A DATA SET is a series of observations collected by the same methodology. Each data set should have documentation sufficient for someone unfamiliar with the research to replicate the study. Data sets may be broken into subsets (data files) that are discrete in space and time, in that order. The documentation for a data set should include all spatial and temporal subdivisions of the data.

(Data, Abstract, Methods, Variables)

NOTES:

• Add rows to tables or lines to paraghaphs as you need them for entering your data.
• Contact emelendez@lternet.edu, if you have any question.

PERSON(S) COMPLETING THIS FORM: E-MAIL ADDRESS:

DATA SET IDENTIFIER: Soil organic matter dynamics in the tabonuco forest, a plantation and a secondary forest in Guzman

PROJECT TITLE: Soil Organic Matter Dynamics in Tabonuco Forest (LTER-NASA-MRCE )

PROJECT DESCRIPTION: In this project we try to find out the relationship between the primary production and the soil organic carbon fractions in the tabonuco forest, a plantation and a secondary forest in Guzman.

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

Soil organic matter formation

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	annual litterfall, and forest floor litter	litter.txt	July 1996 to June 1997	monthly	June 1997
2	soil respiration	respire.txt	August 1996 to June 1997	bimonthly	June 1997
3	soil organic carbon in light fraction, microbial biomass, and soil properties	carbon.txt	January 1997	one time	June 1997

RESEARCH LOCATION: MRCE plots at El Verde (tabonuco forest); A pine plantation and a secondary forest at the "Guzman Plantation" at El Verde.

PRINCIPAL INVESTIGATORS E-MAIL address

OTHER RESEARCHERS E-MAIL address

Xiaoming Zou

xzou@lternet.edu

CONTACT PERSONS E-MAIL address Phone Number (Include area code)

Xiaoming Zou

xzou@lternet.edu

(787)764-0000. Ext. 2868

SOURCE OF FUNDING (SPONSOR): LTER-NASA

DATA SET ABSTRACT: In this project we try to find out the relationship between the primary production and the soil organic carbon fractions.

DATA SET METHODS: This study was conducted in the Luquillo Experimental Forest (LEF) in the subtropical life zone of northeastern Puerto Rico. The forest is dominated by tabonuco (Dacryodes excelsa). The site receives 3500 mm of rainfall each year with a monthly mean temperature of 22.1 °C (Brown et al. 1983). Soils of the area are a complex of upland Ultisols and Oxisols (Soil survey 1995). The general topography is mountainous with deeply dissected drainage at elevations between 340 m and 460 m above sea level.

The experimental treatments were initiated in November of 1989 two months shortly after hurricane Hugo passed over the LEF (Zimmerman et al. 1995). The hurricane defoliated the forest and generated plant debris that was equal to the total amount of annual litterfall in the forest (Lodge et al. 1991). The experimental design had four blocks, and each block had three treatments: one time removal of hurricane-generated debris, fertilization, and control.

Fertilization was conducted by a quarterly addition of nutrients to the plots at an annual rate of 300 kg-N/ha, 100 kg-P/ha, 100 kg-K/ha, 8 kg-B/ha, 15.4 kg-Cu/ha, 2.2 kg-Fe/ha, 25 kg-Mn/ha, 26 kg-Zn/ha, and 19 kg-Mg/ha. The plot for each treatment was 20 m 20 m in size with an interior 10 m x 10 m area for measurement. All blocks were located within the tabonuco forest zone, although there were differences both within and among blocks in tree species composition, tree density and stem basal area (Parrotta and Lodge, 1991).

Five baskets ( 0.50 m2 in surface area, 0.65 m above ground) were placed in each plot of the three treatments (debris removal, fertilization and control) in each block. The litterfall was collected every two weeks from July 14, 1996 to June 30, 1997. The collected materials were separated into leaves, wood and miscellaneous materials and then oven dried at 50 0C for one week before they were weighed. Forest floor litter was collected every two months from July 1996 to May 31, 1997 from a random area of 0.5 m x 0.5 m in each plot, divided into leaf, wood and miscellaneous materials and weighed after being oven-dried for one week (50 0C).

