Transformation of particle-size composition, structure, and density of soils upon urbopedogenesis is considered for Rostov agglomeration. Various soils are compared by horizons. It is found that the...

Constructed Technosols are an important component of urban green infrastructure, whose role in the carbon balance of urban ecosystems remains poorly studied. The dynamics of carbon stocks and CO₂ emission of soil structures depend on both bioclimatic conditions and the parameters of the construction: the substrates used and the composition and thickness of the layers. The carbon stock dynamics and CO₂ emission were studied on constructozems of different compositions at the Experimental Station for Study of Soil Constructions in the Botanical Garden of the Southern Federal University (Rostov-on-Don). The station consists of 15 sites representing five different variants of soil constructions made of substrates traditionally used for landscaping and beautification tasks in cities of the steppe zone. Haplic Chernozem of the automorphic position in the vicinity of the Experimental Station was studied as a background (reference) soil. Monitoring studies during two seasons (from September 2020 to December 2022) enabled us to compare the seasonal dynamics of organic and inorganic carbon contents and CO₂ emission for different soil constructions with the background. All constructions created on the basis of humus-accumulative horizons of chernozems demonstrated a pronounced dependence of CO₂ emission on the temperature of air (r = 0.76, 0.82, 0.76, and 0.49 for constructions 2, 3, 4, and 5, respectively, at p < 0.05) and of soil (r = 0.58, 0.74, 0.75, and 0.68 for constructions 2, 3, 4, and 5, respectively, at p < 0.05). The biomass stocks of lawn grasses growing on the constructions were determined, and a positive correlation between the CO₂ emission and the increase in the aboveground biomass was revealed: a moderate correlation for construction 2 (r = 0.48, p < 0.05), a pronounced correlation for constructions 3 and 4 (r = 0.5, p < 0.05; and r = 0.68, p < 0.05), and a strong correlation for construction 5 (r = 0.75, p < 0.05). The dynamics of the stocks of various forms of carbon in the first year of operation of the structures were studied. Based on the comparison of carbon fluxes and stocks, it is shown that lawn ecosystems at the early stages of constructozem development cannot be considered as net carbon stocks in the temperate continental climate of Rostov-on-Don.

The research aims to study the content of organic matter in typical chernozem, its distribution in the soil profile under herbaceous and wooden phytocenoses. Organic matter plays a key role in the functioning of soils and their stable performance of ecological functions, including – the protection function. This is particularly relevant in the growing urbanization. The research analysis includes 40 full-profile sections of migration-segregated chernozems (typical carbonate) laid on the upland soil of the Rostov agglomeration. We determined organic matter by high-temperature catalytic combustion on a TOC-L CPN Shimadzu in an SSM-5000A solid sample combustion unit. Based on the data obtained, we calculated the organic carbon reserves. Statistical analysis included the calculation of the Mann-Whitney U-test to consider significant differences in the samples of indicators under wooden and herbaceous phytocenoses and descriptive statistics. The research results showed the influence on the organic carbon content of such a widespread type of anthropogenic impact as planting trees in the steppe zone. Comparison of the total organic carbon content values in similar genetic horizons under herbaceous and wooden phytocenoses indicates the spatial heterogeneity of this indicator, associated primarily with the type of land use. The supply of humus for Rostov chernozems under herbaceous phytocenoses was assessed as low and under wooden phytocenoses – as average. In the one-meter layer of natural chernozems of the Rostov agglomeration, humus reserves are 387 t/ha, which corresponds to the average supply level. Thus, the park and recreational zone, where wooden vegetation grows, plays a special ecological role in the city as a place of accumulation of an increased amount of organic matter of natural origin compared to other soils of the Rostov agglomeration. Цель – исследование содержания органического вещества в черноземах обыкновенных, его распределение в профиле почв под травянистыми и древесными фитоценозами. Органическому веществу принадлежит ключевая роль в функционировании почв и стабильном выполнении ими экологических функций, в том числе – протекторной функции, что приобретает особую актуальность в условиях растущей урбанизации. Анализ включал 40 полнопрофильных разрезов черноземов миграционно-сегрегационных (обыкновенных карбонатных), заложенных на плакорах Ростовской агломерации. Определяли органическое вещество методом высокотемпературного каталитического сжигания на анализаторе углерода TOC-L CPN Shimadzu в приставке для сухих образцов SSM-5000A. По полученным данным рассчитывали запасы органического углерода. Статистический анализ включал расчет критерия Мана-Уитни, для учета достоверных различий в выборках показателей под древесными и травянистыми фитоценозами, а также описательную статистику. Результаты исследований показали влияние на содержание органического углерода такого распространенного вида антропогенного воздействия, как посадка деревьев в степной зоне. Сравнение величин содержания общего органического углерода в аналогичных генетических горизонтах под травянистыми и древесными фитоценозами указывает на пространственную неоднородность данного показателя, связанную, в первую очередь, с типом землепользования. Обеспеченность гумусом для чернозёмов Большого Ростова под травянистыми фитоценозами оценивается как низкая, а под древесными фитоценозами – как средняя. В метровой толще естественных черноземов Ростовской агломерации запасы гумуса составляют 387 т/га, что соответствует среднему уровню обеспеченности. Таким образом, парково-рекреационная зона, где произрастает древесная растительность, выполняет особую экологическую роль в городе, являясь местом аккумуляции повышенного количества органических веществ природного происхождения по сравнению с иными почвами Ростовской агломерации.