北京山区主要针叶林可燃物空间连续性研究——可燃物水平连续性与树冠火蔓延

以北京市山区主要针叶林(侧柏林和油松林)为研究对象,通过对林分树冠可燃物的负荷量、结构、理化性质及火行为特征进行分析,建立了树冠可燃物水平连续性指数D和评估等级,并对侧柏林和油松林的可燃物水平连续性进行评估与分析。研究结果显示:可燃物负荷量对火蔓延速度的影响显著,随可燃物负荷量增大,火蔓延速度增加,增加幅度受到可燃物紧密度的影响;风速对火蔓延速度的影响十分明显,对可燃物水平连续性的影响程度大于坡度;相同风速下,油松林树冠火的蔓延速度大于侧柏林;侧柏林D的平均值为1.470(高度连续),油松林D的平均值为0.933(中度连续),侧柏林树冠火蔓延的危险性大于油松林,一旦发生火灾,侧柏林比油松林更容易形成大面积高强度树冠火;D的主要影响因素是针叶树种树冠负荷量及其空间分布,以及风速和坡度及其协同作用。     

Functioning unilateral adrenocortical carcinoma in a dog

An 11-year-old, 24-kg, intact female Siberian husky dog in anestrus had a 2-month history of polyuria and polydipsia. The dog had signs of mineralocorticoid excess such as hypertension and hypokalemia refractory to potassium supplementation. Abdominal ultrasound revealed an irregular mass in the left adrenal gland. The ACTH stimulation test for aldosterone concentration did not reveal hyperaldosteronism. Unilateral adrenalectomy was performed and histopathology identified adrenal cortical carcinoma. All clinical signs of mineralocorticoid excess ceased after surgery.     

意大利园艺种子产业

经过几十年的长足发展,意大利已经跻身于全球种子生产的领头国家行列,该国种子产业最大的优势在于拥有众多专业化分工、市场营销策略明确的种子公司.本文精选了10家盈利最高的意大利本土种子公司,对其进行调查研究,以期对该国种子产业的特点和发展趋势有所了解.     

Communicative Action to Level the Playing Field in Forest Plantations in Indonesia

The government of Indonesia allocated state land to private companies to establish forest plantations. However, ownership of this land was contested by some Sumatran communities. The plantation company, endorsed by the government, quickly developed a partnership to resolve the conflict, but this was unclear and inequitable. Action research was carried out to facilitate communication among stakeholders. This communicative action changed some perceptions and shared values began to emerge. A forum was established, which contributed to equitability producing a better partnership. This research is a model for empowering local communities in climate change, bioenergy, and food security negotiations.     

重庆市北碚区土地利用转型及生态环境效应

以重庆市北碚区为例,利用2009年、2013年、2017年3期土地利用现状数据,基于土地利用主导功能视角,建立了“生态—生活—生产”（三生）分类体系,运用ArcGIS和社会网络分析软件Ucinet,通过土地利用转移矩阵、土地利用重心模型及土地利用转型生态环境响应模型,对该区土地利用转型及其生态环境质量进行了研究。结果表明:（1）2009—2017年,北碚区土地利用功能结构转型明显,生产用地面积减少,而生态、生活用地面积增加。（2）2009—2017年,除服务以及其他生产用地、工矿生产用地的重心向南偏移外,其余各功能用地重心均向北偏移。农业生产用地分布较为均衡,生活用地空间分布的不均衡性有所缓和,而生态用地分布的不均衡性进一步加剧,工矿生产用地、服务以及其他生产用地分布的不均衡性先加剧后有所缓和。（3）2009—2017年,北碚区土地利用生态环境质量维持稳定,生态恶化趋势略大于生态改善趋势,农业生产用地被占用是该区生态环境质量恶化的主要原因。     

Relationship between greenhouse gas emissions and changes in soil gas diffusivity in a field experiment with biochar and lime

