Soil Silt Content Research Articles

Dasylirion cedrosanum Trelease (Nolinaceae) Density Varies Depending on Elevation and Slope in the Northeast of Zacatecas, Mexico

There is little or no specific and concise information on the ecological conditions which constrain distribution, abundance, and density of Dasylirion cedrosanum Trelease keeping in mind that such knowledge is indispensable to promote and support plantations and reforestation programs in order to confront the consequences of a possible depletion of natural populations. Therefore, the aim of this study was to evaluate D. cedrosanum density as related to ecological factors such as latitude, longitude, altitude, slope, soil texture fractions, pH, electric conductivity, available nitrogen and phosphorus contents, and organic matter content on a xerophytic scrub in the northeast of the Mexico’s state of Zacatecas. Data from 41 square–shaped sampling units of 1.000 m 2 each from an area of 2.422.2 ha where altitude varies from 2.000 to 2.356 masl, and slope inclination changes from moderate (5.5%) to steep (44.2%) was analyzed through linear relationships, quadratic functions, and principal components analysis. Results provide compelling evidence about D. cedrosanum density depends on elevation, inclination, and soil silt and sand contents. A triangularshaped dispersion of observations when density is plotted against each soil, silt or sand, contents was appreciated. A significant humped trend suggest that sites having slopes around 20%, although it could be in the 10 to 30% slope range, provides a better habitat for this species. D. cedrosanum plants are scarcer, that is, present at low and minimum densities (< 259 plants ha-1) in the sampled units characterized by high

Using palm-mat geotextiles for soil conservation: II. Effects on in situ soil particle size distribution and nutrient concentration

Although geotextile mats have considerable potential for soil conservation, field studies on their impacts on soil particle size distribution and nutrient conservation are scant. Hence, field experiments were conducted at Hilton, east Shropshire, U.K. (52°33′5.7″N, 2°19′18.3″W) during 2007–2009, to study the impacts of palm-mat geotextiles on topsoil (0–5 cm) particle size distribution and changes in selected nutrients (total P, K, Ca, Mg, S, Zn, Cu, Fe, Mn, Mo and Cl). Geotextile-mats constructed from Borassus aethiopum (Borassus palm of West Africa) and Mauritia flexuosa (Buriti palm of South America) leaves are termed Borassus mats and Buriti mats, respectively. Ten runoff plots (10 × 1 m on a 15° slope) were established, with duplicate treatments. The treatments were: (i) bare soil; (ii) permanent grass; (iii) bare soil with 1 m Borassus-mat buffer zones (area coverage ~ 10%) at the lower end of the plots; (iv) bare soil with 1 m Buriti-mat buffer zones (area coverage ~ 10%) at the lower end of the plots; and (v) completely-covered with Borassus mats. Initial and final topsoil samples were collected and analysed for sand (fine, medium and coarse), silt (fine, medium and coarse), clay and selected nutrients. Results revealed that soil silt and clay contents significantly ( P < 0.05) decreased in the Borassus completely-covered plots with a concomitant increase in proportion of sand content after ~ 2 years. Both Borassus and Buriti buffer strip plots also had lower soil clay contents, indicating that palm-mat geotextile cover significantly affected particle size distribution, even after only 2 years. Buriti mat-cover within the buffer strip plots resulted in notably higher decrease in mean ( n = 2) clay content, with a concomitant increase in mean ( n = 2) sand contents compared with mean ( n = 18) clay and sand contents of bare soils within the same plots. Data indicate that total P and total K contents with Borassus completely-covered plots significantly ( P < 0.01) increased and total Ca content decreased after ~ 2 years. However, except grassed plots, all plots had significant ( P < 0.05) increases in total P concentrations. Borassus buffer strip plots also had significant ( P < 0.05) decreases in total Ca contents over the initial contents. The increases in total P and K contents within Borassus complete-cover plots were significantly ( P < 0.05) higher than both grassed and Buriti buffer strip plots. Borassus buffer strip plots significantly ( P < 0.05) decreased total Ca content compared to bare and grassed plots. Treatments had no significant ( P > 0.05) effects on changes in other selected nutrients (total Mg, S, Zn, Cu, Fe, Mn, Mo and Cl) concentrations. In summary, it is evident that despite significant ( P < 0.05) decreases in soil clay and total Ca contents, use of Borassus mats as buffer strips was very successful in conserving or improving other selected soil properties. ► Impacts of geotextiles on soil texture and nutrient retention were studied ► Buffer strip plots had lower soil clay contents than bare plots ► Borassus complete-covered plots had less clay and silt contents than initial soil ► Total P content increased in the Borassus complete-covered plots over initial soil ► Mat cover had no effect on changes in total Mg, S, Zn, Cu, Fe, Mn, Mo and Cl

