Accumulation In Soil Layers Research Articles

Carbon accumulation in soil layers under degraded, intact and planted forest cover types in tropical semi-deciduous and moist evergreen forests

Carbon accumulation in soil layers under degraded, intact and planted forest cover types in tropical semi-deciduous and moist evergreen forests

Soil nitrogen dynamics under tobacco with different fertilizer management in southern Brazil

Nitrogen (N) is an essential element to the constitution and metabolism of many plant components, being the most effective nutrient for improving yield and quality of tobacco (Nicotiana tabacum L.) plantations. We aimed to quantify potential N losses through leaching and volatilization and consequent tobacco yield under N fertilizer sources/management in southern Brazil. Experiments were conducted under similar conditions in four locations over three cropping seasons: 2013/2014, 2014/2015 and 2015/2016. Treatments were three N sources (urea, Chilean saltpeter and ammonium nitrate) with distinct application methods for urea (incorporated and broadcasted) plus a control (zero). N losses were quantified through ammonia (NH3) volatilization and inorganic N (nitrate and ammonium) movement down the soil profile, by tracking their concentration in soil solution and accumulation in soil layers over the tobacco growing cycles. Tobacco yield and N accumulation in leaves were annually determined. Tobacco yield was positively influenced by N fertilizer application, irrespective of the source/management used. Amongst sources, Chilean saltpeter presented the lowest NH3 emission, being the most effective in maintaining higher inorganic N in soil solution. Expressive volatilization of NH3 was observed under urea in surface application, reaching 16% of loss from fertilizer. Overall, it was detected higher concentration of nitrate and ammonium in the initial tobacco crop phase, between 20 and 50 days after transplanting. Therefore, as a practical recommendation splitting the early tobacco N rates in later applications should be considered to minimize losses through leaching and better synchronize crop demand.

Establishment of Aporrectodea longa and measurement of dung carbon incorporation in soils under permanent pasture

Earthworm populations often have a large biomass in pasture soils and can significantly accelerate the disappearance of organic matter from the soil surface and its accumulation in soil layers. This field study investigated the influence of the anecic earthworm Aporrectodea longa on bulk soil C in permanent pastures two years after their introduction. We used the approach of measuring soil C and 13C after the application of C-enriched dung to paddocks with and without established A. longa populations (∼50 m−2). At three sites with differing soil types, dung incorporation into the soil was limited, suggesting that densities were still too low to influence bulk soil C. In a fourth pasture where A. longa had been present for 23 years, and had reached a density of 190 m−2, more dung-derived C was detected to 300 mm depth in the soil profile compared with the control without A. longa.

Weathering, sedimentary and diagenetic controls of mineral and geochemical characteristics of the vertebrate-bearing Silesian Keuper

