Temporal dynamics, drivers, and components of soil respiration in urban forest ecosystems

Abstract

The objective of the study was to estimate the seasonal dynamics, the contribution of roots, litter, and soil microorganisms, as well as the primary drivers (soil moisture and temperature) of soil respiration (Rs) in urban forest ecosystems. Trenching and litter exclusion methods were used to distinguish root-derived (Rr) and litter-derived respiration (Rl) in soils of the Lomonosov Moscow State University (LMSU) Botanical Garden Arboretum, planted with Picea obovata (spruce) and Carpinus betulus (hornbeam). Measurements were taken every 1–2 weeks year round, as well as moisture (Θ10) and temperature (T10) of upper soil horizons (top 10 cm). The major factors affecting Rs were T10 throughout the year and Θ10 in summer. The results indicate that the contribution of Rr to Rs during the growing season on average for the spruce plantation was 34%, and for the hornbeam plantation was 38%. Our results indicated that trenching might significantly increase soil moisture, which could confound the results. The contribution of Rl to Rs on average during a year for the spruce plantation was 27%, and for the hornbeam plantation was 18%. Our data indicated a decrease in basal respiration due to litter and root exclusion in the hornbeam plantation. Year-round experiments have revealed that Rs, its temporal dynamics and drivers, as well as the contribution of individual components (roots, litter) are similar to the data obtained for natural forests. Thus, any climatic changes associated with urban development will affect the values of soil respiration similarly to natural forests. Also, the value of Rs will be influenced by manipulations carried out in urban environments, such as litter removal, the replacement of trees with lawns, and watering. Additionally, our data suggest the possibility of using such urban ecosystems as objects for research related to the carbon cycle.