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This paper aimed at using the niche-fitness analysis method to assess soil fertility of cultivated land in Jianghan Plain in China. By introducing the niche-fitness theory into comprehensive analysis of soil fertility, an evaluation method was developed using geographic information systems (GIS) and the soil basic niche-fitness model (SBNFM). To begin with, 10 indicators were selected and used to assess the spatial differences of soil fertility for cultivated land, and its weight was decided using analytic hierarchy process (AHP). Soil samples were collected from topsoil (0–25 cm) in 58 units and examined for pH, organic matter (OM), total nitrogen (TN), etc. After standardizing soil attribute data of each unit, the optimum niche of every indicator was obtained and the soil basic niche-fitness value of each plot was calculated by using SBNFM. Finally, the soil fertility of the cultivated land was divided into four grades based on the shortest distance cluster analysis method in this area. Results indicate that the soil fertility of the cultivated land in this area was on the medium and high side, the percentages of area in grades 1, 2, 3 and 4 accounted for 33.43%, 35.99%, 22.70% and 7.88%, respectively; thus, approximately 70% of the cultivated land was classified in the top two grades. The linear-correlated relationship between niche-fitness value and rice yield has shown that SBNFM is an important and effective tool to analyze soil fertility and evaluate the quality of cultivated land. The above results might be helpful and support fertilizer management or agricultural activity in the study area. [ABSTRACT FROM AUTHOR]

The feeding ecology of soil animals is seldom investigated in the winter when the soil is covered with a layer of snow. Collembola (springtails) are winter-active arthropods that appear on the snow surface, especially on sunny days, and remain active in microhabitats under the snow. Since winter-active Collembola must be consuming food, we assessed the food resources for these Collembola with stable isotope and bacterial 16S rRNA gene amplicon sequencing methods. We collected two Desoria species from the snow surface and Tomocerus cf. jilinensis from subnivean microhabitats. The stable isotope signatures of winter-active Collembola species differed significantly from the soil litter layer. The isotopic signature of Desoria sp.1 was similar to the snow. Furthermore, the putative food resource (bacteria) ingested by Desoria sp.3 and Tomocerus cf. jilinensis were more from snow than from litter. All three Collembola species ingested a large proportion of Cyanobacteria. Moreover, a large proportion of bacteria associated with Collembola were putative symbionts. Bacterial communities and their associated metabolic functions were more similar in the two congeneric Desoria species than with Tomocerus cf. jilinensis. Our findings suggest that winter-active Collembola mainly feed on resources present in the snow layer. Stable isotope and amplicon sequencing methods are promising techniques to evaluate the diets of soil animals that remain active in snow-covered soils. • Food resources of winter-active Collembola mainly derived from snow. • Cyanobacteria were one of the predominant food resource bacteria. • A large proportion of Collembola-associated bacteria were putative symbionts. [ABSTRACT FROM AUTHOR]