1. Micobial community (diversity and functional traits) underpin the sustainability of agroecosystems. Assembly processes influence microbial community composition and in turn determine their functional traits. However we have a poor understanding of how assembly processes that govern microbial community interact through time to maintain soil fertility.
2. Flooded rice fields are one kind of agroecosystems with high level of sustainability. Ancient rice paddies have a history of cultivation spanning hundreds or thousands of years and thus provide an ideal opportunity to explore relationships between community assembly processes and agroecosystem sustainability. In this study, we used statistical null models to evaluate temporal patterns of bacterial community assembly processes along rice cultivation years and their associations with increases in soil fertility in paddy agroecosystems.
3. We found that stochasticity was a persistent force structuring paddy soil microbial communities, putatively due to frequent flooding that facilities dispersal. However, determinism gradually increased over centuries of agriculture and corresponded to increases in soil fertility. Accordingly, multifunctionality, calculated using enzymes catalysing key soil functions in carbon, nitrogen, phosphorous and sulphur cycling significantly increased along rice cultivation years. We therefore propose that balanced assembly processes preserve a diverse array of traits that can dominate under various circumstances while also allowing for particular traits to be selected for by soil fertility, thus supporting multifunctionality that underpins agroecosystem sustainability.
4. In total, our results highlight that knowledge on temporal microbial assembly processes, community composition and ecological function in the context of soil fertility is key to understanding ecological mechanisms maintaining agroecosystem sustainability.

中文翻译：

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动态微生物组装过程对应于可持续稻田农业生态系统中的土壤肥力

1. 微生物群落（多样性和功能性状）是农业生态系统可持续性的基础。组装过程会影响微生物群落组成，进而决定其功能特征。然而，我们对控制微生物群落的组装过程如何随着时间相互作用以维持土壤肥力了解甚少。
2. 淹水的稻田是一种具有高度可持续性的农业生态系统。古代稻田有数百年或数千年的种植历史，因此提供了探索社区集会过程与农业生态系统可持续性之间关系的理想机会。在这项研究中，我们使用统计无效模型来评估水稻种植年间细菌群落组装过程的时间模式及其与水稻农业生态系统中土壤肥力增加的关联。
3. 我们发现，随机性是构成稻田土壤微生物群落的持久力，这可能是由于频繁的洪灾导致设施分散所致。但是，确定性在几个世纪的农业中逐渐增加，并对应于土壤肥力的增加。因此，随着水稻种植年限的增长，使用酶催化土壤，碳，氮，磷和硫循环中关键功能的酶计算出的多功能性显着提高。因此，我们建议平衡的组装过程保留在各种情况下都可以控制的多种特性，同时还允许土壤肥力选择特定的特性，从而支持支撑农业生态系统可持续性的多功能性。
4. 总的来说，我们的结果突出表明，在土壤肥力的背景下，有关时间微生物组装过程，群落组成和生态功能的知识是理解维持农业生态系统可持续性的生态机制的关键。