COS 239-4 - Dynamic range of the contribution of down woody materials on the carbon stocks of Caribbean forests

Background/Question/Methods

The amount of dead woody material in forested stands represents a vital piece of information for tropical forest management due to its contribution to stand biomass, carbon cycling, and its influence on wildfires. The Caribbean archipelago of Puerto Rico (PR), subject to periodic extreme weather events and where forests cover 55 percent of the land area, offers the opportunity to study changes in the contribution of down woody materials to forest carbon stocks. Using data from the USDA Forest Service, Forest Inventory and Analysis program, we analyze the total amount of forest carbon in downed woody materials from 2006 to 2018 within dry, moist, and wet/rain forest types in PR.

Results/Conclusions

The density of coarse woody debris decreased in the dry forest from 9.32 Mg/ha to 1.53 Mg/ha, contrasting with increases from 2.43 Mg/ha to 5.87 Mg/ha in the moist forest and from 5.55 Mg/ha to 15.60 Mg/ha in the wet/rain forest. The higher values of density within dry stands at the beginning of the study period in 2006 suggest that the tropical storm Jeanne (2004), which became a hurricane after hitting PR with high sustained winds particularly within the dry forest zone, was a disturbance resulting in large amounts of downed wood biomass. Contrastingly, the increase within moist and wet/rain stands resulted from the passage of hurricanes Irma and María in 2017, which have a minor effect at low elevation sites where dry forest stands are present. Pre-Irma and María analysis show a general decreasing trend in downed woody biomass in all forest types correlated with the maturity of the predominant secondary forest stands. The pulses of downed wood along succession and as part of extreme weather events provide insight about the influence of time and recurring disturbances on dead biomass loadings under a panorama of climate change in need of conservation management.