Explaining the Atlas Cedar (Cedrus atlantica M.) dieback by studying Water relations of young plants subject to an edaphic drought

O Omari,Aadel Taoufik,S Bourekkadi,Zine El Abidine Abdenbi,Rochdi Atmane,J Abouchabaka,K Slimani

doi:10.1051/e3sconf/202123400100

O Omari, Aadel Taoufik + Show 5 more

Open Access

https://doi.org/10.1051/e3sconf/202123400100

Copy DOI

Abstract

Cedrus atlantica M. stands from the Middle Atlas Mountains in Morocco have been severely affected by dieback. The edaphic water deficit could be the cause that triggered this phenomenon leading to the mortality of dying trees. The objective of this work is to analyze the ecophysiological behavior of Atlas cedar seedlings subjected to an edaphic drought of progressive intensity. During the drying cycle, the relative moisture content of the substrate decreased significantly to reach 12.71% at the end of the test; 4.27% and 2.88% respectively for the basaltic, calcareous, and sandy substrate. The pre-dawn water potential reached very low values of -32.25, -37.38, and -39.50 bar at the end of the water drying cycle. The critical water potential varied between -36 and -39 bar depending on the type of substrate. The mean maximum stomatal conductance under favorable water conditions was of the order of 330 mmol/m2/s. It was reduced, due to drying, in proportion to the reduction in substrate moisture content. Atlas cedar maintains gas exchange under conditions of severe water stress but can be lethal with extreme and recurrent droughts. This behavior can explain the development of the phenomenon of cedar stand decline, which is more accentuated especially with adverse ecological conditions.

Highlights

Forest tree dieback has become quite common in many regions of the world [1,2,3,4,5]
Atlas cedar plants, subjected to a gradual and severe edaphic drought to the end of the dewatering test, showed drought tolerance behavior expressed by the continuation of their gas exchanges up to a critical water potential fairly negative of the order of -39 bars, -36 bars and -38 bars respectively on substrates basaltic, calcareous and sandy
The corresponding relative water contents recorded at the level of the culture substrate were very low: 12.71%; 4.27% and 2.88% on basaltic, calcareous and sandy substrate. This critical predawn water potential level corresponds to the threshold below which the survival of the plants is at stake determined are consistent with values published by other researchers

Summary

Introduction

Forest tree dieback has become quite common in many regions of the world [1,2,3,4,5]. The extent of the decline of the Atlas cedar in the Middle Atlas varied according to the ecological conditions of stands, including the type of substrate and aspects. It is rare in cedar on basalt exposed to the influences north-west, but more common on calcareous and calcareous substrates dolomitic, located on steep terrain and hot exposures [6, 9]. Repeated droughts associated with extremes local ecological conditions and human impact have been identified as the main causes of degradation of forest ecosystems and tree dieback, in the Mediterranean region [7, 8, 13, 14]. The impacts of climate change would be more accentuated in the region Mediterranean and Maghrebian [21, 22]

Objectives

Methods

Results

Discussion

Conclusion