Estimation of Soil Erosion Using Field and Modelling Approaches in an Undisturbed Arnhem Land Catchment,Northern Territory,Australia

An assessment of slope erosion at Tin Camp Creek catchment, Arnhem Land, Northern Territory, Australia, was carried out using the fallout environmental radioisotope caesium‐137 (¹³⁷Cs) as an indicator of soil erosion status, two numerical models (SIBERIA and the Revised Universal Soil Loss Equation (RUSLE)) and erosion pins. This undisturbed drainage basin is situated in the seasonally wet‐dry tropics, with high energy storms and a mean annual rainfall of 1389 mm. Tin Camp Creek catchment is unaffected by European agriculture or pastoral activities, but often experiences fire during the dry season. Two transects were sampled for ¹³⁷Cs in 2002 and 2004, and two models were used to convert ¹³⁷Cs measurements into soil loss estimates. Two methods using the theoretical Profile Distribution Model (PDM) gave net soil redistribution rates between +2.72 and –22.19 t ha^?1 yr^?1 and +2.95 and –24.06 t ha^?1 yr^?1, respectively, while an Australian empirical model (AEM) for uncultivated soils produced estimates between +1.84 and –7.00 t ha^?1 yr^?1 (negative values indicate soil erosion, positive, deposition). The RUSLE gave estimated soil losses for the two transects of approximately 10 t ha^?1 yr^?1, while the SIBERIA model produced values between 0.5 and 2 t ha^?1 yr^?1 for the transects and between 3.5 and 11 t ha^?1 yr^?1 for the total catchment. Average net soil losses of 14 and 15 t ha^?1 yr^?1 for the total catchment and slopes, respectively, were measured by erosion pins. The soil losses in the catchment are similar to those for some other transects in the Northern Territory and the Kimberley region of Western Australia (measured by the ¹³⁷Cs AEM), even though these areas are affected by pastoral activities. This may be at least partly explained by erosion in Tin Camp Creek catchment during high intensity rainstorms at the commencement of the wet season, especially if the slopes have been affected by fire during the previous dry season.     

The use of Caesium–137 to Assess Surface Soil Erosion Status in a Water–Supply Catchment in the Hunter Valley,New South Wales,Australia

In the absence of direct erosion measurements, the soil activity of the fallout radionuclide caesium–137 (¹³⁷Cs) offers an attractive tool for the estimation of long–term (approximately 45 years) net surface and minor rill soil erosion rates for hillslopes. A transect–based soil sampling technique was applied to one woodland and five grazed pasture hillslopes in the Williams River water–supply catchment in the Hunter Valley, New South Wales. An Australian regression model (SOILOSS) relating net soil loss from runoff–erosion plots to ¹³⁷Cs deficit in soils was used to calculate a weighted net surface and minor rill erosion rate for the six hillslopes. The net median surface erosion rates ranged between 0.00 and 0.64 t ha^–1yr^–1with the average median soil erosion rate of 0.19 t ha^–1 yr^–1(std. dev. = 0.23), indicating that these hillslopes were unlikely to be major sources of sediment to the catchment's waterways. Net soil loss rates were also shown to be low in comparison to Australia–wide data and comparable to hillslope data obtained elsewhere in the same region. Minimum and maximum error bounds were provided with each erosion rate to account for radionuclide detector count error. For one hillslope the estimated error due to detection was 1.34 t ha^–1yr^–1, while the remaining five hillslopes exhibited error of up to 0.41 t ha^–1yr^–1. Correlation analyses between the net soil loss rates and physical hillslope characteristics were non–significant.     

