Decrease In Organic Matter Research Articles

Rill Erosion Due to Wildfire or Deforestation in Forestlands of Northern Iran

Rill erosion, mostly affecting steep and long hillslopes, is one of the most severe effects of deforestation and wildfires in natural ecosystems. Specific monitoring and accurate but simple models are needed to assess the impacts of these forest disturbances on the rill detachment process. To address this need, this study has simulated the rill detachment capacity (Dc) through flume experiments on samples of soils collected in hillslopes after deforestation and severe burning. The associations between Dc and organic matter (OM) and the aggregate stability of soil (WSA), two key parameters influencing the rill detachment process, have also been explored under the two soil conditions (deforested and burned soils) using multivariate statistical techniques. Finally, linear regression models to predict Dc from these soil parameters or the hydraulic and morphological variables (water flow rate, WFR, and soil slope, S), set in the flume experiments, have been proposed for both soil conditions. Higher Dc in samples from deforested sites compared to the burned soils (+35%) was measured. This Dc increase was associated with parallel decreases in OM (−15%) and WSA (−34%) after deforestation compared to the wildfire-affected sites. However, the discrimination in those soil properties between the two soil conditions was not sharp. Accurate linear equations (r2 > 0.76) interpolating Dc and the shear stress (τ) have been set to estimate the rill erodibility (Kr) to evaluate soil resistance in erosion models to be applied in deforested or burned sites.

The Paleoenvironment and Mechanisms of Organic Matter Enrichment of Shale in the Permian Taiyuan and Shanxi Formations in the Southern North China Basin

The organic-rich shale of the Permian Taiyuan Formation (TYF) and Shanxi Formation (SXF) in the Southern North China Basin (SNCB) is considered a potential shale gas source. The shale was formed in a marine-continental transitional sedimentary environment, which has rarely been studied, with the enrichment mechanisms of organic matter (OM) remaining unclear. This study investigated the controlling factors and enrichment mechanisms of OM by analyzing the total organic carbon (TOC) content, paleoclimate, paleoproductivity, sedimentation rate, redox, and paleosalinity. The TOC of the TYF ranged from 0.92 to 7.43 wt.%, with an average of 2.48 wt.%, which was higher than that of the SXF (TOC = 0.36–5.1 wt.%, average of 1.68 wt.%). These geochemical indices suggest that both the TYF and SXF were deposited in warm and humid paleoclimates, with relatively high biological productivity and sedimentation rates. During the deposition process, the TYF experienced frequent transgression and regression events, leading to an enhancement of water reducibility, a relatively high sedimentation rate, reduced OM oxidation, and rapid deposition of OM, which were conducive to the preservation of OM. Moreover, a high biological productivity increased respiratory oxygen consumption in the water column, which could lead to OM accumulation. However, the regression event experienced by the SXF reduced the paleoproductivity and sedimentation rate and increased water oxidation, leading to a decrease in OM. The main controlling factors for the enrichment of OM in the TYF and SXF were the sedimentation rate, paleoproductivity, and redox conditions, thus establishing the enrichment models for OM in the TYF and SXF. This study is conducive to understanding shale enrichment mechanisms and guiding shale gas exploration.

Imbalanced Nutrient Accumulation in the Coastal Soils Induced by Salinity Intrusion

Salinity intrusion worldwide is a problem of consideration for the global food production and ensuring food security. In this investigation, we focused to find out the key chemical elements for this salinity problem. In this paper, the authors reported the high accumulation of sodium (Na + ) and increased EC (6.9 dS/m) values than that of the previous year (4.67 dS/m). We found the highest EC, Na +, and ESP of 6.9 ds/m, 2.6 meq/100 g of soil, and 19.1%, respectively at Dumki, Potuakhali. The highest increase of exchangeable Na + was found in Tojumuddin, Bhola. The result is 55% more when compared to the previous investigated result. Contrary to the Na + increase, we found an 84-91% decrease of the organic matter (OM) in the investigated samples. The excessive increase of exchangeable Na + and decrease of OM in this investigation indicate the salinity intrusion and low nutrient content in the coastal soils of Bangladesh.

