Inter-annual and decadal changes in teleconnections drive continental-scale synchronization of tree reproduction

Abstract

Climate teleconnections drive highly variable and synchronous seed production (masting) over large scales. Disentangling the effect of high-frequency (inter-annual variation) from low-frequency (decadal trends) components of climate oscillations will improve our understanding of masting as an ecosystem process. Using century-long observations on masting (the MASTREE database) and data on the Northern Atlantic Oscillation (NAO), we show that in the last 60 years both high-frequency summer and spring NAO, and low-frequency winter NAO components are highly correlated to continent-wide masting in European beech and Norway spruce. Relationships are weaker (non-stationary) in the early twentieth century. This finding improves our understanding on how climate variation affects large-scale synchronization of tree masting. Moreover, it supports the connection between proximate and ultimate causes of masting: indeed, large-scale features of atmospheric circulation coherently drive cues and resources for masting, as well as its evolutionary drivers, such as pollination efficiency, abundance of seed dispersers, and natural disturbance regimes.

It is not just a ‘trade‐off’: indications for sink‐ and source‐limitation to vegetative and regenerative growth in an old‐growth beech forest

“…5a). When considering the multiple collinearity among weather signals (namely p, T and Rg) and the negative correlation between wet, cold and dry, hot conditions in consecutive summers (see also Ascoli et al, 2017) this driver may not contradict but complete the often-observed weather cues for periodically high fruit production such as high temperature or drought in the previous summer or differences in summer temperature between the preceding 2 yr (Piovesan & Adams, 2001;Kelly & Sork, 2002;Gruber, 2003;Kelly et al, 2013;Drobyshev et al, 2014;Hacket-Pain et al, 2015;Kon & Saito, 2015;Ascoli et al, 2017;Vacchiano et al, 2017). However, the lack of any significant correlation between fruit-NPP and GPP during any period of the current or the previous 2 yr questioned the assumption that the weather signals would trigger fruit production via carbon assimilation (Gruber, 2003;M€ uller-Haubold et al, 2015).…”

“…A triggering of fruiting by high precipitation in (tÀ2) could be explained by higher decomposition rates and a higher water uptake associated with an higher uptake of nutrients in wet compared to dry years, leading to higher levels of mineral nutrients in (tÀ1) that may promote bud formation (ʻresource prim-ingʼ, Ascoli et al, 2017). A priming via high carbon assimilation in (tÀ2) seems to be unlikely as no significant correlation between p June-August and GPP was found (see also Tamrakar et al, 2018).…”

“…The negative correlation between stem and fruit growth and the high investment of nutrient resources into fruit production, particularly in tree species with large fruits and strong periodicity in fruiting, supports the assumption that masting is controlled by resource availability (Piovesan & Adams, ; Kelly & Sork, ; Schmidt, ; Yasumura et al ., ; Eichhorn et al ., ; Drobyshev et al ., ; Hacket‐Pain et al ., ; Ascoli et al ., ; Han & Kabeya, ; Vacchiano et al ., ). However, it is not clear which nutrients are most critical for the regenerative cycle (Crone & Rapp, ; Pearse et al ., ; Allen et al ., ).…”

Climatically controlled reproduction drives interannual growth variability in a temperate tree species

“…Indeed, our results show that a major source of uncertainty in the prediction of future changes in tree growth may originate from uncertainty in the response of tree reproductive effort to climate change (Ascoli et al . ; Pearse et al . ).…”

“…; Ascoli et al . ) may have effects on growth trends analogous to the influence of cyclic insect outbreaks (Peters et al . ).…”