Abstract
Agricultural land use may deteriorate soil bacterial diversity and function in an agroecosystem. This study aimed to explore the impact of agricultural disturbance on the taxonomic and functional diversity of soil bacteria using a high-throughput sequencing method. We examined the bacterial community diversity in five types of flooded soils in the Hanon Maar Crater from two types of canals characterized by different nutrient levels and three field types with a different rice cultivation history. Proteobacteria (43.2%), Chloroflexi (19.8%), Acidobacteria (15.8%), Actinobacteria (5.1%), and Nitrospirae (5.0%) were the dominant phyla (>5%). The relative abundance of Actinobacteria was 7.1 times greater in the abandoned fields than in the polluted canal. Alpha diversity indices of taxonomic diversity showed strong negative correlations with C, N, and NH4+ levels. The 1.7-fold greater number of operational taxonomic units (OTUs) in abandoned fields than in paddy fields may be caused by factors other than nutrients. Functional analysis revealed that 11 putative functions, including cellulolysis and ligninolysis, were significantly affected by soil management. Functional diversity indices showed negative correlations with electrical conductivity (EC) and NH4+. Nitrogen input had a greater effect on bacterial taxonomic diversity than on functional diversity. Available P was positively correlated with the diversity indices. Taken together, these results suggest that keeping land fallow for more than 5 years and monitoring of C, N, and P levels are practical approaches for restoring taxonomic diversity but not functional diversity of soil bacteria. Our study demonstrated a decoupled response of taxonomic and functional diversity to rice cultivation, highlighting the necessity of further studies on the impact of decoupling on the stability of ecosystem functioning.
Highlights
IntroductionMaars are shallow volcanic craters formed during phreatomagmatic explosions [1]
Maars are shallow volcanic craters formed during phreatomagmatic explosions [1].The Hanon Maar Crater, created approximately 3.4 million years ago on Jeju Island, is the only maar-type crater on the Korean Peninsula [2]
We observed that agricultural land use in the Hanon Marr crater altered the soil bacterial community composition and diversity
Summary
Maars are shallow volcanic craters formed during phreatomagmatic explosions [1]. The Hanon Maar Crater, created approximately 3.4 million years ago on Jeju Island, is the only maar-type crater on the Korean Peninsula [2]. Located at the center of the Hanon Volcano, it is approximately 1.0–1.2 km in diameter. 500 years ago, the side wall of the crater was pulled down for drainage, and crop cultivation was started there [3]. Volcanic craters are valuable resources for obtaining climatic and ecological data on microbes and other biota [5,6]. Because of the historical and ecological importance of the Hanon Maar Crater, efforts have been made to restore its ecosystem. An important goal of such restoration is to preserve the soil, which provides valuable archaeological and geochemical data, which are, in turn, useful for research on climatic change [7]
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