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This paper examines the geomorphological evolution of the Criffel–Dalbeattie granitic pluton (CDGP). Research is based on data from Shuttle Radar Topography Mission, Google Earth, Ordnance Survey maps and field measurements. Granitic emplacement into Southern Uplands terrain along Caledonian structural trends took place during the mid-late Devonian. Faulting and subsidence during the late Palaeozoic and Mesozoic preceded assumed differential uplift of the pluton during the early Palaeocene. This led to the development of bidirectional palaeo-surfaces. Structural rather than lithological controls formed the dominant bases for subsequent weathering during the Palaeogene and Neogene. Shallow surface weathering over the CDGP and absence of saprolite imply that weathering episodes may have been relatively short-lived. However, joint enlargement and in situ eroded corestones indicate that earlier weathered features were substantially modified by glacial agencies. Pleistocene glacial events included ice streaming from the NNW which took place over moulded hills. Thinner late-stage ice scoured irregular hill long profiles while divergent ice contributed to basin erosion. Localised resurgent ice streaming was shortlived. After early uplift and palaeo-surface formation, the CDGP hills evolved through phases of granitic weathering and glacial erosion likely over the past 65 Ma since the early Palaeocene.

The Boteti palaeo-estuary in northern Botswana is located where the endoreic Boteti river, an overflow from the regional Okavango river system, enters the Makgadikgadi pans. The present work considers diagenetic silica and calcium carbonate dominated transformations. The aims are to help identify precursor conditions for the origin of microcrystalline silcrete–calcrete intergrade deposits while developing insight into pene-contemporaneous silica and calcite matrix formation. General precursor conditions require the presence of cyclical endoreic freshwater inflow into a saline pan. The pan should be deep enough to sustain a permanent watertable under climatic conditions sufficient to cause carbonate fractionation within the groundwater. Freshwater inflow into a saline pan drives the geochemistry of the system (from freshwater to saline, from neutral to high pH). The geochemistry is controlled by the periodicity of inflow relative to salinity levels of phreatic groundwater in the receptor saline pan. The source of most silica and localized CaCO3 is derived from the dissolution and precipitation of micro-fossils, while more general CaCO3 enrichment stems from saline pan based carbonate fractionation. Diagenetic change leads to colloidal then more consolidated bSiO2/CaO aggregate formation (amorphous silica) followed by transformations into opaline silica over time. Irregular zones of siliceous sediment forming in otherwise calcareous deposits may relate to the irregular occurrence of biogenic silica in the source sediments, inferring a source for local silica mobilization in intergrade deposits. The distribution of calcareous micro-fossils may have a similar converse effect. Diagenetic evidence from an intergrade deposit with a low SiO2/CaO ratio suggests that transformation occurred more into the pan, while an intergrade deposit with a high SiO2/CaO ratio more likely formed closer to a land margin and was frequently inundated by freshwater. Pene-contemporaneous silcrete–calcrete intergrade formation under the above conditions may take place where dissolved silica crystallizes out in the vicinity of calcite crystals due to local decreases in pH. The continuing consolidation of bSiO2/CaO aggregates may be facilitated by the presence of increasing amounts of calcite. It appears that CaCO3 may act as a catalyst leading to pene-contemporaneous bSiO2/CaO aggregate formation. However the processes involved require further work. Copyright © 2013 John Wiley & Sons, Ltd.

A methodology was devised for comparison of generalised range condition over time, irrespective of the nature of original imagery used. It was applied for range condition change mapping throughout Botswana through 1984–2000. Results showed that range degradation was most widespread during the 1980s drought when 25% of the country was affected, decreased to 6.5% in 1994 and increased to 9.8% in 2000. This suggests that these semi-arid rangelands are fairly resilient and can withstand “normal” droughts even under conditions of heavy grazing pressure. However, degradation that persists during normal or above average rainfall years is related to increasing livestock and other pressures on rangelands and may represent areas with severe range recovery problems. This application meets some requirements of a semi-arid developing country looking to improve range condition monitoring over relatively remote areas.