A study on the annual runoff change and its relationship with water and soil conservation practices and climate change in the middle Yellow River basin

Based on the long-term hydrological and meteorological series, DEM, soil database and documents of soil conservation measures of the middle Yellow River, investigations are made on the spatial and temporal changes of runoff and the impact of 11 factors, which include rainfall, temperature, terrain slope, drainage density, gravel, sand, silt, and organic carbon content in soil, water consumption, and soil conservation measures. The results show that the total runoff generated from the middle Yellow River had a decreasing trend in the past 60 years, with two abrupt falls around the years 1971 and 1991. In the spatial dimension, runoff modulus grew from the north to the south and from the west to the east, and the largest gradient of spatial change of runoff modulus happened during the period of 1956–1970 before the first falls of the total runoff. In the period 1954–2009, the average annual rate of temporal change of runoff modulus increased acceleratedly outward from the northwest of the middle Yellow River with a concentric ring pattern. Correlation analysis of runoff modulus with potential influencing factors in the spatial perspective reveals that the spatial distribution of the runoff modulus is principally the results of the regional variation of natural conditions. The results of the correlation analysis of the temporal series of runoff coefficient and influencing factors suggest that climate change, hydraulic engineering and soil conservation measures, were all the major causes of runoff reducing in the second half of the last century in the middle Yellow River. For the whole middle Yellow River, climate change contributed over 40% of the runoff deviations in the 1960s, 1970s and 1990s, while water consumption induced also over 40% runoff reduction in the 1960s, 1970s and 1980s. The runoff reduction due to hydraulic engineering was about 2–3 times of that caused by soil conservation measures, and both of them increased continuously from the 1960s to the 1980s, and kept at a higher level in the 1990s. The contribution of different causes to runoff deviation was variable in different drainage areas. Generally, in the semi-arid areas climate change played a decreasing role in runoff reduction comparing with other causes, while in the semi-humid areas it induced a higher and more variable proportion of runoff deviation according to the decade means.

Characteristics of hummocked and non-hummocked Colorado riparian areas and wetlands

Several hummock formation theories exist in the scientific literature, but are rarely mentioned in management publications where only one or two other theories are stressed. Our objectives were to identify and describe the edaphic, climatic, topographic and vegetation characteristics of riparian areas and wetlands in Colorado that do and do not support hummocks, and to classify hummocked sites according to hummock characteristics. 25 natural resource professionals throughout Colorado identified ten sites each that were a mix of hummocked and non-hummocked in proportion to their local abundance, from which 40 hummocked and 40 non-hummocked sites were randomly selected for sampling. Plant functional group canopy cover was determined using Daubenmire cover classes. Soil samples were collected and numerous site characteristics were recorded. Hummock size, shape and density were measured at hummocked sites. Forward model selection and multiple logistic regression were used to determine relationships between site characteristics and odds of hummock occurrence. Mean winter precipitation, mean annual temperature and forb cover were negatively related to odds of hummock occurrence while soil silt content and plant species richness were positively related to odds of hummock occurrence. Cluster analysis resulted in three groups of hummocked sites with differing hummock morphology, vegetation and climatic characteristics. Differential frost heave and plant biomass accumulation were likely involved in hummock formation at sites examined for this study, but conditions expected to occur following cryoexpulsion of clasts were not observed.

