表观健康猪群携带猪链球菌2型毒力因子的分布特征

为了研究钦州市猪链球菌2型(SS2)的毒力因子分布特征,采用多重PCR方法对从我市健康猪扁桃体分离的11株SS2相关毒力基因——荚膜多糖(Cps2J),溶菌酶释放蛋白(Mrp),胞外蛋白因子(EF),溶血素(Sly),进行毒力基因检测。检测结果显示:毒力基因型为Mrp+epf+Sly+共有8株,毒力基因型为Mrp+epf+Sly-共有1株,这两种毒力基因型可归为强毒力基因型,占此次健康猪源毒株的81.8%;另外Mrp-epf-Sly-共有2株,属于弱毒和无毒基因型,占健康猪源毒株的18.2%。通过结果分析,预示我市目前SS2的主要流行菌株是同时具有4种毒力因子的高致病性菌株。     

Below‐Canopy distribution of photosynthetically active radiation and its relation to seedling growth in a boreal Pinus sylvestris stand

A simulation model was used to predict the spatial distribution of direct and diffuse photosynthetically active radiation below a heterogenous canopy of a Pinus sylvestris stand in eastern Finland. Seedling growth was related to both measured and predicted radiation. The model predicted rather well the overall pattern of radiation distribution beneath the canopy. All the growth parameters of Pinus sylvestris seedlings (height, current height increment and mean height increment) correlated positively with the amount of both measured and predicted radiation. The correlation between seedling growth and irradiance was better for predicted diffuse radiation than for total radiation. This was probably because diffuse radiation, being symmetrically distributed around trees, correlates more strongly than direct radiation with other factors affecting seedling growth.     

民间花文化是持续推动广东花卉产业发展的新动力

将调查数据以性别、年龄等自然特征进行匹配分析,发现广东农村民间潜藏着丰富的非物质层面的花文化,女性对花文化的传承具有明显优势,花卉在广东农村社会交往中已经融入民间的精神世界而成为表情达意的沟通媒介。发挥女性对花文化的传承优势,凭借比邻港澳地缘空间,结合民间非物质层面的花文化宣传中国的传统节日、传统花卉,吸纳世界的优秀礼仪文化,将有利于促进广东花卉产业的发展。民间花文化理应为广东花卉产业的新发展增添持续的不可替代的文化动力。     

几株乳酸杆菌耐逆性的比较研究

试验主要比较研究了6株乳酸杆菌对热(55℃和65℃)、酸(pH值1.0、2.0和3.0)、胆盐(0.1%和0.3%)、微量元素铜(0、10、50和250mg/L)和锌(0、120、600和3 000mg/L)的耐受性。结果表明:各菌株对这些因子的耐受性有不同程度的差异,如菌株LGG增殖速度、产酸性、耐酸性和耐温度55℃的能力都较其他菌株好,但该菌株在65℃下存活率极低;菌株ZJ614耐高温能力较强,在65℃处理20min后存活率能达到19.2%,但Cu2+(50 mg/L)对其增殖的不良影响较大;菌株ZJ621虽对酸的耐受性较强,但对胆盐的耐受性较差。经全面考察各菌株对各逆性因子的耐受性,初步推断,菌株ZJ610和ZJ617的综合耐逆性相对较强。     

商品肉鸡舍内环境因子含量测定及分布规律研究

 对商品肉鸡舍内主要环境因子如氧气、二氧化碳、氨气、硫化氢浓度、细菌浓度以及温度、湿度等进行定量检测,并分析各环境因子变化规律。试验结果显示,该鸡舍内氧气浓度平均为19.6%,比舍外降低6.0%;二氧化碳浓度平均为3 673×10⁶ mg/m³,为舍外二氧化碳浓度的8.48倍;细菌浓度平均为6.9×10⁵ cfu/m³;舍内平均温度为24.0 ℃,相对湿度为75.5%;氨气浓度在试验期间均超过100 mg/m³;硫化氢浓度低于检测仪器最低浓度1 mg/m³。试验表明,鸡舍内空气环境中二氧化碳浓度与氨气浓度严重超标,氧气含量不足,各环境因子与病原微生物相互作用,可能是导致鸡群发病的主要原因。     