Imbalanced Nutrient Accumulation in the Coastal Soils Induced by Salinity Intrusion

Salinity intrusion worldwide is a problem of consideration for the global food production and ensuring food security. In this investigation, we focused to find out the key chemical elements for this salinity problem. In this paper, the authors reported the high accumulation of sodium (Na + ) and increased EC (6.9 dS/m) values than that of the previous year (4.67 dS/m). We found the highest EC, Na +, and ESP of 6.9 ds/m, 2.6 meq/100 g of soil, and 19.1%, respectively at Dumki, Potuakhali. The highest increase of exchangeable Na + was found in Tojumuddin, Bhola. The result is 55% more when compared to the previous investigated result. Contrary to the Na + increase, we found an 84-91% decrease of the organic matter (OM) in the investigated samples. The excessive increase of exchangeable Na + and decrease of OM in this investigation indicate the salinity intrusion and low nutrient content in the coastal soils of Bangladesh.

A 16,000-yr-long sedimentary sequence from Lakes Peters and Schrader (Neruokpuk Lakes), northeastern Brooks Range, Alaska

AbstractSediments that accumulate in high-latitude lakes serve as valuable environmental archives of changing conditions in a region currently undergoing rapid change. A previously unexplored sedimentary sequence reaching back 16,000 years from Lakes Peters and Schrader (Neruokpuk Lakes) in the northeastern Brooks Range (69°N), Alaska, shows distinct changes in accumulation rates and biophysical properties including bulk density (BD), organic matter (OM) content, and grain-size distribution at five widely distributed core sites. The oldest sediments contain little OM and accumulated rapidly as glaciers retreated around 15 ka. OM peaked between 12 and 10 ka along with Northern Hemisphere summer insolation. BD increased and OM decreased until around 5 ka, possibly reflecting a decrease in river-transported terrestrial OM. From 5–2 ka, OM consistently increased, suggesting a rise in river discharge, or a rise in summer temperatures, which led to higher productivity, or both. After 2 ka, sediments increased in BD and decreased in OM, suggesting glacier growth. Evidence for glacier expansion late during the Little Ice Age is weak, but increased sedimentation rates may reflect glacier retreat during the last century. This study provides a framework for future paleoenvironmental research of a rare archive in a relatively pristine Arctic setting.

Transformation of terrestrial organic matter along thermokarst-affected permafrost coasts in the Arctic.

The changing climate in the Arctic has a profound impact on permafrost coasts, which are subject to intensified thermokarst formation and erosion. Consequently, terrestrial organic matter (OM) is mobilized and transported into the nearshore zone. Yet, little is known about the fate of mobilized OM before and after entering the ocean. In this study we investigated a retrogressive thaw slump (RTS) on Qikiqtaruk - Herschel Island (Yukon coast, Canada). The RTS was classified into an undisturbed, a disturbed (thermokarst-affected) and a nearshore zone and sampled systematically along transects. Samples were analyzed for total and dissolved organic carbon and nitrogen (TOC, DOC, TN, DN), stable carbon isotopes (δ13C-TOC, δ13C-DOC), and dissolved inorganic nitrogen (DIN), which were compared between the zones. C/N-ratios, δ13C signatures, and ammonium (NH4-N) concentrations were used as indicators for OM degradation along with biomarkers (n-alkanes, n-fatty acids, n-alcohols). Our results show that OM significantly decreases after disturbance with a TOC and DOC loss of 77 and 55% and a TN and DN loss of 53 and 48%, respectively. C/N-ratios decrease significantly, whereas NH4-N concentrations slightly increase in freshly thawed material. In the nearshore zone, OM contents are comparable to the disturbed zone. We suggest that the strong decrease in OM is caused by initial dilution with melted massive ice and immediate offshore transport via the thaw stream. In the mudpool and thaw stream, OM is subject to degradation, whereas in the slump floor the nitrogen decrease is caused by recolonizing vegetation. Within the nearshore zone of the ocean, heavier portions of OM are directly buried in marine sediments close to shore. We conclude that RTS have profound impacts on coastal environments in the Arctic. They mobilize nutrients from permafrost, substantially decrease OM contents and provide fresh water and nutrients at a point source.

Evaluation of soil degradation produced by rice crop systems in a Vertisol, using a soil quality index

One of the priorities of land planners is the development of methodologies that allow the detection of negative impacts on soils. The objective of this work was to evaluate the impact of rice production systems that use irrigation with groundwater on soil at the field scale, using a soil quality index. Six soil quality indicators (SQI) corresponding to different soil properties were measured: aggregate stability, water percolation, soil organic matter (OM), exchangeable sodium content (ESC), pH, and electrical conductivity in saturated paste extract. Data was collected in 75 sampling sites, setting reference values and threshold values for each SQI. The indicators were standardized and 5 soil quality categories were defined: very low, low, moderate, high and very high. The impact of rice crop on soil quality was analyzed in 6 field plots with different crop rotations using this SQIn. A negative effect on soils structure was observed with the introduction of rice in the crop rotation. This effect was attributed to a decrease in OM and an increase of ESC resulting from the use of water for irrigation rich in sodium bicarbonate. Soil management should promote activities that help to increase organic matter in the soil, and to reduce the amount of Na in the exchangeable complex. The use of a SQIn can provide an early assessment of soil degradation processes and help land managers to implement soil conservation practices.

