Profundal Sediment Organic Content and Physical Character Do Not Reflect Lake Trophic Status, but Rather Reflect Inorganic Sedimentation and Exposure

1992 ◽  
Vol 49 (7) ◽  
pp. 1431-1438 ◽  
Author(s):  
D. J. Rowan ◽  
J. Kalff ◽  
J. B. Rasmussen
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Bulk Density ◽  
Trophic Status ◽  
Organic Content ◽  
Sedimentation Rates ◽  
Lake Surface ◽  
Lake Trophic Status ◽  
Sediment Organic Content ◽  
Lake Surface Area

An analysis of profundal sediment data from 83 north-temperate lakes shows that increasing inorganic sedimentation and exposure (or lake surface area) results in lower organic content and water content, and greater bulk density. Because sedimentation rates are unavailable for most lakes, we estimate sedimentation rates from readily available catchment sediment loads using a mass-balance model. The mass-balance estimate of sediment retention (per square metre of depositional zone) is an excellent predictor of measured inorganic sedimentation rates for a data set covering 19 lakes (R2 = 0.92). Multiple regressions are used to predict organic content, water content, and bulk density of profundal sediment from inorganic sedimentation rates and either exposure or lake surface area, which are surrogates for the energy of the depositional environment. These analyses explain 76, 74, and 66% of the between-lake variation in the three sediment parameters, respectively. Sediment organic content is not related to lake trophic status (chlorophyll a) and is negatively correlated with net organic matter sedimentation rates. The common occurrence of organic-rich sediments in oligotrophic shield lakes is, therefore, not a reflection of high organic matter inputs, but rather the extremely low inputs of mineral sediments to these lakes.

The Distribution of Nucula Turgida (Bivalvia: Protobranchia) From Dublin Bay, Ireland, and the Effect of Sediment Organic Content

1986 ◽  
Vol 66 (1) ◽  
pp. 119-130 ◽  
Author(s):  
James G. Wilson ◽  
Colin Shelley
Keyword(s):  
Organic Matter ◽  
Clay Fraction ◽  
Fine Sand ◽  
Organic Content ◽  
Muddy Sand ◽  
Sediment Organic Content

Recent investigations (Walker & Rees, 1980; Davis & Wilson, 1983b) have shown that the protobranch bivalve Nucula turgida (Leckenby and Marshall) occupies an important niche in the ecology of Dublin Bay, where it is the dominant organism over much of the southern part of the outer bay. This is an area of moderately sorted fine sand (Harris, 1980) with a pelite (silt and clay) fraction of less than 10% and a consequently low percentage of organic matter of around 1% (Davis & Wilson, 1983 b). Trevallion (1965) described the N. turgida habitat as one of firm muddy sand, adding that the animals avoided mud due to their inability to maintain position or feeding and respiratory currents and also avoided gravel due to their inability to burrow in coarse substrates.

Organic matter and nitrogen content of the forest floor in even-aged northern hardwoods

1984 ◽  
Vol 14 (6) ◽  
pp. 763-767 ◽  
Author(s):  
C. Anthony Federer
Keyword(s):  
Organic Matter ◽  
Nitrogen Content ◽  
Bulk Density ◽  
Forest Floor ◽  
Mineral Soil ◽  
Organic Content ◽  
Stand Age ◽  
Clear Cutting ◽  
Mature Forest ◽  
Forest Floors

Organic content of the forest floor decreases for several years after clear-cutting, and then slowly recovers. Thickness, bulk density, organic matter, and nitrogen content of forest floors were measured for 13 northern hardwood stands in the White Mountains of New Hampshire. Stands ranged from 1 to about 100 years in age. Forest-floor thickness varied significantly with stand age, but bulk density, organic fraction, and nitrogen fraction were independent of age. Total organic content of the forest floor agreed very well with data from Covington's (W. W. Covington 1981. Ecology, 62: 41–48) study of the same area. Both studies indicated that mature forest floors have about 80 Mg organic matter•ha−1 and 1.9 Mg nitrogen•ha−1. Within 10 or 15 years after cutting, the organic matter content of the floor decreases to 50 Mg•ha−1, and its nitrogen content to 1.1 Mg•ha−1. The question whether the decrease is rapid and the minimum broad and flat, or if the decrease is gradual and the minimum sharp, cannot be answered. The subsequent increase to levels reached in mature forest requires about 50 years. Some of the initial decrease in organic matter and nitrogen content of the forest floor may be caused by organic decomposition and nitrogen leaching, but mechanical and chemical mixing of floor into mineral soil, during and after the harvest operation, may also be important. The difference is vital with respect to maintenance of long-term productivity.

