Long-term dynamics of Collembola in a pine forest ecosystem

Biomonitoring data on soil Collembola collected over a six year period (1992-1997) in Scots pine (Pinus sylvestris L.) forest in the Northern Vidzeme Biosphere Reserve, northern Latvia, are analysed. Monitoring was conducted in three plots: young (30-40 years), middle-aged (50-70 years), and old (150-200 years) pine stands. Sampling was performed once a year, in late August or early September, according to a systematic sampling scheme. One hundred soil cores (5 cm²× 10 cm) were taken within each plot every year, Collembola were extracted from the cores by using a modified high gradient extractor. During the monitoring period, there was a tendency of climate warming between 1992 and 1997. A decrease of precipitation resulted in decrease of soil moisture in the studied plots. Species richness S and Shannon's index H' within almost all plots showed significant linear decreasing trends, while no trends were found in total density of Collembola. Several species (Sphaeridia pumilis, Sminthurinus aureus, Pseudanurophorus binoculatus, Anurophorus septentrionalis, Arrhopalites spp.) decreased in density during the period of investigation. The possible reasons for the changes in the collembolan community are discussed.