Soil Salinization Related to Soil Morphological and Physicochemical Characteristics in the Luohui Irrigation Scheme, China

The physicochemical properties of soil profiles in the Luohui Irrigation Scheme located along the southeastern edge of the Loess Plateau in China were investigated. The scheme covers part of a river terrace system along the Luohe River. The study area was approximately 31 × 16 km with a north–south gradient and a difference in altitude of about 40 m. The terrace system was divided into a high terrace (HT; 371–389 m), an intermediate terrace (IT; 360–370 m), and a low terrace (LT; 344–359 m). The HT and LT soils showed different trends in salt accumulation in their surface horizons and overall soil profiles. Surface soils and soil profiles on the HT contained a greater amount of clay and silt than those on the LT, which had coarser soil textures. The IT had soils with characteristics intermediate between those of the HT and LT. A negative relationship was found between soil pH and soil electrical conductivity, and positive ones between soil electrical conductivity and silt contents and between water electrical conductivity and the sodium adsorption ratio. Soil morphological characteristics and soil salinization were related to the topographic sequence of the soils. Soil salinization showed spatial pattern within this irrigation scheme and subsoil texture was a useful indicator of the state of salt accumulation. This information may help in developing guidelines for agricultural soil management that are based on the underground water dynamics and soil morphological properties.

Effect of available burrow densities of plateau pika (Ochotona curzoniae) on soil physicochemical property of the bare land and vegetation land in the Qinghai-Tibetan Plateau

The available burrow densities of plateau pika (Ochotona curzoniae) regulate the soil physicochemical property in alpine meadow. A field survey was conducted to investigate the effect of available burrow densities of plateau pika on soil physicochemical property of bare land (bare patch produced by burrowing behavior of plateau pika) and vegetation land (land covered with vegetation). This study indicated that the increase in available burrow of plateau pika caused the soil water content at 0–10cm layer of bare land and that at 10–20cm of vegetation land to reduce, and caused the soil water content at 10–20cm layer of bare land and that at 0–10cm layer of vegetation land to firstly increase and then decline. In the increasing process of available burrow of plateau pika, the soil silt content firstly increased and then decreased, and soil sand content firstly decreased and then increased. With the increase of available burrow of plateau pika, the soil porosity at 0–10cm layer of bare land and that at 10–20cm layer of vegetation land decreased, while the soil porosity at 10–20cm layer of bare land and that at 0–10cm of vegetation land firstly increased and then decreased. Soil pH value, soil organic matter, total nitrogen and total phosphorus content firstly increased and then decreased, peaking at 14 available burrows per 625m2, while total soil potassium content did not respond to available burrow densities of plateau pika. This study suggested that the proper available burrows existing in the alpine meadow increased soil permeability, accelerated soil moisture to penetrate deeply, increased the proportion of soil silt, and improved the soil nutrient; however, this beneficial effect was strongly influenced by the available burrow density of plateau pika, implying that plateau pika did not benefit soil structure when its available burrow was over 34 number/625m2.

The Impact of Plant Hedgerow in Three Gorges on the Soil Chemicophysical Properties and Soil Erosion

Through the research and sampling analysis on different plant hedgerow in sloped farmland in Three Gorges reservoir area, we will conduct research on the impact of plant hedgerow in Three Gorges on the chemicophysical properties of soil and soil erosion. The results show that the plant hedgerow mainly composed by Morus alba, Citrus reticulata, Zanthoxylum bungeanum, Vitex negundoand Begonia fimbristipula can decrease the soil density as well as sand content and increase soil porosity, soil water content, silt content and clay content to some extent. The organic matter, nitrogen, phosphorus, potassium and cation exchange capacity and other chemical indices of soil in different locations in plant hedgerow indicate as maximum in on-band, minimum in inter-band, middle both upper-band and below-band. In the same slop with no plant hedgerow, the organic matter, nitrogen, phosphorus, potassium and cation exchange capacity and other chemical indices of soil show a trend of increasing from the top to the bottom of the slop, which reveals that these substances own a feature of accumulation by moving to the bottom. The strength of soil anti-corrosion in different plant hedgerow is: Vitex negundoand (79.2%)&gt; Citrus reticulata (36.4%)&gt; Morus alb (22.4%)&gt; Zanthoxylum bungeanum (18.9%)&gt; Begonia fimbristipula (15.3%)&gt; CK (8.7%), and the soil anti-corrosion indices in plant hedgerow are decreasing with the increase of soil immersion time, besides, the former and the latter are 3 times polynomial function. For those 5 plant hedgerows, Vitex negundoand owns the best impact on improving soil chemicophysical properties and reducing soil erosion.

