Urbanization can negatively impact riparian forests, and their roles in providing ecosystem services. These include anthropogenic subsidies or resource alterations including nitrogen runoff or dumping lawn refuse. These human impacts can change forest structure by altering ground arthropod communities and forest functions like decomposition. A large proportion of riparian forest diversity is represented by invertebrate communities which play major roles as pollinators, soil aerators, decomposers, and prey for other species. Altered arthropod communities in urban areas can affect nutrient cycling and stream water chemistry with cascading effects.
This study investigates the effect of urban ground cover on arthropod abundance and community composition through litter manipulations. This experiment is conducted in Binghamton University’s Nature Area adjacent to an urban stream. Litter manipulation treatments included a control, litter removal, litter addition and urban grass-cutting addition. Within each experimental plot, we investigated the rates of decomposition of sugar maple and red oak leaves by collecting litterbags at four-month time intervals. We used a randomized block design for each of the 4 experimental treatments in 10 blocks over one year. We conducted field surveys of ground arthropods using pitfall traps and counted total abundances and identified ground arthropods to order and family levels.
After 12 months, we found that sugar maple decomposed faster than red oak (49% red oak, 55% sugar maple). Although not statistically significant, compared to the control, the litter removal treatment showed 5% higher decomposition for both oak and maple litter and the grass addition showed 3% and 5% higher decomposition for oak and maple, respectively. The increased resources by grass addition may have led to increased biological activities. The removal treatment could change the micro-environment of the decomposition.
The highest abundance of ground arthropods was found in June. There were no significant differences between treatment groups; however, there is a trend showing the highest abundance in the grass addition (100.3 ± 11.6) and lowest in the litter removal (64.0 ± 9.8) compared to the control (80.3 ± 8.4). All major groups were represented including spiders, beetles, ants, centipedes and millipedes, mites, and springtails. In June, differences between treatment groups were driven by springtail abundance. Results will be reported for all collection months. Studying arthropod communities and decomposition within these urban sites allows further understanding of how riparian forests function with urban resource subsidies.