The effects of season,daylight saving and time of sunrise on serum cortisol in a large population

Cortisol is critical for maintenance of health and homeostasis and factors affecting cortisol levels are of clinical importance. There is conflicting information about the effects of season on morning cortisol and little information on the effects of sunlight on population cortisol assessment. The aim of this study was to assess whether changes in median serum cortisol occurred in a population in conjunction with changing seasons, daylight saving time (DST) or time of sunrise. We analysed serum cortisol results (n?=?27 569) from a single large laboratory over a 13-year period. Subjects with confounding medications or medical conditions were excluded and data analysed in 15-minute intervals. We assessed the influence of traditional seasons, seasons determined by equinox/solstice, DST and time of sunrise on median cortisol. The median time of cortisol collection did not vary significantly between seasons. Using traditional seasons, median cortisol was lowest in summer (386?nmol/L) and spring (384?nmol/L) with higher cortisol in autumn (406?nmol/L) and winter (414?nmol/L). Median cortisol was lowest in the summer solstice quarter with significant comparative increases in the spring equinox quarter (3.1%), the autumn equinox quarter (4.5%) and the winter solstice quarter (8.6%). When cortisol was modelled against time, with adjustment for actual sunrise time on day of collection, for each hour delay in sunrise there was a 4.8% increase in median cortisol (95% CI: 3.9–5.7%). In modelling to explain the variation in cortisol over the morning, sunrise time was better than season in explaining seasonal effects. A subtle cyclic pattern in median cortisol also occurred throughout the months of the year. A 3-year trial of DST allowed comparison of cortisol in DST and non DST periods, when clock time differed by one hour. There was modest evidence of a difference in acrophase between DST and non DST cortisol (p?=?0.038), with DST peak cortisol estimated to occur 58?minutes later than non-DST peak. In summary, we found that time of sunrise and time of cortisol collection were the most important factors influencing median cortisol. For each hour later that the sun rose there was an almost 5% increase in median cortisol. There was significant seasonal variability with lowest cortisol noted in summer coinciding with the earliest sunrise time. This is an important finding which is consistent with the understanding that light is the major zeitgeber in entrainment of the human circadian cortisol rhythm. Our data suggest this rhythm is resistant to the arbitrary changes in clock time with daylight saving.     

Home range and habitat use of male Reeves's Pheasant(Symaticus reevesii)during winter in Dongzhai National Nature Reserve,Henan Province,China

Home range and habitat use of male Reeves's Pheasant(syrmaticus reevesii)were studied during winter of 2001～2002 and 2002～2003 in the Dongzhai National Nature Reserve,Henan Province.Results from five individuals of Reeves's Pheasant with over 30 relocations,indicated that the average size of home range was 10.03±1.17 hm2 by Minimum Convex Polygon method.8.60±0.35 hm2 by 90% Harmonic Mean Transformation method,and 9.50±1.90 hm2 by 95% Fixed Kernel method.It was observed that the winter range is smaller than that in the breeding season.The mean core area of the home range was found to be 1.88±0.37 hm2.Although the habitat composition of the core area varied greatly for individuals,a large part of the habitats used were composed of conifer and broadleaf mixed forests,masson pine forests,fir forests,and shrubs.Habitat use within the study area was non-random,while habitats within home ranges were randomly used.Habitat use was dictated by tree diameter at breast height,shrub height and coverage at 2.0 m.The proximity between forests and shrubs were also found to be important in providing refuge for the birds during winter.Recommendations for conservation management include protecting the existing habitats in Dongzhai National Nature Reserve,increasing suitable habitat for Reeves's Pheasant through artificial plantations(e.g.firs),and restoring some parts of the large shrub area into forests.     

Home range and habitat use of male Reeves’s pheasant (Syrmaticus reevesii) during winter in Dongzhai National Nature Reserve, Henan Province, China

Home range and habitat use of male Reeves’s pheasant (Syrmaticus reevesii) were studied during winter of 2001∼2002 and 2002∼2003 in the Dongzhai National Nature Reserve, Henan Province. Results from five individuals of Reeves’s pheasant with over 30 relocations, indicated that the average size of home range was 10.03 ± 1.17 hm² by Minimum Convex Polygon method, 8.60 ± 0.35 hm² by 90% Harmonic Mean Transformation method, and 9.50 ± 1.90 hm² by 95% Fixed Kernel method. It was observed that the winter range is smaller than that in the breeding season. The mean core area of the home range was found to be 1.88 ± 0.37 hm². Although the habitat composition of the core area varied greatly for individuals, a large part of the habitats used were composed of confier and broadleaf mixed forests, masson pine forests, fir forests, and shrubs. Habitat use within the study area was non-random, while habitats within home ranges were randomly used. Habitat use was dictated by tree diameter at breast height, shrub height and coverage at 2.0 m. The proximity between forests and shrubs were also found to be important in providing refuge for the birds during winter. Recommendations for conservation management include protecting the existing habitats in Dongzhai National Nature Reserve, increasing suitable habitat for Reeves’s Pheasant through artificial plantations (e.g. firs), and restoring some parts of the large shrub area into forests. __________ Translated from Biodiversity Science, 2005, 13 (5) [译自: 生物多样性, 2005,13(5)]     

The influence of small-scale variation in habitat on winter trout distribution and diet in an afforested catchment