An Examination of Vertical Accretion of Floodplain Sediments in the Labasa River Sugarcane Belt of Northern Fiji: Rates,Influences and Contributing Processes

The ¹³⁷Cs (caesium‐137) method was used to investigate medium‐term rates of sediment deposition on the floodplain of the Labasa River, on Vanua Levu island in northern Fiji. The Labasa basin is commercially important for sugarcane farming, which provides much revenue and sustains the economy in the greater Labasa area. Alluvium was sampled at three riverbank sites in vertical increments of 30 mm. Measured net vertical accretion rates, based on analysis of depth‐profiles of ¹³⁷Cs activity, ranged from 10 mm yr^?1 at a low‐lying site near a tributary confluence with the main river, to 60 mm yr^?1 on a levée that was elevated slightly above the adjacent floodplain. These rates of accretion are high, but in general agreement with rates recorded using similar methods in other tropical Pacific island river systems. Soil erosion under sugarcane on hilly parts of the lower Labasa basin is an important factor in rapid floodplain development. Observations made during Cyclone Ami, which traversed Vanua Levu island in early 2003, illustrate the major contribution of severe storm events to floodplain sediment supply, by triggering numerous landslides on catchment slopes and in‐channel debris floods, and by generating large‐magnitude overbank floods.     

A Survey of Soil Erosion in Australia using Caesium‐137

A survey of soil erosion was conducted in Australia using the fallout radioisotope caesium‐137 as an indicator of topsoil redistribution. Two hundred and six sites were sampled, 100 within rotational cropping and horticultural use, 52 within uncultivated permanent pasture and forest, and 54 in rangelands. Average net soil losses were approximately equal for cultivated cropping lands and rangelands (ca. 5.5 t ha^?1 yr^?1), and just over 1 t ha^?1 yr^?1 for pasture and forest. The Mann Whitney U Test revealed that losses under cropping and rangeland conditions were significantly higher (p < 0.05) than under uncultivated pasture and forest. Soil loss was negatively correlated with mean annual rainfall and slope gradient, and positively correlated with slope length (Spearman's rank correlation). There was no correlation between rates of soil loss and a rainfall erosi‐vity index. An assessment of erosional events was provided by landholders for 104 sites, with their ranking being weakly but significantly correlated with soil loss estimates (r =+0.35). Sixty percent of sites had net soil losses greater than 1 t ha^?1 yr^?1, and 74% of sites had losses of more than 0.5 t ha^?1 yr^?1. This latter rate may be regarded as a limit for a tolerable level of soil loss. These high rates of soil loss have occurred since the mid‐1950s despite there being significant landholder awareness of the soil erosion hazard.     

Estimation of soil erosion on cultivated fields on the hilly Meghalaya Plateau,North-East India

The estimation of soil erosion rates in complex subtropical agricultural systems of hilly environment is difficult and most of the traditional methods have serious limitations. The ¹³⁷Cs technique allows to obtain relatively quickly retrospective medium term soil erosion results. The objective of this study was using ¹³⁷Cs approach to quantify soil loss under agricultural system which develops under growing human pressure on the hilly terrain of the Meghalaya Plateau. The measured values of caesium inventory for all sampling points are between 2% and 63% of the reference value of caesium inventory. The estimated annual soil loss for sampling points located on the slope are between 29 and 79 Mg·ha⁻¹·yr⁻¹ in the case of an improved mass balance model. It means that soil erosion in this manually tilled agricultural area cannot be neglected.     

Concordant <Superscript>210</Superscript>Pb and <Superscript>137</Superscript>Cs ages of black sea anoxic unconsolidated sediments

Two independent geochronologic radiometric methods: ¹³⁷Cs and ²¹⁰Pb were used to determine the sedimentation rate and subsequently to date the oldest sediments of a 50 cm core containing unconsolidated sediments collected at a depth of 600 m below sea surface in the anoxic zone of the Western Black Sea, off the Romanian town of Constanta. Both methods gave coincident value within experimental uncertainties of 0.42±0.20 mm·y⁻¹ for ¹³⁷Cs and 0.49±0.03 mm·y⁻¹ in the case of ²¹⁰Pb, within the Constant Initial Concentration model, which gave for the lower most sediments an age of 1.00±0.01 ka. The constant sedimentation model as well as the possible causes of observed discrepancy between experimental uncertainties are discussed.     