The Kalahari Transect (KT) is an International Geosphere–Biosphere Programme mega-transect designed to examine hydrological and ecological patterns and processes throughout the savannas of southern Africa. The KT traverses a precipitation gradient ranging from ∼920 mm rain/year in the north to ∼260 mm rain/year in the south. Previous research shows a positive correlation between canopy cover and precipitation suggesting a water limitation on productivity. However, there has been minimal research on other possible sources of limitations, such as soil Nitrogen (N) and/or Phosphorus (P). We used a factorial in-situ experimental design to test for increased aboveground grass production (measured as peak season standing stock) under elevated soil P and P + N levels. Four sites along the KT precipitation gradient were used in this study: Mongu (Zambia), Pandamatenga (Botswana), Ghanzi (Botswana) and Tshane (Botswana). Soils at each site were amended with N and P fertilizers during the dry season. We extracted soil samples during the following growing season to analyze for plant available soil P. Vegetation samples were harvested from which we measured foliar P and aboveground grass biomass production. We saw differences in foliar P at the treatment and site level but not for the interaction between treatment and site. There were individual effects from site on biomass but not for any interactions with nutrient treatments. Despite higher levels of foliar P, we did not detect an increase in aboveground biomass. This may be explained by luxury uptake or allocation to belowground resources.

International audience; In this article, we have applied discriminant diagrams and bivariate plots for tectonic setting to Quaternary sediments from the East African Rift System (EARS). Sediment samples used in this study represent two different phases in early stage intracontinental rift evolution: the alluvial fan of the nascent Okavango system and a lacustrine basin within the relatively more mature Tanganyika system. The diagrams for tectonic setting for major elements place the majority of these EARS sediments within the passive margin (PM) setting. Passive margin sandstones are generally enriched in SiO2 and depleted in Na2O, CaO and TiO2 reflecting their highly recycled nature. Based on major element discriminant diagrams, we propose two new fields for early stage intracontinental rift evolution (alluvial fan and lacustrine basin), within the previously defined passive margin field. The rare earth element (REE) patterns from both Okavango and Tanganyika sediments exhibit patterns similar to PAAS, with ash layers from the Rungwe volcanics in the Tanganyika samples exhibiting an enrichment in REE relative to the bulk sediment.

This work considers the spatial distribution and ages of western MOZ basin siliclastic sediments prior to providing insights into the diagenesis of degraded dune and alluvial fan sands. Previously published and new TL/OSL ages imply that extensive over-washing of dune sands took place at least 100 ka ago while ages on Okavango floodplains imply that the fan was formed ca. 40 ka and has since undergone periods of higher and lower flood regimes. Sediment analyses indicate that both dune and fan sands contain a diagenetic matrix of clay-enhanced amorphous silica (CEAS) which bonds weakly formed aggregates. The time of formation of diagenetic matrix products is inconclusive but may have been accelerated during or shortly after events dated using OSL/TL techniques. Hence earlier dune over-washing may have led to greater porewater of an acidic to near neutral nature which in turn promoted smectite formation and silicic acid precipitation > 100 000 years ago. The relatively abundant CEAS matrix in floodplain sands implies more recent semi-continuous flood events again of an acidic-near neutral nature leading to the formation of smectite. In this case the floodplain sediments are dated as having been deposited around 40 and 11 ka, when porewater content may have accelerated clay formation and silica dissolution. The dual nature of the CEAS in the islands reflects a changing environment from smectite-dominated flooding events to sepiolite-dominated desiccation events. Flooding may also correspond to TL/OSL ages over the past 40 000 years which contributed to accelerated CEAS formation. The sepiolite is associated with a Ca-rich matrix implying desiccation which may relate to drying events over the 40 000 year period or to riparian tree root pumping and selective salt accumulation. This work shows that sedimentation in incipient rifts is complex and rarely explained totally in terms of primary depositional events. The implications of different stages of sand diagenesis may be significant in enhancing palaeo-environmental interpretations in semi-arid fluvial environments.

