The conifer forests, relics of extinct civilizations, silent witnesses of the planets’ evolution, have changed the face of continents over millions of years and transformed the ancient arid soils into the fertile lands we know today. Tree species experienced a continuous and sustainable development under the influence of environmental factors to a point that nowadays are threatened by forecasted drought episodes for this century. 

Among all tree species that can be found in Europe’s forests, one of them seems to have a special aura. Rising majestically from other species besides which it grows, Norway spruce suggests to any viewer, even untrained, a sense of greatness and respect. Undoubtedly, spruce forests can be considered the green treasure of our continent, a wealth we still own and without which European forestry would be poorer.

Effects of temperature and precipitation shift in this century on European forests should imply a wide concerning on forestry managers and researchers in order to identify suitable countermeasures to fight the predictive economic and environmental losses.

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According to Hanewinkel et al. (2013), conifers and especially spruce are considered to be the most threatened tree species (a mean of more than 20% drop for lands occupied by spruce in 2100). Based on this, new strategies and measures need to be taken in consideration for minimizing the expected damages. Europe’s spruce reforestation policies should be strongly related with a recent concept regarding the species survival and evolution, namely “Adaptive Forest Management”. Bolte et al. (2009) suggest the “active adaptation” strategy as suitable for stands transformation by replacing sensitive populations or tree species with others which could potentially respond better to possible climate changes during their life development.

A study performed by Șchiop et al. (2017), published in the scientific journal Trees: Structure and Function, on Romanian seedling populations of Norway spruce originating from Carpathian Mountains stands located at different elevations (230-1650m), was aimed to identify reliable water stress biomarkers in this species, which may be eventually used to select populations responding better to forecasted drought events.

The study quantified seed germination indices under osmotic stress and the most common metabolites in Norway spruce seedlings as physiological response to severe drought stress. The general reactions to water stress treatment included, among others, a decrease in water content percentage, photosynthetic damages expressed in chlorophyll a and b reductions, osmolyte (proline, total soluble sugars) and non-enzymatic antioxidants (total phenolic compounds, total flavonoids) accumulation, opposite variation patterns of ion content levels in roots and needles.

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The levels of analyzed parameters varied among populations, but the results pointed out that the decrease in needle water content, degradation of chlorophylls and the increase of proline levels could be employed as a battery of biomarkers for an early indication of water stress in this plants because of their degree of linear reduction or increase among all populations. Furthermore, two of the populations under study developed a different response to water stress than the other populations, indicating lower damages caused by this type of stress, both on germination (osmotic treatment) and seedling (water stress treatment) level. As a result, this Norway spruce populations could be used with a higher success in reforestation programs in order to minimize the drought effects on early growth of seedlings on reforestation sites from Romania (For more information regarding which Carpathian Norway spruce populations were less damaged by drought you can visit:  https://link.springer.com/article/10.1007/s00468-017-1563-1 ).

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In addition, the overall research also highlighted for the first time in this species the ion transport mechanism in Norway spruce seedlings as a response to water stress, which included K⁺ and Na⁺ ion uptake in roots and an exclusion of this ions on needle level, as the corresponding K:Na ratios are increasing in roots and decreasing in needles as a result of water stress exposure (For more data you can visit the Romanian abstract of the full study at: http://www.usamvcluj.ro/files/teze/2015/schiop.pdf )

Reforestation programs on the continent are using conifer seedlings originating in the certified seed stands across Romania and Europe. The previous study points out to the opportunity of starting a  European program of  screening those populations that could respond better to drought, for each conifer species, using biochemical markers, which would be a major step forward in proper use of seedling material on reforestation sites and would allow a better chance for future stands development.

AUTHOR OF THE POST:

Sorin T. Șchiop

Forestry engineer working in a Romanian forest district. He has a PhD in Genetics and Plant Breeding, with most of the research conducted at the Institute for Plant Molecular and Cellular Biology, Polytechnic University of Valencia, Spain. His expertise includes genetic diversity and biochemical response of Norway spruce seedlings to salt and drought stress, greenhouse and nursery production of conifer seedlings (seed and grafting), forestry management.

Cover photo: Norway spruce seedling nursery in Albac, Romania. Photo credit: Sorin T. Șchiop

References:

1. Bolte A, Ammer C, Löf M, Madse P, Nabuurs GJ, Schall P, Spathelf P, Rock J (2009). Adaptive forest management in central Europe: Climate change impacts, strategies and integrative concept. Scandinavian Journal of Forest Research 24(6):473-482.
2. Hanewinkel M, Cullmann DA, Schelhaas MJ, Nabuurs GJ, Zimmermann NE (2013). Climate change may cause severe loss in the economic value of European forest land. Nature Climate Change 3:203-207.
3. Șchiop ST (2015). Genetic diversity and biomarkers of drought and salt stress in several Norway spuce (Picea abies [L.] Karst.) populations. Phd Thesis, University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, Romania – Polytechnic University of Valencia, Spain.
4. Șchiop ST, Al Hassan M, Sestraș AF, Boscaiu M, Sestraș RE, Vicente O (2017). Biochemical responses to drought, at the seedling stage, of several Romanian Carpathian populations of Norway spruce (Picea abies L. Karst). Trees, DOI10.1007/s00468-017-1563-1.