Reducing greenhouse gas emissions from arable soil while maintaining productivity is a major challenge for agriculture. Biochar is known to reduce N₂O emissions from soil, but the underlying mechanisms are unclear. This study examined the impact of green waste biochar (20 Mg ha^?1) and lime (CaCO₃; 2 Mg ha^?1) application on soil gas transport properties and related changes in these to soil N₂O and CO₂ emissions measured using automated chambers in a field experiment cropped with maize. In situ soil water content monitoring was combined with laboratory measurements of relative soil gas diffusion coefficient (D_p/D₀) at different matric potentials, to determine changes in D_p/D₀ over time. Cumulative N₂O emissions were similar in the control and lime treatment, but much lower in the biochar treatment. Cumulative CO₂ emissions decreased in the order: lime treatment > biochar treatment > control soil. When N₂O emissions were not driven by excess N supply shortly after fertilisation, they were associated with D_p/D₀ changes, whereby decreases in D_p/D₀ corresponded to N₂O emissions peaks. No distinct pattern was observed between CO₂ emissions and D_p/D₀. Cumulative N₂O emissions were positively related to number of days with D_p/D₀ < 0.02, a critical limit for soil aeration. These results indicate that improved soil gas diffusivity, and hence improved soil aeration, may explain the effect of biochar in reducing N₂O emissions. They also suggest that knowledge of D_p/D₀ changes may be key to explaining N₂O emissions.     

Defining the immune response to Ehrlichia species using murine models

Pathogenic bacteria belonging to the family Anaplasmataceae include species of the genera Ehrlichia and Anaplasma. Ehrlichia chaffeensis, first known as the causative agent of human monocytic ehrlichiosis, also infects several vertebrate hosts including white-tailed deer, dogs, coyotes and goats. E. chaffeensis is transmitted from the bite of an infected hard tick, such as Amblyomma americanum. E. chaffeensis and other tick-transmitted pathogens have adapted to both the tick and vertebrate host cell environments. Although E. chaffeensis persists in both vertebrate and tick hosts for long periods of time, little is known about that process. Immunological studies will be valuable in assessing how the pathogen persists in nature in both vertebrate and invertebrate hosts. Understanding the host immune response to the pathogen originating from dual host backgrounds is also important to develop effective methods of diagnosis, control and treatment. In this paper, we provide our perspective of the current understanding of the immune response against E. chaffeensis in relation to other related Anaplasmataceae pathogens.     

Isolation of a novel viral agent associated with porcine reproductive and neurological syndrome and reproduction of the disease

Disease outbreaks characterized by reproductive failure and/or neurologic disorders, which are commonly referred as "Porcine Reproductive and Neurologic Syndrome (PRNS)", were observed in many swine farms in Iowa and other states. Although an infectious cause was suspected to account for the disease, no conclusive diagnosis had been reached with respect to conventional infectious agents. Extensive laboratory diagnostic investigation on suspect cases repeatedly resulted in the isolation of a cytopathic enveloped virus of 50-60nm in size from nervous and second lymphoid tissues and sera and, to reflect its unknown identity, named "Virus X". The presence of virus particle with morphological characteristics similar to Virus X in tissues from affected animals was also observed on thin-section positive-staining electron microscopy. Isolates of Virus X were not readily recognized by antibodies raised against any known viruses pathogenic to swine but by antisera collected from animals surviving clinical episode, indicating that Virus X is likely a previously unrecognized agent. Pregnant sows experimentally inoculated with Virus X (ISUYP604671) or homogenate (filtrate) of tissues from a clinically affected animal developed clinical signs and pathological changes similar to field observations including the loss of pregnancy. Furthermore, caesarian-derived, colostrum-deprived young pigs developed mild encephalomyelitis lesions in brains after experimental inoculation with the virus or the tissue homogenate although clinical neurologic signs were not observed. More importantly, Virus X was re-isolated from all inoculated animals while control pigs remained negative for the virus during the study. Collectively, Virus X is a novel viral agent responsible for PRNS and remains to be further characterized for taxonomical identity.