Dune and Vegetation Stability at South Padre Island, Texas, United States of America

Padre Island is the longest of five barrier islands occurring along the Texas Gulf Coast. South Padre Island is separated from the northern two-thirds of the island by the Mansfield Channel. The composition and pattern of vegetation on South Padre Island are relatively well known, but data on the interrelationship of dune and vegetation stability are lacking. We hypothesized that (1) there should be an inverse relationship between elevation change and percent cover on transects across the nearshore dunes of South Padre Island; and (2) percent cover, species composition, and species importance should be most stable where elevation change was least. We tested these hypotheses using three study sites differing in vegetation abundance. Elevation measurements were taken at 1.0-m intervals along three transects at each site using survey-grade Global Positioning System equipment. Vegetation abundance was determined in 10-m intervals along each transect. No sites or topographic zones were devoid of elevation change. Even a site that had a mean percent cover of 65.1% had a mean elevation change of 15.6 cm. However, cover does not have to be great to provide considerable stability. There was no significant difference in elevation change at Site 1, where cover was 57%, and Site 2, where cover was only 12.5%. As hypothesized, there was a significant inverse correlation between elevation change and percent cover when analyzed over all transects and sites, but the relationship did not hold for all sites or topographic zones when these were examined separately. Lack of correlation may be due to differences among sites and zones in the number of different perturbations and their intensities and frequencies. Only Site 2 showed a significant difference in percent cover between the initial and final samples. Species composition and importance were more stable where elevation changes were low

Survivorship and Growth Among Three Developmental Stages of Black Mangrove (Avicennia germinans) Seedlings in Southernmost Texas

Black mangrove is useful for shoreline stabilization in Texas and Mexico but there is insufficient information regarding propagule survivorship and seedling growth. We compared survivorship and growth of three develop-mental groups of black mangrove seedlings planted on three dredge spoil islands in the Lower Laguna Madre of Texas, to better understand optimum planting strategy. Each spoil island had 100 seedlings without emergent radicles, 100 seedlings with emergent radicles, and 75 head-started seedlings. Survivorship of seedlings with and with-out emergent radicles was low, (0-16%). Survivorship of head-started seedlings was higher, (60 – 62.7%). Varia-tion in survivorship among developmental categories was significant but variation among islands was not. The 16 surviving seedlings with emergent radicles censused 346 days after planting were similar in mean height (32.9 cm) and mean number of pairs of leaves (13.2) to head-started seedlings grown for 376 days (105 days in nursery, 271 days on Island 1). Growth rates for height ranged from 0.041 cm/day to 0.058 cm/day. Growth in mean pairs of leaves ranged from 0.042 pairs/day to 0.051 pairs/day. Comparison of the person-days required to have 300 seed-lings alive one year after field planting shows that head-starting is clearly the preferable planting strategy

Detection of Temporal Changes in Vegetative Cover on South Padre Island, Texas Using Image Classifications Derived from Aerial Color-Infrared Photographs

Supervised image classifications developed from 23 x 23 cm aerial color-infrared aerial photographs (1:5,000 scale) were used to evaluate temporal changes in vegetative cover occurring within three 150 x 300-m research sites on South Padre Island, Texas. Use of high-resolution digitized imagery (ground pixel resolution of ca. 0.1 m) and survey-grade GPS for positional measurements of ground control points (20-25 1.0m2 targets within each research site) resulted in consistently high levels of geometric accuracy, with root mean square errors (RMSEs) ranging between 0.397 – 2.867. Similarly, use of relatively simple information categories (dry and wet sand, live and dead vegetative cover, and water) resulted in supervised image classifications with consistently high levels of overall thematic accuracy (90.0 – 98.0%). Temporal comparisons of image classifications using a cross-tabulation procedure indicated that changes in total vegetative cover had been minimal at most locations during the course the two-year study (2003-2005). However, a localized but significant disruption of native vegetation caused by the dumping of sand by highway maintenance crews was detected in one of the study sites (2004), and ground inspection revealed numerous other sand-dumping sites at various locations on the barrier island. In the first situation, comparison of CIR aerial photographs acquired before and after the sand-dumping incident provided a reliable means by which to evaluate the extent of damage caused by the dumped sand, and to monitor its eventual recovery as a result of recolonization by native plant species

Detection of Incipient Pest Infestations on Glasshouse Crops Using Multispectral Imagery and a Common Vegetation Index

