Small Test Site Research Articles

НАСІННА ПРОДУКТИВНІСТЬ СОСНИ КЕДРОВОЇ КОРЕЙСЬКОЇ (PINUS KORAIENSIS SIEB. ET ZUCC.) В МЕЖАХ ГАЛИЦЬКОГО НАЦІОНАЛЬНОГО ПРИРОДНОГО ПАРКУ


 
 
 
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 Інформація про авторів:
 Мандзюк Роман Іванович, канд. с.-г. наук, наук. співробітник. Email: romanmandziuk@gmail.com
 Харачко Тарас Іванович, канд. с.-г. наук, доцент, кафедра лісових культур і лісової селекції. Email: taras-forester@ukr.net
 Цитування за ДСТУ: Мандзюк Р. І., Харачко Т. І. Насінна продуктивність сосни кедрової корейської (Pinus Koraiensis Sieb. et Zucc.) в межах Галицького національного природного парку. Scientific Bulletin of UNFU. 2018, т. 28, № 3. С. 00–00.
 Citation APA: Mandziuk, R. I., & Kharachko, T. I. (2018). On Seed Productivity of the Pinus Koraiensis (Sieb. et Zucc.) in Halych National Nature Park. SBUNFU, 28(3), 00–00. https://doi.org/10.15421/40280300
 
 
 
 
 Наведено коротку характеристику сосни кедрової корейської та проведено історичний екскурс щодо його появи у лісових насадженнях Галицького національного природного парку (Галицький НПП). Проаналізовано сучасні напрями досліджень виду у світі та зроблено висновок щодо актуальності його досліджень в Україні, а саме: доцільність вивчення процесів шишко- та насіннєношення, які безпосередньо впливають на насінну продуктивність. Описано результати фенологічних спостережень та встановлено періодичність шишконошення виду на постійній лісонасінній ділянці у Галицькому НПП. Висвітлено результати дослідження біометричних показників шишок і насіння кедрової корейської сосни. Результати досліджень свідчать про високу насінну продуктивність інтродуцента в умовах підприємства та дають підстави висловити припущення про збільшення цього показника впродовж кількох найближчих десятиліть, одночасно зі збільшенням віку шишконосних дерев. Встановлено оптимальні терміни заготівлі лісонасінної сировини та виявлено чинник, що впливає на зменшення врожаю шишок. Висвітлено результати інвентаризації самосіву досліджуваного виду на пробних ділянках та зроблено аналіз його висотної структури. Одночасно з обліком самосіву, наведено найхарактерний місця його появи в насадженні та висунуто припущення щодо причин його масового випадання впродовж другого та третього років життя. Проведене дослідження підтвердило натуралізацію виду в умовах Галицького НПП і вказало на притаманну для нього досить високу насінну продуктивність. Результати досліджень свідчать про можливість ширшого впровадження цього цінного, для лісового господарства, виду у лісові насадження регіону.

Fractional cover mapping of spruce and pine at 1 ha resolution combining very high and medium spatial resolution satellite imagery

Increases in extreme weather events associated with climate change have the potential to put currently healthy forests at risk. One option to minimize this risk is the application of forest management measures aimed at generating species mixtures predicted to be more resilient to these threats. In order to apply such measures appropriately, forest managers need up-to-date, accurate and consistent forest maps at relatively fine spatial resolutions. Cost efficiency is a major factor when creating such maps. Taking European spruce (Picea abies) and Scots pine (Pinus sylvestris) as an example, this paper describes an innovative approach for mapping two tree species using a combination of commercial very high resolution WorldView-2 (WV2) images and Landsat time series data. As a first step, this study used a supervised object-based classification of WV2 images covering relatively small test sites distributed across the region of interest. Using these classification maps as training data, wall-to-wall mapping of fractional coverages of spruce and pine was achieved using multi-temporal Landsat data and Random Forests (RF) regression. The method was applied for the entire state of Bavaria (Germany), which comprises a total forested area of approximately 26,000km2. As applied here, this two-step approach yields consistent and accurate maps of fractional tree cover estimates with a spatial resolution of 1ha. Independent validation of the fractional cover estimates using 3780 reference samples collected through visual interpretation of orthophotos produced root-mean-square errors (RMSE) of 11% (for spruce) and 14% (for pine) with almost no bias, and R2 values of 0.74 and 0.79 for spruce and pine, respectively. The majority of the validation samples (75% (spruce) and 84% (pine)) were modeled within the assumed uncertainty of ±15% of the reference sample. Accuracies were significantly better compared to those achieved using a single-step classification of Landsat time series data at the pixel level (30m), because the two-step approach better captures regional variation in the spectral signatures of target classes. Moreover, the increased number of available reference cells mitigates the impact of occasional errors in the reference data set. This two-step approach has great potential for cost-effective operational mapping of dominant forest types over large areas.

