南方森林对雨雪冰冻灾害的受损与恢复响应的树龄依赖

森林受损与恢复对雨雪冰冻灾害的响应机制是森林研究与管理中的重要问题.然而对于植被受灾中,大树、中树、小树何者容易受损,即树龄依赖性问题仍没有一致结论,而受损后恢复的树龄依赖性则鲜有研究报道.本研究通过调查2008年中国南方罕见的雨雪冰冻灾害后,南岭天井山不同林型内植被的受损与恢复的情况,探讨森林对雨雪冰冻灾害的受损与恢复响应的树龄依赖.结果表明,植被的受损与恢复都反映出不同程度的树龄依赖性.3种林型中植被受损的比例随着树龄的增大而增加,在达到一定径级大小后达到平稳,这种规律在不同林型中表现出差异性,针叶林中的小树相比阔叶林的小树更易受损;从受损方式上也反映出不同林型的树龄依赖有所不同.就受损最为严重的方式掘根来说,针叶林幼苗的掘根比例较大,混交林小树的掘根比例显著大于幼苗和大树,而阔叶林大树的掘根比例显著大于幼苗和小树.不同林型受损恢复的树龄依赖性存在差异,针叶林折干与折冠树木(径级大于2.5 cm)的恢复率随树龄增加呈现逐渐上升的趋势,而针阔混交林与阔叶林折干与折冠树木的恢复率随着树龄增加呈波动变化,不存在明显的上升或下降的变化趋势;根部受损严重的树木恢复率为零,全部掘根死亡.植被受损及恢复与树龄之间存在关联性,并且这种关联性受林型、树形和受损方式等因素的差异所影响.植被受损与恢复都存在树龄依赖性,并且这种依赖性受林型、树形和受损方式等因素的影响,认识这种依赖性是有效应对灾害和开展灾后恢复重建的重要基础.     

中国南方干旱灾害风险特征及其防控对策

应用中国南方区域14省区市252个国家基本气象站1961—2015年逐日地面气象观测资料及干旱灾害资料,研究中国南方干旱灾害影响的时空变化特征,分析中国南方干旱灾害风险变化特征,提出干旱灾害风险防控策略与防御对策。结果表明:近55年中国南方区域降水量呈现波动变化,降水量线性拟合趋势特征不明显。但进入21世纪后南方区域平均降水量明显偏少,且平均降水量年际振荡幅度增大。近55年研究区气温呈显著上升趋势,南方平均地表气温升高速率高于全球地表升温速率;研究区气温从1976年开始持续上升,气温升高的突变年在1997年。重旱风险高发区主要集中于西南,随着气候变暖,干旱灾害频率、强度和受旱面积均增加,干旱灾害风险增大。气温突变后次高干旱灾害风险区明显扩大。未来10年(2016—2025年)中国南方地区的干旱发生频率可能升高。因此,要加强干旱灾害风险管理,生态环境脆弱区域实施生态环境修复,农业主产区域以保障粮食安全为主,解决水资源时空分布不均和资源供需加剧矛盾,提高干旱灾害风险防控水平。     

南方森林雨雪冰冻灾害的特征

近年来极端气候事件频发,各地的雨雪冰冻灾害受到广泛关注。极端的雨雪冰冻灾害作为一个重要的扰动因子,对森林生态系统造成重大影响,尤其是在中国冰雪天气少有发生的南亚热带地区。2008年1-2月中国南方遭受了一场低温雨雪冰冻综合性极端天气灾害,其持续时间长,影响范围广,对中国南方森林造成了严重的损害。国内对此次雨雪冰冻灾情概况、林木受损情况以及雨雪冰冻灾害程度的影响因素等方面开展了大量研究,而现有的研究对受损林木评定的标准主观、粗略不全或是概念混淆,造成各研究结果难以比较。为明晰分类标准及相关概念,本文在总结雨雪冰冻灾害发生的气候与生物学特点、整合前人研究结果的基础上,提出雨雪冰冻灾害中林木生理冻害分类标准以及林木机械损伤分类标准,为相关研究提供参考依据。同时,总结分析雨雪冰冻灾害中导致森林受损的各影响因素,并将众多的因素总结归纳为影响凝雪冰凌重量及林木自身抵抗力2个方面。最后,针对灾害的影响因素以及灾后森林易发生的次生灾害,提出灾后森林恢复与重建的建议。     

