Environmental conditions and vascular cambium regulate carbon allocation to xylem growth in deciduous oaks

Abstract

Summary Environmental conditions and the structure of the dormant cambium are assumed to affect seasonal patterns of cambial activity, hence controlling allocation of non‐structural carbohydrates (NSC) to growth. However, seasonal dynamics of xylogenesis, and their connections with NSC content and dormant cambium size, have been rarely assessed along an environmental gradient. We monitored xylogenesis and leaf phenology during 2012 and 2013, and NSC in 2012, for the drought‐sensitive Quercus robur and the drought‐tolerant Quercus pyrenaica along a water‐availability gradient in the north‐western Iberian Peninsula, and analysed dependencies of xylem production and phenology on the number of cells in dormant cambium. Study oak species showed comparable seasonal fluctuations in cambial activity and NSC content, despite Q. pyrenaica had a shorter growing season and a lower wood production than Q. robur. A sharp drop in spring NSC levels at all study sites evidenced that stored carbohydrates were crucial for earlywood formation. Under drier conditions, both species extended the growing period in spring and autumn, but reduced and even stopped xylogenesis in summer, showing an enhanced NSC accumulation before dormancy. A higher number of cells in dormant cambium of large dominant oaks accounted for their wider xylem increments and longer active periods. Our study demonstrates that xylogenesis is modulated by predisposing effects of dormant cambium size on xylem production and growing season length. Moreover, the high plasticity of cambial activity in deciduous oaks would confer resistance against recurrent summer drought through the improvement of the NSC status. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12789/suppinfo is available for this article.

Forest resilience to drought varies across biomes

“…Species such as the drought-adapted P. nigra and the drought-sensitive P. sylvestris display marked differences in their post-drought recovery and drought resistance (Marqu es, Camarero, Gazol, & Zavala, 2016). Conversely, other species from temperate or transitional sub-Mediterranean forests such as Q. robur or Q. pyrenaica may maintain growth during dry periods at the expense of a shorter vegetative period (P erez- de-Lis et al, 2017). This trade-off between forest resistance to drought and recovery after drought has been reported previously Gazol, Ribas et al, 2017), yet their mechanisms, causes, and consequences are still poorly understood.…”

“…The resistance of juniper to moderate drought stress (West, Hultine, Sperry, Bush, & Ehleringer, 2008) and few legacy effects after water shortage (Peltier et al, 2016) could be explained by their tendency to display anisohydric behaviour and a very negative hydraulic potential . Conversely, other species from temperate or transitional sub-Mediterranean forests such as Q. robur or Q. pyrenaica may maintain growth during dry periods at the expense of a shorter vegetative period (P erez-de-Lis et al, 2017). It is plausible that a great capacity to recover after drought may be due to a greater plasticity in stomatal regulation (Klein, 2014).…”

Climatic sensitivity of Quercus robur L. in floodplain near Kyiv under river regulation

“…This pattern is probably linked to the mechanism of non-structural carbohydrates accumulation (Pérez-de-Lis et al, 2016a) contributed to cambium activity and vessel enlargement that in Q. robur begins before budburst, leaf expansion, and thus carbon assimilation (Sass-Klaassen et al, 2011;Pérez-de-Lis et al, 2016b). In the Lisnyky forest, the June heat significantly diminishing current tree-ring width probably leads to an overall slowdown of the xylogenesis or its cessation (Pérez-de-Lis et al, 2017). Such premature ring growth completion triggers accumulation of soluble sugars and starch providing earlywood formation with readily available energy and material during the next growing season (Barbaroux & Bréda, 2002;Pérez-de-Lis et al, 2017).…”

“…In the Lisnyky forest, the June heat significantly diminishing current tree-ring width probably leads to an overall slowdown of the xylogenesis or its cessation (Pérez-de-Lis et al, 2017). Such premature ring growth completion triggers accumulation of soluble sugars and starch providing earlywood formation with readily available energy and material during the next growing season (Barbaroux & Bréda, 2002;Pérez-de-Lis et al, 2017). The positive growth response to prior-August rainfall indicates that the Lisnyky floodplain is prone to drought in late summer and that water availability in this period may be crucial for carbon assimilation and non-structural carbohydrates storage.…”

Genetic features of the phenological forms of Quercus robur (Fagaceae) according to the analysis of the introns polymorphism of β-tubulin genes and microsatellite loci

“…У природних популяціях існують і перехідні фенологічні форми Q. robur (Utkina, Rubtsov, 2017), тому при ідентифікації рослин зважають на комплекс ознак фенотипу. Разом із тим варіації сезонного розвитку в популяціях Q. robur можуть бути наслідком звичайної мінливості, пов'язаної з особливостями умов зростання дерев (Pérez-de-Lis et al, 2017).…”