Combination of statistical and physically based methods to assess shallow slide susceptibility at the basin scale

Abstract. Approaches used to assess shallow slide susceptibility at the basin scale are conceptually different depending on the use of statistical or physically based methods. The former are based on the assumption that the same causes are more likely to produce the same effects, whereas the latter are based on the comparison between forces which tend to promote movement along the slope and the counteracting forces that are resistant to motion. Within this general framework, this work tests two hypotheses: (i) although conceptually and methodologically distinct, the statistical and deterministic methods generate similar shallow slide susceptibility results regarding the model's predictive capacity and spatial agreement; and (ii) the combination of shallow slide susceptibility maps obtained with statistical and physically based methods, for the same study area, generate a more reliable susceptibility model for shallow slide occurrence. These hypotheses were tested at a small test site (13.9 km2) located north of Lisbon (Portugal), using a statistical method (the information value method, IV) and a physically based method (the infinite slope method, IS). The landslide susceptibility maps produced with the statistical and deterministic methods were combined into a new landslide susceptibility map. The latter was based on a set of integration rules defined by the cross tabulation of the susceptibility classes of both maps and analysis of the corresponding contingency tables. The results demonstrate a higher predictive capacity of the new shallow slide susceptibility map, which combines the independent results obtained with statistical and physically based models. Moreover, the combination of the two models allowed the identification of areas where the results of the information value and the infinite slope methods are contradictory. Thus, these areas were classified as uncertain and deserve additional investigation at a more detailed scale.

OVERLAND FLOW ANALYSIS USING TIME SERIES OF SUAS-DERIVED ELEVATION MODELS

With the advent of the innovative techniques for generating high temporal and spatial resolution terrain models from Unmanned Aerial Systems (UAS) imagery, it has become possible to precisely map overland flow patterns. Furthermore, the process has become more affordable and efficient through the coupling of small UAS (sUAS) that are easily deployed with Structure from Motion (SfM) algorithms that can efficiently derive 3D data from RGB imagery captured with consumer grade cameras. We propose applying the robust overland flow algorithm based on the path sampling technique for mapping flow paths in the arable land on a small test site in Raleigh, North Carolina. By comparing a time series of five flights in 2015 with the results of a simulation based on the most recent lidar derived DEM (2013), we show that the sUAS based data is suitable for overland flow predictions and has several advantages over the lidar data. The sUAS based data captures preferential flow along tillage and more accurately represents gullies. Furthermore the simulated water flow patterns over the sUAS based terrain models are consistent throughout the year. When terrain models are reconstructed only from sUAS captured RGB imagery, however, water flow modeling is only appropriate in areas with sparse or no vegetation cover.

OVERLAND FLOW ANALYSIS USING TIME SERIES OF SUAS-DERIVED ELEVATION MODELS

Abstract. With the advent of the innovative techniques for generating high temporal and spatial resolution terrain models from Unmanned Aerial Systems (UAS) imagery, it has become possible to precisely map overland flow patterns. Furthermore, the process has become more affordable and efficient through the coupling of small UAS (sUAS) that are easily deployed with Structure from Motion (SfM) algorithms that can efficiently derive 3D data from RGB imagery captured with consumer grade cameras. We propose applying the robust overland flow algorithm based on the path sampling technique for mapping flow paths in the arable land on a small test site in Raleigh, North Carolina. By comparing a time series of five flights in 2015 with the results of a simulation based on the most recent lidar derived DEM (2013), we show that the sUAS based data is suitable for overland flow predictions and has several advantages over the lidar data. The sUAS based data captures preferential flow along tillage and more accurately represents gullies. Furthermore the simulated water flow patterns over the sUAS based terrain models are consistent throughout the year. When terrain models are reconstructed only from sUAS captured RGB imagery, however, water flow modeling is only appropriate in areas with sparse or no vegetation cover.

