Long-term trends of heron and egret populations in Italy, and the effects of climate, human-induced mortality, and habitat on population dynamics

Factors affecting bird population dynamics include climate, harvesting by humans, and habitat changes. Here, we describe the long-term (1972–2006) population trends of seven heron species in NW Italy, an area holding important European breeding populations of these species. Grey (Ardea cinerea), purple (Ardea purpurea), and squacco (Ardeola ralloides) herons, and little egrets (Egretta garzetta) exhibited a strong logistic increase, leveling off around year 2000 at 3–23 times their initial level. Black-crowned night herons (Nycticorax nycticorax) began by increasing like the former species but then dropped to initial levels. Such trends were found to be influenced by several candidate ecological factors, as assessed by ARIMA models. Specifically, grey herons increased following a decrease in human-induced mortality, as quantified by an index of hunting pressure, and an increase in winter temperatures. Little egrets increased mainly with the increase of the extent of ricefields, whereas squacco herons increased with increasing rainfall in the African wintering range. Black-crowned night herons were also positively affected by increasing African rainfall, but only during 1972–1988, whereas in later years competition with other herons could have affected the species’ decline. The improved protection of colony sites by special reserves was unlikely to be the primary trigger of the observed increase, although obviously important for the long-term population persistence. In conclusion, our study shows that heron populations of southern Europe are sensitive to environmental and climatic changes, as well as to temporal variation in human disturbance and changes in foraging habitats, though the importance of the different factors differs among species.     

钙盐及模拟干旱互作对大花套唇苣苔种子萌发和幼苗生长的影响

苦苣苔科原大花旋蒴苣苔(former Boea clarkeana Hemsl.)为我国特有的复苏植物,在最近的修订中被并入套唇苣苔属(Damrongia Kerr),更名为大花套唇苣苔[D. clarkeana(Hemsl.)C. Puglisi]。为了探究该植物对喀斯特特殊生境的适应机制,该文以大花套唇苣苔成熟种子为材料,通过观察钙盐和模拟干旱互作试验,研究了干旱和盐胁迫共同作用对其种子萌发和幼苗生长的影响。结果表明:钙盐及模拟干旱互作时,低浓度钙盐可减轻干旱对种子萌发和幼苗生长的抑制作用,且低程度的干旱与低浓度的钙盐相互作用时反而会促进种子萌发和幼苗生长; 低钙盐低干旱复合条件对大花套唇苣苔生长的促进作用体现了该物种对喀斯特地区保水性差的石灰岩土壤基质的专适性,避免了和其他植物直接生态位的竞争。     

高温和密度效应对棉蚜死亡和繁殖的影响

在室内采用叶子圆片培养基饲养棉蚜的方法,研究不同温度(32、34、36、38、40 ℃)和密度(每皿5、25、50、75)对棉蚜死亡和繁殖的影响.结果表明： 随着温度的升高、密度和持续天数的增加,棉蚜累计死亡率呈上升趋势.互补重对数模型模拟结果表明：β值随着密度的增加而减小,说明随着棉蚜密度的增加,温度对棉蚜的作用减弱;不同持续天数的γ_j值不同,说明棉蚜条件死亡率受温度和作用时间的共同影响.双因素方差分析结果表明,温度和密度显著影响棉蚜的繁殖率,且存在交互作用.32~36 ℃范围内,棉蚜繁殖率随密度的增加呈降低趋势,40 ℃条件下,不同密度棉蚜繁殖率没有差异,说明随着温度的升高,密度对棉蚜的作用逐渐减弱.即在不同的温度区间和密度范围内,温度和密度对棉蚜的作用大小、主次发生了改变.研究结果为棉蚜种群监测、预警和改进害虫控制方法提供了科学依据.     