Research was conducted to evaluate the effectiveness of multispectral (conventional color and color infrared) imagery and a common vegetation index (simple ratio) for detecting incipient infestations of spider mites (Tetranychus spp.; Acari: Tetranychidae) and false spider mites (Brevipalpus spp.; Acari: Tenupalpidae) on selected crops under glasshouse conditions. Although damaging infestations of both mite species were associated with intense feeding injury which was readily detectable by visual inspection, subtle levels of foliar damage caused by the two mite species were difficult to detect by visual inspection and were not readily distinguishable from undamaged (healthy) foliage in conventional color (CC) or color infrared (CIR) imagery. In contrast, foliage exhibiting subtle levels of mite feeding injury was readily distinguished from healthy foliage in derivative imagery based on the Simple Ratio (SR), a vegetation index defined as the ratio of near-infrared to red reflectance (700-1100 nm and 600-700 nm, respectively) for each pixel in the imagery. CIR and SR images were shown to be considerably more effective than CC imagery in the initial detection and subsequent monitoring of a spider mite infestation on glasshouse cucumbers which increased from incipient to annihilative levels within a period of approximately six weeks. The rationale for and potential uses of CC, CIR, and derivative imagery based on SR and other vegetative indices for monitoring pest infestations on glasshouse crops are discussed

Evaluation of Artificial Lighting Sources for the Acquisition of Color Infrared Imagery Under Glasshouse Conditions

English: Research was conducted to evaluate the spectral properties, illumination intensities and lighting patterns of four basic categories of bulbs and lamps which could conceivably serve as sole lighting sources for the acquisition of color infrared (CIR) imagery under glasshouse conditions. Bulbs and lamps in two major categories (fluorescent tubes and sodium- and mercury-vapor glasshouse lamps) were deemed unsuitable for this purpose either because they emitted little or no nearinfrared (NIR) radiation or because they imparted an overall bluish cast that seriously degraded the quality of CIR imagery. All of the incandescent and quartz halogen lamps evaluated in these studies exhibited spectral properties suitable for CIR image acquisition, i.e., they emitted relatively high levels of both visible and NIR radiation. However, most bulbs and lamps in these categories were characterized by either inadequate levels of illumination or reflectors that produced a circular lighting pattern in which luminosity varied substantially from the center portion of the image to the edges. The most suitable bulb evaluated was a heavy-duty (500W) quartz halogen lamp with a rectangular reflector which, when modified by the addition of crumpled aluminum foil to the reflector housing, produced adequate levels of illumination that was distributed in a near-uniform pattern across the target area. Color infrared imagery of plant foliage acquired using this lamp as a sole lighting source was comparable in quality to imagery of the same plant material acquired under natural lighting conditions. The performance of this particular lamp is used to exemplify the stringent requirements of any lamp under consideration as a sole lighting source for CIR image acquisition within the glasshouse environment. Spanish: Se investigaron las propiedades espectrales, las intensidades de iluminación y los patrones de luz de cuatro tipos básicos de bulbos y lámparas que podrían servir como fuentes únicas de luz para la adquisición de imágenes infrarrojas (CIR) bajo condiciones de invernadero. No se consideraron adecuados para este propósito los bulbos y las lámparas en dos categorías importantes (tubos de fluorescencia y lámparas de invernadero de vapor de mercurio y sodio ya que o emitieron muy poca o ninguna radiación infrarroja cercana (NIR) o porque impartieron un tono azul que degradó seriamente la calidad de las imágenes CIR. Todas las lámparas incandescentes y de halógeno de cuarzo evaluadas en estos estudios exhibieron propiedades espectrales adecuadas para la adquisición de imágenes infrarrojas, por ejemplo, emitieron niveles relativamente altos de radiación visible y de radiación cercana al infrarrojo. Sin embargo, las mayoría de los bulbos y lámparas en esta categoría se caracterizaron por producir niveles inadecuados de iluminación o por producir un patrón de luz circular en el cual la luminosidad varió substancialmente de la porción central de la imagen a las orillas. El bulbo probado que resultó mas adecuado fue la lámpara de halógeno-cuarzo con un reflector rectangular el cual, cuando se modificó por la adición de papel aluminio arrugado al nicho del reflector, produjo niveles adecuados de iluminación que se distribuyeron en un patrón casi uniforme a lo largo de la área expuesta. Las imágenes infrarrojas del follaje vegetal tomadas usando esta lámpara como única fuente de luz fueron comparables en calidad a las imágenes del mismo follaje tomadas bajo condiciones de luz natural. El desempeño de esta lámpara en particular es usado para ejemplificar los estrictos requerimientos para cualquier lámpara que sea usada como única fuente de luz para la adquisición de imágenes de color infrarrojo en ambiente de invernadero

Detecting Stress in Glasshouse Plants Using Color Infrared Imagery: A Potential New Application for Remote Sensing

