Cambial activity in five species of the tropical dry forest: dynamics of seasonal changes in the cambial region

Abstract Key message This study in tropical dry forests reveals cambial activity varies by species and site, linked to rainfall patterns, impacting tree growth and highlighting importance of xylem and phloem development consideration. Abstract Ecological studies on cell division in the vascular cambium have emerged as a key need for understanding tree growth dynamics in tropical dry forests, as well as the effects of year-to-year variation in precipitation. To address this gap, we selected five representative tree species from the tropical dry forest to study dynamics in vascular cambium cell division. The study was conducted at three sites in Mexico with different rainfall regimes from May 2022 to May 2023. Monthly samples were collected, and anatomical features were recorded during cambial activity. The beginning and end of cambial activity were established, and differences between species and sites were analyzed. Linear and exponential models were tested to fit the data. The cambium remained active for six to nine months. Cell divisions toward the phloem maintained cambial activity until the dry season, and in 2023, cambial reactivation occurred with the formation of new phloem. The number of cells in the cambial region showed high monthly variation, with a rapid increase during the first months of the rainy season and a peak between July and November. Cell numbers gradually decreased toward the end of the dry season. Tree species showed low variation between sites. Site analysis supported the adjustment of different growth models and growth rates across sites. Cell divisions were faster at the site with the least precipitation and slower at the wetter site. This study highlights the importance of considering xylem and phloem formation when studying cambial activity, providing valuable insights into tropical dry forest ecology.