Caribbean forested wetlands-pterocarpus officinalis forests as models to understand wetlands in light of expected changes in sea level

Caribbean forested wetlands-pterocarpus officinalis forests as models to understand wetlands in light of expected changes in sea level Elsie Rivera Ocasio 1, Neftalí Rios López 1, Amadou Bâ 2 and Tamara Heartsill Scalley 3 1 University of Puerto Rico-Bayamón/Humacao, 2 Université Antilles-Guyane, 3 International Institute of Tropical Forestry-USDA Forest Service

Pterocarpus officinalis One of the main constituents of coastal freshwater-forested wetlands in the Caribbean basin. Provide unique and significant habitat for many plant and animal species; endemic & neotropical migrant birds. Prevent erosion along coastal margins & along river banks in both coastal and montane areas. Cultural resource for artisanal fishers Grassland Pterocarpus swamp forest Mangrove Figure 1. Distribution and relative size of P. officinalis, from grassland to mangrove along a salinity gradient in Guadeloupe (Saint-Etienne et al. 2006).

Pterocarpus stands cover large areas in Caribbean islands and can dominate the canopy, with 47% to 100% coverage depending on site salinity levels.

Pterocarpus officinalis Stands are structured by salinity and flooding in coastal areas and by flooding along rivers & seasonal variations in the water table in mountain areas

Pterocarpus officinalis Throughout the Caribbean, expansion of agricultural and urban areas has reduced its distribution to isolated patches. Current populations in coastal areas often occur near the extreme of their salinity tolerance.

Structure of this talk- What we currently know about this species Hydroperiods and topography Salinity Influence Intraspecific interactions Genetic structure and historical dynamics Pterocarpus stand variability from coastal to montane Next Steps

Hydroperiod Seasonally flooded wetland Figure 2. Water depth measurements in the pasture side, low salinity (N = 12) and Laguncularia side, high salinity (N = 12) sections of 1-ha plot in Sabana Seca, Puerto Rico. Rivera Ocasio et al. (2007) Journal of Tropical Ecology 23:559 568.

Salinity effects on forest structure Basal area of Pterocarpus swamp forests decreases along salinity gradients that range from 9.7 to 15.0.

Salinity effects on Forest Structure 50 Position in the 1ha plot 40 30 20 10 Juveniles pasture side 0 0 50 100 150 200 50 Low salinity High salinity Laguncularia side Position in the 1ha plot 40 30 20 10 Adults 0 0 50 100 150 200

Salinity - Forest Structure - Mortality - Distribution pasture side Low salinity High salinity Laguncularia side Rivera Ocasio et al. (2007) Journal of Tropical Ecology 23:559 568.

Salinity effects- Forest Dynamics-Growth 0 ppt 5 ppt 10 ppt Rivera Ocasio et al (2007) Journal of Tropical Ecology 23:559 568.

Salinity effects- Litter, flower and fruit production Leaf litter, flower and fruit production of Pterocarpus is 10 times less in high soil salinity than in low soil salinity. Eusse AM, Aide TM (1999) Plant Ecology 145: 307-315.

Pterocarpus officinalis- responses to salinity Despite some degree of salt tolerance P. officinalis cannot be considered a halophyte The species is unable to complete its life cycle in salt concentrations of 200 mm (12 ) NaCl Medina et al. 2007 identified that P. officinalis associated to mangroves occupies low salinity sites and sequesters Na in the rachis thus, actively preventing damage to leaf tissues

What do we currently know about the species? Hydroperiods and topography Salinity Influence Intraspecific interactions Genetic structure and historical dynamics Pterocarpus stand variability from coastal to montane populations Next steps

Salinity effects- Intraspecific interactions Root nodulation Rivera Ocasio et al (2007) Journal of Tropical Ecology 23:559 568. 10 ppt 5 ppt 0ppt In the absence of salt, inoculation had a positive effect on biomass production of Pterocarpus when compared to un-inoculated plants. At 10 of NaCl, the decrease of seedling biomass has been linked to the reduction of the number of nitrogen fixating nodules.

Salinity effects on Intraspecific interactions Root mycorrhizal colonization Pterocarpus officinalis is considered highly mycorrhizal dependent AM colonization is always >50% within low (<10%) salinity levels Saint-Etienne L, et al. (2006). Forest Ecology and Management 232 : 86-89.

What do we currently know about the species? Hydroperiods and topography Salinity Influence Genetic structure and historical dynamics Pterocarpus stand variability from coastal to montane populations Next Steps

Genetic diversity and Historical dynamics Pterocarpus officinalis populations show strong regional differentiation between Caribbean and Continental populations. Relatively high population differentiation within Puerto Rico. Conservation implications at the regional scale for populations from the two main regional groups. Within the Caribbean, Trinidad has the most diverse population. Within the Continent, Venezuela has high genetic diversity. Rivera-Ocasio et al. 2005 Conservation Genetics

Genetic diversity and Historical dynamics Molecular markers suggest historical isolation, local extinctions and recolonization events of areas within the Caribbean Basin. Clear separation between Insular (Puerto Rico, Trinidad and Dominican Republic) and Continental populations. Most P. officinalis populations had a unique haplotype per population, indicating isolation and restricted geneflow. Nuclear markers revealed that pollen dispersal is limited (Rivera Ocasio 2007). nrits- gene network

Genetic diversity and Historical dynamics cpdna- chloroplast structure/maternal seed dispersal history Two major haplotypes- High diversity in Central America -Differentiation between Venezuela and Trinidad

Genetic diversity and Historical dynamics A history of isolation, local extinctions and recolonization events within the Caribbean Basin. Strong regional differentiation between Caribbean and Continental populations. The Dominican Republic had similarities with both regional groups, suggesting historical geneflow, This correlates very well with sea currents within the Caribbean Basin and the influence of the Orinoco River plume.

Pterocarpus stands dynamics from coastal to montane populations Coastal Stands are strongly structured by salinity and flooding Montane Stands are structured by flooding along rivers and seasonal variations in the water table.

Pterocarpus stands dynamics from coastal to montane populations-leaves Leaf K [ ] is greater in coastal sites, less in montane sites. Leaf percent carbon was greater in montane sites. No differences between sites in terms of N of leaves or fine roots.

Pterocarpus stands dynamics from coastal to montane populations-root nodules Montane sites greater nodule mass and more (96.3%) nodules active, compared to coastal sites (82.2%)

Pterocarpus from coastal to montane populations- Root nodules Nodule mass and diameter were larger near the surface of the soil and in montane sites.

Next steps Measure along salinity gradients and along the continuum of coastal - montane ecosystems -soil carbon, -leaf decomposition rates, -nitrogen fixation and accumulation rates Measure hydroperiod in coastal and montane stands to understand sea level rise impacts.

Next steps Study the function and structure of this wetland species under its current range of environmental conditions Help establish practical conservation goals that will maintain this species and the wetlands where it occurs.