农业科研单位固定资产管理问题探究

从农业科研单位固定资产管理中存在的主要问题出发,对存在的问题进行了阐述和分析,提出了加强固定资产管理工作的措施和建议。     

科尔沁沙地典型沙丘植被光谱特性

采用Field Spec4(美国ASD)的便携式光谱仪对科尔沁5种典型沙丘植被的光谱曲线进行测量,并对其特征进行提取分析。结果表明,1)5种典型沙丘植被黄柳(Salix gordejevii)、冷蒿(Artemisia frigida)、麻黄(Herbal ephedrae)、差巴嘎蒿(Artemisia halodendron)和小叶锦鸡儿(Caragana microphylla)的光谱形态大致相同。根据原始光谱差异和多个光谱特征参数可以区分植被类型。"红边斜率"由高到低依次为冷蒿(0.99%)小叶锦鸡儿(0.68%)黄柳(0.59%)麻黄(0.58%)差巴嘎蒿(0.56%)。2)对差巴嘎蒿不同季节光谱反射率特性进行比较分析得知,随植被生长期推移,差巴嘎蒿呈现出"双峰"和"红移"现象,但该现象并不明显。由于研究区在7月份出现持续干旱,植被缺水严重,导致差巴嘎蒿的"红边位置"在7月6日出现微小浮动,显现两个"红边平台"。3)分析不同覆盖度下差巴嘎蒿的光谱特性,差巴嘎蒿的导数光谱呈现"双峰"特性,且当覆盖度大于40%时,"红边位置"与覆盖度并无直接联系,但"红边斜率"与覆盖度呈正比关系。对不同覆盖度下差巴嘎蒿光谱可见光波段的连续统去除,得到吸收深度随覆盖度的增加而增大,吸收峰面积随覆盖度的增加而减小,对覆盖度敏感性参数比较可知,研究该地区差巴嘎蒿覆盖度变化优先考虑吸收峰面积。因此,基于植被高光谱特性的分析,对于今后利用遥感监测沙丘植被长势、植被分类识别及反演植被覆盖度等的应用提供重要的参考价值。     

利用Laplace变换求解一维波动方程的定解问题

运用Laplace变换的概念和一些主要性质研究了波动方程的定解问题,首先运用Laplace变换将波动方程转化为代数方程,再利用周期函数的Laplace逆变换公式求出方程的解,并举例验证了Laplace变换法的简便性.     

求解各向异性扩散LLT模型的新的图像去噪算法

基于四阶各向异性扩散的图像去噪LLT模型,提出了一种修正不动点迭代算法. 该算法以最速下降方向为搜索方向,以避免直接计算逆矩阵,减小了舍入误差,提高了算法的收敛速度.利用矩阵的谱性质证明了该算法的收敛性. 数值实验结果表明：对于256×256的“Lena”图像,在标准差为15的高斯白噪声情况下,本文提出的算法将信噪比由SNR=11.208 8提高到SNR=16.511 1.     

毛乌素沙地不同沙丘部位几种灌木地土壤水分动态

土壤水分是制约沙漠植物生长的主要因素之一,地形部位对土壤水分影响较大,以毛乌素沙地固定沙丘3种灌木地为研究对象,分析其不同沙丘部位下各层次土壤水分的变化,并采用Brown-Forsythe检验方法分析不同沙丘部位之间土壤水分含量的差异。结果表明,沙地柏土壤体积含水量为0.97%～17.66%,油蒿土壤体积含水量为1.51%～15.70%,杨柴土壤体积含水量为3.20%～19.05%。表土层土壤水分含量较高,心土层土壤水分含量最低。表土层中丘顶、迎风坡中部、迎风坡下部与背风坡中部差异显著(P值分别为0.04,0.045,0.03),说明地形部位对表土层壤水分含量影响较大,背风坡水分含量高于迎风坡,因此栽植植物时可选择在背风坡栽植,以便于植物成活。     

植物石蜡切片的固定与保存

石蜡切片是观察植物组织构造常用的制片方法之一。活的细胞或组织多为无色透明,各种组织间和细胞内各种结构之间均缺乏反差,在一般光镜下不易清楚区别;组织离开机体后很快就会死亡和产生组织腐败,失去原有正常结构,因此,组织要经固定、石蜡包埋、切片及染色等步骤以免细胞组织死亡,才能清晰辨认其形态结构。重点研究了植物石蜡切片的固定与保存,拟为今后固定剂及固定方法的选择提供科学依据。     

