Soil nematode communities in temperate rice-growing systems

Abstract

We compared soil nematode abundance, genus richness and feeding groups composition between four different biotope types (flooded rice paddies, upland crops planted one year after flooded rice, rice paddy bunds, and seminatural control grasslands) in temperate rice-growing systems in Russia. Our survey covered three major rice producing regions: Krasnodarsky Krai, Republic of Kalmykia in European Russia and Primorsky Krai in the Russian Far East, which have not been studied with this respect so far. Genus richness, C–P, maturiry (MI), Enrichment (EI) and Structure (SI) indices, and the total abundance of nematodes were strongly region-specific. The most of the highest values (18 genera, C–P = 2.6 ± 0.1, abundance 208.6 ± 10.1 ind. g−1 soil dwt) were found in Primorsky Krai and the lowest (6 genera, C–P = 2.1 ± 0.1, EI = 22.0 ± 1.3; SI = 55.4 ± 1.2; abundance 64.5 ± 3.3 ind. g−1 soil dwt) in Kalmykia. The highest values of enrichment and structure indices were discovered in Krasnodar Krai (EI = 53.1 ± 6.0 and SI = 82.9 ± 1.4 respectively). The abundance of the nematode feeding groups was in opposite rather driven by biotope type than the region. In the flooded rice paddies, the abundance of predatory nematodes was significantly lower than in control grasslands (2.1 ± 1.0 and 9.5 ± 3.0 ind. g−1 soil dwt, respectively). Alternatively, the abundance of fungivores increased in flooded rice paddies. We conclude that rice growing considerably alters the relative abundance of nematode feeding groups and consequently their role in detrital food webs due to alteration of the overall structure of a micro food web and specifically negative effects of flooding on predatory nematodes. Bunds act as important reservoirs of soil nematode diversity in the rice agroecosystems.