scholarly journals Estimating Soil Thermal Diffusivity Using Pedotransfer Functions with Nonlinear Regression

2018 ◽  
Vol 12 (1) ◽  
pp. 164-173
Author(s):  
Ahmed Yehia Mady ◽  
Evgeny Shein
Keyword(s):  
Organic Matter ◽  
Thermal Diffusivity ◽  
Water Content ◽  
Bulk Density ◽  
Nonlinear Regression ◽  
Quadratic Equation ◽  
Soil Physical Properties ◽  
Pedotransfer Functions ◽  
Soil Thermal Diffusivity ◽  
Exponential Equations

Background and Objective:Pedotransfer Functions (PTFs) are widely used for estimating soil thermal diffusivity. Some attempts have been made to indirectly predict soil thermal diffusivity from the easy available fundamental soil physics properties. The aim of the work was to validate usage PTFs with Nonlinear Regression (NLR) for estimating soil thermal diffusivity (KD), moreover was to select the best predictor variables used for determination of PTFs.Materials and Methods:Soil thermal diffusivity was measured at different values of water content using Kondratieff method. The parameters of the quadratic equation, which described the relation between thermal diffusivity and water content, were determined by the fitting curve and using PTFs (exponential equations) based on soil physical properties. The Combination of different soil physical properties used as PTF model’s independent variables was tested. Three classes of PTFs were proposed using NLR to estimate KDwere: KDPTF-1 (Sand+ Silt+ Clay), KDPTF-2 (Sand+ Silt+ Clay + Bulk density), and KDPTF-3 (Sand+ Silt+ Clay+ Bulk density + Organic matter).Results:The best class of PTF could be used for calculating the parameters of the quadratic equation and soil thermal diffusivity, was KDPTF-1 which taking into account the percentage of sand, silt and clay, RMSE=2.94×10-8m2/s, and GMER =1.05.Conclusion:The quadratic and exponential equations were representing the nonlinear regression equations, which could be used for estimating soil thermal diffusivity at different values of water content from easily available data on soil texture, bulk density, and organic matter content.

Effects of wave disturbance and substrate slope on sediment characteristics in the littoral zone of small lakes

1998 ◽  
Vol 55 (4) ◽  
pp. 967-976 ◽  
Author(s):  
Hélène Cyr
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Littoral Zone ◽  
Organic Matter Content ◽  
Organic Content ◽  
Matter Content ◽  
Sediment Characteristics ◽  
Small Lakes ◽  
Large Lakes ◽  
Fine Sediments

Sediment characteristics in the littoral zone of lakes affect the distribution, biomass, and productivity of benthic organisms and affect chemical exchanges with the water column, yet we know very little about their distribution. I tested whether sediment water and organic matter content were related to site exposure and to basin morphology by comparing sediments along 12 transects in three small lakes (area <150 ha). The distribution of sediment water content in small lakes differed from the general patterns described for large lakes and ocean. Sediment water content was generally high in shallow waters (<2-5 m), decreased sharply to 30-50% within 20 m from shore, and increased again in the deeper portion of the littoral zone. Fine sediments were retained in the shallow littoral zone (<1.5 m) at sites with mean fetch <150 m. The maximum depth at which sediments were mixed increased with increasing depth of the wave-mixed layer and with increasing slope of the substrate. The organic matter content (OM) of littoral sediments was closely related to their water content (WC) (log(OM) = -4.7 + 3.0 log(WC), r2 = 0.77, P < 0.001), and sediment organic content was very similar in the upper and lower portions of the littoral zone.

