Species diversity and regeneration of native species in Pennisetum ciliare (buffelgrass) pastures from the thornscrub of Sonora,México

To examine the influence of buffelgrass land conversion and pasture management on native species diversity and regeneration patterns, we describe community attributes and population structure in four different active pastures in thornscrub vegetation from eastern Sonora, Mexico. We compare a relatively undisturbed thornscrub community with a contiguous five years old active pasture, to identify species able to regenerate under current management practices. Buffelgrass conversion has a significant influence on species diversity and other community attributes. Active pastures have lower species diversity, crown cover and basal area of native species than the studied native thornscrub. An active pasture subjected to heavy grazing and without management of the thorny legume, Acacia cochliacantha, showed the lower species diversity and an almost monospecific stand of this legume. It is likely that the reduction in species diversity is caused by the conversion process, inadequate management and regeneration barriers that limit seedling establishment in active pastures. Our data recorded eight native species (13%) that were able to regenerate in active pastures. However, the great majority of native species were unable to regenerate under pastures. This study shows that under current management, active buffelgrass pastures maintain only a small fraction of native species with regenerating populations in the thornscrub.     

�ռ�Բ�������ⷽ�������ݴ���

???????????????????????????????????:λ????????????????????λ?????????????????????????????????;??????????????????????????????????????????????????????????????????????????????????????????????????????3????????????:???????????????????????????????????????÷??????н?????????     

牡丹江地震台形变数据快速转换软件

采用VB6.0编制形变数据快速转换软件,可以将epd格式的形变数据转换成Mapsis所要求的格式,便于研究人员使用.牡丹江地震台形变数据快速转换软件已在牡丹江地震台调试通过,使用效果较好,便于推广应用.     

Migration of volatile organic contaminations (VOCs) through a deforming clay liner

A fully coupled thermal–hydraulic–mechanical–chemical (THMC) model was proposed to describe the migration of volatile organic contaminations (VOCs) in unsaturated landfill liners. The vertical soil stress, capillary pressure, air pressure, temperature increase, and solute concentration were selected as the primary variables. Finite deformations were described using Lagrangian coordinates. Non-isothermal moisture transport was found to be dependent on both the temperature gradient and the concentration of the VOCs. The VOCs were assumed to exist and be transported in three phases in the soil: solid, liquid, and gas. An illustrative example of an unsaturated landfill with a compacted clay liner was presented. For the case considered, the transport of gas phase VOCs was found to dominate the migration progress. Moreover, the temperature gradient can accelerate the breakthrough of VOCs in an unsaturated liner, while the mechanical consolidation slowed down the motion of the VOCs.     

Contribution to the Global Warming Mitigation of Marshlands Conversion to Croplands in the Sanjiang Plain,Northeast China

Based on the estimation of greenhouse gases (GHG) emissions and carbon sequestration of the total conversion of marshlands (TMC), marshlands conversion to paddy fields (MCPFs) and marshlands conversion to uplands (MCULs), this study revealed the contribution to the global warming mitigation (CGWM) of paddy fields versus uplands converted from marshlands in the Sanjiang Plain (excluding the Muling‐Xingkai Plain on south of Wanda Mountain), Heilongjiang Province, northeast China. The results showed that the total area of MCPFs and MCULs was 504.23 × 10³ ha between 1982 and 2005. The CGWM per unit area was 45.53 t CO₂eq/ha for MCPFs and that was 23.95 t CO₂eq/ha for MCULs, with an obvious 47.40% reduction. The MCPFs and MCULs ecosystems acted as the carbon sink all of the year. As far as CGWM per unit area is concerned, MCPFs mitigated the greenhouse effect which was greater than MCULs. And it was effective that the implementation of the uplands transformed into paddy fields in Northeast China with regard to marshlands protection and croplands (including paddy fields and uplands) reclamation.     

MATLAB在GPS定位坐标系统模拟中的应用

针对在GPS定位坐标系统中进行精密计算的复杂性,通过使用MATLAB来处理协议天球坐标系的定义及转换问题,以此来确定GPS卫星星座在天球坐标系中的具体位置。通过使用MATLAB来模拟其原理及计算过程,可大幅度提高GPS定位坐标系统中的计算速度以及精度。     

全站仪数据格式转换程序设计与实现

在分析数据存储文件格式的基础上,设计了数据的读取算法,对观测数据进行自动化识别,生成标准记录格式的观测数据文件和CASS通用编码格式的展点数据文件,从而减轻了内业数据处理工作量,提高了工作效率。     

清华山维EPSEM房产空间管理系统转换亿图软件的技术实现方案

介绍了当前福州市更新房地产信息管理软件亿图软件,由存量房产测绘成果转换到亿图软件带来的问题,提出了利用C#及AutoCAD的二次开发工具ObjectARX开发技术解决这些问题的方法并进行了总结。     

基于多模GNSS接收机的卫星系统完好性监测

为了满足多卫星系统完好性监测的需要,本文通过对比不同卫星系统定位结果的方法来监测各个卫星系统的可用性。利用上述方法对实测的三模(GPS、GLONASS和COMPASS)数据进行了处理,结果表明该方法具有可行性,可为多模GNSS接收机的自主完好性监测提供参考信息。     

农村集体土地使用权调查坐标系统的选择

河南省农村集体土地建设用地和宅基地使用权调查已逐步开始,全省统一布设D,E级GPS控制网作为农村集体土地使用权调查的基础控制,采用国家A,B级GPS点和河南省C级GPS点作为起算数据。本文阐述各地级市的市区、县域建立农村集体土地使用权调查坐标系统的方法和采用的起算数据及与历史地籍资料坐标系统的转换原理与方法。