Effect Of Sulfur Addition On Phosphorus Fraction Of Soil Aggregates In Meadow Grassland

Increased sulfur deposition leads to soil acidification,which has important effects on both the structure and function of terrestrial ecosystems.Sulfur addition alters the cycling and transformation of soil phosphorus in meadow grasslands,but there is a lack of systematic studies on the distribution of phosphorus fractions among soil aggregates.Based on this,we set up an acidification gradient experiment(0,1,2,5,10,15,20,50 g S m^-2yr^-1)with eight levels of sulfur addition based on the actual sulfur deposition(0.4-3.0 g S m^-2yr^-1)in the temperate meadow grassland of Inner Mongolia to systematically study the soil aggregates chemical properties,phosphorus fractions and dominant plant Leymus chinensis phosphorus fractions in response to sulfur addition.The main results were as follows:（1）The addition of high sulfur significantly reduced the p H,EC,phosphatase activity and phosphorus fractions of the bulk soil and aggregates of all particle sizes,but the addition of low sulfur changed the chemical properties of microaggregates,so the microaggregates were vulnerable to external interference.（2）Under the high sulfur addition treatment,the bulk soil and soil aggregate Na HCO₃-Pi increased significantly,and HCl-P decreased significantly;The content of bulk soil,small and micro aggregates Na OH-Po added with high sulfur was significantly higher than that of the control treatment.The content of bulk soil and microaggregate Residual-P added with high sulfur decreased significantly compared with the control.Soil acidification induced by sulfur addition promoted the dissolution and transformation of insoluble phosphorus.（3）The effective phosphorus content of the bulk soil and aggregates increased significantly with the addition of sulfur.There was no significant change in structural phosphorus and metabolic phosphorus in the phosphorus fractions of Leymus chinensis,the dominant plant added with sulfur.The content of residual phosphorus in Leymus chinensis increased significantly when sulfur was added;The main reason is that sulfur addition can improve the availability of phosphorus in soil,promote plant absorption,and reduce the decomposition of residual phosphorus of dominant species Leymus chinensis.