Changes In Soil Erosion Research Articles

The consequences of land-cover changes on soil erosion distribution in Slovakia

Soil erosion is a complex process determined by mutual interaction of numerous factors. The aim of erosion research at regional scales is a general evaluation of the landscape susceptibility to soil erosion by water, taking into account the main factors influencing this process. One of the key factors influencing the susceptibility of a region to soil erosion is land cover. Natural as well as human-induced changes of landscape may result in both the diminishment and acceleration of soil erosion. Recent studies of land-cover changes indicate that during the last decade more than 4.11% of Slovak territory has changed. The objective of this study is to assess the influence of land-cover and crop rotation changes over the 1990–2000 period on the intensity and spatial pattern of soil erosion in Slovakia. The assessment is based on principles defined in the Universal Soil Loss Equation (USLE) modified for application at regional scale and the use of the CORINE land cover (CLC) databases for 1990 and 2000. The C factor for arable land has been refined using statistical data on the mean crop rotation and the acreage of particular agricultural crops in the districts of Slovakia. The L factor has been calculated using sample areas with parcels identified by LANDSAT TM data. The results indicate that the land-cover and crop rotation changes had a significant influence on soil erosion pattern predominately in the hilly and mountainous parts of Slovakia. The pattern of soil erosion changes exhibits high spatial variation with overall slightly decreased soil erosion risks. These changes are associated with ongoing land ownership changes, changing structure of crops, deforestation and afforestation.

Short-term changes in upland soil erosion in England and Wales: 1999 to 2002

Erosion was assessed on upland sites between October 2001 and June 2002, and compared with measurements of erosion made at the same sites during previous visits (1999). In addition to highlighting the scale of changes in erosion extent and nature over the sample period, the data were used to determine the influence of field site management and weather conditions on upland erosion. Results indicated that site erosion continued over the duration of the study, with most upland regions of England and Wales experiencing increases in erosion area and volume. On 52% of the 139 sites surveyed, increases in erosion extent resulted in 705 m 2 of newly exposed soil. Sheep were identified as the most frequent cause of this increased erosion, although the impacts of humans (through vehicle access, footpaths and drainage) were also extensive. Water-driven erosion processes were also prevalent in the maintenance of bare soil, both alone and in combination with other factors such as sheep, walkers and general weather conditions. Revegetation of bare soil was also an important feature of upland sites, resulting in a net decrease in erosion area on 63% of sites. The implications of these changes in erosion are discussed in the light of continuing changes in land use and management in the UK uplands, particularly those of reform of the EU Common Agricultural Policy (CAP), and in view of predicted changes in climate.

Vegetation Cover Plays the Most Important Role in Soil Erosion Control

To obtain, characteristics and behaviors of soil erosion phenomena, to control it's harms and reduce it's risks, realistic data from soil erosion rates are necessary. Mean while, measuring soil erosion rates particularly in large scale is a time consuming and expensive task. Moreover, spatial and temporal changes of soil erosion increase this problem. Therefore, to find out a certain way of creating capable methods which easily and quickly be able to estimate soil erosion rate, is quite logical. So, different models are widely used, but, may be the most important consideration with this regard is that, these models should be previously, tested and adopted to defined areas to stop probability of causing some huge and meaningful errors. Therefore, to achieve the above mentioned aim, different methods are used. Anyway, conditions which resulted to create a suitable model, should be considered in a defined area where, model is applied, unless, model application can leads to huge risks. This study is an attempt with this refer, that is, with comparing measured soil loss rates and predicted soil erosion rates from a defined catchment area, created a reasonable relationship between them and achieved the main aim of the study. That is, one of the small upland catchments of Emam kandi of Urmia with 75 ha area which is part of the Urmia lake catchment area and under layned by calcareous parent material, is selected as a study site. Selected catchment has natural pasture and has closured during the recent years. To calculate sediment yield the following processes were done: first, estimating the volume of trapped sediments, then, surveying the catchment area, for calculating sediment yield. Measured sediment yield is 6.19 t ha(-1) year(-1) which leads to soil loss rate of 13.76 t ha(-1) year(-1) by using Sediment Delivery Ratio (SDR). Also, inside the measurement of sediment yields and calculation of soil loss rates, two models of MUSLE and PSIAC were used respectively after exclosure and before exclosure to predict soil loss rates. Predicted soil loss rates by MUSLE and PSIAC respectively are 12.80 and 26.5 t ha(-1) year(-1). Finally, Comparisons and statistical analysis and scientific discussions were made.

