Litterfall Production Prior to and during Hurricanes Irma and Maria in Four Puerto Rican Forests

Abstract

Hurricanes Irma and Maria struck Puerto Rico on the 6th and 20th of September 2017, respectively. These two powerful Cat 5 hurricanes severely defoliated forest canopy and deposited massive amounts of litterfall in the forests across the island. We established a 1-ha research plot in each of four forests (Guánica State Forest, Río Abajo State Forest, Guayama Research Area and Luquillo Experiment Forest) before September 2016, and had collected one full year data of litterfall production prior to the arrival of Hurricanes Irma and Maria. Hurricane-induced litterfall was collected within one week after Hurricane Irma, and within two weeks after Hurricane Maria. Each litterfall sample was sorted into leaves, wood (branches and barks), reproductive organs (flowers, fruits and seeds) and miscellaneous materials (mostly dead animal bodies or feces) after oven-drying to constant weight. Annual litterfall production prior to the arrival of Hurricanes Irma and Maria varied from 4.68 to 25.41 Mg/ha/year among the four forests, and annual litterfall consisted of 50-81% leaffall, 16-44% woodfall and 3-6% fallen reproductive organs. Hurricane Irma severely defoliated the Luquillo Experimental Forest, but had little effect on the other three forests, whereas Hurricane Maria defoliated all four forests. Total hurricane-induced litterfall from Hurricanes Irma and Maria amounted to 95-171% of the annual litterfall production, with leaffall and woodfall from hurricanes amounting to 63-88% and 122-763% of their corresponding annual leaffall and woodfall, respectively. Hurricane-induced litterfall consisted of 30-45% leaves and 55-70% wood. Our data showed that Hurricanes Irma and Maria deposited a pulse of litter deposition equivalent to or more than the total annual litterfall input with at least a doubled fraction of woody materials. This pulse of hurricane-induced debris and elevated proportion of woody component may trigger changes in biogeochemical processes and soil communities in these Puerto Rican forests.

Hurricane Maria in the U.S. Caribbean: Disturbance Forces, Variation of Effects, and Implications for Future Storms

“…Overall, there was a very good ability to model the spatial variation of the hurricane effects with the simple models. Furthermore, the percentage of greenness loss in the region (31%) and the much larger amount in the LEF (51%), agrees with the small number of field studies that have been conducted so far [39,40]. The studies are not quite correspondent, since these other studies were focused on litterfall and tree damage (not equivalent to canopy greenness loss) and calculated greenness loss here was up to a month after the hurricane (because of satellite image quality limitations discussed in the methods).…”

Persistent Hydrological Consequences of Hurricane Maria in Puerto Rico

“…Using remote sensing techniques, one recent effort estimated that Maria caused immediate mortality or severe damage to 23-31 million trees (Feng et al, 2018). Similarly, forest plots sampled at four locations across Puerto Rico indicated that the pulse of litterfall associated Hurricanes Irma and Maria was equivalent to 95-171% of the mean annual total (Liu et al, 2018). However, litterfall from Hurricane Irma was actually greater than from Maria for the forest plot nearest to Irma's path, supporting the idea of an Irma-related LAI response in Figure 2a.…”

The effects of Hurricane Otto on the soil ecosystems of three forest types in the Northern Zone of Costa Rica

“…These disturbances alter the forest vegetation composition and productivity, through tree damage [3]. Hurricanes cause rapid deposition of significantly large amounts of leaf litter and woody debris from the canopy to the forest floor [4] , [5], [6], [7], which then results in short to long-term changes to the forest structure and forest ecological processes [4]. These processes are critical to forest recovery, and are associated with both the rapid increase in the carbon (C) and nitrogen (N) nutrients [8], [9], [10], [11] and the subsequent influences to the soil microbiota [12], [13].…”

“…There have been studies on the effects of hurricane-induced litter fall and enhanced soil nutrients on soil processes (especially decomposition) that have shown the patterns observed are a function of the characteristics of the specific hurricane, and that of the forest before the hurricane hit, making it difficult to predict specific effects from the hurricane-induced dropping of canopy material [8]. Moreover, much of the leading work has been conducted under hurricane simulation experiments in which canopy components are cut and dropped to the forest floor (for example: [6] [9] [14] [15] [16]), which leads to the important question of "what happens under real conditions and are they different?". Clearly, there is much work to be conducted, but doing work in the same forest location before and after a hurricane is truly a serendipitous opportunity.…”

“…Based on the previous literature [4][5][6][7][8][9][10][11], we predicted that the likely deposition of fresh leaf litter and excessive woody debris deposited on the forest floor during Hurricane Otto would result in increased levels of inorganic N and C biomass, as indicators of enhanced microbial activity involved in the decomposition and incorporation of the extra C and N material into the forest biota, and would be associated with an increase in the abundance of the microbes associated with these activities.…”