The Kalahari sand sheet, with a 2.5-million ha area, is probably the largest continuous surface of sand in the world. The Kalahari Transect (KT) is one of a set of IGBP “megatransects” identified for global change studies and provides an ideal setting to investigate changes in ecosystem dynamics, vegetation composition and structure, and carbon or nutrient cycles along a spatial precipitation gradient without confounding soil effects. Soil physical properties remain poorly characterized along the KT. The present work provides a review of previous studies on the Kalahari soils combined with new results from recent analyses of physical (mostly hydraulic) and biogeochemical properties of the soil. In summary, the Kalahari soil is acidic, dominated by sand and nutrient poor. Nutrient contents, soil textures and soil hydraulic properties differ under and between canopies. Roots are concentrated in the top 80 cm of the soil, with grass roots more abundant and dominant close to the surface. Moreover, the distribution of tree roots does not exhibit a clear dominance over grasses at deeper soil layers. This review provides important baseline information for this system, as well as insights as to how biochemical processes vary along a rainfall gradient.

Geo-chemical analyses of duricrusts from the margins of the Moshaweng dry valleys (Kalahari, central Botswana) was undertaken mainly to provide a diagnostic basis for palaeo-environmental conditions and to help stimulate the development of a worldwide duricrusts database. The Moshaweng duricrusts fall into three main petrological groups: calcrete, intergrade cal-silcrete and quartz pebble conglomerate and two distinct geochemical groups for elements involved in non-pedogenic calcrete and cal-silcrete formation, comprising mainly SiO2, CaO, CO2 and Sr. For most other elements, calcretes and silcretes define a single compositional variation trend indicating their genetic link. Results of this work show that the different behaviours of Rb and Ba (no anomaly) and Na2O and CaO (important anomalies) have resulted from in situ chemical weathering likely at the aquifer scale. The source solutions for calcretes and calc-silcrete formation are also derived from the aquifer host clastic sedimentary rocks, namely the Mmamabula Formation (Karoo) and the derived Kalahari Group Sediments. Hence these sediments represent the main source of CaO and SiO2 solutes that formed the Moshaweng duricrusts. Changes in geochemical conditions within the aquifer led to changes in pH such that recharge through infiltration led to Ce oxidation generating Ce-negative anomalies in percolating water implying initially low pH values ( 8.5 during the dry season such that the groundwater was supersaturated in carbonates leading to the precipitation of calcretes. The resulting highly alkaline and saline water may have promoted silica dissolution engendering calc-silcrete formation during the subsequent wet season when a decrease of pH to ∼7–8 was triggered by the inflow of fresh water. On the basis of the hydrochemical constraints discussed in this paper, we show that calcretes precipitated at pH > 8.5 and cal-silcretes at pH

