Changes in mangrove tree mortality, forest canopy, and aboveground biomass accumulation rates following the 2017 hurricane season in Puerto Rico and the role of urbanization

Abstract

15Mangrove ecosystem responses to tropical cyclones have been well documented over the last 16 half a century, resulting in repeated measures of tree mortality, aboveground biomass reduction, 17 and recovery by species, size, and geomorphology. However, no studies have investigated the 18 role of urbanization in mangrove hurricane resistance and resilience, despite increasing 19 urbanization of tropical shorelines. This study gauges the initial response and short-term 20 recovery of Puerto Rico's mangroves along well defined and quantified urban gradients 21 following the 2017 hurricane season. Survival probability of tagged trees decreased with time, 22 and the mean mortality across all sites was 22% after eleven months. Mean canopy closure loss 23 was 51% one month after the hurricanes, and closure rates also decreased with time following 24 the storms. Aboveground biomass accumulation decreased by 3.5 kg yr -1 per tree, corresponding 25 to a reduction of 4.5 Mg ha -1 yr -1 at the stand level. One year later, the mangroves have 26 recovered to 72% canopy closure and to nearly 60% of their pre-storm growth rates. No 27 connection to urbanization could be detected in the measured dynamics. Instead, species, size 28 and geomorphology were found to play a role. Larger trees suffered 25% more mortality than 29 smaller size classes, and Laguncularia racemosa suffered 11% less mortality than other species. 30Hydro-geomorphology was also found to play a role, with forests in tidally restricted canals 31 experiencing more canopy loss but faster recovery than open embayment systems. These 32 findings suggest size, species, and geomorphology are important in mangrove resistance and 33 resilience to tropical storms, and that urbanization does not play a role. Managing mangrove 34 ecosystems for optimal shoreline protection will depend upon knowing which forests are at 35 greatest risk in a future of increasing urbanization. 36are more often conflicting than in agreement. Following hurricane Andrew in Florida, R. mangle 1 (Rhizophora mangle) was found to suffer the highest mortality, and L. racemosa (Laguncularia 2 racemosa) the least (A. H. Baldwin et al. 1995), but other studies of the same hurricane in 3 Florida found the opposite (Doyle et al. 1995; McCoy et al. 1996). Still another study of the 4 same storm in the Dominican Republic found L. racemosa to be the least affected, and A. 5 germinans (Avicennia germinans) the most (Sherman et al. 2001). Other studies for other storms 6 in other locations have found variations in species susceptibilities (Wadsworth 1959; Smith et al. 7 1994; Daniel Imbert 2018). This conflict might be explained by differences in habitat and hydro-8 geomorphology, both of which have also been found to play a role in storm related tree mortality 9 and forest recovery (Sherman et al.

Urbanization, environmental stabilization and temporal persistence of bird species: a view from Latin America

“…Fire activity was minimal at the edge of urban areas in the Sierras chicas (Argentina) and North Carolina (USA) (Argañaraz et al, 2015; Pickens et al, 2017). However, Branoff (2018) found no impacts of urbanization on mangroves vegetation resistance to hurricanes. On the other hand, floods may be increased by urbanization (Hollis, 1975; Konrad, 2003; Jacobson, 2011).…”