Automated lithological mapping using airborne hyperspectral thermal infrared data: A case study from Anchorage Island, Antarctica

The thermal infrared portion of the electromagnetic spectrum has considerable potential for mineral and lithological mapping of the most abundant rock-forming silicates that do not display diagnostic features at visible and shortwave infrared wavelengths. Lithological mapping using visible and shortwave infrared hyperspectral data is well developed and established processing chains are available, however there is a paucity of such methodologies for hyperspectral thermal infrared data. Here we present a new fully automated processing chain for deriving lithological maps from hyperspectral thermal infrared data and test its applicability using the first ever airborne hyperspectral thermal data collected in the Antarctic. A combined airborne hyperspectral survey, targeted geological field mapping campaign and detailed mineralogical and geochemical datasets are applied to small test site in West Antarctica where the geological relationships are representative of continental margin arcs. The challenging environmental conditions and cold temperatures in the Antarctic meant that the data have a significantly lower signal to noise ratio than is usually attained from airborne hyperspectral sensors. We applied preprocessing techniques to improve the signal to noise ratio and convert the radiance images to ground leaving emissivity. Following preprocessing we developed and applied a fully automated processing chain to the hyperspectral imagery, which consists of the following six steps: (1) superpixel segmentation, (2) determine the number of endmembers, (3) extract endmembers from superpixels, (4) apply fully constrained linear unmixing, (5) generate a predictive classification map, and (6) automatically label the predictive classes to generate a lithological map. The results show that the image processing chain was successful, despite the low signal to noise ratio of the imagery; reconstruction of the hyperspectral image from the endmembers and their fractional abundances yielded a root mean square error of 0.58%. The results are encouraging with the thermal imagery allowing clear distinction between granitoid types. However, the distinction of fine grained, intermediate composition dykes is not possible due to the close geochemical similarity with the country rock.

Use of terrestrial laser scanning data to drive decimetric resolution urban inundation models

The advent of airborne LIDAR sparked a renewed research drive in two-dimensional hydraulic modelling at the turn of the millennium due to its ability to rapidly generate accurate DEMs over wide areas. Terrestrial LIDAR applies the same principle but uses a mobile ground-based platform, allowing rapid collection of terrain data in urban areas at decimetric scale. Here we apply two computationally efficient hydraulic models to DEMs of a small urban test site in Alcester, UK, derived from terrestrial and airborne LIDAR data at 10cm and 1m scales. The first model, LISFLOOD-FP, is a 2D raster-based model employing a simplified formulation of the de St. Venant equations, whilst the second model, ISIS-FAST, employs a proprietary rapid flood spreading algorithm. The response of the models to changes in DEM resolution and data source are analysed and compared across two event scales. For the first time we show that a flood wave propagating across an urban domain responds to small scale topographic features, such as street kerbs and road surface camber, which are not represented in airborne data but which are resolved by the terrestrial laser scanner. Importantly these features are preserved even if the 10cm terrestrial data are degraded to the 1m scale of the airborne DEM. The results indicate that inclusion of these features improves the representation of hydraulic connectivity over the DEM, and hence flood risk estimation. LISFLOOD-FP is shown to be more robust to changes in DEM resolution than ISIS-FAST due to the momentum conservation inherent to the simplified shallow water formulation, but the reduced computational requirements of ISIS-FAST at 10cm scale allow it to be used for ensemble simulations. The extra detail inherent in terrestrial laser scanning data is advantageous where accurate representation of surface features is required, with potential benefit to high asset-value flood risk analysis and future studies into coupled surface/sewer and pluvial urban inundation models.

Anthrax Letters in an Open Office Environment: Effects of Selected CDC Response Guidelines on Personal Exposure and Building Contamination

In 2001, letters filled with a powder containing anthrax (Bacillus anthracis) spores were delivered by mail to a number of governmental and media locations within the United States. In response, the U.S. Centers for Disease Control and Prevention (CDC) provided guidelines for office personnel who might encounter a letter containing suspicious powder. These guidelines were developed during the crisis and in the absence of experimental data from laboratory or field investigations. An obvious need thus exists for quantitative and scientific verification for validation of these guidelines. This study attempts to address this need, adapting earlier work that used a multiple small office test site to create a model system in an open office test site in a vacated office building in which Bacillus atrophaeus spores (as a simulant for B. anthracis spores) were released by opening a letter. Using SF6 as a tracer gas, smoke tubes (containing stannic chloride) to visualize airflow, culturable aerosol sampling, and aerosol spectrometry we were able to characterize airflow and unmitigated spore aerosol dissemination within the office test site. Subsequently, two scripted test scenarios were used to reproduce selected portions of the existing CDC response guidelines and a modified version where the contaminated letter opener warned co-workers to evacuate then waited 5 min before doing so himself. By not leaving together with other co-workers, the risk of the letter opener cross-contaminating others was eliminated. The total potential spore aerosol exposure of the letter opener was not affected by remaining still and waiting 5 min to allow co-workers to escape first before leaving the office. Closing office doors and quickly deactivating the heating, ventilation, and air conditioning system significantly reduced spore aerosol concentrations outside the main open office in which they had been released.

