We investigated whether enhanced nitrogen (N) and water inputs would redistribute the microbial community within different soil aggregate size classes in a field manipulation experiment initiated in 2005. Distribution of microbial groups was monitored in large macroaggregates (>2000 μm), small macroaggregates (250–2000 μm), and microaggregates (<250 μm) in a semiarid grassland. Both arbuscular mycorrhizal (AM) fungi and saprophytic fungi were the most abundant in soil macroaggregates. The gram-negative bacteria were more abundant in soil microaggregates. Total phospholipid fatty acid (PLFA) concentration in general and actinomycetes in particular decreased with N addition under ambient precipitation but was unaffected by combined additions of N and water within the three soil aggregate fractions as compared to control plots. In contrast, the abundance of saprophytic fungi decreased with combined N and water addition, but it was not affected by N addition under ambient precipitation. The abundance of gram-positive bacteria increased with N addition under both ambient and elevated water conditions for all soil aggregate fractions. In summary, the higher short-term nutrient and water availabilities provoked a shift in soil microbial community composition and increased total PLFA abundance irrespectively of the level of soil aggregation. In the long term, this could destabilize soil carbon pools and influence the nutrient limitation of soil biota within different soil aggregate size classes under future global change scenarios. 相似文献
A field experiment was conducted to assess the role of nitrogen (N) and water addition in shaping soil fungal communities and co-occurrence networks in temperate grassland, northern China.
Materials and methods
We measured soil fungal and plant community compositions, and also soil properties including available N, phosphorus, potassium concentrations, soil pH, and soil moisture. Soil fungal co-occurrence networks were constructed using a random matrix theory–based network inference approach.
Results and discussion
Plant species richness was decreased by N addition but increased by water addition, whereas fungal richness was decreased by N addition. The fungal community composition was significantly changed by both N addition and water addition. Soil fungal α diversity and β diversity were explained by a combination of variations in plant species richness and plant functional composition, and also by changes in soil pH via the soil acidification pathway induced by N and water addition. The fungal co-occurrence networks were more complex and clustered under water addition than that in ambient precipitation.
Conclusions
Our results suggested that plant functional composition, plant species richness, and soil acidification should be incorporated into ecosystem models for predicting soil fungal communities under future climate changes in terrestrial ecosystems.
