Different drought sensitivity traits of young sessile oak (Quercus petraea (Matt.) Liebl.) and Turkey oak (Quercus cerris L.) stands along a precipitation gradient in Hungary

This paper analyses the drought-induced growth responses of two ecologically and economically important broadleaf tree species, namely sessile oak (Quercus petraea (Matt.) Liebl.) and Turkey oak (Quercus cerris L.) in south-western Hungary. Although both have been described as drought-tolerant species, our understanding of their growth responses to drought extremes is still limited. Forest stands of younger ages of the target species were sampled along a precipitation gradient under similar soil conditions. 136 tree-ring samples were used to build six species- and site-specific chronologies. We also applied several dendroecological metrics to assess the drought sensitivity of the species. Water deficit was estimated by various drought indices including the soil water-budget based water stress index. The results indicated a strong dependency of annual tree-ring width of both species on the water availability of summer months in the actual year of ring formation. However, we found markedly different reaction of the two species against drought conditions. Turkey oak responded more sensitively to droughts than sessile oak revealed by the significantly lower resistance and higher recovery potential of this species. The more plastic behaviour of Turkey oak could be also perceived by the higher sensitivity of its tree-ring chronologies and by the observed relationship between resistance and recovery that showed a closer fit to the line of full resilience in case of this species. Regarding the precipitation gradient, a linearly proportional increase of growth reduction with rising water stress was found for Turkey oak while the growth response of sessile oak decreased considerably with increasing aridity indicating lower growth plasticity of sessile oak to droughts there. Based on our findings it seems that Turkey oak copes better with droughts than sessile oak and may gain competitive advantages under the projected climate change in Hungary.

Automated summary

This study examined the drought-induced growth responses of sessile oak and Turkey oak in south-western Hungary. The results revealed that Turkey oak showed higher sensitivity to drought, lower resistance, and higher recovery potential compared to sessile oak. Additionally, Turkey oak exhibited a linearly proportional increase in growth reduction with rising water stress, while sessile oak's growth response decreased considerably with increasing aridity, indicating its lower growth plasticity to droughts.