Fluvial adjustments to soil erosion and plant cover changes in the central spanish pyrenees

ABSTRACT. Until the middle of the 20th century, Pyrenean rivers were characterized by braided channels, unstable sedimentary structures and an almost complete lack of plant cover in the alluvial plain, due to the high sediment yield in hillslopes and the occurrence of frequent and intense flooding. This was probably related to strong demographic pressures, including the cultivation of steep slopes, frequent fires, deforestation and overgrazing. Depopulation and farmland abandonment resulted in plant recolonization in formerly cultivated areas, causing a decrease in runoff and sediment yield. As a consequence, most Pyrenean rivers tend to reduce the width of the alluvial plain and to replace the braided pattern with an incised, somewhat meandering pattern, involving the construction of new terrace levels and the stabilization of fluvial bars.

Changes in soil erosion associated with the shift from conventional tillage to a no-tillage system, documented using 137Cs measurements

Caesium-137 measurements have been used to document changes in the rate and extent of soil erosion associated with the shift from conventional tillage to a no-till system on a farm in south-central Chile. The study site is located in the Coastal Mountains of the 9th Region (38°37′S 73°04′W), and is characterized by Araucano series Ultisols (Typic Hapludult), a temperate climate and a mean annual precipitation of 1100 mm year −1. A field, which was under conventional tillage until May 1986 and which was subsequently managed using a no-till system, was selected for the study. An approach for using 137Cs measurements to quantify the medium-term erosion and deposition rates associated with the periods of contrasting land management documented previously was employed. This approach involves both a standard method and a simplified method, which permits a larger number of sampling points to be used. In this study, emphasis was placed on application of the simplified method, which has the important advantage of requiring only two 137Cs measurements per sampling point. The results obtained for the study field showed that the implementation of no-till practices, including crop residue management, coincided with a reduction in the net erosion rate by about 87% and the proportion of the study area subject to erosion from 100% to 57%, and therefore significantly decreased soil and nutrient loss. Reduced soil and nutrient loss has important on-site benefits, in terms of sustainable management of the soil resource and maintaining crop productivity, as well as reducing off-site problems associated with the degradation of river water quality.

Modeling vegetation coverage and soil erosion in the Loess Plateau Area of China

Soil erosion is still one of major issues limiting agricultural and forestry productivity in Loess Plateau of China. Vegetation plays an important role in controlling soil erosion, but studies on modeling dynamics of vegetation and soil erosion and interaction between them were hardly reported. We hypothesized that changes of vegetation coverage and soil erosion as affected by climate factors and human activities in the Loess Plateau of China might be simulated using appropriate models. In order to test our hypothesis and to better understanding the interaction between vegetation coverage and soil erosion, we conducted a study at watershed of Zhifanggou, a typical region of Loess Plateau. Soil erosion was negative linearly correlated with vegetation coverage ( r = 0.99***), while vegetation was mainly associated with human activities. Based on climate change, ecological stress factors and human activities, we developed a model to estimate vegetation coverage and soil erosion. Testing the model performance indicated that dynamics of vegetation coverage and soil erosion in the Loess Plateau of China could be precisely simulated. The importance of each factor in the model was also evaluated. The information of this study can be useful for better understanding the relationships between vegetation and soil erosion.

