Nitrogen uptake from 15N-enriched fertilizer by four tree crops in an Amazonian agroforest

Mixed tree cropping systems have been proposed for sustainable nutrient management in the humid tropics. Yet, the nutrient interactions between intercropped trees have not been addressed sufficiently. In the present study we compare the temporal and spatial patterns of the uptake of applied ¹⁵N by four different tree crops in a mixed tree cropping system on a Xanthic Ferralsol in central Amazônia, Brazil, during one year. Most of the N uptake occurred during the first two weeks. Very little N was recovered by peach palm (Bactris gasipaes), more by cupuassu (Theobroma grandiflorum) and annatto (Bixa orellana) and most by Brazil nut (Bertholletia excelsa). Due to tree pruning the total accumulation of applied ¹⁵N in the above-ground biomass of annatto decreased throughout the year. It remained constant in cupuassu and peach palm and increased in Brazil nut. Brazil nut showed an extensive root activity and took up more fertilizer N applied to neighboring trees than from the one applied under its own canopy in contrast to the other three tree crops. Therefore, trees with wide-spread root systems may not need to receive N fertilizer directly but can take up N applied to other trees in the mixed cropping system. This means that such trees may effectively decrease N leaching when intercropped with trees that have dormant periods or places with low N uptake, but also exert considerable resource competition.This revised version was published online in November 2005 with corrections to the Cover Date.     

2006年特大干旱中森林植被对农作物的防护作用

2006年四川发生了百年一遇的特大干旱。按照自然地理条件相近、森林覆盖率有较大差异的原则;同时,在同一行政区内按森林覆盖率的高低分成对照组。在县层面上,共3对对比县,在乡层面上共7对对比乡。对比县中,森林覆盖率高的一组森森覆盖率为34.20%～52.29%,平均为43.16%,森林覆盖率低的一组为16.60%～27.28%,平均为20.84%;对比乡镇中,森林覆盖率高的一组森林覆盖率为28.50%～56.23%,平均为41.29%,森林覆盖率低的一组为10.70%～19.12%,平均为14.61%。在干旱后期,调查了四川盆地丘陵区9个县14个乡镇主要农作物(水稻、玉米和红薯)的受灾率、成灾率和绝收率。调研结果表明,森林对农业的旱情具有一定的缓解作用。在县层次上,与森林覆盖率低的相比,森林覆盖率高的主要农作物(水稻、玉米和红薯)的平均受灾率、成灾率、绝收率分别降低16.6%、16.2%、4.0%;在乡镇层次上,与森林覆盖率低的相比,森林覆盖率高的主要农作物(水稻、玉米和红薯)的平均受灾率、成灾率、绝收率分别降低20.3%、19.7%、12.7%;与无农田防护林网相比,有农田防护林网的水稻平均受灾率、成灾率分别降低5.8%、22.8%,没有绝收现象,而无防护林的水稻平均绝收率为6.5%。     

《东北草本植物志》第1卷补正（V）

本节对东北蕨类植物的４科６属１０种２变种进行了补遗和订正，考证了名称及有关文献，讨论了所述分类群与其近亲分类群的区别特征。     

PGPB对红树植物木榄幼苗的接种效应

通过盆栽试验研究了植物促生菌(PGPB)对红树植物木榄幼苗的接种效应,供试菌为6种解磷菌(即B.amy,Vib,B.atr,Xan,B.Lic,P.M.)和5种固氮菌(即Au4,Phy,24S,JA4,cd),结果表明:(1)分别接种6种解磷菌株6个月后木榄幼苗的生长均得到了不同程度的促进,与对照相比,木榄苗高增加21.57%～9.54%,生物量增加27.49%～20.32%,叶片的氮含量增加33.33%～1.35%,叶片的磷含量增加24.42%～2.04%;经差异显著性检验,B.amy和Vib 2个菌种对木榄幼苗的促生效应比其它解磷菌株更明显;(2)分别接种5种固氮菌株6个月后木榄幼苗的生长均得到了促进,与对照相比,木榄幼苗的均高增加24.07%～10.22%,生物量增加32.36%～19.71%,叶片的氮含量增加23.39%～4.05%,叶片的磷含量增加32.79%～4.99%;差异显著性检验表明:Au4和Phy 2个菌种对木榄幼苗的促生效果比其它固氮菌更显著.     