Soil organic carbon storage in moutain grasslands of the Lake Plateau at Mt. Durmitor in Montenegro

Soil organic C storage in mountain areas is highly heterogeneous, mainly as a result of local-scale variability in the soil environment and microclimate. The aims of the present study were to estimate soil organic carbon density (SOCD) and stocks in leptosol on morainic deposits of high-altitude grasslands of the Lake Plateau of Mt. Durmitor National Park in Montenegro, and determine the soil variables that can be used as factors to determine the SOCD at 28 soil profiles. Our results indicated that SOC storage in the top 40 cm of the alpine grasslands were estimated at 560 414.86 t C, or 152.66 t?ha-1, with an average density of 15.27 kg?m-2. The soil organic carbon density increased significantly with soil moisture, clay and silt content, but only moderately with mean annual temperature. In conjunction, these variables could explain approximately 51% of the total variation in SOC density.

Medicinal Mushroom Growth as Affected by Non-Axenic Casing Soil

Ten different casing soils were collected from two soils at two depths (0.2 and 2.0 m below soil surface) to examine the relationships between the physical properties of non-axenic casing soil and yield, number and weight of the medicinal mushroom Agaricus blazei ss. Heinemann. The results showed that soil clay content and bulk density were negatively correlated with the mushroom yield, respectively, but soil silt content and water-holding capacity were found to be positively correlated with the yield. The number of mushrooms was negatively correlated with soil water-holding capacity but positively correlated with soil clay, bulk density and porosity. The weight of mushroom was positively correlated with the content of soil fine sand and negatively correlated with the contents of soil coarse sand, total sand and clay. Neither soil depth nor different soil combinations affected the yield and number of mushrooms, but the mushroom weight was affected by the soil combinations and soil depth, so interplay in the fructification process with the physical characteristics of casing is complicated.

Distribution of different forms of Mn and their association with soil properties in arid zone soils of Punjab, India

Six pedons from arid zones soils of Punjab, north western India, were investigated for different forms of manganese (Mn): total Mn, diethylenetriamine penta-acetic acid (DTPA)-extractable Mn, soil solution plus exchangeable Mn, adsorbed Mn onto inorganic sites, and oxide surfaces, and Mn bound by organic sites. Total Mn content ranged from 241–517 mg kg−1, DTPA-extractable Mn content ranged from 1.40–4.52 mg kg−1, soil solution plus exchangeable Mn content ranged from 0.04–0.30 mg kg−1, Mn adsorbed onto inorganic sites ranged from 34–109 mg kg−1, and that onto oxide surfaces ranged from 28–173 mg kg−1. The Mn bound by organic sites ranged from 14–56 mg kg−1. The forms of Mn did not exhibit any consistent pattern of distribution. Irrespective of the different fractions of Mn their content was higher in the fine textured soils as compared to the coarse textured soils. The soil solution plus exchangeable Mn held onto organic site and oxide surface (amorphous) increased with increase in organic carbon, silt and clay contents. The Mn adsorbed onto inorganic site (crystalline) increased with only silt and clay content. The DTPA-Mn increased with increase in organic carbon content, whereas Mn adsorbed onto oxide surfaces increased with an increase in organic carbon, silt and clay. However, both these fractions decreased with an increase in calcium carbonate and pH. Total Mn was strongly correlated with organic carbon, silt and clay content of soil. Among the forms, Mn held on the organic site, water soluble + exchangeable and Mn adsorbed onto oxide surface were positively correlated with DTPA-extractable Mn. DTPA-extractable Mn and soil solution plus exchangeable Mn seem to be good indices of Mn availability in soils and are helpful for correction of Mn deficiency in the soils of the region.