Responses of a semi-arid landscape to human disturbance: A simulation study of the interaction between rock fragment cover, soil erosion and land use change

Landscape responses to human-induced changes cannot always be studied using field monitoring and/or the analysis of sedimentological archives. Simulation models can provide additional information on the time scale and the way that landscapes respond to human interference. We present an adapted version of the SPEROS model that is subsequently used to study the interaction of water erosion, tillage erosion and rock fragment cover under various land use scenarios on semi-arid hillslopes in southeast Spain. The simulation results show that such a model, based on a relatively simple representation of erosion processes is capable of capturing the essential characteristics of rock fragments patterns in this area, i.e. a semi-logaritmic increase of rock fragment cover with slope gradient on abandoned land and a linear relationship between rock fragment cover and curvature on intensively cultivated land. The model simulations indicate that such patterns develop in a decadal time scale and that the pattern on arable land is the result of the combined action of tillage and water erosion. The model simulations also allow to assess the effects of land use changes on overall sediment production rates due to water erosion. Land abandonment leads to an exponential decline of water erosion rates and hence of sediment export over a time scale of 50–70 years. Conversion of abandoned land to intensively cultivated arable land (e.g. almond groves) will lead to a peak in water erosion, lasting again for several decades after which the water erosion rates decrease again due to the increase of rock fragment cover on the hillslope due to intensive chisel tillage. Only under the traditional system of light mouldboard tillage relatively high water erosion rates can be sustained for a long time period. The temporal and spatial patterns observed are clearly related to the interaction of water and tillage erosion: this interaction must therefore be accounted for in any long-term impact study.

Linking changes in atmospheric dust deposition, vegetation change and human activities in northwest Spain during the last 5300 years

A high-resolution, 5300-yr record of pollen and lithogenic elements (K, Ca, Ti, Rb, Sr, Y, Zr) from an ombrotrophic peat bog located in northwest Spain, reveals that the variations in the fluxes of lithogenic elements supplied to the bog by atmospheric deposition were coupled to the evolution of the vegetation of the area. A strong negative correlation exists between the percentage of tree pollen and the concentration of lithogenic elements. For example, the correlation between total tree pollen and Sr concentrations is - 0.94. The main phases of decline of the deciduous forest occurred during known cultural periods (late Neolithic, the Metal Ages, the Roman Period, the Middle Ages and the Industrial period) suggesting a close link between human activities (fires and forest clearances), changes in the vegetation and soil erosion. The flux of lithogenic elements seems to have increased before a significant variation in pollen is detected, which may indicate that changes in soil erosion are reflected earlier than the changes in vegetation in the bog record. Variations in the composition of the deposited dust reflect impacts that occurred at different spatial scales, with local sources dominant in the late Neolithic, the Metal Ages and the Middle Ages, whilst regional sources are more important in the Roman period and the Industrial Revolution. During the prehistoric period, arboreal pollen percentages recovered to their former levels, suggesting that woodland regenerated following a disturbance phase, but for the last 1400 years no significant recovery took place until afforestation with pines was introduced 200 years ago. While this must be the result of continuous clearances to convert forest into arable land, a cumulative effect on soil degradation must also be implied.

