Humus-rich Topsoils Research Articles

Medium-term transformation of Chernozems under broadleaf forests in the temperate climate of south-east Poland

Water erosion, accelerated in sloped landscapes by intense cultivation (ploughing), can rapidly degrade humus-rich topsoil horizons of chernozemic soils, leading to an irreversible loss of the most valuable soil resources, in particular in areas with relict Chernozems/Phaeozems. An afforestation can effectively control erosion rates, but dense canopy forests are commonly listed among factors that support the transformation of Chernozems into Luvisols/Retisols. A comparison of the morphology and physico-chemical properties of adjacent arable and forest soils was carried out in four catenas located in the patches of relict chernozemic soils in the loess belt of south-east Poland. An analysis has evidenced that mixed broadleaf forests have generated during the 200–300-year-long period (an approximate time since afforestation of the sites under study) topsoil acidification (by approximately 1–1.5 grade compared to adjacent arable soils), base cations leaching (below 10 cmol(+) kg−1), decrease of soil organic carbon pools (by 15–35% in the soil column of 0–50 cm) and clay depletion (by ca. 4%). The subsurface Bt (argic) horizons have developed in all afforested and some of arable soil profiles. However, all studied forest soils preserved the mollic or chernic horizons and in most cases retained the same reference soil group as adjacent arable soils (Chernozem or Phaeozem). It means that even in temperate humid climate as in south-east Poland, mixed broadleaf forests, consisting of tree species known with little acidifying impact on soil, may not rapidly degrade Chernozems. The observed evidence of physicochemical and morphological transformation is apparently weaker than the reported soil destruction caused by water erosion and justifies the controlled afforestation of the relict Chernozems and Phaeozems as a means of their preservation against rapid loss.

Geophysical investigation of the Orle River fracture system in Igarra Township, southwestern Nigeria

The subsurface structure and propagation geometry of the fracture system controlling the Orle River Channel in the Igarra Township, Southwestern Nigeria, have been investigated via a multi-method geophysical survey. The goal was to delineate the nature, distribution, and spatial propagation geometry of the fracture system and evaluate its potential to serve as storage and distribution features for groundwater within adjoining areas. 2D electrical resistivity, total field magnetic, and co-planar loop conductivity measurements were collected along four traverses using an ABEM1000 Terrameter unit, a GEMS Magnetometer, and an EM34 Co-planar loop electromagnetic system. Traverses were established to run across and parallel to the river channel. The observed electrical resistivity field data were inverted for subsurface 2D resistivity structure using a commercially available 2.5D finite element modelling inversion software. Magnetic field intensity data and ground conductivity data were presented against station positions. Three subsurface layers were delineated at the survey site; (1) surficial humus-rich and wet top-soil, (2) a thin poorly developed weathering layer, and (3) the fresh bedrock which occurs as relatively shallow levels and often outcrops. The River channel is controlled by multiple fractures usually located at or near the contracts between contrasting rock types. Fracture dip is usually in the northerly direction but conjugates, dipping southwards also occur in the most northerly extremes of the imaged fracture system. Upstream the fracture path is wider and along with the imaged overburden, isjuxtaposed northwards of the channel axis suggesting a much broader river channel in the geologic past. Low aperture fractures imaged tangential to channel axis likely serve to funnel surface and groundwater from the channels to the surrounding areas. Where such low aperture fractures can be delineated, they offer the best chances of groundwater abstraction within adjoining areas, particularly during the dry season.

Origin, age and transformation of Chernozems in northern Central Europe – New data from Neolithic earthen barrows in SW Poland

Among the clay-illuviated soils, dominant in the loess belt in southern Poland, islands of chernozemic soils are distinguished by their spectacular agricultural productivity. However, those soils are not marked as Chernozems/Phaeozems in European and world soil maps due to their common excessive wetness and doubts regarding their origin. Well-preserved earthen barrows of the Funnel Beaker culture, discovered recently in Muszkowice (SW Poland) offer a unique possibility of pedo-archaeological reconstruction (the first of such in Poland) of the pre- and post-Neolithic development of soil cover in loess-dominated areas, and explanation of the existing differentiation of soil cover into neighbouring Chernozems and Retisols. The buried chernozemic soil (Phaeozem) in Muszkowice started to develop in the Late Pleistocene period (mean residence time of humus – 12,670–13,000 cal BP). Until the burial (ca. 5480–5310 cal BP), an at least 22-cm thick mollic horizon has developed, with secondary carbonates accumulation at ca 80 cm. The barrow mound soil, constructed entirely of initially humus-rich topsoil material, has transformed into Retisol with fully developed, thick eluvial and illuvial (argic) horizons, and still preserved a high content of humus in the barrow mound soil profile. Further, the surrounding soils are entirely altered into Retisols (with secondary carbonates starting at 135–160 cm). Taking into account the palynological reconstruction from the nearest pollen profile in the loess-covered area, a crucial importance of the open-canopy (mainly oak) forests is concluded for the persistence of Chernozems under a temperate (increasingly moist) climate from the Early Holocene to the Neolithic period. In turn, the close-canopy broadleaf forests (mainly beech) are considered to be responsible for the rapid transformation of Chernozems/Phaeozems into Retisols/Luvisols in the Late Holocene. Chernozems have persisted and probably even rejuvenated only in the areas of permanent settlement since the Neolithic until the present time, where human activity (farming, pasturing) has eliminated a continuous broadleaf/beech close-canopy forest cover.