Sediment samples from a continuous 4.6 m profile in the dry bed of Lake Ngami in NW Botswana were analysed for geochemistry and dated using both 14C and TL methods. Certain units in the profile were found to be diatom rich and these, with the geochemical results, were used as indicators of high and low lake levels within the basin. The Lake Ngami sediments contain a high proportion of SiO2 (51–92.5 wt%, avg. 72.4 wt%) and variable levels of Al2O3 (2.04–17.2 wt%, avg. 8.88 wt%). Based on elevated Al2O3 and organic matter (LOIorgC ) results, lacustrine conditions occurred at ca. 42 ka until 40 ka and diatom results suggest that relatively deep but brackish conditions prevailed. At 40 ka, the lacustrine sedimentary record was terminated abruptly, possibly by tectonic activity. At ca. 19 ka, shallow, aerobic, turbulent conditions were prevalent, but lake levels were at this time increasing to deeper water conditions up until ca. 17 ka. This period coincides with the Late Glacial Maximum, a period of increased aridity in the central southern Africa region. Generally, increasing Sr/Ca ratios and decreasing LOIorgC and Al2O3, from ca. 16 to 5 ka, suggest decreasing inflow into the basin and declining lake levels. Based on the enrichment of LREE results, slightly alkaline conditions prevailed at ca. 12 ka. Diatom results also support shallow alkaline conditions around this time. These lake conditions were maintained primarily by local rainfall input as the region experienced a warmer, wetter phase between 16 and 11 ka. Lake levels rose rapidly by 4 ka, probably in response to enhanced rainfall in the Angolan catchment. These results indicate that lake levels in the Lake Ngami basin are responding to rainfall changes in the Angolan catchment area and local rainfall. The results confirm that the present-day anti-phase rainfall relationship between southern Africa and regions of equatorial Africa was extant during the late Quaternary over the Angolan highlands and NW Botswana.

The long morphodynamic history of the linear dune system of northwest Ngamiland comprises both construction and degradation processes. Here we describe features resulting from the latter. Crest lowering during wet periods is associated with lateral transfer of sand into the straats. Weathering and leaching have mobilised iron to the base of the dune profiles and have corroded the quartz grains. Satellite image interpretation indicates that dune sand has been diluted by bioturbation which transferred Damaran saprolite from below the dunes to the surface. Flooding and waterlogging have modified and in places completely destroyed the original crisply linear morphology. Small linear collapse features across the linear dunes are associated with open fractures or faults where water infiltration is facilitated. The implications for luminescence dating of dune sands, to identify periods of aridity, are discussed. The dunes cannot simply be regarded as providing a stacked record of such periods. They are very old and much of the record is missing as a result of crest lowering. The chronostratigraphy includes degradational components which must be distinguished from those of construction. Bioturbation cannot be disregarded as a complication which overprints the luminescence signals.

This work considers new evidence for palaeo-environmental change taking place during the Pleistocene in northern Botswana. Duricrusted strandlines along the northeastern margin of Sua Pan provide palaeo-environmental data pertaining to the Makgadikgadi subbasin (MSB) with inferences regarding the larger Makgadikgadi–Okavango–Zambezi (MOZ) rift depression. Field, XRD and geochemical data show that MSB strandlines comprise calcretes (LU1 type), MgO-rich calcretes with silica (LU2 type), sil-calcrete (LU3 type) and silcrete (LU4 type). Early freshwater episodes appear to have been followed by calcrete-dominated drying phases interspersed with repeated silcretisation. Calcretisation through pan littoral sediments may have been both biogenically and environmentally induced. Calcite precipitation was in part controlled by the Mg/Ca ratio of pore water in the pan littoral zone suggesting closed basin type evaporative conditions, which were followed by a major desiccation interval. Phases of silcrete precipitation appear to be related to periods when the geochemistry of the lake littoral more closely resembled present-day Na–CO 3 –SO 4 –Cl-type brines. Silica saturated acidic, moderately saline groundwater preceded Si precipitation which took place as the pH reduced. Si mobilisation occurred (inter alia) as a result of quartz grain dissolution enhanced by diatoms, bacteria and algal growth in the moist pan littoral. SiO 2 -rich pore waters migrated through cracked and desiccated calcrete into areas of lower salinity and lower pH resulting in preferential calcite removal and silcrete precipitation. Approximate TL dates imply that exposed littoral sand underwent calcretisation during the drying phases of extensive palaeo-lakes which occurred prior to 110 ka, 80–90 ka and 41–43 ka. These wet periods compare fairly well with Vostok core chronologies for southern Africa.

