An evolutionary model for sabkha development on the north coast of the UAE

The north coast of the United Arab Emirates (UAE) provides a typical example of coastal sabkha (supratidal flat) formation. Various stages of sabkha development can be recognized along this coast. This paper combines previous studies of sabkha environment with the results of field investigation of sabkha geomorphology, sedimentology, and stratigraphy on the north coast of UAE, to formulate a model of sabkha evolution.The model has six stages in the evolution of coastal sabkhas following the early Holocene sea-level rise. These are: Stage 1: sea-level rise results in the formation of an embayment. Stage 2: involves subsequent spit development and progradation across the bay as a result of sediment availability. Stage 3: coincident with spit evolution is the development of a khor (tidal inlet) with or without mangrove. Channel depth of Khors varies from 4 to 6 m. Stage 4: sediment accumulates in the khor reducing the khor depth, turning it into a lagoon. There are three sub-stages of the lagoon stage. (a) With lagoon depths of 1–2 m, (b) with lagoon depths 0.5 m or less, (c) when the lagoon floor is exposed at low tide. Stage 5: is sabkha formation; development occurs in two sub-stages. In the first the sabkha is immature and flooded during rain storms and spring tides (0.1 m above present sea-level). Later the sabkha is only flooded after rainstorms, when it reaches an elevation of about 1 m or more above present sea-level. Stage 6: in sabkha development is the coastal plain, which results when large sabkhas are linked together.     

Nipa (Distichlis palmeri): A perennial grain crop for saltwater irrigation

The perennial saltgrass nipa (Distichlis palmeri, Poaceae) is endemic to northern Gulf of California tidal marshes flooded with hypersaline (38–42 g L⁻¹) seawater. Nipa was a wild harvest staple of the Cocopah people of the Río Colorado delta. We investigated the physiology, anatomy, chromosome number, and agronomic potential of nipa as a global food crop. Nipa seeds had 60–93% germination on salinities ranging from 0 to 30 g L⁻¹. Relative Growth Rates (RGR) on both flooded and aerobic conditions remained above 4% d⁻¹ up to 30 g L⁻¹, about half the RGR on freshwater. Nipa grain (caryopses) had 7–8% protein, 8% sugar and 79% total digestible carbohydrates (mostly starch) and only 2% ash and 8% fiber, equal to conventional grains in apparent nutritional value. Shoots were low in ash and sodium, and compared favorably to alfalfa forage in protein, digestible carbohydrates and energy contents. Mature female stands in the Colorado River delta produced an estimated 1.25 t ha⁻¹ of grain, but over two years in the greenhouse only partial flowering was observed. Nevertheless, D. palmeri appears to be worth developing as a perennial grain and forage crop, especially for salinized, flooded soils.     

Environmental changes,remote sensing,and infrastructure development: The case of Egypt's East Port Said harbour

Using Landsat TM data, this article examines the environmental impact of the East Port Said harbour project on the surrounding landscape. The optimum three-band combination and the most appropriate multispectral bands were selected to enhance the images and monitor land cover changes for the periods of 1984–1991 and 1991–2003. The results indicate that wetland areas declined from 103 km² in 1984 to 30 km² in 2003. In addition, the surface area of El-Malha Lake has shrunk from 27 km² to 18 km² over the same period. In contrast, the area covered by salt crust has increased from 11 km² in 1984 to 19 km² in 2003. Urban land use and designed cultivated lands were also significant in 2003, covering 49 km² and 71 km², respectively. The rate of shoreline change between 1984 and 2003, the period when the East Port Said harbour was constructed, was calculated. Vector data indicate that the rate of shoreline loss was ?13 m/year from 1984 to 1991 and ?15 m/year from 1991 to 2003. Despite the fact that construction of the East Port Said harbour caused significant changes in the study area, there are several factors controlling coastline and land cover changes including industrial development and fish cultivation farms.     

Seasonal changes in nauplii and adults of Calanus hyperboreus (Copepoda) captured in sediment traps,Amundsen Gulf,Canadian Arctic

Arctic copepods were collected using time-series sediment traps in the Amundsen Gulf, Canadian Arctic, as part of the CASES (Canadian Arctic Shelf Exchange Study) program. Four sediment traps were deployed at three stations (200 m depth for CA15, 200 and 400 m depths for CA18, and 200 m depth for CA20) from October 2003 to July 2004. We collected many copepod nauplii ranging in body length from 155 to 811 μm, among which nauplii (mostly N1–2) of Calanus with a size of ∼190 μm apparently increased in abundance from February to mid-March. Mature-stage adult females (AF) of Calanus hyperboreus were collected in the traps from February to March, and adult males of C. hyperboreus appeared from November to December at all stations. The likely spawning period of these AF coincided with the occurrence period of ∼190 μm-sized nauplii. This finding suggests that these nauplii were derived from C. hyperboreus and that their breeding began at the beginning of November or December at the latest, continuing through April in the Amundsen Gulf.     

