Does drought advance the onset of autumn leaf senescence in temperate deciduous forest trees?

Abstract

Abstract. Severe droughts are expected to become more frequent and persistent. However, their effect on autumn leaf senescence, a key process for deciduous trees and ecosystem functioning, is currently unclear. We hypothesized that (I) severe drought advances the onset of autumn leaf senescence in temperate deciduous trees and (II) tree species show different dynamics of autumn leaf senescence under drought. We tested these hypotheses using a manipulative experiment on beech saplings and 3 years of monitoring mature beech, birch and oak trees in Belgium. The autumn leaf senescence was derived from the seasonal pattern of the chlorophyll content index and the loss of canopy greenness using generalized additive models and piecewise linear regressions. Drought and associated heat stress and increased atmospheric aridity did not affect the onset of autumn leaf senescence in both saplings and mature trees, even if the saplings showed a high mortality and the mature trees an advanced loss of canopy greenness. We did not observe major differences among species. To synthesize, the timing of autumn leaf senescence appears conservative across years and species and even independent of drought, heat and increased atmospheric aridity. Therefore, to study autumn senescence and avoid confusion among studies, seasonal chlorophyll dynamics and loss of canopy greenness should be considered separately.

High-Resolution X-Ray Computed Tomography: A New Workflow for the Analysis of Xylogenesis and Intra-Seasonal Wood Biomass Production

“…The growing season 2019 (when the samples were collected) experienced a very intense drought in late spring-early summer. Also because of the water deficit accumulated during the very dry 2018, the soil in late springearly summer of 2019 was dry as never observed before in Belgium (Mariën et al, 2021). Therefore, wood formation in black pine might be sensitive to drought as in other conifer species (Andrianantenaina et al, 2019).…”

On the Below- and Aboveground Phenology in Deciduous Trees: Observing the Fine-Root Lifespan, Turnover Rate, and Phenology of Fagus sylvatica L., Quercus robur L., and Betula pendula Roth for Two Growing Seasons

“…and four birches (Betula pendula Roth) in the KS and four beeches and four oaks (Quercus robur L.) in the PB. The trees were chosen because their aboveground wood and leaf phenology have been extensively monitored since 2017 in the framework of the LEAF-FALL project [68][69][70][71][72][73]. As such, concurrent measurements allowed the integration of results on both the belowand aboveground phenology in deciduous trees.…”

“…When required, the data were gap-filled using measurements of the Royal Netherlands Meteorological Institute's (KNMI) meteorological station of Woensdrecht (The Netherlands). More information on the meteorological stations and the measurements methods can be found in the literature [71,74,75].…”

“…The blue, orange, red and green dots represent the volumetric soil water content at depth intervals of 0-5 cm, 5-20 cm, 20-40 cm and 40-80 cm, respectively. This figure is partly adapted after Mariën et al [71] and Mariën et al [73].…”

“…By accumulating the daily potential evapotranspiration minus the daily sum of the precipitation, we were then able to compute the daily rainfall deficit per hydrological year (i.e., starting from a zero deficit around the first of April) and using continuous computation (i.e., when accounting for the hydrological fraction in the wet period that does not contribute to building up ground water reserves). The period from 1901 to 2000 was used as a long-term reference [71,73]. .…”