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| Response of phosphorus fractions in soil aggregates to leaching：evidence from the soil of different land-use patterns in the upper reaches of the Chishui River |
| Received:February 17, 2025 Revised:May 19, 2025 |
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| KeyWord:Karst area;soil aggregates;land-use patterns;leaching loss of phosphorus |
| Author Name | Affiliation | E-mail | | FENG Xiaowen | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | MENG Xiangzhi | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | LI Yiran | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | WANG Zhen | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | WANG Keqin | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | HOU Lei | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | houlei_1985@126.com |
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| Abstract: |
| To investigate the effects of leaching on phosphorus（P）fraction loss in soil aggregates across land-use patterns, soils from slope cropland, shrubland, orchard, and plantation forest in the Longjing small watershed of the Chishui River ' s upper reaches were selected for indoor soil column leaching experiments. This study analyzed land-use differences in P fraction leaching characteristics and influencing factors, while estimating the annual P leaching flux of the Chishui River watershed. The results indicated that：macroaggregates（>2 mm） dominated all land-use soils（>52.06%）. Total phosphorus（TP）followed the order：orchard（1.98 g · kg-1）>shrubland（1.59 g · kg-1）> cropland（1.40 g · kg-1）>plantation forest（0.62 g · kg-1）. Fertilized soils（first three types）exhibited organic-bound phosphorus（OP） dominance（46.19%-65.49%）, while plantation forest showed Ca-bound phosphorus predominance（73.11%-86.14%）. Soluble phosphorus （SP）constituted the primary leachate P form. Slope cropland exhibited significantly higher TP（0.10 mg·L-1）, SP（0.09 mg·L-1）, and SP/ TP ratio（90.00%）than other types（P<0.05）, with cumulative leaching amount（0.185 3 mg）exceeding others by 1.79 – 1.89 times. Plantation forest displayed negative leaching loss（-14.23%）primarily attributed to aggregate OP retention, whereas other types showed 50.35%–61.64% P leaching loss rates dominated by OP and Fe/Al-bound phosphorus（Fe/Al-P）. Land-use variations in soil aggregate TP, Fe / Al-P, structural stability, pH, and SOM governed leaching responses. The annual P leaching flux of the Chishui River watershed reached 19.13 kg·hm-2, predominantly from cropland（73.35%）, with plantation forest exhibiting inhibitory effects（-2.69%）. This study reveals that fertilization-induced aggregate destabilization drives P leaching in Karst regions, while converting cropland to forests and afforestation effectively mitigate P loss. |
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