Semi-arid Landscapes Research Articles

Implications from the Use of Non-timber Forest Products on the Consumption of Wood as a Fuel Source in Human-Dominated Semiarid Landscapes.

Little is known about what possible effects on wood resources might be caused by non-timber forest products (NTFPs). Here, we assessed the patterns of fuelwood consumption related to an NTFP (Caryocar coriaceum) oil extraction and how this non-domestic activity can indirectly increase the use pressure on fuelwood species in a protected area, semiarid of Brazil. We conducted semi-structured interviews, in situ inventories, phytosociological surveys, and analyses of wood quality to identify the set of woody plants used in oil production. Householders use large volumes of dry wood and a set of woody species, which are highly exploited. Additionally, many preferred species have low fuel potential and suffer much use pressure. The best fuelwood species are underused, what requires management strategies to improve their potential as a source of energy. As a result, we suggest some conservation and management actions of fuelwood resources related to the use of NTFPs.

Evaluating management-induced soil salinization in golf courses in semi-arid landscapes

Abstract. Site-specific information on land management practices are often desired to make better assessments of their environmental impacts. A study was conducted in Lubbock, Texas, in the Southern High Plains of the United States, an area characterized by semi-arid climatic conditions, to (1) examine the potential management-induced alterations in soil salinity indicators in golf course facilities and (2) develop predictive relationships for a more rapid soil salinity examination within these urban landscape soils using findings from a portable X-ray fluorescence (PXRF) spectrometer. Soil samples were collected from managed (well irrigated) and non-managed (non-irrigated) areas of seven golf course facilities at 0–10, 10–20, and 20–30 cm depths and analyzed for a suite of chemical properties. Among the extractable cations, sodium (Na) was significantly (p < 0.05) higher in the managed zones of all the golf facilities. Soil electrical conductivity (EC), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR), parameters often used in characterizing soil salinity and sodicity, were for the most part significantly (p < 0.05) higher in the managed areas. Water quality reports collected over a 22-year period (1991–2013, all years not available) indicated a gradual increase in pH, EC, SAR, total alkalinity, and extractable ions, thus supporting the former findings. Findings from the PXRF suggested possible differences in chemical species and sources that contribute to salinity between the managed and non-managed zones. PXRF-quantified Cl and S, and to a lesser extent Ca, individually and collectively explained 23–85% of the variability associated with soil salinity at these facilities.

Sources of variability in livestock water quality over 5 years in the Northern Great Plains.

Concentrated dissolved minerals in naturally occurring water accessible to livestock grazing semiarid landscapes can negatively influence animal productivity and well-being. Twelve indicators of water quality (Ca, Cl, Fe, F, Mg, Mn, Na, nitrate N, pH, SO4, total dissolved solids [TDS], and temperature) were measured at 45 livestock water sites over 5 yr from 2009 through 2013 at the 22,257-ha USDA-ARS Fort Keogh Livestock and Range Research Laboratory (Miles City, MT) to estimate variation. Water was sampled from 4 sources: 1) flowing surface water, 2) groundwater, 3) reservoirs, and 4) springs. The sampled area was classified by 3 cardinal compass bearings (locations): 1) north, 2) southeast, and 3) southwest of the Yellowstone River. Samples were collected twice yearly in 2 seasons, May (wet) and September (dry). Year, location, source, and season and their interactions were analyzed as a 5 × 3 × 4 × 2 factorial arrangement of treatments. A location × year interaction (P < 0.04) was found for Mg, Na, SO4, and TDS. The southwest location had the greatest concentrations in 2012 of Na, SO4, and TDS. A source × year interaction (P < 0.02) was found for Ca, Fe, F, Mg, Mn, Na, SO4, TDS, and temperature. Iron, Mg, and Mn had the greatest concentrations in flowing surface water in 2012. Greater and then lower precipitation in 2011 followed by below-average precipitation in 2012 was associated with elevated mineral concentrations in sources in the southwest location and flowing surface water sources demonstrating sources of water quality variability within time and space at the study site. Average concentrations of Ca, Cl, Mg, and nitrate N and pH levels across sources and locations did not exceed the upper maximum intake level for beef cattle. In contrast, concentrations of F, Fe, Na, SO4, and TDS at times exceeded the upper maximum level for beef cattle, indicating these minerals may negatively impact range beef cattle performance.

