Changes in Watering Frequency Stimulate Differentiated Adaptive Responses among Seedlings of Different Beech Populations

Georgios Varsamis,Ioannis Takos,Theodora Merou,Panayiotis G Dimitrakopoulos,Katerina Tseniklidou,Aristotelis C Papageorgiou,George C Adamidis

doi:10.3390/biology11020306

Abstract

Simple SummaryFuture precipitation changes are expected to affect plant populations’ adaptive responses. In southern Europe, annual precipitation is expected to decline and become unpredictable with occasional extreme rainfall events. Although there are many studies investigating water deficit effects in beech populations, they mainly refer to water withholding and rewatering or limited watering for prolonged periods. There is a lack of information considering the effect of simulated changes in monthly precipitation distribution on plants. In our study, we aimed to elucidate whether simulated distribution differences in monthly precipitation, expected to prevail in 2050, affects the response of various adaptive traits in beech seedlings originating from sites with contrasting climatic conditions. We found significant population differences according to watering interactions in most of the stem anatomical traits, but only for leaf circularity regarding the morphological traits. Our results indicate that beech populations in the southernmost region of their European distribution may demonstrate high variability in adaptive responses towards climate change conditions.Seasonality, rather than annual precipitation levels, is expected to affect the adaptive responses of plant populations under future climate change. To estimate adaptive traits’ variation, we conducted a common garden experiment with two beech populations from contrasting climatic origins (Evros with longer drought intervals during summer and higher precipitation seasonality, and Drama representing a more temperate ecosystem). We simulated two different watering treatments (frequent vs. non-frequent) on beech seedlings, according to predicted monthly precipitation levels expected to prevail in 2050 by the CSIRO MK3.6 SRESA1B model, considering as reference area a natural beech stand in Mt. Rodopi, Greece. A series of morphological and stem anatomical traits were measured. Seedling survival was greater for the Evros population compared to that of Drama under non-frequent watering, while no difference in survival was detected under frequent watering. Leaf morphological traits were not generally affected by watering frequency except for leaf circularity, which was found to be lower under non-frequent watering for both populations. Stomata density in leaves was found to be higher in the Evros population and lower in the Drama population under non-frequent watering than frequent. Stem anatomical traits were higher under non-frequent watering for Evros but lower for the Drama population. Multivariate analyses clearly discriminated populations under non-frequent rather than frequent watering, indicating genetic adaptation to the population’s environment of origin.

Highlights

The ongoing climate change is expected to cause prolonged drought periods and changes in seasonal precipitation patterns across the Mediterranean basin, having profound effects on range expansion, adaptive potential and survival dynamics of wild plant populations [1,2]
One of the plant species that are expected to be mostly affected by climate change is the European beech (Fagus sylvatica L.), a dominant forest tree species in Europe that is considered sensitive to extended drought summers [3,5,6,7,8,9,10,11]
The percentage of survived seedlings differed between populations under non-frequent watering

Summary

Introduction

The ongoing climate change is expected to cause prolonged drought periods and changes in seasonal precipitation patterns across the Mediterranean basin, having profound effects on range expansion, adaptive potential and survival dynamics of wild plant populations [1,2]. During summers with extreme drought events (e.g., 2003 and 2018), most European beech populations were negatively affected [11,13], but the ones growing in Greece were, interestingly, less affected during the summer drought of 2003 [14]. This indicates the existence of intra-specific variation in adaptive traits, defining potential alternative survival strategies among populations growing under different environmental conditions [15,16,17,18,19]

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