LUQ LTER DATA SETS DOCUMENTATION FORM

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DATA SET IDENTIFIER: Bisley rainfall and throughfall, and chemistry of rainfall and throughfall

PROJECT TITLE: Nutrient fluxes for rainfall and throughfall (in Bisley)

PROJECT DESCRIPTION:Several meteorological parameters are being measured at Bisley since 1993. Correlations between elevation and stream-runoff and rainfall, elevation and air and soil temperature, and between trhoughfall and vegetation types have been found. These relationships are used inhydrologic and nutrient budgets as well as in environmental models .

Rainfall and Stream-runoff

Long-term rainfall and discharge data from the Luquillo Experimental Forest (LEF) were analysed to develop relationships between rainfall, stream-runoff, and elevation. These relationships were then used with a Geographic Information System (GIS) to determine spatially-averaged, mean annual hydrologic budgets for watersheds and forest types within the study area. Model estimates indicate that a total of 3864 mm/yy (444 hm3) of rainfall falls on the forest in an average year. The Tabonuco, Colorado, Palm and Dwarf Forest types receive an estimated annual rainfall of 3537, 4191, 4167, and 4849 mm/yy, respectively. Of the average annual rainfall input, 65% (2526 mm/yr) is converted to runoff and the remainding 35% (1338 mm.yr) is lost from the system by evapotranspiration and other abstractions. In comparison to other tropical forests, the LEF as a whole has more evapotranspiration than many tropical montane forests but less evapotranspiration than many lowland tropical forests.

Throughfall

Changes in the quantity and quality of precipitation as it passes through vegetative cover are important components of both hydrologic and nutrient budgets.

Throughfall over any period depends on the balance between precipitation, evaporation and canopy storage (Horton, 1919; Leonard, 1967; Rutter et al., 1972). If the watershed is divided into different vegetation types based on similarity in throughfall and steamflow, the total throughfall over the watershed can be expressed as:

(1) Pg = Sum( T n A n )+ Sum (Sm Dm)

Where Pg = total throughfall reaching the ground, Tn = canopy throughfall from vegetation type n, An = area of vegetation type n, Sm = stemflow from stem type m and Dm = number of stems in type m.

Using eqn. (1) to estimate total watershed throughfall becomes a problem of determining the minimum number of vegetation types necessary to describe the system at the required level of accuracy. In one of our studies, measured throughfall was compared with actual canopy and stem conditions to estimate the percentages of throughfall for different time periods was calculated by weighting the average throughfall and stemflow measured in representative areas of each vegetation type by the total area of that vegetation group.

Measurements reported here were made in two of the Bisley Research Watershed of the U.S. Forest Service. These adjacent watersheds drain 13.0 ha of highly dissected mountainous terrain that range in elevation from 265 to 455 m. Both watersheds are covered by Tabonuco type forests and were selectively logged at various times between 1860 and 1940 (Scatena, 1988).
The dominant tree in the watersheds in the Tabonuco ( Dacryodes excelsa ) which often comprises as much as 35% of the canopy ( Wadsworth, 1970). Structurally the forest has three dominant layers, a discontinuous emergent strata, a continuous upper stratum at 20 m, and an understory layer. Leaves are mesophyllous and often covered with epiphytic growth.

Air and Soil Temperature

The relationship between mean air temperature and elevation is a required parameter for some environmental models such as Zelig. Mean air and soil temperature measurements of 10 sites located along a windward elevation gradient from 153 to 1011 meters were used to develop relationships between mean air and soil temperature of and elevation. The regressions performed showed a linear relationship between both air and soil mean temperature and elevation. The equations:

(2) Mean Air Temperature (in C) = 26.4 -(0.00558 * elevation in meters) and

(3) Mean Soil Temperature (in C) = 25.6 - (0.00543 * elevation in meters)

best fit these relationships. The equation that best fits the mean soil temperature - elevation relationship includes all the stations. In contrast, the best equation for the mean air temperature - elevation relationship excluded both station located at Sabana.

