Effects of Plantation Type and Soil Depth on Microbial Community Structure and Nutrient Cycling Function

Bacterial diversity of cantaloupes and soil from Arizona and California commercial fields at the point of harvest

Across the United States, melons are a high demand crop reaching a net production of 2.7 million tons in 2020 with an economic value of $915 million dollars. The goal of this study was to characterize the bacterial diversity of cantaloupe rinds and soil from commercial melon fields at the point of harvest from two major production regions, Arizona, and California. Cantaloupes and composite soil samples were collected from three different commercial production fields, including Imperial Valley, CA, Central Valley, CA, and Yuma Valley, AZ, at the point of harvest over a three-month period, and 16S rRNA gene amplicon sequencing was used to assess bacterial diversity and community structure. The Shannon Diversity Index showed higher diversity among soil compared to the cantaloupe rind regardless of the sampling location. Regional diversity of soil differed significantly, whereas there was no difference in diversity on cantaloupe surfaces. Bray-Curtis Principal Coordinate Analysis (PCoA) dissimilarity distance matrix found the samples clustered by soil and melon individually, and then clustered tighter by region for the soil samples compared to the cantaloupe samples. Taxonomic analysis found total families among the regions to be 52 for the soil samples and 12 among cantaloupes from all three locations, but composition and abundance did vary between the three locations. Core microbiome analysis identified two taxa shared among soil and cantaloupe which were Bacillaceae and Micrococcaceae. This study lays the foundation for characterizing the cantaloupe microbiome at the point of harvest that provides the cantaloupe industry with those bacterial families that are potentially present entering post-harvest processing, which could assist in improving cantaloupe safety, shelf-life, cantaloupe quality and other critical aspects of cantaloupe post-harvest practices.

Temporal Variations in Aboveground Biomass, Nutrient Content, and Ecological Stoichiometry in Young and Middle-Aged Stands of Chinese Fir Forests

Understanding the ecological dynamics of forest ecosystems, particularly the influence of forest age structure on soil carbon (C), nitrogen (N), and phosphorus (P) content, is crucial for effective forest management and conservation. This study aimed to investigate the nutrient storage and ecological stoichiometry across different-aged stands of Chinese fir forests. Soil samples were collected from various depths (0-15 cm, 15-30 cm, and 30-45 cm) across four age groups of Chinese fir forests (8-year-old, 12-year-old, 20-year-old, and 25-year-old) in the Forest Farm, Pingjiang County, China. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured, and their stoichiometries were calculated. The results showed that both individual tree biomass and stand biomass, along with SOC, TN, and TP content, increased with stand age, highlighting the significant importance of stand age on biomass production and nutrient accumulation in forests. Specifically, soil C and P contents significantly increased as the forest aged, while variation in N content was relatively minor. Soil C/N and C/P ratios exhibited variation corresponding to forest age, suggesting alterations in the ecological stoichiometry characteristics of the forests over time. These findings are crucial for understanding the dynamics of ecosystem functioning and nutrient cycling within Chinese fir forests and provide a solid scientific basis for the effective management and conservation of these vital forest ecosystems.

Microbial Community, Co-Occurrence Network Relationship and Fermentation Lignocellulose Characteristics of Broussonetia papyrifera Ensiled with Wheat Bran

Broussonetia papyrifera has a high lignocellulose content leading to poor palatability and low digestion rate of ruminants. Thus, dynamic profiles of fermentation lignocellulose characteristics, microbial community structure, potential function, and interspecific relationships of B. papyrifera mixing with wheat bran in different ratios: 100:0 (BP100), 90:10 (BP90), 80:20 (BP80), and 65:35 (BP65) were investigated on ensiling days 5, 15, 30, and 50. The results showed that adding bran increased the degradation rate of hemicellulose, neutral detergent fiber, and the activities of filter paper cellulase, endoglucanase, acid protease, and neutral protease, especially in the ratio of 65:35. Lactobacillus, Pediococcus, and Weissella genus bacteria were the dominant genera in silage fermentation, and Pediococcus and Weissella genus bacteria regulated the process of silage fermentation. Compared with monospecific B. papyrifera silage, adding bran significantly increased the abundance of Weissella sp., and improved bacterial fermentation potential in BP65 (p < 0.05). Distance-based redundancy analysis showed that lactic acid bacteria (LAB) were significantly positive correlated with most lignocellulose content and degrading enzymes activities, while Monascus sp. and Syncephalastrum sp. were opposite (p < 0.05). Co-occurrence network analysis indicated that there were significant differences in microbial networks among different mixing ratios of B. papyrifera silage prepared with bran. There was a more complex, highly diverse and less competitive co-occurrence network in BP65, which was helpful to silage fermentation. In conclusion, B. papyrifera ensiled with bran improved the microbial community structure and the interspecific relationship and reduced the content of lignocellulose.