Fallout 137Cs and natural 40K as tracers of topsoil development during slope processes — a case study from the Daugai environs, Southern Lithuania

Investigations of soil erosion by ¹³⁷Cs method brings uncertainties of different nature. The estimation of the ¹³⁷Cs local inventory is associated with problems of data comparison and instrumental errors. In order to avoid systematic errors, the rate of soil erosion determined by the ¹³⁷Cs method is compared with the values obtained for other radioactive elements. Soil parameters must be regarded too. The aim of the work was to test the character of ¹³⁷Cs and ⁴⁰K distribution in the topsoil vertical section for determination erosion-accumulation type and ratio in different time spans. The topsoil thickened by different types of erosion-accumulation processes was sampled at a 2–3 cm interval. Soil samples were analysed by means of scintillation gamma spectrometry. The relationship between ¹³⁷Cs and ⁴⁰K inventories was weakest in the topsoil formed by mixing of soil material during the installation of artificial drains. Based on climatic characteristics, variations of theoretical soil accumulation rate in the last 50 years were calculated for the topsoil accumulated predominantly by water erosion. ⁴⁰K and ¹³⁷Cs correlation in the bottom of vertical section of topsoil or arable horizon are closest and this section may be used as a complementary parameter determining the local inventory value.     

The deserts of the Kashmir‐Tibetan frontier

Abstract

Semi-arid landscapes are vulnerable to cultivation, overgrazing and climate variability, although it is difficult to identify the relative significance of these three factors. In the South African Karoo, the ‘desertification debate' seeks to explain a change to more shrubby vegetation in heavily grazed areas. We examine these issues in catchments where farm reservoirs provide sediment stores with 137Cs, 210Pb, geochemical and mineral magnetic signatures. Rainfall data and stocking numbers are reported and current erosion rates are estimated. Sediment accumulation in the reservoirs increases between 1935 and 1940, probably due to rises in the frequency of rainfall events of >25mm day. Significant increases in sedimentation rates (×8) occur during rain-fed wheat cultivation. In an uncultivated catchment, sediment yields remain relatively high and reflect increases in erosion from hillslopes, colluvial storage, and cultivated land sources. Gully systems have acted as transport routes rather than sediment sources over the last ～70 years. Badland erosion rates average ca. 50t ha^?1 yr^?1. At Ganora, their development in the 1920s strongly influences peak sedimentation between 1970 and 1980. Any delay between badland initiation and increased sediment yield appears to be a function of landscape connectivity. Recovery following disturbance is occurring slowly and is likely to take >100 years. De-stocking and better management systems are reducing erosion rates but may be offset by increases in rainfall intensity.     

Sedimentation rates in the Lake Qattinah using 210Pb and 137Cs as geochronometer

The constant rate of supply (CRS) of excess ²¹⁰Pb model was successfully applied to assess ²¹⁰Pb data of two sediment cores from the lake Qattinah, Syria. Gamma spectrometry was used to determine ¹³⁷Cs and ²¹⁰Pb activity concentrations. The bottom of the cores was ²¹⁰Pb-dated to years 1907 and 1893. The accumulation rates were determined using ²¹⁰Pb method and found to vary similarly in both cores from 0.10 ± 0.01 to 3.78 ± 0.57 kg m^?2 y^?1 during the past century. ¹³⁷Cs was used as an in-dependent chronometer. The two distinct peaks observed on the ¹³⁷Cs record of both cores, corresponding to 1965 and 1986, have allowed a successful validation of the CRS model.     

Re‐sampling for Soil‐caesium‐137 to Assess Soil Losses after a 19‐year Interval in a Hunter Valley Vineyard,New South Wales,Australia

Soils in a lower Hunter valley vineyard, New South Wales, Australia, were sampled and analysed for caesium‐137, an indicator of soil erosion status, in 1984–1985 and 2004. From the time of the vineyard's first establishment in 1971 to 1985, estimated soil losses were 250 tonnes (equivalent to 64.2 t ha^?1 yr^?1). Re‐sampling in 2004 showed that soil losses were 48 tonnes in the 19 years since 1985, equivalent to 9.7 t ha^?1 yr^?1. The decline in erosion rates may be explained by a change in land and soil management from intensive cultivation to one of no cultivation (sod culture) in 1998, and a lower annual rainfall and fewer rain‐days per year in the period from 1986 to 2004.     