LTER CORE AREAS: Annotate all that apply (See online list)

LEF LTER 1 RESEARCH TOPIC: (Annotate all that apply) (See online list)

We define a data file as a component of a data set. A data set can have only one data file or more. Basically, different data files have different data structures or format .
DATA SET FILES (SUBSETS):

Data File No.	Data File Identifier	On-Line Filename	Starting Date	Periodicity of sample	End Period
1	Bisley rainfall and nutrient fluxes	Rainfall_flux.txt	March 22, 1988	weekly	December 31, 2002
2	Bisley throughfall and nutrient fluxes	Throughfall_flux.txt	March 22, 1988	weekly	December 31, 2002
3	Bisley Rain and Throughfall weekly measurements	BisleywklyRain-Throughfall2008.txt	March 8, 1988	weekly	September 30, 2008
3	Bisley Rain Gauge weekly measurements	BisleyannualRainfall88-08.txt	1988	weekly	2008

RESEARCH LOCATION: Bisley watersheds and Bisley Tower, Luquillo Experimental Forest

INVESTIGATORS:

PRINCIPAL INVESTIGATORS	E-MAIL ADDRESS:
Frederick N. Scatena	fns@sas.upenn.edu

OTHER RESEARCHERS	E-MAIL ADDRESS:
Tamara Heartsill-Scalley	theartsill@fs.fed.us
Carlos Estrada-Ruiz	cestrada@fs.fed.us
William H. McDowell	wmcdowell@lternet.edu
Ariel E. Lugo	alugo@lternet.edu

CONTACT PERSONS	Phone Number (Include area code)	E-MAIL ADDRESS:
Tamara Heartsill-Scalley	787-766-5335	theartsill@fs.fed.us
Frederick N. Scatena	215-898-6907	fns@sas.upenn.edu

SOURCE OF FUNDING (SPONSOR): USFS, NSF-LTER

DATA SET ABSTRACT: 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.

DATA SET METHODS:
Rainfall and throughfall collection
The rainfall and throughfall measured in this study were collected and measured in the same manner for the duration of the study, and in accordance with our previous publications (Scatena, 1990; Schellekens et al., 1999; Holwerda, 2006).  Bulk rainfall and throughfall were collected weekly (i.e. every Tuesday morning) and occasionally before and after major storms.  Total rainfall was collected in a 25 m above canopy walk-up tower that is located on the divide between the two catchments and at an elevation of 361 m above sea level.  Throughfall was measured throughout the watershed using 20 to 35 randomly placed but fixed gauges that were placed across the ridges, hill-slopes, gaps, and stream channels of the watershed (Scatena, 1990).  The rainfall collector and each throughfall collector had identical 143 cm2 funnels.  As many as 35 collectors were operated at any given time for the time series presented here. During Hurricane Hugo in 1989, the canopy tower that held the climate station and rainfall collector was toppled, but most of the throughfall collectors remained intact.  Those that were destroyed were randomly re-located within 10 m of their original site and throughfall was collected without interruptions.  The meteorological tower was also replaced after a few months. 

Chemistry
During every collection, bulk rainfall and throughfall were collected for chemical analysis.  Water for the rainfall analysis was collected from the above-canopy rainfall collector.  The throughfall sample was a composite of water collected in eight collectors.  These eight throughfall collectors were selected at the beginning of the study because their mean throughfall volume and conductivity was similar to the mean of all the bottles and therefore considered representative of the site.  These collection bottles were cleaned or replaced on a weekly basis and contained filters to prevent frogs and litter from entering the bottles. 
Water samples were delivered to the laboratory on the same day they were collected.  Chemical analysis was conducted in the same manner as previous studies of the LEF (McDowell et al., 1990; McDowell and Asbury, 1994; McDowell, 1998).  Protocols and the original data are available on the Luquillo LTER web-page:

(http://luq.lternet.edu/data/lterdb20/metadata/lterdb20.htm). 

