The Interaction Mechanism Of Aggregates Characteristics And Physic-chemical Properties Of Red Soils And Their Effect On Erosion Processes

Soil aggregate is one of the important factors to determine soil anti-eredibility. The study of its' responses during erosion processes have great importance in reducing water erosion danger, stabilizing and improving agricultural production, preserving soil resources and balancing soil ecological system. Six typical red soils, which developed from three parent materials at Heshengqiao(Hl,H2,H3) and Tongcheng(T1,T2,T3), arc used in this paper. From the aspects of aggregate characteristics and physic-chemical properties, the susceptivity of red soil to water erosion, size characteristics of sediment and the physic-chemical mechanism of aggregates stability are studied using covered and uncovered net under simulated rainfall conditions. The main results are summarized as follows:During erosion process, soils (H2, T1) having more stability aggregates put off the time of emergence flow, and the time of steadying flow and their runoff volume is more less than other soils. In the covered net treatment the runoff volume of H2 and Tl is less 3.3L/6min and 2.6L/6min than uncovered, but other soils have similar runoff volume in two treatment. The time of emergence flow and steadying flow is delayed in the treatment of covered net. The sediment concentration changes greatly during erosion process, H2 and Tl increase with time, H1 and H3 increase at beginning and decrease subsequently, T2 and T3 decrease with time. In covered treatment the average sediment concentration is less 2.18-14.29g/l than uncovered.The sediment from high-clay soils has more stability aggregates and less primary particles than high -sand and high-silt soils, therefore it was much coarser. The runoff electively transport 0.002-0.02mm particle, and contains 26.68-60.33% of this class particle in sediment. The transportability of thin-flow and its selection to sediment particle decrease when splash is eliminated.DR, Sip and C/N are positively correlated with erosion rates, average sediment concentration and MWD (undispersed)/MWD(dispersed) of sediment; ASC ,CFI, clay%, iron and aluminum oxides, Sid , Si0 ,OM, HA, FA, humin are negatively correlated with them. DR, ASC ,CFI, clay%, Fed, Ald, Al0, Si0, OM, C/N, FA, humin are mostly significant or highly correlated with erosion rates ,average sediment concentration and MWD(undispersed)/MWD(dispersed) of sediment.Among erosion indexes, DR is negatively correlated with iron and aluminum oxides, Sid, Si0 ,OM, HA, FA, humin and positively correlated with Sip, C/N. ASC, CFI, clay% negatively correlated with Sip, C/N and positively correlate with others. Fed, Ald, A10,Si0, OM, C/N, FA, humin are mostly significant or highly correlated with DR, ASC, clay%.Fed, Ald, A10 and Si0 decrease with the increase of sediments size of Tongcheng soils. The low concentration in bigger particles make them less stable than small ones. Fea, Ald and A10 increase with the increase of sediments size of Heshengqiao soils. Their relative enrichment in bigger particles make big particles more stable.OM is enriched in sediment and more significant in the soils of Heshengqiao. OM and C/N indicated more POM is depleted from bigger particles and it can't stable aggregates. Organo-mineral complex can stable aggregates. POM is concentrated in 0.05-0.25mm particle in covered sediment of Tongcheng and <0.05mm particle in uncovered sediment of Tongcheng. Humus increases with the increase of particle size in sediment and aggregates. It may stable particles. HA changes differently in different soils and HA/FA changes with HA. The function that HA and FA stable particles is uncertain and worth studying further.