Frequency and intensity of nitrogen addition alter soil inorganic sulfur fractions, but the effects vary with mowing management in a temperate steppe

Abstract

Abstract. Sulfur (S) availability plays a vital role in driving functions of terrestrial ecosystems, which can be largely affected by soil inorganic S fractions and pool size. Enhanced nitrogen (N) input can significantly affect soil S availability, but it still remains largely unknown if the N effect varies with frequency of N addition and mowing management in grasslands. To investigate changes in the soil S pool and inorganic S fractions (soluble S, adsorbed S, available S, and insoluble S), we conducted a field experiment with different frequencies (two times per year vs. monthly additions per year) and intensities (i.e., 0, 1, 2, 3, 5, 10, 15, 20, and 50 g N m−2 yr−1) of NH4NO3 addition and mowing (unmown vs. mown) over 6 years in a temperate grassland of northern China. Generally, N addition frequency, N intensity, and mowing significantly interacted with each other to affect most of the inorganic S fractions. Specifically, a significant increase in soluble S was only found at high N frequency with the increasing intensity of N addition. Increasing N addition intensity enhanced adsorbed S and available S concentrations at low N frequency in unmown plots; however, both fractions were significantly increased with N intensity at both N frequencies in mown plots. The high frequency of N addition increased the concentrations of adsorbed S and available S in comparison to the low frequency of N addition only in mown plots. Changes in soil S fractions were mainly related to soil pH, N availability, soil organic carbon (SOC), and plant S uptake. Our results suggested that N input could temporarily replenish soil-available S by promoting dissolution of soil-insoluble S with decreasing soil pH and mineralization of organic S due to increasing plant S uptake. However, the significant decrease in organic S and total S concentrations with N addition intensity in mown plots indicated that N addition together with biomass removal would eventually cause soil S depletion in this temperate grassland in the long term. Our results further indicated that using large and infrequent N additions to simulate N deposition can overestimate the main effects of N deposition and mowing management on soil S availability in semiarid grasslands.

Nitrogen addition alters plant growth in China’s Yellow River Delta coastal wetland through direct and indirect effects

“…Secondly, the plant allocated fewer resources for S acquisition because it must allocate more resources for P acquisition, which is the first limited resource ( Chen et al., 2016a ). It contradicts the findings of Li et al. (2019) , and they discovered that plant S uptake increased with nitrogen addition in a S-deficient temperate steppe.…”

Effects of nitrogen and water addition on soil carbon, nitrogen, phosphorus, sulfur, and their stoichiometry along soil profile in a semi-arid steppe

“…In the long run, plant growth processes and plant residue inputs into the soil varied significantly under low-and high-N addition rates (Bai et al 2010), which may further affect soil C and nutrient cycling. High-N addition typically inhibits plant growth and the subsequent return of plant residues to soil due to low soil pH and the toxic effects of ammonium on plants rather than having a favorable impact on these processes (Tian and Niu 2015;Li et al 2019;Niu et al 2022b). Third, alterations in plant and microbial traits, especially their competition for soil nutrients, may result in an unsynchronized response of these soil elements (Moreau et al 2015;Craig and Fraterrigo 2017).…”

“…Experimental findings show that N addition altered the soil stoichiometry in grassland ecosystems by boosting soil C and N contents while decreasing soil P and S levels (Li et al 2019;Ning et al 2021;Xu et al 2021). However, related findings are not entirely consistent among different experiments because the effects of N addition would vary with several factors like the rate of N addition, the depth of soil, and the availability of water (Chen et al 2016;Gao et al 2018;Coonan et al 2019).…”

“…The majority of earlier investigations discovered well-constrained relationships among soil C, N, and P, suggesting that alterations in the stoichiometry of these nutrients may better reflect variations in their availability in soils under environmental changes (Cleveland and Liptzin 2007;Elser et al 2010;Yue et al 2017). Apart from C, N, and P in soils, the element S is also a fundamental component of proteins and critical to the growth of organisms (Blum et al 2013;Li et al 2019). It is crucial to recognize changes in S availability and its stoichiometric relationships with C, N, and P in order to comprehend how these elements interact in the dynamics of ecosystem services and to evaluate the degree of nutrient restriction in ecosystems (Chen et al 2016).…”