A comparison of the effectiveness of the roots of two grass species in reducing soil erosion on alluvial fans in south-east China     

Fangshi Jiang  Kaiwen He  Jiahui Lin  Hui Li  Zhenzhi Zhan  Jinshi Lin  Hongli Ge  Ming Kuang Wang  Yanhe Huang 《水文研究》2020,34(1):96-110

The effects of root systems on soil detachment by overland flow are closely related to vegetation types. The objective of this study was to quantify the effects of two gramineous roots (Paspalum mandiocanum with shallow roots and Pennisetum giganteum with deep roots) on soil detachment capacity, rill erodibility, and critical shear stress on alluvial fans of benggang in south-east China. A 4-m-long and 0.12-m-wide flume was used. Slope steepness ranged from 9% to 27%, and unit flow discharge ranged from 1.39 × 10⁻³ to 4.19 × 10⁻³ m² s⁻¹. The mean detachment capacities of P. mandiocanum and P. giganteum lands were 18% and 38% lower than that of bare land, respectively, and the effects of root on reducing soil detachment were mainly reflected in the 0- to 5-cm soil layer. The most important factors in characterizing soil detachment capacity were root length density and soil cohesion, and soil detachment capacity of the two grass lands could be estimated using flow shear stress, soil cohesion, and root length density (NSE = 0.90). With the increase in soil depth, rill erodibility increased, whereas shear stress decreased. The mean rill erodibilities of P. mandiocanum and P. giganteum lands were 81% and 61% as much as that of bare land, respectively. Additionally, rill erodibilities of the two grass lands could be estimated as an exponential function by root length density and soil cohesion (NSE = 0.88). The mean critical shear stress of P. mandiocanum and P. giganteum lands was 1.29 and 1.39 times that of bare land, respectively, and it could be estimated with a linear function by root length density (NSE = 0.76). This study demonstrated that planting of the two grasses P. mandiocanum and P. giganteum could effectively reduce soil detachment and enhance soil resistance to erosion on alluvial fans, with the deep roots of P. giganteum being more effective than the shallow roots of P. mandiocanum. The results are helpful for understanding the influencing mechanism of root systems on soil detachment process.  相似文献   

短期重现性地磁日变化感应电流集中分布与地震关系初步研究     

冯志生  姜楚峰  冯丽丽  李军辉  戴勇  黄颂  姚丽  章鑫  袁桂平  倪晓寅  戴苗  李鸿宇 《中国地震》2020,36(3):502-516

通过分析台站之间地磁垂直分量日变化相关性,研究中国大陆南北带地区90°E～110°E,2009～2018年地磁日变化感应电流线状集中分布现象与M_S≥6.0地震关系。统计发现,我国每月平均出现约2次感应电流集中分布现象,且10天左右内有原地重复出现现象——感应电流集中分布重叠异常,原地重现的集中分布感应电流日期间隔一般在10天左右以内,原地重现日期一般不连续,重现次数一般仅有2次。研究发现,我国南北带2009～2018年共出现重叠异常23次,20次重叠异常出现后18个月内重叠段发生M_S≥6.0地震,对应率高达87%,地震基本发生在重叠段端部250km以内,重叠段发生2次M_S≥6.0地震的比例较低,约35%;重叠段2个端部均发生M_S≥6.0地震的比例极小,仅约9%。部分重叠段走向与已经发现的上地幔和地壳高导带埋深走向基本一致,推测重叠异常发生在上地幔和地壳高导带附近,是来自上地幔和地壳内高导带附近的地震异常信息。目前已知,中国大陆强地震主要发生在上地幔高导层的隆起区一带及其壳内高导层发育地区,深部电性测深结果表明,大震易于发生在电导率急剧变化的梯度带,但这些地区何时发生地震还未得知,本文发现的重叠异常解释了这些地区1～2年内是否发生地震这一问题。  相似文献   

