Soil moisture is a limiting factor for vegetation restoration on the Loess Plateau, China. Micro-topography may cause heterogeneities in the distribution of soil moisture, but little is known about its effect on deep ...Soil moisture is a limiting factor for vegetation restoration on the Loess Plateau, China. Micro-topography may cause heterogeneities in the distribution of soil moisture, but little is known about its effect on deep soil moisture. Our study aims to explore the distribution and impact of soil moisture within the upper 10 m of soil for different microtopographies. Taking undisturbed slope as the control, five micro-topographies were selected. Soil moisture over a depth of 0-10 m from 2017 to 2019 was investigated, and soil particle size and soil organic matter were measured. Variance analysis and multiple comparisons were used to analyze the difference in soil moisture for different microtopographies and multiple-linear regression was used to analyze the influence of micro-topography on soil moisture. There are significant differences in soil moisture within the different layers underlying the examined micro-topographies, while the inter-annual variation in soil water storage for the selected microtopographies increase with increased rainfall. The depth of influence of micro-topographic vegetation on soil moisture exceeded 1000 cm for a gully(GU), 740 cm for a sink hole(SH), 480 cm for a scarp(SC), 360 cm for an ephemeral gully(EG) and 220 cm for a platform(PL). Micro-topography will cause the heterogeneous distribution of soil moisture in the shallower layers, which changes the vegetation distribution differences between micro-topographies. This may be the survival strategy of herbaceous vegetation in response to climate change in the Loess Plateau. For future vegetation restoration efforts, we need to pay attention to the influence of microtopography on soil moisture.展开更多
A high-quality heralded single-photon source (HSPS) at 1.5 μm is experimentally demonstrated based on spontaneous four wave-mixing in a piece of dispersion-shifted fiber cooled by liquid nitrogen.To improve the up-li...A high-quality heralded single-photon source (HSPS) at 1.5 μm is experimentally demonstrated based on spontaneous four wave-mixing in a piece of dispersion-shifted fiber cooled by liquid nitrogen.To improve the up-limit of the preparation efficiency of the HSPS,commercial dense wavelength-division multiplexing components are used to reduce the loss of the filtering and splitting system between the fiber and the single-photon detectors.As a result,a preparation efficiency of 80% is realized under a g(2)(0) of 0.06 in our HSPS experimental system,which is the best performance for the fiber-based HSPS at 1.5 μm reported so far.展开更多
基金financially supported by the 13th Five-Year National Key Research and Development Project (No.2016YFC0501705) funded by the Ministry of Science and Technology (MOST),P.R.China。
文摘Soil moisture is a limiting factor for vegetation restoration on the Loess Plateau, China. Micro-topography may cause heterogeneities in the distribution of soil moisture, but little is known about its effect on deep soil moisture. Our study aims to explore the distribution and impact of soil moisture within the upper 10 m of soil for different microtopographies. Taking undisturbed slope as the control, five micro-topographies were selected. Soil moisture over a depth of 0-10 m from 2017 to 2019 was investigated, and soil particle size and soil organic matter were measured. Variance analysis and multiple comparisons were used to analyze the difference in soil moisture for different microtopographies and multiple-linear regression was used to analyze the influence of micro-topography on soil moisture. There are significant differences in soil moisture within the different layers underlying the examined micro-topographies, while the inter-annual variation in soil water storage for the selected microtopographies increase with increased rainfall. The depth of influence of micro-topographic vegetation on soil moisture exceeded 1000 cm for a gully(GU), 740 cm for a sink hole(SH), 480 cm for a scarp(SC), 360 cm for an ephemeral gully(EG) and 220 cm for a platform(PL). Micro-topography will cause the heterogeneous distribution of soil moisture in the shallower layers, which changes the vegetation distribution differences between micro-topographies. This may be the survival strategy of herbaceous vegetation in response to climate change in the Loess Plateau. For future vegetation restoration efforts, we need to pay attention to the influence of microtopography on soil moisture.
基金Supported by the National Basic Research Program of China under Grant Nos 2011CBA00303 and 2010CB327606Tsinghua University Initiative Scientific Research Program and Basic Research Foundation of Tsinghua National Laboratory for Information Science and Technology(TNList)。
文摘A high-quality heralded single-photon source (HSPS) at 1.5 μm is experimentally demonstrated based on spontaneous four wave-mixing in a piece of dispersion-shifted fiber cooled by liquid nitrogen.To improve the up-limit of the preparation efficiency of the HSPS,commercial dense wavelength-division multiplexing components are used to reduce the loss of the filtering and splitting system between the fiber and the single-photon detectors.As a result,a preparation efficiency of 80% is realized under a g(2)(0) of 0.06 in our HSPS experimental system,which is the best performance for the fiber-based HSPS at 1.5 μm reported so far.
