A spectral index to monitor the head-emergence of wheat in semi-arid conditions

Harvesting wheat (Triticium aestivum L.) for forage or leaving it for grain is the main decision uncertainty growers face in semi-arid regions during mid-season. To facilitate decision-making, a decision support system (DSS) has recently been proposed that requires information about crop water and nutritional status during spike emergence. Though remote sensing has been used to provide site-specific crop status information, a spectral vegetation index is needed to ensure that the information has been acquired during spike emergence. The objective of this study was to propose a spectral index sensitive to spike emergence and validate its suitability across different commercial farm fields by using ground spectral measurements and multispectral satellite imagery. To develop the index, controlled experiments with commonly grown wheat varieties were conducted during the 2004/2005 and 2005/2006 growing season in the agricultural area of the northern Negev desert of Israel. The experiments showed that spike emergence correlated most strongly (r = 0.7, p < 0.05) with spectral changes near the 1.2 μm water absorption feature in contrast to the band at 1.1 μm which appeared to be only weakly correlated. Thus, the spike emergence sensitive band at 1.2 μm has been combined with the insensitive band at 1.1 μm as reference to form the ratio-based normalized heading index (NHI). Experimental data were then used to establish an index threshold that helps separate data acquired before and after spike emergence. The proposed NHI was able to identify spike emergence with a classification accuracy varying between 53 and 83%. Accuracy was influenced by season, and whether narrow or broad spectral bands were used. Validation of the index in commercial farm fields in Israel and the United States showed that the classification accuracy was similar for ground spectral measurements and the advanced land imager (ALI) satellite imagery. These results suggest that the NHI is suited for identifying the onset of heading throughout wheat-growing areas without the need for characterizing seasonal trends.     

Early establishment of broadleaved trees after logging of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> and <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> plantations with different understory treatments

We studied the effects of the amount of advanced regeneration before logging and different understory treatments on forest recovery, particularly the establishment of lucidophyllous (evergreen broadleaved) species, following the logging of conifer plantation with a focus on the sprouting ability. The establishment of lucidophyllous tree and shrub species originating from advanced regeneration was closely related to the total amount of these elements in the advanced regeneration, regardless of understory treatment. The understory-left treatment could preserve understory as surviving individuals by high proportion (60% or more of the understory) compared with the understory-cleared practice after logging. However, half of the surviving individuals were damaged to some extent by logging and skidding. Relatively large trees were likely to survive with no damage, indicating that they face a lower risk than smaller trees. In understory-cleared stands, a high proportion (60% or more) of the understory regenerated by resprouting. However, the resprouting ratio depended on tree size and species. Therefore, as well as the amount of the understory, the tree size of understory before logging would be also an important factor for early forest recovery. Further, the infrequent (low-density) species could easily disappear after logging because of their low resprouting ratio and low density. Thus, recovery from resprouting alone would risk simplification of the species composition after logging. We concluded that leaving the developed understory intact before logging can enhance the speed and biodiversity of forest recovery.     

桑树枝条长度与条重、叶重关系的数学模型探讨

探讨了桑树枝条长度与条重、叶重之间的数学模型 ,包括枝条长与枝条重、片叶重、条叶重之间的关系式 ,以及条长比与条重比、叶重比之间的关系式     

Integration of geospatial and cattle nutrition information to estimate paddock grazing capacity in Northern US prairie

Spatiotemporal variability in forage quantity and quality requires that regular assessment is needed of the capacity for grasslands to support livestock nutritional requirements. Current methods for estimating grazing capacity are typically production-based and lack the forage quality data necessary to match nutrients in forage with livestock requirements in real time. This paper describes a method for estimating short-term grazing capacity for small (1–20 ha) paddocks using cattle nutrition and high spatial resolution forage data in Geographic Information Systems (GIS) for mixed-grass prairie. We define grazing capacity as the number of days a specific paddock will support the nutritional requirements of beef cattle. We integrate previously published methods for estimating cattle nutritional requirements, forage quality (crude protein) and forage quantity (phytomass) to estimate grazing capacity based on current standing-crop. The model utilizes high-resolution (<30-m) satellite imagery or field data to estimate short-term grazing capacity for small paddocks. Three versions of the model were evaluated on one paddock under cattle use in 2007. One version was parameterized using data collected on June 22 from the Landsat Thematic Mapper (TM), one version was parameterized using data collected June 23 from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and one version was parameterized using data collected June 20 from field clippings. TM and ASTER versions underestimated grazing capacity by four days while the field version overestimated grazing capacity by one day. Results suggest integration of cattle nutrition and forage data in GIS could assist with stocking rate adjustments, but additional trials are needed.     

