Increasing air humidity – a climate trend predicted for northern latitudes – alters the chemical composition of stemwood in silver birch and hybrid aspen

Silver birch, Betula pendula Roth, is one of the most common trees in Europe. Due to its content of many biologically active substances, it has long been used in medicine and cosmetics, unlike the rare black birch, Betula obscura Kotula. The aim of the study was therefore to compare the antioxidant properties of extracts from the inner and outer bark layers of both birch trees towards the L929 line treated with acetaldehyde. Based on the lactate dehydrogenase test and the MTT test, 10 and 25% concentrations of extracts were selected for the antioxidant evaluation. All extracts at tested concentrations reduced the production of hydrogen peroxide, superoxide anion radical, and 25% extract decreased malonic aldehyde formation in acetaldehyde-treated cells. The chemical composition of bark extracts was accessed by IR and HPLC-PDA methods and surprisingly, revealed a high content of betulin and lupeol in the inner bark extract of B. obscura. Furthermore, IR analysis revealed differences in the chemical composition of the outer bark between black and silver birch extracts, indicating that black birch may be a valuable source of numerous biologically active substances. Further experiments are required to evaluate their potential against neuroinflammation, cancer, viral infections, as well as their usefulness in cosmetology.

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Carbon allocation in early successional tree species at elevated air humidity and different soil nitrogen sources

10.5194/egusphere-egu21-8217 ◽

2021 ◽

Author(s):

Marili Sell ◽

Ivika Ostonen ◽

Gristin Rohula-Okunev ◽

Azadeh Rezapour ◽

Priit Kupper

Keyword(s):

Biomass Allocation ◽

Tree Species ◽

Root Respiration ◽

Fine Root ◽

Silver Birch ◽

Organic Carbon Content ◽

Climate Change Scenarios ◽

Air Humidity ◽

Species Specific ◽

Exudation Rate

Global climate change scenarios predict increasing air temperature, enhanced precipitation and air humidity for Northern latitudes. We&#8239;investigated the effects of elevated air relative humidity (RH) and different inorganic nitrogen&#8239;sources&#8239;(NO3-, NH4+) on above- and belowground traits in different tree species, with particular emphasis on rhizodeposition rates. Silver birch, hybrid aspen and Scots pine saplings were grown in PERCIVAL growth chambers with stabile temperature, light intensity and two different air humidity conditions: moderate (mRH, 65% at day and 80% at night) and elevated (eRH, 80% at day and night). The collection of fine root exudates was conducted by a culture-based cuvette method and total organic carbon content was determined by Vario TOC analyser. Fine root respiration was measured with an infra-red gas analyser CIRAS 2.&#8239;&#160;We analysed species-specific biomass allocation, water and rhizodeposition fluxes, foliar and fine root traits in response to changing environmental conditions. The&#8239;eRH&#8239;significantly decreased the transpiration flux in all species. In birch the transpiration flux was also affected by the nitrogen source. The average carbon exudation rate for aspen, birch and pine varied from 2 to 3 &#8239;&#956;g&#8239;C g-1&#8239;day&#8239;-1. The exudation rates for deciduous tree species tended to increase at&#8239;eRH, while conversely decreased for coniferous trees (p=0.045), coinciding with the changes in biomass allocation.&#8239;C flux released by fine root respiration varied more than the fine root exudation, whereas the highest root respiration was found in silver birch and lowest in aspen. At eRH the above and belowground&#8239;biomass ratio in aspen increased, at the expense of decreased root biomass and root respiration.&#8239;&#160;Moreover,&#8239;eRH&#8239;significantly affected fine root morphology, whereas the response of specific root area was reverse for deciduous and coniferous tree species. However, fine roots with lower root tissue density had higher C exudation rate. Our findings underline the importance of considering species-specific differences by&#8239;elucidating tree&#8217;s&#8239;acclimation&#8239;to environmental factors and their&#8239;interactions.&#8239;&#8239;&#160;

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