Natural and human disturbances affect natural regeneration of Swietenia macrophylla: Implications for rainforest management

In this paper we document how changes in forest structure mediated by natural (hurricane) and human (logging) disturbances affect natural regeneration of Swietenia macrophylla via its effects on seed predation, germination, and early recruitment. Work was carried out in two ejidos within the Mayan zone of Quintana Roo, differing with regard to their exposure to the effect of the hurricane Dean 2008 (Naranjal Poniente; high hurricane impact) and Señor (with no evidence of hurricane effects). We experimentally set S. macrophylla seeds in both hurricane conditions and contrasting logging effects, in three treatments: (1) open access, (2) rodent and insect access and (3) rodent and insect exclusion. We measured three dependent variables: (i) number of seeds predated, (ii) number of seeds germinated and (iii) number of seedlings established. We found that the three variables measured were differentially affected by logging and hurricane Dean. Seed predation was higher in areas with hurricane effects; germination showed no differences, but early recruitment was differentially affected by the two conditions, via an increasing of herbivory and sun exposition. Both types of disturbances studied occurred periodically in Yucatan Peninsula and elsewhere in tropics, so it is necessary to implement specific actions in order to face changes in mahogany natural regeneration stocks, and supporting the future management of tropical forests.     

The contribution of competition to tree mortality in old-growth coniferous forests

Competition is a well-documented contributor to tree mortality in temperate forests, with numerous studies documenting a relationship between tree death and the competitive environment. Models frequently rely on competition as the only non-random mechanism affecting tree mortality. However, for mature forests, competition may cease to be the primary driver of mortality.We use a large, long-term dataset to study the importance of competition in determining tree mortality in old-growth forests on the western slope of the Sierra Nevada of California, U.S.A. We make use of the comparative spatial configuration of dead and live trees, changes in tree spatial pattern through time, and field assessments of contributors to an individual tree's death to quantify competitive effects.Competition was apparently a significant contributor to tree mortality in these forests. Trees that died tended to be in more competitive environments than trees that survived, and suppression frequently appeared as a factor contributing to mortality. On the other hand, based on spatial pattern analyses, only three of 14 plots demonstrated compelling evidence that competition was dominating mortality. Most of the rest of the plots fell within the expectation for random mortality, and three fit neither the random nor the competition model. These results suggest that while competition is often playing a significant role in tree mortality processes in these forests it only infrequently governs those processes. In addition, the field assessments indicated a substantial presence of biotic mortality agents in trees that died.While competition is almost certainly important, demographics in these forests cannot accurately be characterized without a better grasp of other mortality processes. In particular, we likely need a better understanding of biotic agents and their interactions with one another and with competition.     

注干农药防治光肩星天牛的试验研究

对行道树、防风林杨树采用注干农药方法防治光肩星天牛成虫、幼虫的试验研究结果表明：以长效内吸注干乳油效果最好，具有传导快，杀虫效果好，残效期长的特点。长效内吸注干乳油防治结果：行道树罩笼接虫，成虫死亡率达９２．９％，室内饲喂注于后的枝条，成虫死亡率达９９．９％，大面积防风林成虫死亡率达９４．７％，总体被害率４．４％，幼虫１～２龄死亡率达８９．８％。对比了注干农药和农药涂干的效果，防治１～２龄幼虫注干防效比涂干防效高１８．６％。注于农药方法防治光肩星天牛可提高防治效果，降低防治成本，减少对环境的污染，并可兼防其它食叶性和刺吸性害虫。     

复方三氮唑核苷注射液对鸡新城疫病毒的抑制试验

将复方三氮唑核苷（毒菌杀平）注射液、三氮唑核苷液和盐酸吗啉双胍液分别稀释成2，10，20，100μl/L的溶液，分别与等量鸡新城疫病毒（NDV）液混合，其中含抗病毒药含量分别为0.025,0.125，0.250,1.250μg/mL。将混合液37℃感作2h，尿囊腔接种9-11日龄鸡胚，每组接种11个鸡胚，每胚0.1mL，37℃培养，每6-8h照蛋1次，死亡鸡胚及时取出冷冻，活胚孵化至96h全部取出，冷冻后测定血凝效价，计算病毒滴度和病毒灭活率。试验结果表明：含量为0.025,0.125,0.250,1.250μg/mL的毒菌杀平注射液、三氮唑核苷液、盐酸吗啉双胍液对NDV均有不同程度的抑制作用，复方制剂没有降低原抗病毒药的药效，三氮唑核苷对该NDV的抑制效果好于盐酸吗啉双胍。     

CO2气调对两种储粮害虫致死率的研究

谷蠹(Rhyzopertha dominica)成虫和杂拟谷盗(Tribolium con fusum)卵、幼虫、蛹及成虫对35%CO_2、11%O_2,35%CO_2、21%O_2,75%CO_2、11%O_2及75%CO_2、21%O_2 4种气调环境都很敏感,但35%CO_2对杂拟谷盗成虫致死率不高。杂拟谷盗卵、幼虫、蛹及成虫对高CO_2(75%)气调环境的敏感顺序为:卵>幼虫>蛹>成虫。     