Large area forest stem volume mapping in the boreal zone using synergy of ERS-1/2 tandem coherence and MODIS vegetation continuous fields

ERS-1/2 tandem coherence was reported to have high potential for the mapping of boreal forest stem volume (e.g. Santoro et al., 2002, 2007a; Wagner et al., 2003; Askne & Santoro, 2005). Large-scale application of the data for forest stem volume mapping, however, is hindered by the variability of coherence with meteorological and environmental acquisition conditions. The traditional way of stem volume retrieval is based on the training of models, relating coherence to stem volume, with the aid of forest inventory data which is generally available for a few small test sites but not for large areas. In this paper a new approach is presented that allows model training using the MODIS Vegetation Continuous Fields canopy cover product (Hansen et al., 2003) without further need for ground data. A comparison of the new approach with the traditional regression-based and ground-data dependent model training is presented in this paper for a multi-seasonal ERS-1/2 tandem dataset covering several well known Central Siberian forest sites. As a test scenario for large-area application, the approach was applied to a multi-seasonal ERS-1/2 tandem dataset of 223 ERS-1 and ERS-2 image pairs covering Northeast China (~ 1.5 million km 2) to map four stem volume classes (0–20, 20–50, 50–80, and > 80 m 3/ha).

Probabilistic landslide risk analysis considering direct costs in the area north of Lisbon (Portugal)

The purpose of the present study is the analysis of landslide risk for roads and buildings in a small test site (20 km 2) in the area north of Lisbon (Portugal). For this purpose, an evaluation is performed integrating into a GIS information obtained from multiple sources: (i) landslide hazard; (ii) elements at risk; and (iii) vulnerability. Landslide hazard is assessed on a probabilistic basis for three different types of slope movement (shallow translational slides, translational slides and rotational slides), based on some assumptions such as: (i) the likelihood of future landslide occurrence can be measured through statistical relationships between past landslide distribution and specified spatial data sets considered as landslide predisposing factors; and (ii) the rainfall combination (amount–duration) responsible for past slope instability within the test site will produce the same effects (i.e. same type of landslides and similar total affected area), each time they occur in the future. When the return period of rainfall triggering events is known, different scenarios can be modelled, each one ascribed to a specific return period. Therefore, landslide hazard is quantitatively assessed on a raster basis, and is expressed as the probability for each pixel (25 m 2) to be affected by a future landslide, considering a rainfall triggering scenario with a specific return period. Elements at risk within the test site include 2561 buildings and roads amounting to 169 km. Values attributed to elements at risk were defined considering reconstruction costs, following the guidelines of the Portuguese Insurance Institute. Vulnerability is considered as the degree of loss to a given element resulting from the occurrence of a landslide of a given magnitude. Vulnerability depends not only on structural properties of exposed elements, but also on the type of process, and its magnitude; i.e., vulnerability cannot be defined in absolute terms, but only with respect to a specific process (e.g. vulnerability to shallow translational slides). Therefore, vulnerability was classified for the three landslide groups considered on hazard assessment, taking into account: (i) landslide magnitude (mean depth, volume, velocity); (ii) damage levels produced by past landslide events in the study area; and (iii) literature. Finally, a landslide risk analysis considering direct costs was made in an automatic way crossing the following three layers: (i) Probabilistic hazard map for a landslide type Z, considering a particular rainfall triggering scenario whose return period is known; (ii) Vulnerability map (values from 0 to 1) of the exposed elements to landslide type Z; and (iii) Value map of the exposed elements, considering reconstruction costs.

Airborne laser scanning and usefulness for hydrological models

Abstract. Digital terrain models form the basis for distributed hydrologic models as well as for two-dimensional hydraulic river flood models. The technique used for generating high accuracy digital terrain models has shifted from stereoscopic aerial-photography to airborne laser scanning during the last years. Since the disastrous floods 2002 in Austria, large airborne laser-scanning flight campaigns have been carried out for several river basins. Additionally to the topographic information, laser scanner data offer also the possibility to estimate object heights (vegetation, buildings). Detailed land cover maps can be derived in conjunction with the complementary information provided by high-resolution colour-infrared orthophotos. As already shown in several studies, the potential of airborne laser scanning to provide data for hydrologic/hydraulic applications is high. These studies were mostly constraint to small test sites. To overcome this spatial limitation, the current paper summarises the experiences to process airborne laser scanner data for large mountainous regions, thereby demonstrating the applicability of this technique in real-world hydrological applications.