Characteristics of the Gobi desert and their significance for dust emissions in the Ala Shan Plateau (Central Asia): An experimental study

Using intact samples of Gobi surfaces, we conducted wind tunnel experiments and related analyses to describe the surface characteristics of Gobi deserts and their significance for dust emissions in the Ala Shan Plateau, an area of Central Asia with high dust emissions. Under relatively high wind velocities (22 m s⁻¹), the total sediment transport approached 700 g m⁻², with the fine fractions (<50 μm in diameter) accounting for up to 26 g m⁻². In consecutive experiments, the emission rates decreased greatly due to depletion of erodible particles. In the Ala Shan Plateau, coverage by gravels varied, and aeolian sediment transport increased with increasing gravel cover (to about 30%); above that level, transport decreased. Because gravel cover was less than 30% in most areas, the gravel may not play important role in dust emissions in this region. Although the Gobi surfaces are covered by gravel, high clay contents that may restrain sediment transport. In the Ala Shan Plateau, dust emissions therefore appear to be controlled mainly by the availability of fine particles, which is in turn controlled by their deposition by ephemeral streams, by their creation via physical, salt, and chemical weathering, and by other processes such as aeolian abrasion.     

Groundwater fluctuations induced by ecological water conveyance in the lower Tarim River,Xinjiang, China

Data from 40 monitoring wells across 9 sections of the lower Tarim River from 2000 to 2006 were analyzed to investigate the relationship between the transmission loss per unit river length and the change in groundwater depth. The relationship between the rise of the groundwater table (y) and the distance from the main river reach (x) was then assessed through regression analysis. We concluded that the maximum affected area was 1933 m away from the main river reach in the Alagan section, and the minimum affected area was 576 m away in the Kaogan section. In addition, after 8 water deliveries, the volume for recharging the groundwater was 78 248.7 × 10⁴ m³. Using the Yingsu section as an example, we found that the volume for recharging the groundwater decreased with additional periods of delivery except after the second and sixth water delivery The results revealed that the beneficial effect of an ecological water conveyance project on the ecosystem in the lower Tarim River is a long-term process. These findings may be useful for guiding studies on instream flow requirements and provide a scientific basis for implementing similar ecological projects in other areas.     

Considerations on the chronological and causal relationships between talus flatirons and palaeoclimatic changes in central and northeastern Spain

Talus flatirons are relatively common landforms in arid and semiarid areas. They are frequent in the Duero, Tajo and Ebro Tertiary Basins in Spain. The generation of a flatiron requires the alternation of periods with a prevalence of accumulation processes followed by periods with a preponderance of erosion processes. In the three Tertiary basins considered here talus flatirons have been found in numerous places and up to five stages of slope evolution have been recognised in some locations. The second youngest stage (S₂) has been dated in several places in the Ebro and Duero Basins through ¹⁴C. The age of this stage ranges from 2529 ± 52 to 3590 ± 40 ¹⁴C yBP. The third youngest stage (S₃) has yielded dates of 27,862 ± 444 radiocarbon years BP in the Ebro Basin, and 28,550 ± 130 ¹⁴C yBP in the Duero Basin. S₄ has been dated in the Ebro Basin to 35,570 ± 490 ¹⁴C yBP. The S₂ slope facets correspond to the Iron and Bronze Age Cold Stages. The S₃ and S₄ flatirons may be correlated with the Heinrich events H₃ and H₄. These dates may indicate that the accumulation periods on the slopes correspond to cold global events. The dates obtained for the stages S₃ and S₄ in the central and northeastern sectors of Spain and their good correlation with Heinrich events suggest that flatirons could be related to climatic sequences in the Upper Pleistocene and Holocene.     