Soil survey data rescued by means of user friendly soil identification keys and toposequence models to deliver soil information for improved land management

In many countries there is a large source of soil survey information that could be used to guide land management decision. This soil information is commonly undervalued and underused, because it is usually not in a user-friendly format that non-soil specialists who generally make land management decisions can readily apply, nor are soil specialists always immediately available to conduct the interpretation required.The aim of this work was to develop an approach to convey soil survey information by means of special-purpose soil classifications and conceptual toposequence models in order to improve land management decisions. The approach: (i) salvages and reinterprets valuable soil survey legacy data from the plethora of detailed published soil survey technical reports and their numerous appendices of quantitative and qualitative data, and (ii) delivers complex or intricate soil survey information to non-soil specialists using a vocabulary and diagrams that they can understand and have available to apply when they need it.To illustrate the wide applicability of this approach, case studies were conducted in three different parts of the world – Kuwait, Brunei, and Australia, each of which exhibit vastly different landscapes, climates, soil types and land use problems. Pedologists distilled published soil survey information and identified a limited set of soil properties related to landscape position which enabled non-soil specialists to determine soil types by following user-friendly approach and format. This provides a wider audience with information about soils, rather than always relying on a limited number of soil specialists to conduct the work.The details provided in the case studies are applicable for the local area that they were prepared for. However, the structured approach developed and used is applicable to other locations throughout the world outside of: (i) Brunei, especially in tropical landscapes, (ii) Kuwait, especially in arid and semi-arid landscapes and (iii) Australian winter rainfall landscapes, especially in Mediterranean landscapes – in order to establish similar local classifications and conceptual models.

The relationship between the spread of the Catholic Church and the shifting agro-pastoral line in the Chahar Region of northern China

The Great Wall of China roughly follows a transition belt between subhumid region and arid/semiarid region, often thought of as a boundary between agricultural and pastoral area. However, in the mid-18th century, the farming activity began to cross the Great Wall and infiltrate the pastoral region. The agro-pastoral line moved substantially northwards and westwards resulting in a changing landscape beyond the Great Wall. The Catholic Church, which had been proselytizing in Inner Mongolia since the turn of the 18th century, played an important role in this historical process. This paper evaluates the role of Catholic churches in this shift of the agro-pastoral line in Chahar Region in the 19th century.Chahar, a semi-arid region in the southeastern Mongolia Plateau, had a significant Catholic activity after 1700s. As congregation obtained land from the Mongols, missionaries converted local Han Chinese to Catholicism while lending land, housing and farm implements. By 1952 most people living there had been converted. As a result of intensive land management by the Catholic missions, the semiarid landscapes, formerly used for grazing lands, were changed to more intensive agricultural use. This study examines the important role of the practices of an authoritarian religious organization on the movement of the agro-pastoral line and the relationship between those religious missions and environmental change. This study shows that when the missionaries began preaching to the impoverished Han people coming from within the Great Wall rather than the local Mongols of the Chahar Region, increasing numbers of Han Catholic villages appeared beyond the Great Wall, cultivating what used to be grazing land. Meanwhile, to manage these Han people, the local administrative system was transformed from the Meng-Banner system into Banner-county system. As the name suggests, this latter system was based on Mongol-controlled Banners and Han-controlled counties. Thus the boundary between Banner and county hints at the movement of the agro-pastoral line. By tracking this movement we found that the agro-pastoral line in Chahar region shifted in the late Qing Dynasty. Meanwhile, Catholic villages became more concentrated in the counties, indicating that the Catholic Church had played an important role in this movement of the agro-pastoral line.

