Luquillo Data Sets By Insertion Order

Transects 60 m long are conducted at alternate points in the 9 ha grid at El Verde. Transects 80 m long are conducted at alternate points at the Bisley Grid in watersheds #1 and #2. Data are used to support the GIS database.

The population distribution research area of the LEF LTER is designed to gather information on the distribution and abundance of key plant and animal species within the forest under different disturbance regimes. Multiple mark and resight studies were conducted to determine the population density of Anolis stratulus at one undisturbed forest site and one site in a partially regenerated treefall gap. Tower surveys were conducted in order to access individuals in the forest canopy.

Transects are conducted to note the vertical distribution and relative abundance of anole species. Data permit the calculation of average sighting distance for each species which is used in the final calculation of abundance.

Circular plot counts are used to measure relative numbers of birds over time and between sites. The duration of each count is 10 minutes. During this period, all birds heard or seen are recorded on a data sheet in one of two categories: 1) within 25 m of the observer (< 25 m) and 2) further than 25m from the observer (> 25 m). Records are further broken down into birds only heard (H on the data sheet) and birds observed (recorded as estimated distance from the sampling point in meters; see sample data sheet). Counts are begun as soon after dawn as possible and conclude before noon. Census points are at least 60 m apart within the grids. A complete list of the grid points where counts are taken is found in the data. Originally counts were conducted three times a year.

Relationships between landforms, soil nutrients, forest structure, and the relative importance of different disturbances were quantified in two subtropical wet steepland watersheds in Pueno Rico. Ridges had fewer landslides and treefall gaps, more above-ground biomass, older aged stands, and greater species richness than other landscape positions. Ridge soils had relatively low quantities of exchangeable bases but high soil organic matter, acidity and exchangeable iron. Valley sites had higher frequencies of disturbance, less biomass, younger aged stands, lower species richness and soils with more exchangeable bases. Soil N, P, and K were distributed relatively independently of geomorphic setting, but were significantly related to the composition and age of vegetation. On a watershed basis, hurricanes were the dominant natural disturbance in the turnover of individuals, biomass, and forest canopy. However. turnover by the mortality of individuals that die without creating canopy openings was faster than the turnover by any natural disturbance. Only in riparian areas was forest turnover by treefall gaps faster than turnover by hurricanes. The same downslope mass transfer that links soil forming processes across the landscape also influences the distribution of landslides, treefall gaps, and the structure and composition of the forest. One consequence of these interactions is that the greatest aboveground biomass occurs on ridges where the soil nutrient pools are the smallest. Geomorphic stability, edaphic conditions, and biotic adaptations apparently override the importance of spatial variations in soil nutrients in the accumulation of above-ground biomass at this site.

The data set consists of one file containing data from the summers of 1994 and 1999. Various habitat characteristics are presented, as well as the apparency of common plant taxa at 7 heights (every 0.5 m from ground level to 3 m). However, the data for some plant species were not divided by height in 1994; only total apparency of those species is available for that year.

Rainfall and throughfall are collected weekly at the Bisley LEF site. These data sets begin March 1988 and ends December 2003.

Rain and throughfall samples are the total catch for the week, and are exposed to field conditions for that time. No event sampling is conducted on a routine basis. Rainfall Collected in Bisley (RCB) are bulk or always-open collectors that receive dry deposition by sedimentation.

All samples are measured for pH and conductivity, and then filtered (pre-combusted Whatman GF/F glass fiber filter) prior to further analysis. From 1983-1994 samples were cooled and returned to the San Juan chemistry laboratory for analysis. During those years, samples for NH4 and NO3 analyses were refrigerated continuously until analysis. Sub samples for NH4 analysis were also preserved with 1 molar HCl. From 1994 on, samples for NH4 and NO3 were frozen until analysis, were not acidified, and all analyses were conducted at the University of New Hampshire.

Nutrient fluxes in rainfall and throughfall were measured weekly in a mature subtropical wet forest in NE Puerto Rico over a 15-year period that included the effects of five hurricanes and several prolonged droughts. Annual inputs of K, Ca, Mg, Cl, Na, and SO4-S are similar to those reported from other marine-influenced tropical forests. Rainfall input of nitrogen is comparatively low and reflects the relative isolation of the air shed. Mean annual rainfall and throughfall were 3482 and 2131 mm yr-1 respectively. On average, rainfall, throughfall, rainfall pH, and rainfall flux NH4-N and NO3-N had small but significant decreases throughout the study period. More nutrients fluxes had seasonal differences in rainfall (6 out of 12) than throughfall (4 out of 12). All volume weighted enrichment ratios calculated for the 15-year period were greater than one. However, median weekly enrichment ratios were less than 1 for sea salts and dissolved organic carbon and between 1 and 2 for Mg, Ca, SiO2 and SO4-S. In contrast, median weekly enrichment ratios were greater than 10 for NH4-N, PO4-P, and K and reflect biological enrichment within the canopy. Droughts reduced enrichment ratios of cations and sea-salts, but increased enrichment ratios for NH4-N, PO4-P and K. In the weeks following hurricanes relative throughfall tends to be higher and enrichment ratios tend to be lower. These long-term observations indicate that physical and biological processes associated with water passing through the canopy act to buffer internal nutrient cycles from inter-annual, and seasonal variations in rainfall inputs.

The LTER is conducting annual monitoring of Algae, Chlorophyll a, benthic organic matter, and benthic inorganic matter in order to document baseline stream characteristics. These data may be used to examine effects of disturbances such as hurricanes on stream ecosystems.

Collection details of bromeliads collected for invertebrate community and diversity analysis from 4 localities in the LEF. Dates, location, plant size, amounts, pH and temp. of contained water, and weights of debris retained by the bromeliads.