Denitrification potential of marsh soils in two natural saline-alkaline wetlands     

Junhong Bai  Qingqing Zhao  Junjing Wang  Qiongqiong Lu  Xiaofei Ye  Zhaoqin Gao 《中国地理科学(英文版)》2014,24(3):279-286

Little information is available on denitrification potential of marsh soils in natural saline-alkaline wetlands. The denitrification potentials of an open wetland in the floodplain(Erbaifangzi wetland) and a closed wetland(Fulaowenpao wetland) in backwater areas in Jilin Province of Northeast China were monitored by an anaerobic incubation at 30℃ for 25 days. Our results showed that the relative denitrification index(RDI) increased gradually with incubation time, and showed a rapid increase in the first 5 days of incubation. The RDI values declined quickly from surface soils to subsurface soils and then kept a small change in deeper soils along soil profiles over the incubation time. Denitrification proceeded much faster in the top 20 cm soils of open wetland than in the closed wetland, whereas no significant differences in RDI values were observed in deeper soils between both wetlands. The RDIs were significantly negatively correlated with bulk density and sand content, while a significantly positive correlation with clay content, soil organic matter, total nitrogen and phosphorous. The maximum net NO–3-N loss through denitrification in 1 m depth were higher in the open wetland than the closed wetland with higher soil pH values. Future research should be focused on understanding the influencing mechanisms of soil alkalinity.  相似文献   

A landscape pattern analysis method based on boundaries and nodes: A case study in upper Minjiang River, China     

Qingchun Wen  Xiuzhen Li  Hongshi He  Yuanman Hu  Xin Chen  Yu Chang  Wei Wang  Rencang Bu 《中国地理科学(英文版)》2014,24(1):50-59

Traditionally,patch-based analysis at the landscape scale fragmentation has been used in the study of landscape ecology while the study of boundary and node has not been considered as much detail until recently.This study investigated the possibility of applying boundary-and node-based methods in landscape pattern analysis to the upper reaches of the Minjiang River in the southwestern China.Boundary-based and node-based landscape indices were selected to be used in analyzing changes in landscape patterns,and the results were compared with analysis using traditional pattern indices.We compared the responses of patch-area-based,boundary-length-based and node-number-based indices,and concluded that boundary-based and node-based indices are more sensitive to disturbance than patch-based indices with various patterns,and node-based indices are even more sensitive than boundary-based ones.Thus,the results suggest that boundary-based and node-based pattern analysis methods provide helpful supplementary information to traditional patch-based pattern analysis methods.The results about pattern dynamics of landscapes in the upper reaches of the Minjiang River based on boundaries and nodes showed that with human disturbance,the dominance of forest landscape was weakened by other landscape types; thus the landscape pattern of the study area became more homogeneous and the boundary network became more complex.These changes further augmented disturbance interfaces in the landscape and increased the possibilities of further landscape fragmentation.  相似文献   

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尼胜楠  陈剑利  李进  陈超  梁青 《大地测量与地球动力学》2014,34(4):49-55

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������  ������  �ŷ� 《大地测量与地球动力学》2014,34(6):37-40

???1999??2012???????????????????????????????λ????????????????????????λ??????GPS??????????????????????仯?????????о?????????????λ??GPS????????仯??????????????????仯?????????????????????????????????????λ????????GPS?????????С????ζ??????????????????????λ???????GPS?????????????ζ??????3??????????λ?仯????GPS????????????????г????????  相似文献   

大伙房库区近30年来植被覆盖变化分析   总被引：1，自引：0，他引：1  

迟瑶  王艳慧  王崇 《地理信息世界》2014,(6)

根据像元二分模型原理,利用1983年、2000年、2011年大伙房库区遥感影像数据提取植被覆盖遥感信息,结合植被指数计算植被覆盖度,分析比较大伙房库区不同时期植被覆盖的变化,研究大伙房库区这三个时期植被覆盖动态变化规律,为大伙房库区的生态建设和可持续发展提供决策支持。结果显示:1近30年以来,大伙房库区植被覆盖等级分布不均衡,高植被覆盖区过分集中在北部地带,西部则多为低植被覆盖区;2大伙房库区高植被覆盖面积在减少、低植被覆盖面积在增加;3大伙房库区植被覆盖总面积在下降,库区的生态环境已经遭到了破坏;4政策建议:加强监测与监管力度,合理开发利用矿产资源,积极响应国家"退耕还林、退耕还草"号召。  相似文献   

The formation of wind curl in the marine atmosphere boundary layer over the East China Sea Kuroshio in spring     