乳酸菌富铁的研究

为了使铁离子转化为易被动物体吸收的微量元素,以防治仔猪因缺铁而造成的贫血等病症,本研究用乳酸菌富集铁元素。首先测得乳酸菌在硫酸亚铁和有机铁2种来源的铁元素中所能正常生长的最高铁离子浓度,然后加入适宜浓度的铁离子培养乳酸菌至最高活菌数。菌液离心后冲洗3次并烘干,用原子分光光度法测定乳酸菌干细胞内铁离子的含量,比较乳酸菌对2种形态铁元素的富集能力。最后做饲养试验。结果表明:乳酸菌对有机铁的耐受质量浓度(0.5 g/L)比硫酸亚铁(0.1 g/L)高;乳酸菌对有机铁的富集能力(1.590 mg/g)比硫酸亚铁(0.024mg/g)强。含有机铁的乳酸菌制剂对降低断奶仔猪死亡率有显著效果。     

甲酸乙酯的施药高度对仓内空间杀虫效果的影响

在储粮容量7000t的高大平房仓空仓内,设置一个高7.50 m、直径300mm的熏蒸室,分别在7.50m、5.61m、3.74m、1.87m和0.1m的高度放置试虫,先后从0.10m、3.74m和7.50m的高度施药,测定了甲酸乙酯对处于不同高度的赤拟谷盗(Tribolium castaneum(Herbst))和谷蠹(Rhyzopertha dominica(Fabricius))成虫的杀虫效果。结果为:在0.10m高度施药,甲酸乙酯对于靠近施药点的试虫可完全致死,而在1.87m及其以上高度处的害虫死亡率均显著低于施药点的死亡率。在高度3.74m处施药,施药点及其以下两种害虫的死亡率均显著大于施药点以上的害虫死亡率,3.74m及其以下的谷蠹均完全死亡,赤拟谷盗的死亡率则出现了0.1m处100%,1.87m和3.74m处则分别只有96.7%和81%。经7.50m高度施药,0.10m高度处的害虫死亡率达100%,且害虫死亡率出现自下而上递减的结果。本实验表明,作为熏蒸剂的甲酸乙酯在空间被施用后,静态条件下向上扩散且有效杀虫的高度小于2m;在高空施药后主要扩散趋势为向下运动(下沉),对施药点以下的害虫效果较好,建...     

Low reproductive success of leatherback turtles, Dermochelys coriacea, is due to high embryonic mortality

We examined the mechanism responsible for low reproductive success in leatherback turtles (Dermochelys coriacea) at Playa Grande, Costa Rica: low egg fertilization versus high rates of embryonic death. Leatherbacks at this beach had a high rate of fertility (=93.3%±2.5%, n=819). We incubated 10 eggs from every clutch encountered of 19 females during 3 months of the 1998-1999 nesting season. Fertility rate of some females decreased during the nesting season, but overall was high. Detection of fertility was difficult using standard methods because fertility rates cannot be determined accurately from nests excavated after hatching because of egg decomposition. Removal and incubation of eggs from nests provided a better estimate. Embryonic death, particularly in the beginning of incubation before embryos are visible to the unaided eye, was the cause of low hatching success in this population. Hatching success increased with increasing fertility and differed between females, with some mothers having 71-81% success and others 23-32%. Embryonic death and not low egg fertility drives poor recruitment at Playa Grande. Improved conservation of this species at Playa Grande will require a better understanding of the mechanism behind embryonic death.     

Reedbeds as refuges for water voles (Arvicola terrestris) from predation by introduced mink (Mustela vison)

The water vole has recently undergone a catastrophic decline in the UK. This has resulted from loss and fragmentation of suitable habitat leaving water vole populations highly vulnerable to the impact of predation by introduced American mink. However, at some reedbed sites water voles and mink have apparently coexisted for many years. To determine if reedbeds offer a refuge from predation, 70 voles were radio-tagged at three sites in England and overwinter mortality monitored. Water vole perception of predation risk was also assessed. Mortality was high (64%), predation by mustelids, including mink, being the chief cause. Experiments suggested that voles failed to perceive areas of highest predation risk. However, predation rate declined strongly with the distance water voles lived from a main water channel. Thus, reedbeds provide a refuge from predation, even by mink, and calculations suggest that they may support source populations enhancing the viability of water vole metapopulations. Consequently reedbeds are now being used as one focus for the conservation of water voles in England and Wales.     

捕捞网具逃逸死亡研究进展

幼鱼及非目标种类兼捕已成为许多网具作业共同存在的问题,提高网具选择性能是降低这种兼捕的重要途径。但是选择性能研究主要是基于从网具中逃逸后的鱼类较轻遭受到网具损害并最终存活。如果逃逸死亡率较高,即使选择性提高也是无宜的,因此应当将鱼类逃逸后生存能力作为网具改进效果的评价指标。本文主要由以下三个部分组成:(1)逃逸后死亡的主要影响因素概述,主要包括网具特征、作业时间、作业深度、渔获种类及体长、渔获量及环境因子等;(2)逃逸死亡对资源量和渔业管理决策的影响;(3)总结了近年来通过网具革新措施提高存活率的最新研究概况,如逃逸网片、分离栅及新型材料的应用等。综合分析,认为采取保护幼鱼和非目标种类的一系列措施尽管能够提高鱼类从网具的逃逸几率,但是并不能降低遭遇网具的概率,实施禁渔区、禁渔期制度管理,避免在幼鱼资源高密度区和产卵季节作业是降低这种未报告死亡的最重要的途径。