Sand Dune Area Research Articles

Effectiveness of ecological restoration projects in Horqin Sandy Land, China based on SPOT-VGT NDVI data

Horqin Sandy Land is a major source of sandstorms in Northern China, especially the Beijing–Tianjin–Tangshan Region. A series of ecological restoration projects including the ‘Grain for Green Project’, the ‘Beijing and Tianjin Sandstorm Source Controlling Project’, and the ‘Three-North Shelterbelt Project’ were implemented in this region. This study assesses the effectiveness of ecological restoration projects within Tongliao City, the main body of Horqin Sandy Land. The different treatment effects of various sand dunes were assessed and compared based on Normalized Difference Vegetation Index (NDVI) from SPOT VEGETATION Ten Daily Synthesis Archive from 1999 to 2007 and the desert distribution map of China in 2000. The results showed that: (1) the fixed and semi-fixed sand dunes were the main sand dune types, which accounted for 70% of the entire sand dune area in 2000; followed by shifting sand dunes and the semi-shifting sand dunes. (2) The ecological restoration projects resulted in improvements of different sand dune types, the improved area covered 76% of the sand dune area, mainly in the southern parts of the study area. The vegetation cover of the sand dunes in Naiman Banner, Hure Banner and the south of Horqin Left Back Banner increased significantly. While mild improvement occurred in the central sand dunes of the study area. (3) The area with degraded vegetation accounted for approximately 10% of sand dune area, mainly located in the southeast of Jarud Banner and the west of Horqin Left Middle Banner. Most of these areas showed mild and insignificant degradation except for a small area of moderate degradation. (4) The types of sand dunes in degraded status were mainly the fixed and semi-fixed sand dunes, followed by the semi-shifting sand dunes and saline-alkali land. The lower the dune fixity (e.g. shifting or semi-shifting versus semi-fixed or fixed) and the more likely to contribute to sand-storms, the greater the effectiveness of restoration projects. Finally, some implications for the sustainable development of the ecological restoration projects are discussed.

Groundwater investigation on sand dunes area in southern part of Vietnam by magnetic resonance sounding

In the last five years, magnetic resonance sounding (MRS), as a non-invasive geophysical method, has emerged as a new technique for ground water investigation in Vietnam. In this paper, we present the general theoretical basis of this method together with acquisition, processing, and interpretation of the MRS data. We show a case study of MRS surveys in sand dunes area in order to characterize aquifers situated in the southern part of Vietnam. From the interpretation of MRS soundings we delimited an aquifer layer in the subsurface with strong lateral variations for which we determined the depth at 44 m and water content between 3% and 9.5%. The longitudinal relaxation constant T*1 is about 250 m s, while the transverse relaxation T*2 is between 150–200 m s. That indicates fine to medium grain size and thus low to medium hydraulic permeability. These results are confirmed by the observations from the well LK1 between 45 to 70 m. The results of other MRS measurements showed the presence of a low water bearing aquifer and were confirmed by the observations in two other wells.

Two centuries of vegetation succession in an inland sand dune area, central Netherlands

Questions: (a) What are the rates and directions of vegetation succession in an inland sand-dune system? (b) What are the differences in successional trajectories in different relief types? and (c) Is it possible to preserve the last areas of still active dunes and under what circumstances? Location: The study sites were located in the northern part of the Veluwe Region, central Netherlands; longitude 5°44′ E, latitude 52°20′ N, altitude 9 to 24 m a.s.l. Methods: Vegetation and relief mapping was conducted in three permanent plots, 200 m × 200 m in size, in 1988 and 2003. Phytosociological releves (2400) were recorded in each 10 m × 10 m subplots. Age of woody species was determined by wood coring. Geographic Information System, ordination analyses, and TWINSPAN were used for data exploration and elaboration. Results: A total of 70 vascular plants and 19 bryophytes were recorded over successional stages spanning approximately190 years. The following dominant species formed the sequence of successional stages, but not all participated in all relief types: Ammophila arenaria, Festuca arenaria, Corynephorus canescens, Festuca ovina and Agrostis capillaris, and pine forest dominated in its herb layer at first by Deschampsia flexuosa and later by either Empetrum nigrum, Vaccinium myrtillus or Vaccinium vitis-idaea. Conclusions: The successional trajectory is basically unidirectional for more than 100 years; no clear multiple successional pathways were observed, as is frequent in coastal dunes. Successional divergence was observed after approximately 130 years in the composition of the herb layer in the closed pine forest. The obvious vegetation heterogeneity in the still active sand-blown area is related to differences in timing of vegetation establishment on particular relief types, thus the succession exhibits a terrain-dependent asynchronous character. We conclude that the last patches of still-active sand dunes can be preserved only by repeated strong artificial disturbances.