Allometric relationships and peak-season community biomass stocks of native shrubs in Senegal's Peanut Basin

Allometric equations and community biomass stocks are presented for Guiera senegalensis J.F. Gmel (Gs) and Piliostigma reticulatum (DC.) Hochst (Pr) – two native shrub species in the Sahel. These shrubs are of interest because they dominate semi-arid sub-Sahalien Africa but have been largely overlooked as a key biomass component and regulator of ecosystem composition and function in this landscape. In Year 1, best predictors of aboveground biomass were height and number of stems (Gs) and crown diameter (Pr); and for belowground biomass were height and basal diameter (Gs) and basal diameter (Pr). In Year 2, height and crown diameter were the best predictors of aboveground biomass (R² = 0.90 for Gs and 0.87 for Pr), whereas basal diameter and number of stems (Gs) and basal diameter (Pr) were best predictors of belowground biomass. Peak-season biomass estimates ranged from 0.44 to 4.58 ton ha^?1 (mean = 2.38 ton ha^?1) in the Gs sites and from 0.33 to 7.38 ton ha^?1 (mean = 3.71 ton ha^?1) in the Pr communities. Both species exhibited unusually large root:shoot ratios (4.5:1 for Gs and 10.2:1 for Pr). Although models differ between years, allometric relationships provide reasonable biomass estimates for Gs and Pr.     

Highways as flyways: Time and energy optimization in migratory Levant Sparrowhawk

A successful migratory strategy is the result of optimizing three important factors – time, energy and safety. Raptors mainly use soaring-and-gliding flight that results in time and energy minimization. I observed migratory flocks of Levant Sparrowhawk as they took off from nocturnal roost, to understand the environmental and anthropogenic factors affecting their early-morning flight behavior. The earliest flocks converged in a straight line from the roosts to the highway and flew above it for 40–70 min after sunrise. The flocks stayed ca. 40–100 m in above the highway which suggested that the Levant Sparrowhawk utilized the heat released by the highway surface to improve flight conditions. Twenty-five Levant Sparrowhawk that took off from the roost and headed across open areas had to flap an average of 16.8 ± 1.9 wing beats per minute, which was significantly greater (paired t = ?16.8, P = 0.0001) than the 8.8 ± 1.8 wing beats per minute for the same individuals when flying over the highway. The data indicate that Levant Sparrowhawk, that have behaviorally modified and adapted to flying along highways, are able to migrate an hour earlier in the day and to conserve almost 50% of the energy they would otherwise have had to invest in covering the same distance in flapping flight. The result of this strategy maximizes timing of migration while minimizing energy expenditure.     

Comparative study of nitrogenase activity in different types of biological soil crusts in the Gurbantunggut Desert,Northwestern China

Biological soil crusts cover large areas of the Gurbantunggut Desert in northwestern China where they make a significant contribution to soil stability and fertility. The aim of this study was to quantify the potential nitrogen-fixing activity (NA) of different types of biological soil crusts in the Gurbantunggut Desert. The results suggest that NA (nmol C₂H₄ m^?2 h^?1) for each type of crusts was highly variable. Seasonal variation was also important, with all three types of crusts responding in a similar way to changes in environmental conditions. From March to May, NA was relatively low for all crust types. During this season, NA was 2.26 × 10³ for cyanobacterial crust followed by lichen crust (6.54 × 10²) and moss crust (6.38 × 10²). From June to October, all crust types reached their highest level of NA, especially lichen crust and moss crust (p < 0.01). The NA of cyanobacterial crust (9.81 × 10³) was higher than that of lichen crust (9.06 × 10³) and moss crust (2.03 × 10³). From November to February, when temperatures were consistently low (<0 °C), NA was at its lowest level, especially in cyanobacterial crust (4.18 × 10²) and moss crust (5.43 × 10²) (p < 0.01). Our results indicate that species composition is critical when estimating N inputs in desert ecosystems. In addition, all three types of crusts generally responded in a similar way to environmental conditions. The presence of N fixation activity in all crusts may contribute to the maintenance of fertility in sparsely vegetated areas and provide surrounding vascular plant with fixed nitrogen.     

Synergic effect of salinity and light-chilling on photosystem II photochemistry of the halophyte,Sarcocornia fruticosa

Laboratory experiments were conduced to assess the synergic effect of chilling and light on photosystem II photochemistry of the halophyte, Sarcocornia fruticosa, grown at different salinity concentrations (0, 170, 340, 510 and 1030 mM). Chlorophyll fluorescence was measured after chilling (at 5 °C in darkness) and light-chilling (at 5 °C and 700 μmol m^?2 s^?1) treatments, and after 24 h of recovery (at 20 °C and 75 μmol m^?2 s^?1). At 5 °C and 700 μmol m^?2 s^?1, plants grown with 0 and 170 mM NaCl showed the lowest F_v/F_m values, whereas quantum efficiency of PSII (Φ_PSII) was higher for plants grown at 170 and 340 mM NaCl, these results being consistent after two exposures to chilling treatments. Susceptibility to photoinhibition decreases when low temperature and high light are combined with high salinity. Therefore, populations of S. fruticosa that occur in arid environments with salinities c. 340 mM could show a higher tolerance to light-chilling.     

