Abstract:

Soil nematodes play an important role in carbon flow and nutrient cycles in forest ecosystems. In this paper, we investigated total nematodes and dynamics of the different trophic groups with seasons and soil depths, and analyzed their relationship with soil temperature, moisture and pH in ash (Fraxinus mandshurica) and larch (Larix gmelinii) plantations during 2007 and 2008. The soil nematodes were collected from soil with Sieving-centrifugation-flotation method. The results showed that: 1) the density of total nematodes in ash plantation was significantly higher than that in larch, averaged 1 079 ind. ·100 g^-1 dry soil in ash, and 394 ind. ·100 g^-1 dry soil in larch, respectively. Based on trophic groups classification, the majority of soil nematodes in two plantations was Plant-feeding nematodes (PF), the second-highest was Bacterivores (BA) and the minimum was Omnivores-Predators (OM-PR) and Fungivores (FF); 2) the densities of total nematodes and trophic groups were significantly higher in topsoil than that in deep soil across two-years investigation; 3) in the two years, the maximum population of total nematodes and trophic groups both occurred in autumn (October) in both plantations, while the minimum was in summer and spring; 4) total nematode densities were significantly and negatively correlated with soil moisture and pH, but positively with soil temperature in spring and summer. Overall, 46% (ash) and 49% (Larch) variations of total nematode density were able to be interpreted by combination of these soil factors. These results are important for understanding the relationships between soil nematodes and environmental factors in ash and larch plantations.

Key words: soil nematodes, trophic groups, Fraxinus mandshurica, Larix gmelinii, soil depth, seasonal dynamics