Groundwater Responses to Tidal and Meteo-hydrological Forcing in a Coastal Sand-Dune Area

Field observation of the groundwater fluctuation has been conducting with the aim to obtain better understanding of groundwater dynamics in coastal sand-dune environment. Ogata beach in Joetsu coast was selected as field observation location. The Ogata sand dune (20km in length, the maximum of 1km in width, the maximum height of 30m) which is the layered structure of new and old dunes is distributed along the margin of Takada plain. The field observations and analysis of the tide and beach groundwater changes for particular points along beach profile, revealed interesting characteristics, include: strong correlation between tidal and beach groundwater fluctuation and so on. As a results, fresh groundwater supply in terms of steady flow theory is estimated to amount from 13.3 to 79.9m3/day per meter of beach width.

Isotopic and geochemical characteristics of groundwater in the Senegal River delta aquifer: implication of recharge and flow regime

Groundwater and surface water samples were collected to improve understanding of the Senegal River Lower Valley and Delta system, which is prone to salinization. Inorganic ion concentrations and environmental isotopes (18O, 2H and 3H) in groundwater, river, lake and precipitation were investigated to gain insight into the functioning of the system with regard to recharge sources and process, groundwater renewability, hydraulic interconnection and geochemical evolution. The geochemical characteristics of the system display mainly cation (Ca2+ and/or Na+) bicarbonated waters, which evolve to chloride water type; this occurs during groundwater flow in the less mineralized part of the aquifer. In contrast, saline intrusion and secondary brines together with halite dissolution are likely to contaminate the groundwater to Na–Cl type. Halite, gypsum and calcite dissolution determine the major ion (Na+, Cl−, Ca2+, Mg2+, SO42− and HCO3−) chemistry, but other processes such as evaporation, salt deposition, ion exchange and reverse exchange reactions also control the groundwater chemistry. Both surface water and groundwater in the system show an evaporation effect, but high evaporated signatures in the groundwater may be due to direct evaporation from the ground, infiltration of evaporated water or enriched rainwater in this region. The stable isotopes also reveal two types of groundwater in this system, which geomorphologically are distributed in the sand dunes (depleted isotopes) and in the flood plain (enriched isotopes). Consideration of the 3H content reinforces this grouping and suggests two mechanisms of recharge: contribution of enriched surface water in recharging the flood plain groundwater and, in the sand dunes area where water table is at depth between 8 and 13 m, slow recharge process characterized the submodern to mixed water.

Unique arbuscular mycorrhizal fungal communities uncovered in date palm plantations and surrounding desert habitats of Southern Arabia.

The main objective of this study was to shed light on the previously unknown arbuscular mycorrhizal fungal (AMF) communities in Southern Arabia. We explored AMF communities in two date palm (Phoenix dactylifera) plantations and the natural vegetation of their surrounding arid habitats. The plantations were managed traditionally in an oasis and according to conventional guidelines at an experimental station. Based on spore morphotyping, the AMF communities under the date palms appeared to be quite diverse at both plantations and more similar to each other than to the communities under the ruderal plant, Polygala erioptera, growing at the experimental station on the dry strip between the palm trees, and to the communities uncovered under the native vegetation (Zygophyllum hamiense, Salvadora persica, Prosopis cineraria, inter-plant area) of adjacent undisturbed arid habitat. AMF spore abundance and species richness were higher under date palms than under the ruderal and native plants. Sampling in a remote sand dune area under Heliotropium kotschyi yielded only two AMF morphospecies and only after trap culturing. Overall, 25 AMF morphospecies were detected encompassing all study habitats. Eighteen belonged to the genus Glomus including four undescribed species. Glomus sinuosum, a species typically found in undisturbed habitats, was the most frequently occurring morphospecies under the date palms. Using molecular tools, it was also found as a phylogenetic taxon associated with date palm roots. These roots were associated with nine phylogenetic taxa, among them eight from Glomus group A, but the majority could not be assigned to known morphospecies or to environmental sequences in public databases. Some phylogenetic taxa seemed to be site specific. Despite the use of group-specific primers and efficient trapping systems with a bait plant consortium, surprisingly, two of the globally most frequently found species, Glomus intraradices and Glomus mosseae, were not detected neither as phylogenetic taxa in the date palm roots nor as spores under the date palms, the intermediate ruderal plant, or the surrounding natural vegetation. The results highlight the uniqueness of AMF communities inhabiting these diverse habitats exposed to the harsh climatic conditions of Southern Arabia.