Cyanobacterial soil crusts may be important in arid and semi-arid ecosystems because of their ability to fix atmospheric nitrogen (N2). These crusts are very sensitive to trampling by animals, and their destruction can decrease ecosystem N inputs, affecting the productivity of the region. The objective of this study was to quantify the nitrogen-fixing activity in soil crusts during the wet season in southern African ecosystems using in situ acetylene reduction assays. The average acetylene reduction rates for each site ranged from 88 to 535 nmol m−2 h−1, were highly variable, and were lower than previously reported for other arid areas. All soil samples showed acetylene reduction activity; however, soils with crusts supported higher rates than did “non-crusty” soils under litter, moss, or sand. High values of 15N natural abundance (δ15N) indicated that processes other than N fixation were more important in the crusts than N fixation. For example, coupled nitrification/denitrification and ammonia volatilization or atmospheric deposition of 15N-enriched nitrate or ammonium may have caused shifts in δ15N within the soil crusts. The estimated annual N fixation rates ranged from 8 to 44 g N ha−1 year−1, orders of magnitude lower than values estimated in other studies. The anomalous wet conditions experienced during the year of the study may have increased the temporal availability of soil mineral N and decreased N fixation rates. However, the presence of N fixation activity in all crusts analysed and their ability to survive at high temperature and after long dry periods may provide ecosystem resilience, facilitating ecosystem recovery after severe droughts.

Vegetative response aspects of climate change studies include the determination of vegetation cover changes across climatic gradients. Vegetation characteristics and soil moisture measurements were obtained from four locations with decreasing rainfall along the Botswana Kalahari transect. These are referred to as Pandamatenga, (698 mm year−1), Maun (460 mm year−1), Okwa (407 mm year−1) and Tshane (365 mm year−1). Trends in major vegetative cover and soil components included species types and richness assessments which reflected certain changes southward but also showed interesting degrees of variability. This occurred despite the apparent homogeneity of the Kalahari sands and predominantly semi-arid savanna shrub–woodland vegetation cover. Despite linear decreases, both in rainfall and soil moisture content, results indicated high soil moisture variability at the Okwa location which relates to unique climatic and geological factors. Also many species are unique to specific locations for instance Pandametanga is characterized by Zambesian species while the Maun location is characterized by Colophosphermum mopane. This changes southwards as Acacias become more dominant and significantly co-occur with Grewia flava. While the average total numbers of plants decreased, total numbers of different species varied little from the wetter to the drier end of the moisture gradient. The association between rainfall and woody cover is negative implying that canopy cover extents (in terms of vegetation density) increase along the gradient due to increases in bush encroachment in drier areas. Therefore, while representing a continuum in terms of species numbers, in other respects (e.g. species types and ground cover components) vegetation zones in the Kalahari may be regarded as discontinuous units. Differences between mapped vegetation zones may be accounted for in terms of relatively unique ecosystem factors which function partly in response to geological conditions and partly in response to local (as opposed to regional) climatic factors. This appears to have led to ecosystem adaptive measures (in terms of species responses) rarely mirrored elsewhere along the gradient. Hence adaptability in terms of species migrations in response to relatively rapid climate changes may not readily take place over the Kalahari in Botswana.

Quaternary sedimentation in the Moshaweng dry valley of southeastern Botswana is evaluated on the basis of geomorphological evolution and sedimentological analyses. Stratigraphic evidence reveals an upper surface (1095 m) containing abundant sil-calcrete, an intermediate surface (1085 m) in which sil-calcrete underlies nodular calcrete and lower (1075 m) surface in which sil-calcrete and nodular calcrete are interbedded. This subdivision is reflected in the geochemical composition of the sediments which show an overall trend of decreasing SiO2 content (and increasing CaCO3 content) with depth from the highest to the lowest surface levels. The calcretes and sil-calcretes represent modifications of pre-existing detrital Kalahari Group sand and basal Kalahari pebbles which thinned over a Karoo bedrock high. Modification took place during wet periods when abundant Ca++-rich groundwater flowed along the structurally aligned valley system. With the onset of drier conditions, water table fluctuations led to the precipitation of nodular calcretes in the phreatic layer to a depth of about 20 m. A major geochemical change resulted in the preferential silicification of the nodular calcrete deposits. Conditions for silica mobilization may be related to drying-induced salinity and in situ geochemical differentiation brought about by pebble dissociation towards the top of the sediment pile. As calcretization and valley formation progressed to lower levels, silica release took place on a diminishing scale. Thermoluminescence dating infers a mid-Pleistocene age for sil-calcrete formation suggesting that valley evolution and original calcrete precipitation are much older. Late stage dissolution of CaCO3 from pre-existing surface calcretes or sil-calcretes led to the formation of pedogenic case-hardened deposits during a time of reduced flow through the Moshaweng system possibly during the upper or late Pleistocene. Copyright © 2002 John Wiley & Sons, Ltd.

