Critical temperatures for xylogenesis in conifers of cold climates

Abstract

Aim To identify temperatures at which cell division and differentiation are active in order to verify the existence of a common critical temperature determining growth in conifers of cold climates. Location Ten European and Canadian sites at different latitudes and altitudes. Methods The periods of cambial activity and cell differentiation were assessed on a weekly time-scale on histological sections of cambium and wood tissue collected over 2 to 5 years per site from 1998 to 2005 from the stems of seven conifer species. All data were compared with daily air temperatures recorded from weather stations located close to the sites. Logistic regressions were used to calculate the probability of xylogenesis and of cambium being active at a given temperature. Results Xylogenesis lasted from May to October, with a growing period varying from 3 to 5 months depending on location and elevation. Despite the wide geographical range of the monitored sites, temperatures for onset and ending of xylogenesis converged towards narrow ranges with average values around 4-5, 8-9 and 13-14 degrees C for daily minimum, mean and maximum temperature, respectively. On the contrary, cell division in the cambium stopped in July-August, when temperatures were still high. Main conclusions Wood formation in conifers occurred when specific critical temperatures were reached. Although the timing and duration of xylogenesis varied among species, sites and years, the estimated temperatures were stable for all trees studied. These results provide biologically based evidence that temperature is a critical factor limiting production and differentiation of xylem cells in cold climates. Although daily temperatures below 4-5 degrees C are still favourable for photosynthesis, thermal conditions below these values could inhibit the allocation of assimilated carbon to structural investment, i.e. xylem growth

Temperate and boreal forest tree phenology: from organ-scale processes to terrestrial ecosystem models

“…2). In natural stands, the onset of cambial activity occurs within a relatively narrow range of daily minimum air temperature (+2 to +7°C in 80% of the data; Rossi et al 2008), resulting in altitudinal gradients of cambium resumption (Moser et al 2010;Oladi et al 2010;Prislan et al 2013). Moreover, the resumption of cambial activity can be triggered during late winter by an artificial heating of tree stems (Oribe et al 2003;Begum et al 2007Begum et al , 2010.…”

“…However, the influence of temperature on cambium activity remains equivocal. Indeed, the cessation of the division of cambial initials in late summer or autumn occurs at considerably milder temperatures than those for spring resumption (between +5°C and +13°C for gymnosperms, Rossi et al 2008), but cessation can be hastened by artificial cooling (Gričar et al 2007). This equivocal role of temperature results in the absence of clear altitudinal gradients in the timing of the cessation of cambial activity (Moser et al 2010;Oladi et al 2010;Prislan et al 2013).…”

Fingerprints of extreme climate events in Pinus sylvestris tree rings from Bulgaria

“…In order to injure the newly formed tracheids, these frost events must have happened after the start of cambial activity (Glerum and Farrar 1966;Hantemirov et al 2004). We did not study the onset of cambial activity in detail, but in analogy with other studies we expect it to start after the middle of April at xeric sites (Antonova et al 1995;Gruber et al 2010;Eilmann et al 2011) and at the beginning of May at high altitude sites (Rossi et al 2003(Rossi et al , 2008Gruber et al 2009). This is why we consider that frost events recorded at the beginning of May at lower altitude sites or in the middle of May at higher altitudes could have damaged cambial cells and newly formed tracheids.…”

“…A strong influence of summer temperature is often found at high altitude sites (Fritts 1976;Camarero et al 1998;Rossi et al 2008). Yet it is sometimes recorded not in tree-ring width, but in other parameters such as maximum latewood density (Trouet et al 2012).…”

“…At these sites, trees are most sensitive to local limiting factors and react most distinctively to changes in them . Typical examples are alpine treeline sites, where low temperatures are the primary limiting factor (Rossi et al 2008), or dry sites, where low precipitation is the primary limiting factor (Cherubini et al 2003;Rigling et al 2001;Büntgen et al 2010). Yet, studies about the influence of extreme climatic events on tree rings are scarce and limited to only a few locations around the world, thus hindering the broad-scale estimation of possible changes in their frequency.…”