Purpose

To define geo-climates, soil properties, and land use effect on soil total phosphorus (TP) and its fractions in plantation forests and farmlands in the high-latitude northern hemisphere.

Methods

We measured nine sequential leaching P fractions (H₂O-Pi, NaHCO₃-Pi, NaHCO₃-Po, NaOH-Pi, NaOH-Po, HCl-Pi, conc. HCl-Pi, conc. HCl-Po, and Residual-P) from paired shelterbelt and farmland soils in 14 regions of Northeast China.

Results

For the whole northeast (NE) China Plain statistics, TP averaged at 196.39 mg kg⁻¹. 52.7% and 14.5% were from HCl-Pi and NaOH-Po, respectively. All P fractions in shelterbelts were lower than in farmlands (except for Re-P). (1) A paired t-test found lower NaHCO₃-Pi (31%, p = 0.036), TPi (18%, p = 0.051), and NaOH-Pi percentage (1.72%, p = 0.033) in shelterbelts. (2) Compared to farmlands, shelterbelts tended to have lower NaHCO₃-Po and TPi in low latitude regions, while having lower NaOH-Pi, conc. HCl-Pi, and Po in low pH regions. Warm regions had higher NaOH-Pi, HCl-Pi and conc. HCl-Pi but lower conc. HCl-Po. Alkalization reduced NaOH-P and conc. HCl-P but increased HCl-Pi. Variation partitioning found that soil factors explained 35.3%–50% of P variations, followed by geo-climates (23.3%–23.5%). (3) Glomalin-related soil protein (GRSP) and soil fungi regulated poplar-farmland P, and strong geo-climate and soil pH interactions were found. We identified five Inocybe species positively related to conc. HCl-Po, which was accompanied by the lower GRSP and strengthened at higher latitudes. Mortierella_alpina, Otidea_brunneoparva, and Leveillula_taurica could increase the stoichiometric percent of NaHCO₃-Pi and NaOH-Pi, but decrease HCl-Pi percentage, and this can be weakened in high pH soils.

Conclusions

Our results highlight that soil alkalization, latitude, and soil fungi determined shelterbelt-farmland soil P, favoring the proper P management in NE China.