Suping Zhang  Yang Kong 《中国海洋大学学报(英文版)》2014,13(6):883-892

Various data are used to investigate the characteristics of the surface wind field and rainfall on the East China Sea Kuroshio (ESK) in March and April, 2011. In March, the wind speed maximum shows over the ESK front (ESKF) in the 10 meter wind field, which agrees with the thermal wind effect. A wind curl center is generated on the warm flank of the ESKF. The winds are much weaker in April, so is the wind curl. A rainband exists over the ESKF in both the months. The Weather Research and Forecasting (WRF) model is used for further researches. The winds on the top of the marine atmosphere boundary layer (MABL) indicate that in March, a positive wind curl is generated in the whole MABL over the warm flank of the ESKF. The thermal wind effect forced by the strong SST gradient overlying the background wind leads to strong surface northeasterly winds on the ESKF, and a positive shearing vorticity is created over the warm flank of the ESKF to generate wind curl. In the smoothed sea surface temperature experiment, the presence of the ESKF is responsible for the strong northeast winds in the ESKF, and essential for the distribution of the rainfall centers in March, which confirms the mechanism above. The same simulation is made for April, 2011, and the responses from the MABL become weak. The low background wind speed weakens the effect of the thermal wind, thus no strong Ekman pumping is helpful for precipitation. There is no big difference in rainfall between the control run and the smooth SST run. Decomposition of the wind vector shows that local wind acceleration induced by the thermal wind effect along with the variations in wind direction is responsible for the pronounced wind curl/divergence over the ESKF.  相似文献   

Warmer-Get-Wetter or Wet-Get-Wetter? A Criterion to Classify Oceanic Precipitation     

Chengcheng Qian  Ge Chen 《中国海洋大学学报(英文版)》2014,13(4):552-560

In this study, the temporal and spatial variations of observed global oceanic precipitation during 1979–2010 are investigated. It is found that the global trend in precipitation during this period varies at a rate of 1.5%/K of surface warming while the rate is 6.6%/K during 2006–2010. The precipitation is highly correlated with Sea Surface Temperature(SST) in both the temporal and the spatial patterns since the strong 1997–98 El Nino event. Considering the distributions of precipitation and SST, seven oceanic regions are classified and presented using the observed Global Precipitation Climatology Project(GPCP) data and Extended Reconstructed Sea Surface Temperatures, version 3(ERSST.v3) data. Further examining the mechanisms of the classified oceanic precipitation regions is conducted using the Tropical Rainfall Measuring Mission(TRMM) satellite, GFDL-ESM-2G model precipitation and SST data and Hadley Center sea ice and SST version 1(Had ISST1) data. More than 85% of global oceanic precipitations are controlled by either one or both of the warmer-get-wetter mechanism and wet-get-wetter mechanism. It is estimated that a 0.5 SST signal-to-noise ratio, representing the trend of SST time series to the standard deviation, is a criterion to distinguish the mechanism of a region. When the SST ratio is larger than 0.5, the precipitation of this region is controlled by the warmer-get-wetter mechanism. SST, rather than the humidity, is the pivotal factor. On the other hand, when the SST ratio is less than 0.5, the precipitation is controlled by the wet-get-wetter mechanism. The SST variability is a significant factor contributing to the precipitation variation.  相似文献   

长三角盛夏—初秋强降水的延伸期过程预报探析   总被引：1，自引：1，他引：0  

信飞  陈伯民  孙国武  王超 《气象科学》2014,34(6):672-677

针对长三角汛期强降水过程,根据不同降水类型的特性,提出分时段建立低频模型并给出建模流程。综合分析长三角汛期强降水期的低频特性,将低频气旋及反气旋区分划分7个关键区。重点研究盛夏—初秋时段的强降水特征,在总结强降水期低频特征的基础上,借助EOF分解建立延伸期大—暴雨的预报模型:1区或2区有低频气旋维持并发展;6区、7区或5区存在低频反气旋。并且在7个关键区中1、2区的低频气旋及5、6、7区的低频反气旋为主要低频系统,起决定作用,而3区的低频系统为次要低频系统,起辅助作用。利用该模型提前30 d预报出2012年汛期最强降水过程,并分析本次过程的低频系统演变,给出动态演变模型。  相似文献   

Optimal Forward-Scattering Angles of Atmospheric Aerosols in North China          下载免费PDF全文

JIA Sheng-Jie  Lü Da-Ren 《大气和海洋科学快报》2014,(3):236-242

The accurate understanding of atmospheric aerosol extinction coefficients is very important for at- mospheric science research. To achieve a fast and simple method for determining the parameters, the selection of optimal forward-scattering angles of atmospheric aerosols is required. In this paper, the authors introduce the detec- tion basis of forward-scattering of atmospheric aerosols, and the authors verify the sensitivity of the phase function to the real part of the complex refractive index. The au- thors use the Jaenicke urban aerosol model to determine that forward-scattering angles near 33° are suitable. However, the optimal forward-scattering angles in North China are between 37° and 40°. Numerical simulation shows that certain types of particle size distribution of newly generated particles and pollution have limited in- fluences on the selection of forward-scattering angles. But the ranges of these insensitive angles shift - 10 degrees for dust intrusion, and the relative deviations of the phase function are less than 5.0% within extra angles of 0° to 3°. This study can serve as a reference for the selection of optimal forward-scattering angles for visibility meters and Present Weather Identifiers （PWIs） in addition to the de- tection of forward-scattering optical properties.  相似文献   

火箭人工增雨作业中应注意的一些技术问题   总被引：1，自引：0，他引：1  

徐冬英 《气象研究与应用》2014,35(3):85-89

根据火箭增雨作业的原理对催化剂播撒量、成核率与火箭飞行速度和高度的关系进行分析;确定作业目标、时机和部位、作业火箭用量;对增雨效果、火箭播云对环境的影响进行评估。  相似文献