Quaternary sedimentation in the western Makgadikgadi basin of north central Botswana is evaluated on the basis of new evidence from satellite imagery and sedimentological analyses. Thematic Mapper imagery interpretation, combined with field evidence, has led to the identification of geomorphological features which are mainly composed of light grey calcareous sandstones (formerly calcretes) overlain by dark grey sands. The literature suggests that palaeolake Makgadikgadi I formed and developed intermittently after initial downwarping in the early–mid Pleistocene. The calcareous sandstones were formed when calcium carbonate precipitation took place in pre-existing Kalahari sands along the western shoreline of Makgadikgadi I. Field evidence, supported by X-ray diffraction and SEM analyses, indicates that CaCO 3 precipitated mainly in marshy conditions around plant roots and stems and in association with bacteria in embayments along the lakeshore. The sandstones thickened and became partially indurated as a result of increasing palaeolake levels. Deposition was terminated by renewed tectonism which uplifted the shoreline zone relative to the lake basin, leading to falling palaeolake levels. Post-uplift reworking led to case hardening and pedogenic calcrete formation in the upper sections of the calcareous sandstones. Sedimentary conditions altered during the late Pleistocene. Extensive distributaries from the proto-Okavango system incised the shoreline ridge contributing to the filling of Makgadikgadi II. Satellite data suggest that the proto-Okavango rivers formed a series of fan deltas at this time along the western Makgadikgadi basin. Widespread dispersal of fluvial grey sands took place as a result of basin tilting which led to anastomosing channels flowing southward possibly around 18,000 B.P. These results, although preliminary in nature, augment previous geomorphological analyses by adding some detail in terms of depositional environments and by providing a tentative age and origin for the ubiquitous grey sands.

Determination of trends in soil organic carbon (SOC) and vegetation cover along savanna ecosystem moisture gradients is critical to the understanding of ecosystem functioning and global change. Field results from 57 sites along the Botswana Kalahari Transect (BKT) showed general increases in both SOC and vegetation cover components along the temperature/moisture gradient. However, details in both SOC and woody cover trends revealed an area of relatively declining values in the central Kalahari. Image classification using TM single band data as input values confirmed the existence of an anomalously low woody cover area in the north-central Kalahari, within an area mapped as northern Kalahari tree and shrub savanna. It is postulated that the occurrence of such a zone of low shrubs in a gradient of otherwise increasing tree height and structural complexity may result mainly from edaphic factors, because of the co-incidence of near surface calcrete. However, the effects of fire and heavy grazing also influence the extent of low above-ground biomass, at least locally. Attempts were made to examine the extent to which soil organic carbon and vegetation components can be predicted using Thematic Mapper (TM) imagery, to increase potentially the number of sites in the BKT database. As a result of correlation and regression analyses, it was determined that the imagery-based SOC indexes of the literature were not useful in the Kalahari environment because of the extremely low SOC values encountered. Results of multiple regression analysis confirmed that woody vegetation cover could be predicted mainly through the use of TM3 single band radiance values throughout the BKT even during a non-drought period. Woody vegetation cover could be predicted to a lesser extent by the Transformed Normalised Vegetation Index. As high correlation coefficients were found between woody vegetation cover and SOC, the density of woody cover as derived from TM3 data may be taken as a surrogate for relative SOC abundance. Because this method is indirect, field checking will be required to verify results.

