Congratulations to our Head of R&D, Dr. Boris Rewald, on the new publication "Biehl, J., Sandén, H., & Rewald, B. (2023). Contrasting effects of two hydrogels on biomass allocation, needle loss, and root growth of Picea abies seedlings under drought. Forest Ecology and Management, 538, 120970. "
To study the effect of two commercial hydrogels (Polyter and Stockosorb) on above and below ground growth of Picea abies seedlings during a ∼ 5-week drought period, they used rhizoboxes with non-uniform nutrient distribution and hydrogels to monitor root system development in a stratified soil. Biomass allocation, root morphology and root elongation rates were related to evapotranspiration rates.
Total plant biomass was significantly greater when plants were grown in Polyter amended soil (+16-17%) compared to the Stockosorb and control treatments. Dead needle mass was significantly greater in Stockosorb than in Polyter (+719%) and control (+274%). Root elongation was faster in both hydrogel treatments compared to the control during the first part of the drought period, but then ceased to follow the order Polyter > control > Stockosorb. Root morphological changes in relation to the hydrogels were limited.
The better performance of Polyter amended seedlings was related to a slow release of water from the hydrogel, whereas Stockosorb released the additional soil water content prematurely. The latter may have provided a "false sense of security" and the subsequent lack of acclimation responses early in the drought resulted in even more severe drought stress and needle loss in Stockosorb amended seedlings compared to the control. However, neither hydrogel resulted in preferential growth towards or away from the hydrogel, suggesting that roots did not perceive the hydrogel-bound water, nor did secondary compounds inhibit root growth. Deeper root system placement, and thus potential benefits for drought events at later growth stages, was not found as Polyter also had a strong positive effect on root growth in the fertile topsoil. As hydrogel amendments may differentially affect root system establishment and seedling vitality during drought, further studies in the field, e.g. using minirhizon camera systems or root corers, are urgently needed before large-scale applications to mitigate the effects of climate change on forest regeneration/restoration can take place.
Citation: Biehl, J., Sandén, H., & Rewald, B. (2023). Contrasting effects of two hydrogels on biomass allocation, needle loss, and root growth of Picea abies seedlings under drought. Forest Ecology and Management, 538, 120970. doi: 10.1016/j.foreco.2023.120970