| Sloping farmland is the most important type of cultivated land in the Loess Plateau,which is characterised by sparse vegetation, fragmented landform by erosion, and severe soiland water loss, and is vulnerable to loss of soil and water. Hedgerow is acknowledgedextensively as an multi-effective and sustainable soil and water conservation measure.Onobrychis viciaefolia Scop, Medicago sativa L., Amorpha fruticosa Linn.were selected asresearch object in our study. Soil particle composition and content of soil organic carbon andnitrogen were measured using particle composition, potassiumdichromate colorimetricmethod, the Kjeldahl method, respectively.We analyzed the effects of hedgerow on the soiland water conservation aiming at providing theoretic foundation for the extension ofhedgerow in the research area.The following conclusions were drawn.(1) Hedgerow improved the soil particle composition evidently. The effects of hedgerowconsisting of Amorpha fruticosa Linn.was the best among that of Onobrychis viciaefoliaScop (OS hedgerow), Medicago sativa L.(MS hedgerow) and Amorpha fruticosaLinn.(AS hedgerow). The content of coarse silt in the OS and MS. hedgerow increasedfrom the upper slope to the lower slope and vice versa in the AShedgerow. The content ofvery fine sand and coarse silt increased by4.5%and3.9%,4.8%and3.1%in OS and MS,respectively, and decreased by2.8%and2.4%in AS hedgerow. The content of fine siltand clay decreased by6.2%and4.4%,8.3%and10.6%in OS and MS hedgerow,respectively, and increased by6.7%,7.1%in AS hedgerow.(2) Hedgerow changed soil fractal dimensions. The finer the soil texture, the higher the valueof fractal dimension, the better the soil structure.The soil fractal dimentions in the upper,middle and lower slope were2.4635,2.4691and2.4008,2.5005,2.4961and2.4764,2.4117,2.4684and2.5112, for OS, MS and AS, respectively. Soil fractal dimentions wereboth affected by slope position and plant species. Soil structure became better from theupper slope to the lower slope in AS hedgerow, while that did worse in OS and MShedgerow. Soil structure in MS hedgerow was better than that in OS hedgerow.(3) Soil was deposited in the hedgerow, while be eroded under the hedgerow. Compared withthat under the hedgerow, the soil fractal dimensions in the hedgerow were largersignificantly. The difference between soil fractal dimensions in the hedgerow and under the hedgerow was larger for OS hedgerow than that for MS hedgerow and the effect ofsoil and water conservation of OS hedgerow was also better than that of MS hedgerow.The effect of soil and water conservation under the hedgerow of AS was better than that ofOS, while that in the hedgerow of AS be worse than that of OS, which is under continuedinvestigation.(4) Hedgerow advanced the content of soil nutrition. The soil nutrition content in differentslope position related to the content of clay. The variation of soil organic carbon andnitrogen content in different slope position were similar to those of the content of clay anfine silt, which decreased from the upper slope to the lower slope in OS and MS hedgerowand increased in AS hedgerow. Soil organic carbon content in different hedgerow variedeach other. That in OS and MS hedgerow, which were similar, werelower significantlythan that in AS hedgerow. There were no significant differences among the soil nitrogencontent of different hedgerow. |