Subsurface electrical resistivity imaging and electromagnetic conductivity profiling at a proposed construction site at Adekunle Ajasin University campus, Akungba-Akoko, South-Western Nigeria

Electrical resistivity imaging and co-planar loop electromagnetic conductivity measurements have been employed to delineate the bedrock topography and subsurface distribution of structural features at a construction site on the campus of Adekunle Ajasin University. The goal was to map the subsurface geological disposition and to identify features which could adversely impact on the ongoing construction works. Data were collected along three geophysical traverses using the ABEM1000 Terrameter unit and the EM34 Co-planar loop electromagnetic system. Traverse 1 trend roughly east-west for a total length of 155m while traverses 2 and 3 are trend north-south for 80m each. The collection of electrical resistivity data utilized the dipole-dipole array with an electrode separation of 5 m and maximum dipole spread of 35m. Observed field data were processed and inverted using a finite-element modelling inversion algorithm. Conductivity were collected at 10m coil separation and plotted against station positions. A station separation of 5m was maintained on all traverses for both data sets. Three geo-electric layers were delineated; a thin highly discontinuous low resistivity layer representing the humus-rich top soil, a continuous consistently high resistivity layer with a highly rugose upper layer and several near vertical scarps representing the fresh bedrock and intermediate resistivity layer representing the weathered bedrock separating the upper low resistivity and basal high resistivity signatures. Overburden thickness rarely exceeds 4 m with the exception of the deep weathering section in the southwest and at fracture points with the bedrock. Perennial groundwater flow at the site is restricted to the southeastern sections of the site. KEYWORDS : Akungba-Akoko, electrical resistivity imaging, ground conductivity, bedrock structure, foundation studies.

Humus-rich topsoils in SW Norway – Molecular and isotopic signatures of soil organic matter as indicators for anthropo-pedogenesis

Some previous studies showed that the formation of several deep dark humus-rich topsoils in Northern Europe was strongly influenced by the application of different organic materials by anthropogenic activities in former times. Such topsoils classified as plaggic Anthrosols also occurred in the Jæren region in SW Norway. However, source material and formation time of these Plaggic Anthrosols have not yet been clarified. Close to this region we found further humus-rich topsoils in the Karmøy municipality (2 sites at main island of Karmøy and 1 site at Feøy). These soils show a thick humus-rich topsoil up to 30 cm, and their formation cannot only be explained by natural conditions. We analyzed the molecular signature of the soil organic matter (SOM) by benzene polycarboxylic acids (BPCA), non-targeted bulk SOM mass spectrometry, δ34S and 14C AMS dating in order to determine source materials and the age of the SOM. The black carbon (BC) contents of the plaggic soils in Jæren (mean 3.4 g kg−1) deliver clear evidence for inputs of combustion residues from ancient fire management and/or from settlements. The C-XANES and Py-FIMS-spectra reveal relative enrichments of aromatic C and heterocyclic N compounds in the plaggic soils corresponding to the BC contents. In contrast, the humus-rich topsoils in Karmøy seem to be unaffected by fire management due to the low BC contents (mean 0.6 g kg−1) and the relative low portions of aromatic C and heterocyclic N compounds from C-XANES and Py-FIMS. The δ34S isotope signature of the SOM ranged from 10.6 to 15.2‰ in the soils at the islands and 10.0 to 13.5‰ in Jæren, corresponding to the Anthrosols in the Baltic Sea region (Median: δ34S = 11.5‰) and suggest an input of marine biomass (δ34S of seaweed = 20‰). The AMS 14C dating and complementary archaeological literature implied that the soils in Jæren and Karmøy have been formed between the Roman Iron Age (500 BC to AD 500) and the Viking Age (AD 800 to AD 1,000). Our results provide strong evidence for an anthropo-pedogenesis of the humus-rich topsoils in Karmøy and indicate parallels to the plaggic soils in Jæren as well as to Anthrosols in the Baltic Sea region. Therefore, we propose to classify the humus-rich topsoils in Karmøy as Anthrosols.

