moniliforme

M. C. Rodríguez-Molina
Abstract The variability of Fusarium spp. density in soil was studied in a field located in Badajoz (south-western Spain). The upper 40 cm of each side of a 1 m × 1 m × 1 m pit were sampled intensively, taking soil samples from points 10 cm apart. The species isolated were F. oxysporum, F. solani, F. roseum and F. moniliforme. For all four sides of the pit population densities of F. oxysporum, F. solani and F. roseum significantly decreased with increasing soil depth and for all the four layers significant differences were detected between sides of the pit. Horizontal variability also occurred on a smaller sampling scale: when a layer of a side was sampled, densities might be significantly different between points in the layer. However, no clear trend in horizontal variability was observed for any species. These findings demonstrate that Fusarium spp. populations were heterogeneously distributed in this reduced soil volume. Zusammenfassung Die Variabilität der Dichte von Fusarium spp. im Boden wurde in einem Feld in Badajoz (Südwestspanien) untersucht. Die oberen 40 cm jeder Seite einer 1 m × 1 m × 1 m großen Grube wurden intensiv beprobt, wobei im Abstand von jeweils 10 cm Bodenproben entnommen wurden. Aus den Proben wurden F. oxysporum, F. solani, F. roseum und F. moniliforme isoliert. An allen vier Seiten der Grube nahmen die Populationsdichten von F. oxysporum, F. solani und F. roseum mit zunehmender Bodentiefe signifikant ab. Bei allen vier Schichten wurden signifikante Unterschiede zwischen den Seiten der Grube festgestellt. Bei kleinerem Beprobungsmaßstab wurde auch horizontale Variabilität festgestellt: Wenn eine Schicht einer Seite beprobt wurde, unterschieden sich die Dichten zwischen den einzelnen Punkten der Schicht teilweise signifikant. Für keine Art war jedoch eine deutliche Tendenz bei der horizontalen Variabilität feststellbar. Die Ergebnisse zeigten, daß die Populationen von Fusarium spp. in diesem kleinen Bodenvolumen heterogen verteilt waren. [source]

FTIR-spectroscopic characterization of humic acids and humin fractions obtained by advanced NaOH, Na4P2O7, and Na2CO3 extraction procedures

Michael Tatzber
Abstract Aim of our study was the development of the methodological basis for the characterization of humic fractions of a long-term field experiment. Humic acids (HAs) were extracted from three layers of a nontilled soil using three different extractants (1 M NaOH, 0.1 M Na4P2O7, 1 M Na2CO3), and the humin fraction was enriched. NaOH as extractant for FTIR analysis of humic substances yields higher resolved IR spectra, especially in the important regions of stretching vibrations including aromatic and aliphatic groups and in the fingerprint area including amides, aliphats, and aromats than the other extractants. The NaOH extraction has lower extraction yields as compared to Na4P2O7 and Na2CO3 and represents a different part of the soil organic matter (SOM). This is reflected by lower C : N ratios and higher E4 : E6 and fulvic acid,to,humic acid ratios as compared to the other extractants. The FTIR band areas of HA fraction obtained by NaOH showed an increase of the aromatic and carbonyl groups and a decrease of amide groups with increasing soil depth. Aliphatic groups showed contradicting results: The bands of the stretching vibrations increased, and the band of the bending vibrations decreased. We assume that band interactions in the bending vibrations were responsible for that phenomenon under the assumption of an increase of aliphatic groups with increasing soil depth. The IR bands of the enriched humin fraction showed a decreasing trend in case of both aliphatic bands deriving from stretching vibrations and an increase of aromatic characteristics with depth. Our study led to the conclusion that HA fractions obtained by 1 M NaOH represent a small and dynamic fraction indicated by the measured yields in combination with values of Nt, C : N, E4 : E6 ratios, and ratios of fulvic acids (FA) to HA. The humin fraction has a high contribution to the total organic C and represents a more stabilized fraction of SOM which still shows changes in its aromatic and aliphatic characteristics with soil depth. [source]