Abstract
Nitrogen (N) and phosphorus (P) are the dominant limiting nutrients in alpine meadows, but it is relatively unclear how they affect the soil microbial community and whether their effects are rate dependent. Here, N and P addition rates (0, 10, 20, and 30 g m–2 year–1) were evaluated in an alpine meadow and variables related to plants and soils were measured to determine the processes affecting soil microbial community and enzyme activities. Our results showed that soil microbial biomass, including bacteria, fungi, gramme-negative bacteria, and actinomycetes, decreased along with N addition rates, but they first decreased at low P addition rates (10 g m–2 year–1) and then significantly increased at high P addition rates (30 g m–2 year–1). Both the N and P addition stimulated soil invertase activity, while urease and phosphatase activities were inhibited at low N addition rate and then increased at high N addition rate. P addition generally inhibited peroxidase and urease activities, but increased phosphatase activity. N addition decreased soil pH and, thus, inhibited soil microbial microorganisms, while P addition effects were unimodal with addition rates, achieved through altering sedge, and available P in the soil. In conclusion, our studies indicated that soil microbial communities and enzyme activities are sensitive to short-term N and P addition and are also significantly influenced by their addition rates.
Highlights
Nitrogen (N) and phosphorus (P) addition, either individually or in combination, have been shown to influence the above- and belowground ecosystem performance in many terrestrial ecosystems (Humbert et al, 2016; Li et al, 2016)
The results showed that the pathways of N and P addition determining soil microbial phospholipid fatty acid (PLFA) and enzyme activities were significantly different
The alpine meadows in the Qinghai-Tibetan Plateau are strongly limited in terms of available N and P levels (Xu et al, 2015; He et al, 2016)
Summary
Nitrogen (N) and phosphorus (P) addition, either individually or in combination, have been shown to influence the above- and belowground ecosystem performance in many terrestrial ecosystems (Humbert et al, 2016; Li et al, 2016). As an important component of the belowground ecosystems, soil microorganisms usually interact with the plants through roots and, form cooperative or competitive relationships (Zhou et al, 2021). Plant diversity and density are directly correlated with soil microbial diversity and function (Porazinska et al, 2018; Navratilova et al, 2019) and soil microbial biomass directly depends on plant species richness (Geisseler and Scow, 2014). These plant effects on soil microorganisms indicated that changes in plants would surely affect soil microbial community, while these effects remain elusive when N or P fertilisers are applied
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