Tsunami exposure estimation with land-cover data: Oregon and the Cascadia subduction zone

A Cascadia subduction-zone earthquake has the potential to generate tsunami waves which would impact more than 1000 km of coastline on the west coast of the United States and Canada. Although the predictable extent of tsunami inundation is similar for low-lying land throughout the region, human use of tsunami-prone land varies, creating variations in community exposure and potential impacts. To better understand such variations, land-cover information derived from midresolution remotely-sensed imagery (e.g., 30-m-resolution Landsat Thematic Mapper imagery) was coupled with tsunami-hazard information to describe tsunami-prone land along the Oregon coast. Land-cover data suggest that 95% of the tsunami-prone land in Oregon is undeveloped and is primarily wetlands and unconsolidated shores. Based on Spearman rank correlation coefficients (r_s), correlative relationships are strong and statistically significant (p < 0.05) between city-level estimates of the amount of land-cover pixels classified as developed (impervious cover greater than 20%) and the amount of various societal assets, including residential and employee populations, homes, businesses, and tax-parcel values. Community exposure to tsunami hazards, described here by the amount and relative percentage of developed land in tsunami-prone areas, varies considerably among the 26 communities of the study area, and these variations relate to city size. Correlative relationships are strong and significant (p < 0.05) for community exposure rankings based on land-cover data and those based on aggregated socioeconomic data. In the absence of socioeconomic data or community-based knowledge, the integration of hazards information and land-cover information derived from midresolution remotely-sensed imagery to estimate community exposure may be a useful first step in understanding variations in community vulnerability to regional hazards.     

Titanium behavior in quartz during retrograde hydration: Occurrence of rutile exsolution and implications for metamorphic processes in the Sør Rondane Mountains,East Antarctica

In the central Sør Rondane Mountains, East Antarctica, orthopyroxene felsic gneiss (OPG) was converted to hornblende-biotite felsic gneiss (HBG) by hydration that accompanied the intrusion of pegmatite. The retrograde HBG contains exsolved rutile in quartz. The composition of orthopyroxene and clinopyroxene in OPG suggests a temperature of 840 °C (interpreted as the near-peak temperature), and the composition of hornblende and plagioclase in HBG suggests a temperature of 670–700 °C (interpreted as the temperature during hydration). Ti concentrations in quartz were measured using an electron probe micro-analyzer, and Ti-in-quartz thermometers were applied. Measured Ti concentrations were 110 ppm (equivalent to 760–820 °C) for homogeneous quartz from OPG and 35 ppm (650–700 °C) for an exsolution-free area of a quartz grain from HBG. The pre-exsolution Ti concentration in quartz from HBG was reconstructed with 100 μm beam diameter and 25 kV of accelerating voltage, giving 103 ppm, similar to the value obtained for homogeneous quartz in OPG. The temperatures obtained using a Ti-in-quartz thermometer are consistent with those estimated using other thermometers. Although analysis of the main constitute minerals in HBG yields the conditions of hydration, the reconstructed pre-exsolution Ti content in quartz within HBG yields the pre-hydration conditions. Thus, the Ti-in-quartz thermometer is a potentially powerful tool with which to identify the peak or near-peak temperature conditions, even for retrogressed metamorphic rocks.     

Physical impact of grazing by sheep on soil parameters in the Nama Karoo subshrub/grass rangeland of South Africa

The direct short-term impact of three rates of stocking (4, 8 and 16 small-stock units [SSU] ha^?1) was quantified in terms of soil characteristics of arid Nama Karoo vegetation (subshrub/grass). Mature Merino wethers grazed in the experimental plots throughout May in 1995 and 1996 (the plots were not subjected to grazing at any other time). Stocking rate proved inversely related to initial infiltration rate. Light trampling (4 SSU ha^?1) loosened the topsoil sufficiently to increase the initial infiltration rate: infiltration capacity of soil in fields stocked at 4 SSU ha^?1 and 16 SSU ha^?1 was 17% higher and 14% lower respectively than that of soil of ungrazed rangeland over the two grazing periods. Increased soil compaction and greater bulk density due to higher stocking rates significant decreased the infiltration rate. Compared to ungrazed rangeland stocking rates of 4, 8 and 16 SSU ha^?1 over the two grazing periods increased bulk density respectively by 2.73%, 6.67% and 8.945% and compaction by 10.90%, 16.78% and 20.90%. No grazing also increased bulk density and soil compaction and decreased infiltration rate. Light stocking (4 SSU ha^?1) influenced all soil parameters most favourably. From a hydrologic point of view, grazing levels and rotation schemes need to be tailored for sustainable utilization of arid subshrub/grass vegetation by livestock.     

