Xiumin Yan

Pathways of N2O emission from rice paddy soil

Abstract The pathways of nitrous oxide (N 2 O) emission from a paddy soil were investigated in a pot experiment. The results indicate that the main pathway of N 2 O emission from rice–soil system depends on the soil water status. When the soil was flooded, the emission was predominantly (87.3% on average) through the rice plants, while in the absence of floodwater, N 2 O was emitted mainly through the soil surface, with only 17.5% on the average released through the plants. Cutting the rice stems below water surface immediately decreased the N 2 O flux to 55.8% of that before cutting, while the N 2 O flux from the pots with intact plants did not change. Two days after the cutting, the average N 2 O flux from the cut pots was 51.1% of that from the intact pots. During the absence of floodwater, cutting the rice stems did not significantly affect the N 2 O flux compared with that from the pots with intact plants.

Euedaphic and hemiedaphic Collembola suffer larger damages than epedaphic species to nitrogen input

Wetlands are commonly limited in available nitrogen. But marshes in the Sanjiang Plain, Northeastern China suffer large amounts of exogenous nitrogen from agriculture fertilization after wetland reclamation. This paper focuses on the ecological effects of a short-term increase of nitrogen input on collembolan communities. Our results show a significant decrease in collembolan abundance and Shannon diversity index, and the abundance of euedaphic and hemiedaphic collembolans decreased faster than epedaphic collembolans. These results indicate that euedaphic or hemiedaphic fauna suffer more biodiversity loss caused by nitrogen deposition than epedaphic fauna and call for more researches on trait-based approaches under environmental stress in the future.

Daytime warming has stronger negative effects on soil nematodes than night-time warming

Warming of the climate system is unequivocal, that is, stronger warming during night-time than during daytime. Here we focus on how soil nematodes respond to the current asymmetric warming. A field infrared heating experiment was performed in the western of the Songnen Plain, Northeast China. Three warming modes, i.e. daytime warming, night-time warming and diurnal warming, were taken to perform the asymmetric warming condition. Our results showed that the daytime and diurnal warming treatment significantly decreased soil nematodes density, and night-time warming treatment marginally affected the density. The response of bacterivorous nematode and fungivorous nematode to experimental warming showed the same trend with the total density. Redundancy analysis revealed an opposite effect of soil moisture and soil temperature, and the most important of soil moisture and temperature in night-time among the measured environment factors, affecting soil nematode community. Our findings suggested that daily minimum temperature and warming induced drying are most important factors affecting soil nematode community under the current global asymmetric warming.