Annual Cambial Rhythm in Pinus halepensis and Pinus sylvestris as Indicator for Climate Adaptation

Abstract

To understand better the adaptation strategies of intra-annual radial growth in Pinus halepensis and Pinus sylvestris to local environmental conditions, we examined the seasonal rhythm of cambial activity and cell differentiation at tissue and cellular levels. Two contrasting sites differing in temperature and amount of precipitation were selected for each species, one typical for their growth and the other represented border climatic conditions, where the two species coexisted. Mature P. halepensis trees from Mediterranean (Spain) and sub-Mediterranean (Slovenia) sites, and P. sylvestris from sub-Mediterranean (Slovenia) and temperate (Slovenia) sites were selected. Repeated sampling was performed throughout the year and samples were prepared for examination with light and transmission electron microscopes. We hypothesized that cambial rhythm in trees growing at the sub-Mediterranean site where the two species co-exist will be similar as at typical sites for their growth. Cambium in P. halepensis at the Mediterranean site was active throughout the year and was never truly dormant, whereas at the sub-Mediterranean site it appeared to be dormant during the winter months. In contrast, cambium in P. sylvestris was clearly dormant at both sub-Mediterranean and temperate sites, although the dormant period seemed to be significantly longer at the temperate site. Thus, the hypothesis was only partly confirmed. Different cambial and cell differentiation rhythms of the two species at the site where both species co-exist and typical sites for their growth indicate their high but different adaptation strategies in terms of adjustment of radial growth to environmental heterogeneity, crucial for long-term tree performance and survival.

Application of confocal laser scanning microscopy in dendrochronology

“…They are characterised by latewood-like cells in earlywood (E-IADF), and earlywood like cells in different portions of latewood (L-IADF) ( Figure 4). The species often have unclear growth ring bound- aries (Figure 4b) which are a consequence of uninterrupted cambial production in winter (De Luis et al, 2007De Micco et al, 2016a;Novak et al, 2016a;Balzano et al, 2018Balzano et al, , 2019a, and lack of cambial dormancy in winter (Prislan et al, 2016). The species can also contain dark rings (Figure 4b), i.e.…”

“…Prirastne plasti alepskega bora (Pinus halepensis) vsebujejo številne gostotne variacije (IADF), ki jih je starejša literatura poimenovala lažne branike (slika 4a, b), zato je na splošno težko ugotoviti, kaj je branika in ali je nastala znotraj istega koledarskega leta (De Novak et al, 2016a;Balzano et al, 2018Balzano et al, , 2019. Vrsta ima pogosto nejasne meje med prirastnimi plastmi (slika 4b), ki so posledica neprekinjenega delovanja kambija tudi pozimi (Prislan et al, 2016). Pojavljajo se tudi »temne branike«, ki predstavljajo prirastne plasti, ki v osnovi vsebujejo le kasni les (Novak et al, 2016a) (slika 4c).…”

Summer drought reconstruction in northeastern Spain inferred from a tree ring latewood network since 1734

“…The relationship between latewood growth and evapotranspiration during summer has already been explored in recent work from the Pyrenees, using maximum latewood density [Büntgen et al, 2008;Dorado-Liñán et al, 2012]. Further studies are needed to assess this finding since in other species growing at lower altitudes under stronger summer stress, the reduction of photosynthetic activity during summer is compensated by the species' ability to resume growth in autumn when conditions are favorable [de Luis et al, 2007;Novak et al, 2013;Martinez del Castillo et al, 2016;Prislan et al, 2016]. In light of projected global warming, a higher water demand during summer would translate into a decrease in latewood width, which may have implications on forest sustainability.…”

“…Since latewood substantially contributes to stem mechanical stability and stores large amounts of water, a lower proportion of this xylem tissue would tend to reduce drought resistance [Domec and Gartner, 2002;Martinez-Meier et al, 2008, de Luis et al, 2011. Further studies are needed to assess this finding since in other species growing at lower altitudes under stronger summer stress, the reduction of photosynthetic activity during summer is compensated by the species' ability to resume growth in autumn when conditions are favorable [de Luis et al, 2007;Novak et al, 2013;Martinez del Castillo et al, 2016;Prislan et al, 2016]. Intraspecific plasticity of cambial phenology of P. sylvestris and P. uncinata needs to be studied in more detail to better evaluate the ecological consequences these our findings.…”

Assessment of Atmospheric Deposition and Vitality Indicators in Mediterranean Forest Ecosystems

“…A study in Spain suggests that drought was the key climatic factor explaining variations in growth patterns of Aleppo pine and black pine [51]. For Mediterranean Pinus species, it is known that under favorable growth conditions, the vascular cambium may be active throughout the entire year [52,53]. Tree vitality can be defined as the ability of a tree to assimilate, to survive stressful conditions, to react to a changing environment, and to reproduce [54].…”