Soil properties related to potential particulate matter emissions (PM10) of sandy soils

Little information is available on the effect of properties of coarse textured soils on the emission of fine particulate matter (PM10). In this study was evaluated the effect of textural fractions (clay, silt and sand), organic matter contents (OM) and soil moisture of 7 sandy to loamy-sand soils on potential PM10 emissions by means of wind tunnel simulations. PM10 emissions decreases linearly along the whole soil moisture range in loess developed soils (Anguil and Santa Rosa), and above a given soil moisture in soils developed on sandy sediments (Villa Mercedes, Abra Pampa, Potrok Aike, Rio Mayo and Pilcaniyeu). Soils with higher PM10 emissions had high threshold moisture contents (TMC, soil moisture above which the PM10 emission was negligible) excepting for Potrok Aike (PA) that had low PM10 emissions and high TMC (8%) as a consequence of its relative high OM contents. Moisture effects on PM10 emissions decreased in a logarithmic way when OM contents increased in relation to soil silt contents (P < 0.01). In general, maximum PM10 emissions were higher in soils with higher silt contents, excepting PA which

Estimating base cation weathering rates in Canadian forest soils using a simple texture-based model

Mineral weathering is the primary source of long-term buffering capacity in soils and is important for forest nutrient sustainability. Regional assessments of weathering rates in Canada and the U.S. have employed an empirical clay-based Soil Texture Approximation (STA) owing to limited data availability, although the STA is rarely calibrated before application to a study area. Soil weathering rates estimated with the STA at 75 sites in Canadian forests (6–367 eq ha−1 year−1) were on average seven times lower than estimates obtained using the PROFILE model and when mineralogy was not available, the Analysis to Mineralogy model and parameter estimation (143–2,119 eq ha−1 year−1). Comparison with a catchment mass balance at a subset of sites in Ontario (n = 19) demonstrated the reliability of PROFILE weathering estimates. A revised (generalized) STA model for total base cation weathering was developed at the 75 study sites to incorporate soil silt content (%) and loss-on-ignition (LOI, %) (BCw = (1.73 + 0.03 · silt − 0.06 · LOI) · 1,000 · depth). The model performance (Radj2 = 73%) and relative bias (−1%) suggested that the revised STA may have broad application to forest soils in Canada but may not necessarily be suited to all soil texture classes.

Assessment of wheat and maize water productivities and production function for cropping system decisions in arid and semiarid regions

AbstractThe great challenge of the agricultural sector in countries located in arid and semiarid regions faced with severe water scarcity is to produce more food from less water. This may be achieved by increasing the crop water productivity (WP). Based on experiments conducted in different regions of Iran, it was found that the range of wheat WP was greater than that reported earlier by the FAO. The maize WP was high in the northwestern regions of Iran and less in the southwest. The wide ranges of WP (0.5–1.8 kg m−3 for wheat and 0.3–2.3 kg m−3 for maize) indicate tremendous opportunities for increasing agricultural production with less water. The variability of crop WP can be ascribed to climate, cropping calendar, soil characteristics, and irrigation water management. Wheat and maize WP of 1.5 and 1.7 kg m−3 were recommended as an optimum level to be considered in the cropping system of potential regions. Irrigation water applied for an optimum level of wheat and maize WP was about 2650 and 5900 m3 ha−1, respectively. The maximum wheat WP occurred under deficit irrigation, while for maize it was measured under full irrigation. Regions with higher annual rainfall and high silt content in soil were more productive under deficit irrigation management. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Distribution characteristics and influencing factors of soil organic carbon in alpine ecosystems on the Tibetan Plateau transect, China

The undisturbed regions along the Qinghai-Tibet Highway crossing the natural zones of montane desert, alpine meadow-steppe, and montane shrub-coniferous forest were chosen as the study areas. Soil samples were collected at 23 sites and the relations between the influencing factors and distribution of soil organic carbon (SOC) content were studied. The results indicated that the order of SOC content for the whole soil profile with different vegetations and in the horizontal direction was shown as below: forest>shrub>meadow>steppe>desert. All the SOC contents of the top 10 cm soil layers of forest, shrub and meadow vegetations, as well as that of the top 20 cm soil layers in steppe, in the vertical direction, were higher than those of corresponding lower soil layers. However, the SOC content in the desert soil was in accordance. The grey correlative analysis between the climatic factors and SOC content in the top soil show that precipitation was the dominant climatic factor affecting the distribution of SOC in the Tibetan Plateau transect. The influence of precipitation on the horizontal distribution of SOC decreased with the increase of precipitation in the horizontal direction. The vertical distribution of SOC along the soil profile was greatly affected by precipitation or the soil clay content in top soil layers, and was clearly influenced by soil silt content or sand content in lower soil layers, as well. The influences of both soil bulk density and soil pH on the vertical distribution of SOC along the soil profile gradually declined. The plant biomass was the most important biotic factors affecting the distribution of the SOC.

