Seasonal dynamics of manganese accumulation in European larch (Larix decidua Mill.), silver birch (Betula pendula Roth), and bilberry (Vaccinium myrtillus L.) over 10 years of monitoring

Distinct seasonality of nutrients in twigs and leaves of temperate trees

Seasonal variation of nutrient concentrations in different organs is an essential strategy for temperate trees to maintain growth and function. The seasonal variations and variability (i.e., seasonality) of leaf nutrient concentrations have been well documented, while the trends and magnitudes of such seasonal variations in other tree organs (e.g., twigs) and their associations with leaf nutrients remain poorly understood. We measured the concentrations of 10 nutrients (nitrogen, N; phosphorus, P; potassium, K; calcium, Ca; magnesium, Mg; iron, Fe; manganese, Mn; copper, Cu; zinc, Zn; boron, B) in twigs and leaves of four temperate tree species (i.e., Pinus tabuliformis, Ginkgo biloba, Cotinus coggygria, and Sophora japonica) to explore their seasonal variations and seasonality. Our results showed that macronutrient concentrations (N, P, K, Ca, and Mg) were significantly higher in leaves and micronutrient concentrations (Fe, Mn, Cu, and Zn) were significantly higher in twigs. Concentrations of P and K both showed a negative seasonal covariation between twigs and leaves, while Ca, Fe, Mn, Cu, Zn, and B showed an opposite relationship. Compared with mobile nutrients, nonmobile nutrients exhibited significantly greater seasonality in the leaves but there were no such differences in twigs. The seasonality of nutrient concentrations in twigs was significantly stronger than in leaves and they were positively correlated. Additionally, nutrients with higher physiological requirements in leaves showed weaker seasonality, confirming the hypothesis of seasonal stability of high-demand nutrients, while such relationships were not statistically significant for twigs. This study demonstrates distinct seasonality of nutrients in twigs and leaves of temperate woody plants. These findings highlight that high-demand nutrients show stronger seasonal stability in leaves but not in twigs and uncover the seasonal coordination between twigs and leaves as a nutrient conservation strategy.

Assessing the seasonality of foliar nutrient concentrations in woody plants

Seasonal variations in foliar nutrient concentrations are an important strategy of plants to adapt to different climates and availabilities of soil nutrients. Gaps in our knowledge, however, remain in both the seasonality of the concentrations of multiple nutrients in plant leaves and their spatial pattern on a large scale. We compiled data on foliar concentrations of nine essential nutrients (N, P, K, Ca, Mg, Fe, Mn, Zn, and Cu) in woody plants in China and evaluated the characteristics and latitudinal patterns of their seasonal variability (i.e., seasonality). Foliar concentrations of mobile nutrients (N, P, K, and Zn) in deciduous broadleaf woody plants decreased significantly during the growing season, but nonmobile nutrients (Ca and Mn) continued to accumulate. In contrast, the foliar nutrient concentrations in evergreen broadleaves and conifers generally showed no significant seasonal trend. The seasonality of foliar nutrient concentration was weaker for the nutrients with higher foliar concentrations, supporting the hypothesis of seasonal stability of high-demand nutrients. The seasonality of foliar nutrient concentration was stronger for deciduous than evergreen plants, while the effect of plant phylogeny was not statistically significant. The seasonality of foliar N and P concentrations increased with latitude in the deciduous broadleaf woody plants, but evergreen plants showed no significant latitudinal trend. The spatial patterns of seasonality for foliar N and P concentrations were significantly explained by climate and foliar habit. These findings improve our understanding of the seasonality of plant foliar concentrations of multiple nutrients as a strategy to adapt to varying climatic conditions.

