湿地松林分间伐对材种结构的影响研究

根据间伐8年后的湿地松林分生长和主伐造材调查结果，建立了胸径和断面积等与林分保留密度及本底断面积的回归关系，分析比较了不同间伐强度对林木径阶分布和造材材种结构的影响效果。研究结果表明，间伐后林分保留密度对林木胸径和断面积生长以及材种结构等均产生显著影响；尾径20cm及以上规格的材种出材率随间伐强度增大而增大，而14cm及以下规格的材种出材率则随间伐强度的增大而减小。不同伐对照总的出材量虽比间伐的大，但增加的部分主要为较小规格的材种。     

甘蓝型油菜种子胎萌发生的影响因子研究

以黄籽油菜'410'456'552'和黑籽油菜'492'为试验材料,采用花期标记、定期采样、形态和生理分析等方法,研究了种子胎萌发生时期、环境对胎萌的影响以及胎萌与种子的形态和相关生理指标的关系.结果表明:4个甘蓝型油菜品种种子胎萌发生在种胚充实阶段(花后27～36 d左右),初始胎萌率为2.44％～3.90％,胎萌发...     

水温升高对黑斑侧褶蛙蝌蚪变态时长和血液参数的影响

为探究升温对黑斑侧褶蛙（Pelophylax nigromaculatus）变态时长、形态表型和血液参数的影响,在水温为21、23、25和27℃条件下,测定了从37期蝌蚪发育至46期变态完成期时的变态时长、身体大小、血液中各型白细胞的百分比及嗜中性粒细胞与淋巴细胞的比值（N/L的比值）的变化。结果显示,21 ℃组和23 ℃组的变态时长显著长于25 ℃组和27 ℃组（P < 0.05）;体重、体长以及体重与体长的比值都在21 ℃组最高,25 ℃组最低,但均无明显的组间差异（P > 0.05）。水温对血液淋巴细胞、嗜中性粒细胞、嗜酸性粒细胞、嗜碱性粒细胞和单核细胞的百分比以及N/L的比值均无明显影响（P > 0.05）。升温可加速黑斑侧褶蛙蝌蚪的变态过程,但不影响各型白细胞所代表的天然免疫能力和应激反应能力。     

Soil texture affects the conversion factor of electrical conductivity from 1:5 soil-water to saturated paste extracts

Electrical conductivity (EC) of soil-water extracts is commonly used to assess soil salinity. However, its conversion to the EC of saturated soil paste extracts (EC_e), the standard measure of soil salinity, is currently required for practical applications. Although many regression models can be used to obtain EC_e from the EC of soil-water extracts, the application of a site-specific model to different sites is not straightforward due to confounding soil factors such as soil texture. This study was conducted to develop a universal regression model to estimate a conversion factor (CF) for predicting EC_e from EC of soil-water extracts at a 1:5 ratio (EC_1:5), by employing a site-specific soil texture (i.e., sand content). A regression model, CF=8.910 5e^{0.010 6sand}/1.298 4 (r²=0.97, P < 0.001), was developed based on the results of coastal saline soil surveys (n=173) and laboratory experiments using artificial saline soils with different textures (n=6, sand content=10%-65%) and salinity levels (n=7, salinity=1-24 dS m^-1). Model performance was validated using an independent dataset and demonstrated that EC_e prediction using the developed model is more suitable for highly saline soils than for low saline soils. The feasibility of the regression model should be tested at other sites. Other soil factors affecting EC conversion factor also need to be explored to revise and improve the model through further studies.     

孕穗期不同低温对水稻空壳率的影响

为了降低低温对水稻生产造成的损失,以水稻品种龙稻5号和东农428为材料,采用盆栽种植方式于孕穗期进行低温处理,研究孕穗期低温对水稻空壳率的影响。结果表明:随着低温强度降低及时间延长,水稻空壳率显著增加。水稻品种龙稻5号较东农428更具耐冷性。     

Variations in carbon and nitrogen ratios and their effects on seed germination in Cupressus sempervirens populations