The role of vegetation–microclimate feedback in promoting shrub encroachment in the northern Chihuahuan desert

Many arid and semi-arid landscapes around the world are affected by a shift from grassland to shrubland vegetation, presumably induced by climate warming, increasing atmospheric CO2 concentrations, and/or changing land use. This major change in vegetation cover is likely sustained by positive feedbacks with the physical environment. Recent research has focused on a feedback with microclimate, whereby cold intolerant shrubs increase the minimum nocturnal temperatures in their surroundings. Despite the rich literature on the impact of land cover change on local climate conditions, changes in microclimate resulting from shrub expansion into desert grasslands have remained poorly investigated. It is unclear to what extent such a feedback can affect the maximum extent of shrub expansion and the configuration of a stable encroachment front. Here, we focus on the case of the northern Chihuahuan desert, where creosotebush (Larrea tridentata) has been replacing grasslands over the past 100-150years. We use a process-based coupled atmosphere-vegetation model to investigate the role of this feedback in sustaining shrub encroachment in the region. Simulations indicate that the feedback allows juvenile shrubs to establish in the grassland during average years and, once established, reduce their vulnerability to freeze-induced mortality by creating a warmer microclimate. Such a feedback is crucial in extreme cold winters as it may reduce shrub mortality. We identify the existence of a critical zone in the surroundings of the encroachment front, in which vegetation dynamics are bistable: in this zone, vegetation can be stable both as grassland and as shrubland. The existence of these alternative stable states explains why in most cases the shift from grass to shrub cover is found to be abrupt and often difficult to revert.

Aspect reduces soil moisture and tree cover, but not nitrogen mineralization or grass cover, in semiarid pinyon-juniper woodlands of the Southwestern United States

Global climate change is expected to increase the aridity of semiarid landscapes by increasing heat stress and decreasing soil moisture, negatively impacting plant survival, growth, and reproduction and forcing major shifts in plant community composition. To better understand potential vegetation shifts, we investigated how aspect-mediated differences in soil moisture and nitrogen influence tree-grass and tree species coexistence in pinyon-juniper woodlands in the southwestern United States (at the Sevilleta Long Term Ecological Research Station in New Mexico). We measured soil moisture, total mineralized soil nitrogen, grass cover, and woody cover and demography of the two dominant trees—two-needle pinyon pine (Pinus edulis) and one-seeded juniper (Juniperus monosperma)—along 32 transects on north-facing and south-facing slopes. Tree cover was greater on north-facing than on south-facing slopes, reflecting significantly higher soil moisture on northern aspects. Aspect did not affect soil nitrogen or grass cover. Population structure for juniper was influenced by aspect while reproductive output was influenced by aspect in both species, suggesting that differences in drought tolerance between these codominant tree species may be responsible for differences in the utilization of resources in our study area. Our results suggest that soil moisture can affect tree cover and tree-grass coexistence more than does nitrogen. Increasing aridity due to global climate change is likely to decrease woody cover in semiarid landscapes, resulting in systems codominated by grasses and woody species.

Restoration of riparian areas following the removal of cattle in the northwestern great basin.

We assessed the effects of the elimination of livestock in riparian systems at Hart Mountain National Antelope Refuge in southeastern Oregon, 23 years after the removal of cattle grazing, using 64 photos taken before grazing was removed compared with later retake photos. Two methods were used for this assessment: (1) a qualitative visual method comparing seven cover types and processes and (2) a new quantitative method of inserting digital line transects into photos. Results indicated that channel widths and eroding banks decreased in 64 and 73% of sites, respectively. We found a 90% decrease in the amount of bare soil (P < 0.001) and a 63% decrease in exposed channel (P < 0.001) as well as a significant increase in the cover of grasses/sedges/forbs (15% increase, P = 0.037), rushes (389% increase, P = 0.014), and willow (388% increase, P < 0.001). We also assessed the accuracy of the new method of inserting digital line transects into photo pairs. An overall accuracy of 91% (kappa 83%) suggests that digital line transects can be a useful tool for quantifying vegetation cover from photos. Our results indicate that the removal of cattle can result in dramatic changes in riparian vegetation, even in semi-arid landscapes and without replanting or other active restoration efforts.

Contemporary aeolian morphogenesis in semiarid landscapes of the intermountain depressions of Southern Siberia

This article studies the modern long-term variability in the intensity of aeolian morphogenesis in semiarid regions of Southern Siberia. The results of long-term station-based monitoring of aeolian processes are presented. The coherence of intensity fluctuation of atmospheric humidity and fluctuation of inland lakes is traced. Pulsating character of aeolian processes due to climate cycles of atmospheric moisture is presented.The increasing role of deflation in the modern morphogenesis is revealed. Much attention is paid to catastrophic aeolian processes. The interaction of aeolian and fluvial processes, forming a special mechanism of denudation and substance moving, and also being characteristic for the subarid foothill of the northern periphery of the South-Siberian mountain belt, is considered. Spatial ordering of aeolian processes within a regional subsystem of a unified aeolian substance cycle in Central Asia is presented.

