Intermediate herbivory intensity of an aboveground pest promotes soil labile resources and microbial biomass via modifying rice growth
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Background and Aims
The importance of aboveground herbivores for modifying belowground ecosystems has prompted numerous studies; however, studies can be biased by context dependent conditions which lead to extremely inconsistent results. So far, the impacts of herbivory intensity by important rice pests on rice paddy soil ecosystems are lacking. The aim of this study was to test the hypothesis that intermediate herbivory intensity of the brown planthopper (Nilaparvata lugens Stål) could promote soil labile resources and microbial biomass, while high intensity would show a reverse pattern, by mediating rice plant growth. This study will also help the development of integrative pest management.
Four hopper infestation density treatments (0, 4, 8 and 12 nymphs per rice plant) and two infestation duration treatments (9 and 15 days after N. lugens infestation, DAI 9 and DAI 15) were established in a glasshouse experiment. Soil and plant were sampled destructively from four replicates and analysed for soil labile resources availability, soil microbial biomass and plant performance, respectively.
The infestation density significantly affected both shoot and root mass of rice (P < 0.05), soil dissolved organic carbon (DOC) and nitrogen (DON), and microbial biomass carbon (MBC) and nitrogen (MBN), and the effects were further enhanced by prolonged infestation duration. Compared to the control (CK) without N. lugens, plant dry mass, DOC, DON, MBC and MBN increased under low (LD) and moderate hopper densities (MD) but decreased under high density (HD) on DAI 9. Moreover, the LD treatment exerted the most promotional effects on DAI 15. Rice root to shoot ratio generally increased in treatments subjected to herbivory. The labile resources and microbial biomass showed close relationships with both shoot and root mass across treatments, in particular with root mass on DAI 15. Such a trend indicated that the shift of photosynthate allocation to belowground contributed to changes of soil resource availability and microbial biomass.
Intermediate herbivory intensity showed positive effects on rice seedling performance and, further, promoted soil labile resource availability and microbial biomass. The importance of extrapolating temporal and spatial scale, i.e. from the short-term greenhouse experiment to an entire rice growing season in the field, was highlighted.
KeywordsAboveground herbivore Belowground Nilaparvata lugens Herbivory density Infestation duration Soil microbial biomass Resource availability
Days after N. lugens infestation
Soil dissolved organic carbon
Soil dissolved organic nitrogen
Soil microbial biomass carbon
Soil microbial biomass nitrogen
Low hopper density
Moderate hopper density
High hopper density
This study was supported by the National Foundation of Sciences in China (31170487), National Key Basic Research Program of China (Grant No. 2010CB126200), the Fundamental Research Funds for the Central Universities and the PADA (Priority Academic Program Development of Jiangsu Higher Education Institutions). We thank Mr. Feng Wang and Miss Ying Tang for their laboratory work. We also thank Dr. Bryan Griffiths (SAC, Edinburgh, UK) and Dr. Anne Baily (Teagasc, Wexford, Ireland) for editing the manuscript.
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