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

Abstract

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, Ceará, 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.

How Forest Management with Clear-Cutting Affects the Regeneration, Diversity and Structure of a Seasonally Dry Tropical Forest in Brazil

“…On the other hand, the contribution of both the early and late secondary ecological groups generally tended to increase with the regeneration time (treatments), characterising a difference between the groups in carrying out their ecological functions during the regeneration process in the SDTF after clear-cutting. A greater abundance of individuals of species belonging to the pioneer ecological group has been seen in research in this forest formation [20,26].…”

“…ha −1 to 2113 ind. ha −1 over an 11-year period [26]. They also found that mortality was more related to the stage of plant development (younger plants being more prone to death) than to species.…”

“…Even so, for some time now, more effort has been put into the search for knowledge, improvement and adaptation to a more balanced coexistence with the conditions inherent to the SDTF [14][15][16][17][18][19][20][21][22]. Some studies, however, only highlight aspects of certain forest physiognomies [23,24], while others address regeneration and/or succession [4,5,[25][26][27][28][29]. Studying this environment continues to be urgent since, among other aspects, it will be adversely affected by ongoing climate change [30] while at the same time undergoing greater pressure on its natural resources.…”

Morphophysiological changes in Bauhinia cheilantha (Bong.) Steud. (Fabaceae) caused by water deficit

“…This species has a broad geographic distribution and is also present in landscapes of the Brazilian seasonally dry tropical forest known as the Caatinga. B. cheilantha colonizes both primary and secondary forest formations with varying degrees of plasticity in various untested attributes in this study (Campos et al, 2020). We hypothesize that physiological traits will have a higher degree of change compared to morphological traits, potentially resulting in phenotypic plasticity.…”

Canopy Effects on Rainfall Partition and Throughfall Drop Size Distribution in a Tropical Dry Forest

“…March and April receive 43% of the annual rainfall [22], with a high occurrence of consecutive dry days [28,29]. The dry period occurs from June to December, with only 1% of the total annual rainfall [22], showing the high temporal variability of rainfall [28,30]. The annual potential evapotranspiration surpasses 2000 mm, which is within the 0.2 and 0.5 rainfall-to-potential evapotranspiration ratio described by [31] for semi-arid regions and has an aridity index of 0.48 [32] that also classifies the region as semi-arid, where water scarcity is observed 9 to 10 months per year [33].…”