Inorganic phosphorus fractions in the rhizosphere of xerophytic shrubs in the Alxa Desert

In spite of the extremely low phosphorus (P) availability in soils of the Alxa Desert region (Inner-Mongolia, China), many shrubs grow well there. The objective of this study was to investigate the status of inorganic phosphorus (Pi) fractions in the rhizosphere of xerophytic shrubs. For all five selected shrubs, soil pH in the rhizosphere decreased by 0.4–0.8 units and the total P concentrations were greater than those in the corresponding bulk soils. In the rhizosphere of Reaumuria soongorica, Olsen P concentration was lower than that in the bulk soil. In general, the order of Pi fractions was Ca₁₀–P > Ca₈–P > Al–P > Fe–P > Ca₂–P > O–P. The concentrations of all Pi fractions varied significantly with rhizosphere and corresponding bulk soils. The results of stepwise regression showed that Olsen P concentration in rhizosphere and bulk soils was contributed by different Pi fractions. The correlation analysis showed that the relationships between Pi fractions differed between rhizosphere and bulk soils. These results indicated that the soil Pi fractions are significantly affected by root activities, differing between the rhizosphere and bulk soils, and different xerophytic shrubs exhibited significantly different effect on soil Pi fractions.     

Spatiotemporal heterogeneity of soil fertility in the Central Monte desert (Argentina)

In arid environments, soil fertility exhibits a high degree of spatial and temporal heterogeneity, which results from high climatic variability seasonally and heterogeneous plant distribution. However, because most desert areas have been altered by human activities, heterogeneous fertility would originate from grazing or logging activities. We evaluated spatial and temporal heterogeneity of soil fertility in cattle-excluded sites under and outside woody plant cover (Prosopis flexuosa and Larrea divaricata), and in sites disturbed by tree removal during wet and dry season in Ñacuñán Biosphere Reserve (Central Monte desert of Argentina). Soil organic matter, fulvic acids, bioavailable organic matter, and nitrate were lower outside plant canopy (8.9 mg g^?1, 0.03 mg g^?1, 8.2 mg g^?1, and 4.17 mg kg^?1, respectively). Total N, humic acids, and abundance of microbial functional groups did not show differences among sites. Most parameters differed between seasons, tending to be higher in the wet season. Overall soils of Ñacuñán Reserve are characterized by: a) more homogenous spatial pattern than expected from woody plant presence; b) very heterogeneous temporal pattern; and c) after two years, tree removal does not seem to induce infertile soil formation.     

Fluctuations of the Última Esperanza ice lobe (52°S), Chilean Patagonia,during the last glacial maximum and termination 1

We present a new record from the Última Esperanza region (51°25’-52°25'S), southwestern Patagonia, to unravel the timing and structure of glacial fluctuations during the Last Glacial Termination (T1). This sector of southern South America represents the only windward-facing continental landmass in the Southern Hemisphere that intersects the core of the Southern Westerly Wind belt.Geomorphic, stratigraphic and geochronological evidence indicate the following stages during and since the Last Glacial Maximum (LGM): (i) deposition of prominent moraine complexes during at least two advances dated between ~ 39 and > 17.5 ka; (ii) development of an ice-dammed proglacial lake (glacial lake Puerto Consuelo) accompanying ice recession; (iii) active deposition of moraine complexes at intermediate positions followed by recession at ≥ 15.2 ka; (iv) lake level drop and subsequent stabilization between 15.2-12.8 ka; (v) a glacial readvance in glacial lake Puerto Consuelo between 14.8-12.8 ka; (vi) ice recession, stabilization, and lake level lowering between 12.8-10.3 ka; and (vii) glacial withdrawal and disappearance of glacial lake Puerto Consuelo prior to 10.3 ka. By comparing our results with the chronologies from neighboring regions we explore whether there was a consistent temporal/geographic pattern of glacial fluctuations during the LGM and T1, and examine their implications at regional, hemispheric, and global scales. The correspondence of these variations with key paleoclimate events recorded in the Southern and the Northern Hemispheres suggest a common forcing that, most likely, propagated through the atmosphere. Regional heterogeneities at millennial timescales probably reflect the influence of processes related to deep ocean circulation, and changes in the position/intensity of the Antarctic Polar Front and Southern Westerly Winds.     