Erratum to: Refining landscape contexts for open-air, Lower and Middle Paleolithic sites: a case study from Muthanna Province, Southern Iraq

Open-air Paleolithic sites in desert and semiarid landscapes provide interpretive quandaries because of the absence of depositional matrices and stratigraphic controls. This paper argues that datable and stratified vertical contexts may be preserved in the vicinity of open-air artifact scatters. These, in turn, may account for paleo-environmental conditions that would have attracted Paleolithic groups. The site in question is in the Southern Iraqi desert, a locale heretofore terra incognita for early hominin activity. Optically stimulated luminescence (OSL) dates were taken from ancient spring and dune deposits in a depression flanking the hamada surfaces on which the artifact distributions were found. Geochemical and granulometric studies were used to reconstruct the depositional histories of the spring locale, and the dates were projected onto contemporary oxygen isotope curves that serve as proxies for the climatic cycles operational across the greater Near East. The advent of OSL dating provides a new window for dating events and environments linked to Paleolithic chronologies. The locations of surface scatters may signify preservation of nearby micro-environments which could be proxies for structuring landscape and occupational chronologies.

Spatial variation, mapping, and classification of moss families in semi-arid landscapes in NW Turkey.

Geostatistics and remote sensing techniques are frequently used in analyzing the spatial variability of terrestrial ecosystems. We analyzed spatial variation of moss families by geostatistics and Landsat imagery in a typical semi-arid landscape in North Central Anatolia, Turkey. We sampled 49 sites, chosen based on elevation, slope steepness, and slope aspect. Moss families were determined in a 10-m(2) representative area at each sampling site. The samples were transported to a laboratory and identified for moss families. In total, 10 families were found. Semivariogram analysis was performed to analyze the spatial structure of these families. The semivariogram analysis showed that the moss families were spatially dependent within 117 m in the study area. Thirteen thematic classes were categorized by Landsat Thematic Mapper (TM) image in the study area. The classification resulted in an overall kappa statistic of 0.8535, producer accuracy of 74.29, and user accuracy of 86.67. The family with the lowest classification accuracy was Orthotrichaceae (kappa of 0.6379, producer accuracy of 64.52, and user accuracy of 66.67). The moss families and the other classes were identified with a 0.78 kappa statistic value and an 80.74 % accuracy level by using the Landsat TM. The classification showed that Brachytheciaceae, Pottiaceae, Bryaceae, and Grimmiaceae were the most abundant moss families in this semi-arid environment.

Develop energy from shale with local ecosystems in mind

In South Africa, there currently are plans to develop shale-based gas extraction in arid and semi-arid landscapes of the Karoo. The extraction of gas from shale in the Karoo through hydraulic fracturing, also known as 'fracking', remains a contentious issue, with stakeholders often criticised for not being forthright in their reporting of the possible risks to local water resources. Indeed, what I find the most striking among all the debate and polemical essays is how very few scientific reports there are on the possible local effects of fracking on the native Karoo biota.

Hydropedological Assessments of Parcel-Level Infiltration in an Arid Urban Ecosystem

Soil morphology and correspondent hydrologic data can contribute to qualifying and quantifying urban soil suitability and capacity to cycle stormwater runoff. We put particular emphasis on the possibility that residential parcels may manage their own stormwater on pervious yard areas. We assessed the morphology of Aridisol pedons (as deep cores to approximately the 3.6-m depth) via soil taxonomy, performed in situ measurements of infiltration, and measured subsoil hydraulic conductivity in two desert parks, four residential parcels, and three dual-purpose park–stormwater retention basins in the Phoenix, AZ, metropolitan area. Infiltration rates overall ranged between 0.4 and 1.7 cm h⁻¹. We used borehole hydraulic conductivity as a proxy for drainage, which ranged from a low of 0.0 to 13 cm h⁻¹. Representing a baseline, or set of “natural” hydrologic processes, native desert sites exhibited a relatively high capacity to infiltrate and redistribute rainfall, which, depending on storm intensity, may drain to washes or ephemeral streambeds via subsurface runoff. Simulations of stormwater runoff on residential parcels showed that when rooftop runoff is directed to pervious patches, rainfall is entirely infiltrated and redistributed, which predicts good potential for parcel-level stormwater management. Our observation of an accumulation of fine sediments in retention basin surface soils was corroborated with local observations that drawdown times in the retention basins had increased with time. Although further assessment is needed on a wider variety of semiarid landscapes, our results suggest a positive role for residential parcels in detaining stormwater on site and perhaps easing the wet-weather burden on centralized stormwater infrastructure in semiarid urban ecosystems.

