Using high-throughput sequencing quantitatively to investigate soil nematode community composition in a steppe-forest ecotone

The analysis of nematode community composition by high throughput sequencing (HTS) has attracted much attention because of its advantage for throughput, high resolution and coverage. However, we are still not clear whether the sequenced data will result in similar estimates in the absolute abundance and biomass of the nematode community as shown by morphological analysis. To better compare these two methods, we investigated the nematode community structure and composition from a steppe-forest ecotone. Based on high-throughput sequencing and morphological identification approaches, we compared the abundance and biomass of total nematodes as well as different feeding groups in meadow steppe, transition ecotone and forest ecosystems. Our results suggested that the absolute abundance conversion from the relative abundance obtained by HTS present the same ecological conclusions in the nematode community composition and trophic structure with that of the morphological analysis. The plant-parasite index was significantly higher in meadow-steppe than those in the transition ecotone and the forest ecosystems. The Shannon-Wiener diversity, evenness and the observed richness obtained by the two methods showed similar patterns (MS > TS > FS) among the three ecosystems. The observed richness obtained by HTS was higher than that of morphological analysis. However, the biomass of bacterivores obtained by the two methods exhibited a weak correlation. Despite the limitations both approaches have, our results suggested that HTS can be used quantitatively to understand changes in nematode communities in the steppe-forest ecotone from the abundance aspect. The improvement of the database used by the HTS may further enhance the accuracy of ecological information obtained by molecular techniques.