Modeling susceptibility to deforestation of remaining ecosystems in North Central Mexico with logistic regression

Determining underlying factors that foster deforestation and delineating forest areas by levels of susceptibility are of the main challenges when defining policies for forest management and planning at regional scale. The susceptibility to deforestation of remaining forest ecosystems (shrubland, temperate forest and rainforest) was conducted in the state of San Luis Potosi, located in north central Mexico. Spatial analysis techniques were used to detect the deforested areas in the study area during 1993-2007. Logistic regression was used to relate explanatory variables (such as social, investment, forest production, biophysical and proximity factors) with susceptibility to deforestation to construct predictive models with two focuses: general and by biogeographical zone.In all models, deforestation has positive correlation with distance to rainfed agriculture, and negative correlation with slope, distance to roads and distance to towns. Other variables were significant in some cases, but in others they had dual relationships, which varied in each biogeographical zone. The results show that the remaining rainforest of Huastecaregion is highly susceptible to deforestation. Both approaches show that more than 70% of the current rainforest area has high and very high levels of susceptibility to deforestation. The values represent a serious concern with global warming whether tree carbon is released to atmosphere. However, after some considerations, encouraging forest environmental services appears to be the best alternative to achieve sustainable forest management.     

影响黑龙江省夏季林火的关键气象因子分析

利用2001～2009年黑龙江省夏季林火资料和同期林区气象观测资料,采用主成分分析方法确定了月降水量和月无雨日数、月平均温度及14时月平均风速是影响夏季林火的关键因子,其中降水量是最重要的影响因子,其次是温度因子和动力因子,夏季的温湿状况以及动力条件是决定夏季林火是否发生的关键;根据温湿因子综合分析发现,夏季林火多发生在暖干型气候背景下,即气温高降水少的月份,而且这种形势下发生的火灾往往持续时间长、过火面积大、造成的损失严重。     

基于点云数据的测树因子提取与分析研究

利用三维激光扫描仪对树木进行扫描获取树点云数据,经过格式转换、分离、提取后,对树木各测量因子包括胸径、树高、树冠、材积量进行测定,并对测量方法进行分析与讨论。结果表明:树冠测定因子可以由于测量技术的提高,测定树冠的叶面积指数更能反映树冠的生理学意义;通过不规整三角网构建的多面体的计算的树干体积较平均断面积、中央断面积求树干材积更准确与便捷。     

不同生态因子对银杏生长的影响

用定位研究的方法,在丹东不同区域建立生态因子观测场,测定不同土层厚度、pH值、土壤养分含量、空气温湿度、光照强度、降雨、蒸发量等各因子对银杏生长的影响,结果表明:在不同的温度条件下,银杏种子萌发和幼苗生长状况不同,经20 d后,种子发芽率恒温比变温高6.2个百分点,幼苗根系生长、苗高、地径恒温比变温分别提高36.7%和16%。经过遮阴处理,银杏幼苗生长好于对照区。生长在壤土和沙壤土上的银杏其生长表现优于生长在沙土和黏土上的,土壤含盐量以0.03%～0.043%,银杏生长良好。银杏对pH值适应范围很宽,在pH值4～8.5的土壤上均能生长。     

呼伦贝尔沙地樟子松天然更新苗影响因素的研究

通过对呼伦贝尔沙地樟子松天然林天然更新苗特征及其影响因素的研究,结果表明:母树密度不同,天然更新苗数量和年龄结构存在明显差异;樟子松天然更新苗年龄结构在时间上具有明显的不连续性,樟子松天然更新苗密度因林分类型的差异明显不同。在疏林地(树龄30 a),平均更新苗密度每2 500 m2为13株,在火烧迹地平均更新苗密度每600 m2为28.5株,樟子松单株样地平均更新苗密度每600 m2为118.8株。不同年龄的天然更新苗保存密度和年平均降水量有显著或极显著关系,且随着林分郁闭度的增加,研究区天然更新苗密度呈现降低的趋势。