Compositions and metabolic footprints of soil nematode communities under different alfalfa-crop planting patterns in semi-arid region of the Loess Plateau, Northwest China.

Abstract

Soil nematode communities play an important role in ecosystem material cycling and energy flow. In this study, soil samples were collected from three rotation systems in southern Ningxia mountainous region, including alfalfa continuous cropping (A-A), alfalfa-corn rotation (A-C), alfalfa-potato rotation (A-P). Soil physicochemical properties, nematode community composition and their metabolic footprints were measured. Compared with the A-A plot, the concentrations of soil organic carbon (SOC) and total nitrogen (TN) were significantly increased by 4.6% and 7.4% for SOC, 4.0% and 5.2% for TN in the A-C and A-P plots, respectively. Soil microbial biomass carbon and nitrogen were significantly higher in the A-C and A-P plots when compared with the A-A plot. The total abundance of soil nematodes in the A-C and A-P plots was higher by 49.5% and 93.7% than that in the A-A plot, respectively, with the dominant trophic group being changed to omnivores-predators from plant parasite. Compared to the A-A plot, the plant parasite index (PPI) was decreased significantly in the A-C and A-P plots, indicating that the harm of plant-parasites was reduced in soil food web. The nematode channel ratio (NCR) in the A-C and A-P plots were higher than that in the A-A plot, indicating that the role of bacterial decomposition was enhanced in soil organic matter decomposition. The maturity index (MI), the total nematode metabolic footprint, enrichment footprint, structure footprint in the A-C and A-P plots were all significantly higher than those in the A-A plot, suggesting that the structure and function of soil food web were more mature and stable, and the productivity and metabolic activity of nematodes were significantly enhanced. In general, the alfalfa-crop rotations improved soil nutrient status and reduced the disturbance degree of soil food web. Furthermore, soil ecosystem developed in the stable and healthy direction, which would be beneficial to the sustainable development of agriculture.