English: Studies were conducted to evaluate the effectiveness of color infrared (CIR) film for detecting physiological stress in plants located within glasshouse structures. Spectroradiometer measurements obtained within and outside of a structure constructed of polycarbonate plastic indicated no significant attenuation or disruption of visible and near-infrared radiation entering the structure. CIR photographs of cucumber seedlings (Cucumis sativus) obtained within the greenhouse were comparable in quality to those obtained outside the structure, and clearly distinguished between foliage of healthy plants and those subjected to a moderate level of nitrogen stress. In CIR imagery of a trifoliate orange tree (Poncirus trifoliata (L.) Raf.) obtained within a greenhouse constructed of yellow fiberglass panels, leaves damaged by citrus red mites (Panonychus citri [McGregor]) were distinguishable from healthy foliage, and the distribution of damaged leaves on the tree itself was clearly evident. These results suggest that remote sensing techniques which have been used successfully to monitor conventional field crops are readily extendable to the commercial glasshouse environment with certain modifications. Spanish: Se condujeron estudios para evaluar la eficacia de la película infrarroja de color (CIR) para detectar el estrés fisiológico en las plantas situadas dentro de un invernadero. Las mediciones del spectroradiómetro obtenidas dentro y fuera de un invernadero construido con plástico de policarbonato no indicaron ninguna atenuación o interrupción significativa de la radiación visible y del cercano infrarrojo que penetraba al invernadero. Las fotografías con CIR de las plantas de semillero de pepino (Cucumis sativus) obtenidas dentro del invernadero fueron comparables en calidad a aquellas obtenidas fuera de este, y distinguieron claramente entre el follaje de plantas sanas y de aquellas sometidas a un nivel moderado de estrés de nitrógeno. En imágenes de CIR de un naranjo trifoliado (Poncirus trifoliata (L.) Raf.) obtenidas dentro de un invernadero construido de paneles amarillos de fibra de vidrio, las hojas dañadas por el ácaro rojo de los cítricos (Panonychus citri [McGregor]) se distinguieron del follaje sano, y la distribución de hojas dañadas en el árbol mismo fueron claramente evidentes. Estos resultados sugieren que las técnicas de detección a distancia que se han utilizado con éxito para supervisar campos de cultivo convencionales, también pueden usarse fácilmente, con algunas modificaciones, en cultivos comerciales en invernadero

Factors Affecting the Spatial Distribution of Black Mangrove on the Dredged-Material or “Spoil” Islands in the Lower Laguna Madre of Texas

Research was conducted to evaluate the spatial distribution of black mangrove (Avicennia germinans) on the dredged-material or “spoil” islands of the Lower Laguna Madre of Texas. Aerial color-infrared (CIR) photographs revealed the presence of black mangrove stands on many of the islands located south of the Arroyo Colorado (a distributary of the Rio Grande which empties into the Laguna Madre), but failed to detect significant mangrove stands on islands located north of the Arroyo. Analysis of CIR photographs and supervised image classifications for individual islands suggested a concentration of black mangrove along western shorelines and relatively low interior areas of islands, although relatively small and localized mangrove stands were clearly evident along eastern shorelines at several locations. These observations were consistent with ground surveys which indicated significantly higher mangrove densities along western vs eastern shorelines of selected islands (0.6 and 0.1 plants/m2, respectively; P \u3c 0.05), but no difference between ratios of small to large plants in stands located along western vs eastern shorelines (1.6 and 1.4, respectively; P\u3e0.05). The most plausible explanation for these trends is that wave action caused by prevailing southeasterly winds during most of the year may impede or prevent the establishment of black mangrove propagules (germinated „seeds‟) along eastern shorelines of islands which otherwise constitute suitable habitat for A. germinans. If this interpretation is correct, development of planting strategies designed to facilitate establishment of black mangrove stands along shorelines subject to turbulent wave action will be a requisite to the use of this important native plant species for erosion prevention and mitigation on spoil islands in the Lower Laguna Madre

International Liver Transplantation Society Global Census:First Look at Pediatric Liver Transplantation Activity Around the World

Background. Over 16 000 children under the age of 15 died worldwide in 2017 because of liver disease. Pediatric liver transplantation (PLT) is currently the standard of care for these patients. The aim of this study is to describe global PLT activity and identify variations between regions. Methods. A survey was conducted from May 2018 to August 2019 to determine the current state of PLT. Transplant centers were categorized into quintile categories according to the year they performed their first PLT. Countries were classified according to gross national income per capita. Results. One hundred eight programs from 38 countries were included (68% response rate). 10 619 PLTs were performed within the last 5 y. High-income countries performed 4992 (46.4%) PLT, followed by upper-middle- (4704 [44·3%]) and lower-middle (993 [9·4%])-income countries. The most frequently used type of grafts worldwide are living donor grafts. A higher proportion of lower-middle-income countries (68·7%) performed ≥25 living donor liver transplants over the last 5 y compared to high-income countries (36%; P = 0.019). A greater proportion of programs from high-income countries have performed ≥25 whole liver transplants (52.4% versus 6.2%; P = 0.001) and ≥25 split/reduced liver transplants (53.2% versus 6.2%; P &lt; 0.001) compared to lower-middle-income countries. Conclusions. This study represents, to our knowledge, the most geographically comprehensive report on PLT activity and a first step toward global collaboration and data sharing for the greater good of children with liver disease; it is imperative that these centers share the lead in PLT.</p