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DATA SET IDENTIFIER : Earthworms in tropical tree plantations and secondary forests

PROJECT TITLE : Earthworm Population Dynamics

PROJECT DESCRIPTION : Plant communities may impose strong control on soil fauna populations. We compared and examined patterns of earthworm abundance, species composition, and distribution pattern of earthworms in tree plantations and secondary forests of Puerto Rico. Our results indicate that variation in plant species composition and soil properties between plant communities can trigger differences in earthworm abundance and distribution pattern within a tropical wet forest.

LTER CORE AREAS: Annotate all that apply
 

Population Dynamics

Disturbance Patterns

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

Spatial and temporal distribution of population

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	Earthworm density and biomass raw data	earthraw.txt	January 1994	one time sample	May 1994
2	Earthworm species by forests	eart1tb2.txt	January 1994	one time sample	May 1994
3	Summary of density and biomass data	eart1tb1.txt	January 1994	one time sample	May 1994

RESEARCH LOCATION: within the subtropical wet forest life zone of the Luquillo Experimental Forest (LEF) of Puerto Rico (Ewel & Whitmore 1973)

INVESTIGATORS:

PRINCIPAL INVESTIGATORS E-MAIL address

Xiaoming Zou

xzou@www.ites.upr.edu

OTHER RESEARCHERS E-MAIL address

Grizelle Gonzalez	ggonzalez@fs.fed.us
Sonia Borges

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

SOURCE OF FUNDING (SPONSOR): NSF-LTER

DATA SET ABSTRACT: We compared patterns of earthworm abundance and species composition in tree plantations and secondary forests of Puerto Rico. Tree plantations included pine (Pinus caribaea Morelet) and mahogany (Swietenia macrophylla King) established in the 1930s, 1960s, and 1970s; secondary forests were naturally regenerated in areas adjacent to these plantations. We found that (1) earthworm density and fresh weight in the secondary forests were twice those in either of the tree plantations, and did not differ between the plantations, and (2) the exotic earthworm species, Pontoscolex corethrurus Mller, dominated both plantations and the secondary forests, but native earthworm species, Pontoscolex spiralis Borges & Moreno, Estherella montana Gates, and E. gatesi Borges & Moreno, occurred only in the secondary forests. Our results suggest that naturally-regenerated secondary forests are preferable to pine and mahogany plantations for maintaining a high level of earthworm density, fresh weight, and native species.

DATA SET METHODS: We used three plantations of each tree species (Pinus caribaea and Swietenia macrophylla) and their adjacent secondary forests, located between 200 m and 600 m elevation in the LEF. Each of the six pairs (plantations/secondary forests) have the same age, and similar topography, soil, and climate conditions. Two pine plantations were established in 1962 and one in 1977 with a 3 x 3 m tree spacing on the abandoned croplands near Cubuy and Guzman, respectively. These lands were cleared by bulldozers before planting pine seedlings. By 1989, the canopy of the pine plantation was mainly a monoculture, but Casearia sylvestris Sw., Didymopanax morototoni (Aubl.) Decne. & Planch., and Tabebuia heterophylla (DC.) Britton were among the native woody species presented in a well developed understory. The average litter production was 7.0 Mg/ha/yr. Two plantations of Swietenia macrophylla were established in 1932 near El Verde Field Station and one in 1963 near Sabana. Tree spacing ranged from irregular to 7.6 x 2.4 m (Lugo 1992). In 1984, the overstory of the plantations were dominated by mahogany, but Ocotea leucoxylon (Sw.) Mez., Tabebuia heterophylla, and Myrcia splendens (Sw.) DC. were also found in the understory. Average litter production was 10.8 Mg/ha/yr. Secondary forests were naturally regenerated adjacent to the pine and mahogany plantations on the same abandoned lands with similar soil conditions. By 1989, the secondary forests were dominated by Tabebuia heterophylla, Casearia arboria (L.C. Rich) Urban, Syzygium jambos (L.) Alston, and Manilkara bidentata (A. DC.) Chev. Average litter production was 6.15 Mg/ha/yr (Cuevas et al. 1991, Lugo 1992). All field data were obtained between January and May, 1994. Earthworms were sampled in two plots (0.5 x 0.5 m) randomly located in each plantation or its adjacent secondary forest for a total of 24 plots. Ground litter (leaves and twigs < 2 mm) was collected from each plot and litter biomass was obtained after drying leaves and twigs at 60 °C for at least 72 hrs. Leaves were analyzed for total extractable polyphenolics content using the Folin-Denis reagent (Horowitz 1970, Anderson & Ingram 1989) and were reported as percent tannic acid equivalent (% TAE). Soils beneath the litter were collected by shovel to a depth of 0.25 m and placed onto a cloth sheet. Earthworms were hand sorted and stored in plastic bags in a cooler with ice. Fresh weight of earthworms was recorded after the worms were rinsed with water and dried with paper towels on the same day when they were collected. A small subsample of the soil (0 - 0.25 m) was used for measuring pH and moisture content. Soil water content was calculated for each site by oven drying 10 g of fresh sample at 105 °C for 48 hrs and reported on the oven-dry basis. Soil pH was measured using a paste of 1:1 ratio of fresh soil and deionized water. Data was analyzed using ANOVA (SAS 1987) to compare differences among the plantations and the secondary forests. Where significant differences were found, Duncan's multiple range test was employed to compare differences among pine, mahogany and secondary forest. Earthworm density and fresh weight were correlated with soil pH, moisture content, ground litter biomass, and litter polyphenolics content using a simple linear correlation analysis (SAS, 1987).