(1) Habitat influences on trout distribution and diet at a reach scale were analysed over a single winter in a conifer-afforested catchment in Ireland, in an area subject to very low levels of atmospheric pollution. (2) A total of 234 salmonids were sampled from which 1194 individual prey items were recovered. Salmonids were sampled at eleven sites over a 2 km stretch of the river Douglas, a third order stream of the river Araglin in the Munster Blackwater, Co. Cork, Ireland. (3) In this winter study, water depth and flow primarily influenced trout distribution. (4) Stepwise multiple regression was used to identify the most influential environmental factors on trout metrics. Trout biomass was positively correlated to maximum depth and the percentage of pool area within sites, but density and condition were not significantly influenced by habitat variation at the reach scale. (5) The results from diet analysis suggest that trout are heterogeneous generalist feeders in winter, preying mainly on Trichoptera and Ephemeroptera species. Prey diversity in the diet of individuals throughout the study was positively correlated to the percentage of deciduous vegetation, undercut banks and coniferous vegetation, whilst the prey sub-population diversity at site scale was not related to any of the habitat variables measured.     

白冠长尾雉雄鸟的冬季活动区与栖息地利用研究

2001年和2002年冬季,利用无线电遥测技术在河南董寨国家级自然保护区内对白冠长尾雉(Syrmaticusreevesii)雄鸟的冬季活动区和栖息地利用进行了研究。对遥测位点超过30个的5只雄性个体的研究表明,白冠长尾雉雄鸟的冬季活动区面积为10.03±1.17hm2(最小凸多边形法,MCP)、8.60±0.35hm2(90%调和平均转换法,90%HMT)和9.50±1.90hm2(95%固定核法,95%FK),明显小于其繁殖期的活动区面积。核心区面积为1.88±0.37hm2。核心区的栖息地组成在个体间变化较大,但主要是针阔混交林、松林、杉木林和灌丛。在研究区尺度上,白冠长尾雉雄鸟对栖息地有明显的选择性,但在活动区内则是随机利用栖息地。乔木胸径、灌木高度、2.0m层盖度及灌丛与森林的距离对雄性白冠长尾雉冬季的栖息地选择有重要影响。根据本项研究结果,我们建议在白冠长尾雉的栖息地管理中首先应加强对现存栖息地的保护,同时应通过适当的造林来扩大栖息地面积,此外还要注意对大面积的现有灌丛进行改造。     

山西五鹿山褐马鸡不同季节的空间分布与栖息地选择研究

1997～1998年在山西省五鹿山自然保护区内对世界珍禽褐马鸡(Crossoptilon mantchuricum)越冬期与繁殖期的空间分布模式及其变化规律进行了研究,同时探讨了种群空间分布模式与栖息地结构特征之间的关系。经Pois—son函数和χ^2检验,发现褐马鸡在越冬期和繁殖期均为聚集分布,但越冬期的聚集程度更为明显。通过对栖息地可利用率与实际利用率的比较,发现褐马鸡在越冬期与繁殖期对栖息地的利用存在显著性差异：越冬期褐马鸡对阔叶林具有明显的负选择性;进入繁殖期后,褐马鸡对落叶阔叶林和灌丛的利用率显著增加,而对针叶林和针阔混交林的利用率有所减少。对两个时期的栖息地样方进行判别分析,发现草本植物数量、草本植物平均高度、乔木胸径、乔木高度是影响褐马鸡越冬期与繁殖期栖息地选择的主要因子。研究结果表明,褐马鸡种群的空间分布模式及其变化,与栖息地结构以及空间资源分布的季节性变化有关。在越冬期,由于温度、降雪等气候因素的影响,草本植物都已枯萎,落叶阔叶林的郁闭度较低,隐蔽条件较差,褐马鸡活动的区域范围受到一定的限制,此时褐马鸡常常在郁闭度较高的针叶林或针阔混交林中,并聚集形成较大的群体,共同取食,聚集分布的程度较高;进入繁殖期后,随着落叶阔叶林郁闭度增大以及林下、灌草丛中草本植物种类和数量的增多,褐马鸡群体逐渐变小,多以配偶对的形式活动,空间聚集程度降低。但由于褐马鸡对栖息地具有严格的选择性,许多配偶对主要集中在质量较好的区域内占区和营巢,因此在大尺度上褐马鸡种群的空间分布仍为聚集型分布。     

2006年冬季南海北部浮游植物生物量和初级生产力及其环境调控

通过2006年2月在南海北部现场调查所获得的数据分析研究了海域的浮游植物现存量和生产力,结果表明冬季浮游植物的分布特征与东北季风引起的环流场的变化关系密切。调查海域水柱平均Chla浓度的变化范围为0.03～1.21mg·m-3（平均（0.33±0.33）mg·m^-3）,高值区出现在广东沿岸及海南岛东部附近海域;初级生产力的分布范围为41.3～1040.0mgC·m^-2d^-1。由于东北季风引起近岸水体混合剧烈,不利于浮游植物生长,因此虽然沿岸带Chla浓度（（0.53±0.50）mg·m^-3）较高,但初级生产力却是最低的,只有41.3mgC·m^-2d^-1,同时冬季反气旋涡强度下降和底层富营养水的涌升,营养盐充足,因此开阔海的Chla浓度（（0.31±0.30）mg·m^-3）和初级生产力（（631.3±578.0）mgC·m^-·2d^-1）均高。浮游植物粒度级份测定表明,Pico级份对冬季南海北部浮游植物现存量和生产力的贡献很大,特别是在开阔海区,分别占47%和66%。