This study investigated the variations in the carbon (C), nitrogen (N), and C/N ratios in the seeds of the Mediterranean Cypress (Cupressus sempervirens L.), a typical forest tree of the Mediterranean Region. The data were gathered from populations distributed across Turkey. We also evaluated the relationship between these variations and germination parameters such as the germination percentage (GP) and mean germination time (MGT). All of the evaluated characteristics demonstrated statistically significant variations among the populations. The GPs were generally low and varied between 14% in Datça and 51% in the Köprülü Kanyon. The MGTs ranged from 14.9 in the Köprülü Kanyon to 18.9 in Marmaris. In addition, the C ratios varied between 46% in Marmaris and 52% in the Köprülü Kanyon, while the N ratios ranged from 1.1% in Beycik and Göksu to 1.8% in the Köprülü Kanyon. Furthermore, we observed a positive correlation between the GP and the C and N contents (R² = 0.51 and R² = 0.49, respectively) but found a negative correlation between the MGT and the C and N contents (R² = 0.56 and R² = 0.32, respectively). Moreover, with regard to the combined C and N seed ratios of the regression models, R² = 0.95 for the GP and R² = 0.87 for the MGT, and the populations with higher quantities of C and N in their seeds had shorter MGTs and higher GPs.     

蒙古扁桃种子萌发和幼苗生长对渗透胁迫的响应

以天然生长于祁连山自然保护区隆畅河自然保护站的濒危植物蒙古扁桃(Prunus mongolica)去内果皮的种子为材料,以不同渗透势PEG-6000溶液模拟干旱条件,研究了种子萌发和幼苗生长对干旱胁迫的响应特征。结果表明,随着干旱胁迫程度的加剧,蒙古扁桃种子吸胀速率、萌发率、萌发指数、活力指数、苗高和根长、组织饱和含水量等指标均表现出明显降低的趋势,而幼苗初生芽干重、根干重和根冠比均呈先升后降的趋势。蒙古扁桃种子对水势变化既敏感又抗旱,种子能够萌发的最低渗透势阈值为-0.65 MPa。干旱胁迫未能萌发的种子复水后萌发率较高。分析认为,蒙古扁桃种子萌发和幼苗生长对干旱胁迫的响应特征对种的延续具有重要意义,但在人工栽培时保证 土壤墒情应是保障建植成功的关键措施。     

农田土壤颗粒尺寸分布分维及颗粒体积分数的空间变异性

盐渍土膜下滴灌过程中的土壤理化性质存在空间变异性,对灌溉管理有一定影响。该文根据3个不同尺度下土壤采样及颗粒尺寸分布（PSD）测定结果,探讨了土壤PSD分维和颗粒体积分数之间的定量关系,分析了各尺度和综合尺度下土壤PSD分维和颗粒体积分数的经典统计特征和地质统计特征,根据颗粒体积分数的半方差函数计算了不同尺度颗粒体积分数的分形维,并做出了等值线图。研究表明,土壤PSD分维与黏粒的体积分数呈正相关关系,黏粒体积分数增大引起PSD分维增加的原因在于细颗粒的比表面积比粗颗粒的大;各尺度土壤PSD分维及颗粒体积分数均无强变异特征;不同尺度下土壤PSD分形维的半方差函数中块金和基台值均非常低;50 m尺度土壤PSD分维和黏粒体积分数的等值线图具有类似的集中度和走势,而砂粒体积分数和粉粒体积分数则具有相反的集中度和走势。该研究说明土壤PSD分维和颗粒体积分数都有一定的尺度依赖性。     

径向基神经网络在猪胴体瘦肉率预测中的应用

猪胴体瘦肉率(LMP)是评价猪肉品质的重要指标之一,在生产线上快速而准确地预测出其数值并进行分级是并不可少的。目前,国内大部分厂家依然采取屠宰后人工称重测量的方法,耗时耗力,且存在相当大的误差。为此,随机抽取了116头皖北地区商品猪,选定眼肌面积、背膘厚及腿臀比作为参考数据,以Mat Lab工具箱作为研究工具,利用BP、Elman和RBF等3种不同的神经网络建立预测模型,统计后进行比较分析。实验表明:3种模型的神经网络均可用于瘦肉率预测,但RBF网络误差最小,训练速度最快,学习能力最强,最适合用于建立瘦肉率的预测模型。     

西宁奶牛场荷斯坦奶牛乳脂率测定

对西宁奶牛场３２７头中国荷斯坦泌乳奶牛的乳汁进行乳脂率测定。结果：乳脂率平均值为３．４９％，变动范围１．２％～６．８％；乳脂率在２．７％以下的牛３１头，占全群牛的９．５％，２．８％～３．２％的牛６７头，占２０．５％，３．３％～３．９％的牛１６３头，占４９．８％，４％以上的牛６６头，占２０．２％；不同胎次、产奶量及不同泌乳期乳脂率有一定的变化。