Inversion of the asymmetry factor for desert areas of China

Deserts, which have high surface albedo and wide area, are important components of the earth system. It is very important for the research of surface radiation and energy balance to understand the anisotropic scattering of desert areas. The emergence and development of multi-angle remote sensing made possi]e the inversion of the anisotropic scattering of desert areas at the regional or global scale. Firstly, this paper explored the accuracy of the inversion of asymmetry factor using the Hapke model and the simulated single- and multi-phase MISR data. Based on the results, the asymmetry factor of representative surface of desert areas in northwestern China was retrieved. The values of the asymmetry factor retrieved from MISR data were compared with the values retrieved from the laboratory data. The results showed that the single-phase MISR data could be used for the inversion of asymmetry parameter of desert areas. The sign of the asymmetry parameter for the laboratory measurements was positive, which suggests that the surface of laboratory samples is forward scattering. The sign of the asymmetry parameter for MISR data was negative; that is, it is backscattering. The values of the asymmetry parameters retrieved from MISR data were related to the character of the land surface. At Loulan, where the surface was smoother than other sites, retrieved values exhibited the largest negative values of asymmetry factor, suggesting the strongest backscattering. The sand dune area of the Kumtag Desert, which has the greatest roughness, had only slightly negative asymmetry factor values. These findings indicated that at the sensor scale, a rough surface (e.g., dunes) does not necessarily mean more backscattering than a smooth surface. This finding has significant implications for empirical methods (e.g., using the normalized index of backward-scattered radiance minus forward-scattered radiance as an indicator of surface roughness), which should be used carefully for analyzing surface roughness from the remote sensing data.

Climate, landscape and microenvironment interact to determine plant composition in naturally discrete gravel beach communities

Question: What is the relative importance of national-, regional- and within-beach-scale influences on vegetation composition and floristic affinities of New Zealand gravel beaches? Location: Coastal New Zealand. Methods: We sampled vegetation composition at 61 gravel beaches, quantifying site factors and adjacent landscape characteristics. Site, climate and geographic relationships between gravel beaches and related ecosystems were inferred using GIS data layers. To simultaneously investigate influences at different spatial scales, we used ordination and variation partitioning to examine relationships between composition and environment, and hierarchical models to understand floristic affinities with related ecosystems. Results: At a national scale, compositional variation among beaches reflects mean annual temperature and spring vapour pressure deficit; within regions, proximity of native woody vegetation and coastal turfs are important; within-beach variation is related to substrate stability and particle size distribution. The gravel beach flora is 50% exotic, reflecting the highly modified nearby landscapes; 30% of species are characteristic of coastal sands, 20% of braided riverbeds and 8% of coastal turfs. Affinities with coastal sand communities are unrelated to microsite sandiness or area of sand dunes within 50 km. Affinities with braided riverbeds are related to the bed area of those rivers draining within 200 km and proportion of gravel in the substrate. Affinities with coastal turfs are related to proximity to the nearest turf and the proportion of humus in the substrate. Conclusions: Examining multiple scales of influence in a landscape context is essential to understand composition of naturally discrete ecosystems that span wide geographic ranges and to underpin their conservation management.

