Physiological responses and adjustment mechanisms of the dominate species of natural vegetation of Eastern Tengger Desert     

HaiYan Zhou  HuiJuan Tan  ZhiShan Zhang  XiaoHong Ji  HengWen Fan  JianLi Yuan 《寒旱区科学》2010,2(5):0455-0463

Reaumuria soongorica and Salsola passerina have significant differences in ecophysiological characteristics, which change with the environmental variations. Although they live together for a long period of time, their adaptive mechanisms to environmental stresses are very different. As two extreme xerophytes, Reaumuria soongorica and Salsola passerina differ significantly from other psammophytes in ecophysiological characteristics; they can survive in lower water potential, and can even grow in piedmont areas. Low water potential may be related to the existence of osmosis-regulating substance, such as praline, which can strengthen the capacity of water absorption. Compared to other psammophytes, Reaumuria soongorica and Salsola passerina have a higher degree of photo-inhibition under the same condition, and the photo-inhibition can lead to destruction of the photosynthetic pigment, nevertheless, this photo-inhibition can be repaired under suitable conditions in the morning and evening.  相似文献   

Numerical Simulation of the 1999 Yangtze River Valley Heavy Rainfall Including Sensitivety Experiments with Different SSTA     

GUO Yufu  WANG Ji  ZHAO Yan 《大气科学进展》2004,21(1):23-33

With the IAP/LASG GOALS model,the heavy rainfall of the summer of 1999 in the Yangtze River valley is simulated with observational sea surface temperature (SST).Comparing the simulations of 1999 with the corresponding ones of 1998 and the sensitivity experiments with different sea surface temperature anomalies (SSTA) at different ocean regions,the relationships between the floods in the Yangtze River valley and the SSTA in the Pacific and Indian Oceans are studied.The results show that the positive SSTAin the tropical Indian Ocean are a major contributor to the heavy rainfall and may be a very important index to predict the heavy rainfall over the Yangtze River valley in the summer.The simulations also show that the relationships between the SSTA in the tropical eastern Pacific and the heavy rainfall in the Yangtze River valley are very complicated,and the heavy rainfall in the Yangtze River valley can occur in both a decaying and an intensifying El Ninio event and also in a La Nina event.However,the different SSTA of different periods in the above three cases play different parts.  相似文献   

Thermoluminescence Dating of Colluvial Deposits and Its Application to Chronological Study of Paleoearthquakes     

Ji Fengju  Li JianpingInstitute of Geology  CSB  Beijing  China 《中国地震研究》1999,(4)

On the basis of studies of lithofacies features of colluvial deposits, applicability of thermoluminescence dating of the colluvial deposits at different lithofacies positions, and reliability of the dating result, the thermoluminescent ages of colluvial deposit from different types of faults were determined. From the above, the ages of paleoseismic events and their recurrence intervals on the related fault were deduced.  相似文献   

A Review of Seismicity in the First Half of 2018     

Zhai Luyuan  Ji Yun  Jiang Xianghu  Yang Chen  Lu Jinglin 《中国地震研究》2018,32(3):442-446

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Comparative Study on Two Methods for Measuring Wave Velocity Change of Crustal Medium Based on Large Volume Airgun Excitation Data     

YE Beng  CAO Wenzhong  HUO Yuanhang  CHEN Ji  LI Xiaobin 《中国地震研究》2019,33(4):584-595

This paper proposes the application of dynamic programming method to calculate the relative change of wave velocities and compares its similarities and differences with the cross-correlation delay estimation method based on interference. The results show that:①the trend of wave velocities obtained by cross-correlation method and dynamic programming method are consistent. Besides,it is considered that the calculated result using cross-correlation delay method is reliable.② Compared with the cross-correlation delay method,the calculated result of the dynamic programming method has a magnifying effect and is more sensitive to small disturbances.③ Under ideal conditions,the wave velocity change trend calculated by P-wave and S-wave phase should be consistent. In addition,the cross-correlation delay method is used to calculate the wave velocity change.Under appropriate conditions,the process of recovering from the suspected wave velocity before the M_L1. 1 earthquake near the airgun source can be observed.  相似文献   

