Elizaveta Nikolaevna Derevenets

Due to the need to develop technologies for reducing carbon dioxide emissions and increasing the C-absorption
capacity of natural and anthropogenic ecosystems, the possibility of using mineral fertilizers to regulate microbial
respiration and CO2 emissions from urban lawn soils was evaluated. Th e studies were carried out on the territory of
the Botanical Garden of Moscow State University on the Lenin Hills in a small-plot experiment with the fractional
application of four types of complex fertilizers (NPKS 27:6:6:2, NPKS 21:10:10:2, NPK 15:15:15 and NPK 18:18:18
+ 3 MgO + trace elements (TE)) at doses of 60 and 120 kg N ha-1 during the growing season. Th e carbon content
of microbial biomass (Cmic) using substrate-induced respiration was studied, the basal respiration (BR) of soils was
estimated, and the emission of CO2 from soils using closed static chambers was determined. Тhe Cmic content in the
soil of the control plot in the summer period varied within 1300–1450 μg·g-1. Th e application of NPKS 21:10:10:2
and NPK 18:18:18 + 3 MgO + TE at a low dose increased the Cmic content by 12–35% for two weeks, then it decreased.
Th e application of all fertilizers for a short period increased basal respiration of soils and CO2 emission,
maximum on the 6th day. After two weeks, the increase in the intensity of BR and CO2 emission decreased or it
reached the control values (1,5 μg C-CO2·g-1·h-1 and 500 mg·CO2 ·m-2·h-1 respectively) or less. In the short term,
the lowest intensity of CO2 emission and a surge in basal respiration, along with an increase in microbial biomass,
were observed with the addition of fertilizer NPKS 21:10:10:2. The greatest change in the functioning of the soil
microbial community, revealed by the maximum qCO2, occurred with the introduction of NPKS 27:6:6:2. The dynamics
of CO2 emission from the soils of the small-plot experiment from April to October correlated with the soil
temperature (rS = 0.66, p<0.05, n=135). In all periods of the study, the minimum CO2 emissions were noted for the
plot with NPKS 21:10:10:2 fertilizer.

Microbial production and CO2 emission in Albic Retisol (Loamic) and Albic Retisol (Aric, Loamic) of Lomonosov Moscow State University carbon polygon «Chashnikovo»≫ in the Moscow region were studied during the peak of vegetation activity. The object represents monitoring sites in two natural ecosystems (secondary spruce forest and mixed-grass meadow) and in two agroecosystems (perennial grasses and bare fallow). The soils differed in their stocks
of organic matter carbon (Corg), microbial carbon (Cmic), and potentially mineralizable carbon (Cpm). The highest values of microbial indicators and carbon content were observed in the upper 30 cm with a maximum in the upper 10 cm. Corg stocks in the 0–30 cm layer were 1.1–1.3 times higher in agricultural soils (72.7–75.6 t ha-1) compared to natural ones (59.4–65.0 tha-1). The contribution of Cmic stocks to Corg stocks in meadow soils and agricultural soils under perennial grasses (1.8 and 1.4%) was higher than in forest soils and soils under bare fallow. Сpm stocks in natural soils (1.34 and 0.97 tha-1 for a layer of 0–10 cm) were 1.3–2.3 times greater than in agricultural soils, but the intensity of mineralization of organic matter in agricultural soils was 1.4–2.9 times lower than in soils of natural ecosystems. For ecosystems with similar vegetation, the influence of Сpm stocks on the amount of microbial CO2 production was shown; its proportional increase was noted. Maximum potential microbial CO2 production (4.8 gCm-2day-1 for the 0–10 cm layer and 10.5 gCm-2day-1 for the 0–30 cm layer), Cmic stocks (0.50 tha-1), as well as CO2 emission (11.09±0.29 gCm-2day-1) were characteristic of the soils of a dry meadow. In other ecosystems, CO2 production by microorganisms was lower by approximately 2 times. Since CO2 emission, in addition to microbial respiration, is also caused by the respiration of plant roots, its minimum values were observed in agricultural soils under bare fallow (5.01±1.43 gCm-2・day-1). CO2 emission from forest soils and agricultural soils under perennial grasses was statistically not significantly lower compared to the meadow.