Litter samples were ground with a Wiley mill to pass through a 0.85 mm mesh sieve. Soil organic carbon was determined with the Walkley-Black method (Nelson and Sonmers 1982). Nitrogen was analyzed with a Kjedahl digestion method (Bremner and Mulvaney 1982). Extractions for soil exchangeable K, P, Mn and Fe was done using a modified Olsen s method (Hunter, 1982). Calcium, Mg, Na and Al were extracted with 1 N KCl. All extractions were analyzed by a Beckman plasma emission spectrometer.

Soil respiration was measured using NaOH in field chambers (Carter, 1993). Six cylinder chambers (102.5 cm2 in opening area and 20 cm in height) were placed in each plot. Three of them included ground plant litter and three had no litter. A plastic bottle with an opening area of 10.75 cm2 containing 15 ml of 1 M NaOH was placed inside each chamber for 24 hr and then brought to the laboratory for titration using 1 M HCl to determine the amount of CO₂ which was absorbed in the NaOH solution during the incubation. Microbial biomass was measured using a

fumigation-incubation procedure (Jenkinson and Powlson 1975) in August 1996 and March 1997, representing a wet and dry season, respectively. A soil sample from seven cores (3.75 cm in diameter) from each plot was collected to a depth of 10 cm and weighed for soil bulk density determination. Approximately 15 to 20 g was oven-dried at 1050 C for three days for determining soil water content. Two sets of soil samples were prepared: one as a control and the other for fumigation treatment. Each sample contained 30 g of soil that was placed into a 100 ml beaker. For the fumigation treatment, beakers were placed into a clean glass vacuum desiccator that was lined with moistened filter paper. A beaker containing 40 ml of alcohol-free chloroform was placed into the desiccator which was then evacuated for 2-3 min. During the evacuation period, the chloroform was boiled vigorously until the atmosphere in the desiccator was near saturation. Samples were left in the desiccator for 18-24 hr. The fumigated samples were vaccumed for 3 times to extract the remaining chloroform in soil. Each sample was inoculated with 1.0 g well mixed inoculum and then placed into wide month glass jars of 2-L volume. A beaker containing 20 ml 1 M NaOH was placed into each jar. The jars were closed using lids with rubber septa and incubated for 10 days at 25 0C. The quantity of NaOH remaining in each beaker was titrated with 1 M HCL with phenolphthalein as an indicator. The same soil sample was incubated with another 20 ml 1 M NaOH for another 10 days and the remaining NaOH was titrated with HCl at the end of the incubation.

Nitrogen and carbon in the light fraction was determined using a density isolation method (Sollins et al., 1984). Air- dried soil was passed through a 2 mm mesh sieve and then 1 g of the soil was suspended in 20 ml of soidium iodide (NaI) solution adjusted gravimetrically to 1.85 g/ml density. The suspension was sonicated for 15 min, vacuumed (70 kPa) for 10 min, and then left to for 24 hrs at room temperature to separate light and heavy fractions. The light fraction at the surface of the high- density liquid was aspirated and trapped onto a filter paper (GF/A), rinsed with deionized water, and then analyzed for C and N with a Perkin-Elmer CHN analyzer.

Soil respiration rate was calculated using the following formula (Carter 1993): Milligrams of C or CO₂ = (B - V) NE, where B = volume (milliliters) of acid needed to titrate the NaOH in the beakers from the control sample, V = volume (milliliters) of acid needed to titrate the NaOH in the beakers from the CO₂ enriched samples, N = normality of the acid, and E = equivalent weight. To express the data in terms of carbon, E = 6; to express it as CO₂, E = 22.
Microbial biomass was calculated using the formula: B = V_f -V_c; G = B/100*S*0.0004955 g C/cm³; M = G*H*D/W where B = CO₂ flush (as % by volume), V_f = CO₂ flush of 10 day fumigated soil, V_c = CO₂ flush of 10 day control soil, G = Grams of CO₂-C flush, S = jar volume, M = soil biomass, H = soil bulk density, D = soil depth, and W = dry weight of soils. Statistical analysis of the data was conducted using Statistix software. I used the SAS to calculate the decay constant k (SAS 1985). Differences among the treatments were tested using Sheffe s multiple range test. The significance level was set at alpha= 0.05.

