Soil P components and soil fungi community traits in poplar shelterbelts and neighboring farmlands in northeastern China: Total alterations and complex associations

Abstract

Phosphorus (P) is an indispensable element for all life on Earth, and clarifying soil P components can favor the precise management of soil nutrients. This paper hypothesized that soil total P (TP) and P components in different aggregates and leachable fractions differed between poplar shelterbelts and farmlands. Such changes were strongly associated with fungal variations. Total 24 soil samples were collected from 0 to 40 cm soil layers in 12 pairs of poplar shelterbelts and neighboring farmlands in four sites in Northeast China Plain. The soil P was determined in three soil aggregates (macroaggregates, microaggregates, and silt + clay) and nine sequential leachable fractions (H2O-Pi, NaHCO3-Pi, NaHCO3-Po, NaOH-Pi, NaOH-Po, HCl-Pi, conc. HCl-Pi, conc. HCl-Po, and Re-P), and soil fungi in bulk soils were analyzed by Illumina sequencing. Our data revealed that poplar shelterbelts had 27.75% lower soil TP than neighboring farmlands, mainly occurring in macroaggregates (0.25–2 mm) with no changes in microaggregates and silt + clay. In leachable P fractions, reduced TP was caused by changes in HCl-Pi contributed 47.8%, and NaOH-Pi contributed 34.2% (low or medium plant-available). Poplar shelterbelts decreased the soil fungi diversity and network relations with fewer nodes, edges, and modularity but contained more ectomycorrhizal and less pathogenic fungi than farmlands. The macroaggregates P reduction was mainly driven by fungal community changes, while the fraction-P changes were more closely related to soil pH and tree growth of poplar trees. Our findings highlighted high P depletion from poplars, possible risks for plant availability, and soil fungi roles in the China shelterbelt program, supporting the evaluation and management of soil P-related nutrients in the farmland afforesting system.