| 3 | 用光学多道分析仪测量高压钠灯的光谱辐照度(英文)显示文摘本文描述用光学多道分析仪(OMAⅢ)对高压钠灯的光谱辐照度测量,采用美国国家标准和技术研究院的光谱辐射照度标准灯FEL(1000瓦卤钨灯),测量光谱范围380nm到800nm。讨论了测量中的一些问题。 为了简明地估计和比较测量误差,引进了平均标准误差,即在测量范围内所有光谱辐照度标准误差的算术平均值。用于测量的12只高压钠灯是经过几百小时的稳定试验后挑选出来的,它们的平均标准误差在0.6%和1.9%之间,作为一个灯组的平均误差为1%。 利用测得的光谱辐照度,计算了光照度和积分辐照度,前者的标准误差从0.02%到0.26%,后者的从0.06到0.25%,都小于0.3%。 为了探索提高测量精度即降低测量的平均标准误差的可能,进行了改变仪器的曝光时间和每个读数的重复次数(扫描次数)的实验。结果表明,合理地选取这些参量可以改善测量的精度。 采样波长的移动和仪器内部杂散光的影响是存在于测量中的两个主要问题,本文对此作了分析和讨论。 | 胡荣生 T.Lush R.Saunders D.McSparron | 1992 | 照明工程学报1992，3，4： | 0 |
| 4 | Two decades of compositional and structural change in deciduous old-growth forests of Indiana,USA显示文摘Aims Using a network of permanent plots,we determined how multiple old-growth forests changed over an 18-19-year period at a state-wide scale.This examination of change allowed us to assess how the compositional and structural stability of each forest varied with site characteristics(topography,physiography and productivity)and stochastic disturbance.Methods In 2011,we resampled 150 plots distributed across five old-growth hardwood forests in Indiana,USA that were originally sampled in 1992-1993.Within each plot,we relocated and remeasured the diameter at breast height(dbh)of all trees(≥10.0 cm)present during the 1992-1993 sample,which allowed us to track their individual fates through time for growth and mortality calculations.Trees that grew to≥10.0 cm dbh since plot establishment were designated as ingrowth.The dbh and species of all saplings(stems≥2.0 cm but<10.0 cm dbh)were also recorded.For each forest,we calculated density(stems ha^(−1)),basal area(BABA;m^(2)ha^(−1))and importance value(relative density+relative BABA)/2 of trees by species.For saplings,density per ha was calculated by species for each forest.We also calculated annual mortality rate(AMR)for three diameter classes(10-29.9,30-59.9 and≥60 cm)and species richness(S),evenness(E)and Shannon-Weiner diversity(H')for the tree and sapling layers.Differences between years were compared for each forest using paired t-tests and Wilcoxon signed rank tests.Important FindingsAlthough we observed commonality in changes across some sites,our results suggest that these forests differ in their rates and trajectories of change.Changes in total stand BABA and density varied across sites and were influenced by past disturbance and mortality rates.We observed a general increase in the overstory dominance of Acer saccharum coupled with a general decrease in the dominance of Quercus section Lobatae(red oak group)species.Mortality of overstory trees present in 1992-1993 ranged from 27%to 49%over the study period(mean AMR 1.6-3.7%).Most sites experienced greater mortality of early and mid-successional species,but one site experienced heavy mortality of Fagus grandifolia,a shade-tolerant late-successional species.Shade tolerant species,A.saccharum in particular,dominated the sapling layer at most sites.However,recruitment of this species into larger size classes did not occur uniformly across all sites and the species was comparatively uncommon at one site.Overall,our results suggest that old-growth remnants,even within a single state,cannot be viewed as equivalent units with regard to research or management.Stochastic disturbance events and surrounding land use may have amplified effects on small scattered remnants.Therefore,continued monitoring of these rare,but biologically important forests is critical to their long-term management and protection. | Christy A.Lowney Bradley D.Graham Martin A.Spetich Stephen R.Shifley Michael R.Saunders Michael A.Jenkins | 2016 | Journal of Plant Ecology2016，9，3： | 0 |
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