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 < 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>0.05). 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.
Yeager, V., Summy, K. R., Judd, F. W., Lonard, R. I., Mazariegos, R., Everitt, J. H., Heep, M. R., & Whelan, T. (2010). Factors Affecting the Spatial Distribution of Black Mangrove on the Dredged-Material or “Spoil” Islands in the Lower Laguna Madre of Texas. Subtropical Plant Science, 62, 44–55.
Subtropical Plant Science