Phosphorus addition decreases plant lignin but increases microbial necromass contribution to soil organic carbon in a subalpine forest

Abstract

Increasing phosphorus (P) inputs induced by anthropogenic activities have increased P availability in soils considerably, with dramatic effects on carbon (C) cycling and storage. However, the underlying mechanisms via which P drives plant and microbial regulation of soil organic C (SOC) formation and stabilization remain unclear, hampering the accurate projection of soil C sequestration under future global change scenarios. Taking the advantage of an 8‐year field experiment with increasing P addition levels in a subalpine forest on the eastern Tibetan Plateau, we explored plant C inputs, soil microbial communities, plant and microbial biomarkers, as well as SOC physical and chemical fractions. We found that continuous P addition reduced fine root biomass, but did not affect total SOC content. P addition decreased plant lignin contribution to SOC, primarily from declined vanillyl‐type phenols, which was coincided with a reduction in methoxyl/N‐alkyl C by 2.1%–5.5%. Despite a decline in lignin decomposition due to suppressed oxidase activity by P addition, the content of lignin‐derived compounds decreased because of low C input from fine roots. In contrast, P addition increased microbial (mainly fungal) necromass and its contribution to SOC due to the slower necromass decomposition under reduced N‐acquisition enzyme activity. The larger microbial necromass contribution to SOC corresponded with a 9.1%–12.4% increase in carbonyl C abundance. Moreover, P addition had no influence on the slow‐cycing mineral‐associated organic C pool, and SOC chemical stability indicated by aliphaticity and recalcitrance indices. Overall, P addition in the subalpine forest over 8 years influenced SOC composition through divergent alterations of plant‐ and microbial‐derived C contributions, but did not shape SOC physical and chemical stability. Such findings may aid in accurately forecasting SOC dynamics and their potential feedbacks to climate change with future scenarios of increasing soil P availability in Earth system models.

Nutrient addition affects stability of soil organic matter and aggregate by altering chemical composition and exchangeable cations in desert steppe in northern China

“…Phosphorous has also been shown to minimize the degradation of lignin components. Stable lignin tends to selectively accumulate in the soil, thus enhancing its aromatic compound proportion (Luo et al, 2022). Meanwhile, the proportion of aromatic‐C was found to be higher in the aggregates <0.25 mm than in macro‐aggregate, which confirmed the percentage of micro‐aggregates was highest for the P addition treatment (Figure 6 and Table 1).…”

“…This can be explained that C input originating from the root litter was reduced to a higher degree than the C output related to reduced oxidase activity. However, the addition of P enhanced the accumulation of microbial necromass and contribution that it makes to SOM (Luo et al, 2022). Nevertheless, it should be noted that there are distinctly different effects produced by the addition of P and N on different soil aggregate‐relevant SOM.…”

Bacterial biomarkers are linked more closely to wheat yield formation than overall bacteria in fertilized soil

“…Little is known about how fertilization impacts the abundance of bacterial biomarkers and thus affects crop yield. Increasing application of the partial least squares path modelling (PLS‐PM) has provided unprecedented, in‐depth analyses of the relationships between microorganisms and crop productivity, offering deeper insight into the soil–plant–microbe interactions (Ai et al, 2018; Cao et al, 2022; Luo et al, 2022). Hence, we used PLS‐PM to investigate the connections between bacterial biomarkers and wheat yield under different fertilization regimes to provide a theoretical foundation for optimizing fertilization management and maximizing the benefits of bacterial biomarkers and thus enhancing productivity.…”

Nitrogen fertilization weakens the linkage between soil carbon and microbial diversity: A global meta‐analysis

“…C accumulation through microbial controls on C cycling (Delgado-Baquerizo et al, 2013;Luo et al, 2022;Singh et al, 2010). Recently, the positive role of microbes in soil C storage through the "microbial carbon pump" (MCP) has been emphasized (Liang et al, 2017).…”