长江口咸潮入侵变化特征及成因分析     

李文善  王慧  左常圣  董军兴  徐浩  潘嵩  金波文  高通 《海洋学报》2020,42(7):32-40

本文基于海洋站潮位观测数据、海平面变化影响调查信息以及长江口水文站径流量数据等，重点分析了2009?2018年长江口咸潮入侵的变化特征及其影响因素，分析结果表明:(1)长江口咸潮入侵季节变化特征明显。咸潮一般从每年的9?10月开始入侵，翌年4?5月结束。3月咸潮入侵次数最多，达12次。2009?2018年，长江口咸潮入侵次数和咸潮持续时间均呈下降趋势，2009年长江口咸潮入侵次数最多，达13次，时间均发生在10月至翌年的4月；咸潮持续时间年际变化较大，2011年咸潮入侵持续时间最长，累计为55 d。2015?2018年，咸潮入侵次数和入侵持续时间均明显减少，2018年没有监测到咸潮入侵过程。(2) 1?4月，长江口处于季节性低海平面期，且同期径流量少，但是受东亚季风影响，持续的增水过程使得增减水?径流量综合影响指数明显偏高，其中1月、2月、3月的影响指数分别为1.5、1.9和1.6，该时段长江口的咸潮入侵过程主要受增减水的影响。5?7月，长江口径流量明显增加，海平面?径流量综合影响指数均小于0，径流的作用强于海水上溯。8月，长江口径流量开始下降，虽然季节海平面较高，但是长江口呈现明显的减水过程，海平面?径流量和增减水?径流量的综合影响指数分别为0.1和?1.6，基本不会发生咸潮入侵。9月，长江口处于季节高海平面期，并且以增水为主，海平面?径流量和增减水?径流量的综合影响指数较大，分别为1.2和1.0，易发生咸潮入侵。10月、11月长江口海平面?径流量的综合影响指数分别为1.5和0.8，径流影响弱于海水上溯，易发生咸潮入侵。(3) 2009?2018年发生的48次咸潮入侵过程有2/3恰逢天文大潮。在某些年份长江口沿海基础海平面偏高，若持续增水恰逢天文大潮，则加剧咸潮入侵的影响程度。  相似文献   

2018?2019年舟山近海浮游动物群落结构春季年际变化及其与水团的关系   总被引：1，自引：1，他引：0  

王慧君  许永久  俞存根  章寒  张洪亮  蒋日进  梁君  郭爱  朱文斌  徐开达  刘连为  王皓学 《海洋学报》2020,42(6):90-100

根据2018?2019年春季两个航次在舟山近海进行的浮游生物调查结果，对舟山近海的浮游动物群落结构(类群组成、优势种数量)年际变化进行了研究，利用典范对应分析(Canonical Correspondence Analysis, CCA)研究了两年春季浮游动物类群组成差异、优势种变化的原因，初步探讨了春季浮游动物群落结构动态变化的机制。结果表明:根据表层温度(Sea Surface Temperature，SST)、表层盐度(Sea Surface Salinity，SSS)的聚类分析，将该区域分为3个水团:杭州湾内水团(I区)、舟山本岛上升流水团II区)、舟山近海水团(III区)。不同水团对浮游动物类群组成影响显著，引起2018年和2019年春季3个水团区差异的主要贡献种(贡献率>10%)均为中华哲水蚤，同一水团两年间年际差异的贡献种如下:I区为捷氏歪水蚤(56.91%)和真刺唇角水蚤(12.34%)；II区为中华哲水蚤(72.64%)、五角水母(13.35%)；III区为中华哲水蚤(41.93%)、夜光虫(22.94%)。CCA分析表明，第1 CCA轴(CCA1)和第2 CCA轴(CCA2)共解释了两年春季浮游动物优势种累计方差的46.14%和物种?环境累计方差的97.82%。CCA1主要反映了空间(近海水团和湾内水团)的差异。CCA2主要反映了2018年和2019年站位的年际差异。盐度是影响春季浮游动物群落结构空间差异的主要因素，而温度、叶绿素a浓度是春季浮游动物群落结构年际差异的主要因素。  相似文献   

2017年春夏季西北太平洋浮游植物的区域差异及其与不同水团的关系   总被引：2，自引：0，他引：2  

林更铭  陈杨航  黄奖  王彦国  叶又茵  杨清良 《海洋学报(英文版)》2020,39(6):107-118

The West Pacific Ocean is considered as the provenance center of global marine life and has the highest species diversity of numerous marine taxa. The phytoplankton, as the primary producer at the base of the food chain,effects on climate change, fish resources as well as the entire ecosystem. However, there are few large-scale surveys covering several currents with different hydrographic characteristics. This study aimed to explore the relationships between the spatio-temporal variation in phytoplankton community structure and different water masses. A total of 630 water samples and 90 net samples of phytoplankton were collected at 45 stations in the Northwest Pacific Ocean(21.0°–42.0°N, 118.0°–156.0°E) during spring and summer 2017. A total of 281 phytoplankton taxa(5 μm) belonging to 61 genera were identified in the study area. The distribution pattern of the phytoplankton community differed significantly both spatially and temporally. The average abundances of phytoplankton in spring and summer were 797.07×10~2 cells/L and 84.94×10~2 cells/L, respectively. Whether in spring or summer, the maximum abundance always appeared in the northern transition region affected by the Oyashio Current, where nutrients were abundant and diatoms dominated the phytoplankton community;whereas the phytoplankton abundance was very low in the oligotrophic Kuroshio region, and the proportion of dinoflagellates in total abundance increased significantly. The horizontal distribution of phytoplankton abundance increased from low to high latitudes, which was consistent with the trend of nutrient distributions, but contrary to that of water temperature and salinity. In the northern area affected by the Oyashio Current, the phytoplankton abundance was mainly concentrated in the upper 30 m of water column, while the maximum abundance often occurred at depths of 50–75 m in the south-central area affected by the Kuroshio Current.Pearson correlation and redundancy analysis(RDA) showed that phytoplankton abundance was significant negatively correlated with temperature and salinity, but positively correlated with nutrient concentration. The phytoplankton community structure was mainly determined by nutrient availability, especially the N:P ratio.  相似文献   