利用MODIS数据评估冷冻灾害对广东植被的损害

2008年初我国南方地区发生的极端冷冻灾害对植被造成了极大破坏。以广东为例,利用MODIS数据,对比分析了受损植被与正常植被的NDVI变化;利用ISODATA非监督分类方法提取受损植被分布信息,借助90m SRTM DEM数据研究受损植被与地形因子的关系,发现广东植被受损严重,受损植被总面积达19 011.06 km²。受损植被受海拔高程、坡度、坡向等地形因子影响较大;受损植被主要集中于海拔大于400 m,坡度小于15°的阴坡区域;通过MODIS土地覆盖图与受损植被的复合分析,研究了该地区受损植被的类型,发现受损植被以常绿阔叶林、混交林、落叶阔叶林、灌丛、落叶针叶林及常绿针叶林为主。     

森林低温霜冻灾害干扰研究综述

在全球变暖的背景下,森林低温霜冻灾害的发生并没有减少趋势,低温霜冻灾害的发生可能对林木的组织或整个幼树、幼苗产生致命伤害,进而成为林木生长发育,天然或人工更新的一个主要限制因子。森林低温霜冻灾害的发生和危害程度取决于林木生长复杂多变的物理环境和树木的耐冻性,前者又受大尺度环流形势及局地尺度小气候特征的影响。借助于3S技术建立复杂地形下低温和光照的空间分布模型,并结合林木的耐冻性,构建低温霜冻危害评估的概率模型,将有助于提高霜冻灾害的监测和危害评估水平。森林低温霜冻的防御应考虑将物理与生物防霜方法相结合,前者通过建防护林和采取合适的采伐措施,来改善林内地表的辐射平衡;后者则通过生物技术手段来增强林木的耐冻性。需结合霜冻灾害的监测和危害评估模型,对各种不同防霜措施的防霜效果进行定量评估。     

南方双季稻低温灾害等级预测

基于南方双季稻种植区708个气象站1961—2010年的逐日气象资料、双季稻低温灾害发生的气象行业标准和1960—2010年逐月74项大气环流特征量资料,采用因子膨化、相关性分析、逐步回归等方法,建立了针对不同风险和时空变化趋势的分区双季稻低温灾害历年第一次灾害发生等级预测模型。结果表明:高风险区(Ⅰ区)早稻春季低温灾害、晚粳稻寒露风、晚籼稻寒露风的预测模型平均外延预测基本一致准确率分别为100%、83.3%和83.3%;低风险且呈增加趋势区(Ⅱ区)早稻春季低温灾害、晚粳稻寒露风、晚籼稻寒露风的预测模型平均外延预测基本一致准确率分别为100%、83.3%和83.3%;低风险且呈减少趋势区(Ⅲ区)早稻春季低温灾害、晚粳稻寒露风、晚籼稻寒露风的预测模型平均外延预测基本一致准确率分别为83.3%、100%和83.3%;各预测区域各代表站预测模型的回代和预测等级误差基本在1个等级以内,具有较高的精度。     

古田山24 ha森林动态监测样地常绿阔叶林群落结构和组成动态: 探讨2008年冰雪灾害的影响

常绿阔叶林是我国亚热带地区的地带性植被, 其中最为典型而且分布最广泛的是中亚热带常绿阔叶林。为探讨2008年初我国南方发生的冰雪灾害对中亚热带常绿阔叶林的影响, 以浙江省古田山国家级自然保护区24 ha森林动态监测样地内的中亚热带常绿阔叶林为例, 研究了该森林在冰雪灾害前后(2005-2010年)的群落结构及物种组成动态。结果表明, 群落径级结构变化较小, 但群落整体补员不足且死亡率较高; 多个粒度上的群落动态显示出一致的衰退特征, 但不同生境间的群落动态存在差异; 物种多度和胸高截面积多呈减小趋势, 但频度和重要值变化不明显。同时, 物种的多度、胸高截面积、频度和重要值等次序均无明显变化。这说明2008年发生的冰雪灾害对古田山中亚热带常绿阔叶林群落的短期动态产生了较大的负面影响, 且其影响程度与植物胸径和地形等因素密切相关; 同时也反映了古田山中亚热带常绿阔叶林群落结构对冰雪灾害干扰具有一定的抵抗力。     

