| The wind-water erosion crisscross region of the Loess Plateau is suffering the long-term interaction of wind and water erosion.The fragile ecological environment have seriously threatened the local ecological restoration and the survival of human.The shrub patches were typical pioneer successional vegetation types in the local area.To explored the effect of shrub patches(Artemisia ordosica)on the soil microhabitat,the surface runoff and sediment during rainfall,we investigated the microtopography,photothermal redistribution,water and nutrient spatial characteristics,and runoff and sediment yield in shrub patches(Artemisia ordosica)of different sizes.We studied the effects of microtopographic changes of shrub patches on light and heat redistribution,soil moisture and nutrient spatial distribution,surface runoff and sediment production.The main results of this study are as follows:(1)With the growth and development of shrub patches,the sand-fixing ability of shrub was enhanced.The mound forms a cone with a middle bulge and slower taper.The amount of sand-fixing patches in the large shrub patches(cube root volume d > 160 cm)was the highest.Due to the different distance of solar radiation reaching the ground,the surface light intensity and soil temperature at different sites under the shrub patches were different.The surface light intensity and soil temperature under shrubs were significantly lower than in the bare land(P < 0.05),and trend to decrease from the position of shrub taproot to the edge of the up-slope and down-slope.Compared with bare land,the light intensity of large,medium(80 cm < d <160 cm)and small(d < 80 cm)shrubs decreased by 55.45 %,45.46 %,and 34.87 %;the soil temperature decreased by 29.61 %,18.34 % and 7.44 %,respectively.The large shrub patch had the greatest effect on the redistribution of light and heat,and it effectively improved the conditions of light intensity and soil temperature under canopy of shrub patches.(2)During the growing season,soil water content of 0-10 cm soil depth was(excluding July)increased with the increasing shrub patches size.Soil water content(0-10 cm)of large shrub patch was highest and reached the peak value in August.Shrub patches could maintain high soil moisture than bare land.The water-stable aggregates of > 0.25 mm particle size under large shrub patches were significantly larger than other patches and bare land(P < 0.05).The mean weight diameter(MWD)of water-stable aggregates was increased with the shrub patches growing,and the large shrub patches was the largest.Soil organic matter content in large shrub patches was significantly higher than other patches and bare land in 0-10 cm soil depth(P < 0.05).(3)Rainfall was less in the beginning(May)and the end(September)of the growing season.The contribution of rainfall in May and September was smaller than other months,which showed that more water consumption in May and September in the study area.The fitting equation shows that the shrub patches could catch,utilize and maintain the surface runoff and sediment energy well during the rainfall.The runoff reduction benefits of medium shrub patches(35.93 %)were superior to the large shrub patches(31.38 %),small shrub patches(19.71 %)and bare land.The benefits of reducing sediment was greatly in the large shrub patches(49.25 %)than the medium shrub patches(62.36 %),small shrub patches(94.94 %)and bare land.The main factors influencing surface runoff were rainfall,rainfall duration and leaf area index.The main factors affecting the surface sediment yield were rainfall,rainfall duration,soil bulk density,saturated hydraulic conductivity,above-ground biomass,below-ground biomass and leaf area index.Compared with the bare land,the existence of shrub patches not only reduced the damage of solar radiation on the ground surface,but also effectively prevent the sandy soil erosion.The existence of shrub patches obviously improved the soil moisture and nutrients condition,which had certain significance in conserving soil hydroponics.Under the same rainfall conditions,the utilization rate of rainfall was increased with shrub patches growing.The intercept and utilize of surface runoff and sediment by shrub patches was essential for the recovery and development of degraded ecosystems in the wind-water erosion crisscross region on Loess Plateau. |
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