Drought Effects on Early Growth and Mortality of Three Oak Species in the Upper Rhine Valley

Abstract

Pedunculate oak and sessile oak are important natural species in the Upper Rhine Valley. The increasing mortality of these oak species has been observed since the 1980s in this region, mainly due to severe droughts. Turkey oak is known to be highly productive and drought-resistant. The goal of this article is therefore to investigate the adaptability to drought of these three young oak species growing at the same site, and to show to what extent Turkey oak can be substituted for these native oak species. Stand measurements and retrospective analyses of radial growth were performed within the framework of the eight-year-old “Mooswald” afforestation experiment in order to determine stand volume, mortality and resistance/resilience to drought for each species. Turkey oak shows significantly higher stand volume and significantly lower mortality than sessile oak. Values of these two parameters for Turkey oak and sessile oak are not significantly different from those of pedunculate oak. However, Turkey oak is not more resistant to drought than the other oak species. Sessile oak has the highest mortality and the smallest stand volume, while pedunculate oak is the least resilient to drought. These results are only a trend that must be confirmed in older stand stages and investigation in young stands must continue, supported by better monitoring and improved tools.