Impact of microclimatic conditions and resource availability on spring and autumn phenology of temperate tree seedlings.

Yann Vitasse,Constantin M Zohner,Rungnapa Kaewthongrach,Barbara Moser,Frederik Baumgarten,Yongshuo H Fu,Manuel G Walde

doi:10.1111/nph.17606

Abstract

Summary Microclimatic effects (light, temperature) are often neglected in phenological studies and little information is known about the impact of resource availability (nutrient and water) on tree’s phenological cycles.Here we experimentally studied spring and autumn phenology in four temperate trees in response to changes in bud albedo (white‐painted vs black‐painted buds), light conditions (nonshaded vs c. 70% shaded), water availability (irrigated, control and reduced precipitation) and nutrients (low vs high availability).We found that higher bud albedo or shade delayed budburst (up to +12 d), indicating that temperature is sensed locally within each bud. Leaf senescence was delayed by high nutrient availability (up to +7 d) and shade conditions (up to +39 d) in all species, except oak. Autumn phenological responses to summer droughts depended on species, with a delay for cherry (+7 d) and an advance for beech (−7 d).The strong phenological effects of bud albedo and light exposure reveal an important role of microclimatic variation on phenology. In addition to the temperature and photoperiod effects, our results suggest a tight interplay between source and sink processes in regulating the end of the seasonal vegetation cycle, which can be largely influenced by resource availability (light, water and nutrients).

Highlights

The phenological responses of plants to environmental cues play a prominent role in shaping species’ distribution ranges (Chuine & Beaubien, 2001; Korner et al, 2016) and Earth’s climate (Richardson et al, 2013)
We aimed to address the following questions: (1) To what extent is leaf-out regulated by microclimatic conditions, that is does high bud albedo and shade delay leaf-out at the individual level? (2) Do source–sink feedbacks and/or stress responses explain the effects of nutrient availability, solar radiation and soil moisture on autumn leaf senescence? does elevated sink strength lead to delayed senescence, does increased light availability advance senescence, and how does water availability interact with these patterns? (3) Are the different responses among species related to their tolerance to drought or shade?
This study demonstrates the importance of microclimatic conditions, especially solar radiation, in regulating the timing of budburst in spring and leaf senescence in autumn

Summary

Introduction

The phenological responses of plants to environmental cues play a prominent role in shaping species’ distribution ranges (Chuine & Beaubien, 2001; Korner et al, 2016) and Earth’s climate (Richardson et al, 2013). A striking example is that simplistic spring phenology models that ignore chilling and photoperiod often perform compared with more complex phenological models that include these cues (Fu et al, 2012; Basler, 2016) This contrasts with numerous experimental observations of temperate and boreal perennial plants, which have long shown that chilling and photoperiod play a significant role in dormancy release and bud development This contrasts with numerous experimental observations of temperate and boreal perennial plants, which have long shown that chilling and photoperiod play a significant role in dormancy release and bud development (e.g. Coville, 1920; Wareing, 1953; Murray et al, 1989; Heide, 1993; Rousi & Pusenius, 2005; Vihera-Aarnio et al, 2006)

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