SMAP卫星海表盐度产品的检验与校正     

秦思思  王辉  朱江  万莉颖  张宇  王昊运 《海洋学报(英文版)》2020,39(3):148-158

In this study, sea surface salinity(SSS) Level 3(L3) daily product derived from soil moisture active passive(SMAP)during the year 2016, was validated and compared with SSS daily products derived from soil Moisture and ocean salinity(SMOS) and in-situ measurements. Generally, the root mean square error(RMSE) of the daily SSS products is larger along the coastal areas and at high latitudes and is smaller in the tropical regions and open oceans. Comparisons between the two types of daily satellite SSS product revealed that the RMSE was higher in the daily SMOS product than in the SMAP, whereas the bias of the daily SMOS was observed to be less than that of the SMAP when compared with Argo floats data. In addition, the latitude-dependent bias and RMSE of the SMAP SSS were found to be primarily influenced by the precipitation and the sea surface temperature(SST). Then, a regression analysis method which has adopted the precipitation and SST data was used to correct the larger bias of the daily SMAP product. It was confirmed that the corrected daily SMAP product could be used for assimilation in high-resolution forecast models, due to the fact that it was demonstrated to be unbiased and much closer to the in-situ measurements than the original uncorrected SMAP product.  相似文献   

A motion planning algorithm for the feed support system of FAST     

姚蕊  姜鹏  孙京海  于东俊  孙纯 《天文和天体物理学研究(英文版)》2020,(5):117-126

The paper relates to a motion planning algorithm for the feed support system of the Five-hundred-meter Aperture Spherical radio Telescope(FAST).To enhance the stability of the feed support system,the start/termination planning segments are adopted with an acceleration and deceleration section.The source switching planning adopts a combination of a line segment and focal segment to realize stable control of the feed support system.Besides,during the observation trajectory,a transition segment which is not used for observation data is planned with a required time.Through an example simulation,a smooth change is realized via the motion planning algorithm and presented in this paper.  相似文献   

Intraguild predation by polyps of three scyphozoan jellyfish: Nemopilema nomurai,Aurelia coerulea,and Rhopilema esculentum     

Tang  Changsheng  Sun  Song  Zhang  Fang 《中国海洋湖沼学报》2020,38(6):1755-1761

Journal of Oceanology and Limnology - Jellyfish blooms occur worldwide and have resulted in serious problems in tourism, fisheries, coastal industries, and the marine ecosystem. The life cycle of...  相似文献   

地震观测仪器自动监控软件设计与实现     

姜佳宁  吴利军  徐磊  赵祖虎  方宏 《地震地磁观测与研究》2019,40(4):167-175

结合地震地球物理观测台网台站监测工作实际，研制一款地震观测仪器自动监控软件。该软件适用于不同网络环境下IP类仪器设备的网络实时或定时自动监控，地球物理观测类仪器时钟、状态和观测数据的定时自动监控，能自动识别当日观测数据中的无效数据、变幅异常、干扰、地震和限幅等信息，无需借助其他硬件和软件即可将告警信息以短信方式发送给值班人员和管理人员，可实现对仪器原始观测数据的自动备份和手动恢复，及对仪器的一键重启和校正时钟等控制类操作，无需跨平台操作即可查看当日观测数据曲线及分析数据的完整性和有效性，从而实现对仪器的统一高效管理。  相似文献   

Global Statistical Assessment and Cross-Calibration with Jason-2 for Reprocessed HY-2 A Altimeter Data     

Maofei Jiang  Ke Xu  Yalong Liu 《Marine Geodesy》2018,41(3):289-312

HY-2 A (Haiyang-2 A) satellite was launched on August 16, 2011 and radar altimeter is one of its main payloads. We reprocessed two years of HY-2 A altimeter sensor geophysical dataset records (SGDR) data. This paper presents the main results in terms of reprocessed HY-2 A altimeter data quality: verification of data availability and validity, monitoring several relevant altimeter parameters, and assessment of the HY-2 A altimeter system performances. A cross-calibration analysis of reprocessed HY-2 A altimeter data with Jason-2 was conducted. The reprocessed HY-2 A altimeter data show good quality and have a low level of noise with respect to Jason-2. The same geophysical correction methods were used to calculate the sea surface height (SSH) for the two missions. The mean standard deviations of the crossover differences for HY-2 A and Jason-2 are 5.24 cm and 5.34 cm, respectively. The mean standard deviation of the crossover differences between HY-2 A and Jason-2 is 5.37 cm. These show that HY-2 A can provide SSH measurements at almost the same level of accuracy as Jason-2. The relative SSH bias between HY-2 A and Jason-2 due to the Ultra Stable Oscillator (USO) drift is obviously observed, and it can affect the calculation of mean sea level and should be further studied and corrected.  相似文献