财政投入和金融支持对农民农业增收贡献的比较

基于2000~2013年省级面板数据,运用固定效应模型和分位数回归模型考察了财政投入和金融支持对提升农民农业收入的影响,并采用因素分解法比较两者对农民农业增收的贡献大小,继而通过两步固定效应回归、分组回归和替换变量回归三种方式检验结果的稳健性,均得出一致结果,即财政投入和金融支持均促进农业增收,其中财政投入贡献更大,此外大规模的土地投入和完善的基础设施建设也有利于农业收入提高。     

Effect of vegetation restoration on ant nest‐building activities following mobile dune stabilization in the Horqin Sandy land,Northern China

Measurements of the density and characteristics (size and height) of ant mounds were carried out on mobile, semi‐mobile, semi‐fixed and fixed dunes in the Horqin Sandy Land, Northern China. The relationships between the distribution of ant mounds and the plant community (abundance and cover) were investigated, for areas within and across the dune stages. Changes in spatial pattern of ant mounds were also analysed following mobile dune stabilization. The results showed no ant mounds on mobile dunes; the mound density was significantly higher on fixed dunes than on semi‐fixed or semi‐mobile dunes. The mound density depended on plant density and cover across all dune stages, but not within any dune stage. The mound diameter increased but the mound height decreased from semi‐mobile dunes to fixed dunes. However, the mound diameter and height were not related to plant cover and density within any stabilization stage or across all dune stages. The spatial pattern of ant mounds tended to change from more clumped (semi‐mobile and semi‐fixed dunes) to less clumped and approached a random pattern (fixed dunes) along the dune stabilization gradient, which was related to the changing vegetation pattern during succession. Although the quantification of the number of ant species present was not attempted on each dune, the observed differences in ant colour and size suggest at least eight species were present. Fixed dunes were more attractive for different kinds of ant species, but the mound distribution exhibited a more random pattern with more continuous vegetation. Thus, different environmental conditions, especially in terms of the plant communities present at different dune stages, affected the activities and behaviour of the ants (including the distribution of mounds), but did not affect mound size and height. Copyright © 2009 John Wiley & Sons, Ltd.     

海南铜鼓岭国家自然保护区药用植物调查研究

结合传统的路线法、小样方法与固定样地法调查铜鼓岭保护区药用植物在群落中的分布情况。结果表明,铜鼓岭国家自然保护区共有药用植物640种,隶属136科544属。其中,蕨类植物20种,隶属14科17属;裸子植物1种;被子植物618种,隶 属120科525属。640种药用植物中包括4种海南特有种植物,8种濒危珍惜、国家级保护植物。经过调查分析发现,铜鼓岭保护区药用植物资源在植物群落中占有重要地位,如贡甲、海南大风子、赤楠蒲桃等在铜鼓岭保护区的分布广泛且数量众多,其中海南大风子是国家级珍稀保护植物,但在铜鼓岭保护区内却是优势物种,这是铜鼓岭保护区药用植物资源的重要特色。     

Increase in the Capacity of Interlayer Sites in a Paddy Soil as a Possible Factor Affecting the Dynamics of Fixed Ammonium at the Initial Stage of Anaerobic Incubation

To evaluate whether the capacity of interlayer sites affects the dynamics of fixed ammonium (NH₄⁺) in a paddy soil, a combination of potassium (K)–saturation treatment and stepwise extraction of nonexchangeable K with 0.01 mol L^?1 hydrochloric acid was applied to a soil incubated anaerobically up to 70 days. The capacity of interlayer sites increased with an increase of weakly fixed NH₄⁺ during the initial 28 days (r = 0.78, P < 0.01), and remained stable thereafter. On the other hand, the concentration of exchangeable NH₄⁺ increased curvilinearly during the whole incubation period, which was correlated with an increase of weakly fixed NH₄⁺ (r = 0.85, P < 0.01). These results suggested that the dynamics of weakly fixed NH₄⁺ in a paddy soil is regulated not only by the chemical equilibrium between exchangeable and weakly fixed NH₄⁺ but also by the capacity of interlayer sites within a few weeks after flooding.