Pulses of seed release in riparian Salicaceae coincide with high atmospheric temperature

Riparian shrubs and trees in the Salicaceae family release their seeds when floods that create nursery sites for germination are more frequent, but little is known about the factors controlling temporal variations in seed release within the seed release period. The seed release of three riparian tree species dominating European floodplain forests (Populus alba L., Populus nigra L., and Salix alba L.) was monitored in spring 2007 and 2008 using seed traps placed along the Middle Ebro River, NE Spain. Correlations relating biweekly seed rain intensity (seeds trapped per square meter) to meteorological (atmospheric temperature, cumulative precipitation, relative humidity, solar radiation, mean wind speed) and hydrological (river discharge) variables were investigated. The best combination of environmental variables explaining seed rain intensity was identified using an Akaike information selection criterion‐based backward selection, after accounting for temporal autocorrelation both in seed rain intensity and environmental variables. Seed rain correlated positively with temperature for P. alba, P. nigra, and S. alba, though its effect decreased with relative humidity for P. nigra. Our results can help fine‐tune the design of environmental flows to promote sexual recruitment of Salicaceae trees: Planning water releases during the hottest days of the seed dispersal period, when seed rain peaks, should maximize seed germination density and thus increase the potential for successful seedling establishment.     

燃烧器摆角同步性对切圆锅炉再热汽温和壁温偏差的影响研究

为解决某电厂660 MW超超临界机组切圆锅炉日常运行中再热汽温和壁温偏差大、管壁易超温和再热汽温不足等问题,本文研究了燃烧器摆角同步性对汽温和壁温偏差的影响特性。热态运行时,只有将炉外四个角的燃烧器摆角设置在不同位置时,才能在保证管壁不超温的前提下将再热汽温提升至设计值,初步判断造成这一现象的根本原因是炉内四个角燃烧器摆角不同步造成。机组冷态停炉检查时发现,有近一半的燃烧器摆角炉内外定位不一致导致四角不同步,对炉内外燃烧器摆角进行了重新定位。消缺处理后,再将炉外四个角的燃烧器摆角设置在同一位置,再热器两侧的汽温和壁温偏差均有所降低,机组状态显著改善。额定负荷下,在最高点再热器管壁温度降低了8.1℃的前提下,两侧再热汽温偏差降低至1.0℃的同时,再热汽温提升至619.8℃。