Irrigation practice and water usage characteristics in sand dune upland fields in the Hokuriku Region, with much rainfall in Japan: case studies on watermelon and Japanese radish

We investigated the use of irrigation water for a successive planting of watermelon followed by Japanese radish in a sand dune area in the Hokuriku Region. The main results were as follows: (1) Upland field tested in the study used a large volume of irrigation water in spite of its location in the Hokuriku Region where rainfall was plentiful. Notwithstanding this, frequent irrigation was considered necessary. (2) Watermelon was cultivated as a Spring–Summer crop with a mean cultivation period of 102 days, during which it was irrigated for 59 days at 1.7-day average intervals with an irrigation volume of 7.1 mm/watering and a total irrigation volume of 428 mm over its entire growing season. The amount of rainfall during the period was 604 mm during 42 days of rainfall. Soil moisture levels in the upland field were kept at relatively high values ranging between pF1.3 and pF1.5 at 15-cm depth with frequent irrigation during no-rainfall period. (3) Japanese radish was cultivated as a Summer–Autumn crop with a mean cultivation period of 71 days during which it was irrigated for 39 days at 1.9-day average intervals with an irrigation volume of 9.4 mm/watering and a total irrigation volume of 358 mm over its entire growing season. The amount of rainfall during the period was 376 mm during 29 days of rainfall. Frequent irrigations were used to maintain the soil moisture levels in the upland field within the range of pF1.4–pF1.6 at 15 cm depth. (4) During the irrigation period, the amount of water used for irrigation was 5.9 mm/day in watermelon and 6.1 mm/day in Japanese radish which are greater than evapotranspiration (ET). In addition, during pre-irrigation, the preparation of the seeding bed can be carried out at the right time which contributes to producing high-quality Japanese radish in adequate quantity. In addition, pre-irrigation for preparation of bed for watermelon transplanting is very important for better time management and high-quality production. For this purpose, the irrigation facilities need to be functioning very well.

The influence of dunes on mixing in a migrating salt‐wedge: Fraser River estuary, Canada

AbstractDune bedforms and salt‐wedge intrusions are common features in many estuaries with sand beds, and yet little is known about the interactions between the two. Flow visualization with an echosounder and velocity measurements with an acoustic Doppler current profiler over areas of flat‐bed and sand dunes in the highly‐stratified Fraser River estuary, Canada, were used to examine the effect of dunes on interfacial mixing. As the salt‐wedge migrates upstream over the flat‐bed, mixing is restricted to the lower portion of the water column. However, as the salt‐wedge migrates into the dune field from the flat bed, there is a dramatic change in the flow, and large internal in‐phase waves develop over each of the larger dunes, with water from the salt‐wedge reaching the surface of the estuary. The friction Richardson number shows that bed friction is more important in interfacial mixing over the dunes than over the flat‐bed, and a plot of internal Froude Number versus obstacle (dune) height shows that the salt‐wedge flow over the dunes is mainly supercritical. Such bedforms can be expected to cause similar effects in interfacial mixing in other estuaries and sediment‐laden density currents, and may thus be influential in fluid mixing and sediment transport. Copyright © 2010 John Wiley & Sons, Ltd.

ベトナム中部タムジャン・ラグーンにおけるエビ養殖の拡大と環境問題―高解像度衛星画像を用いた湖沼環境評価―

Tam Giang Lagoon, lying along the coast of Hue Province in Central Viet Nam, has undergone a rapid expansion of shrimp aquaculture over the last dozen years. Intensive shrimp farming has expanded not only in and along the littoral zone of the lagoon, but also over lowland paddy fields and on coastal sand dunes. In this research, the authors studied three areas that include the coastal sand dune area southeast of Tam Giang Lagoon, classifying shrimp farming into six types in terms of aquacultural facility and operational management, while identifying their geographical distributions and processes of development during the period 1999-2009 through on-site survey and interpretation of multi-temporal high-resolution satellite images of Landsat7-ETM, QuickBird and ALOS-AVNIR-2. Some environmental issues accompanying the development of the respective types of shrimp farming are schematized to make an assessment of lagoon environments from the perspective of sustainable resource management in this area. In the results, the following three conclusions are presented. (1) Overcrowded installation of aquacultural facilities in and along the littoral zone has deteriorated water quality in the lagoons, and such facilities may have increased recent flood levels during times of flooding. (2) Intensive aquaculture spreading over the lacustrine lowlands has caused further water pollution in the lagoons and outbreaks of shrimp diseases, and this type of aquaculture may lead to saltwater intruding into the groundwater under adjacent paddy fields. (3) Recent development of large-scale intensive shrimp farming on coastal sand dunes may cause a shrinkage of the freshwater lens existing under the sand dunes, as well as leakage of saltwater from shrimp ponds into the freshwater lens.

