Efficacy of Organic Soil Amendments for Management of Heterodera glycines in Greenhouse Experiments

In a repeated greenhouse experiment, organic soil amendments were screened for effects on population density of soybean cyst nematode (SCN), Heterodera glycines, and soybean growth. Ten amendments at various rates were tested: fresh plant material of field pennycress, marigold, spring camelina, and Cuphea; condensed distiller’s solubles (CDS), ash of combusted CDS, ash of combusted turkey manure (TMA), marigold powder, canola meal, and pennycress seed powder. Soybeans were grown for 70 d in field soil with amendments and SCN eggs incorporated at planting. At 40 d after planting (DAP), many amendments reduced SCN egg population density, but some also reduced plant height. Cuphea plant at application rate of 2.9% (amendment:soil, w:w, same below), marigold plant at 2.9%, pennycress seed powder at 0.5%, canola meal at 1%, and CDS at 4.3% were effective against SCN with population reductions of 35.2%, 46.6%, 46.7%, 73.2%, and 73.3% compared with control, respectively. For Experiment 1 at 70 DAP, canola meal at 1% and pennycress seed powder at 0.5% reduced SCN population density 70% and 54%, respectively. CDS at 4.3%, ash of CDS at 0.2%, and TMA at 1% increased dry plant mass whereas CDS at 4.3% and pennycress seed powder at 0.1% reduced plant height. For Experiment 2 at 70 DAP, amendments did not affect SCN population nor plant growth. In summary, some amendments were effective for SCN management, but phytoxicity was a concern.     

Soil calcium content as the driving factor for vegetative structure and soil microbial function diverging across a fire chronosequence of the boreal forests in northeast China

中国东北地区北方森林土壤钙对植被结构和土壤功能随火烧序列恢复趋势分化的驱动作用随着火后恢复时间的延长,各生物物理因子对森林群落结构恢复和重建的重要性也发生着变化。本研究的主要目的是明确我国北方森林在火灾干扰后地上植被和土壤微生物功能的关键恢复时期及其主导性驱动因子。在东北大兴安岭林区,选择不同时期的火烧林地,组成一个50年的火烧演替序列,分析随火烧后恢复时间的增加,乔木、灌木和草本物种的生物量在整个群落中所占比重的动态变化特征。同时,采集不同火烧林地的土壤样品,分析其养分含量、微生物生物量以及酶活性等理化指标,并以这些理化数据为基础,估算土壤微生物的生长效率和碳素利用效率,以反应土壤微生物功能随火烧时间的演变规律。研究结果发现,在选定的火烧序列内,不同功能群物种在森林群落的恢复和重建中的贡献表现出明显的时期变异性。草本物种的比重从最初的75%下降到1.5%,而乔木物种的比重则从火烧 初期的0.04%上升到后期的70%。土壤微生物的生长效率和碳素利用效率平均为0.242和0.236,在火烧恢复的第9、15和31年的取值明显大于火烧后的第2和3 年。火烧后恢复时期也影响了土壤中金属离子的含量,土壤中钙和铁的含量都在火烧序列后期得到明显提高,其中钙的含量与群落中木本物种间呈正相关关系,而与微生物功能间呈负相关关系。在本研究选定的火烧序列内,火烧干扰后的第15和31年是地上群落结构和土壤微生物功能恢复的关键期,地上和地下恢复过程在这两个时期呈现出分异趋势,而土壤中钙含量的变化对这一分异趋势发挥了一定的驱动作用。     

Application of a Sex Pheromone,Pheromone Analogs,and Verticillium lecanii for Management of Heterodera glycines

A mutant strain of the fungus Verticillium lecanii and selected bioregulators of Heterodera glycines were evaluated for their potential to reduce population densities of the nematode on soybean under greenhouse conditions. The bioregulators tested were the H. glycines sex pheromone vanillic acid and the pheromone analogs syringic acid, isovanillic acid, ferulic acid, 4-hydroxy-3-methoxybenzonitrile, and methyl vanillate. A V. lecanii-vanillic acid combination and a V. lecanii-syringic acid combination were also applied as treatments. Syringic acid, 4-hydroxy-3-methoxybenzonitrile, V. lecanii, V. lecanii-vanillic acid, and V. lecanii-syringic acid significantly reduced nematode population densities in the greenhouse tests. Results with vanillic acid, isovanillic acid, and ferulic acid treatments were variable. Methyl vanillate did not significantly reduce cyst nematode population densities in the greenhouse tests.     