REFERENCES:
Brown, S. and A.E. Lugo. 1990. Tropical secondary forests. Journal of Tropical Ecology 6: 1- 32.

Brown, S. and A.E. Lugo. 1994. Rehabilitation of tropical lands: a key to sustaining development. Restoration Ecology 2: 97-111.

Brown, S., M. Lenart, J. Mo and G. Kong. 1995. Structure and organic matter dynamics of a human-impacted pine forest in a MAB reserve of subtropical China. Biotropica 27 (3): 276-289. Cambardella , C.A. and E.T. Elliott. 1992. Particulate soil organic matter changes across a grassland cultivation sequence. Soil Sci . Soc. Am. J. 56 (3) : 777-783.

Cuevas , E., S. Brown and A.E. Lugo . 1991. Above- and below-ground organic matter storage and production in tropical pine plantation and a paired broadleaf secondary forest. Plant and Soil 135: 257- 268.

Garcia-Montiel , D.C. 1996. Changes in nutrient cycling during tropical deforestation. A Ph.D. dissertation. Colorado State University, Fort Collins, CO.

Lugo, A.E. and S. Brown, S. and J. Chapman. 1988. An analytical review of production rates and stemwood biomass of tropical forest plantations. Forest Ecology and Management 23: 179-200.

Lugo , A.E. 1992. Comparison of tropical tree plantations with secondary forests of similar age. Ecological Monographs 62 (1): 1-41.

Mo, J., S. Brown, M. Lenart and G. Kong. 1995. Nutrient dynamics of a human-impacted pine forest in a MAB reserve of subtropical China. Biotropica 27 (3): 290-304.

Parrotta , J.A. and Lodge, D.J. 1991. Fine root dynamics in a subtropical wet forest following hurricane disturbance in Puerto Rico. Biotropica 23: 343-347.

Waide, R.B., J.K. Zimmerman and F.N. Scatena. 1998. Controls of primary productivity: lessons from the Luquillo mountains in Puerto Rico. Ecology 79 (1): 31-37.

Walker, L.R. 1991. Tree damage and recovery from Hurricane Hugo in Luquillo Experimental Forest, Puerto Rico. Biotropica 23: 379-385.

Walker, L.R. , J.K. Zimmerman, D.J. Lodge and S. Guzman - Grajales . 1995. An altitudinal comparison of growth and species composition in hurricane-damaged forests in Puerto Rico. Journal of Ecology 84: 877-889.

Zimmerman, J.K. , W.M. Pulliam , D.J. Lodge, V, Quinones - Orfila , N. Fetcher, S. Guzman - Grajales , J.A. Parrotta , C.E. Abury , L.R. Walker and R.B. Waide . 1995. Nitrogen immobilization by decomposing woody debris and the recovery of tropical wet forest from hurricane damage . Oikos 72: 314-322.

Zou , X., C.P. Zucca , R.B. Waide , W.H. McDowell . 1995. Long- term influence of deforestation on tree species composition and litter dynamics of a tropical rain forest in Puerto Rico. Forest Ecology and Management 78: 147-157.

CROSS-REFERENCES (other data sets related to this one):

SAMPLE LOCATION: soil and litter samples at the Institute for Tropical Ecosystem Studies (ITES) Soil Laboratory (second floor) in plastic bags.

