Effects of Provenance, Growing Site, and Growth on Quercus robur Wood Anatomy and Density in a 12-Year-Old Provenance Trial

Abstract

Vessels are responsible for an efficient and safe water transport in angiosperm xylem. Whereas large vessels efficiently conduct the bulk of water, small vessels might be important under drought stress or after winter when large vessels are embolized. Wood anatomy can adjust to the environment by plastic adaptation, but is also modified by genetic selection, which can be driven by climate or other factors. To distinguish between plastic and genetic components on wood anatomy, we used a Quercus robur trial where trees from ten Central European provenances were planted in three locations in Austria along a rainfall gradient. Because wood anatomy also adjusts to tree size and in ring-porous species, the vessel size depends on the amount of latewood and thereby ring width, we included tree size and ring width in the analysis. We found that the trees’ provenance had a significant effect on average vessel area (VA), theoretical specific hydraulic conductivity (Ks), and the vessel fraction (VF), but correlations with annual rainfall of provenances were at best weak. The trial site had a strong effect on growth (ring width, RW), which increased from the driest to the wettest site and wood density (WD), which increased from wet to dry sites. Significant site x provenance interactions were seen only for WD. Surprisingly, the drier site had higher VA, higher VF, and higher Ks. This, however, is mainly a result of greater RW and thus a greater proportion of latewood in the wetter forest. The average size of vessels > 70 μm diameter increased with rainfall. We argue that Ks, which is measured per cross-sectional area, is not an ideal parameter to compare the capacity of ring-porous trees to supply leaves with water. Small vessels (<70 μm) on average contributed only 1.4% to Ks, and we found no evidence that their number or size was adaptive to aridity. RW and tree size had strong effect on all vessel parameters, likely via the greater proportion of latewood in wide rings. This should be accounted for when searching for wood anatomical adaptations to the environment.

Impact of Environmental Conditions on Wood Anatomical Traits of Green Alder (Alnus alnobetula) at the Alpine Treeline

“…The number of vessels per size class and wood surface area (Figure 4b) showed a lower absolute number of small and midsize vessels (up to 1200 µm 2 ) at the dry S-site, which is in accordance with the significantly lower VD and TCA at the S-site. On the contrary, an increase in VD and TCA under drought conditions has been reported in several studies [21,58,77]. However, Arnic et al [21] and Giagli et al [22] pointed out that drier summer conditions resulted in narrower annual rings and, consequently, higher VD and TCA.…”

“…Intraspecific studies provide insights into the impact of environmental factors on speciesspecific anatomical traits, disentangling genotypic and environmental effects contributing to xylem development is a difficult task. There is evidence that provenances can have more impact on xylem anatomy than environmental conditions [58][59][60]. Therefore, anatomical variations in plants growing at faraway sites or along wide-ranging environmental gradients may result from genetic variations.…”

“…However, tracheid enlargement might be based on turgor control in gymnosperms [66], while in more complex angiosperms, cell differentiation is probably actively regulated by endogen mechanisms rather than being a result of passive processes [76]. Anatomical traits are often under strong genetic control [58,73] suggesting species-specific adaptations to environmental impacts. In beech, for example, like in our study, no change in MVA under drought was detected [22,77,78].…”

“…However, Arnic et al [21] and Giagli et al [22] pointed out that drier summer conditions resulted in narrower annual rings and, consequently, higher VD and TCA. Environmental and provenance effects on anatomical traits often result from stem height and ring width [58]. In beech, VD was positively related to the above-ground biomass and increased with tree height [77].…”

The anatomical structure of the root, stem, and branch of Gyrinops versteegii trees from different growing sites

“…Furthermore, Chaabouni (2014) stated that different growing sites could affect the wood characteristics because of the different environmental conditions such as temperature, light intensity, and elevated CO2 levels. In the previous study, Hietz et al (2022) reported that different growing sites affect the vessel area, vessel fraction, and wood density of Quercus robur L. from Austria (Weyerburg, Wels, and Weistrach). This is also supported by Arnič et al (2021), where vessel area, vessel density, and tree ring width of Fagus sylvatica L. significantly differ among the trees from three selected sites in Slovenia.…”