Aseptic micropropagation of Rhododendron P.J.M. hybrids

Summary

Shoot tips established in vitro better than single nodes. Five-cm shoot tips gave better Stage I results than 2-cm shoot tips. The best microshoot proliferation rates were obtained with isopentenyladenine (2iP) at 5 and 10 mg l^?1; tetrahydropyranyl-benzyladenine was ineffective. Microshoots rooted well, regardless of the level of 2iP in the Stage II medium. Stem-cutting-macropropagated plants generally were more variable in height, had less basal branching and were more erect than plants from microculture.     

旱塬区林地及耕地土壤水分动态变化研究

采用烘干法对采集于渭南旱塬地中耕地与林地的土壤样本进行了土壤水分含量的测定分析。结果表明:从整体来看,渭南市旱塬上耕地与林地土壤水分在10月份表现为2m以上土壤水分变化幅度较大,2～5m变化幅度较小,其主要原因是受到降水影响;11月份、2月份受冬季气候的影响,土壤水分含量整体偏高,变化幅度不大,不同的是11月份耕地在4～5m的范围内变化幅度相对较大,林地在0～1.5m范围内变化幅度大,2月份只有林地在4.5～5m的范围内变化幅度较大;3月份和4月份受春旱的影响,土壤含水量整体偏低,变化幅度较小,不同的是3月份耕地在0～0.6m和1.6～2.2m的范围内变化幅度大,林地在1.4～2.0、2.0～3.2和4.2～4.6m这3个区间内土壤含水量变化幅度较大,4月份只有耕地在2.6～3.2m的范围内变化幅度较大。     

Population Dynamics of Songbirds in the Boreal Mixedwood Forests of Alberta,Canada: Estimating Minimum and Maximum Extents of Spatial Population Synchrony

Ecological phenomena vary over space and time and interpretation of these processes also varies depending on the measurement scale. As the spatial scale of observation increases and decreases, changes in population abundance will likely exhibit alternating patterns of asynchrony and synchrony. While the study of how and why population dynamics change with spatial scale of measurement is intrinsically interesting, most population ecologists seek to study mechanisms of population change on a discrete study area. Our study develops methods that population ecologists can use to determine spatially appropriate sampling designs, and demonstrates how such spatial scales can be determined for 25 species of songbirds using long-term data from the boreal mixedwood forest of Alberta, Canada. To determine minimum scales of synchrony in population dynamics, we calculated the average correlation of changes in population abundance over time across different numbers of fixed-radius point-count samples. We then used a randomization test to remove the effect of number of replicates from the determination of appropriate spatial scale. The maximum extent of synchrony was estimated as the distance where population dynamics were no longer correlated. Estimates of the minimum scale of synchrony differed between species, ranging from 3.1 to 18.6 ha. The maximum scale of synchrony was estimated to be greater than or equal to 8 km for 14 of the 25 species examined, and to be greater than or equal to 70 km for Tennessee Warbler (Vermivora peregrina). Maximum spatial extents were significantly correlated with body mass and territory size.     

荔枝年生长周期内N、P、K营养动态规律与施肥管理体系

通过3年大田试验探索荔枝年生长周期内N、P、K营养规律,验证由高氮、高磷钾、高钾复合肥组成的荔枝平衡施肥管理措施的适用性。结果表明,荔枝年生长周期内,收获期N、P、K营养水平降至最低,随后因施肥而迅速恢复,在秋梢老熟到花芽分化期达年周期内最大值,此后随着开花结果N、P、K营养水平逐渐下降,至新的收获期又降至最低水平。秋梢和果枝的N、P、K水平因生长期的不同而明显变化,然而肥料用量(3～5kg/树)和N∶P∶K比例对树体N、P、K水平的影响较小。每个生育期结果母枝的N、P、K含量依次为N>K>P。收获期到开花前是树体营养恢复阶段,开花到果实生长发育期是消耗体内贮藏态N、P、K的过程。在荔枝年生长周期内,分别在收获期、秋梢老熟期和坐果期施用高氮复合肥、高磷钾复合肥和高钾复合肥能保障年周期内荔枝树体N、P、K营养水平处于最佳状态。