Date published:

Belowground Secrets of Scandinavian Pines

Zadworny, M., Mucha, J., Bagniewska-Zadworna, A., Żytkowiak, R., Mąderek, E., Danusevičius, D., Oleksyn, J., Wyka, T.P. and McCormack, M.L. (2021), Higher biomass partitioning to absorptive roots improves needle nutrition but does not alleviate stomatal limitation of northern Scots pine. Global Change Biology 27: 3859-3869.

DOI: 10.1111/gcb.15668

To understand the geographic distribution of trees and the processes that control forest productivity, we need to study the mechanisms by which trees take up limited environmental resources and the ways in which they allocate those resources. Equally important are the modifications of those mechanisms induced by the local environments. Members of the AMU Laboratory of General Botany participated in a research program run by Polish Academy of Sciences Institute of Dendrology in Kórnik that focused on studying traits controlling resource economy in Scots pine, a widely distributed tree with geographic range spanning temperate and subarctic areas. The team of scientists travelled between southern Poland and northern Scandinavia, collecting root and needle samples from natural stands of Scots pine. They also sampled pines growing in a so-called 'provenance trial' in Lithuania, where pines of different origins and adapted to different climates are grown in a common environment.

Research has shown that in the cool, northern climatic zone, where soils have low nutrient contents, pine roots are modified in a manner that increases their absorptive area. Furthermore, when northern pines are grown on a fertile site in the temperate climate, they not only retain this root structure, but also show elevated contents of mineral nutrients, nitrogen and phosphorus, in their needles, even exceeding the levels found in local pines. This evolutionary specialization of roots allows pines growing in nutrient-poor soils of the Far North to achieve viable nutrient levels and survive under those adverse conditions. Researchers also reported a surprising finding: the level of long term water deficit in needles measured by stable carbon isotope (13C) in the provenance trial was not related to the absorptive root structure. This shows that a higher absorptive area, while increasing nutrient uptake capacity, may not necessarily increase water uptake.

According to predictions, the subarctic regions will be strongly affected by the climate warming. Whereas higher temperatures are generally conducive to tree growth, they may be accompanied by drought that will restrict growth, especially that roots in the northern pines are relatively shallow. This adverse effect of climate warming on pine growth may be mitigated to some extent by transfer of new genes from more southerly pine population through seeds or pollen. Arrival of these genes will allow a gradual evolutionary adaptation of the northern pines to the new conditions. Studies combining field sampling with provanance trials, such as one reported in the Global Change Biology article, not only help to uncover the various adaptive mechanisms in trees but they also allow predictions of how trees will respond to climate changes.