Lateglacial and Holocene climate, disturbance and permafrost peatland dynamics on the Seward Peninsula, western Alaska

Northern peatlands have accumulated large carbon (C) stocks, acting as a long-term atmospheric C sink since the last deglaciation. How these C-rich ecosystems will respond to future climate change, however, is still poorly understood. Furthermore, many northern peatlands exist in regions underlain by permafrost, adding to the challenge of projecting C balance under changing climate and permafrost dynamics. In this study, we used a paleoecological approach to examine the effect of past climates and local disturbances on vegetation and C accumulation at a peatland complex on the southern Seward Peninsula, Alaska over the past ∼15 ka (1 ka = 1000 cal yr BP). We analyzed two cores about 30 m apart, NL10-1 (from a permafrost peat plateau) and NL10-2 (from an adjacent thermokarst collapse-scar bog), for peat organic matter (OM), C accumulation rates, macrofossil, pollen and grain size analysis.A wet rich fen occurred during the initial stages of peatland development at the thermokarst site (NL10-2). The presence of tree pollen from Picea spp. and Larix laricinia at 13.5–12.1 ka indicates a warm regional climate, corresponding with the well-documented Bølling–Allerød warm period. A cold and dry climate interval at 12.1–11.1 ka is indicated by the disappearance of tree pollen and increase in Poaceae pollen and an increase in woody material, likely representing a local expression of the Younger Dryas (YD) event. Following the YD, the warm Holocene Thermal Maximum (HTM) is characterized by the presence of Populus pollen, while the presence of Sphagnum spp. and increased C accumulation rates suggest high peatland productivity under a warm climate. Toward the end of the HTM and throughout the mid-Holocene a wet climate-induced several major flooding disturbance events at 10 ka, 8.1 ka, 6 ka, 5.4 ka and 4.7 ka, as evidenced by decreases in OM, and increases in coarse sand abundance and aquatic fossils (algae Chara and water fleas Daphnia). The initial peatland at permafrost site (NL10-1) is characterized by rapid C accumulation (66 g C m−2 yr−1), high OM content and a peak in Sphagnum spp. at 5.8–4.6 ka, suggesting the lack of permafrost. A transition to extremely low C accumulation rates of 6.3 g C m−2 yr−1 after 4.5 ka at this site suggests the onset of permafrost aggradation, likely in response to Neoglacial climate cooling as documented across the circum-Arctic region. A similar decrease in C accumulation rates also occurred at non-permafrost site NL10-2. Time-weighted C accumulation rates are 21.8 g C m−2 yr−1 for core NL10-1 during the last ∼6.5 ka and 14.8 g C m−2 yr−1 for core NL10-2 during the last ∼15 ka. Evidence from peat-core analysis and historical aerial photographs shows an abrupt increase in Sphagnum spp. and decrease in area of thermokarst lakes over the last century, suggesting major changes in hydrology and ecosystem structure, likely due to recent climate warming.Our results show that the thermokarst–permafrost complex was much more dynamic with high C accumulation rates under warmer climates in the past, while permafrost was stabilized and C accumulation slowed down following the Neoglacial cooling in the late Holocene. Furthermore, permafrost presence at local scales is controlled by both regional climate and site-specific factors, highlighting the challenge in projecting responses of permafrost peatlands and their C dynamics to future climate change.