Soil erosion patterns: evolution, spatio‐temporal dynamics and connectivity

Soil erosion is among the major environmental threats related to agricultural land use in Europe. Important European policies and directives, such as the Water Framework Directive, the European Commission Strategy for Soil Protection as well as agro-environmental measures address the issues of soil erosion. During recent decades, international research has contributed greatly to an improved understanding of soil erosion processes at various scales from single plots to complex watersheds. Research focus evolved from descriptive approaches over process analyses of soil-hydrological dynamics to in depth studies of the temporal interactions of rainfall soil erosion relationships. The analysis of spatial dynamics of soil surface characteristics and runoff and erosion patterns is a recent topic of soil erosion research, which is a crucial piece of the puzzle when analysing connectivity issues and when linking upland area processes of sediment production with channel processes of sediment transport. Patterns of runoff and soil erosion represent the two-dimensional response of the landscape to rainstorm events. These patterns illustrate in a complex and yet incompletely understood way the spatial variability of important soil, land use and landscape characteristics. There has been increasing recognition of the significance of such patterns for understanding and predicting erosion and its environmental impacts. For example, improved insight into the way in which patterns of runoff and soil loss evolve over time and vary with spatial scale may help us to better comprehend the value and limitations of short-term plot studies with respect to erosion in a wider, real-landscape context. A better appreciation of the role of dynamic connectivity in runoff and sediment delivery may assist in improving our estimates and surface functions of landscape response to rainfall events. Similarly, improved understanding of patterns of aeolian erosion and deposition may facilitate prediction of wind erosion’s impacts. In the framework of the European COST action 623 ‘Soil Erosion and Global Change’ two meetings focused on recent developments in understanding the influence of spatial characteristics and patterns on the hydrological and erosion response of soils and landscapes. The first meeting was held in September 2001 in Strasbourg (France) and addressed the role of dynamic soil surface characteristics for soil erosion. Selected papers from this meeting were published in Earth Surface Processes and Landforms vol. 29 (2004). The second meeting was held at the LeibnizCentre for Agricultural Landscape and Land Use Research (ZALF) in Muncheberg (Germany) in October 2002. This meeting focused on the spatio-temporal dynamics of runoff and soil erosion patterns and related connectivity parameters at scales ranging from experimental plots to watersheds. This special issue of Earth Surface Processes and Landforms contains selected papers from this meeting. The issue opens with two papers dealing with the role of semiarid vegetation patterns for spatially structuring runoff and soil erosion at hillslope scale. The first paper gives a review of recent findings on this issue (Puigdefabregas), while the second presents a simulation approach (Boer and Puigdefabregas). Three papers deal with catchment-scale analysis, the most complex presenting a mapping approach of erosion patterns as related to agricultural land use and field organization patterns (Van Dijk et al.). The approach allows the identification of linkages between driving force patterns (land use) and pressure patterns (sediment delivery) at watershed scale. The paper by Vigiak et al. presents model comparisons with respect to their performance in predicting erosion patterns at catchment scale. Ollesch et al. describe a model adaptation to soil hydrological patterns for better predicting snowmelt erosion in catchments. The last three papers deal with small experimental approaches on laboratory or field plots. Takken et al. present an in-depth study on the role of spatial discretization of hydraulic model parameters on model results. Rejman and

POTENTIAL EFFECTS OF CLIMATE CHANGE ON RAINFALL EROSIVITY IN THE YELLOW RIVER BASIN OF CHINA

Severe soil erosion in the Yellow River basin is a significant obstruction to the sustainable management of soiland water resources. Any changes in soil erosion will have great effects on long-term planning of soil and water conservationin such a severely eroded basin. Rainfall erosivity describes the soil loss potential caused by rain, which can be expected tochange in correspondence to changes in climate. This study was conducted to assess the potential effects of climate changeon rainfall erosivity in the Yellow River basin. Two different rainfall scenarios were generated with the HadCM3 generalcirculation model for the years 2006 to 2035, 2036 to 2065, and 2066 to 2095. The statistics test showed that rainfall erosivityincreased significantly in the Yellow River basin under both scenarios for all periods in the coming decades. The erosivityincrease varied from scenario to scenario, and from period to period. Generally, increases in erosivity were less from southeastto northwest. The calculated precipitation elasticity of rainfall erosivity indicated that percent changes in rainfall erosivitywere greater than percent changes in total precipitation by a factor of 1.2 to 1.4. The expected increases in precipitationrequire that more attention will be given to soil and water conservation practices such as vegetation rehabilitation andcheck-dam construction.

Long-term erosional responses after fire in the Central Spanish Pyrenees: 1. Water and sediment yield

This paper reports the results of a study on how fire effects water and sediment losses in the Central Spanish Pyrenees where land abandonment results in an increase of the scrubland and fire-affected surfaces. In 1991, two plots (control and burnt) were installed to collect runoff, suspended sediments and solutes. One of the plots was burnt (burnt-1) and the other was covered by shrubs and herbs (control). During 1993, another burnt plot was installed (burnt-2). Data was collected from the three plots until 1999 and is used as the basis for assessing the soil erosion changes after the fire. Runoff, solute and suspended sediment concentration and erosion rates were slightly greater during the first 2 years following fire on burnt-1 compared to the control plot. The average runoff coefficients during the 8-year study period were 4.2% and 7%, the total sediment concentrations were 189 and 181 mg l −1, and the erosion rates were 89 and 143 kg ha −1 year −1 for the control and burnt-1 plots, respectively. In contrast, burnt-2 plot responded differently than burnt-1 plot to fire, although these two plots were designed to be replicated treatments. The average runoff coefficient for burnt-2 plot was two times greater than that for the control plot. Likewise, total sediment concentration was 649 mg l −1 and erosion rate was 566 kg ha −1 year −1, which are 3.6 and 4.5 times greater than the control plot. Differences between burnt and control plots were analysed at hourly, daily, monthly and yearly temporal scale. Both burned plots began to recover after the fire. However, burnt-1 plot had a recovery time of 2 years compared to burnt-2 plot; while 7 years after the fire, the runoff sediment concentration and erosion rates from burnt-2 were higher than those for the control plot. Water and sediment losses from the two burnt plots were markedly different.

