Luquillo Data Sets By Insertion Order

The canopy trimming experiment at El Verde simulates some aspects (canopy openness and biomass redistribution) of hurricane disturbances. Soil samples and leaf litter were gathered from three replicate blocks, each with four treatment plots in Tabonuco Forest at in El Verde. Treatments (canopy trimming and debris addition) were applied in a 2 x 2 factorial design. Samples were obtained both before and after the canopy were trimmed and debris was applied in the appropriate treatments. Samples were collected every four months before and after treatments were applied. Molecular approaches such as EL-FAME are useful indicators of microbial community shifts in response to environmental change. In this experiment we analyzed microbial community composition and abundance in soil and leaf litter samples as reflected by EL-FAME profiles. All soil samples were cleaned by removing rocks and roots, and leaf litter samples were ground.

Fatty acid nomenclature: Fatty acids are named according to the conversion X:YωZ, where X represents the number of carbon atoms in the chain, followed by Y after the colon which represents the degree of the unsaturation. The symbol ω and Z represent the number of double bonds nearest to the carboxyl end. The prefixes a, i, cy and d refer to anteiso, iso, cyclopropyl branching and dicarboxylic fatty acid respectively; br indicates that the type of branching is unknown, while a number followed by Me indicates position of methyl group. Prefixes a and b indicate that the OH groups of an OH fatty acid are located at positions 2 and 3 respectively. Numbers preceded by w indicate the position of OH groups from the aliphatic end of the fatty acids (Kaur et al 2005).

Community analysis based on fatty acids: Fatty acid biomarkers could represent a group of particular microorganisms present in soil and leaf litter. Fatty acids used in literature as biomarkers are: Branched chain fatty acids (br 17:0, br 18:0, i17:0, a17:0, i16:0, i16:1, 10Me16:0, 10Me17:0), iso and anteiso isomers of 15:0 for gram positive bacteria; Cyclopropane fatty acids (cy17:0, cy19:0, 16:1w9, 16:1w7c, 16:1w5, 18:1w7,19:1) for gram-negative bacteria; 18:2w6 for fungi; 10Me16:0, 10Me17 : 0 and 10Me18 : 0 for Actinomycetes; cy17:0 and 10Me16:0 for Sulphate reducing bacteria; 16:1w8, 18:1w8 for Methanogens (Modified from Zelles, 1999; Kaur et al 2005).

We measured litterfall from 12 sites along an upper elevation gradient every two weeks from 1994 to present. Samples are being used to estimate the litterfall productivity over time and space, identify the impacts of periodic events, and help us understand the drivers of ecosystem and biogeochemical processes with climate and vegetation change.

Soil solution chemistry.

Chapter 1 (fish community data): Historical data are often one of the only resources for documenting and assessing causes of environmental change, particularly in developing regions where funding for ecological studies is limited. In this study, previously unpublished data from a 1977 year-long study of the fish community of the Espiritu Santo estuary are presented. This dataset is among the oldest and most extensive surveys of a Caribbean island estuarine fish community. A comparison of these historical data with data collected in June and July 2004 using identical sampling methods allowed description of potential long-term changes in the fish community, identification of vulnerable species, and assessment of potential drivers of change. Results strongly suggest a decline in species richness and abundance in the Espiritu Santo estuarine fish community, with greater declines in freshwater-tolerant than marine or euryhaline species. Declines in freshwater inflow to the estuary, due to large-scale upstream water abstractions for municipal use, have increased since the initial 1977 survey. This is the first study to examine long-term change in the fish community of a tropical island estuary. Additional research and conservation efforts are needed to understand mechanisms of change and to protect Caribbean island estuarine fish communities.

Chapter 2 (isotope and gut content data): The contribution of riverine-derived organisms and organic matter to four fishes along the salinity gradient in two Puerto Rican estuaries, the Espiritu Santo and Mameyes, was examined via stable isotope and gut content analyses. Stable isotope analyses indicated that riverine organic matter potentially contributed as much as 69% of the diet of one (caitipa mojarra, Diapterus rhombeus) of four fishes sampled. In contrast, riverine organic matter was of little direct importance to the three other fishes, tarpon snook (Centropomus pectinatus), ground croaker (Bairdiella ronchus), and white mullet (Mugil curema) contributing less than a third of their assimilated material even in the estuaries’ upper reaches. Gut content analysis of estuarine fishes demonstrated that several species of pelagic or omnivorous fish consume riverine-derived organisms, specifically juvenile migratory freshwater shrimps, during their residence in the estuary. Freshwater shrimps were frequently encountered (in 37 and 39% of guts examined) and composed an average of 18 and 22% of gut content material of omnivorous fishes sampled in the Espiritu Santo and Mameyes estuaries, respectively. To our knowledge, this is the first study to examine the contribution of riverine subsidies to a Caribbean island estuary. Given increasing demand for water resources on tropical islands and the importance of diadromy in these systems, there is a need for additional research on this topic to better inform water management decisions.

This data set comprises a single data file, which contains data on the abundance and distribution of the whipspider Phrynus longipes on the Luquillo Forest Dynamics Plot in July 2001.

In order to better understand how flooding and gap formation affect Amazonian rainforests, I set up plots both in three major forest types that differed by flooding duration (referred to here as dry, wet, very wet) and in their respective gaps.

Rain, throughfall, and stream water are collected weekly at the LEF sites listed below. These data sets begin as early as 1983; LTER sampling began in 1988.

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. Rain samples from WDEV are wet only from an automatically-closing collector that prevents any dry deposition (Aerochem Metrics NADP collector). RCEV and 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. Subsamples for NH4 analysis were also preserved with 1 molar H2SO4. 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.

Rain and Throughfall Sampling Sites
Descriptions of LTER LUQ rain and throughfall weekly sample chemistry data from 1988 onwards. Chemical concentrations are recorded as mg/L or mg/L as appropriate. Values below detection limits are recorded as 1/2 the detection limit.

This study was part of the Lotic Intersite Nitrogen eXperiment (LINX); a series of identical 15NH4 tracer additions to streams throughout North America. 15NH4Cl was added at tracer levels to a Puerto Rican stream for 42 days. Samples were collected from selected food web and dissolved nitrogen compartments throughout the addition and for several weeks afterwards to determine the uptake, retention and transformation pathways of nitrogen in the stream.