The link between fluids and rank variation in the South Wales Coalfield: evidence from fluid inclusions and stable isotopes

Fluid inclusion and stable isotope data from quartz and carbonate minerals in fracture fillings and ‘ironstone’ nodules from the South Wales Coalfield have been used to characterise the fluids generated during basin evolution and associated coalification. Carbonates grew first, probably at relatively shallow depths and low temperatures (<100°C). The carbonates exhibit a trend of increasing C‐isotopic values across the coalfield, ranging from δ¹³C = ?12‰ VPDB in the SE of the coalfield to 0‰ VPDB in the NW, possibly as a result of increasing methanogenesis in the deeper (NW) parts of the coalfield. Quartz formed at a later stage of basin formation, probably at temperatures between 150 and 200°C. Fluid inclusions in these minerals suggest that burial and coalification of the sediments were associated with mixed aqueous–petroleum fluids. Furthermore, the density of these petroleum fluids decreases towards the NW of the coalfield, where the rank of the associated coal increases to anthracite grade. The study confirms that the composition and temperature of these fluids closely correlate with the variations in coal rank, indicating a possible causal link. The data also give general support to models that propose regional fluid flow in the basin. and are consistent with the erosion of approximately 2 km of section which is not preserved today. A geothermal gradient (at maximum burial) of 45°C km^?1 is proposed, and thus no exceptionally anomalous thermal regime is required to explain coal rank variation.     

Consilience of genetics and archaeobotany in the entangled history of rice

Major leaps forward in understanding rice both in genetics and archaeology have taken place in the past decade or so—with the publication of full draft genomes for indica and japonica rice, on the one hand, and with the spread of systematic flotation and increased recovery of archaeological spikelet bases and other rice remains on early sites in China, India and Southeast Asia. This paper will sketch a framework that coherently integrates the evidence from these burgeoning fields. This framework implies a reticulate framework in the phylogeny of early cultivated rice, with multiple starts of cultivation (two is perhaps not enough) but with the key consolidations of adaptations that must have been spread through hybridisation and therefore long-distance cultural contacts. Archaeobotanical evidence allows us to document the gradual evolutionary process of domestication through rice spikelet bases and grain size change. Separate trends in grain size change can be identified in India and China. The earliest centre of rice domestication was in the Yangtze basin of China, but a largely separate trajectory into rice cultivation can be traced in the Ganges plains of India. Intriguingly, contact-induced hybridisation is indicated for the early development of indica in northern India, ca. 2000 BC. An updated synthesis of the interwoven patterns of the spread of various rice varieties throughout Asia and to Madagascar can be suggested in which rice reached most of its historical range of important cultivation by the Iron Age.     

Vegetation,land, and wood use at the sites of Bat and Al‐Khashbah in Oman (fourth–third millennium BC)

About 4200 charcoal fragments have been identified from the fourth‐ to third‐millennium BC archaeological sites of Bat and Al‐Khashbah in order to gain an understanding of plant resources available at the sites. Acacia sp., Ziziphus sp., and Tamarix sp. were the main taxa identified at both sites and indicate a similar vegetation composition as today. Phoenix sp. (date palm) charcoal also has been found at both sites. Whereas the cultivation of date palm for the 2700–2300 BC layers from Bat was likely, given other circumstantial evidence (i.e. local cereal cultivation and floodwater irrigation), it is unclear whether date palm was cultivated at Al‐Khashbah. Especially for the older periods (3300–2700 BC) it is possible that nomadic pastoralists were exploiting and/or managing wild date palms. The find of Avicennia marina at Al‐Khashbah indicates long‐distance contacts with the coast.     