Human impact on the natural environment in early colonial Australia

AbstractLittle Llangothlin Lagoon on the New England Tablelands of northeast New South Wales possesses the most detailed and best verified 210Pb chronology yet available in Australia. Recent criticisms of the length of the record are shown to be based on a faulty understanding of the principles of 210Pb dating. Attempts to revise the chronology of the lower part of the dated sequence by several decades must be rejected given that (a) fundamentally dissimilar chronological models yield ages that are statistically indistinguishable and (b) the most extreme manipulation of the modelling data fails to alter the basal dates in the profile by more than three years. The most telling criticism of the revisionist view, however, comes from the exact concordance between the dates from the basal part of the sequence, the historical date of official European contact and the massive changes in palynology, geochemistry and soil erosion resulting from that contact.The thesis that environmental disturbance immediately prior to the time of official European contact in Australia was the result of human activity is supported by a wealth of documentary evidence revealing the illegal or unsanctioned presence of Europeans throughout much of southern and eastern Australia years before official records began. Likewise, it is clear that many elements of the pre‐contact Australian environment, including certain of its soils, were fragile and susceptible to rapid and dramatic disturbance under the impact of European land use. Finally, there is convincing evidence of stable chemical and mineralogical conditions in several southeast Australian lakes throughout the last millennium or more, conditions that were altered catastrophically with the arrival of the first Europeans and their stock.

Relative influence of wildfire on soil properties and erosion processes in different Mediterranean environments in NE Spain

Abandonment of terraced soils and increased brushland cover has increased wildfire occurrence to almost an annual rate in the Cap de Creus Peninsula, NE Pyrenees Range, Province of Girona, Spain. A wildfire occurred in August 2000 and affected an area of 6760 ha of shrubs and cork trees, whereas still cultivated plots were only slightly affected. Five stations of erosion measurements, corresponding to five different environments (from present cultivation to late abandonment) were destroyed by the passage of fire, and were promptly replaced to allow to monitoring post-fire effects on soil erosion. Selected soil properties were determined monthly before the fire and during 6 months after the fire at a monthly rate. Runoff and sediment yield together with dissolved organic carbon (DOC) in runoff water and organic carbon losses in eroded sediments (EOC) were evaluated throughout 2000. The last stage of abandonment, stands of cork trees, had the highest soil stability. Nevertheless, evidence of unfavourable soil conditions was detected at the shrub stage, when Cistus monspeliensis cover was the dominant opportunistic plant. This stage was considered to be a critical threshold leading either to degradation or regeneration processes according to fire frequency. A drastic change in soil properties, erosion and nutrient depletion occurred after the fire in all the environments. Statistics enabled to state that environments differed significantly in main soil properties. By statistically comparing the measured variables between the environments before and after the fire, DOC was found to be the soil parameter showing the highest significance between environments. Absolute values of erosion were low with respect to other Mediterranean environments although the shallow nature of these soils might deserve special attention because of a comparatively higher risk of degradation.

Relative influence of wildfire on soil properties and erosion processes in different Mediterranean environments in NE Spain