Bio-Remediation and Physicochemical Interaction of Experimentally Contaminated Soils in Uganda with Diesel

This study was conducted for a period of 4 weeks to monitor and evaluate the process of bio-stimulation and natural recovery rates in terms of bacteria and fungi communities to diesel contaminated soils. In this study, laboratory experiments were conducted to measure pH, moisture content, Potassium (K), Phosphorous (P), Organic Nitrogen (ON), Organic Carbon (OC), Organic Matter (OM), fungi and bacteria cells before and after soils were intentionally contaminated with diesel. The results of this study showed that treatment level, K, P and pH have a positive effect on the number of bacterial cells whereas moisture content, sand and clay particles impact negatively. A correlation coefficient of R 2 = -0.93 was obtained between time and OC, OM, ON while OC, OM, ON and bacteria showed an R 2 = -0.58. Three conclusions can be drawn based on this study. One, by week 4, bacterial cells counts had doubled. Two, by week 4, bacterial counts numerically outnumbered fungal cells. Three, the increase in both bacterial and fungal cells was accompanied with a decrease in OM, OC and ON. This means that both bacterial and fungal cells had adapted by week 4.

Phytotoxicity and speciation of copper, zinc and lead during the aerobic composting of sewage sludge

The content and speciation of heavy metals in composted sewage sludge is the main cause of negative impacts on environment and health of animal and human. An aerobic composting procedure was conducted to investigate the influences of some key parameters on phytotoxicity and speciation of Cu, Zn and Pb during sewage sludge composting. The pH value reached the optimal range for development of microorganisms, and content of organic matter (OM) and dissolved organic carbon (DOC) decreased with the composting age. The total amounts of Cu, Zn and Pb were much lower in the final compost. The results from sequential extraction procedure of heavy metals showed that composting process changed the distribution of five fractions of Cu, Zn and Pb, and reduced the total contents and sum percentages of four mobile fractions (exchangeable (EXCH), carbonate (CAR), reducible iron and manganese (FeMnOX), and organic matter bound (OMB)), indicating that the metal mobility and phytotoxicity decreased after aerobic composting. The seed germination and root growth of Pakchoi ( Brassica Chinensis L.) were enhanced with composting age and reached the highest value at the end of compost. The decrease of OM and DOC was significantly correlated to changes of metal distribution and germination index (GI) of Pakchoi. Only for Cu in the compost, the GI could be predictable from the sum mobile metal fractions (EXCH + CAR + FeMnOX + OMB) ( R = −0.814 *). For Zn and Pb, R value was significantly increased by use of other components, such as pH, OM and DOC, which suggested that the transformation of heavy metal speciation and phytotoxicity of sewage sludge during an aerobic composting was rather strongly dependent on multiple components than a single element.

In vivo digestibility of different types of forages using sheep as a model of ruminants

Digestibility of a forage is very important as it contributes to the energy and protein values and intakepotential of the feed in ruminant production systems. The silages used in this digestibility trial present therange of variation encountered in practice of forages used within Finland: early cut grass (EG), late cutgrass (LG), red clover (Trifolium pratense, RC) and whole-crop barley (Hordeum vulgare, WCB). Grasssilages were a mixture of timothy (Phleum pretense) and meadow fescue (Festuca pratensis). EG, LG,RC and WCB were cut on 13 June (2006), 3 July (2006), 29 June (2006) and 2 August (2006),respectively. Grass and clover silages were wilted for 1 day and all silages were ensiled with AIV 2, andensiled in round bales. Four rams (Dorset and Finnsheep × Texel crossbred) were used to estimatedigestibility in a 4 × 4 Latin square experiment with four 3-week experimental periods. The totaldigestibility was determined using total collection method by measuring daily forage intake and theamount of faeces excreted over the last 7 days of each period.All silages were well preserved and had relatively high DM concentration, within 395 - 566 g/kg.The ash concentration in EG, LG, RC and WCB was 88, 70, 97 and 62 g/kg DM. The respective CPconcentrations were 180, 113, 163, 71 g/kg DM and NDF concentrations were 509, 623, 385and 548 (g/kgDM).The organic matter digestibility for EG, LG, RC and WCB was 0.751, 0.608, 0.645 and 0.618.There was a 20 day difference in the cutting dates of EG and LG resulting in 0.008 unit decrease inorganic matter digestibility per day. Neutral detergent fibre digestibility was highest for early cut grasssilage (0.74). and lowest for red clover (0.50) and whole-crop barley (0.51).Forages vary greatly in their digestibility depending on species and maturity as shown by theresults of the current study. The great variation emphasizes the importance of accurate routine digestibilityanalysis and need to analyze farm silages for ration formulation.