 REFERENCES :

Anderson, J. M., & J. S. I. Ingram. (1989) Tropical Soil Biology and Fertility: A Handbook of Methods. C.A.B. International, Wallingford, UK.

Brown, S., L. Lugo, S. Silander, & L. Liegel. (1983) Research History and Opportunities in the Luquillo Experimental Forest. Gen. Tech. Rep. SO-44, USDA Forest Service, Washington DC, USA.

Ewel, J. J., & J. L. Whitmore. (1973) The Ecological Life Zones of Puerto Rico and the U.S. Virgin Islands. Res. Pap. ITF- 18, USDA Forest Service, Washington DC, USA.

Horowitz, W. (1970) Official methods of analysis of the association of official analytical chemists, p. 154. AOAC, Washington, D.C., USA.

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

SAS, Inc. (1987) SAS Guide for Personal Computers, 6th ed. Cary, North Carolina, USA.

Scatena, F. N., & M. C. Larsen. (1991) Physical aspects of hurricane Hugo in Puerto Rico. Biotropica 23, 317-323.

Soil Survey Staff. (1995) Order 1 Soil Survey of the Luquillo Long-Term Ecological Research Grid, Puerto Rico. USDA NRCS, Lincoln, NE, USA.

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. For. Ecol. Manage. 78, 147-157.

CROSS-REFERENCES (other data sets related to this one): LTERDBAS #92: Earthworms in abandoned tropical pastures

SAMPLE LOCATION : ITES, Data Manager's File DM-002 , Drawer #1

STORAGE SITES (of data files): N/A

KEYWORDS : Luquillo experimental forest, Pinus caribea, Pontoscolex corethrurus, Puerto Rico, restoration, Swietenia macrophylla

LEF LTER OFFICIAL KEYWORDS (See table): EL VERDE, SABANA, SUBTROPICAL, WET, SECOND FOREST, TERRESTRIAL, TREES, PEER REVIEWED JOURNAL

PUBLICATIONS :

González G., X. Zou, and S. Borges. 1996. Earthworm abundance and species composition in abandoned tropical croplands: comparison of tree plantations and secondary forests. Pedobiologia 40:385-391.