Variations of backscatter strength along the super slow-spreading Southwest Indian Ridge between 57°E and 70°E

Simrad EM12 backscatter strength data of the Southwest Indian Ridge (SWIR), between 57°E and 70°E, are used to reveal the along-axis segmentation of this super slow-spreading ridge. The backscatter properties of different geologic domains, like bathymetric highs and oblique basins within the rift valley, are characterized using 66 small test sites. We show that backscatter strength is higher on bathymetric swells, corresponding to segment centres, and lower in deep oblique basins corresponding to axial non-transform discontinuities and fracture zones. This contrast between segment centres and discontinuities is produced by both a thicker sediment cover and less frequent volcanic eruptions at segment ends. Using the model of Mitchell (1993), sediments have been estimated to be 2 to 5 m thicker in these areas than at segment centres. The distribution of the seamounts within the rift valley is controlling the long-wavelength variations of the mean backscatter strength calculated along the axis. Lower densities of seamounts and thicker sediments are producing lower and heterogeneous reflectivity levels in the deepest part of the axial valley floor between 61°45′E and 63°45′E. We propose that cooler mantle temperatures inducing construction of fewer volcanoes occur beneath this part of the ridge. The mean backscatter strength along the SWIR axis decreases dramatically toward the Rodrigues Triple Junction suggesting that volcanic production is reduced between 68°20′E and 69°20′E and that the transition from amagmatic tectonic deformation at the triple junction to new seafloor spreading occurs between 69°20′E and 70°E.

Increased ablation of Wisconsin ice in eastern north Greenland: observations and modelling

In Kronprins Christian Land at 80° N in eastern north Greenland, it has been observed that the surface of the Wisconsin ice is significantly darker than the Holocene ice found immediately upstream from a transition located 710 m from the ice margin. δ 18O analysis has shown the dark surface is of Wisconsin origin. Deep ice cores from the Greenland ice sheet all indicate that the Wisconsin ice contains orders of magnitude more microparticles which could he the reason for the dark appearance of the Wisconsin surface. Photographic documentation, spectral surface-albedo measurements and satellite-image analysis all indicate a reduced albedo of Wisconsin ice. The effect of this reduced albedo is not confirmed by the ablation measurements. However, measurements of ablation variability within small test sites has documented that large errors will arise if only one stake per measuring point is used. Energy-balance calculations show ablation rates should be 10–70%, i.e. 1.8–8.4 mm d−1, respectively, less than experienced. Additionally, a satellite-image analysis shows even higher albedo contrasts 20–30 km to the south of our transect locality. Immediately after the termination of the ice age, most of the surface in the ablation zone consisted of this low-reflectance ice. So, in the early Holocene, the dark ice of Wisconsin origin is likely to have resulted in higher ablation rates than previously considered. This may probably partly explain the fast rate of retreat/disintegration of the ice sheets in the Northern Hemisphere, after the termination of the Wisconsin ice age.

Increased ablation of Wisconsin ice in eastern north Greenland: observations and modelling

In Kronprins Christian Land at 80° N in eastern north Greenland, it has been observed that the surface of the Wisconsin ice is significantly darker than the Holocene ice found immediately upstream from a transition located 710 m from the ice margin. δ18O analysis has shown the dark surface is of Wisconsin origin. Deep ice cores from the Greenland ice sheet all indicate that the Wisconsin ice contains orders of magnitude more microparticles which could he the reason for the dark appearance of the Wisconsin surface.Photographic documentation, spectral surface-albedo measurements and satellite-image analysis all indicate a reduced albedo of Wisconsin ice. The effect of this reduced albedo is not confirmed by the ablation measurements. However, measurements of ablation variability within small test sites has documented that large errors will arise if only one stake per measuring point is used. Energy-balance calculations show ablation rates should be 10–70%, i.e. 1.8–8.4 mm d−1, respectively, less than experienced. Additionally, a satellite-image analysis shows even higher albedo contrasts 20–30 km to the south of our transect locality.Immediately after the termination of the ice age, most of the surface in the ablation zone consisted of this low-reflectance ice. So, in the early Holocene, the dark ice of Wisconsin origin is likely to have resulted in higher ablation rates than previously considered. This may probably partly explain the fast rate of retreat/disintegration of the ice sheets in the Northern Hemisphere, after the termination of the Wisconsin ice age.

