A. N. Gennadiyev

Soil catena formation and erosion of two Mississippian mounds at Cahokia archaeological site, Illinois

About 1000 years ago, Mississippian Indians built what are now designated Mounds 69 and 70 at Cahokia near Collinsville, Illinois. Loamy soil materials were placed on the mounds by Mississippian Indians before A.D. 1100, and the site was inhabited until approximately A.D. 1300. The general objective of this study was to determine the potential of using archaeological mounds or sites to obtain information on soil development and erosion processes. Our specific objectives were to determine: (i) the extent of soil formation during the past 900 years, (ii) the time period and extent of disturbance by human activities, including tillage and digging by treasure hunters and looters, and (iii) the erosion phase of soils on mound sideslopes and the amount of soil loss from accelerated erosion. The vegetation and distribution of organic C in soil profiles suggests there has been no tillage since the 1970s and little soil erosion of either the summit or the sideslope of Mound 69. The adjacent alluvial plain is still being cultivated. Fly ash, particulate matter resulting from high-temperature coal combustion, was used as a time marker in soil and sediment. Fly-ash distributions in the upper 20 cm of Mound 69 support the theory that cultivation occurred between the 1850s and the 1970s. Based on the fly ash data, approximately 55% of the original surface soil layer remains on the sideslope of Mound 69 (compared with the uncultivated sideslope of Mound 70). There has been substantial deposition of sediment rich in fly ash onto the footslope of Mound 69 (from the cultivated sideslope) and the toeslope of Mound 70 (from the cultivated footslope). The fly ash and organic C data for the summit soil profile on Mound 70 suggest treasure hunters and looters disarranged the soil profile completely. The uncultivated sideslope with a 23% slope had a 40-cm surface layer rich in fly ash. The fly-ash content and thickness of the footslope soil surface layer was reduced as a result of tillage and erosion from the 1850s to the 1970s. Fly ash-enriched sediment accumulated on the toeslope and created a 60-cm surface layer. The current vegetation and the decrease in organic C with depth on the footslope and toeslope of Mound 70 suggest that no tillage has occurred since the 1970s. Fly ash presence within soil layers indicates which layers have been exposed at the soil surface since the 1850s and the extent of soil mixing. Archaeological mounds with known dates of construction can be used to obtain information on soil development and erosion processes.

Impact of Land Use Change and Soil Erosion in Upper Mississippi River Valley on Soil Organic Carbon Retention and Greenhouse Gas Emissions

The dynamics of soil organic carbon (SOC) are affected by many factors including land use, management history, soil type, climate, and soil landscape processes. The primary objective of this research was to compare the storage of SOC on sloping woodland and cropland landscapes of northwestern Illinois. The cropland area was cultivated using a moldboard plow system for 125 years, and then the primary tillage was changed to chisel plow for the last 25 years. The woodland area was never cleared or cultivated. The SOC concentrations of various soil layers, to a depth of 0.5 m, were measured. The woodland landscape had significantly higher SOC in the surface layers on all landscape segments than at the cultivated site. For both land uses, the subsurface layers had similar SOC levels. Results suggested that the cropland landscape retained 52% of the total SOC on a volumetric basis during the last 150 years of cultivation, soil erosion, and agricultural use. The other 48% of the SOC was either deposited in the water or released to the atmosphere. Results suggest that if mesic-frigid temperature line moved north because of climate change, then the current uncultivated forest soils would be used for cropland, and additional SOC will be released to either the stream or atmosphere and not maintained in soil even with a chisel plow system.

Comparative assessment of the contents of magnetic spherules, 137Cs, and 210Pb in soils as applied for the estimation of soil erosion

The contents of magnetic spherules and 137Cs and 210Pb isotopes were determined in gray forest soils of the Novosil Agroforest Experimental Station in Orel oblast (central part of European Russia). The spatial variability in the contents of these substances was studied, and their distribution in the soil profiles and along soil transects within the afforested and cultivated slopes was analyzed. Factors and processes favoring the accumulation of magnetic spherules and 137Cs and 210Pb isotopes in the soils, as well as their removal from the soils, were revealed. Similarities and distinctions in the patterns of their behavior were interpreted. Prospects for the combined use of these three tracers to estimate the rates of soil erosion and sediment deposition on the soil surface were tested.

Short-range variation in a Wisconsin soilscape (USA)

Here we report on the variation of a soilscape in south central Wisconsin, USA. The variation in soil properties and soil features results in four soil order (Entisols, Inceptisols, Alfisols and Mollisols). Observations were made along a 200 m transect in a field that was cultivated since 1870. Slopes ranged from 7.5% on the back slope to 0% in the lower part. The soilscape had a total relief difference of 7.0 m. The soils were studied by 41 soil pits (60 cm), 6 soil pits (125 cm), 15 soil augers (100 cm), and ground-penetrating radar imagery. The summit and shoulder consist of coarse glacial outwash (loamy sands) over limestone whereas the lower part is lacustrine sediments over coarse outwash (loams, silty loams). The A-horizon thickness ranged from 14 to 52 cm with thick A horizons at the toeslope that also had the lowest soil pH. The soil organic carbon (SOC) contents of the A horizons ranged from 11.6 to 46.9 g C kg–1, and the higher contents are in the lower part of the soilscape. SOC stocks (0–20 cm depth) ranged from 50 to 70 Mg C ha–1 on the summit and backslope, but were 80 to 95 Mg C ha–1 in the flat part of the soilscape. The lowest soybean yields (1.6 Mg ha–1) were found at the summit and the highest yield (6.3 Mg ha–1) at the lower end of the backslope. Soybean yields were correlated to the thickness of the A horizon, and every 10 cm increase in A horizon thickness yielded an extra 0.6 Mg soybeans ha–1. Analysis of spherical magnetic particles was used to estimate soil erosion rates that were highest on the backslope (16.2 Mg ha–1 yr–1) and rates of soil deposition in the lowest part of the soilscape was 18.8 Mg haP1 yr–1. It seems that there is no net soil and SOC loss within this soilscape. All in all, we found 4 soil taxonomic orders within 200 m. The variation in this soilscape was substantial and probably enhanced by 140 years of cultivation.