New evidence on the introduction,cultivation and processing of hemp (Cannabis sativa L.) in southern Sweden

Subfossil remains of Cannabis sativa L. (hemp) have been found at Lindängelund in the region of Malmö, southern Sweden. These represent the earliest robust evidence so far for hemp retting in Scandinavia. Finds of seeds, stems and pollen of C. sativa from a waterlogged context on a settlement dating to the Roman Iron Age demonstrate that the plant was locally cultivated and processed during the 1st–2nd centuries AD. An introductory phase in Scandinavia is proposed (c. AD 1–400) during which the cultivation of hemp was apparently small scale and processing was probably carried out within settlements. In the succeeding centuries, c. AD 400–550 (the Migration Period), remains of hemp are mostly found in pollen records from lake sediments, and less frequently in the archaeological record. This could indicate that the process of hemp retting relocated from settlements to lakes shores where activity became larger in scale and more integrated with the prevailing agricultural system.     

Sensitivity of bulk sedimentary stable carbon isotopes to prehistoric forest clearance and maize agriculture

The stable carbon isotope compositions (δ¹³C) of tropical lake sediments and soils have been used to reconstruct the occurrence of prehistoric maize cultivation and its relative importance through time. This study assesses some of the possible variables affecting the response of lake sediment bulk organic carbon isotope (δ¹³C_TOC) values to variations in the scale of prehistoric maize cultivation and the potential of this proxy to yield quantitative estimates of the scale of prehistoric maize agriculture in small tropical watersheds. High resolution analyses of δ¹³C_TOC values, maize pollen concentrations, and mineral influx were conducted on sediments deposited during a ∼220 year period of prehistoric maize agriculture in the watershed of Laguna Castilla, a small lake in the mid-elevations of the Cordillera Central, Dominican Republic. Close correspondence between δ¹³C_TOC values and maize pollen concentrations in the Laguna Castilla sediment record indicates a close relationship between the isotopic values and the scale of prehistoric maize cultivation. Correlations between the δ¹³C_TOC signature and mineral influx indicate that the isotope record is also sensitive to variations in allochthonous carbon delivery. This study establishes that sedimentary δ¹³C_TOC values can provide a highly sensitive proxy of the spatial scale of prehistoric maize agriculture in small tropical watersheds, but emphasizes the need for a better understanding of sediment dynamics and carbon cycling in anthropogenically modified landscapes before this proxy can be widely employed in diverse archaeological settings.     

Fluid circulation related to post‐Messinian extension,Thassos Island,North Aegean

In the North Aegean Domain, Thassos Island contains a Plio‐Pleistocene basin controlled by a large‐scale flat‐ramp extensional system with a potential décollement located at depth within a marble unit. Numerous mineralizations associated with normal faults of Plio‐Pleistocene age are the sign of fluid circulation during extension. Two main generations of fluid flow are recognized, related to Plio‐Pleistocene extension. A first circulation under high‐temperature conditions (about 100–200°C) resulted in dolomitization of marbles near the base of the Plio‐Pleistocene basin. The dolomites are characterized by low δ¹⁸O values (down to 11‰ versus Standard Mean Ocean Water). Some cataclastic deformation affected the dolomites. Hydrothermal quartz that crystallized in extension veins above a blind ramp also has low δ¹⁸O values (about 13‰). This shows that high‐temperature fluids moved up from the décollement level toward the surface. A second downward circulation of continental waters at near‐surface temperature is documented by calcite veins in fault zones and at the base of the Plio‐Pleistocene basin. These veins have O isotope values relatively constant at about 23–25‰ and C isotope values intermediate between the high δ¹³C value of the carbonate host rock (about 1–3‰ versus Peedee Belemnite) and the low δ¹³C value of soil‐derived carbon (?10‰). The calcites associated with the oxidative remobilization of primary sulphide Zn–Pb mineralization of Thassos carbonates have comparable O and C isotope compositions. Hot fluids, within the 100–200°C temperature range, have likely contributed to the weakening of the lower marble unit of Thassos and, thus, to the process of décollement.     