STORAGE SITES (of data files): ITES' Data Management files DM-002, Drawer #1

INVESTIGATOR'S ASSIGNED KEYWORDS: soil organic carbon (soc) fractions, controls of soc, litterfall, microbiomass, soil respiration

LEF LTER OFFICIAL KEYWORDS (See table): MRCE, EL VERDE, TABONUCO, CARBON, SECOND FOREST, SOILS, LITTER FALL, PRIMARY PRODUCTION, RESPIRATION, TREES  (pines), THESIS

PUBLICATIONS:

DISSEMINATION: UNRESTRICTED

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

*WILL HAVE TO BE APPROVED BY LTER PRINCIPAL INVESTIGATORS: N. BROKAW, A. LUGO

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

SITE DESCRIPTION:
These studies were conducted in a pine plantation and a secondary forest at the Guzman sector of the Luquillo experimental forest within the subtropical wet forest zone in northeastern puerto rico (18º 18' n; 65º 50' w). The Mean annual rainfall at this site was 3920 mm (lugo, 1992). The tree plantation of Pinus caribeae was established on Abandoned croplands in 1976. The secondary forest, located 1 km away from the plantation on the same slop, is of similar age. The soils are classified as a clayey, mixed isothermic tropohumult. Both the plantation and the secondary forest are 0.25 ha in Size. Two experimental treatments were established in 1990 in both the plantation and the secondary forest: control and litter Exclusion. The litter exclusion plot was conducted by establishing a tent of 2.0 x 2.0 m2 in area and 1.7 m in height, using pvc Tubes and nylon netting with 1 mm opening mesh. Initial forest floor mass was removed from the exclusion plots.

Geographical positional system (GPS) Coordinates for each location:

location	latitude	longitude
MRCE plots at El Verde (tabonuco forest)
Pine plantation at the Guzman plantation, El Verde
Secondary forest at the Guzman plantation, El Verde

VARIABLES (ATTRIBUTES):

FILE NAME OR #ABOVE (all in which the variable appears)	1 (twice in file), 2, 3	1 (twice in file), 2, 3 (three times in file)	1	1
ABBREVIATION (as it appears on the data file)	Month	Location	leavesLitterfall_g-d-m2	miscLitterfall_g-d-m2
NAME OF VARIABLE	month (and year)	location	weight of leaves fall	Weight of miscelaneous material
DEFINITION OF VARIABLE	Month and year when the measurement was taken	location where the measurement was taken	weight of miscelaneous material in litterfall	Weight of miscelaneous material in litterfall
UNIT		N/A	g/day/m2	g/day/m2
PRECISION		N/A	± .01	± .01
RANGE OR LIST OF VALUES	July 1996 to June 1997	plantation = Guzman plantation; sco F (SF) = Guzman secondary forest; Secondary Forest plot Guzman Plot = Guzman secondary forest; MRCE C = MRCE control plot; MRCE F = MRCE fertilization plot; MRCE L = MRCE litter removal plot; MRCE PLOT	0 to 2	0 to 1
DATA TYPE	alphanumeric	alphabetic	real	Real
MISSING DATA CODES	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE

VARIABLES:

FILE NAME OR #ABOVE (all in which the variable appears)	1	1	2 (MRCE PLOTS)	2 (MRCE PLOTS)	2 (IN GUZMAN PLANTATION & SECONDARY FOREST)
ABBREVIATION (as it appears on the data file)	woodLitterfall_g-d-m2	TotForestFloorLitter_g-m2	control1, contro12, control3	control plot no litter	litter exc
NAME OF VARIABLE	weight of wood fall	forest floor litter total	carbon dioxide evolution in a control plot (1), in a fertilized plot (2), and in a litter removal plot (3)	carbon dioxide evolution in a chamber in control plot with no litter	carbon dioxide evolution in a litter exclusive treatment
DEFINITION OF VARIABLE	weight of woody material in litterfall	total weight of forest floor litter	total weight of carbon dioxide in the control plot with litter	total weight of carbon dioxide in the plot with no litter	total weight of carbon dioxide in the plot litter only
UNIT	g/day/m2	g/m2	g/m2.d	g/m2.d	g/m2.d
PRECISION	± .01	± .01	± .01	± .01	± .01
RANGE OR LIST OF VALUES		400 to 1400	1 to 4	1 to 3	1 to 2
DATA TYPE	real	real	real	real	Real
MISSING DATA CODES	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE

