Experimental assessment of the contribution of plant root respiration to the emission of carbon dioxide from the soil

The contributions of root and microbial respiration to the total emission of CO2 from the surface of gray forest and soddy-podzolic soils were compared under laboratory and field conditions for the purpose of optimizing the field version of the substrate-induced respiration method. The magnification coefficients of respiration upon the addition of saccharose (k mic) were first determined under conditions maximally similar to the natural conditions. For this purpose, soil cleared from roots was put into nylon nets with a mesh size of 40 μm to prevent the penetration of roots into the nets. The nets with soil were left in the field for 7–10 days for the compaction of soil and the stabilization of microbial activity under natural conditions. Then, the values of k mic were determined in the root-free soil under field conditions or in the laboratory at the same temperature and water content. The contribution of root respiration as determined by the laboratory version of the substrate-induced respiration method (7–36%) was lower compared to two field versions of the method (27–60%). Root respiration varied in the range of 24–60% of the total CO2 emission from the soil surface in meadow ecosystems and in the range of 7–56% in forest ecosystems depending on the method and soil type.