| The Loess Plateau suffers from the highest soil erosion intensity in China, and lies in a very fragile ecological and environment. Moss crust is the advanced stage of biological soil crusts development and succession, and is prevalent in the Loess Plateau. Generally, moss crust can affect the hydrological and soil erosion. Most studies suggested that biological soil crusts(BSCs) would limit rainfall infiltration, accelerate soil water consumption and also drive vegetation co mmunity development toward dry biochemical direction. In premise of aggravating unobvious soil erosion, we assumed taking certain interference treatment to BSCs to promote rainfall infiltration, improve soil water condition, ultimately to achieve positive succession of ecological system. Based on that assumption, we took moss crust in wind water erosion crisscross region in Loess Plateau as our research object, and carried out the moss crust interference experiments. We studied the effects of different interference intensity(harrowing and trampling) on the moss crust growth, soil water and water erosion, which aim to determine the appropriate disturbance ways and disturbance intensities. Conclusions are as follows:(1) Effects of disturbance on moss crust growth was closely related to the intensity of interference. Sight disturbance(disturbed 30%) didn’t obviously affect moss crust growth. Moderate(disturbed 60%) and severe disturbance(disturbed 90%) had negative influences on moss crust and they enlarged as the increase of disturbance intensity. Specifically, compared with CK(non-interference), mean coverage of sight-, moderate- and severe-harrowing treatments(harrowing 30%, 60%, 90%) reduced by 9.7%, 44.5%, 74.9% in fourth month, respectively, and their biomass decreased by 8.9%, 49.0%, 69.7%, respectively. Moss crust average coverage of sight-, moderate- and severe-trampling treatments(trampling 30%, 60%, 90%) respectively decreased by 8.8%, 33.8%, 56.6%, and their biomass respectively decreased by 12.8%, 27.6%, 40.8%. Therefore, moss crust was highly sensitive to harrowing and trampling interference.(2) BSCs(non-disturbance, CK) didn’t monolithically promote or inhibit water infiltration, which infiltration depth and soil water capacity were lower t han bare soil plots, causing soil moisture accumulating in shallow layer and deteriorate soil moisture environment. Harrowing treatments could significantly promote water infiltration, increase infiltration depth and capacity. Compared with CK, the total amount infiltration of sight-, moderate- and severe- harrowing treatments increased by 20.2%, 42.7%, 10.5%, respectively. The total amount infiltration of sight- and moderate- trampling treatments increased by 17.6% and 3.2% compared to CK, severe-harrowing treatment reduced by 21.8%. Therefore, water infiltration had relationship with disturbance method and intensity. Harrowing was more conducive to the promotion of infiltration than trampling.(3) Harrowing reduced surface runoff, but runoff differed in trampling treatments during the entire observation period(July to October in 2014). there were 12 times rainfall caused runoff. The total runoff of sight-, moderate- and severe-harrowing plots was 22.9%, 29.6%, 10.0% lower than CK, respectively. Compared with CK, sight- and moderate-tramping plots reduced runoff by 23.5% and 5.6%, but severe-tramping plots significantly increased runoff by 20.8%. Therefore, the same with the infiltration effect, harrowing was more conducive to reduce surface runoff than trampling.(4) Results indicated that BSCs can remarkably control and reduce soil eros ion, and the whole sediment yield has reduced by 54.9% as compared with bare soil plots. Compared to BSCs(CK), sight interference treatments were almost the same with CK, but moderate- and severe- trampling plots increased by 25.2% and 37.7%. The total sediment yield of moderate- and severe-harrowing treatments was 20.8% and 98.4% higher than CK, respectively.(5) Despite of fact that harrowing and trampling disturbance restrains moss crusts formation and growth, moss crust can quickly restore after slight interference. moss crust with moderate interference kept regress in the first rainy season(coverage still above 42%), which may be restored after several rainy season. Besides, sight-, moderate- harrowing and sight-trampling disturbance can accelerate water infiltration capability and reduced runoff without significantly aggravating soil erosion. Therefore under such conditions as infiltration restraint and soil moisture shallow accumulation because of large moss crust coverage, slight- and moderate harrowing or slight-trampling could be performed to promote water infiltration, improve soil water condition in small scale and accelerate ecosystem positive succession. |
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