Spatial distribution characteristics of fungal population in microbial fermentation bed for pig rearing

Pig rearing on microbial fermentation bed system is a new environmentally-friendly breeding method. Micro-organisms are critical for deodorization and decomposition of pig excrement. The aim of this study was to investigate the spatial distribution characteristics of fungal population in the litters of microbial fermentation bed at Fuqing Agriculture Modern Facilities Base, Fujian Academy of Agricultural Sciences, China. A total of 32 litter samples were collected in space and culturable fungi in each sample isolated and identified based on morphological characteristics and molecular identification. The spatial distribution characteristics of the fungal population in the fermentation bed were evaluated by analyzing spatial distribution frequency, spatial distribution index, diversity index and niche characteristics. This was critical for laying the needed basis for the management of pig fermentation beds, utilization of pig manure and control of pig diseases. From the study, a total of 18 fungal species were isolated from 32 samples, belonging to 10 different genera. The dominant genus was Aspergillus, which had 7 species. There were significant differences in the species and amount of fungi at different spatial samples. There were 1-4 species and 4.0×10²-5.8×10⁵ colonies·g^-1 of each species. Mucor racemosus and Penicillium citrinum had high frequency and population with a frequency distribution above 10. The amounts of Scopulariopsis brevicaulis, A. nidulans and A. candidus exceeded 2.0×10⁵ colonies·g^-1, belonging to the high population amount. Based on the results of the 6 spatial distribution indices and the Taylor power law test, the distribution of fungal population in fermentation beds had an aggregated distribution pattern. The results of population diversity index analysis for the 32 spatial samples showed that fungal population had obvious diversity, with aggregated and uneven distribution pattern in fermentation beds. Fungal population had higher richness, evenness and dominance in both 2-A and 3-D samples, which included species with higher frequency and population. This included M. racemosus, Cladosporium oxysporum and A. nidulans. However, fungal population had lower richness, evenness and dominance in both 1-A and 1-B samples that harbored more fungi with a frequency less than three times. This included A. candidus, S. brevicaulis and Geotrichum candidum. The analysis of the fungal population niche characteristics showed no positive correlation between niche breadth and overlap of the fungi. M. racemosus and C. oxysporum were the widest adaptability species, with ecological width of 7.60 and 5.18, respectively. However, the six fungal species (A. candidus, A. chevalieri, A. terreus, S. brevicaulis, F. equiseti and Chaetomium sp.) were the narrow adaptability species, with ecological width range of 1.00-1.10. For niche overlap, M. racemosus overlapped with 12 species, but C. oxysporum overlapped with only two species. In conclusion, fungal population had obvious community diversity in microbial fermentation bed system for pig rearing. The spatial distribution characteristics of fungi had aggrega-tion and uneven distribution pattern. M. racemosus and C. oxysporum were the dominant species, with a wide distribution and strong adaptability.