Modeling N2O Emissions from Agricultural Fields in Southeast China     

Gou Ji  Zheng Xunhu  Wang Mingxing  Li Changsheng 《大气科学进展》1999,16(4):581-592

DNDC, a rainfall-driven and process-oriented model of soil carbon and nitrogen biogeochemistry, is applied to simulate the nitrous oxide emissions from agricultural ecosystem in Southeast China. We simulated the soil N₂O emission during a whole rice-wheat rotation cycle (from Nov. 1, 1996 to Oct. 31, 1997) under three different conditions, which are A) no fertilizer, B) both chemical fertilizer and manure and, C) chemical fertilizer only. The processes of N₂O emission were discussed in detail by comparing the model outputs with the results from field measurement. The comparison shows that the model is good at simulating most of the N₂O emission pulses and trends. Although the simulated N₂O emission fluxes are generally less than the measured ones, the model outputs during the dryland period, especially during the wheat reviving and maturing stages in spring, are much better than those during the paddy field period. Some sensitive experiments were made by simulating the N₂O emissions in spring, when there is a smallest gap between the simulated fluxes and the measured ones. Meanwhile, the effects of some important regulating factors, such as the rainfall, N deposition by rainfall, temperature, tillage, nitrogen fertilizer and manure application on N₂O emission during this period were analyzed. From the analysis, we draw a conclusion that soil moisture and fertilization are the most important regulating factors while the N₂O emission is sensitive to some other factors, such as temperature, manure, tillage and the wet deposition of atmospheric nitrate.  相似文献   

云南腾冲火山旅游景观探讨     

李志群  任治  张泰身 《地质论评》1999,45(7):940-945

腾冲火山活动始于上新世,形成橄榄玄武岩、安山玄武岩、安山 岩及英安岩4大类,分为两个喷发旋回,4个喷发期。主要景观由全新世的第四期火山机构组成,景观分为火山锥、熔岩被、火山地热、火山与热水观赏石等。岩石属高钾钙碱性火山岩系,是挤压造山带的产物。腾冲火山群深部存在熔融岩浆囊,是休眠火山,但岩浆囊内绝大部分岩浆已喷发。结合人文景观,腾冲火山群是不可多得的科学考察和旅游景区。  相似文献   

Using radium isotopes to quantify submarine groundwater discharge at different scales in the Huanghe River Estuary,China     

Haowei Xu  Disong Yang  Xiaoyi Guo  Maosheng Gao  Guangquan Chen  Diansheng Ji  Shengtao Chen  Huaming Yu  Bochao Xu 《海洋学报(英文版)》2023,(8):32-39

As an important land-ocean interaction process, submarine groundwater discharge(SGD) is composed of multiple dynamical processes at different scales and plays an important role in the study of coastal ocean geochemical budgets. However, most of the existing studies focus on the quantification of the total groundwater discharge, few studies are about the differentiation and quantification of groundwater discharge processes at different scales(i.e., short-scale SGD and long-scale SGD). As a world-...  相似文献   

Effect of aluminium dust on secondary organic aerosol formation in m-xylene/NO_x photo-oxidation     

LIU Chang  MA Qing Xin  CHU Bi Wu  LIU Yong Chun  HE Hong  ZHANG Xiao Ye  LI Jun Hua  HAO Ji Ming 《中国科学:地球科学(英文版)》2015,(2):245-254

As an important anthropogenic volatile organic compound(VOC), m-xylene has attracted numerous attentions due to its potential in secondary organic aerosol(SOA) formation. In this study, effects of aluminium dust seeds(boehmite and alumina) on SOA yield and aerosol size in m-xylene/NOx photo-oxidation were investigated in a 2 m3 smog chamber at 30°C and 50% relative humidity. Compared to the seed-free system, the presence of aluminium seeds resulted in an increase in the SOA yield, and also enhanced the O3 concentration in the chamber. The photolysis of O3 is a major source of OH radical, which is the most important oxidant of m-xylene. The increase in O3 concentration could result in the generation of more OH radicals, and finally contribute to the SOA formation. Seed particles influence the SOA size mainly by acting as condensation nuclei. Semi-volatile organic compounds(SVOCs) were condensed onto these nuclei, resulting in the increase in SOA size. However, when aluminium seeds with high concentrations were introduced into the system, SVOCs that had been condensed onto each particle were dispersed by these seeds, leading to the reduction in aerosol size.  相似文献   

A New Species of the Ankylosaurid Dinosaur Crichtonsaurus (Ankylosauridae: Ankylosauria) from the Cretaceous of Liaoning Province, China     

Lü Junchang  Ji Qiang  GAO Yubo  Li Zhixin 《《地质学报》英文版》2007,81(6):883-897

A new ankylosaurid species of Crichtonsaurus, C. benxiensis sp. nov., is erected based on a well preserved skeleton and a nearly complete skull found in the Sunjiawan Formation (Cenomanian–Turonian), Beipiao, Liaoning Province. Crichtonsaurus benxiensis sp. nov. is characterized by width 84.6% of length of the skull, a deep depression located medial to the notch between the orbit and the squamosal horn, paroccipital processes fused to the quadrates, fused scapula and coracoid, a large foramen for the supracoracoid nerve to enter the coracoid and to exit out from the scapula. Based on the new specimen, Crichtonsaurus is assigned to Ankylosauridae.  相似文献