Distribution of halophytes in coastal salt marsh and on sand dunes in Korea

To elucidate the distribution of halophytes in Korea, we surveyed 95 coastal salt marsh and sand dune areas. As a result, 62 halophytes of 57 species, 4 varieties and 1 form belonging to 44 genera and 21 families were recorded from coastal regions and islands of South Korea. Of these, 33 taxa were plants growing on sand dunes and the other 29 in salt marsh. Fifty eight taxa were found on the west coast, which was surveyed at 61 areas. The most common species among them were Suaeda glauca (Bunge) Bunge, Suaeda japonica Makino, Phragmites communis Trin., Zoysia sinica Hance, Carex scabrifolia Steud. in salt marsh, and Salsola komarrovii Iljin, Lathyrus japonicus Willd., Limonium tetragonum (Thunb.) A.A. Bulloc, Calystegia soldanella Roem. & Schult. on sand dunes. On the other hand, only 45 taxa were found on the southern coast, surveyed at 15 areas. On the east coast, surveyed at 13 areas, 44 taxa were found. The most common species were Salsola komarrovii Iljin, Lathyrus japonicus Willd., Calystegia soldanella Roem. & Schult., on sand dunes and Linaria japonica Miq., which on the Korean peninsula is found only on the east coast. On Jeju Island, surveyed at 6 areas, 30 taxa of halophytes were found. Canavalia lineata (Thunb.) DC. is found in Korea only on Jeju Island. About half of the Korean halophytes were members of three families (Chenopodiaceae: 12 species, Poaceae: 12 species and Asteraceae: 7 species).

Flight of mayflies towards horizontally polarised and unpolarised light

Light in the optical environment is not just coloured, but it is polarised. The visual system of many insect species is polarisation sensitive which allows them to use the polarisation pattern of skylight for navigation purposes. There is also increasing evidence that mayflies and other aquatic and semiaquatic insects are able to detect water bodies on the base of the water-reflected horizontally polarised light using it as an environmental cue to detect suitable habitats. In a pilot experiment we constructed and tested light trap pairs emitting unpolarised and horizontally linearly polarised light with the same intensity and spectrum to record potential polarisation-sensitive species from various insect orders. Aquatic insects are assumed to use horizontally polarised light for habitat detection. Thus, we expected that these species will be captured in significantly greater numbers by the trap emitting horizontally polarised light than by the trap emitting unpolarised light. Trappings were carried out at each night from April to October during 2001 and 2002 at two sites in Hungary. One of the trapping sites was at the edge of the flood basin of a river with some smaller ponds. The other trapping place situated in a protected sand dune area scattered with ephemeral alkali lakes. The same mayfly species were collected by the traps emitting polarised and unpolarised light. From the recorded five species four species were caught in greater numbers and more frequently by the trap emitting horizontally polarised light. Caenis horaria and Cloeon dipterum mayflies were attracted significantly stronger to the polarised trap, thus they are likely to use positive polarotaxis in habitat detection. Ephoron virgo and Caenis macrura also showed a tendency for polarotaxis, but they were represented with too low numbers of individuals in the samples to produce significant differences.

Grass Rhizosheaths: Associated Bacterial Communities and Potential for Nitrogen Fixation

Rhizosheaths are structures composed of mucilage secreted from plants and adherent soil particles that form a cylinder around the root. Using scanning electron microscopy (SEM), we observed bacteria associated with rhizosheaths of the grasses Achnatherum hymenoides, Calamovilfa longifolia, Hesperostipa comata, and Pascopyrum smithii from a sand dune area in Harding County in northwestern South Dakota. The greatest numbers of bacteria, observed with SEM (529 mm-2), and the greatest number of culturable bacteria (9.9 × 107 CFU · g-1 or 5178 CFU · mm-2) were on rhizosheaths of C. longifolia. Rhizosheaths of all the grasses examined contained a higher density of bacteria than the surrounding soil. Nitrogen fixation, as assayed by reduction of acetylene to ethylene, was present in some rhizosheaths. Bacterial nifH gene sequences amplified from bacteria associated with rhizosheaths were most similar to those from Alcaligenes latus and Mesorhizobium loti.

