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.
Highlights
Litterfall regulates nutrient cycling [1], changes diversity and biomass of soil and litter invertebrates [2,3], boosts the transfer of soil CO2 to the atmosphere [4], may cause seedling mortality [5], is a major source of soil organic carbon [6], and reflects the complex interaction betweenForests 2018, 9, 367; doi:10.3390/f9060367 www.mdpi.com/journal/forestsForests 2018, 9, 367 environmental and physiological factors [7,8] in forest ecosystems
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
This study focused on the quantity and composition of litterfall prior to the arrival of and from Hurricanes Irma and Maria
Summary
Litterfall regulates nutrient cycling [1], changes diversity and biomass of soil and litter invertebrates [2,3], boosts the transfer of soil CO2 to the atmosphere [4], may cause seedling mortality [5], is a major source of soil organic carbon [6], and reflects the complex interaction betweenForests 2018, 9, 367; doi:10.3390/f9060367 www.mdpi.com/journal/forestsForests 2018, 9, 367 environmental and physiological factors [7,8] in forest ecosystems. The instant input of massive litterfall amounts after a hurricane can trigger changes in physical and chemical environments within forests at both small and large temporal and spatial scales, resulting in the alteration of forest successional stage and development [9,10]. Forest productivity is the primary factor controlling litterfall production [15,16]. Annual litterfall production of the world’s tropical forests have been reported to range from 15.3 Mg/ha/year in Zambezian woodlands [17] to 5.2 Mg/ha/year in Hawaiian montane rain forests [1]. It was reported that the net primary productivity in Puerto Rican Tabonuco forest, Palo Colorado forest and Elfin forest was 10.5, 7.6 and 3.7 Mg/ha/year, respectively, and the annual litterfalls were 8.6, 6.8 and
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