[Effect of Biochar on Soil Enzyme Activity & the Bacterial Community and Its Mechanism].

Biochar-based fertilizers can improve the mineralization of carbon and nitrogen in soil and enhance the soil micro-ecological environment due to particular physical and chemical properties. It is of great significance to explore the underlying mechanism of biochar-based fertilizer in the regulation of soil microorganisms and soil enzyme activity to improve soil quality. Field experiments were conducted to investigate the effects of different biochar-based fertilizer rates[0 (CK2), 0.6 (T1), 0.9 (T2), 1.2 (T3), and 1.5 (T4) t·hm-2]on soil nutrients, soil enzyme activity, and bacterial community structure. The results showed that with the application of biochar-based fertilizer, soil bulk density decreased, while the pH value, available P, available K, organic matter content, and the C/N ratio increased by 0.32%-5.83%, 14.09%-23.16%, 0%-38.70%, 7.49%-14.16%, and 4.06%-10.13%, respectively, compared to that of the CK2 treatment. With increasing rates of biochar-based fertilizer, the enzyme activity first increased and then decreased. Invertase (INV), urease (URE), catalase (CAT), and neutral phosphatase (NPH) activity under the application of biochar-based fertilizer were 63.73%-166.37%, 117.52%-174.03%, 12.98%-23.59%, and 60.84%-119.71% higher than that of CK2, respectively. The corresponding bacterial diversity was significantly improved, especially with regard to the increase in the abundance of growth promoting bacteria, such as Gemmatimonadetes and Proteobacteria, and decreased the abundance of Acidobacteria and Actinobacteria. The correlation analysis showed that soil C/N ratio was the key factor affecting soil enzyme activity, and there was a significant positive correlation between soil enzyme activity and bacterial diversity. There were significantly positive correlations among the activities of the above four soil enzymes and the relative abundance of Gemmatimonadetes (P<0.01), with CAT being the key factor affecting the bacterial community structure. This study revealed a relationship between soil enzyme activity and microbial colonies, which provides a theoretical basis and mechanism for applying biochar to regulate the soil enzyme and micro-ecological environment.

[Effect of Biochar Amendment on Physicochemical Properties and Fungal Community Structures of Cinnamon Soil].

To identify the effect of biochar addition on soil abiotic and biotic properties and provide evidence for the soil improvement with biochar input, the soil physiochemical properties and fungal community were investigated in a cinnamon soil after 3-year biochar additions of 10, 20, and 40 t ·hm-2. The relationship between the fungal community and edaphic physicochemical characteristics was also analyzed. The results showed that soil pH, moisture, total nitrogen (TN), and total organic carbon (TOC) significantly increased but dissolved organic carbon (DOC) content and soil bulk density decreased with biochar addition. High-throughput sequencing results indicated that biochar amendment had little influence on fungal α diversity but significantly changed the fungal community structure. The taxonomic classification showed that the dominant fungal phyla were Ascomycota, Zygomycota, and Basidiomycota, and these phyla accounted for more than 90% of the total sequences. The relative abundance of Ascomycota and Basidiomycota increased, while the abundance of Zygomycota decreased with biochar addition. At the genus level, biochar addition increased the relative abundances of Alternaria, Conocybe, and Aspergillus but decreased the relative abundances of Actinomucor and Gibberella. Redundancy analysis (RDA) showed that soil DOC, pH, and moisture were key environmental factors leading to the shift in the soil fungal community composition. In summary, the application of biochar changed the soil physicochemical properties, which drove the ecological succession of soil fungal communities.