biostudies-literatureLei GRegulation Technology of Key Substance Migration Processes at the Interface of Low-quality and Inefficient Forests in the Low Hilly Region of Southern China402https://www.ebi.ac.uk/biostudies/studies/S-EPMC12899702biostudies-literatureUnknown15(3)The coupling between tree biomass and soil microhabitats is central to subtropical forest soil functioning, yet species- and stage-specific tree-soil interactions remain understudied. This study quantified these interactions in two dominant species-<i>Cunninghamia lanceolata</i> (Lamb.) Hook. (<i>C. lanceolata</i>) and <i>Quercus fabri</i> Hance (<i>Q. fabri</i>)-across five diameter at breast height (DBH) classes (5-10, 10-15, 15-20, 20-25, 25-30 cm). Soil quality was characterized via the Soil Quality Index (SQI) based on 16 physicochemical and enzyme activity parameters, while random forest models identified biomass importance. Soil properties and enzyme activities varied with diameter class (<i>p</i> < 0.05): <i>C. lanceolata</i> showed a unimodal pattern (minimum at 15-20 cm DBH), whePlants (Basel, Switzerland)Diameter Class-Dependent Species-Specific Tree-Soil Feedback Linked to Soil Quality Between &lt;i&gt;Cunninghamia lanceolata&lt;/i&gt; (Lamb.) Hook. and &lt;i&gt;Quercus fabri&lt;/i&gt; Hance in Subtropical Forests.PMC128997022022YFF1303004Li WQi LYang YLei GChen TfalseDiameter Class-Dependent Species-Specific Tree-Soil Feedback Linked to Soil Quality Between &lt;i&gt;Cunninghamia lanceolata&lt;/i&gt; (Lamb.) Hook. and &lt;i&gt;Quercus fabri&lt;/i&gt; Hance in Subtropical Forests.The coupling between tree biomass and soil microhabitats is central to subtropical forest soil functioning, yet species- and stage-specific tree-soil interactions remain understudied. This study quantified these interactions in two dominant species-<i>Cunninghamia lanceolata</i> (Lamb.) Hook. (<i>C. lanceolata</i>) and <i>Quercus fabri</i> Hance (<i>Q. fabri</i>)-across five diameter at breast height (DBH) classes (5-10, 10-15, 15-20, 20-25, 25-30 cm). Soil quality was characterized via the Soil Quality Index (SQI) based on 16 physicochemical and enzyme activity parameters, while random forest models identified biomass importance. Soil properties and enzyme activities varied with diameter class (<i>p</i> < 0.05): <i>C. lanceolata</i> showed a unimodal pattern (minimum at 15-20 cm DBH), whe2026-01-01T00:00:00Z2026 Jan2026-07-08T03:11:30.228Z2026-07-08T03:07:49.711ZS-EPMC128997024168156510.3390/plants15030402