Assessment of Organic Matter Dynamics in the Litter of Urban Coniferous Stands Using Characteristics of Their Structural and Functional Organization: A Case Study in Moscow City

Properties of forest litter in the European larch stands planted in the Izmailovo Park specially protected natural area in Moscow were studied in two sites of 100–120-year-old larch plantations on the typical sandy loamy soddy eluvozems on sandy deposits underlain by moraine (Luvic Cambisols). One of the sites is the control and the other was subjected to human impacts typical of park areas as a result of recreation. A classification of litter structure and transformation characteristics is proposed to assess a stepwise change in organic matter corresponding to different periods of litter functioning. In seasonal dynamics, a uniform decrease in litter stock over the year is observed in control stands versus the disturbed plot, where the most significant decrease in stock is recorded in November–June. In the annual cycle, a considerable decrease in the stock of active fraction is observable in the annual cycle, suggesting an intensive biological turnover in the studied larch stands. The dynamics of the stocks of litter fractions are different. The recreational load in larch stands determines a decrease in the accumulation of litter organic matter and influences the dynamics of this process. A significant twofold decrease in litter thickness and stock during recreation is recorded and is accompanied by a significant simplification of the litter structure and changes in its typology, which is especially pronounced in the conditions of near-trunk spaces. The characteristics of structural and functional litter organization in larch stands are the informative criteria for the specific features of organic matter biogeochemical cycles appropriate for other types of tree stands both natural and urban.