Carex brunnescens, a pioneer plant that has an excellent ability to fix sand in the source region of the Yellow River （Maqu）, plays an important role in maintaining the ecosystem stability of alpine grassland in Maq...Carex brunnescens, a pioneer plant that has an excellent ability to fix sand in the source region of the Yellow River （Maqu）, plays an important role in maintaining the ecosystem stability of alpine grassland in Maqu. In this study, the biological characteristics （phonological characters, the growth process of overground and underground organs, and the morphological characters of underground organs） of C. brunnescens were studied by a field observation experiment. The results showed that C. brunnescens had the characteristics of turning green earlier than other plants, a long growth period, and two flowering and fruiting cycles. The leaf width, length and number of a single plant, and the density, coverage and leaf density of community increased significantly from the leaf extension period to the fruit mature period and then tended to be stable in the withering period, while the plant height and leaf area of a single plant and the leaf area of community rose significantly at first and then decreased. Underground stems （horizontal and vertical stems） and roots of C. brunnescens could survive in sand at a depth of 0-60 cm. The number of middle roots （0.2-0.5 mm in diameter） was the largest in all soil layers （0-20, 20-40 and 40-60 cm）, and the total length of fine roots （〈0.2 mm） were the maximum in the sand at a depth of 20-40 cm, while the total length of middle roots was the maximum in the sand layer at a depth of 0-20 cm. The length, fresh weight and dry weight of the main root, horizontal and vertical stems was the maximum in the sand layer at a depth of 10-30 cm and was the minimum in the sand layer at a depth of 40-50 cm. It is concluded that C. brunnescens can well adapt to the alpine sand habitat of Maqu, can be used as the constructive species for ecological restoration in the alpine desertified grassland of Maqu, and has good popularization and application prospects.展开更多
Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China. Understanding the composition, distribution, and transport processes of...Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China. Understanding the composition, distribution, and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion. In this study, based on laboratory rainfall simulation experiments, we analyzed rainfall-induced erosion processes on sand-covered loess slopes （SS） with different sand cover patterns （including length and thickness） and uncovered loess slopes （LS） to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion. The grain-size curves of eroded sediments were fitted using the Weibull function. Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS. The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed. The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS. Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes. The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage. Sand cover on loess slopes aggravates loess erosion, not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess, compared with the loess slopes without sand cover. The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount. Furthermore, given the same sand cover pattern, a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion. This difference explains the existence of intense erosion on slopes that are thinly covered with sand in regions where aeolian erosion and fluvial erosion interact.展开更多
黄河流域是我国重要的生态屏障和经济区,防风固沙服务及其驱动机制的研究对于筑牢黄河流域生态安全屏障具有重要意义。基于修正土壤风蚀模型(RWEQ)定量评估黄河流域2000—2018年防风固沙服务时空变化,采用相关分析和地理加权回归模型(G...黄河流域是我国重要的生态屏障和经济区,防风固沙服务及其驱动机制的研究对于筑牢黄河流域生态安全屏障具有重要意义。基于修正土壤风蚀模型(RWEQ)定量评估黄河流域2000—2018年防风固沙服务时空变化,采用相关分析和地理加权回归模型(GWR)从社会、气候、土壤、植被、地形等角度探究各驱动因素对黄河流域防风固沙服务影响的空间异质性。结果表明:(1)2000—2018年黄河流域土壤风蚀模数与单位面积防风固沙量分别以0.04 t hm^(-2)a^(-1)和0.14 t hm^(-2)a^(-1)的速率下降,而防风固沙保有率和植被覆盖度则分别以0.05%·a^(-1)和0.26%·a^(-1)的速率上升。(2)黄河流域土壤风蚀以微度(<2 t hm^(-2)a^(-1))和轻度(2—25 t hm^(-2)a^(-1))为主,共占研究区面积的96.28%。土壤风蚀在空间分布呈现西北高东南低的特点,而防风固沙服务高值则主要分布于西北部和下游流域。(3)各驱动因素对黄河流域防风固沙服务的影响具有明显的空间异质性,其中降水、温度、实际蒸散量、土壤黏粒含量、土壤有机质含量和坡度以负面抑制作用为主,而风速、气压、归一化植被指数和土壤粗砂含量则主要呈现正向促进作用。本研究结果可为黄河流域荒漠化防治和生态保护修复提供一定参考和依据。展开更多