Physical quality of a Luvisol under agroforestry systems in a semi-arid region, Brazil

Soil Research ◽  
2016 ◽  
Vol 54 (4) ◽  
pp. 430 ◽  
Author(s):  
Rafaela Watanabe ◽  
Getulio Coutinho Figueiredo ◽  
Alvaro Pires da Silva ◽  
Júlio César Lima Neves ◽  
Teógenes Senna de Oliveira
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Bulk Density ◽  
Agroforestry Systems ◽  
Organic C ◽  
Physical Quality ◽  
Consolidation Pressure ◽  
Critical Water Content ◽  
Semi Arid

Agroforestry systems provide many environmental benefits in semi-arid regions; however, trampling by cattle, and agricultural practices, can degrade physical quality of the soil. The aim of this study was to evaluate the degree of compaction and the compression behaviour of a Luvisol after 14 years under agro-silvopastoral (ASP) and silvopastoral systems (SILV), compared with a soil under natural vegetation (NV). We evaluated the degree of soil compactness, compaction index, pre-consolidation pressure, maximum bulk density, critical water content and the stocks of total organic carbon (C), organic matter (OM), C in light organic matter (LOM), and nitrogen (N) in LOM. The results indicated that agroforestry systems change the compressive behaviour of the soil, increasing maximum bulk density (P < 0.05) and reducing critical water content (P < 0.05). Despite the increases in maximum bulk density, changes induced by agroforestry system did not affect the pore space, as shown by similar values for degree of compactness (P > 0.05) under ASP, SILV and NV. This suggests a change in the quality of OM, as evidenced by the lower values for stocks of N in LOM (P < 0.10) and total organic C (P < 0.05) under ASP and SILV, whereas pre-consolidation pressure was unaffected (P > 0.05). After 14 years, the degree of compactness and load-bearing capacity of the soils under ASP and SILV had not increased, being suitable for plant growth.

The relations between soil water retention characteristics, particle size distributions, bulk densities and calcium carbonate contents for Danish soils

2005 ◽  
Vol 36 (3) ◽  
pp. 235-244 ◽  
Author(s):  
Niels Henrik Jensen ◽  
Thomas Balstrøm ◽  
Henrik Breuning-Madsen
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Particle Size Distribution ◽  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Soil Water Content ◽  
Pressure Head ◽  
Pedotransfer Functions ◽  
Regression Equations

A database containing about 800 soil profiles located in a 7-km grid covering Denmark has been used to develop a set of regression equations of soil water content at pressure heads −1, −10, −100 and −1500 kPa versus particle size distribution, organic matter, CaCO3 and bulk density. One purpose was to elaborate equations based on soil parameters available in the Danish Soil Classification's texture database of particle size distribution and organic matter. It was also tested to see if inclusion of bulk density or CaCO3 content (in CaCO3-containing samples) as predictors or grouping in surface and subsurface horizons or textural classes improved the regression equations. Compared to existing Danish equations based on much fewer observations the accuracies of the new equations were better. The equations also predicted the soil water content at the measured pressure heads more accurately than the pedotransfer functions developed in HYPRES (Hydraulic Properties of European Soils). Introducing bulk density as a predictor improved the equation for the pressure head of −1 kPa but not for the lower ones. The grouping of data sets in surface and subsurface horizons or in textural classes did not improve the equations. Based on the equations a set of van Genuchten parameters for soil types in the Danish Soil Classification was elaborated. The prediction of soil water content, especially at pressure head −1 kPa, is more accurate using these van Genuchten parameters than using the pedotransfer functions developed in relation to the HYPRES database from a broad range of European soils.

Soil properties influencing compactability of forest soils in British Columbia

2004 ◽  
Vol 84 (2) ◽  
pp. 219-226 ◽  
Author(s):  
M. Krzic ◽  
C. E. Bulmer ◽  
F. Teste ◽  
L. Dampier ◽  
S. Rahman
Keyword(s):  
British Columbia ◽  
Organic Matter ◽  
Water Content ◽  
Bulk Density ◽  
Forest Soils ◽  
Tree Planting ◽  
Total Carbon ◽  
Regression Equations ◽  
Wide Range ◽  
Proctor Test