Element contents and their seasonal dynamics in leaves of alder Alnus glutinosa (L.) Gaertn

Alnus glutinosa is an actinorhizal plant that fixes N via actinomycetes. Compared to other trees, A. glutinosa is more resistant to environmental stress and able to uptake soil nutrients more easily. Alnus glutinosa grows well not only in natural stands but also in degraded environment or soil in need of restoration. Changes in the contents of selected macro-, micro-, and non-nutrient elements in the leaves of A. glutinosa during the vegetation season were monitored in the Ore Mountains (Czech Republic), an area affected by extreme air pollution in the past. Decreased foliar content of N, P, K, and Cu, and increased content of Ca, Mn, Zn, and Al were observed; the content of other elements (S, Mg, Pb, and Cd) varied during the growing season or remained constant. From the viewpoint of nutrition, the content of N, S, Ca, and Mg macroelements was adequate; concentrations of P and K were low. Excessive amounts of Mn and Zn were measured, and the level of Cu was good. Non-nutrient elements Pb and Cd were present at the background level, and the level of Al was high. N/P, N/Ca, N/Mg, and Ca/Mg ratios were balanced, S/N value showed the lack of S, and N/K ratio indicated low content of K, which caused also suboptimal K/Ca and K/Mg values. The P/Al ratio varied from balanced to lower values. The content of individual elements and monitored changes were influenced by the amount of elements in the soil, moisture conditions, foliage phenology, and altitude.

Factors controlling Mn and Zn contents in leaves of silver and downy birch in acidified soils of Central Europe and Norway

In Central European mountain forests, foliar element concentrations (FECs) of manganese (Mn) in silver birch (Betula pendula Roth) are occasionally approximately 5000 mg kg-1 and can represent stress for these plants. Factors controlling the Mn FECs in silver birch in Central Europe and downy birch (Betula pubescens Ehrh.) in Norway have not yet been fully deciphered. In this study, the Central European silver birch specimens were sampled in 2022. The samples were analysed by X-ray fluorescence spectroscopy. Norwegian data were obtained from the literature. Mn FECs are commonly negatively correlated with magnesium and, in certain areas, with potassium. Mn FECs are simultaneously elevated with zinc (Zn), likely because of soil acidification and anthropogenic emissions. Mn FECs in birch were previously thought to be related to altitude, which was assigned to (i) downslope washes of Mn or (ii) the historical load of acid emissions. The highest Mn FECs in silver birch were found in the Harz Mountains, Germany, and have been attributed to historical atmospheric contamination and the abundance of soils on felsic silicic rocks poorly buffering acid rains. The historical emission load from iron and steel production was hypothesised to be the cause of elevated Mn and Zn FECs in the Beskid Mountains, Czech Republic. Mn FECs in birch can be used to map historical soil acidification caused by industrial emissions. Zn FECs in birches can reflect soil contamination by this element.

Mobilisation of Cd, Mn, and Zn in floodplains by action of plants and its consequences for spreading historical contamination and fluvial geochemistry

Cadmium, Mn, and Zn are mobilised by plants commonly growing in floodplains, most notably willows (Salix) and alder (Alnus). These plants accumulate unwanted elements (Cd) or excessive element concentrations (Mn, Zn) in their foliage, thus introducing them into the food web and enriching them in floodplain surface by litterfall. In floodplain of the Litavka River in Czechia, contaminated by historical mining activities, up to 100 mg kg^-1 Cd and up to several thousand mg kg^-1 Mn and Zn are present in willow leaves in autumn, probably close maxima for sustainable plant growth. Willows and alders show seasonal growth of their foliar Mn and Zn. The willow leaves showed Cd/Zn larger than contaminated fluvisol of the Litavka River. Senesced willow leaves thus contribute to spread of risk elements from historically contaminated floodplains back to river water even without the bank erosion. Alders and willows alter geochemical cycles of Cd, Mn, and Zn in fluvial systems and increase Cd/Zn and Mn/Fe concentration ratios and Cd and Mn concentrations in fluvially transported particles relative to global geochemical averages as well as relative to floodplain sediments. Willows, in particular Salix fragilis L., S. aurita L, and S. cinerea L are particularly important "plant pumps". Other common floodplain plants, such as bird cherry (Prunus padus L.) and herbaceous plants (common nettle, Urtica dioica L. and grasses, Poaceae) do not contribute to those phenomena.