Nitrogen enrichment buffers phosphorus limitation by mobilizing mineral‐bound soil phosphorus in grasslands

Abstract

Phosphorus (P) limitation is expected to increase due to nitrogen (N)‐induced terrestrial eutrophication, although most soils contain large P pools immobilized in minerals (Pi) and organic matter (Po). Here we assessed whether transformations of these P pools could increase plant available pools alleviating P limitation under enhanced N availability. The mechanisms underlying these possible transformations were explored by combining results from a 10‐year field N addition experiment and a 3700‐km transect covering wide ranges in soil pH, soil N, aridity, leaching, and weathering that could affect soil P status in grasslands. Nitrogen addition promoted the dissolution of immobile Pi (mainly Ca‐bound recalcitrant P) to more available forms of Pi (including Al‐ and Fe‐bound P fractions and Olsen P) by decreasing soil pH from 7.6 to 4.7, but did not affect Po. Soil total P declined by 10% from 385 ± 6.8 to 346 ± 9.5 mg kg−1, whereas available P increased by 546% from 3.5 ± 0.3 to 22.6 ± 2.4 mg kg−1 after the 10‐year N addition, associated with an increase in Pi mobilization, plant uptake, and leaching. Similar to the N addition experiment, the drop in soil pH from 7.5 to 5.6 and increase in soil N concentration along the grassland transect were associated with an increased ratio between relatively mobile Pi and immobile Pi. Our results provide a new mechanistic understanding of the important role of soil Pi mobilization in maintaining plant P supply and accelerating biogeochemical P cycles under anthropogenic N enrichment. This mobilization process temporarily buffers ecosystem P limitation or even causes P eutrophication, but will extensively deplete soil P pools in the long run.

Changes in soil phosphorus fractions under different land uses in desert grasslands in northwestern China

“…Increased ALP activity can accelerate microbial mineralization rates of P o and mobilize more P from less labile P o pools (Luo et al, 2019; Nannipieri et al, 2011; Sardans et al, 2006). The observed higher relative concentrations of Olsen P and the lower relative concentrations of moderately labile P (NaOH‐P) and recalcitrant P (HCl‐P o and residual P) in the shrub plantation than in natural desert grassland is further evidence for the transformation of P from less labile and non‐labile to labile P pools during the 28‐year‐long grassland‐to‐shrub plantation conversion (García‐Velázquez et al, 2020; Wang et al, 2021a).…”

Nitrogen loading enhances phosphorus limitation in terrestrial ecosystems with implications for soil carbon cycling

“…However, sources of P in terrestrial ecosystems are mainly from rock and mineral weathering, dust transport and atmospheric P deposition (Walker & Syers, 1976; Zhu et al, 2016). In contrast to the large amounts of anthropogenic N loading, the input of P is relatively small and much less readily available to plants and soil micro‐organisms (Hou et al, 2021; Peñuelas et al, 2013; Vitousek et al, 2010; Wang et al, 2022). These unbalanced N and P inputs have resulted in widespread ecosystem‐level P limitation (Ding et al, 2021; Hou et al, 2020; Li et al, 2016; Vitousek et al, 2010).…”

Characteristics of nitrogen deposition research within grassland ecosystems globally and its insight from grassland microbial community changes in China

“…The research areas of N deposition in grassland ecosystems at this stage are mainly concentrated in Inner Mongolia temperate grassland ( Tian et al, 2016 ), semiarid grasslands ( Wang et al, 2019 ), alpine grassland ( Jiang et al, 2018 ), and the Loess Plateau ( Chen et al, 2018 ) in China. The effect of nitrogen deposition on microbial is an important hotspot in current academic research ( Zhang et al, 2013 ; Zhao et al, 2021 ; Wang et al, 2022 ).…”