长期不同氮肥施用量对潮土团聚体分布和真菌群落组成的影响

不同氮肥施用量显著改变团聚体分布、真菌群落组成及生物胶结物质的产生，但它们之间是否存在相关性尚不清楚。以中国科学院封丘农业生态实验站长期定位试验（2005—2020年）为研究平台，其包含5个施氮水平：0（F0）、150 kg?hm-2（F1）、190 kg?hm-2（F2）、230 kg?hm-2（F3）和270 kg?hm-2（F4），研究了不同施氮量对土壤团聚体组成（>2 000 μm、2 000～250 μm、250～53 μm和<53 μm）的影响，以及团聚体组成与生物胶结物质（球囊霉素相关土壤蛋白（GRSP）及微生物生物量碳（MBC））和土壤真菌之间的相关关系。结果表明，土壤团聚体分布和真菌群落组成分为显著不同的3组，分别为F0、F1和F2以及F3和F4，其中，（1）F1和F2处理团聚体平均重量直径（MWD）最高，同时大于2 000 μm团聚体的质量比例显著增加，并与拟棘壳孢属（Pyrenochaetopsis）富集有关；（2）F1和F2、F3和F4处理均表现为2 000～250 μm团聚体的质量比例增加，而小于53 μm粉黏粒质量比例显著降低，2 000～250 μm团聚体的质量比例增加主要与易提取球囊霉素和总球囊霉素相关土壤蛋白比值（EE-GRSP/T-GRSP）以及易提取球囊霉素相关土壤蛋白（EE-GRSP）显著正相关，而与亚隔孢壳属（Didymella）和被孢霉属（Mortierella）相对丰度显著负相关；小于53 μm粉黏粒质量比例显著降低主要与被孢霉属（Mortierella）、白腐菌属（Phlebia）、黑孢壳属（Melanospora）、Fusicolla、柄孢壳属（Podospora）和亚隔孢壳属（Didymella）相对丰度显著正相关，而与EE-GRSP和/或支顶孢属（Acremonium）、柱霉属（Scytalidium）、外瓶霉属（Exophiala）、EE-GRSP/T-GRSP、MBC显著负相关。因此，土壤团聚体稳定性的变异程度受氮肥施用水平影响。本研究条件下，150 kg?hm-2和190 kg?hm-2施氮水平下的团聚体稳定性超过230 kg?hm-2和270 kg?hm-2施氮水平，与不同施氮量下真菌群落组成及其胶结物质变化显著相关。

Effects of Long-term Different N Application Rates on Aggregate Distribution and Fungal Community Composition in Fluvo-aquic Soil

【Objective】The aggregate distribution, the composition of the fungal community, and the production of biological binding agents can be significantly changed by different nitrogen (N) application rates. However, whether there is a correlation between these properties remains unclear. 【Method】A 16-year field experiment located in Fengqiu Agro-ecological National Experimental Station was used as the research platform, and this included five levels of N application rates, i.e. (1) F0: 0, (2) F1: 150 kg?hm-2, (3) F2: 190 kg?hm-2, (4) F3: 230 kg?hm-2, and (5) F4: 270 kg?hm-2. The effects of different N application rates on water-stable aggregate distribution (>2 000 μm, 2 000-250 μm, 250-53 μm and <53 μm) were explored, and the correlation between aggregate distribution and the major biological binding agents (glomalin-related soil proteins（GRSP）and microbial biomass carbon（MBC)) and soil fungal community was studied. 【Result】The soil aggregate distribution and fungal community composition were divided into three significantly different groups: F0, F1 and F2, F3 and F4, respectively. The results showed that: (1) F1 and F2 treatments had the highest mean weight diameter of soil aggregates and significantly increased the proportion of >2 000 μm aggregates and this was mainly related to the enrichment of Pyrenochaetopsis; (2) F1 and F2, F3 and F4 treatments all increased the proportion of 2 000-250 μm aggregates, while they significantly decreased the proportion of <53 μm aggregates. The increase of the proportion of 2 000-250 μm aggregates was significantly positively correlated with the ratio of easily extractable glomalin-related soil proteins to total glomalin-related soil proteins (EE-GRSP/T-GRSP) and easily extractable glomalin-related soil proteins (EE-GRSP). However, it was significantly negatively correlated with the relative abundance of Didymella and Mortierella. The decrease of the proportion of <53 μm aggregates was significantly positively correlated with the relative abundance of Mortierella, Phlebia, Melanospora, Fusicolla, Podospora and Didymella, but significantly negatively correlated with EE-GRSP and/or the relative abundance of Acremonium, Scytalidium and Exophiala, EE-GRSP/T-GRSP and MBC. 【Conclusion】The variation of soil aggregate stability was affected by the level of N application. Also, the stability of soil aggregates under N application rates of 150 kg?hm-2 and 190 kg?hm-2 was higher than that under N application rates of 230 kg?hm-2 and 270 kg?hm-2, which was significantly correlated with the changes in fungal community composition and biological binding agents under different N application rates.