The widespread use of heavy machinery during harvesting and site preparation in timber plantations in British Columbia (BC) has led to concerns that compaction causes a reduction in long-term soil productivity. Impacts of properties such as total C, water content, and texture on compactability of forest soils in BC were assessed. Two compactability indices were used: maximum bulk density (MBD) and susceptibility to compaction (SC) determined by the standard Proctor test. Soil samples were collected from 16 sites throughout BC covering a wide range of biogeoclimatic zones. Soils varied in texture (12 to 87% sand, 9 to 76% silt, and 2 to 53% clay) and organic matter content (18 to 76 g kg-1 total C). A strong negative correlation was observed between MBD and gravimetric water content at which MBD was achieved (WMBD) and between MBD and total C. Similarly, WMBD and total C had strong effects on SC. The estimation of either MBD or SC values was not substantially improved by including texture parameters to the regression equations in addition to the total C. The implication of the relationships observed in this study is that increases in soil organic matter reduce the risk of compactability, which is particularly important for forest soils where compaction is generally not corrected by implements after tree planting. The information is also useful for assessing the extent of compaction on soils affected by machine traffic. Key words: Soil compaction, Susceptibility to compaction, maximum bulk density, Proctor test, total carbon

Larval habitats of common Culicoides Latreille (Diptera, Ceratopogonidae) in Kenya

1976 ◽  
Vol 66 (3) ◽  
pp. 421-425 ◽  
Author(s):  
R. Lubega ◽  
C. P. M. Khamala
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Organic Content ◽  
Immature Stages ◽  
Larval Habitats ◽  
Breeding Habitats ◽  
General Systems ◽  
Emergence Traps ◽  
Species Preferences ◽  
High Organic Content

AbstractThe larval habitats of Culicoides species were determined by examining a total of 1 476 samples collected from different ecological environments in various parts of Kenya. Immature stages were collected from suspected breeding habitats and adults were reared. Adults were also captured in emergence traps and then identified. To determine species preferences, if any, the materials yielding Culicoides were analysed for pH, organic matter and water content.Fifty-seven percent of the samples yielded a total of 26 species of Culicoides. Sites in which Culicoides occurred were classified into eleven habitats grouped into four major systems, namely, aquatic, transitional, terrestrial and general systems. Most species were found breeding over a wide pH range in sites which were wet at least part of the time. A few species appeared to select breeding habitats with a high organic content.

scholarly journals Response of Kostiakov-Lewis Infiltration Parameters to Soil Physical-Chemical Properties in the Loess Plateau of China

2020 ◽  
Vol 71 (4) ◽  
pp. 581-593
Author(s):  
Wenjing Qin ◽  
Guisheng Fan
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Bulk Density ◽  
Loess Plateau ◽  
Chemical Properties ◽  
Sand Content ◽  
The Loess Plateau ◽  
Silt Content ◽  
Main Factors ◽  
Infiltration Parameters

In order to know the main factors influence the infiltration parameters, based on the 344 sets of double-ring infiltration experiments in 101 different experimental sites in the Loess Plateau, obtained a large sample of Kostiakov-Lewis infiltration model parameters, analyzed the relationship between infiltration parameters and soil properties, established a multiple linear model, a nonlinear model and a BP neural network model to predict the infiltration parameters. The results showed that through Pearson correlation analysis, the main factors for parameter k was bulk density, soil water content of 0-10 cm, sand content, silt content and organic matter of 0-20 cm, the main factors influence parameter α was water content, sand content, silt content of 0-40 cm, and bulk density of 20-40 cm, and the main factors for parameter f0 was water content, sand content, silt content, of 0-40 cm, bulk density of 10-40 cm, and organic matter of 0-20 cm. Compared with previous studies, this paper added soil organic matter content as an independent variable to study the effect of soil chemical properties on soil infiltration capacity, which makes the model more reasonable, higher accuracy, and better prediction effect. Based on the effective test, result error analysis and comprehensive analysis, it was feasible to obtain the infiltration parameters in the Kostiakov-Lewis model using three Pedo-transfer functions. Under the condition of comprehensive consideration of forecast accuracy and stability applicability, it was recommended to use the nonlinear model as the prediction model of soil water infiltration parameters in the Loess Plateau.

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