Tropical Plant Reproduction Biology

Program Director: Dr. Joseph Wright

The goals of the plant component of the Environmental Sciencel Program are to monitor the reproductive phenologies and early regeneration of plants in tropical moist forests on Barro Colorado Island (BCI) and in the San Lorenzo Protected Area (SLPA) - in the area formally known as Fort Sherman (FTS), Panama (click on the maps for enlarged views).  The ESP includes eight plant censuses, with most censuses replicated at BCI and the SLPA.

Seed rain, seedling, and sapling censuses are conducted in a 50-ha forest dynamics plot located on BCI and in a 6-ha forest dynamics plot located in the SLPA.  The forest dynamics plots monitor all trees and shrubs larger than 1 cm in diameter at breast height (dbh), or 250,000 and 22,000 individuals at BCI and the SLPA, respectively.  The first six ESP censuses document seed inputs and seedling and sapling regeneration up to 1 cm dbh in the forest dynamics plots, providing data to complete the life cycles of several hundred tree and shrub species.  A seventh ESP census is a replicate seed rain study also located on BCI.

There have been a total of 690 plant species collected by the seed rain and seedling studies. Click here to see a list of these species including photos and phological information (where available).

We have a entensive library of digital images of reproductive parts and leaves from BCI, FTS and PNM. Click here to see them.



(click on the figures for enlarged views)

The three ESP seed rain studies are conducted at weekly intervals and include species-level identification of all flowers, seeds, and fruits of all plant life forms captured by 300 passive traps each with a surface area of 0.5 m2 (click on the figure to the right).  The weekly censuses provide an unusual degree of temporal resolution for analyses of the timing of flower production and fruit maturation.  The counts of seeds and fruits from a known area provide demographic data directly suitable for life history analyses.
Location of BCI seed traps within the 50-ha plot (click here for ASCII file)
The two ESP seedling and two sapling censuses are conducted at annual intervals and include species-level identification of all seedlings and tree and shrub saplings.  The seedling and sapling censuses provide annual estimates of recruitment, growth, and mortality.  The seedling census on BCI includes an annual assessment of light availability, which permits further evaluation of light dependence for all vital rates.  The close physical proximity of the seed rain and seedling censuses (click on the figure to the right) permits further evaluation of the seed-to-seedling transition for both BCI and the SLPA.
The final ESP plant census documents seed production and annual dbh growth increments for focal individuals of four tree species on BCI.  This census provides data to evaluate the degree of reproductive synchrony among individuals and the relationship between past reproduction, growth, and future reproduction.

Future Directions for ESP plant studies

The plant component of the ESP is being extended in three directions with funding from the NSF and the Andrew W. Mellon Foundation.  First, the Terrestrial Program seed rain and seedling censuses have been replicated in 50-ha forest dynamics plots located in the Pasoh Research Forest, Malaysia in 2001 and in the Yasuni National Park, Amazonian Ecuador in 2000 (2002 for seedlings).  The 50-ha forest dynamics plots at BCI, Pasoh, and Yasuni include 310, 827, and 1204 tree and shrub species, respectively.  The Amazonian seed rain study successfully identified more than 600 species of flowers, seeds, and fruits in its first year.  The Malaysian studies take place in a Dipterocarp forest where many hundreds of plant species only reproduce at multi-year intervals in general flowering events.  General flowering events occurred in 1983, 1987, 1992, and 1996 at Pasoh.  The Pasoh seed rain study was initiated in July 2001, a general flowering event began in August 2001, and incredibly a second general flowering event began in March 2002.  We have been blessed with remarkable good fortune.The seed rain and seedling censuses are being extended to include newly formed tree fall gaps at BCI only.  Seed rain and seedling census stations have previously been located randomly.  Since 99% of the forest understory is beneath a closed canopy at any moment, rare tree fall gaps have been poorly represented.  Funding from the Andrew W. Mellon Foundation has made it possible to add up to 100 new stations as new tree falls occur naturally within the BCI forest dynamics plot.  The new gap stations will increase the species included as seedlings by adding those light-demanding species that only recruit into tree falls and also provide vital rates in high-light, tree fall gaps for all seedling species.  Gap stations were added beginning in May 2002 and will be monitored indefinitely.The Terrestrial Program seedling censuses are also being extended by growing seedlings in common gardens in understory and tree fall microhabitats at BCI only with funding from the NSF.  These common garden experiments will provide weekly survivorship for the first year of seedling life, isolate seedling survival during the seed-to-seedling transition, provide vital rates for controlled understory and gap environments, and increase sample sizes for many rare species.  Common gardens were initiated in May 2002 and will be maintained for five years.

Personnel associated with ESP plant studies

S. Joseph Wright is the Principal Investigator for most ESP plant studies in Panama.  Kaoru Kitajima is co-Principal Investigator for common garden studies.

Osvaldo Calderón conducts the three seed rain censuses.
Andrés Hernandéz and Rufino Gonzalez conduct the two seedling and two sapling censuses.  Omar Hernandéz conducts the focal tree census.  Post-doctoral fellow, Roberto Cordero, oversees the common gardens.  Steven Paton manages all data bases.Nancy Garwood, Hugo Navarette, and S. Joseph Wright are co-Principal Investigators for seed rain and seedling studies in the Yasuni National Park, Ecuador.  Milton Zambrano conducts the seed rain censuses.  Viveca Persson and Margaret Metz helped to establish the studies as part of their doctoral studies.I-Fang Sun, S. Joseph Wright, Nur Supardi, and Stephen Hubbell are co-Principal Investigators for seed rain and seedling studies in the Pasoh Research Forest, Malaysia.  Mohammed Fausi bin Hassan and Mohammed Zulki Free bin Ehwan conduct the censuses.  Yu-yun Chen helped to establish the studies as part of her doctoral studies.