Transpiration of silver Fir (Abies alba mill.) during and after drought in relation to soil properties in a Mediterranean mountain area

Abstract

International audience& Context Silver fir is declining and dying at its southern margin on the Mediterranean area, where climate is expected to be warmer and drier. At a regional scale, silver fir seems to be vulnerable to drought, and at a forest stand scale, tree death seems to be distributed according to soil water availability. & Aim To understand the vulnerability of silver fir to drought, factors involved in the regulation of transpiration were assessed with respect to soil properties in order to document the spatial distribution of death rates. & Methods Soil properties were characterized by electric re-sistivity measurements. Sap flow density and predawn needle water potential were recorded on sampled trees during several years, and crown specific transpiration was estimated. In addition, the vulnerability of coarse roots and branches to cavitation was quantified. & Results and conclusion Trees growing on soils with a large water storage capacity were the most vulnerable to drought induced soil water deficits. Transpiration was down-regulated as soon as predawn water potential decreased. The vulnera-bility to cavitation was low, which protected the trees from run-away xylem embolism. Severe soil water deficits led to a rapid decrease of transpiration, which was still visible the following year. The drop-off in transpiration was mainly due to inner sap flow that almost ceased after the drought on all monitored trees. Our results suggest that root dynamic and the ability of roots to take up water were modified by soil water deficit over several years. Such a regulation scheme needs to be better documented and included in models to address silver fir forest responses to drought

In situ marker‐based assessment of leaf trait evolutionary potential in a marginal European beech population

“…With this study, we showed within a rear edge population that the genetic basis of the phenotypic variation of ecologically important traits was substantial. Considering that the studied population experiments spatially heterogeneous water resources due to fine‐scale soil variations (Nourtier et al ., ), we can expect strong environmental variances for the studied traits. Thus, detecting a significant genetic basis suggests that the genetic diversity of the studied population is strong enough to be detected despite the environmental variance.…”

“…In this study, we focused on an elevation range of 987–1048 m. Therefore, the focal population was at the lower limit of the local species’ distribution. Regarding the ecological conditions on Mont Ventoux, the bedrock is calcareous with highly variable soil depth and high content in coarse elements (Nourtier et al ., ). The climate varies along elevation, but in the study site it is Mediterranean, that is characterized by strong summer droughts, with rainfalls mostly occurring in spring and autumn (Cailleret & Davi, ).…”

How do functional traits syndromes covary with growth and reproductive performance in a water‐stressed population of Fagus sylvatica?

“…high water use efficiency, high leaf mass per area and low water content, which is expected to optimize the use of available water resources and would allow copying with the strong summer droughts. Micro‐site conditions such as soil spatial heterogeneity (Nourtier et al ) could contribute to the variation in water availability, with trees on deep soils coming with earliest leaf unfolding and higher LWC and trees on shallow soils coming with higher LMA and WUE. Another hypothesis is that phenology itself alters the leaf morphological traits.…”

Drought-induced decline and mortality of silver fir differ among three sites in Southern France

“…Inter-annual variability in radial growth was primarily explained by water availability during the vegetation period (Cailleret and Davi 2011). These results can be explained by a high vulnerability to drought-induced cavitation, which is counterbalanced by a rapid and complete stomatal closure when soil water potential decreases (Nourtier et al 2012) and by an inhibition of cell division and enlargement (Zweifel et al 2006). Moreover, a lack of water during summer also negatively impacts the growth of the following years by reducing both the quantity of carbohydrates stored in the tree and the fine root turnover, and by inducing needle loss (Bréda et al 2006).…”

“…Indeed, the optimised neighbouring radius used for the determination of competitors ranged between 9 to 15 m, which is quite high compared with the range 2-5 m found by Linares et al (2009) on A. pinsapo using Δ 13 C wood data. As silver fir of Mont Ventoux exhibits an average crown projection diameter of approximately 5 m (Nourtier et al 2012), the overlap rate can be neglected.…”