Performance and mortality of farmed hares

Performance and mortality of hares were evaluated for 2 consecutive years in a large farm in Veneto Region (Northern Italy). On average, fertile reproductive pairs (n=318) gave birth 4.8 times and produced 11.4 live leverets, weaned 8.4 leverets and produced 7.0 growing hares (60 days) every year. Mean mortality was 3.6%, 22.9%, 9.7% and 2.5% in newborn (0 to 2 days of age), suckling (3 to 25 days), growing (26 to 60 days) and sub-adult (61 days until sale) hares, respectively. The main causes of mortality were enteric diseases (75.5%, 75.9% and 12.1% in suckling, growing and sub-adult hares, respectively), followed by respiratory diseases (3.4%, 8.0% and 36.2% in suckling, growing and sub-adult hares, respectively), starvation (11.3% and 8.8% in suckling and growing hares, respectively) and trauma (7.1%, 2.3% and 30.2% in suckling, growing and sub-adult hares, respectively). In reproducing hares, mortality was 24.7% and 15.4% in 2010 and 2011, respectively. Respiratory diseases (34.8%) and ulcerative pododermatitis (18.9%) were the most common pathological changes detected in reproducing hares. Farmed hares seem to be affected by diseases resembling those of rabbits reared under intensive conditions. It seems necessary to improve the husbandry of hares to reach satisfactory technical standards and to preserve their health.     

Effects of mycorrhizal fungi on plant populations

We discuss four potentially important interactions between mycorrhizal fungi and populations of plants. First, vesicular-arbuscular mycorrhizal colonization has been shown to increase reproduction (via both male and female functions) and offspring survival, and thus it can increase population size, at least in the short term. This is undoubtedly important to wild plant species and especially to those whose success depends on high rates of reproduction such as early successional annuals. Second, the positive response in growth and reproduction to vesicular-arbuscular mycorrhizal colonization may be inversely related to plant population density. All else being equal, this would tend to stabilize the density of natural plant populations over time. It may also explain why positive responses to mycorrhizal inoculation of dense crops are rare. Third, vesicular-arbuscular mycorrhizal fungi can increase inequality in size and reproduction among plants within a population. Mycorrhizal fungi may thus exaggerate the genetic overrepresentation in the next generation of the most robust individuals in the current generation. Fourth, established mycorrhizal plants may serve as important sources of inoculum for initially nonmycorrhizal, conspecific seedlings. This may affect regeneration, and could contribute to patchy distributions of species within the community.     

Factors associated with neonatal lamb mortality

Three factors were associated with lamb neonatal mortality: birthweight (P<0.003), number of lambs born per ewe (P<0.001) and lamb sex (P<0.32). Lamb birthweight had the greatest predictive power for survival during the neonatal period. The neonatal mortality rate was 14.3%. The age specific mortality for lambs one day old was 7.9% (P<0.05). Seventy-nine percent of the lambs that died, did so by the end of the fourth post-natal day. Starvation was associated with 58.3% (P < 0.05) of the lamb deaths.     

Ecological role of physical dormancy in seeds of Oxytropis racemosa in a semiarid sandland with unpredictable rainfall

Aims Seed dormancy and the soil seed bank are crucial to plant regeneration strategy, especially in semiarid ecosystems with unpredictable precipitation. The aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis racemosa, a dominant perennial herb in Mu Us Sandland of semiarid China.Methods Germination and imbibition experiments on fresh intact and scarified seeds of O. racemosa were used to identify physical dormancy (PY) in seeds of this species. Soil seed bank dynamics, timing of seedling emergence and the fate of buried seeds in the natural habitat were investigated.Important findings PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment. The soil seed bank exhibited seasonal changes in the number of seeds, which was highest in September and lowest in July. Seeds buried at different sand depths gradually lost dormancy; 20–42% of the seeds remained dormant after 20 months of burial. Dormancy break occurs gradually throughout the year. Our results indicate that O. racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environment, where the amount of precipitation during the growing season is highly variable.     

西域青荚叶实生苗驯化的初步研究

通过对西域青荚叶实生苗驯化方面的实验,得出其驯化成活是各种环境因子综合作用的结果,与原生环境相似的适当的光照(弱、中光)、湿度(高、中湿度)、土壤肥力(高、中肥力)有助于驯化成活.