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Biological soil crust (biocrust) is a common surface cover on the rehabilitated slope land in Hill Loess Plateau. We investigated the responses of runoff and soil loss from biological soil crustal slope to rainfall intensity by using simulated rainfall trial. The results showed that the runoff and soil loss from biocrust slopes increased sharply at the beginning stage of rainfall and then became stable during 10 to 18 min. Compared to bare soil slope, the initial runoff generation time of biological soil crustal slope was significantly increased. The presence of biocrust could significantly decrease runoff and sediment by 21%-78% and 77%-95%, respectively. Rainfall intensities affected soil erosion of biocrust slopes mainly via affecting runoff. The transition from insignificant to significant correlation between runoff and soil loss from biological soil crustal slopes and rainfall intensities was observed with the increases of rainfall intensities. Once the rainfall intensity was higher than 1.5 mm·min-1, there was a significant decrease in the function of biocrust to decrease runoff and soil loss with the increases of rainfall intensities. Our results laid the foundation for the model simulation of runoff and soil loss from biocrust slopes under rainfall conditions.

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The effect of trampling disturbance on soil infiltration of biological soil crusts was investigated by using simulated rainfall. The results showed that the trampling disturbance significantly increased soil surface roughness. The increasing extent depended on the disturbance intensity. Soil surface roughness values at 50% disturbance increased by 91% compared with the undisturbed treatment. The runoff was delayed by trampling disturbance. A linear increase in the time of runoff yield was observed along with the increasing disturbance intensity within 20%-50%. The time of runoff yield at 50% disturbance increased by 169.7% compared with the undisturbed treatment. Trampling disturbance increased soil infiltration and consequently decreased the runoff coefficient. The cumulative infiltration amount at 50% disturbance increased by 12.6% compared with the undisturbed treatment. Soil infiltration significant decreased when biocrusts were removed. The cumulative infiltration of the treatment of biocrusts removal decreased by 30.2% compared with the undisturbed treatment. Trampling disturbance did not significantly increase the soil loss when the distur bance intensity was lower than 50%, while the biocrusts removal resulted in 10 times higher in soil erosion modulus. The trampling disturbance of lower than 50% on biocrusts might improve soil infiltration and reduce the risk of runoff, thus might improve the soil moisture without obviously increa sing the soil loss.

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We present the fabrication of 150 nm half-pitch Si grating templates by reactive ion etch (RIE), which are used in nanoimprint lithography (NIL) for high groove density gratings in SU-8 plastic. The etch properties such as the etch rate, profile and etching selectivity of Si over Cr as etch mask were carefully studied. Under the optimum condition Si gratings with 150 nm in linewidth, 480 nm in height and nearly 90 degree in verticality of the sidewall have been achieved. 150 nm half-pitch gratings on SU-8 were then successfully imprinted using the fabricated templates. The diffraction pattern of zeroth and first order from the SU-8 gratings was observed using a 266 nm laser beam. The developed nanofabrication technique in this work is applicable not only for templates but also for other nanostructures in silicon.