微生物灾害新领域

人们利用微生物酿酒、生产柠檬酸、制造抗菌素和酶制剂等,这类微生物有效利用的例子举不胜举.然而,微生物也有其有害的一面.近二十年来,国外关于微生物灾害新的研究领域,巳发表了数千篇论文.各国纷纷建立专们的研究机构,开展研究工作.在我国,这方面的研究工作刚刚开始.现将微生物灾害的具体事例介绍如下.     

冰雪灾害对粤北杉木林土壤物理性质的影响

2008 年1 月至2 月, 雨雪冰冻天气袭击广东粤北地区。冻雨在枝叶上形成冰柱, 造成大量的折干残体。冰雪灾害对森林土壤的影响是森林恢复和管理的关键所在, 然而对灾害引起土壤物理性质的变化研究甚少。为了研究冰雪灾害对土壤物理性质的影响, 在粤北乐昌林场杉木林内建立三个面积为20 m×20 m 的固定标准地, 分别在标准地中心以及四个角采集上土层(0-20 cm)和下土层(20-40 cm)的土样, 测定土壤物理性质: 土壤容重、毛管持水量、总孔隙度、毛管孔隙度、非毛管孔隙度和通气孔隙度。研究结果表明: 与2008 年相比, 2011 年杉木林地土壤容重降低, 而土壤毛管持水量、总孔隙度、毛管孔隙度、非毛管孔隙度和通气孔隙度均升高, 说明冰雪灾害对土壤物理性质有重要影响。     

浙江九龙山自然保护区黄山松种群冰雪灾害干扰及其受灾影响因子分析

2008年1-2月间, 我国南方广大地区遭受了50年一遇的重大冰雪灾害, 对我国南方林区造成了巨大的损害。浙江九龙山国家级自然保护区黄山松(Pinus taiwanensis)人工林也在此次冰雪灾害中遭到重大损失。针对保护区内黄山松人工林种群的地理分布和受灾特点, 沿海拔梯度设置了6 000 m²的具有代表性的样地, 对其受灾情况进行调查, 分析了不同胸径(DBH)、树高、冠幅等林木特征下的黄山松抵御冰雪灾害能力的差异, 并对不同海拔的黄山松受灾情况进行了比较。结果表明: 1) 九龙山黄山松种群受灾严重, 除树干弯曲外, 其他不同受灾类型的植株在种群中均有出现, 且以断冠植株为最多。2) 黄山松对冰雪灾害的抵御能力与林木大小有关, 断大枝和断冠易发生在相对较粗和高的植株当中; 较为细小和低矮的植株则容易被断干和掘根; 冻死植株以幼树居多, 其DBH和树高显著小于其他受灾类型植株。3) 不同冠幅的黄山松植株受灾类型存在很大差异, 冠幅越大, 植株受灾越严重, 掘根和断干在冠幅较大的植株中较为常见。4) 尖削度、树冠相对高度和不均匀程度对黄山松抵御冰雪灾害也具有较大影响, 尖削度小、树冠较高且不均匀的植株受灾较重。5) 海拔较高处黄山松受灾严重, 断干和掘根植株主要分布在825-850 m的高海拔区间内。     

Antibiotics in the treatment of wounds in the victims of the earthquake in the Armenian SSR

