The relative weight of ontogeny, topology and climate in the architectural development of three North American conifers

Abstract

Knowledge of plant architecture allows retrospective study of plant development, hence provides powerful tools, through modelling and simulation, to link this development with environmental constraints, and then predict its response to global change. The present study aims to determine some of the main endogenous and exogenous variables driving the architectural development of three North American conifers. We measured architectural traits retrospectively on the trunk, branches and twigs of whole tree crowns for each species: annual shoot length (ASL), needle length, branching patterns and reproduction organs (male and female). We fitted a partial least square (PLS) regression to explain each architectural trait with respect to topological, ontogenic and climatic variables. Results showed a significant weight of these three groups of variables for previous and current year, corresponding, respectively, to organogenesis and elongation. Topological and ontogenic variables had the greatest weight in models. Particularly, all architectural traits were strongly correlated with ASL. We highlighted a negative architectural response of two species to higher than average temperatures, whereas the third one took advantage of these higher temperatures to some degree. Tree architectural development weekly but significantly improved with higher precipitation. Our study underlines the strong weight of topology and ontogeny in tree growth patterns at twig and branch scales. The correlation between ASL and other tree architectural traits should be integrated into architectural development models. Climate variables are secondary in importance at the twig scale. However, interannual climate variations influence all axis categories and branching orders and therefore significantly impact crown development as a whole. This latter impact may increase with climate change, especially as climate affects architectural traits over at least 2 years, through organogenesis and elongation.

Short Shoot Growth and Reproduction Response to Light Conditions Vary with Order Branching in the Proximal Part of C. atlantica Crown

“…[38] has found null and strong effect of shade on the production of long shoot in Betula pubescens depending on the year, suggesting that Atlas cedar is less sensitive to shading because the short shoot production of neither the branch order 2 nor the branch order 3 was affected by shading. Suzuki and Maki Suzuki [27] reported that, in Eurya japonica, the annual shoot length decreased with increasing branching order as has been found for many young and adult conifers [11,12,14] like pines and spruce [13].…”

“…Colombo and Templeton [13] have revealed that the annual shoot length was strongly correlated with branch position in the crown, thus with branch age in pines and spruce. In the same way to the latter authors, Buissart et al [14] demonstrated that the annual shoot length and the total number of branches and whorled branches were highly variable and decreased with age and with increasing branching order for Picea mariana, Pinus banksiana, and Pinus strobus. In contrast, Remphrey and Davidson [15] announced that generally, older branches tend to grow slowly whereas lengths of current shoots of major order 1 branches were found to decrease with increasing depth in the crown [16].…”

“…is study shows that neither the order nor the light affects the production of short shoots and that the young branches of order 3 behave in the same way as those of lower order visa-vis of the light availability. Buissart et al [14] for many conifers established that the total number of branches and whorled branches decreased with increasing branching order. However, Sabatier and Barthélémy [8] have showed that sylleptic axillary shoot occurred only on annual shoots of the branch orders 1 and 2 when the extension rate was at its highest but did not occur in branch order 3.…”

The dynamics of primary growth in woody species from rain and transitional forests of Argentinean north Patagonia

“…The minimum number of individuals per species was 15, taking into account the number of plants commonly used in primary growth dynamics research (e.g. Poorter et al 2006;Stecconi et al 2017;Buissart et al 2018).…”

“…It may be hypothesized that primary-growth patterns could change, in evolutionary time, from continuous to rhythmic or vice-versa. This hypothesis may be tested by means of the evaluation of endogenous and environmental influences on the primary growth of woody plants (Buissart et al 2018). Such information is highly interesting, considering that current global tendencies point to increments in climatic variability for temperate regions (Matthews et al 2016), which would impact on plant fitness in future scenarios.…”