DISSEMINATION : UNRESTRICTED

SITES DESCRIPTIONS: This study was conducted within the subtropical wet forest life zone of the Luquillo Experimental Forest (LEF) of Puerto Rico (Ewel & Whitmore 1973). Dacryodes excelsa Vahl is a dominant tree species in a typical mature forest (Zou et al. 1995). Annual precipitation ranges from 2330 to 3920 mm, and the mean annual air temperature is 22.3 °C (Brown et al. 1983). The dominant soils are classified as very-fine, kaolinitic, isohyperthermic Typic Kandiudox, belonging to the Zarzal series (Soil Survey Staff 1995). Agricultural expansion during the late 19th century and the beginning of this century reached the lower portion of the LEF (Garcia-Montiel & Scatena 1994). Forest was cut and converted to coffee (Coffea arabica L.), banana (Musa spp.), or yautía (Xanthosoma spp.) plantations. However, a tropical storm in 1898 and two hurricanes in 1928 and in 1932 (Scatena & Larsen 1991) struck the Luquillo Mountains and destroyed most of these plantations, leading to their abandonment. In the 1930s, the US Forest Service began to annex these abandoned croplands adjacent to the forest. While allowing secondary succession to proceed under natural conditions in most of these disturbed areas, small tree plantations were established for experimental purposes.

Geographical positional system (GPS) Coordinates for each location:
 

location	latitude	longitude
pine plantation
mahogany plantation
secondary forests

 VARIABLES (ATTRIBUTES):

File Name or # above (all in which the variable appears)	1, 2, 3	1	1	2
Abbreviation (as it appears on the data file)	TREATMENT	FRESHWEIGHT(G-M2)	DENSITY1(NO-M2)	NATIVE_SPECIES
NAME OF VARIABLE	Forest type	Earthworm fresh weight	Number of earthworms per square meter	Scientific name of native species
DEFINITION OF VARIABLE	tree plantation type	Fresh weight of earthworms recorded after the worms were rinsed with water and dried with paper towels on the same day when they were sampled (in two plots (0.5 x 0.5 m) randomly located in each plantation or its adjacent secondary forest for a total of 24 plots)	Number of earthworms found per square meter	Scientific name of a native earthworm found in a forest type
UNIT		gramsPerSquareMeter	numberPerMeterSquared
PRECISION		.01
RANGE OR LIST OF VALUES	pine = Pinus caribaea, mahog = Swietenia macrophylla, secon = Secondary Forest			None = no native worm species fount in that plot, Estherella gatesi(Borges and Moreno 1989), Estherella montana(Gates 1970), Pontoscolex spiralis(Borges and Moreno 1990)
DATA TYPE	alphanumeric	decimal	integer	alphabetic
MISSING DATA CODES

 VARIABLES (ATTRIBUTES):

File Name or # above (all in which the variable appears)	2	3	3
Abbreviation (as it appears on the data file)	EXOTIC_SPECIES	DENSITYWEIGHT(NO-M2)	FRESH(G-M2)
NAME OF VARIABLE	Scientific name of exotic species	Number of earthworms per square meter	Earthworm fresh weight
DEFINITION OF VARIABLE	Scientific name of an exotic earthworm found in a forest type	Number of earthworms found per square meter. Mean + standard error; common letters within a column indicate no significant difference among treatments forest in Puerto Rico. Duncan's multi-range test, = 0.05); Total polyphenolyphenolics is given as % Tannic acid equivalent.	Fresh weight of earthworms recorded after the worms were rinsed with water and dried with paper towels on the same day when they were sampled (in two plots (0.5 x 0.5 m) randomly located in each plantation or its adjacent secondary forest for a total of 24 plots). Mean + standard error; common letters within a column indicate no significant difference among treatments forest in Puerto Rico. Duncan's multi-range test, = 0.05); Total polyphenolyphenolics is given as % Tannic acid equivalent.
UNIT		numberPerMeterSquared	gramsPerSquareMeter
PRECISION			.01
RANGE OR LIST OF VALUES	Amynthas rodericensis (Grube), Pontoscolex corethrurus (Muller)
DATA TYPE	alphabetic	alphanumeric	decimal
MISSING DATA CODES

COMPUTATIONAL METHODS:

VARIABLE NAME	FORMULA OR DESCRIPTION