Abstracts of Nippon Dojo-Hiryogaku Zasshi

Abstracts of Nippon Dojo-Hiryogaku Zasshi

A new species ofAeschynomeneL. (Leguminosae, Papilionoideae) from a continental sand dune area in north-eastern Brazil

Aeschynomene sabulicola L.P. Queiroz & D. Cardoso is proposed as a new species of the section Ochopodium. This new species seems to be related to the series Viscidulae, as it presents herbaceous, slender branches, densely covered by viscid glandular hairs. However, it possesses fruits much larger than expected for this series. Aeschynomene sabulicola can be diagnosed by the erect habit, reaching c. 3.5 m high, inflorescences divaricate and horizontal with remote flowers, and fruits with only one subreniform article, this measuring 13–14 × 7–8 mm. The species occurs only in a continental sand dune area along the middle Sao Francisco River basin in the State of Bahia, north-eastern Brazil. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157, 749–753.

Effects of rainfall characteristics on infiltration and redistribution patterns in revegetation-stabilized desert ecosystems

Summary Rainfall, the dominant source of water replenishment in the semi-arid sand dune area of north-western China, plays an important role in sustaining the desert ecosystem. An experiment to measure water balance associated with infiltration events was conducted on the re-vegetated sand dunes in the Tengger Desert, north-western China. The redistribution of infiltrated moisture in the course of percolation, root extraction, and evapotranspiration pathways was investigated for a period of 45 days during the growing season. Time domain reflectometry probes were inserted horizontally at 12 different depths below the ground surface in the Caragana korshinskii dwarf-shrub community to record volumetric soil moisture at hourly intervals. Rainfall events were sporadic with widely different intensities during the period of the experiment. The presence of vegetation markedly influenced the infiltration and redistribution patterns on the stabilized sand dunes. Infiltration rates varied greatly with individual rainfall quantity and antecedent soil moisture, with drier soil profile facilitating infiltration. The relationship between infiltration rate and rainfall intensity was linear, with infiltration rate at 80% the magnitude of rainfall intensity. Contrasts between the infiltration rate and cumulative infiltration varied with the feature of rainfall events of the vegetation-stabilized desert soil and the un-vegetated bare desert soil indicate that the measured precipitation alone is insufficient to explain the effective rainfall of the studied regions. At rainfall amount

Introduction to special section on Aeolian Processes: Field Observations and Modeling

