Puerto Rican Forests Research Articles

Responses of Bird Populations in a Puerto Rican Forest to Hurricane Hugo: The First 18 Months

Bird populations in a subtropical wet forest were monitored every two to three weeks with mist nets and point counts beginning two weeks after the passage of Hurricane Hugo in September 1989. The results were compared with those of a pre-hurricane study in the same locations in which birds were sampled in forest understory and openings. Capture rates were initially higher than in the previous study, due to displaced canopy dwellers foraging in the understory. The shift ofcanopy dwellers may have obscured expected declines in nectarivores and fruit/seedeaters and contributed to increased detections of omnivores and insectivores. Bird captures and fruit production peaked 93-156 days after the storm in pre-existing gaps, where higher capture rates and a distinct assemblage of birds occurred in contrast to sites without fruit (forest understory and a powerline opening). Captures in pre-existing gaps decreased as fruit production ceased, and overall captures declined to baseline levels after 198 days. After one year of recovery, new gaps and forest understory became distinguishable on the basis of their unique foliage profiles. Although different bird assemblages had been found in forest understory and in gaps prior to the hurricane, these assemblages lost their distinctiveness after the storm. It may take many years after a hurricane for forest understory and gaps to become sufficiently distinct in structure and resources before birds differentiate between the two habitats.

A Visit to Arecibo Finds a Telescope Seeking Improvement

The cable car looks not on white slopes and prancing skiers but on the tropical green and brown of Puerto Rican forests. At the top terminus you can look straight down a distance equal to the height of the Washington monument. You look into the center of the world's largest dish—18 acres of wire mesh on a carefully positioned spherical network of supporting cables. You walk around on a 500‐ton assembly that supports two carriage houses, a workshop, cables, waveguides and motors to turn and slide its various parts. Below extend the horns, snouts and Yagi antennas that can transmit and receive radio frequencies between 20 and 600 megahertz. A few miles south of the northern coast of Puerto Rico, this is the radar and radio telescope of the Arecibo Ionospheric Observatory. It was dedicated in 1963 (PHYSICS TODAY, January 1964, page 66).

Effect and Persistence of Herbicides Applied to Soil in Puerto Rican Forests

Six herbicides were applied at 3, 9, and 27 lb/A to the soil in forests of three types in Puerto Rico. The forests differed in soil type, amount and pattern of rainfall, and species composition. Defoliation occurred slowly, but the correlation between percentage defoliation and plants killed was significant at the 1% level of probability. Some defoliation was evident 1 month after treatment and increased slowly during the next 6 to 8 months. The most effective herbicide was 4-amino-3,5,6-trichloropicolinic acid (picloram). Generally, 2-methoxy-3,6-dichlorobenzoic acid (dicamba), 2-methoxy-4,6-bis(isopropylamino)-s-triazine (prometone), and 5-bromo-3-sec-butyl-6-methyluracil (bromacil) were less effective than picloram. Both 2,3,6-trichlorophenylacetic acid (fenac) and 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron) were ineffective. Defoliation was greatest and more plants were killed in the driest site.One year after treatment, fenac was the most persistent herbicide in the soil. Herbicides were found to a 36 to 48-in depth within 3 months after application.Herbaceous and woody seedlings were present at all sites within 18 months after herbicide application. There was no definite relationship between herbicidal treatment and secondary succession, except that the number and frequency of successional species were greater on plots having the highest percentage of defoliation.