Purulent wounds in 88 victims of the Armenian earthquake with the syndrome of long-term squeezing were examined microbiologically and the experience with using antimicrobial drugs for their treatment was analyzed. In all the cases microbial associations were detected, coliform and nonfermenting gram-negative bacilli, enterococci, anaerobes and yeast-like fungi being isolated from 80, 20, 15 and 25 per cent of the patients respectively. 130 bacterial strains were studied in detail. 80 to 100 per cent of the bacterial isolates were resistant to the antibiotics routinely used in surgical practice, i.e. benzylpenicillin, tetracycline, levomycetin, kanamycin, cephalothin and cefazolin and highly sensitive to new antimicrobial drugs belonging to ureidopenicillins (mezlocillin), quinolones (ciprofloxacin) and cephalosporins of the 3rd generation (cefoperazone and ceftazidime). Retrospective estimation of the antibiotic therapy revealed its inadequacy in 55.7 per cent of the patients for the most part because of the isolates resistance. The 19 variants of the antibiotic use prescribed by the physicians mainly included penicillins, aminoglycosides and their combinations (in 67.2 per cent of the cases). The use of the highly efficient drugs of the groups of ureidopenicillins and quinolones was extremely rare which was likely due to lacking of information on the drugs.     

Changes in the size of the nucleoli of the Purkinje cells in the canine cerebellum in the postresuscitation period

The changes in the size of Purkinje cell (PC) nucleolus in the lateral and medial cerebellum zones were studied in dogs with different degree of neurologic status recovery after clinical death of various etiology and duration. PC always possess one nucleolus in the control and experimental groups. In the case of complete neurologic status recovery of animals the area of PC nucleolus increases in both zones studied, irrespective of the cause of clinical death. In the case of neurologic disorders the increase in PC nucleolus area is clearly expressed only in the medial zone of the cerebellum, being insignificant in the lateral zone. It is suggested that adaptive characteristics of PC are distinct in the two compared zones, which leads to greater PC vulnerability in the lateral zone during deep hypoxia.     

On the role of the pineal in thermoregulation in the pigeon

Diurnal rhythm in body temperature of pigeons subjected to different experimental conditions (pinealectomized, sham-operated, melatonin-implanted, cold-exposed) was studied under a 12 h light and 12 h dark regimen. The body temperature of pigeons during photophase was higher than that during scotophase in the normal as well as every treatment group studied. Pinealectomized pigeons showed higher body temperature in the photophase as well as scotophase, than that of the normal and sham-operated birds when examined 2 or 3 weeks following the post-surgical acclimatization to 25 or 3 degrees C. However, subcutaneous implantation of melatonin pellets into pinealectomized pigeons nullified or even reversed the hyperthermic effect of pinealectomy. Exposure of pigeons to--18 degrees C for 280 min during photophase as well as scotophase, produced a marked drop in body temperature in pinealectomized, sham-operated and normal pigeons. The pinealectomized pigeons exhibited a higher body temperature than that of the sham-operated and normal ones when exposed to--18 degrees C during the photophase, but not during the scotophase. It was concluded that while the pineal is not necessary for maintaining the daily thermal rhythm in the avian body, it has a thermoregulatory role, in that it prevents rise in body temperature in warm (25 degrees C) acclimatized and chronic cold (3 degrees C) exposed birds. In acute short-term cold (--18 degrees C) exposure however, the temperature regulatory role of the pineal was not effective during the scotophase.     

Histogenesis of the taste buds of the vallate papilla in the in the rat in the postnatal stages of development

The developing taste buds of vallate papillae were studied with electron microscope in rats during the first 7 days after birth. Two types of cells--light and dark--are identified in the taste buds of a one day old animal. The apical parts of dark cells are characterized by numerous dark granules. A distinguishing feature of light cells is the presence of synaptic contacts with afferent intragemmal nerves. On the 4th day of development on the top of the apical parts of the cell, a microvillar apparatus is seen to form, which does not yet communicate with the oral cavity. On the 7th day, basal cells appear in the taste buds. Some of these cells are seen mitotically dividing. The differentiated microvillar apparatus now communicates with oral cavity. The structure of the taste buds is getting similar to that in the adults. The structural and functional peculiarities of the developing taste buds are discussed in association with the period of ontogenesis under consideration.