Using native species in mixed plots for neotropical timber plantations: quantifying tree growth rates & associated diversity Samantha J. Montgomery 1, Kelsey N. Williams 1, Stephanie H. Tran 1, Christie Hubbard 1, & Nicole Kreuzman 1 with Paul F. Foster 2, and Dr. Cris G. Hochwender 1 1 University of Evansville 2 Reserva Ecológica Bijagual This study measured growth rates of native trees in mixed tree plantations and quantified the diversity of understory plants to promote the use of native species. Native tree species help support a diverse understory which in turn promotes a megadiverse community. Conversion of old growth forests into tree plantations has led to a loss of biodivesity; plantations are typically composed of monocultures with non-native trees that reduce forest heterogeneity. Mixed native tree plantations has been proposed as an alternative. However, there is a lack of research on growth characteristics of native tree species. Study site and species—Reserva Ecológica Bijagual (REBS) is a private reserve located in the Sarapiquí River watershed of the Atlantic plain in Costa Rica. Seven native tree species were planted in three plots (C1, C2, C3) and six species were planted in another three plots (R1, R2, R3). Experimental Design—Survival, height, and diameter at breast height (DBH) were monitored for trees from the six plots in the abandoned pastures (Figure 1). Transects were run in plots in the C and R sites (10 transects total) to examine understory diversity. Individuals ≥1.0m tall were identified, and DBH was measured at 1.3m where possible. All vines and lianas at 1.0m high were identified. Twelve 0.25m quadrats were created in each transect, and every individual plant in each quadrat was identified to species (Figure 2). Analyses—Margalef’s index of species richness and the Shannon-Weiner diversity index were calculated using transect data to describe associated diversity and growth rates were calculated for each tree species. ACKNOWLEDGEMENTS We thank the following people and classes for their assistance with experimental design and data collection in the plots: Dr. Marie Ann de la Fuente, Orlando Vargas, Erica Ballard, Diana Durrance. We thank Dr. Susan G. Letcher and Orlando Vargas for their assistance in plant identification. CGH was funded through a Global Scholar award through the Institute for Global Enterprise in Indiana. The mixed native tree species plots included relatively large trees of high timber quality, and an exceptionally diverse understory that was established in a short period of time. Understory diversity is vital for ecosystem services, with re- vegetation improving structural complexity.This study demonstrated that using a mixture of native tree species in a plantation setting can provide high timber production and rapidly re-establish understory diversity.  Cordia bicolor and Terminalia amazonia (native species) showed rapid growth in mixed plots; each had a mean DBH greater than 20cm after 13 years of growth (Figure 3).  126 species were identified in the 30m 2 area associated with the 120 quadrats.  81 species were found across all transects, and of those 81 species, 65 co-occurred in quadrats.  Across the 120 quadrats (0.25m 2 each) and ten transects (30m 2 each), 142 species from 57 families colonized the understory of the plantations.  Mean number of species occurring in each quadrat was 4.8±0.2 (±SE).  Mean richness was 4.2 ± 0.1 (Margalef’s index) and mean diversity was 2.4 ± 0.4 (Shannon-Wiener index) across all ten transects. B A OBJECTIVE INTRODUCTION METHODS RESULTS Figure 1- Measuring the diameter at breast height (DBH) in the C and R sites. Figure 2 – Identifying individual species in each quadrant. Figure 3—Changes in mean diameter at breast height (DBH) for tree species at the two sites are depicted across time. (A) C site; (B) R site. CONCLUSION