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961.
Response of artificial grassland carbon stock to management in mountain region of Southern Ningxia,China 总被引:1,自引:1,他引:0
Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L.(alfalfa) grassland biomass carbon and soil organic carbon density(SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period(viz. 0–10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0–10 year. During 0–30 year, the SOCD from 0–100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general. 相似文献
962.
963.
野外调查发现,2010年4月14日青海玉树Ms7.1级地震同震地表破裂带长约65km,破裂带走向为310°,破裂面向NE陡倾,地表破裂带由2部分组成,其中西侧部分长约19km,东侧部分长约30km,两者之间存在约15km的无破裂区。地表破裂以右阶雁行状破裂分布为主要特征,呈现左旋走滑性质,伴随有垂直位移。统计结果显示,同震地表破裂垂直位移 (dv)与水平位移 (dh)的比值在0.13~0.53之间,地貌累积dv与累积dh比值为0.27~0.63。同震dv/dh与地貌dv/dh的相似显示玉树南山的形成和玉树地震具有同样的运动学和动力学性质,玉树南山的形成是地质历史上沿玉树断裂多次类似于玉树地震的地震活动的结果,计算出需要1800~2600次地震才能造成玉树南山的隆升。前人研究本段断层地震复发周期为120~200年,计算出断层开始活动时间不晚于20万~40万年以前。 相似文献
964.
A soil temperature control system was designed for sapling study in alpine region and tested in summer, 2009. The system consisted of a power switch, voltage regulator, microcomputer timer, safety relays, temperature control device, temperature sensors, heating cables, fireproofing plastic pipes (PVC), 108 heavy-duty plastic containers and seedlings. The heating cables were held in six 2-layer PVC frames with 25 cm wide, 320 cm long and 25 cm high and three 1-layer frames with 25 cm wide and 320 cm long for 15°C soil temperature treatment, half of the 2-layer frames were used for 20°C and 25°C soil temperature treatments, respectively. Each of the frames was installed at each of ditches with 30 cm wide, 330 cm long and 30 cm deep in size. 12 seedling containers with 20 cm top diameter, 18cm bottom diameter and 25 cm high were homogenously placed at each of the ditches, and spaces between the containers were filled with natural soil. The system was economic, and could increase soil temperatures obviously and uniformly, the maximal and minimal standard errors of soil temperatures were ±0.28 and ±0.05°C at 10cm depth in the containers within each of all the ditches. In the system, aboveground environment was natural, diurnal and monthly soil temperatures varied with changing air temperature, the research results may be better to know the eco-physiological and growth responses of alpine saplings/seedlings to soil warming than that in greenhouse, laboratory, infrared heat lamp and open top chamber. 相似文献
965.
选取太湖源头和睦桥小流域为研究对象,通过90个点的土壤现场采样及室内化学性质分析,旨在揭示其空间分布规律及相关地貌影响.35个代表性采样点的分析表明,在山区小流域尺度上,多数点位土壤pH值介于4.03~4.62之间,近似正态分布,其空间变异较小,土壤全氮和全磷的空间变异居中,土壤有机质和碱土金属(钾、钠、镁、钙)的空间变异性最大.此外,土壤有机质和全氮还具有一定的空间关联性,相关性系数为0.49.地形地貌对土壤化学性质的影响程度不一:随高程增加,土壤中有机质和全氮的含量明显增加,而高程对土壤pH值、全磷及碱土金属的影响则较小;地形坡度对其空间分布的影响较小,而坡向对土壤养分的空间分布有显著影响,偏西及偏北方向的山坡中土壤有机质、全氮和全磷含量要明显高于偏东和偏南的山坡;最后,山坡曲率对土壤有机质的影响也很显著,发散型山坡以及凹型山坡的土壤有机质含量较高,沿山谷线一带土壤有机质的含量亦较高. 相似文献
966.
强降雨在山地灾害链成灾演化中的关键控制作用 总被引:1,自引:0,他引:1
经历了2009年的干旱后,2010年雨季,中国西部山区山地灾害频繁暴发并演化成灾害链,强降雨起到了关键控制作用。降雨使山地灾害链极大扩展了空间影响范围,加速了演化进程。选取灾害链演化中的滑坡、泥石流两个关键环节,构建力学模型,对降雨的控制激发作用进行分析,分别以贵州关岭滑坡-碎屑流灾害链、甘肃舟曲泥石流-堰塞湖灾害链为典型实例进行验证,最终得出结论:强降雨激发滑坡、泥石流形成的控制作用是通过特殊的水作用机制体现的,久旱强雨是灾害链预警防控的关键时段。 相似文献
967.
流域降雨引起水土流失,影响观光河道水体质量,探讨水体观光影响性降雨特性,对于旅游地水土保持建设和景观资源有效利用具有一定的现实意义。本文以浙江省天台山风景区石梁景区为研究区,通过野外观测,获取流域降雨特性与观光水体浊度数据,借助水体视觉美感和侵蚀性降雨分析,探讨观光影响性降雨的临界值、降雨特性、时空差异及其水色变化规律... 相似文献
968.
969.
970.