Treesearch

The limestone region of Puerto Rico covers about 27.5 percent of the island’s surface and is subdivided into the northern, southern, and dispersed limestone areas. All limestone areas have karst features. The karst belt is that part of the northern limestone with the most spectacular surficial karst landforms. It covers 142,544 ha or 65 percent of the northern limestone. The karst belt is the focus of this publication, although reference is made to all limestone regions. The northern limestone contains Puerto Rico’s most extensive freshwater aquifer, largest continuous expanse of mature...

In many countries where the economy has shifted from mainly agricultural to industrial, abandoned agricultural lands are lost to urbanization. For more than 4 centuries the Puerto Rican economy depended almost entirely on agriculture, but sociopolitical changes early in the 20th century resulted in a shift to industry. This shift in the economy, and an increase in population, has resulted in an increase in urban areas. This study describes the rate and distribution of urban growth on the island of Puerto Rico from 1977 to 1994 and the resulting influence on potential agricultural lands....

Soil fauna can influence soil processes through interactions with the microbial community. Due to the complexity of the functional roles of fauna and their effects on microbes, little consensus has been reached on the extent to which soil fauna can regulate microbial activities. We quantified soil microbial biomass and maximum growth rates in control and fauna-excluded treatments in dry and wet tropical forests and north- and south-facing subalpine forests to test whether soil fauna effects on microbes are different in tropical and subalpine forests. Exclusion of fauna was established by...

To study the structure and composition of old-growth forest in the Saracá-Taquera National Forest near Porto Trombetas, Brazil, we established 36 0.25 ha plots and described the vegetation. We collected charcoal from the A2 soil horizon of each plot for radiocarbon dating. Although fires have been very rare in this forest during historic times, the presence of charcoal in these soils indicates fire at some earlier period. The ages (conventional radiocarbon age adjusted to 1997) of the charcoal ranged from 177 to 1547 years. These ages, however, did not correlate significantly with any of...

We experimentally excluded freshwater shrimp assemblages (Atyidae, Xiphocarididae, and Palaemonidae) to examine their effects on detrital processing and benthic insect biomass at three sites along an elevational gradient in a tropical stream in Puerto Rico. We also determined which shrimp taxon was responsible for leaf decay in a subsequent laboratory experiment. At the high-elevation site, the shrimp assemblage was dominated by Atya spp. and Xiphocaris elongata, and leaf decay rates were significantly faster in the presence of shrimps than in their absence. Laboratory experiments showed...

We studied soil moisture dynamics and nitrous oxide (N2O) ¯uxes from agricultural soils in the humid tropics of Costa Rica. Using a splitplot design on two soils (clay, loam) we compared two crop types (annual, perennial) each unfertilized and fertilized. Both soils are of andic origin. Their properties include relatively low bulk density and high organic matter content, water retention capacity, and hydraulic conductivity. The top 2±3 cm of the soils consists of distinct small aggregates (dia. ,0.5 cm). We measured a strong gradient of bulk density and moisture within the top 7 cm of the...

ser humano está transformando rápidamente el planeta Tierra (Meyer y Turner, 1994; Vitousek et al., 1997a). Su actividad tiene efectos globales que modifican el ambiente terrícola (Tabla I). Estos cambios, que comenzaron con la revolución industrial del siglo XIX, serán más notables en el siglo XXI en lo que se ha denominado la era Homogeocena donde el efecto dominante del ser humano sobre la biosfera será incuestionable (Putz, 1997).

A 50 % basal area reduction in Puerto Rico’s colorado forest had little immediate impact on diameter at breast height growth for most residual stems. A slight positive response was evident for several species after 5 to 30 yrs. Instead, thinning served as a major stimulus for a massive ingrowth of two common colorado forest tree species important to the Puerto Rican Parrot: palo colorado (Cyrilla racemiflora L.), the major parrot nesting tree, and cupeíllo (Clusia clusoides (Griseb.) D’Arcy), a main source of food. Canopy opening appeared beneficial for the survival and regeneration of...

The volatile components of whole-body extracts of males, females and workers were analyzed in four species of Neotropical ants in the formicine genus, Camponotus. The species, C. kaura, C. sexguttatus, C. ramulorum and C. planatus, represent three different subgenera. Volatile mandibular gland components were found only in male extracts in three of the species. In C. ramulorum, volatile components were found in male and female reproductives and workers. 3,4-Dihydro-3,5-dihydroxy-6-methylpyran-4-one and octanic acid were found in different sets of three of the species. Methyl 6-methyl...

Ecosystems were originally defined as units of the earth’s surface, that is the whole system including the organisms and the physical factors that form the environment (Tansley, 1935). As the study of ecosystem ecology evolved, ecosystems came to be categorized by their function and structure (Odum, 1953) with an emphasis on integration and indirect interaction (Muller, 1997). Ecosystem scientists divided into two camps: those concerned with measuring an ecosystem’s input and output relations (flows of matter and energy; Evans, 1956) and those concerned with specific populations (Levin,...