LB 23-200 - Species recruitment in the Luquillo Forest Dynamics Plot (LFDP) following Hurricane Maria: Preliminary report

Shifts in forest dynamics following natural disturbances, such as hurricanes, are well studied in many tropical ecosystems, but modern predictions forecast that many disturbances, including hurricanes will increase in frequency and intensity in coming decades. Fast-growing and early successional species dominate a forest following a large storm in response to open canopy conditions and increased light availability due to the loss of mature canopy. Therefore, forest dynamics of newly recruiting trees is of particular interest. Hurricane Maria made landfall in Puerto Rico in September of 2017 and was the most destructive hurricane in 91 years,. The 16-ha Luquillo Forest Dynamics Plots (LFDP), located in the Luquillo Experimental Forest in northeastern Puerto Rico, is a member of the Forest Global Earth Observatory (ForestGEO) long-term monitoring project. Every ~5 years, a complete census of the LFDP measures, maps, and identifies all trees >1 cm DBH. We present preliminary results comparing the pre-hurricane Maria (2016) census data and 5 years post-hurricane Maria (2021). We found that 68 species of new recruits (i.e. trees large enough to be added to the census) were present in 2016 compared to 105 species present in 2021. The post-hurricane forest was significantly denser with an average of 3,878.02 alive trees/ha, compared to 1,712.40/ha in 2016; of all alive trees, 56.58% were new recruits in 2021 while 2.17% were new recruits in 2016. Although the post-hurricane forest is dominated by early successional species such as Cecropia schreberiana, Psychotria berteroana and Schefflera morototoni, Shannon–Wiener diversity index was significantly higher in 2021, likely driven by a larger number of individuals present in the census and wind-assisted seed dispersal during the storm. Long-term monitoring plots like the LFDP provide a better understanding of the effect of intense storms on a forest already disturbed by previous natural disasters, especially in regards to recruitment of new trees. Ongoing data collection for the 2021 census will supplement this study to provide a more complete picture of how the Luquillo forest responds to repeated intense climate events.