VARIABLES:

FILE NAME OR #ABOVE (all in which the variable appears)	2 (IN GUZMAN PLANTATION & SECONDARY FOREST)	2 (IN GUZMAN PLANTATION & SECONDARY FOREST)	2 (MRCE PLOTS)	3 (three times in file)
ABBREVIATION (as it appears on the data file)	root exc	L&R exc	ferti plot no litter, add litter1, litter remov no litter, add litter2	Treatment1, Treatment2, Treatment3
NAME OF VARIABLE	carbon dioxide evolution in a root exclusive treatment	carbon dioxide evolution in a litter and root exclusive treatment	fertilized and litter removal plots-with litter addition	treatment
DEFINITION OF VARIABLE	total weight of carbon dioxide in the plot with root only	total weight of carbon dioxide in the plot with root and litter only	total weight of carbon dioxide in the plot with litter addition	treatment regarding litter removal
UNIT	g/m2.d	g/m2.d	g/m2.d	N/A
PRECISION	± .01	± .01	± .01	N/A
RANGE OR LIST OF VALUES	1 to 2	1 to 2	1 to 3	litter no litter
DATA TYPE	real	real	real	alphabetical
MISSING DATA CODES	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE

VARIABLES:

FILE NAME OR #ABOVE (all in which the variable appears)	3	3	3	3
ABBREVIATION (as it appears on the data file)	MicrobialBiomassC_g-m2	soil pH	soil moisture_%	BulkDensity_G-cm3
NAME OF VARIABLE	microbial biomass carbon	soil pH	soil moisture(%)	Bulk density (G/cm3)
DEFINITION OF VARIABLE	microbial biomass carbon	pH of soil sample	percent of water in soil sample	weight of soil in 1-10 cm of soil sample
UNIT	g/m2.d	percentage	percentage	g/cm3
PRECISION	± .1	±  .01	N/A	± .01
RANGE OR LIST OF VALUES		3 to 6	50 to 70	.5 to .8
DATA TYPE	real	real	integer	real
MISSING DATA CODES	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE	NO BLANK SPACE

VARIABLES:

FILE NAME OR #ABOVE (all in which the variable appears)	3	3
ABBREVIATION (as it appears on the data file)	total C	C in LF
NAME OF VARIABLE	total Carbon in the soil	Carbon in Light Fraction (mg/G)
DEFINITION OF VARIABLE	percentage of organic Carbon in soil sample	weight of Carbon which is at the surface of the high density solution in one gram of soil sample
UNIT	percentage	mg/G
PRECISION	± .1	±  .01
RANGE OR LIST OF VALUES	2 to 9	0 to 4
DATA TYPE	real	real
MISSING DATA CODES	NO BLANK SPACE	NO BLANK SPACE

COMPUTATIONAL METHODS:

Variable Name	Formula

FOR DATA MANAGER USE ONLY

DATE OF LAST REVIEW: Jan 22, 2005
DATE OF LAST ENTRY: 8/24/1998
STAGE OF DATA SET MANAGEMENT (dates):
RECEIVED: 8/24/1998 
ENTERED: 8/24/1998 
FILED 8/24/1998
ON-LINE 10/08/2000
REVIEWED BY RESEARCHER 8/24/1998
FILING MEDIA: magnetic file (papr copy also)
NAME OF DOCUMENTATION FILE: lterdb98.fm1
NAME OF DATA FILE: (1)litter.wb2,(2)respire.wq1,and (3)carbon.wq1
NAME OF ON - LINE CATALOG: LTERDBAS   
RECORD #: 98
DOCUMENT TYPE: magnetic file
PRIORITY TO BE ENTERED: N/A

Rev. date of this form: 15 July 2001