Wood Anatomical Traits Reveal Different Structure of Peat Bog and Lowland Populations of Pinus sylvestris L. in the Carpathian Region

Balázs Palla,Krisztina Buczkó,Klára Cseke,Márta Ladányi,Mária Höhn

doi:10.3390/f12040494

Balázs Palla, Krisztina Buczkó + Show 3 more

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https://doi.org/10.3390/f12040494

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Abstract

Ecologically extreme habitats at a species’ distribution edges bear significance for biota under adverse climatic conditions and climate change. Range-edge populations adjust their functional traits to the special local ecological conditions, leading to increased intraspecific variability in their morpho-anatomical structure and, consequently, favor population survival in the absence of competitors. On the basis of wood anatomical traits, such as tracheid lumen area (CA), cell wall thickness (CWTrad), cell diameter-to-radial cell wall thickness ratio (CD/CWT), and the number of tracheids in the radial tracheid files (TNo), we investigated the xylem adjustment of Pinus sylvestris L. populations from six ecologically extreme habitats from the Eastern Carpathians and the Pannonian Basin. Results indicated significant differences among all studied sites in case of all wood anatomical traits as signs of the local adaptation of trees. Peat bog populations adapted their wood anatomical traits to the generally hydric, cool and anaerobic conditions of the peat bogs, exhibiting smaller CA and proportionally thick CWTrad to ensure the hydraulic safety of the stem, whereas, on the lowland site, trees were characterized by a more effective water-conducting system, developing larger CA with relatively thin CWTrad with lower carbon-per-conduit-costs at the expense of higher vulnerability to cavitation. Radial tree ring growth and TNo also differed markedly among sites, following the temperature and groundwater constraints of the habitats. Wood anatomical variability among tree rings and the corresponding short-term climate response of populations differed from the adaptive responses of the trees to the ecological characteristics of the habitat. In addition to the different phylogeographic origin evidenced in former studies, phenotypic differentiation by the habitat type of the studied populations linked to the variance in morpho-anatomical traits have contributed to the survival of the peripheral Scots pine populations at the species’ range margins.

Highlights

We aimed to (i) reveal wood anatomical trait variation of refugial Scots pine populations from the edaphically extreme habitats of the Carpathians and the Pannonian Basin; (ii) characterize the level of adaptive differentiation in these fragmented, peripheral populations; and (iii) outline seasonal/interannual climate variations reflected by the measured anatomical parameters
These fragmented populations in the southern margin of the natural range of the species grow in specific habitat types, such as peat bogs, dry rocky substrates or mixed forests sustaining on sandy soils and calcareous bedrock [1,20,21]
P. sylvestris in the studied peripheral peat bog populations (RPO, RSD, RLU, RMO) adapted their wood anatomical traits to ensure the hydraulic safety of the stem, whereas, on the sandy, lowland site (HFE), trees are building a more effective water-conducting system at the cost of higher vulnerability to cavitation

Summary

Introduction

Cold tolerant species are predicted to expand their area of distribution towards the cooler regions of the poleward latitudes or to upslope elevations, causing local extinctions and population contractions at the southern periphery. At the warmer range margins, populations of the cold tolerant species are expected to survive in small remnant habitats called refugia, where local conditions favor their persistence [2,3,4]. Species’ survival in refuge habitats are receiving increasing attention today, as they serve as safe havens to which biota can retreat and persist under adverse climatic conditions [6]. Sites with special local ecological characteristics where retreating populations are able to survive are considered as being cryptic refugia [5], and such habitats are important for being identified and conserved, as they mitigate global biodiversity loss [6,7].

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