Biomass Dynamics in a Fragment of Brazilian Tropical Forest (Caatinga) over Consecutive Dry Years

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  • Increases in water scarcity due to climate change, especially in dry regions, can affect the dynamics of successional species. In view of the longest sequence of dry years (2010-2019) to have occurred in the Brazilian semi-arid region, with a consequent reduction in water availability, the influence of rainfall distribution on the production of above-ground plant biomass was investigated in a Dry Tropical Forest (DTF). This natural change monitoring experiment was conducted over 11 years (2009-2019) in a fragment of DTF under regeneration for 40 years, in the district of Iguatu, Ceara, Brazil. All living individuals of the woody component with a Diameter at Ground Level (DGL) >= 3 cm and a height (h) >= 100 cm were measured during 2009-2010, 2015-2016, 2018-2019. Biomass production was calculated using an allometric equation defined for DTF species. A mean mortality rate of 134 ind. ha(-1) yr(-1) was registered, with a recruitment of 39 ind. ha(-1) yr(-1), generating a mean deficit of 95 ind. ha(-1) yr(-1). The mean reduction in biomass was 3.26 Mg ha(-1) yr(-1). Climate conditions during consecutive dry years have a direct effect on the mortality and recruitment of woody species, with a recruitment/mortality ratio of 0.11. Shrubby-tree individuals of smaller diameter showed less resilience to the cumulative effect of drought.