In the laboratory, pH and conductivity were measured following the procedures specified by NADP (1984) and McDowell et al., (1990).  Samples were filtered using pre-combusted glass fiber filters (Whatman GF/F).  Until 1997, samples were held refrigerated for analysis, with a sub-sample for ammonium analysis preserved by acidification with sulfuric acid (McDowell et al., 1990).  After 1997, samples were stored frozen until analysis for all constituents except silica, which was analyzed on a refrigerated subsample.   During the first nine years of the study, most samples were analyzed at the University of Puerto Rico.  After 1997, all samples were analyzed at the University of New Hampshire.  Silica (phospho-molybdate), phosphorus (ammonium molybdate), and ammonium (phenol-hypochlorite) were analyzed throughout the study period using spectrophotometric methods using a Technicon AA II or Lachat Quickchem.  Cations were analyzed with atomic absorption spectrophotometry from 1988-1994, and with ion chromatography from 1994 on.  Anions were measured with ion chromatography.  Dissolved organic carbon and nitrogen were measured using persulfate digestion (McDowell et al., 1987; Solorzano and Sharp, 1980) prior to 1997, and with high temperature Pt-catalyzed combustion after 1997 (Merriam et al., 1996).  Cross-lab comparisons and analysis of samples using the different techniques indicated that comparable results were obtained with different laboratories and methods (e.g. McDowell et al., 1990; Merriam et al., 1996).

Rainfall and throughfall fluxes (kg ha-1 day-1) were calculated from weekly concentration values (http://luq.lternet.edu/data/lterdb26/metadata/lterdb26.htm) multiplied by the corresponding amount of weekly rainfall or throughfall.

REFERENCES:

CROSS-REFERENCES (other data sets related to this one): LTERDBAS #20: Chemistry of rainfall, throughfall, and stream water from El Verde and Bisley Verde and Bisley stations( data file 12); LTERDBAS 29: Bisley daily rainfall (Bisley weekly environmental data); LTERDBAS 90: Bisley Tower I Meteorological data (Bisley Tower); LTERDBAS148: Bisley rainfall and throughfall, and chemistry of rainfall and throughfall;

SAMPLE LOCATION:

STORAGE SITES(of data files):

INVESTIGATOR'S ASSIGNED KEYWORDS: flux chemistry, rainfall and throughfall

LEF LTER OFFICIAL KEYWORDS (See table): BISLEY TOWERS, BISLEY WATERSHEDS, HEADWATER STREAM, TABONUCO, CATIONS AND ANIONS, ENVIRONMENTAL VARIABLES

PUBLICATIONS:

Heartsill-Scalley, T., Scatena, F.N., Estrada, C., McDowell, W.H. and Lugo, A.E. (2007) Disturbance and long-term patterns of rainfall and throughfall nutrient fluxes in a subtropical wet forest in Puerto Rico. Journal of Hydrology 333, 472-485.

RESTRICTED ___ UNRESTRICTED _X__

REASONS TO RESTRICT DATA IN THIS DATA SET BEYOND ITS TWO YEAR POLICY PERIOD*:

*WILL HAVE TO BE APPROVED BY AT LEAST ONE LUQ LTER PRINCIPAL INVESTIGATORS: N. Brokaw, J. ZIMMERMAN, A. LUGO

FILING

_X__ "File" copy only:Data Management will only file an electronic copy of the data file and its documentation 
___ " Enter" data on-line:Data Management will be in charge of entering the data on computer files (Contact Eda C. Meléndez)

SITES DESCRIPTIONS: A complete description of the Bisley watersheds can be found in: Scatena, F. N., 1989. An introduction to the physiography and history of the Bisley Experimental Watersheds in the Luquillo Mountains of Puerto Rico. New Orleans, Louisiana, USDA Forest Service, Southern Forest Experiment Station.

Geographical positional system (GPS) Coordinates for each location:

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COMPUTATIONAL METHODS:

FOR DATA MANAGER USE ONLY

DATE OF LAST REVIEW: November 16, 2011

DATE OF LAST ENTRY: 2002

STAGE OF DATA SET MANAGEMENT (dates):
RECEIVED: May 08, 2006
ENTERED: May 08, 2006
FILED ON-LINE: October 10, 2007
REVIEWED BY RESEARCHER:

FILING MEDIA
NAME OF DOCUMENTATION FILE: lterdb148.htm
NAME OF ON - LINE CATALOG: LTERDBAS
RECORD #: 148
DOCUMENT TYPE: binary only
PRIORITY TO BE ENTERED: N/A