Significant impact of allochthonous nutrient loads on microarthropods in forest soils

Aim of study: To investigate the impact of allochthonous material from piscivorous birds on forest soil microarthropod communities. Area of study: Six study zones in the Curonian Spit peninsula (western Lithuania) were designated in Pinus sylvestris stands with nesting sites of the great cormorants, taking into account the relief and the duration of the ornithogenic impact. Materials and methods: The total abundance of mites and Collembola and the species richness and diversity of Oribatida and Gamasina mites were assessed and compared. Main results: The abundance of Collembola, Tarsonemidae and Acaridae mites positively correlated with ornithogenic activity, while Oribatida and Gamasina mites decreased significantly. The structure of microarthropod communities was similar in most of the studied zones, except for the active nesting zone and the abandoned part of the colony on the dune slope. The greatest species richness of Oribatida and Gamasina was found in the unaffected forest in the dune hollow, whereas the lowest value was found in the active nesting area and in the abandoned part of the colony on the dune slope. Of the environmental parameters studied, soil pH (r = - 0.725) and tree layer (r = 0.827) were those most significantly related to the changes of microarthropod communities. Research highlights: We found that cormorant colonies have a strong impact on forest ecosystems and soil properties, leading to significant changes in soil microarthropod communities. Birds thus create a natural disturbance experiment that can help reveal the factors that determine the diversity and composition of natural microarthropod communities.