AbstractMudstones and claystones from the southern marginal area of the European Upper Triassic, midcontinental Keuper basin (Silesia, southern Poland) were investigated using XRD, organic and inorganic geochemistry, SEM, K-Ar of illite-smectite, AFT, and stable isotopes of O and C in carbonates in order to unravel the consequent phases of the geological history of these rocks, known for abundant fossils of land vertebrates, and in particular to evaluate the diagenetic overprint on the mineral composition. The detected and quantified mineral assemblage consists of quartz, calcite, dolomite, Ca-dolomite, illite, mixed-layer illite-smectite, and kaolinite as major components, plus feldspars, hematite, pyrite, chlorite, anatase, siderite, goethite as minor components. Palygorskite, gypsum, jarosite and apatite were identified in places.The K-Ar dates document a post-sedimentary thermal event, 164 Ma or younger, which resulted in partial illitization of smectite and kaolinite. The maximum palaeotemperatures were estimated from illite-smectite as ∼125°C. Apatite fission track data support this conclusion, indicating a 200–160 Ma age range of the maximum temperatures close to 120°C, followed by a prolonged period of elevated temperatures. These conclusions agree well with the available data on the Mesozoic thermal event, which yielded Pb-Zn deposits in the area. Organic maturity indicators suggest the maximum palaeotemperatures <110°C.Palygorskite was identified as authigenic by crystal morphology (TEM), and calcite by its accumulation in soil layers and by its isotopic composition evolving with time, in accordance with the sedimentary and/or climatic changes. Dolomite isotopic composition indicates more saline (concentrated) waters. Palygorskite signals a rapid local change of sedimentary conditions, correlated with algal blooms. This assemblage of authigenic minerals indicates an arid climate and the location at the transition from a distal alluvial fan to mudflat.Fe-rich smectite, kaolinite, and hematite were products of chemical weathering on the surrounding lands and are therefore mostly detrital components of the investigated rocks. Kaolinite crystal morphology and ordering indicates a short transport distance. Hematite also crystallizedin situ, in the soil horizons. A large variation in kaolinite/2:1 minerals ratio reflects hydraulic sorting, except of the Rhaetian, where it probably signals a climatic change, i.e. a shift in the weathering pattern towards kaolinite, correlated with the disappearance of hematite. Quartz, 2M1illite, and minor feldspars and Mg-chlorite were interpreted as detrital minerals. The documented sedimentation pattern indicates that in more central parts of the Keuper playa system, where an intense authigenesis of the trioctahedral clays (chlorite, swelling chlorite, corrensite, sepiolite) took place, illite and smectite were the dominant detrital clay minerals.Cr/Nb and Cr/Ti ratios were found as the best chemostratigraphic tools, allowing for the correlation of all investigated profiles. A stable decrease of these ratios up the investigated sedimentary sequence is interpreted as reflecting changes in the provenance pattern from more basic to more acidic rocks.

Water and salt movement in soil driven by crop roots: a controlled column study

AbstractWater deficit and salt accumulation in soil presents serious problems to crop production in semi-arid regions. These problems depend on the active transpiration stream and the selective absorption of ions by crop roots. In this study, a large sized soil column system was used to examine the dynamics of water and ion transport and salt accumulation in soil layers. Special reference was placed on the effects of the active and selective absorption by roots of different crops (i.e., corn plants, sunflower plants and no plants). The column system was equipped with on-line systems for the control of groundwater level. Soil water content sensors enabled time-course evaluations of the volumetric water content and hence upward flux of the groundwater in the soils at different depths. Furthermore, the distribution and accumulation of ions in soil layers, plant organs and xylem sap were analyzed using ion chromatography. In this column experiment, diurnal and longer term changes in water movement and ion accumulation in soil, affected by root absorption characteristics of plants, were evaluated quantitatively. The results demonstrated that the column system was applicable for the quantitative analysis of the effects of root absorption by different crops on water deficit and salinization in soils.

Soil ecosystem engineering by the train millipede Parafontaria laminata in a Japanese larch forest

Periodic swarming by adult train millipedes Parafontaria laminata (Attems, 1909) occurs in central Japan on an 8-year cycle, and the emergence of new adults is highly predictable. Millipede biomass reaches a maximum and feeding habits change upon the emergence of adults. Larvae are geophagous while adults feed on both litter and soil. We hypothesized that the shift in the developmental stages of P. laminata influenced the carbon dynamics in the soil and conducted a field mesocosm experiment in a larch plantation forest over 2 years (1999 and 2000) using three developmental stages: sixth- and seventh-instar larvae and adults. By experimentally manipulating millipede density at four levels, we obtained the following results: larvae were geophagous, while adults consumed both litter and soil (mixed-feeding) and consequently showed stronger density effects on litter decomposition rates than larvae; adult activities in the high-density treatment increased soil microbial biomass but not at low adult densities or at the larval stages; and adults increased the carbon accumulation in soil layers especially at high densities due to their mixed-feeding on litter and soil. We determined that due to synchronized postembryonic development with high densities and changes in feeding habits, the train millipede periodically sequestered carbon in this forest.