Effect of land degradation on carbon and nitrogen pools in two soil types of a semi-arid landscape in West Africa

To determine the resilience of soil organic C and N pools during land degradation processes in a semi-arid landscape of West Africa, we compared the magnitude of soil organic C and N differences in bulk soil and aggregate fractions between contrasting types of land cover (degraded land and native land cover) and soil (Luvisols and Cambisols). We analyzed the following soil key indicators: CEC, soil respiration, C and N contents, and δ13C and δ15N signatures of soil organic C.The average CO2 respired from native land cover was at least 82% higher than its value from degraded land cover and was significantly higher in Luvisols than in Cambisols. Likewise, the soil organic C and N contents in bulk soil were significantly affected by land cover and soil contrasts. The average C loss in bulk soil from degraded land cover was equivalent to 49% in Cambisols and 54% in Luvisols. In both soil types, all aggregate fractions were sensitive to land degradation processes and the C loss decreased from macroaggregates to the clay+silt fraction. Compared to the native land cover, organic C loss from the macroaggregates in degraded land cover was 92% and 84%, respectively, in Cambisols and Luvisols. The soil type affected significantly the C content only in the clay+silt fraction. The C/N ratio of finer fractions (microaggregates and clay+silt) was significantly higher in degraded land cover than in native land cover, indicating greater losses of N than C during land degradation processes. The differences of δ13C signatures throughout C pools between the two types of land cover suggest a relative dominance of C3 derived C in macroaggregates and C4 derived C in the clay+silt fraction in the degraded lands. The reduction of soil respiration and the rapid N loss in degraded land cover slowed down the humification processes of C3 plant derived materials which were effectively dominant in macroaggregates.

Artificial rainfall tests, soil moisture profiles and geoelectrical investigations for the estimation of recharge rates in a semi-arid area (Jordanian Yarmouk River Basin)

To overcome the limitations posed by the limited relevant data for recharge estimation in the Jordanian Yarmouk River basin, a mass balance methodology is developed which is simple and may be easily applied to other arid and semi-arid landscapes. This is done by integrating available climatic data with new rain–runoff relationship data, as measured using a specially designed and built artificial rainfall simulator, and changing soil moisture profiles through the hydrological year, as measured in the field. The amount of moisture in the soil after rainfall events changes as a result of both evaporation and of drainage into deeper levels (recharge). The soil moisture profiles at depth are evaluated using geophysical techniques that allow for the tracking of recharge fronts. After rainfall events, the distribution of its fate between runoff, evaporation and recharge is determined. Water in the soil beyond the field capacity can be demonstrated to mostly contribute to the ultimate groundwater recharge in the area. Water stored beyond the permanent wilting point is not considered to contribute significantly to the recharge regime. Because of the irregular nature of rainfall, the amount of recharge is found to be related to the spacing of wet and dry spells during the winter months more than the actual amount of rainfall. Prolonged dry periods allow for excess water to drain into the deeper soil and thus to the groundwater, and thus allow for more uptake following subsequent rainy events. Evaporation does not significantly contribute to the drying of the soils. Reanalysis of rainfall and evaporation data from previous years suggests that recharge rates range from 20 to 37 % of total rainfall amounts, as opposed to the currently assumed 5 %.