Pollen analytical investigations at Crosby Warren, Lincolnshire, in the Vicinity of the iron age and Romano-British settlement of Dragonby

Open-cast ironstone mining at Crosby Warren, near Scunthorpe, Lincolnshire exposed an extensive section through “cover sand” deposits. revealing buried podzol soils and peat layers. Stratigraphic studies, pollen analysis and radiocarbon dating have been carried out on three representative profiles. From these investigations it would appear that the “cover sands” in this area were stabilized under mixed oak woodland by c. 300 BC. After c. 100 BC woodland clearance and farming activities have been distinguished. Local alterations in land-use may be linked with cultural developments at the nearby Iron Age and Romano-British settlement of Dragonby. It is suggested that the impact of man upon the vegetation during Iron Age and Romano-British times probably facilitated podzolization and sand blowing.     

From pedologic indications to archaeological reconstruction: deciphering land use in the Islamic period in the Baida district (north-western Sicily)

The aim of this work was to detect imprints on soil properties from former Islamic land use (9th to 11th century) using a multi-method, soil-chemical approach. Four soil profiles (with buried horizons) found in the vicinities of former Islamic settlements in Sicily were analysed for phosphorus (total, organic and inorganic), nitrogen (total, NO₃⁻ and NH₄⁺), carbon compounds (δ¹³C, lipids, polycyclic aromatic hydrocarbons (PAH) and functional groups), physical and chemical C-fractions and the state of soil weathering. Two soil profiles contained ceramic sherds from the Islamic period. Inorganic nitrogen forms, phosphorous and the PAH content indicated strong impacts from traditional agriculture and/or burning. Radiocarbon dating of soil organic carbon (SOC) fractions from buried horizons showed that distinct changes must have occurred during the Islamic epoch. The isotopic composition of SOC indicated that land use was probably different in earlier times. C₄ plant cultivation was expected but surprisingly lipid analyses did not confirm this. A high amount of aliphates and low C/N ratio indicated a good, long-term SOC stabilisation under the native conditions combined with Islamic land use. The irrigation of the soils probably increased the production of weakly-crystalline Fe forms that helped to stabilise SOC.     

Relict Soils and Early Arable Land Management in Lofoten, Norway

Relict arable soils dating fromc.AD700 provide an opportunity to identify early arable land management practices in the agriculturally marginal landscapes of the Lofoten archipelago, northern Norway. Synthesis of field survey and soil thin section micromorphology supported by image analysis suggests that there was deliberate management of erodible sandy soils in sloping locations to create small areas of cultivation terrace, with a range of materials used as soil amendments to stabilize the accumulated soil and enhance fertility. Small areas of sandy soils in more gently sloping locations were also cultivated, again with a range of materials used as amendments and which contributed to a significant increase in soil thickness. The last phase of cultivation commenced during the late 1800s and involved the reclamation of wetter, peaty soils by spade. These patterns of arable land management are repeated in different parts of Lofoten and indicate that despite the climatic and economic marginality of arable activity in Lofoten, land management practices were developed and applied to permit barley production from small areas.     

Mushrooms Their Consumption,Production and Culture Development

Abstract

In the last 20 years, mushroom consumption and production have increased at a faster rate than almost any other agricultural food product. The consumption and production of Agaricus (A. bisporus and A. bitorquis) and the Shiitake (Lentinus edodes) mushrooms account for 74% and 14%, respectively, of the total world production and demand for cultivated mushrooms. Since the origin of Agaricus cultivation in France, much progress has been made and the bulk of the scientific and engineering progress has been achieved since the beginning of this century. Mushroom science, a composite science of many disciplines including plant pathology, entomology, horticulture, food science, agricultural engineering, agricultural economics and rural sociology has contributed a great deal to the worldwide growth of the industry. Future improvements in mushroom culture will come not only from a more thorough understanding of single facets within the overall process, but from a more complete understanding of the interrelationship of these facets with each other.