Methodology for the Diagnostics of Soil Polygenesis on the Basis of Macro-and Micromorphological Studies

A methodology for studying soil polygenesis and lithological homogeneity of soil profiles is suggested. This methodology is particularly important for mountain soils, where the lithological heterogeneity of the soil profiles created by denudation and accumulation processes is often observed. The methodology includes several stages: (a) the study of the lithological homogeneity/ heterogeneity of soil profiles by field and laboratory methods, (b) the stage-by-stage macro-, meso-, micro-, and submicromorphological analyses of soil profiles with additional use of the methods of neighboring sciences, and (c) the subdivision of soil features into the groups of recent and inherited (relict) features. In the latter group, the subgroups of lithorelict features inherited from the parent material and pedorelict features inherited from the previous stages of soil formation can be distinguished. Two major models of soil polygenesis are suggested. Simple models describe the soils, in which new features appear due to the changes in the environmental conditions in the course of soil evolution. Complex models describe the soils, in which such changes are combined with deposition of new portions of sediments onto the soil surface with the development of buried soil horizons (the synlithogenic pedogenesis). The models of continuous and discontinuous synlithogenic pedogenesis can be further distinguished. It is argued that the micromorphological method applied to the studies on soil microfabrics, microforms of soil humus, soil porosity, coatings, and various pedo-and lithorelict features yields valuable information on polygenetic soils.

Changes in Environmental Parameters and Their Impact on Forest Growth in Northern Eurasia

We performed an empirical investigation of forest growth for two types of forests in northern Eurasia (larches and spruces) in order to show that the sensitivity of trees to the variable climate and geomagnetic field can be seen even under the large-scale average. The main purpose of this research was to model a forest growth rate V for each forest type on the basis of several environmental parameters influencing the tree growth in a high degree and to find the differences and similarities of the larches and spruces’ response to changing environment. We showed that V, which is related to the annual tree-ring width, could be derived from the Normalized Difference Vegetation Index (NDVI) data. Averaged yearly by species for 1982-2006, it displayed a long-term decrease (most likely related to the global climate change) as well as short-term variations with periods of 2.2, 4 and 8 years. A composite function method was used for modeling. We selected several tree growth drivers (the temperature, precipitation, insolation and the geomagnetic field intensity) that were highly correlated with V, and a function was modeled that described the behavior of V. The correlation coefficients between the derived function and experimental time series were 0.8 for larches and 0.9 for spruces. Compared with spruces, larches demonstrated higher thermo-sensitivity. A loss of tree sensitivity to temperature changes is puzzling for dendroclimatology, as a similar process might have occurred during previous periods of sharp global climate changes (as observed currently). Sensitivity of trees to geomagnetic field changes is confirmed both at long- and short-timescales. Spruces are found to be more magnetosensitive than larches.

A detailed reconstruction of changes in the factors and parameters of soil erosion over the past 250 years in the forest zone of European Russia(Moscow region)

Accelerated soil erosion is a major threat to soil,and there are great variations in the rate of soil erosion over time due to natural and human-induced factors.The temperate forest zone of Russia is character-ized by complex stages of land-use history(i.e.active urbanization,agricultural development,land abandonment,etc.).We have for the first time estimated the rates of soil erosion by the WaTEM/SEDEM model(rainfall erosion)and by a regional model(snowmelt erosion)over the past 250 years(from 1780 to 2019)for a 100-km2 study site in the Moscow region of Russia.The calculations were made on the basis of a detailed historical reconstruction of the following factors:the location of the arable land,crop rotation,the rain erosivity factor,and the maximum snow water equivalent.The area of arable land has decreased more than 3.5-fold over the past 250 years.At the end of the 20th century,the rates of gross erosion had declined more than 5.5-fold(from 28×10^(3) to 5×10^(3) t·ha^(-1)yr^(-1))in comparison with the end of the 18th century.Changes in the boundaries of arable land and also the relief features had led to a significant intra-slope accumulation of sediments.As a result of sediment redeposition within the arable land,the variation in net soil erosion was significantly lower than the variation in gross soil erosion.The changes in arable land area and in crop composition are the factors that have to the greatest extent determined the changes in soil erosion in this territory.

Fractionation and fixation of rare earth elements in soils:Effect of spiking with lanthanum,cerium,and neodymium chlorides

Industrial and agricultural activities lead to the release of rare earth elements(REEs)in wastewater and aquatic ecosystems,and their accumulation in soils.However,the behavior of REEs in soils remains somewhat unclear.In the present work the fractionation and fixation of REEs in soddy-podzolic and chernozem soils spiked with La,Ce,and Nd chlorides were studied using dynamic(continuous flow)extraction,which allows natural conditions to be mimicked and artefacts to be minimised.The eluents applied are aimed to dissolve exchangeable,specifically sorbed,bound to Mn oxides,bound to metal-organic complexes,and bound to amorphous and poorly ordered Fe/Al oxides fractions extractable by 0.05 mol/L Ca(NO_(3))2,0.43 mol/L CH_(3)COOH,0.1 mol/L NH_(2)OH·HCl,0.1 mol/L K_(4)P_(2)O_(7) at pH 11,and 0.1 mol/L(NH4)_(2)C_(2)O_(4) at pH 3.2,respectively.It is found that the fixations of added La,Ce,and Nd in the form of metal-organic complexes is predominant for both types of soils:35%-38%in soddy-podzolic soil and 50%-79%in chernozem.The fixation of added elements in the first three fractions(exchangeable,specifically sorbed,and bound to Mn oxides)is significant for soddy-podzolic soil(5%-25%).For chernozem,the relative contents of added Ce and Nd in these fractions are nearly negligible.Only the content of exchangeable La is notable,about 5%.Adding any of three elements(La,Ce,or Nd)at the level of100 mg/kg to an initial sample results in changing the fractionation and bioaccessibility of other REEs present in soil.Their contents increase in the first three fractions and decrease in fifth(oxalate extractable)fraction for both soddy-podzolic soil and chernozem.The main difference is the behavior of REEs in pyrophosphate extractable fraction.For soddy-podzolic soil,adding La,Ce,or Nd results in decreasing the contents of other REEs associated with organic matter.For chernozem,on the contrary,the contents of REEs in the form of metal-organic complexes slightly increase.These processes may be attributed to competitive binding of elements and soil properties;they must be taken into account when assessing the environmental risks of soil pollution with REEs.