“Nothing but land”: Women’s Narratives, Gardens, and the Settler-Colonial Imaginary in the US West and Australian Outback

This essay applies ecocriticism, informed by a transnational, settler-colonial theory, to a comparative analysis of texts by three US and three Australian women authors. Through an examination of both “wild” and domestic landscapes, the essay works to establish how these authors manifest the “settler-colonial imaginary” through their glorification of the process of establishing English-style gardens on homesteads founded in territory depicted as an “ un land.” The essay reads the insistent use of a “nothing but” construction in descriptions of uncultivated land in both the Australian and US texts as signifying the literary imagining of the “ un land” of the colonized territory, a discursive clearing of the land, as it were, to make room for settlement. From there, it proceeds to compare and contrast the different ways in which these texts imagined settlers’ occupation of land as an ecological struggle to wrest an arid or semi-arid landscape into a space amenable for the production of an English garden—the symbol of the settler-colonial project’s ultimate success. It then discusses texts by settler women in both Australia and the United States that imagine settlement in a more ecologically sustainable way, signaling a potential “counter-colonial” gesture of reconciliation with place.

Development of a Framework for Predicting Incident Probabilities of All Terrain Vehicle Use Across a Semi-Arid Landscape

Recreational All-Terrain Vehicle (ATV) activities can fulfill people’s needs in physical, mental, and spiritual well-being, as well as provide significant economic contributions to local jurisdictions. Nevertheless, ATV use creates multiple environmental issues ranging from air and water pollution to soil erosion. Accurately forecasting the incidence locations of ATV activities helps to form the foundation for robust environmental management and conservation intervention. However, drivers’ behavioral patterns have rarely been investigated within a geospatial context to enhance forecasting ability. This paper presents a novel process for estimating occurrence probability of ATV activities in a landscape near Las Cruces, New Mexico, USA, based on a 5 m-resolution web that unifies information extracted from the applications of remote sensing and GIS technologies. The model is composed of three major aspects: object-based classification and validation for the generation of the trail inventory, parameterization, and logistic regression analysis. Rider behavioral patterns were parameterized by quantifying the relationship embedded in the interactions between riders and the terrain. The model outcomes were then analyzed to portray riding patterns in responding to landscape features. The analyses demonstrated that the involvement of riding patterns, such as tailing of ridge branches and previous disturbances, generated significant results. The application of the Area under the Receiver Operating Characteristics Curve (AUROC) validation technique results in an accuracy value greater than 0.8. Accurately foreseeing the spatial distribution of possible newly formed places for ATV activities will facilitate the inauguration of sound recreational policies, which in turn reduces ATV impacts on environments and retains welfare of non-motorized tourists.

Machine learning for predicting soil classes in three semi-arid landscapes

Mapping the spatial distribution of soil taxonomic classes is important for informing soil use and management decisions. Digital soil mapping (DSM) can quantitatively predict the spatial distribution of soil taxonomic classes. Key components of DSM are the method and the set of environmental covariates used to predict soil classes. Machine learning is a general term for a broad set of statistical modeling techniques. Many different machine learning models have been applied in the literature and there are different approaches for selecting covariates for DSM. However, there is little guidance as to which, if any, machine learning model and covariate set might be optimal for predicting soil classes across different landscapes.Our objective was to compare multiple machine learning models and covariate sets for predicting soil taxonomic classes at three geographically distinct areas in the semi-arid western United States of America (southern New Mexico, southwestern Utah, and northeastern Wyoming). All three areas were the focus of digital soil mapping studies. Sampling sites at each study area were selected using conditioned Latin hypercube sampling (cLHS). We compared models that had been used in other DSM studies, including clustering algorithms, discriminant analysis, multinomial logistic regression, neural networks, tree based methods, and support vector machine classifiers. Tested machine learning models were divided into three groups based on model complexity: simple, moderate, and complex. We also compared environmental covariates derived from digital elevation models and Landsat imagery that were divided into three different sets: 1) covariates selected a priori by soil scientists familiar with each area and used as input into cLHS, 2) the covariates in set 1 plus 113 additional covariates, and 3) covariates selected using recursive feature elimination.Overall, complex models were consistently more accurate than simple or moderately complex models. Random forests (RF) using covariates selected via recursive feature elimination was consistently the most accurate, or was among the most accurate, classifiers between study areas and between covariate sets within each study area. We recommend that for soil taxonomic class prediction, complex models and covariates selected by recursive feature elimination be used.Overall classification accuracy in each study area was largely dependent upon the number of soil taxonomic classes and the frequency distribution of pedon observations between taxonomic classes. Individual subgroup class accuracy was generally dependent upon the number of soil pedon observations in each taxonomic class. The number of soil classes is related to the inherent variability of a given area. The imbalance of soil pedon observations between classes is likely related to cLHS. Imbalanced frequency distributions of soil pedon observations between classes must be addressed to improve model accuracy. Solutions include increasing the number of soil pedon observations in classes with few observations or decreasing the number of classes. Spatial predictions using the most accurate models generally agree with expected soil–landscape relationships. Spatial prediction uncertainty was lowest in areas of relatively low relief for each study area.