生态因子与烤烟中性挥发性香气物质的关系研究

研究生态因子与烤烟中性挥发性香气物质的关系,结果表明:海拔高度、年有效积温、年日均温、种植期均温和无霜期对类胡萝卜素降解产物都有促进作用,年日照时数和年降水量与其存在二次抛物线关系;芳香族氨基酸类物质与生态因子中的温度条件间相关关系不显著,而与海拔、年日照时数和年降水量间相关关系显著;酚类降解产物与海拔高度存在着随海拔高度升高而增加的趋势;美拉德反应产物与温度条件的关系密切;西柏烷类物质在高海拔、中等水分和较高温度条件下更有利于其合成积累,光照强弱对其影响不大;新植二烯在时照时射、和煦的天气条件下容易降解和积累。     

Spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River during the period 2002–2011 based on the Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E) data

Detecting near-surface soil freeze-thaw cycles in high-altitude cold regions is important for understanding the Earth's surface system, but such studies are rare. In this study, we detected the spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River(SRYR) during the period 2002–2011 based on data from the Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E). Moreover, the trends of onset dates and durations of the soil freeze-thaw cycles under different stages were also analyzed. Results showed that the thresholds of daytime and nighttime brightness temperatures of the freeze-thaw algorithm for the SRYR were 257.59 and 261.28 K, respectively. At the spatial scale, the daily frozen surface(DFS) area and the daily surface freeze-thaw cycle surface(DFTS) area decreased by 0.08% and 0.25%, respectively, and the daily thawed surface(DTS) area increased by 0.36%. At the temporal scale, the dates of the onset of thawing and complete thawing advanced by 3.10(±1.4) and 2.46(±1.4) days, respectively; and the dates of the onset of freezing and complete freezing were delayed by 0.9(±1.4) and 1.6(±1.1) days, respectively. The duration of thawing increased by 0.72(±0.21) day/a and the duration of freezing decreased by 0.52(±0.26) day/a. In conclusion, increases in the annual minimum temperature and winter air temperature are the main factors for the advanced thawing and delayed freezing and for the increase in the duration of thawing and the decrease in the duration of freezing in the SRYR.     

基于模糊数学的公路路面裂痕检测技术

根据公路路面实际裂痕灰度值比背景灰度值低,而路面非背景和非裂痕像素灰度值比背景灰度值高或低很多,设计了一种基于模糊数学的公路路面裂痕检测的新技术.首先使用改进的基于乘性模型的灰度校正算法对原始图像进行预处理,接着根据OTSU最大类间方差法计算得到原图像前景与背景的最佳阈值作为渡越点,构造一个新的模糊隶属度函数对预处理后的图像进行模糊处理,然后用Sobel算子对模糊后的图像边缘检测判断得到含有裂痕信息的区域,最后用图像分割算法区域分割出含有裂痕信息的图像子块.实验证明,新提出的方法在处理速度和检测准确性方面基本能够满足实际需要,能实时、自动检测出模糊图像的裂痕.     

佛山市桥梁群阻水的数学模型分析

在不同频率流量和阻水条件下,采用一维明渠非恒定流网河数学模型,分析规划中的佛山市桥梁群对区间河道洪季行洪、枯季水环境的影响,计算洪季不同频率洪峰流量下规划桥梁群对区间河道行洪洪水位、分流比的影响,枯季时规划桥梁群对区间河道过流量、分流比的影响,进而提出规划桥梁群建设的合理化建议和限制条件,避免和有效应对规划桥梁群建设对河道的综合利用可能带来的不利影响。     

水稻植株生长模型的研究

研究了早稻茎数消长和叶龄增长,以及叶面积增长和抽穗率的变化,分析了叶龄与积温,氮肥水平及茎数之间的关系,以及不同类型品种间分蘖力的差异,分别组建了叶龄与积温,茎数的数学模型,不同施氮量与茎数消长的数学模型,以及叶面积增长和始穗率数学模型。结果表明,早稻常规品种的茎数消长主要与叶龄增长的关系密切,同时受品种的分蘖力潜能,总叶片数以及不同施氮量的影响,叶龄增长主要与积温有关,而与施氮量关系不明显。     

高校双语教学的实践与展望

本文通过在双语教学的实践和探索过程中积累的经验，就教学模式、教学手段和教材的处理等总结了有效的举措和经验，分析了教学中所遇到的问题并提出可行的解决办法，最后对将双语教学如何达到教学目标提出了展望。