Format: ORAL

Fabrizio Carten1, Aleksandr Bobrovskikh1,2, Francesco Giannino1, Stefano Mazzoleni1

1 Department of Agricultural Sciences, University of Naples Federico II, Naples, Italy 2 Laboratory of Plant Growth Biomechanics, Institute of Cytology and Genetics Siberian Branch of Russian Academy of Sciences (SB RAS), Novosibirsk, Russia

Understanding the physiological mechanisms behind plant responses to environmental cues is crucial to assess the effect of global climate changes on forests. In this context, it is important to comprehend the extent to which wood growth is limited by either the availability of carbon sources or by the activity of the sink itself, i.e. the vascular cambium. Carbohydrates are produced by photosynthesis and allocated to vascular cambium through source-sink dynamics between competing sinks such as primary and secondary meristems in both shoots and roots. The vascular cambium is also directly affected by two main environmental factors, temperature and water availability. Here we present an original process-based modular modelling framework focusing on annual wood growth incorporating the main source and sink dynamics. A first module computes soil water availability and carbohydrates produced by photosynthesis, using temperature and rainfall inputs. A second module estimates the vegetative phenology of primary sinks, both above- and below-ground, and allocates the remaining available carbon resources to secondary growth. Finally, a wood growth module computes the dynamics of cambial cells divisions and xylem differentiation as a function of three external controlling factors: available carbohydrates, temperature, and water stress. The model outputs are the number of xylem cells produced through the season, the main anatomical traits of these cells (i.e., lumen area and wall thickness), overall wood radial growth and earlywood to latewood ratio. Model simulations are performed under different environmental conditions, representing a wide range of world climates, and the results are analysed and compared with general observed trends of tree ring characteristics. The emergence of Intra-Annual Density Fluctuations (IADFs) is also observed. The model approach seems promising, allowing for a better understanding of the dynamics of wood growth and carbon sequestration in forest ecosystems by an in-depth understanding of the balance between primary and secondary growth.