土地利用类型和水热条件影响喀斯特地区土壤无机磷和生物有效磷组分的特征

In order to gain an understanding of the characteristics of soil inorganic phosphorus and bioavailable phosphorus fractions affected by land use types and hydrothermal conditions in karst ecosystems, the characteristics of soil inorganic phosphorus and bioavailable phosphorus fractions in karst ecosystems were analyzed and compared across croplands, artificial forests, and natural forests in low hydrothermal regions (Nanchuan District in Chongqing, Dushan and Suiyang Counties in Guizhou) and high hydrothermal regions (Huanjiang, Mashan County/Wuming, and Longzhou Counties in Guangxi). One-way analysis of variance, two-factor analysis of variance, and correlation analysis were used to explore the different characteristics and the relationship between soil inorganic phosphorus fractions and bioavailable phosphorus fractions under the influence of land use types and hydrothermal conditions. Redundancy analysis was used to explore the key inorganic phosphorus fractions influencing soil bioavailable phosphorus fractions. The results were as follows: (1) Soil inorganic phosphorus fractions were significantly affected by land use types. The contents of dicalcium phosphate (Ca2-P), octacalcium phosphate (Ca8-P), phosphorus adsorbed on the Al oxides surfaces (Al-P), phosphorus adsorbed on the Fe oxides surfaces (Fe-P), occluded phosphorus (O-P) and decalcium phosphate (Ca10-P) in the soils of croplands were found to be higher than those in the soils of artificial forests and natural forests. Furthermore, the contents of Ca8-P, Fe-P and O-P exhibited the order of croplands > artificial forests > natural forests, whereas the contents of Ca2-P and phosphorus extracted by hydrochloric acid (HCl-P) demonstrated the order of croplands > natural forests > artificial forests. (2) In high hydrothermal regions, Ca10-P and O-P contents of natural forests soils were significantly higher than in low hydrothermal regions, and phosphorus extracted by enzymes (Enzyme-P) contents of artificial and natural forests soils were the opposite. (3) Soil inorganic phosphorus fractions Ca2-P, Ca8-P, Al-P, Fe-P and Ca10-P contents were significantly and positively correlated with bioavailable phosphorus fractions CaCl2-P and HCl-P contents. Redundancy analysis showed that Ca2-P was the key factor affecting the bioavailable phosphorus fractions. The results indicate that land use types and hydrothermal conditions are key fraction influencing the characteristics of soil inorganic phosphorus fractions and bioavailable phosphorus fractions. Increasing the contents of inorganic phosphorus fractions has a positive effect on bioavailable phosphorus fractions. Therefore, consideration should be given to the potential effects of future climate change on the fractions and availability of phosphorus in soil, thereby promoting the restoration of karst ecosystems.