Biochemical ripening of dredged sediments. Part 1. Kinetics of biological organic matter mineralization and chemical sulfur oxidation

After dredged sediments have settled in a temporary upland disposal site, ripening starts, which turns waterlogged sediment into aerated soil. Aerobic biological mineralization of organic matter (OM) and chemical oxidation of reduced sulfur compounds are the major biochemical ripening processes. Quantitative data describing these processes are scarce. Therefore, aerobic oxidation and mineralization of five previously anaerobic dredged sediments were studied during a 160-d laboratory incubation experiment at 30 degrees C. A double exponential decay model could adequately describe sulfur oxidation and OM mineralization kinetics. During the first 7 d of incubation, 23 to 80% of the total sulfur was oxidized, after which no further sulfur oxidation was observed. Oxygen used for sulfur oxidation amounted up to 95% of the total oxygen uptake in the first 7 d and up to 45% of the oxygen uptake during the entire incubation period. Mineralization rates of the rapidly mineralizable OM fractions that degraded during the first 14 to 28 d of incubation were 10(2) to 10(3) times higher than the mineralization rates of the slowly mineralizable OM during the remaining period. First-order mineralization rates of the slowly mineralizable OM were 0.22 x 10(-3) to 0.54 x 10(-3) d(-1) and can be compared with those of terrestrial soils. Yields of biomass on substrate ranged from 0.08 to 0.45 g C(biomass)/g C(OM) and appeared to be higher for rapidly mineralizing OM than for slowly mineralizing OM. The results of this study can be used to optimize conditions during temporary disposal of sediments, to estimate the potential decrease in OM, and for future studies on the possible link between OM mineralization and degradation of hydrophobic organic contaminants.

Digestibility and nitrogen retention of diets containing different levels of fibre in local (Mong Cai), F1 (Mong Cai × Yorkshire) and exotic (Landrace × Yorkshire) growing pigs in Vietnam

Total tract digestibility and nitrogen retention of three diets containing different levels of fibre [200, 260 and 320 g/kg neutral detergent fibre (NDF) in dry matter] were determined in three breeds of growing pig at an initial age of approximately 3.5 months. The breeds were local (Mong Cai, MC), F1 crossbred (MC x Yorkshire) and exotic (Landrace x Yorkshire, LY), allocated at random within breed (block) to double 3 x 3 Latin squares. The main fibrous ingredients of the experimental diets were rice bran, cassava residue meal and non-dehulled groundnut cake meal. Digestibility of organic matter (OM), crude protein (CP), NDF, crude fibre, gross energy (GE) and ether extract (EE) decreased as the level of dietary NDF increased (p < 0.001). The r(2) values for the relationship between NDF level and digestibility of OM, CP, GE and EE were 83%, 83%, 80% and 82% respectively. On average, an increase in NDF content of 1% unit resulted in a decrease in OM, CP, GE and EE digestibility of 0.67%, 0.75%, 0.50% and 0.42% units respectively. Digestibility of energy and nutrients was the highest for MC and the lowest for LY (p < 0.01), with intermediate values for F1. There was a negative effect of NDF level on nitrogen (N) retained as a proportion of intake (p < 0.05). Nitrogen retention and utilization were significantly higher (p < 0.001) for LY than for MC and F1 pigs.

Effects of different land-use types on soil quality in the hilly area of Rawalakot Azad Jammu and Kashmir

Vegetative cover plays an important role for the quality of soil especially in hilly and mountainous areas such as Azad Jammu and Kashmir where erosion is a major threat to the ecosystem and productivity. The study focuses on the impact of land-use types on soil quality by measuring the differences in chemical and physical properties at three sites in adjacently located natural forest land (forest), fallow grassland (grass) and arable land (arable). Soil samples from 0-15 and 15-30 cm depth were collected and examined for particle distribution, dry bulk density, organic matter (OM), pH, macro- and micro-nutrients. Land-use types had a significant effect on primary soil particle distribution. Highest clay content was found in forest and highest sand content in arable. Forest had relatively the highest levels of OM, macro- and micro-nutrients and arable the lowest. Most of the properties of the 0-15 cm surface level of grass were similar to those observed in the 15-30 cm level in forest. Arable exhibited lowest nutrient status and poorest physical conditions, indicating a degrading effect of arable cultivation practices on soil. Grass and arable showed, compared to forest, a 30–60% average increase in bulk density and 26–66% average decrease in OM. Regression analysis showed a significant correlation of OM with available phosphorus and potassium while it had negative correlation with dry bulk density and pH. Natural vegetation appeared to be a main contributor of soil quality as it maintained the organic carbon stock, and increased the nutrient status of soil and is therefore important for sustainable development of Azad Jammu and Kashmir and other similar areas. Furthermore, OM was shown to be an important indicator of soil quality.