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Phosphorus (P) is an essential element for living organisms and a major limiting factor in many ecosystems. In recent years, global warming and nitrogen (N) deposition have become increasingly serious, with significant effects on the P cycle in terrestrial ecosystems. A series of studies were carried out on the soil P cycle, but how climate change affects this remains unclear. Field experiments with warming and N addition were implemented since April 2007. Infrared radiators manipulated temperature, and aqueous ammonium nitrate (10 g [m.sup.-2] [year.sup.-1]) was added to simulate N deposition. Compared with the control, N addition reduced soil total P; warming and N addition decreased soil available P; warming, N addition and warming plus N addition decreased microbial biomass P, but increased litter P; and warming and N addition increased phosphatase activity significantly. Correlation analysis showed that soil total P, available P, microbial biomass P and phosphatase activity were positively correlated with soil temperature and water content. Soil total P was positively correlated with microbial biomass P and phosphatase activity; and available P was positively correlated with microbial biomass P but negatively correlated with litter P. The results showed that warming and N deposition accelerated the soil P cycle by changing soil physical and chemical properties and soil biological activities (microbial and phosphatase activities). However, N addition reduced the capacity of microbes to fix P and reduced microbial biomass P, resulting in losses to the soil P pool, further aggravating P limitation in the Songnen Grassland ecosystem. Additional keywords: global warming, nitrogen addition, P cycle. Received 9 May 2019, accepted 7 September 2019, published online 28 October 2019, Introduction Over the last 60 years, terrestrial ecosystems have been influenced by significant human-induced environmental changes, including increases in nitrogen (N) deposition and average global temperatures (IPCC 2014). Global change [...]

Soil enzymes play vital roles in the decomposition of soil organic matter and soil nutrient mineralisation. The activity of soil enzymes may be influenced by climate change. In the present study we measured soil enzyme activity, soil microclimate and soil nutrients to investigate the response of soil enzyme activity to N addition and experimental warming. Warming enhanced phosphatase activity (35.8%), but inhibited the cellulase activity (30%). N addition significantly enhanced the activities of urease (34.5%) and phosphatase (33.5%), but had no effect on cellulase activity. Significant interactive effects of warming and N addition on soil enzyme activity were observed. In addition, warming reduced soil C (7.2%) and available P (20.5%), whereas N addition increased soil total N (17.3%) and available N (19.8%) but reduced soil C (7.3%), total P (14.9%) and available P (23.5%). Cellulase and phosphatase activity was highly correlated with soil temperature and water content, whereas urease activity was determined primarily by soil N availability. The results show that climate change not only significantly affects soil enzyme activity, but also affects the mineralisation of soil nutrients. These findings suggest that global change may alter grassland ecosystem C, N and P cycling by influencing soil enzyme activity. Additional keyword: climate change., Introduction Soil enzymes are important biological activators of underground energy flow and material circulation and play a crucial role in carbon (C) and nutrient transformation in grassland soil (Gorissen and [...]

Nitrogen (N) deposition can reduce plant species richness and cause grassland degradation, thus affecting grassland ecosystem stability. Arbuscular mycorrhizal (AM) fungi play an important role in ecosystem stability. However, the influences of AM fungi on grassland ecosystem stability under N deposition remain unclear. We need more information on the impacts of N accumulation on the interactions between AM fungi and the plant community. To test the contribution of AM fungi to grassland stability under N deposition, a 5‐year field experiment was conducted in a temperate meadow with two manipulated factors, namely, N addition and AM fungi suppression. The plant species richness and diversity, biomass stability, litter decomposition, and greenhouse gas emissions were quantified. Under N addition, AM fungi did not affect the plant species diversity and richness but altered the coverages of different functional groups and increased the aboveground productivity and biomass stability. Litter decomposition increased under N addition and increased more in the treatment where AM fungi were not suppressed. The emissions of N2O and CH4 in the AM fungi suppression treatment were much higher than those in the nonsuppression treatment under N addition. Our results suggest that AM fungi can alter the plant community structure, increase plant productivity and community biomass stability, accelerate litter decomposition, and reduce the soil total N concentration and emissions of N2O and CH4 under N addition. Our results highlight that the conservation of AM fungi should be considered to alleviate grassland degradation and maintain grassland ecosystem multifunctionality in the future considering global change. [ABSTRACT FROM AUTHOR]