Soils and Nitrogen Nutrition of Plants in Alpine Ecosystems of the Northwest Caucasus under Long-Term Increase in Availa
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CULTURAL CHEMISTRY AND SOIL FERTILITY
Soils and Nitrogen Nutrition of Plants in Alpine Ecosystems of the Northwest Caucasus under Long-Term Increase in Availability of Biogenic Elements M. I. Makarova, *, V. G. Onipchenkoa, A. V. Tiunovb, T. I. Malyshevaa, and M. S. Kadulina aLomonosov
Moscow State University, Moscow, 119991 Russia Severtsov Institute of Ecology and Evolution, Moscow, 119071 Russia *e-mail: [email protected]
b
Received December 4, 2019; revised January 30, 2020; accepted March 30, 2020
Abstract—An experiment with the enrichment of acid organic-rich mountain-meadow soils (Umbric Leptosols) of alpine ecosystems with mineral nutrients has demonstrated that the contents of organic carbon, total nitrogen, and labile organic compounds are stable and tolerant towards long-term (20 years) application of mineral fertilizers. Only the following direct effects are well pronounced: an increase in the content of inorganic nitrogen and phosphorus after the application of corresponding fertilizers, as well as a rise in pH as a result of liming. Plants are more sensitive indicators of changes in the conditions of nitrogen nutrition. They are characterized by active absorption of additional nitrogen, and the isotopic composition of nitrogen in them becomes heavier. The degree of these effects depends on the initial nitrogen availability. In addition to these direct effects, changes in the nitrogen status of plants also reflect changes in the transformation of nitrogen-containing compounds in soil and in the nitrogen nutrition of plants taking place due to an increased availability of phosphorus and lower acidity under the most phosphorus-depleted and most acid conditions, respectively. These impacts lead to the mobilization of soil organic nitrogen and are likely to reduce the role of mycorrhiza in plant nitrogen nutrition. As a result, a heavier isotopic composition of nitrogen is formed in some plant species. Keywords: long-term fertilizer experiment, soil acidity, nitrogen, phosphorus, δ15N, symbiotic nitrogen fixation, mycorrhiza DOI: 10.1134/S1064229320080116
INTRODUCTION Nitrogen is the most important biogenic element; its deficit limits the productivity of many terrestrial ecosystems, including high-mountain ecosystems, in which large amounts of nitrogen are immobilized in soil organic matter, while the concentration of mineral compounds available for plant nutrition is low [22, 30]. High-mountain areas undergo increasing anthropogenic load: changes in climatic parameters; additional input of biogenic elements, including nitrogen; and transformation of the structure of phytocenoses [1, 9, 13, 17]. Such changes may result in the activation of organic matter mineralization and formation of a more open biogeochemical nitrogen cycle [9–11, 13]. Poorly studied and relatively slightly involved in anthropogenic activities high-mountain landscapes of the temperate zone with their specific nitrogen regime differing from that in other terrestrial ecosystems attract the attention of researchers [22, 30]. In addi
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