Geoarchaeological Study of Szálka and Vajda Kurgans (Great Hungarian Plain) Based on Radiocarbon and Geophysical Analyses

ABSTRACTTwo archaeologically unexplored mounds were studied in the area of the central Great Hungarian Plain. The age of the construction of the mounds was clarified on the basis of radiocarbon (14C) age determination of buried soil layers. Different, later-building phases of the mounds were detected by pedological and geo-electric analyses of the human-made layers. The age of the buried soils was corrected for the reservoir age of the recent soils found in the surroundings of the mounds. Radiocarbon ages of the carbon extracted from the soils at temperatures 400 and 800ºC were almost completely the same. Based on the calibrated ages of cal BP 4830–5270 (Szálka Mound) and cal BP 4880–5290 (Vajda Mound) of the buried soil layers, the identified kurgans were built by people of the Copper Age Yamnaya Culture. On the basis of the pedological and geophysical analysis of the layers, Szálka Mound and Vajda Mound were built in two and in three phases respectively from the chernozem-like humus-rich topsoil layers of the surrounding area. The former shallow quarry sites have been almost completely filled and cannot be identified at the foot of the mounds even using geodetic methods.

Human activity formed deep, dark topsoils around the Baltic Sea

Previous findings showed that the humus-rich topsoils designated as Chernozems around the Baltic Sea were influenced by the addition of pyrogenic organic matter linked with human activity. For a deeper insight into the human activities, we investigated the isotopic signatures of sulphur (δ34S) and the 14C age from nine soil profiles in order to clarify which kind of organic matter was added to the soils and to estimate the beginning of the Chernozem formation. The study area was expanded by two additional Baltic Chernozem profiles on the island of Fehmarn in which we also analyzed the portions of black carbon (BC) with the benzene polycarboxylic acids (BPCA) method and the SOM composition with the Pyrolysis-field ionization mass spectrometry (Py-FIMS). The compound classes from Py-FIMS and the BC portions were similar to all other Baltic Chernozems and Chernozems from European loess areas and indicated an input of combustion residues to the soils. The δ34S isotope signature of the SOM in the Axh-horizons (Median: δ34S=11.5‰) at the island of Poel and Sjaelland indicated an input of seaweed (δ34S=20‰) or other marine biomass. The AMS14C ages from the humin fraction, i.e. the oldest fraction of SOM, of the Axh-horizons and the settlement history implied that the formation of the Baltic Chernozems started in a time period between the Nordic Bronze Age (3800 to 2800BP) to the Roman Iron Age (2700 to 2000BP). In summary, the results provided a strong evidence for an input of combustion residues and marine biomass by anthropogenic activities and we conclude that the formation of the Baltic Chernozems reflects an anthropo-pedogenesis. Therefore, we propose to classify these soils as Anthrosols.

Effects of Sowing Media and Sowing Depth on Germination and Growth of Lecaniodiscus cupaniodes (Planch. Ex Benth).

This study examines the effect of sowing media and sowing depth on the germination and growth of Lecanodiscus cupanoides (Planch.Ex Benth). The germination of L. cupanoides seed was significantly affected by sowing depth and sowing medium at p=0.05. The result of various sowing media and sowing depth showed that the seed sown at 2 cm and 5 cm depths had the highest germination percentage of 52% each. This was followed by surface sowing with 49.3% and the least germination was found at 7 cm depth. Also, the highest germination was also recorded in sawdust with 50 % germination followed by those planted in topsoil with 44%. Least germination percentage was recorded in river sand (41%). Lecanodiscus cupanoides seedling height was significantly affected by sowing depth and sowing medium. The highest plant height was recorded in seeds sown at 5 cm depth (9.6 cm) while the least height was recorded in Sawdust with 8.6 cm.Shoot height was highest in humus rich top soil with 9.9 cm followed by river sand with 9.2 cm. The least shoot height was found in sawdust with 8.6 cm. Other parameters are mean leaf production and collar diameter. The highest leaf production was found in seeds sown in river sand at 2 cm depth with mean values of 10.5 and 11.0 respectively. The highest collar diameter was in humus rich top soil and river sand with value 2.6 mm. Observations from the study shows that to propagate L.cupanoides on large scale, it is better to sow at the depth of 5 cm and in sawdust for its germination.Keywords: Lecanodiscus cupanoides, sowing depth, sowing media, seedling growth and germination

Regeneration of Rauwolfia vomitoria

Rauwolfia vomitoria is a fast disappearing medicinal plant in Nigeria. Evidence from this current study showed that seedlings of the species under study are best raised by vegetative propagation. From total immerse method, 80% rooted stem cuttings was observed. Drip down method had 60% rooted stem cuttings while the Quick dip method had 70% rooted stem cuttings. The maximum value obtained from the seed germination studies was 50%. The growth medium of one part river sand and 3 parts humus rich topsoil was observed from this study to support the best seedling growth. Key words: Rauwolfia vomitoria, seed germination, vegetative propagation, regeneration.