Impacts of a regional drought on the productivity, dieback, and biomass of western Canadian aspen forests

We examined the impacts of a severe, regional drought (2001–2002) on trembling aspen ( Populus tremuloides Michx.) forests in the western Canadian interior. A total of 150 plots were established in 25 study areas as part of a regional-scale study (CIPHA). Aspen health and mortality were assessed annually during 2000–2005, and changes in stem biomass were estimated using tree-ring analysis and plot-based measurements. Net mean increment in living biomass for all plots was 2.2 t·ha–1·year–1 during 2000–2002 but subsequently decreased to near zero. This collapse was driven by a more than two-fold increase in stem mortality and a 30% decrease in regional stem growth during and following the drought. The analysis showed that spatial variation in aspen productivity and biomass across the region was positively related to multiyear mean values of a climate moisture index and mineral soil silt content but was negatively related to levels of insect defoliation and wood-boring insects. In contrast, mortality and dieback was best correlated with minimum annual climate moisture index, which provided a measure of short-term drought severity. The results support previous studies showing that aspen forests are moisture limited in this region, which poses concerns for the future under a changing climate.

Effect of land use changes on some important soil properties in cotton based farming systems in Burkina Faso

Continuous and intensive cropping without restoration of soil fertility has depleted the nutrient base of most soils in the semi arid zone. A field survey was carried out in 2000 in Bala village in the cotton production zone of western Burkina Faso to assess the effect of land use changes on soil chemical and physical changes. The methodology consisted of land use analysis at contrasted periods, field sampling and measurements, and farmers' interview. Land use analysis was done at three periods: 1952, 1981 and 1999. Soil samples were taken in farmers' fields selected on the basis of their equipment level and the cultivation duration. Two fallows were selected and considered as control situation. Aerial photos analysis showed that the proportion of the land under cultivation was increased at about 38.3% from 1952 to 1999. Soil chemical analysis showed that soil total P and K were significantly higher in soils manually cultivated than in soils cultivated with animals and tractors. Soil pH was lower in motorized farmers' fields than in the other categories. Soil organic matter and N content were not affected by all the studied factors. The percentage of sand in the soil increased with the performance of the equipment. The opposite situation was observed with soil silt content. Soil stability was not significantly affected by any of the factors. But the numerical values showed a more stable soil structure under fallows than when soils were cultivated. From the results, it appeared that the fundamental cause of land degradation in the area is the farming system than the nature of the crop being grown. International Journal of Biological & Chemical Sciences Vol. 1 (1) 2007: pp. 7-14

Site and Stand Conditions Associated with Pine False Webworm Populations and Damage in Mature Eastern White Pine Plantations

Abstract The influence of site and stand conditions on pine false webworm (Acantholyda erythrocephala [L.], Hymenoptera: Pamphiliidae) population densities and host damage was evaluated in 22 eastern white pine (Pinus strobus L.) stands in northern New York State. Mean pine false webworm density was positively related to stand size (ha) and inversely related to soil silt content (A-horizon) after holding stand size constant. Percent radial growth loss (during the first five years after defoliation began) was inversely related to soil carbon content (B-horizon) and inversely related to fine sand content (A-horizon) after holding B-horizon carbon constant. Severe radial growth suppression (missing or discontinuous growth rings) and white pine mortality were inversely related to live crown ratio. The frequency of trees with missing growth rings was inversely related to soil nitrogen (A-horizon) after holding live crown ratio constant. Stands located on sandy glacial lake shoreline/delta deposits had more coarsely textured soils with lower levels of organic matter and nitrogen and had slower height growth rates, lower tree diversity, greater relative dominance of white pine, and higher levels of pine false webworm defoliation than stands on adjacent landforms. These results may be useful to foresters managing eastern white pine stands in areas where similar site and stand conditions predominate and pine false webworm occurs.