Abandonment of terraced soils and increased brushland cover has increased wildfire occurrence to almost an annual rate in the Cap de Creus Peninsula, NE Pyrenees Range, Province of Girona, Spain. A wildfire occurred in August 2000 and affected an area of 6760 ha of shrubs and cork trees, whereas still cultivated plots were only slightly affected. Five stations of erosion measurements, corresponding to five different environments (from present cultivation to late abandonment) were destroyed by the passage of fire, and were promptly replaced to allow to monitoring post-fire effects on soil erosion. Selected soil properties were determined monthly before the fire and during 6 months after the fire at a monthly rate. Runoff and sediment yield together with dissolved organic carbon (DOC) in runoff water and organic carbon losses in eroded sediments (EOC) were evaluated throughout 2000. The last stage of abandonment, stands of cork trees, had the highest soil stability. Nevertheless, evidence of unfavourable soil conditions was detected at the shrub stage, when Cistus monspeliensis cover was the dominant opportunistic plant. This stage was considered to be a critical threshold leading either to degradation or regeneration processes according to fire frequency. A drastic change in soil properties, erosion and nutrient depletion occurred after the fire in all the environments. Statistics enabled to state that environments differed significantly in main soil properties. By statistically comparing the measured variables between the environments before and after the fire, DOC was found to be the soil parameter showing the highest significance between environments. Absolute values of erosion were low with respect to other Mediterranean environments although the shallow nature of these soils might deserve special attention because of a comparatively higher risk of degradation.

Soil erosion and soil properties in reclaimed forestland of loess hilly region

Based on data observed from 1989 to 1998 in the Ziwuling survey station, changes of soil erosion and soil physico-mechanical properties were studied after forestland reclamation. When the man-induced factors changed the eco-environment by reclaiming forestlands, the intensity of man-made soil erosion in reclaimed lands was 1,000 times more than that of natural erosion in forestlands. From the analysis of soil physical and mechanical properties, the clay content and physical clay content decreased 2.74% and 3.01% respectively, and the >0.25 mm water stable aggregate content decreased 58.7%, the soil unit weight increased and the soil shear strength decreased, all of which were easier to cause soil erosion. The results of the correlation analysis showed that the >0.25 mm water stable aggregate content was the greatest influencing factor on soil erosion, the partial correlated coefficient was 0.9728, and then were soil coarse grain and soil shear strength, the partial correlated coefficients being 0.8879 and 0.6020 respectively. The relationships between the >0.25 mm water stable aggregate content, the soil sheer strength and the soil erosion intensity were analyzed, which showed that the first and seventh years were the turning years of the soil erosion intensity after the forestland reclamation. The degenerative eroded soil and eco-environment formed the peculiar erosion environment, which aggravated the soil erosion rapidly.

Influence of Long‐term Cropping Systems on Soil Physical Properties Related to Soil Erodibility

Crop rotations and manure application are thought to alter soil quality. This study was conducted to quantify the effects of over 100 yr of continuous crop management and annual manure applications on selected soil physical properties at Sanborn Field, Columbia, MO. Intact soil cores (76 mm i.d. by 76 mm) were collected from continuous corn (Zea mays L.), continuous wheat (Triticum aestivum L.), continuous timothy (Phleum pratense L.), and a rotation of corn–wheat–red clover (Trifolium pratense L.). The soil was Mexico silt loam (fine, smectitic, mesic, Aeric Vertic Epiaqualfs). Soil was tested throughout a 1‐yr period for aggregate stability, single‐drop rainfall splash detachment, and soil shear strength. Cropping systems affected aggregate stability (P < 0.01), soil strength (P < 0.01), and splash detachment (P < 0.01), but not bulk density. Continuous cropping to timothy produced soil that had three to four times greater aggregate stability, 21 to 27% greater soil strength, and 55 to 67% less soil splash compared with continuous wheat or continuous corn. Season significantly affected all measured soil properties, but the effect was inconsistent. The highest aggregate stability was found during July for all treatments. Splash detachment was more sensitive to cropping systems than other soil measures, and thereby the best measure for evaluating changes in soil erodibility. Cropping and soil management that accumulate plant residues can improve soil quality by increasing soil aggregate stability, shear strength, and resistance to splash detachment.

