Nick Brokaw	Nbrokaw@lternet.edu
Alejandra Riaño	Alejandrarg00@hotmail.com
Eda C. Meléndez-Colom	emelendez@lternet.edu

DATA SET IDENTIFIER:Canopy gap survey at El Verde

PROJECT TITLE:Canopy Structure

PROJECT DESCRIPTION: There are two main goals in this project. One one-time goal was to measure the dimensions of gaps present at El Verde research area, and the other continuing goal is to record changes in three dimensional canopy structure in three one- hectare sized plots, one each in tabonuco, colorado, and cloud forests.

The survey of gaps at El Verde covered about 35 ha, including the 9 ha grid.We defined a treefall gap at El Verde as a hole in the forest canopy extending down to an average height of about 3 m or less above ground. The edge of a gap was delineated by the vertical projection of the edge of the canopy foliage. We measured the dimensions of all gaps present in the 35-ha study site in August 1989, one month before Hurricane Hugo. For each gap we measured L, the longest axis of the gap (distance between edges), and W, the longest axis perpendicular to L, and then approximated gap area as that of an ellipse: Area = p LW/4 (Runkle 1992). Only openings 20 m2; were counted as gaps.  

The presence or absence of vegetation in height intervals above ground at points in the plots is recorded approximately every two years. We can then construct a three dimensional map of canopy surface and two- dimensional diagrams of vegetation cover along the vertical profile. The study began in 1989, before Hurricane Hugo, and continues, showing the changes caused by hurricane damage and recovery.

LTER CORE AREAS: (Annotate all that apply)

Disturbance

Primary productivity

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

Disturbance regime

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	Canopy gap survey at El Verde	Gapsurve.txt	November 1988	once	November 1988

RESEARCH LOCATION: El Verde Research Area

INVESTIGATORS:

PRINCIPAL INVESTIGATORS E-MAIL address

Nick Brokaw

Nbrokaw@lternet.edu

OTHER RESEARCHERS E-MAIL address

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

Nick Brokaw

Nbrokaw@lternet.edu

787 764-0000 ext. 4940

SOURCE OF FUNDING (SPONSOR): NSF

DATA SET ABSTRACT: The survey of gaps at El Verde covers about 35 ha, including the 9 ha grid.

We defined a treefall gap at El Verde as a hole in the forest canopy extending down to an average height of about 3 m or less above ground. The edge of a gap was delineated by the vertical projection of the edge of the canopy foliage. We measured the dimensions of all gaps present in the 35-ha study site in August 1989, one month before Hurricane Hugo. For each gap we measured L, the longest axis of the gap (distance between edges), and W, the longest axis perpendicular to L, and then approximated gap area as that of an ellipse: Area = p LW/4 (Runkle 1992). Only openings ³ 20 m2; were counted as gaps.  

DATA SET METHODS: Within this area, the canopy gap area of all recent gaps (sept. 1989) are marked with yellow flagging and have been roughly measured. Each gap has a unique identifying number. Canopy gap area is determined by measuring with a rangefinder, or  estimating, the lenght of the long and short axes of the hole in the canopy and using these figures to calculate the area of an ellipse as an approximation of the gap area.

Having this done, the rates of gap creation and size class distribution of gaps can be determined directly with a periodic census of new gaps in the area. Data on the mode of treefall, whether by uprooting or snapping off, of live trees or of snags were taken.

REFERENCES:
Brokaw, N. V. L. 1982. Treefalls: frequency, timing, and consequences. Pages 101-108 in E. G. Leigh, A. S. Rand, and D. M. Windsor (eds.). The Ecology of a Tropical Forest: Seasonal Rhythms and Long-term Changes. Smithsonian Institution Press, Washington, D.C.

CROSS-REFERENCES (other data sets related to this one): none

SAMPLE LOCATION: N/A

STORAGE SITES (of data files): stored with N. Brokaw and also LUQ-LTER Data Manager's File DM-001 , Drawer #1

INVESTIGATOR'S ASSIGNED KEYWORDS: canopy, Puerto Rico, Tabonuco forest, treefall gap

LEF LTER OFFICIAL KEYWORDS (See table): 9HA GRID, EL VERDE, TABONUCO, TREEFALL, TREES, PEER REVIEWED JOURNAL

PUBLICATIONS:
Brokaw, N., S. Fraver, J. S. Grear, J. Thompson, J. K. Zimmerman, R. B. Waide, E. M. E. III, S. P. Hubbell, R. Condit, and R. B. Foster. 2004. Disturbance and canopy structure in two tropical forests. Pages 177-194 in E. Losos and J. E. G. Leigh, editors. Tropical Forest Diversity and Dynamism: Results from a Long-Term Tropical Forest Network. The University of Chicago Press.

DISSEMINATION: UNRESTRICTED