[1] Aeolian processes, involving erosion, transportation, and deposition of sediment by the wind, occur in a variety of environments including coastal areas, semiarid, and arid regions (e.g., cold and hot deserts), agricultural fields, and some planetary bodies, notably Mars and possibly Venus and Titan. Aeolian processes are responsible for the emission, transport, and deposition of dust and formation of areas of sand dunes. [2] This special section contains 14 papers that recognize the distinguished career of Dr. Dale Gillette. The papers are based upon oral and poster presentations given at the Sixth International Conference on Aeolian Research (ICAR VI), which was held at the University of Guelph, Ontario, Canada, 23–28 July 2006 (for a summary of the conference see Lancaster et al. [2006]). A special aspect of ICAR VI was the recognition of the long, multifaceted, and distinguished career of Dale Gillette, known to many for his seminal work on mineral aerosols and wind erosion processes. ICAR VI was the latest in a series of conferences on aeolian processes, sediments, and landforms that started in 1986 in Aarhus, Denmark, followed by conferences in Sandberg, Denmark (1990); Zzyzx, California (1994); Oxford, UK (1998); and Lubbock, Texas (2002). The next ICAR will be held in Argentina in 2010. [3] The papers in this volume were chosen for their close relationships to aspects of Dale Gillette's career and his major scientific contributions, as well as being a reflection of some of the most innovative contemporary approaches to studies of aeolian processes, sediments, and landforms. Many of the papers cite Dale's work and are clearly inspired by the fundamental concepts and approaches that he articulated. Thus, there are papers on dust emissions from disturbed and undisturbed surfaces [e.g., Macpherson et al., 2008] that build on the work of Gillette et al. [1980] as well as field studies of dust events and processes [McGowan and Clark, 2008] that continue and build upon the methodology developed during collaborative work at Owens Lake, California, the major source of mineral dust in the western United States prior to mitigation measures designed to reduce dust emissions [Cahill et al., 1996; Gillette et al., 1997a, 1997b, 1997c]. Further papers document experiments on dust deposition processes [Goossens, 2008] and field studies of dust deposition to soils and ecosystems [Bowker et al., 2008; Goldstein et al., 2008]. [4] Dale Gillette was a pioneer in conceptualizing and quantifying the effects of roughness elements (rocks, vegetation) on wind erosion and sediment transport processes [Gillette and Stockton, 1989; Musick and Gillette, 1990; Raupach et al., 1993; Stockton and Gillette, 1990], and this volume contains a number of papers [e.g., Brown et al., 2008; King et al., 2008; Sutton and McKenna Neuman, 2008; Okin, 2008; Shao and Yang, 2008] that build on the fundamental concepts that Gillette and his colleagues developed. Dale Gillette also maintained a long-term interest in the fundamentals of sediment mobilization and transport by wind [e.g., Gillette and Stockton, 1986; Gillette et al., 1996]; papers in this special section by Rasmussen and Sorensen [Rasmussen and Sorensen, 2008] as well as McKenna Neuman and Sanderson [McKenna Neuman and Sanderson, 2008] provide further understanding of the controls of sediment transport and creative ways in which to model these complex nonlinear processes. Throughout his career, Dale Gillette maintained a strong interest in modeling of aeolian processes. Many of the papers in this volume develop models that can be used to assess aeolian processes and their effects on the environment as well as to understand fundamental controls of the processes [e.g., Okin, 2008]. Although Dale never worked on dunes, the approach of the paper on barchan dune corridors [Elbelrhiti et al., 2008] adopts the approach to modeling advocated by him, being firmly based upon fundamental physical principles. [5] The papers in this volume clearly indicate the diversity and healthy state of aeolian research today. Challenges for the immediate future include the issue of scaling of detailed process studies, such as those reported here, on small spatial and temporal scales to regional and global issues such as the global dynamics of aeolian systems, including for example the contribution of dust deposition to soil development, and the human dimensions of change in aeolian systems. Despite considerable progress in recent years, there still remains a significant gulf between the modeling community and those engaged in field and experimental studies. Dale Gillette provides a stellar example of a person who has been able to bridge this gap and thereby contribute in a unique way to scientific understanding of aeolian processes as well as its application to real-world problems of wind erosion and air quality.

Effects of Land-Cover Transformation and Climate Change on the Distribution of Two Microendemic Lizards, Genus Uma, of Northern Mexico

Two species of the Fringe-Toed Lizard, Uma exsul and Uma paraphygas, are restricted to small areas of sand dunes in the Chihuahuan Desert, where land cover transformation has increased dramatically in recent years and future climatic changes are expected to be severe. The current geographic distribution of each species was estimated by ecological niche modeling using the Genetic Algorithm for Rule-set Prediction (GARP). A recent land-use map was used to determine areas where habitat has been transformed by human activities, and niche models were projected under two simulated climatic scenarios and for two periods of time (2020 and 2050) to estimate their future potential distributions. Results indicate a high degree of anthropogenic habitat transformation within the distribution of U. exsul, and an important reduction of its distribution by 2050. For U. paraphygas land cover transformation is less severe, but a complete collapse of its current distributions is expected in the future because of climate change. Despite the uncertainty involved, the general trends seem highly feasible and immediate conservation actions are recommended.

Long‐term effects of restoration on soil hydraulic properties in revegetation‐stabilized desert ecosystems

Improving structure of soils found at 0–5 cm depth, and increasing the thickness of biological soil crusts are both associated with sand dune revegetation‐stabilization in arid northwestern China. Since 1956, research on sand dune stabilization has included the use of straw chequer‐boards to facilitate development of soil structure. One method to gauge the degree of stabilization is to compare undisturbed soil hydraulic properties, including water retention [h(θ)] and hydraulic conductivity [K(h)] functions, with properties from stabilized sites of different ages. This study examined properties at five experimental sites of different ages since revegetation (51, 42, 34, 20 and 0 years). Saturated hydraulic conductivity (Ks) was determined in‐situ from all five sites, and the h(θ) curve was determined from samples collected from three sites. A significant negative correlation existed between Ks and the clay, silt and organic matter contents. Differences in most van Genuchten parameters for h(θ) were observed between the revegetated plots and the migrating sand dune area. Results of this long‐term study show that changes in soil hydraulic properties and improvement in soil structure were associated with migrating dune stabilization.