Comparative study of dermabrasion, phenol peel, and acetic acid peel

Six areas of the face and forehead of a 36-year-old white female presenting with a benign congenital blue nevus of the skin were treated by dermabrasion, bichloracetic acid, and the classic phenol peel. Comparative results at six months showed each of these methods to be approximately equal in the depth of penetration and in the quality of skin on healing. However, in these small test sites, dermabrasion appeared to remove pigment slightly more efficiently. Therefore, her forehead and cheeks were treated with dermabrasion and subsequently with chemical peel. An attempt was made to touch up the dermabraded areas with acetic acid. Full thickness burns occurred, which resulted in thick scarring that required many months to finally heal. We conclude that at least in the treatment of pigmented lesions, the modalities of phenol, acetic acid, and dermabrasion are approximately equal.

Combination of digital elevation models with SPOT-1 HRV multispectral imagery for reflectance factor mapping

Digital numbers in SPOT-1 HRV multispectral imagery were transformed to reflectance factor values. This approach is based on a simplified-scene radiance equation that is developed in this paper. The values of some parameters needed in the equation such as path radiance, total normal optical thickness, and diffuse spectral irradiance were estimated by using multiple linear regression in a small test site of homogeneous ground cover, located within the study area. The calculated values of reflectance factors were presented by dimensionless digital numbers ranging from 0 to 255, which corresponds respectively to the values of reflectance factors from 0 to 1. The feasibility of this approach has been tested against the SPOT-1 HRV multispectral imagery above a canopy of Picaussel Forest of the Quillan region in the eastern pyrenean mountain in France.

ON REGIONAL OPTIMISATION OF GRID AND RELAXATION PARAMETER FOR FINITE DIFFERENCE SOLUTION OF POISSONS' EQUATION IN REVERSE BIASED PLANAR TYPE p‐n JUNCTIONS

The optimisation of grid structure and relaxation parameter is considered in this paper in connection with two‐dimensional finite difference solution of Poisson's equation for determining the field profile in a reverse biased planar type p?n junction. By dividing the planar junction into regions with rectangular and circular symmetry, regional optimisations have been carried out using small area test sites. Having obtained the optimal grid size and relaxation parameter for each region, the complete solution was obtained easily with very fast convergence. The method involved in this kind of regional optimisation is presented in detail with discussions on its comparative usefulness with other known techniques.

Overview of the NERC airborne thematic mapper campaign of September 1982

Abstract In September 1982, NERC funded an airborne campaign using a Daedulus airborne thematic mapper multispectral scanner. A total of 18 sites were flown for 10 experimental groups in the U.K. The major aim of the survey was to provide spectrally simulated satellite data for small test sites, particularly in support of ongoing LANDSAT-4 investigations. However, the survey demonstrated that in certain situations when timely satellite data cannot reasonably be expected, e.g. tidal sites, aircraft provide an important data set. This brief paper provides a summary of the NERC airborne campaign and an introduction to the related papers to be found in this issue.

An all-day test for the evaluation of a topical sunscreen

In order to examine the relevance of high sun protection factors (SPF) to medically important sunburn protection under natural exposure conditions, an all-day testing procedure using twenty-four sun-sensitive subjects was designed. Three small test areas above each scapula were used to compare sunscreen lotions with SPFs of 17 and 6 to a vehicle-treated site. In addition, all of the sun-exposed glabrous skin areas were treated with the highest SPF lotion. One side of each subject's torso and face was also retreated during the exposure period. The subjects were exposed to approximately fifteen times the minimal erythemal dose of ultraviolet B (UVB) during the test, and all received essentially complete protection with the SPF 17 lotion. No difference was seen between one and two applications. On the small test sites, both the SPF 17 and SPF 6 lotions provided protection from sunburn; however, the SPF 17 lotion provided significantly better protection than the SPF 6 lotion. Importantly, tanning was produced without associated or preceding redness, and these tanned areas persisted for 2 weeks or more. It was concluded that under natural exposure conditions when the integrity of the sunscreen film has not been compromised, a single application of the highest SPF sunscreen can protect sun-sensitive subjects from sunburn during a day-long sun exposure and that this protection is better than that afforded by a sunscreen with a substantially lower SPF.