An early Holocene erosion phase on the loess tablelands in the southern Loess Plateau of China

A Holocene loess profile to the west of Xi'an China was studied multi-disciplinarily to investigate the relationships between soil erosion and monsoonal climatic change. The proxy data obtained from this aeolian loess and palaeosol sequence indicate large-scale variations of climate in the southern Loess Plateau since the last glaciation. A rainwash bed, indicative of a wetter climate, excessive runoff and erosion on the loess tablelands, was identified relating to the early Holocene before the onset of the “climatic optimum”. This is synchronous with the early Holocene physiographic erosional stage identified in the valleys in North China. It means that severe erosion took place when the region was undergoing climatic amelioration during the early Holocene. The evidence presented in this paper shows that the erosion occurred as a regional response to a monsoonal climatic shift in the southern Loess Plateau. During the last glaciation, prior to the erosion phase, the land surface on the tablelands had been largely stable except for the rapid accumulation of aeolian dust and the resultant increase in its elevation. Relatively slow dust accumulation and intensive bio-pedogenesis responding to the Holocene “climatic optimum” followed the erosion phase. The loess tablelands were most vulnerable to erosion during the large-scale monsoonal climatic shift from dry-cold glacial to humid-warm post-glacial conditions in the southern Loess Plateau.

Retarded wetland succession: anthropogenic and climatic signals in a Holocene peat bog profile from north‐east Hungary

Summary 1 Pollen, plant macrofossil and humification data supplemented by chemical and physical analyses of a Holocene peat sequence from Nagymohos, Kelemer, north-east Hungary, have been used to study local wetland vegetation dynamics and upland vegetation development in the early and mid Holocene. An attempt was made to distinguish between autogenic successional processes and allogenic environmental forces. 2 Holocene sedimentation began c. 7500 cal. bc. The basin was occupied by a shallow open lake with substantial input of inorganic material until c. 6200 cal. bc, when floating reedswamp vegetation encroached on the lake surface. This turned to Carex fen within c. 100 years. Sphagnum transitional bog became established by c. 5300 cal. bc. 3 The local mire water table in the Sphagnum bog phases was elevated between c. 5700–6000 cal. bc, c. 5000–5250 cal. bc and c. 4500–4700 cal. bc. The most distinctive feature of the record is the coincidence of upland vegetation changes with reconstructed wet-shifts in mire hydrology. The upland pollen data imply selective exploitation of Ulmus and Corylus coupled with burning and soil erosion during the second and third wet periods. 4 Succession from shallow open lake to Sphagnum-bog is an autogenic process, although superimposed allogenic perturbation (human induced soil erosion and climate change) modified the expected progression from wetter to drier and from minerotrophic-water dependent to oligotrophic communities.

Effects of land use and eventual fire on soil erodibility in dry Mediterranean conditions

The Mediterranean countries of Europe have suffered deep land-use transformations during this century and the expansion of wildfires after generalized land abandonment in the marginal uplands. Differences in soil properties due to land use may lead to different responses of the ecosystem in case of fire. We analyze how soil erodibility in a cropland and oldfields of different age after abandonment (bushland, shrubland and pine forest) would be affected by wildfire. Soil samples taken in each land use were analyzed to characterize soil erodibility. From fuel load measures, the range of temperatures to be attained in case of a fire were estimated for the topsoil. From these temperatures and from the information available in the literature, we predicted the changes in soil properties produced by the fire and estimated soil erodibility for the burned lands. Changes in soil erodibility were slight in the field crop with low fuel load, and increased according to biomass and forest floor accumulation. As the initial soil erodibility was inversely related to fuel load, the fire would increase the values of soil erodibility of the different land uses up to close to those of the field crop. In addition, the fire would produce very similar soil erodibility values for the different land uses, and therefore a homogenizing post-fire soil response in the landscape.

Soil recovery from track construction and harvesting changes in surface infiltration, erosion and delivery rates with time

The effects of timber harvesting activities are often characterised by significant changes in surface soil properties, runoff production and erosion rates. Here we quantify trends in surface soil recovery following timber harvesting activities, specifically snig track (skid trail) construction and logging, based on changes in soil surface compaction, infiltration, and erosion with time since initial disturbance. Sites range in age from 0.5 to 5 years. Surface erosion on the snig tracks and general harvesting areas (GHA), and sediment storage and delivery between the two areas, are measured using a large rainfall simulator. Surface soil compaction shows no significant recovery over this time period, illustrating the persistent effects of machinery compaction on surface soil structure. In contrast, surface infiltration rates on the snig tracks increase by a factor of two and snig track erosion rates decline by almost one-order of magnitude over the 5-year period. These findings have important implications for assessing the cumulative impact of timber harvesting activities.