Macropropagation of Ocimum gratissimum,/i> L: A multi purpose medicinal plant in Nigeria

The purpose of this study was to determine optimum macropropagation method for Ocimum gratissimum, a multi purpose medicinal plant. The result showed that significant differences exist as influenced by seed sowing depth and type of soil. Seed sown at 1 cm depth in humus rich topsoil had 80% germination as against 26.3% from river sand of the same sowing depth. The surface sowing in humus rich topsoil had 33.3% while 23.3% was obtain from surface sowing in river sand. The total plant height was 30.6 cm from humus rich topsoil and 27.4 cm from river sand. Other parameters are mean number of leaf production which was 24.0±0.05 from humus rich topsoil and 12.0±0.04 from river sand both from seedlings of 1 cm depth of sowing. For seedlings from surface sowing mean leaf production was 20.8±0.02 and 10.07±0.01 from humus rich topsoil and river sand, respectively. Evidence from the study led to the conclusion that humus rich topsoil and seed sowing depth of 1 cm are the most suitable method(s) of propagating O. gratissimum.

Regeneration of Rauwolfia vomitoria

Rauwolfia vomitoria is a fast disappearing medicinal plant in Nigeria. Evidence from this current study showed that seedlings of the species under study are best raised by vegetative propagation. From total immerse method, 80% rooted stem cuttings was observed. Drip down method had 60% rooted stem cuttings while the Quick dip method had 70% rooted stem cuttings. The maximum value obtained from the seed germination studies was 50%. The growth medium of one part river sand and 3 parts humus rich topsoil was observed from this study to support the best seedling growth.

Landscape development in Dutch coastal dunes: the breakdown and restoration of geomorphological and geohydrological processes

SynopsisIn Dutch coastal dunes, geomorphological and geohydrological processes have been adversely affected by intensive utilisation of the dunes. In the past, wide-scale stabilisation, notably for reasons of coastal defence, stopped nearly all aeolian activity. Rejuvenation did not take place and succession to mature-type ecosystems increased. Artificial infiltration with eutrophic river water and extraction of groundwater for drinking water catchment modified the geohydrology of the wet-dune environment.Today, actions are being taken to restore geomorphological and geohydrological processes. Managing authorities join forces with universities and policy makers to strike the right balance between conflicting interests. Applied research helps to develop management strategies.Two types of research are discussed: (a) geomorphological work on the development of blow-outs; (b) geohydrological work on the development of dune slacks. Questions considered are: do blow-outs grow to an unlimited extent or do they have optimum size and shape corresponding to aerodynamic conditions? Are there natural stabilisation mechanisms for blow-outs? What is the ecological impact of drinking water catchment? Which aspects should be considered to restore the dune slack environment in catchment areas?Our findings are that blow-outs in The Netherlands have an optimum length:width ratio of about 2 with a blow-out length varying between 20 and 30 m. After 10–15 years without artificial stabilisation measures, the areas studied present an average of about one blow-out per hectare. Natural stabilisation mechanisms include algae which colonise deflation sites inside the blow-out and low secondary dunes which develop at the immediate leeward side of the blow-out. Blow-outs situated at or near downhill slopes of 6–12° may easily extend into larger deflation surfaces. Water erosion, probably caused by the water-repellency of humus-rich top soil, often precedes wind erosion on south- and south-east oriented slopes.Drinking water production caused dessiccation of dune slacks and the disappearance of associated vegetation. In areas where infiltration with river water from outside the dunes is also applied, inudation and eutrophication drastically changed the dune environment. Nitrophilous plants appeared, especialy along banks of infiltration ponds, but also in seepage ponds. The plant cover depends on nutrient concentration of the (infiltrated) groundwater but especially on the flux of the groundwater. A high rate of flux leads to high nutrient loads, encouraging the growth and eventually dominance of nitrophilous plants. Restoration of dune slacks depends on the quality and the flux of the groundwater, on the streamlines of the groundwater flow in the dune body in relation to the orientation of the seepage ponds, on the presence of peaty or clayey adsorptive layers in the subsoil and possibly also on the presence of a rainwater lens occurring on top of the infiltration water.