Tree growth responses to climate variation in upland and seasonally flooded forests and woodlands of the Cerrado-Pantanal transition of Brazil

Tropical forest trees are sensitive to climate variations, especially during anomalously warm and dry years that occur during El Nin similar to o. However, species growth responses are poorly understood. We measured annual stem growth of 27 different tree species from upland and seasonally flooded forests and woodlands in the Cuiaba Basin and Northern Pantanal of Mato Grosso, Brazil. Stem growth increment was measured using plastic, spring-loaded dendrometer bands installed on 344 trees. Measurements were made between 2015 and 2019, which encompassed the 2015-16 El Nin similar to o that was one of the warmest and driest on record. Relative stem growth rates (RGR) at both sites increased with higher rainfall and declined with an increase in maximum temperature, but the RGR of trees in the Cuiaba Basin also declined as the length of the dry season increased. RGR, and the response of RGR to climate variation, varied substantially across species. Some species only exhibited a significant RGR response to variations in rainfall, maximum temperature, or dry season length, other species responded to more than one climate variable, and a subset were insensitive to the variation in all three climate variables studied. Rainfall appeared to be a stronger control on RGR in the predominately upland Cuiaba Basin (87% of species exhibited a significant RGR response to rainfall in the Cuiaba Basin vs. 39% in the Pantanal) while temperature was a stronger control on RGR in the seasonally flooded Pantanal (67% of species exhibited a significant RGR response to temperature in the Pantanal vs. 53% in the Cuiaba Basin). While our study period was short, and measurements were done on a small subset of available species, our data indicate that variations in climate affect the growth of tropical forest and woodland tree species differently. These species-specific responses have the potential to alter community diversity and productivity as climate change ensues.