Nitrogen addition accelerates ecosystem phosphorus cycling at multiple scales in a temperate grassland of Northeast China

Abstract

<p>Plant phosphorus (P) resorption, mutualistic symbiosis with mycorrhizas, such as arbuscular mycorrhizal fungi (AMF) and soil organic P mineralization are crucial strategies for acquiring sufficient P to meet plant nutrient demand. Which is the main strategy, however, responding to elevated nitrogen (N) addition to alleviate P deficiency caused by N enrichment remains unclear in terrestrial ecosystems. We explored the responses of foliar P resorption of dominate species (Leymus chinensis), soil microbial properties and organic P mineralization to multi-level N addition in a temperate meadow steppe, Northeast China. We found the enhancements in plant biomass, microbial biomass C and N (MBC, MBN), alkaline phosphatase activities (ALP), and phoD gene abundance (main gene coded soil ALP), while the reductions in soil pH, available P, microbial biomass P, and AMF abundance, and no significant responses of foliar P content under simulative N deposition. When the rates exceeded the threshold 10 g N m<sup>-2</sup>yr<sup>-1</sup>, plants and microbes had little additional responses to N enrichment. Notably, N addition had distinct effects on three plant P acquisition strategies, that no conspicuous increase in P resorption efficiency, reduced dependence on mutualistic with AMF symbiosis and accelerated organic P mineralization. A positive correlation between ALP activity, phoD gene abundance and P mineralization rate suggested increases in phosphatase activities and its functional gene copies play crucial roles in organic P mineralization. Nitrogen addition aggravated P deficiency to the production of plant and microbial biomass, which further accelerated soil organic P mineralization and foliar P resorption. Due to lack of plasticity in P resorption efficiency and reduced dependence on mutualistic with AMF symbiosis, however, the organic P mineralization dominated in P acquisition to meet increased P demand. Furthermore, the increase in ALP activities, activation of phoD genes and decrease in soil pH were the main pathways to accelerate organic P mineralization and consequently alleviated P deficiency caused by anthropogenic N deposition, especially at conditions of N saturation. Our results provide strong evidences that N addition can accelerate the rate of P cycling and mobilize plant P uptake strategies such as soil organic P mineralization and leaf P resorption, which are important to better maintain sustainable ecosystem development in the more fertilized word.</p><p>Acknowledgments: This work was supported by the National Key Research and Development Program of China (2016YFC0500602), National Natural Science Foundation of China (31570470, 31870456), the Fundamental Research Funds for the Central Universities (2412018ZD010), and the Program of Introducing Talents of Discipline to Universities (B16011). H.C. acknowledges support from Chinese Scholarship Council (CSC).</p>

Deep mowing rather than fire restrains grassland Miscanthus growth via affecting soil nutrient loss and microbial community redistribution

“…Thus, our experimental findings indicate that deep mowing slightly altered the composition of soil bacteria, but largely altered the composition of soil fungal communities relative to other treatments (Figure 3). This finding is consistent with previous research showing the responses of soil bacterial and fungal communities to various grassland mowing and management practices (Cui et al, 2020). This effect can be attributed to two factors.…”

“…As discussed above, our experimental results clearly indicated that deep mowing resulted in a higher redistribution of the soil microbial community among all treatments. Although the stability of microbial communities in grasslands significantly affects soil quality and immunity (McCaig et al, 1999;Bonkowski and Roy, 2005;Otto et al, 2005;Cui et al, 2020), the structure and function of microbial communities in dry grasslands are influenced by numerous physicochemical soil factors (Jangid et al, 2011;Griffiths and Philippot, 2013;Zheng et al, 2019). Microbial communities are, therefore, regarded as a crucial mechanism affecting soil quality, which supports our third hypothesis.…”

Nitrogen addition regulates the effects of variation in precipitation patterns on plant biomass formation and allocation in a Leymus chinensis grassland of northeast China

“…As we expected, N input significantly altered the effects of variation in precipitation patterns on biomass formation and allocation (Figure 1). The primary productivity of the studied grassland was N limited (Yang et al, 2011;Cui et al, 2021); therefore, the N addition significantly enhanced leaf carbon assimilation rate and biomass accumulation (Figures 1A, C). For the aboveground biomass, we detected significant interactions between changes in precipitation amount and N addition, which is in line with the results of a few recently published studies (Li et al, 2019b;Ma et al, 2020).…”

Suppression of methane uptake by precipitation pulses and long-term nitrogen addition in a semi-arid meadow steppe in northeast China

“…The zonal soil at the study site is classified as Salic Solonetz (World Reference Base for Soil Resources) or an Aqui-Alkalic Halosol (Chinese soil classification) (Ren et al, 2019;Shi et al, 2019). The soil is saline-alkaline with a pH value of 8.0-10.0 (Cui et al, 2021). Table S2 shows the soil's chemical and physical properties at 0-10 cm depth as measured in the control and long-term N addition plots before the precipitation pulse treatments were applied.…”