This work describes and provides tentative dates for a previously briefly recorded calcrete suite from semi-arid north-central Australia. The aim is to provide further insight into the nature of carbonate deposition in this area and thereby promote further research. The calcrete deposit occupies 3750 km2and appears to have once served as a conduit for groundwater flow towards the Barkly Tablelands playa system. Two major phases of calcrete precipitation are distinguished tentatively as occurring during the Mid- and Late Pleistocene. Geomorphological and SEM evidence suggest that an earlier phase culminated in the direct calcium carbonate precipitation of travertine mounds. These resulted from effusive groundwater flow, possibly along spring lines. This phase was succeeded by a period of longitudinal dune formation. During a later phase, non-pedogenic calcrete was precipitated between and beyond the mounds, apparently replacing former dunes. The presence of salts within the calcrete infers strong evaporative conditions suggesting that this later precipitation took place in the proximity of a saline lake, possibly palaeo-lake Barkly. Later stage aeolian activity appears to have reworked dune surfaces since the second stage of carbonate deposition.

Long-term rainfall trends have shown that although drought periods have recurred in the west-central Sahel since 1990, the frequency and duration has escalated since the 1960s. Data from vegetation sites along north-south transects indicated that aspects of degradation varied considerably throughout the study region. Visual mapping techniques using Landsat MSS data in conjunction with fieldwork facilitated assessment of degradation feature identification and relative browse thinning throughout the area, with the southernmost populated area being worst affected. Regional differences showed that hydrologically induced erosion features covered less extensive areas and were more prevalent in the east, while active sand movement covered > 10,000 km 2 and was more prevalent in the west. Rate of change in the post-drought period showed areas subject to water erosion increasing (due to increased rainfall) while areas of windblown sand were becoming increasingly stabilized. In combining browse thinning with total degraded area, the western image areas of Ayorou, Gossi and Niafounke appeared to be the worst affected while the eastern areas showed less overall degradation.

[1] Savannas are extensive, seemingly stable mixtures of grasses and trees that are thought to result from a combination of facilitation, competition, and disturbance. Here, we study the spatial distribution in surface soils of soil organic matter and macronutrients at two savanna sites along the Kalahari Transect in southern Africa: a dry site with approximately 350 mm of precipitation annually and a wet site with approximately 950 mm of precipitation annually. The concentrations of total organic carbon, total nitrogen (TN), chloride, sulfate, phosphate, and (nitrate + nitrite) were analyzed in surface soils from these sites using a variety of traditional and geostatistical analyses. Soil nutrient content is generally higher at the wet site (e.g., 0.039% TN versus 0.023% TN, 0.67 μg/g PO4−3 versus 0.30 μg/g PO4−3, and 3.44 μg/g (NO3− + NO2−) versus 1.79 μg/g (NO3− + NO2−)), though there is considerable variation among sample populations from different vegetation covers. Our results indicate that the dry site is also more spatially heterogeneous than the wet site. At the dry site, where the range of spatial autocorrelation for TN, SO4−2, PO4−3, and (NO3− + NO2−) is 8.5 m, 8.5 m, 8.7 m, and 7.3 m, respectively, the spacing of all woody vegetation (both shrubs (woody plants ≤ 2 m) and trees (woody plants > 2 m)) contributes to the patterning of soil resources. At the wet site, where the range of spatial autocorrelation for TN, SO4−2, and PO4−3 is 4.6 m, 6.1 m, and 10.2 m, respectively, only trees contribute to the patterning of soil resources, though (NO3− + NO2−) displays a purely random distribution. We also find weak evidence that nitrogen may not be the, or the only, limiting nutrient in these ecosystems.