文摘Carex brunnescens, a pioneer plant that has an excellent ability to fix sand in the source region of the Yellow River （Maqu）, plays an important role in maintaining the ecosystem stability of alpine grassland in Maqu. In this study, the biological characteristics （phonological characters, the growth process of overground and underground organs, and the morphological characters of underground organs） of C. brunnescens were studied by a field observation experiment. The results showed that C. brunnescens had the characteristics of turning green earlier than other plants, a long growth period, and two flowering and fruiting cycles. The leaf width, length and number of a single plant, and the density, coverage and leaf density of community increased significantly from the leaf extension period to the fruit mature period and then tended to be stable in the withering period, while the plant height and leaf area of a single plant and the leaf area of community rose significantly at first and then decreased. Underground stems （horizontal and vertical stems） and roots of C. brunnescens could survive in sand at a depth of 0-60 cm. The number of middle roots （0.2-0.5 mm in diameter） was the largest in all soil layers （0-20, 20-40 and 40-60 cm）, and the total length of fine roots （〈0.2 mm） were the maximum in the sand at a depth of 20-40 cm, while the total length of middle roots was the maximum in the sand layer at a depth of 0-20 cm. The length, fresh weight and dry weight of the main root, horizontal and vertical stems was the maximum in the sand layer at a depth of 10-30 cm and was the minimum in the sand layer at a depth of 40-50 cm. It is concluded that C. brunnescens can well adapt to the alpine sand habitat of Maqu, can be used as the constructive species for ecological restoration in the alpine desertified grassland of Maqu, and has good popularization and application prospects.
基金supported by the National Key Research and Development Program of China (2016YFC0402404, 2016YFC0402407)the National Natural Science Foundation of China (L1624052, 41330858, 41471226, and 51509203)the Dr.Innovation Fund of Xi’an University of Technology (310-252071505)
文摘Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China. Understanding the composition, distribution, and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion. In this study, based on laboratory rainfall simulation experiments, we analyzed rainfall-induced erosion processes on sand-covered loess slopes （SS） with different sand cover patterns （including length and thickness） and uncovered loess slopes （LS） to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion. The grain-size curves of eroded sediments were fitted using the Weibull function. Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS. The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed. The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS. Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes. The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage. Sand cover on loess slopes aggravates loess erosion, not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess, compared with the loess slopes without sand cover. The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount. Furthermore, given the same sand cover pattern, a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion. This difference explains the existence of intense erosion on slopes that are thinly covered with sand in regions where aeolian erosion and fluvial erosion interact.
文摘黄河流域是我国重要的生态屏障和经济区,防风固沙服务及其驱动机制的研究对于筑牢黄河流域生态安全屏障具有重要意义。基于修正土壤风蚀模型(RWEQ)定量评估黄河流域2000—2018年防风固沙服务时空变化,采用相关分析和地理加权回归模型(GWR)从社会、气候、土壤、植被、地形等角度探究各驱动因素对黄河流域防风固沙服务影响的空间异质性。结果表明:(1)2000—2018年黄河流域土壤风蚀模数与单位面积防风固沙量分别以0.04 t hm^(-2)a^(-1)和0.14 t hm^(-2)a^(-1)的速率下降,而防风固沙保有率和植被覆盖度则分别以0.05%·a^(-1)和0.26%·a^(-1)的速率上升。(2)黄河流域土壤风蚀以微度(<2 t hm^(-2)a^(-1))和轻度(2—25 t hm^(-2)a^(-1))为主,共占研究区面积的96.28%。土壤风蚀在空间分布呈现西北高东南低的特点,而防风固沙服务高值则主要分布于西北部和下游流域。(3)各驱动因素对黄河流域防风固沙服务的影响具有明显的空间异质性,其中降水、温度、实际蒸散量、土壤黏粒含量、土壤有机质含量和坡度以负面抑制作用为主,而风速、气压、归一化植被指数和土壤粗砂含量则主要呈现正向促进作用。本研究结果可为黄河流域荒漠化防治和生态保护修复提供一定参考和依据。