Field Efficacy of Verticillium lecanii,Sex Pheromone,and Pheromone Analogs as Potential Management Agents for Soybean Cyst Nematode

A soybean cyst nematode sex pheromone (vanillic acid), chemical analogs of the pheromone, and the fungus Verticillium lecanii were applied in alginate prills (340 kg/ha) to microplots and small-scale field plots as potential management agents for Heterodera glycines on soybean. In 1991 microplot tests, treatment with V. lecanii, vanillic acid, syringic acid plus V. lecanii, or vanillic acid plus V. lecanii lowered midseason cyst numbers compared with the untreated susceptible cultivar control, autoclaved V. lecanii treatment, or aldicarb treatment, At-harvest cyst numbers were lowest with V. lecanii and with vanillic acid treatments. Aldicarb treatment reduced midseason cyst numbers in 1992. There were no differences among seed yields either year. In the field trials, numbers of cysts were reduced one or both years with aldicarb, ferulic acid, syringic acid, vanillic acid, or 4-hydroxy-3-methoxybenzonitfile treatments, or with a resistant cultivar, compared to an untreated susceptible cultivar. Highest yields were recorded after treatment with 4-hydroxy-3-methoxybenzonitrile (1991), methyl vanillate (1992), and aldicarb (1992). These studies indicate that some chemical analogs of vanillic acid have potential for use in soybean cyst nematode management schemes.     

退化红壤区人工林土壤的可溶性有机物、微生物生物量和酶活性

以江西省泰和县退化红壤区18年生马尾松纯林(Ⅰ)、马尾松 枫香 木荷混交林(Ⅱ)、木荷纯林(Ⅲ)和枫香纯林(Ⅳ)4种人工林林分为对象,并以自然恢复的无林荒草地为对照(CK),研究其土壤的可溶性有机碳(SOC)、氮(SON),微生物生物量碳(MBC)、氮(MBN)和土壤酶活性的变化.结果表明： 在0～10 cm土层,各林分类型的土壤SOC、SON含量分别为354～1007 mg·kg^-1和24～73 mg·kg^-1,MBC、MBN含量分别为203～488 mg·kg^-1和24～65 mg·kg^-1,脲酶和天门冬酰胺酶活性分别为95～133 mg·kg^-1·d^-1和58～113 mg·kg^-1·d^-1.不同林分类型之间SOC、SON含量为Ⅳ>CK > Ⅲ>Ⅰ>Ⅱ,MBC、MBN含量为CK>Ⅳ>Ⅲ>Ⅰ>Ⅱ,天门冬酰胺酶活性为Ⅳ>CK>Ⅲ>Ⅱ>Ⅰ,差异显著,而脲酶活性没有显著差异.随着土层加深,SOC、SON、MBC、MBN、脲酶及天门冬酰胺酶活性下降.在0～20 cm土层,SOC、SON、MBC、MBN、全碳和全氮两两之间达极显著相关.天门冬酰胺酶活性与SOC、SON、MBC、MBN、TSN、全碳、全氮极显著相关;而脲酶活性与SON、MBCMBN、TSN、全碳显著相关.     

Diverse Optical and Photosynthetic Properties in a Neotropical Dry Forest during the Dry Season: Implications for Remote Estimation of Photosynthesis1

Using optical and photosynthetic assays from a canopy access crane, we examined the photosynthetic performance of tropical dry forest canopies during the dry season in Parque Metropolitano, Panama City, Panama. Photosynthetic gas exchange, chlorophyll fluorescence, and three indices derived from spectral reflectance (the normalized difference vegetation index, the simple ratio, and the photochemical reflectance index) were used as indicators of structural and physiological components of photosynthetic activity. Considerable interspecific variation was evident in structural and physiological behavior in this forest stand, which included varying degrees of foliage loss, altered leaf orientation, stomatal closure, and photosystem II downregulation. The normalized difference vegetation index and the simple ratio were closely related to canopy structure and absorbed radiation for most species, but failed to capture the widely divergent photosynthetic behavior among evergreen species exhibiting various degrees of downregulation. The photochemical reflectance index and chlorophyll fluorescence were related indicators of photosynthetic downregulation, which was not detectable with the normalized difference vegetation index or simple ratio. These results suggest that remote sensing methods that ignore downregulation cannot capture within‐stand variability in actual carbon flux for this diverse forest type. Instead, these findings support a sampling approach that derives photosynthetic fluxes from a consideration of both canopy light absorption (e.g., normalized difference vegetation index) and photosynthetic light‐use efficiency (e.g., photochemical reflectance index). Such sampling should improve our understanding of controls on photosynthetic carbon uptake in diverse tropical forest stands.