Fluvial sediments of the Algeti River in southeastern Georgia — An archive of Late Quaternary landscape activity and stability in the Transcaucasian region

In order to obtain information about landscape activity and stability during the Late Quaternary in the Transcaucasian region, fluvial sediments of the lower Algeti River in SE-Georgia were studied by means of geomorphologic, sedimentologic and geochronologic methods. These investigations show that sediments aggraded by the Late Pleistocene braided Algeti River were strongly incised around the Pleistocene/Holocene transition, and subsequently a small-scale pattern of diachronous fluvial terraces deposited by the now meandering river developed in the new valley during the Holocene. Prior to ca. 3cal.kaBP, active phases of river channel aggradation and overbank sedimentation about 6cal.kaBP and 3.4–3.2cal.kaBP can be linked with climate-driven vegetation changes, i.e. stronger fluvial dynamics with sedimentation occurred during more arid and colder periods whereas the Caucasian Holocene climate optimum between 6 and 3.4cal.kaBP was characterized by stable geomorphologic conditions. After 3cal.kaBP, strongly increased human impact documented by former pollen studies is reflected by the fluvial dynamics as well, i.e. an activity phase of strong overbank sedimentation 2.7–2.1cal.kaBP occurred during a period when forests in the Lesser Caucasus were burnt down. Two subsequent activity phases with fluvial sedimentation can be linked with historic events that probably both influenced vegetation distribution of the region, i.e. a period of flourishing of Georgia during the Middle Age and a time of large-scale destruction of the country due to a Persian invasion at the end of the 18th century AD, respectively.Thus, whereas no influence of tectonic events or fluctuations of the Caspian Sea level on the fluvial dynamics could be detected, SE-Georgia shows its fragile character with respect to climate- and human driven vegetation-changes similar to other semi-arid landscapes of the Mediterranean region.

Soil type mediates effects of land use on soil carbon and nitrogen in the Konya Basin, Turkey

ObjectiveThe goal of this study was to test for the effects of land use and soil type on soil organic carbon (SOC) and total soil nitrogen (N) stocks in an arid region with a long history of cultivation and animal husbandry. Arid to semi-arid landscapes cover a large proportion of the Earth's surface and are sensitive to agricultural intensification and projected changes in climate, yet data on landscape controls on SOC and N remain scarce. MethodsWe used a state factor approach to study the effects of soil type and land use on surface SOC and total soil N (0–25cm) across 35 sites in a 200km2 area in the Konya Basin, an important agricultural region of Turkey. Using Landsat-based land cover maps, we identified three representative land uses – annual-crop agriculture, orchards and grazing lands – stratified across Aridisols formed on three different parent materials: alluvial clay-loam, lacustrine clay and terrace sandy loam soils. ResultsSOC and N stocks depended strongly on soil type with strong interactions between soil type and land use. On alluvial soils, grazing land SOC and N stocks were 37% and 23% greater, respectively, than those of agricultural sites and 63% and 50% greater than at orchard sites. In contrast, agricultural sites on lacustrine soils contained 41% more SOC and 42% more soil N. There were no land use effects on terrace soils. The vertical distribution in SOC and N within the top 25cm, representing the plow layer in the agricultural sites, differed by soil type and land use. ConclusionsSoil type best explained landscape-scale variability of SOC and N stocks. Interactions between soil type and land use indicate that the long-term effects of land use on SOC and N were mediated by soil type. Differences in SOC and N stocks across soil types even within the same soil order highlight the importance of identifying pedogenic differences in soil properties, such as texture and mineralogy, which can influence the response of SOC and N to land use. Practice implicationsOur study contributes baseline data on SOC and N for a semi-arid region, which can be used to aid development of landscape-scale models of SOC and N dynamics and inform land management. Our data reveal that assessments of regional land use effects on SOC and N in arid to semi-arid environments should account for landscape to regional variability in soils developing on different geomorphic surfaces and parent materials.