【摘要】 为研究紫色土区坡地农作物根系对不同坡位土壤微团聚体组成及稳定性的影响,以紫色土区种植典型粮食作物小麦(Triticum aestivum)的坡耕地(试验地)为研究对象,通过野外采样和室内分析得各粒级微团聚体质量分数,测定平均质量直径(MWD)、平均质量比表面积(MWSSA)、分形维数(D)等微团聚体稳定性指标。结果表明:试验地0. 01～0. 25 mm和<0. 001 mm粒级微团聚体质量分数高于对照地(裸地),而0. 005～0. 001 mm粒级则相反。0～10 cm土层中MWD在0、5和20 m坡位处比对照地显著增加59. 03%、42. 46%和29. 99%,MWSSA在5 m和20 m坡位则减小,而D除在5 m坡位外均高于对照地; 10～20 cm土层MWD在15 m坡位显著增加38. 23%,而MWSSA在10、15和20 m坡位均低于对照地。相关分析表明,D仅与<0. 001 mm粒级、MWSSA呈极显著正相关(P <0. 01)。在紫色土区种植小麦可拦截小粒级微团聚体并促进大粒级微团聚体聚合,改善土壤微团聚体组成;小麦根系对坡面边界位置(上坡和坡底)土壤微团聚体稳定性的影响最显著。更多还原

【Abstract】 [Background]The interaction between tillage erosion and water erosion causes soil and water losses in hilly croplands,which is a severe problem in hilly area with purple soil. In order to provide a scientific basis for the effects of wheat roots on water and soil conservation,the impacts of wheat roots on the composition and stability of soil micro-aggregates at different slope positions in purple soil were analyzed. [Methods]Two linear slopes were selected as the study site,which have an average gradient of 23%,and a horizontal length of 20 m. The whole slope was divided into 5 sample points: 1 m,5 m,10 m,15 m,and 20 m from the hill top to bottom. One slope where the typical wheat was cultivated was used as the treatment plot,while the other without wheat was used as the control plot. Five fractions( 0. 05-0. 25 mm,0. 01-0. 05 mm,0. 005-0. 01 mm,0. 001-0. 005 mm,and < 0. 001 mm) of soil micro-aggregates were obtained by field survey and laboratory analysis,and the micro-aggregates stability indicators included the mean weight diameter of aggregates( MWD),the mean weight soil surface area( MWSSA),and the fractal dimension( D). [Results]1) The proportion of coarse fractions( 0. 01-0. 25 mm) and < 0. 001 mm fractions in the treatment plot were higher than those in the control plot,especially at the 0 m slope position,while the 0. 005-0. 001 mm fraction was lower than that in the control plot. 2) In the range of 0-10 cm soil depth the significant differences( P < 0. 1) in MWD values were found at the 0 m,5 m,and 20 m slope positions,with increments of 59. 03%,42. 46%,29. 99%,respectively,and the MWSSA decreased compared with the control plot at the 5 m and 20 m slope positions. However,no significant changes were found at the other slope positions. The D was higher than that of the control plot except at the 5 m slope position. 3) The significant( P < 0. 1) increase of MWD by 38. 23% was found at the 15 m slope position,while the MWSSA was lower than that of the control plot at 10 m,15 m,and 20 m slope positions in 0-10 cm soil depth. 4) Correlation analysis indicated significant relationships between D and the proportion of < 0. 001 mm fraction( P < 0. 01).[Conculsions] Wheat roots in purple hillslope can intercept micro-aggregates of < 0. 001 mm and promote the polymerization from fine fractions( < 0. 01 mm) to coarse fractions( 0. 01-0. 25 mm),and improve soil micro-aggregate composition. The root system of winter wheat presents the most significant effect on the stability of soil micro-aggregates at the boundary of the slope field( upslope and downslope positions).更多还原