Variation in leaf flushing date influences autumnal senescence and next year’s flushing date in two temperate tree species

Abstract

Recent temperature increases have elicited strong phenological shifts in temperate tree species, with subsequent effects on photosynthesis. Here, we assess the impact of advanced leaf flushing in a winter warming experiment on the current year's senescence and next year's leaf flushing dates in two common tree species: Quercus robur L. and Fagus sylvatica L. Results suggest that earlier leaf flushing translated into earlier senescence, thereby partially offsetting the lengthening of the growing season. Moreover, saplings that were warmed in winter-spring 2009-2010 still exhibited earlier leaf flushing in 2011, even though the saplings had been exposed to similar ambient conditions for almost 1 y. Interestingly, for both species similar trends were found in mature trees using a long-term series of phenological records gathered from various locations in Europe. We hypothesize that this longterm legacy effect is related to an advancement of the endormancy phase (chilling phase) in response to the earlier autumnal senescence. Given the importance of phenology in plant and ecosystem functioning, and the prediction of more frequent extremely warm winters, our observations and postulated underlying mechanisms should be tested in other species.climate change | tree phenology | spring flushing | leaf senescence L eaf phenology of temperate trees has recently received particular attention because of its sensitivity to the ongoing climate change (1-3), and because of its crucial role in the forest ecosystem, water and carbon balances, and species distribution (4-6).A wide variety of methods, such as long-term phenological records (7), indirect measurements of ecosystem greening by remote sensing using satellites or webcam digital images (8-10), and modeling approaches (11-13), have been applied to monitor and study phenological changes. These different approaches, conducted at different spatial scales (from individual plants to biomes), have documented a clear advancement of leaf flushing in temperate climate zones and, to a lesser extent, a delay in leaf senescence (14,15). Furthermore, various temperature manipulation experiments have simulated the impact of future winter warming on leaf phenology and confirmed an advancement in the timing of leaf flushing in response to warming (16-18). However, the response of leaf flushing to climate warming is highly nonlinear (16,19,20), because trees also depend on cold temperatures to break bud dormancy (21-23). This chilling requirement may not (fully) be met in a warming climate, especially at the southern edges of species distribution ranges (5,24,25).Most previous phenological studies have focused on specific phenophases, but how a phenological change (e.g., advanced leaf flushing) affects subsequent phenological events is rarely investigated. Nonetheless, the annual growth cycle of boreal and temperate trees forms an integrated system, where one phenophase in the cycle can affect the subsequent phases (26, 27). Such carryover effects have already been detected in fruit and nu...

Alteration of the phenology of leaf senescence and fall in winter deciduous species by climate change: effects on nutrient proficiency

“…Leaf senescence advanced by 20 days in seedlings of F. sylvatica and Q. robur subjected to 6 ºC warmer temperatures during winter and before leaf flushing in early spring, which was attributed to a legacy of much earlier spring flushing in leaves of warmed saplings (Fu et al, 2014). The timing of leaf senescence was positively correlated with previous flushing dates in the long-term European phenological records of both species, indicating that even though recent environmental cues dominated the variability in the phenology of leaf senescence, they could not fully account for it, which led to the hypothesis that leaf senescence could be triggered by the sink limitation that indicates the accumulation of non-structural carbohydrates in the leaves.…”

Relationships between Wood Formation and Cambium Phenology on the Tibetan Plateau during 1960–2014

“…Thus, the timing of autumn senescence is not affected by the timing of spring phenology in the stem of trees over the study region (Table 1 and Figure 5). However, previous authors found that an earlier leaf flushing resulted in an earlier senescence in two tree species of pedunculate oak (Quercus robur L.) and European beech (Fagus sylvatica L.) in Belgium [22]. The timing of autumn senescence was related to the timing of spring bud-burst by using two decades of ground and satellite-based observations of temperate deciduous forest phenology in the northeastern US [23].…”

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

“…A change in the timing of one phase can potentially affect the timing of subsequent phases (Hänninen and Kramer 2007;Fu et al 2014). Hence, the environmental cues driving the timing of each phase are also indirectly involved in the timing of subsequent phases, as described in Fig.…”

“…However, scarce effort has been directed at modeling the induction of dormancy, which is tightly linked to leaf senescence and cold acclimation and, further, impacts spring phenophases. Another example is the partial dependence of leaf senescence on the timing of budburst (Fu et al 2014), which has not been implemented in models to date (but see Keenan and Richardson 2015). This situation indicates the need for a common framework that is representative of the cyclic nature of phenological events (Figs.…”