Environmental control of seed dormancy and germination in the short-lived Olimarabidopsis pumila (Brassicaceae)

The purpose of our study was to better understand seed germination ecology of the spring annual short-lived Olimarabidopsis pumila, which grows in the Gurbantonggut Desert, China. Seeds underwent after-ripening at 4, 20 ± 2 (room temperature) and 30 °C. After dormancy was broken, germination capacity was a function of temperature and presence of light. For the temperature range studied (4–30 °C), germination capacity was significantly higher between 15 and 25 °C than at temperatures above or below them. Alternating temperatures of 20/10, 25/10 and 25/15 °C were favorable for germination. Although GA₃ did promote dark germination of seeds, GA₃ did not replace light for germination. Seeds germinated to >75% if light exposure time was over 8 h and temperature and moisture conditions were favorable. Seeds were able to germinate at relatively low water potentials (83% at ?0.41 MPa), but decreasing water potentials produced detrimental effects on germination percentage and rate. Thus, dormancy characteristics and germination behavior of O. pumila seeds ensure that germination occurs in the desert only when soil moisture conditions are favorable for seedling establishment and survival.     

Noble gases of the Yamato 000027 and Yamato 000097 lherzolitic shergottites from Mars

We used total melting and stepwise heating methods to measure noble gases within bulk samples from Yamato 000027 and Yamato 000097 lherzolites as well as a melt-vein sample from Yamato 000027. He and Ne are dominated by cosmogenic noble gases. The obtained cosmic-ray exposure age of 4.6 ± 1.5 Ma, an average age based on cosmogenic ³He, ²¹Ne, and ³⁸Ar for these samples, is consistent with the ages of other lherzolitic shergottites, indicating a common impact event for the ejection of lherzolites from Mars. Heavy noble gases released from the bulk samples at low temperatures were elementally fractionated terrestrial atmosphere. Martian noble-gas isotopic signatures, ⁴⁰Ar/³⁶Ar = 1900 and ¹²⁹Xe/¹³²Xe = 1.3, were observed at high temperatures (>1000 °C). The melt-vein sample released greater amounts of atmospheric Ar, Kr, and Xe at low temperatures than the bulk samples. Large amounts of Ar and Kr, as well as excess ⁴⁰Ar and ¹²⁹Xe, were evolved from the melt-vein sample at 1400 °C, and the gas shows very high ³⁶Ar/¹³²Xe (=3100) and ⁸⁴Kr/¹³²Xe (=76) values. Maximum ⁴⁰Ar/³⁶Ar and ¹²⁹Xe/¹³²Xe values of the melt sample were 1100 and 1.6, respectively, at 1600 °C. Cosmogenic Kr shows an absence of ⁸⁰Kr and ⁸²Kr produced by neutron capture on Br, which suggests a small pre-atmospheric body. Overall noble gas compositions for Y000027 and Y000097 support pairing for the Yamato 00 shergottites.     

Field validation of 1930s aerial photography: What are we missing?

Aerial photography from the 1930s serves as the earliest synoptic depiction of vegetation cover. We generated a spatially explicit database of shrub (Prosopis velutina) stand structure within two 1.8 ha field plots established in 1932 to address two questions: (1) What are the detection limits of panchromatic 1936 aerial photography?, and (2) How do these influence P. velutina biomass estimates? Shrub polygons were manually digitized on 1936 imagery and linked to 1932 field measurements of P. velutina canopy area. Aboveground 1932 P. velutina biomass was estimated using a site-specific allometric relationship for field-measured canopy area. Shrub canopy detection limits on the 1936 imagery were comparable to those reported for contemporary imagery. Based on a conservative shrub size detection threshold of 3.8 m², 5.8% of P. velutina biomass was missed. Spatial resolution (0.6 vs. 1.0 m) did not influence detection limits, but the overall accuracy of shrub cover estimates was greater on 1.0 m images. Presence of the sub-shrub Isocoma tenuisecta may also have significantly influenced estimates of P. velutina canopy area. These analyses illustrate the importance of standardizing aerial photo interpretation protocols, accounting for uncertainty estimating shrub biomass, and caution species-specific interpretations for historic aerial photography.