Soil fauna community dynamics during soil thawing period in the subalpine and Alpine forests of Western China

The frequently changed temperature could have great effects on soil fauna community during soil thawing period in cold areas. Therefore, soil faunas were investigated in both the soil organic layer (OL) and mineral soil layer (ML) in the primary fir (Abies faxoniana) forest (PF), fir and birch (Betula albosinensis) mixed forest (MF) and secondary fir forest (SF) in the eastern Qinghai–Tibet Plateau every ten days between March 5 and April 25, 2009. Soil macrofauna was picked up by hand in the fields. Mesofauna was collected and separated from the soil samples by Baermann and Tullgren methods, respectively. The dominated species of macrofauna belongedto Coleoptera and Diptera at the early stage of soil thawing, and to Coleoptera, Diptera, Araneae and Hymenoptera at the later stage. However, the dominated species of mesofauna belonged to Nematode, Collembola, and Acari in the whole soil thawing. The density, number of taxa, and diversity index of soil fauna showed significant change with temperature fluctuations and reached an obvious peak when soil temperatures rising above 0°C. The density and number of taxa of macrofauna in both the OL and ML were the lowest on March 5 in the three forests, but the density of mesofauna in both the OL and ML was the highest on March 25, except for the ML in the PF. These results implied that soil fauna community was sensitive to temperature fluctuations, which is important in understanding the ecological processes in the winter–spring transitional period.