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Incubation temperature modulates the effects of exogenous nitrogen addition on decomposition and nutrient release of Phyllostachys edulis fine roots.

LIU Ren1,2, ZHANG Yu-fei1, JIN Zhi-fang3, MAO Rong1,2, ZHANG Yang1,2, LI Xiao-dong1, CHEN Fu-sheng1,2*   

  1. (1Jiangxi Provincial Key Laboratory of Silviculture, College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China; 2Key Laboratory of National Forestry and Grassland Administration on Forest Ecosystem Protection and Restoration of Poyang Lake Watershed, Jiangxi Agricultural University, Nanchang 330045, China; 3Jiulianshan National Nature Reserve Administration in Jiangxi of China, Longnan 341700, Jiangxi, China).
  • Online:2019-12-10 Published:2019-12-10

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Abstract: Fine root decomposition is an important component of carbon and nutrient cycles in moso bamboo (Phyllostachys edulis) forests. However, how exogenous nitrogen addition and temperature interact to affect bamboo fine root decomposition and nutrient dynamics is still unclear. In this study, a 360day microcosm incubation experiment was used to assess the effects of nitrogen addition (0 and 5 mg·N g-1 root) and incubation temperature (18 and 28 ℃) on cumulative CO2 production, mass loss, nutrients (N, P, Ca, Mg, Fe, Mn, and Cu) concentrations and remaining percentages, and enzyme activities during fine root decomposition. Our results showed that CO2 production, mass loss, and enzyme activities at 28 ℃ were significantly higher than those at 18 ℃, whereas N, P concentrations and remaining percentages, and P/Mn exhibited the reverse trend. The effects of nitrogen addition on bamboo fine root decomposition and enzyme activities varied with incubation temperature. Nitrogen addition significantly decreased cumulative CO2 production and mass loss, N/P, N/Mn, acid phosphatase (AP) and glycosidase enzymes (BG) activities at 28 ℃, but decreased Mn concentration and remaining percentage, N/Mn, BG and acetyl grape amine glycosidase (NAG) activities at 18 ℃. Nitrogen addition and incubation temperature significantly interacted to affect cumulative CO2 production at 0-180 d and 0-360 d, mass loss, AP and BG activities. By the end of incubation, N concentration, N/Mn, and P/Mn in decomposing fine roots were negatively correlated with AP, BG and NAG activities, while Mn concentration was positively correlated with BG and NAG activities. These findings suggest that exogenous N addition and incubation temperature co-regulated fine root decomposition and nutrient releases via regulating enzyme activities. Our results would help accurately assess and predict ecosystem C and nutrient cycles in bamboo forests under the context of global change.

Key words: diatoms, ecological thresholds, total nitrogen, total phosphorus, indicator taxa.