The relationship between WRB soil units and heavy metals content in soils of Catamarca (Argentina)

Trace element content in soils is mainly dependent on the nature of parent rocks from which the soil material is derived, as well as weathering and soil forming processes. Despite the close relationship between soil and rock, the soil forming processes modify the regolith and redistribute the content of heavy metals in the soil horizons. The World Reference Base (WRB) is a morphogenetic system of soil classification strongly based in soil genesis at the level of Reference Soil Groups (RSG). Present differences in trace elements content between different RSG may reflect the impact of pedogenic pathways of each RSG on the original trace element distribution. The natural variation of heavy metal content is a preliminary step in assessing heavy metal contamination in soils. Therefore, the term geochemical background became an important reference with increasing environmental awareness. The concentration and distribution of Cd, Cr, Cu, Ni, Pb, and Zn were investigated in thirty profiles of Catamarca in the municipal district of Fray Mamerto Esquiú, Argentina. The heavy metals content, except for Cd, is highly dependent on RSG according to WRB. Occasional or continuous contribution of sediments as in alluvial soils becomes the soil forming processes that acquires greater importance in the distribution of heavy metals. The organic matter content is the soil property that comes out as relevant at lower levels of Fluvisols when Humic or Mollihumic qualifiers apply. All studied soils show extremely high Pb in relation to the surrounding bedrock. This confirms that the infilling of the alluvial valley is not derived from the surrounding bedrock but it must come from a different source. The increase in the silt content of soils in the southern part of the alluvial valley are well reflected by Ni content. Therefore, pedogenic processes have had little influence in regional Ni distribution. The upper limit of the background, which allows distinguishing between natural element and anomalous concentrations are presented. The heavy metal showing the greatest number of samples with slight enrichment anomalies is Cd. Slight enrichment anomalies in Cd, Cr, Cu, Pb and Zn were detected in profile 29 confirming an anthropogenic pollution.

Estimating dust emission from a sandbank on the downstream Jhuoshuei River under strong wind conditions

An empirical emission model based on experimental data was proposed. The total suspended particulates (TSP) emission model obtained by using stepwise multiple-regression analysis was significant ( p<0.001); moreover, the relatively high value of R-squared ( R 2=0.85), which indicated that four parameters included in the model (air temperature, soil silt content, soil moisture content, and wind speed) accounted for the particulate emissions from a sandbank. The results of the multiple-regression analysis demonstrated that the TSP emission factors increased with increase in air temperature, soil silt content and wind speed, but were inversely affected by the soil moisture content. The model equation verified the experimental results and proved itself to be an important tool in predicting the dust emissions from a sandbank under strong wind conditions.

The influence of American Chestnut ( Castanea dentata) on nitrogen availability, organic matter and chemistry of silty and sandy loam soils

American chestnut trees once dominated vast areas of deciduous forest in eastern North America, but the exotic chestnut blight almost eliminated the species from the region. Introduction of blight-resistant American chestnut hybrids will probably start in the next decade after many years of tree breeding. What were the historic effects of chestnut on forest soils, and what changes may follow reintroduction of hybrid chestnuts? A site in southern Wisconsin provided an opportunity to examine the effect of chestnut trees on soil properties. At this site, 600 km northwest of chestnut's historic distribution, naturalized chestnuts have spread throughout an intact mixed-species forest from nine planted trees. The site contains soil developed on a silty loess-mantled ridge that abuts sandier hillslopes, allowing the effects of individual chestnuts to be examined on two soil types. I sampled and analyzed forest floor and mineral soils beneath canopies of individual American chestnuts and the surrounding mixed-species deciduous forest on fine-silt and sandy-loam soil types. On sandy loam soils, total soil carbon (C) and nitrogen (N), inorganic N and net mineralization and nitrification rates were 10–17% higher beneath chestnut canopies compared to soils beneath mixed-species deciduous forest. The pool of total soil N beneath chestnut canopies was positively related to the silt content of the sandy loam soils. In contrast, there were no differences between properties of chestnut canopy and mixed-species deciduous forest soils on the fine silt texture class. On sandy loam soil conditions common throughout the pre-blight distribution of American chestnut, soil biogeochemical processes differ beneath individual chestnut trees relative to a diverse mixture of deciduous species. These findings suggest that widespread chestnut reintroduction has the potential to alter both stand- and watershed-scale processes.