Tephrosia species and provenances for improved fallows in southern Africa

Seeking an alternative to Sesbania spp. tree fallows, a Tephrosia species and provenance trial was conducted at Msekera Research Station, Chipata (Zambia) to evaluate eleven Tephrosia vogelii and three Tephrosia candida provenances. They were tested for biomass production, quality of biomass, resistance to root-knot nematodes, nitrogen release, and for their effects on soil nitrogen dynamics. At the end of 1.5 years, the T. candida provenances 02970, 02971 and 02972 from Madagascar produced two times greater amount of aboveground biomass than the T. vogelii provenances. There was little variability among the T. vogelii provenances in terms of litter and biomass production. Weed growth was significantly greater under T. vogelii than T. candida provenances. While Tephrosia vogelii provenance 98/02 from Zambia and T. candida 02972 were highly tolerant to the Meloidogyne incognita nematodes, T. vogelii provenances 02977, 98/03, 02973 from Kenya, Zambia and Malawi, respectively, were highly susceptible to the nematodes. The Tephrosia species and provenances showed a wide variability in terms of N, lignin and polyphenol concentration in their foliage. Mineralization of N in the foliage of T. candida provenances 02970 and 02971 and T. vogelii provenances 98/04 and 02974 from Malawi occurred rapidly within 14 weeks of incubation. At the end of the 2-year growth period, there was significantly greater total inorganic N under T. candida provenance 02972 (12.5 mg kg⁻¹) than T. vogelii (5 mg kg⁻¹) provenance Mungwi 98/02. Maize (Zea mays L.) yields after T. candida provenances were greater than those after T. vogelii provenances. Further testing of the most promising provenances is needed for their effects on subsequent maize yields under a range of farm conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同降水年型氮磷配施对冬小麦产量形成及水量平衡的影响

通过田间定位试验,探讨不同降水年型下氮磷配施对冬小麦产量形成及水分利用的影响,为改善麦田水分状况,建立与水分条件相适应的肥料组合模式提供依据.结果表明:(1)试验条件下,与对照处理相比,高氮高磷处理产量及水分利用效率均较高,平水年和干旱年的产量分别较对照增加68.37%和62.95%;水分利用效率分别较对照增加36.7...     

内蒙古锡林郭勒天然草原禾本科牧草根际18株固氮细菌的初步分类鉴定

采用16SrDNA测序方法对从内蒙古锡林郭勒天然草原四种主要禾本科牧草根际分离获得的18个固氮菌株进行属水平的鉴定,结果表明：其中7株属于土壤杆菌属（Agrobacterium）、3株属于产碱菌属（Alcali-genes）、1株属于固氮菌属（Azotobacter）、1株属于芽孢杆菌属（Bacillus）、3株属于假...     

花色多态植物紫薇花部综合特征与繁育系统

[目的]紫薇具有红色、紫色和白色等显著不同的花色以及形态、大小和颜色明显不同的2种雄蕊,使其成为花色多态型和异型雄蕊研究的良好材料.对紫薇花部综合特征和繁育系统进行系统研究,探究紫薇不同花色植株的繁殖策略以及2种雄蕊在传粉过程中的功能作用.[方法]通过野外定点观测,采用传粉昆虫调查、人工授粉以及人工控制套袋试验等方法对紫薇3种花色植株的花部形态特征、开花进程、传粉式样以及花朵的功能形态特征进行检测.[结果]1)3种花色植株的花期和单花开放进程基本相同(单花花期为4～5天).2)3种花色植株的花在形态特征上存在差异.3)3种花色植株的短雄蕊数表现为白色花植株＞紫色花植株＞红色花植株,花色间存在显著差异(P＜0.05);红色花植株的单花花粉量和P/O值显著低于其他2种花色植株(P＜0.05).4)3种花色植株的花粉活性和柱头可授性动态变化趋势相似;花粉寿命与柱头可授期有部分重叠,长雄蕊花粉活性最高时期早于柱头最佳可授期,短雄蕊的与柱头最佳可授期同步;白色和紫色花植株的柱头最佳可授期比红色花植株的长(约2h).5)2种雄蕊在形态、颜色、花粉量、人工控制试验条件下的结实率和结籽数以及传粉昆虫访花行为等方面都存在显著差异,说明2种雄蕊在传粉过程中存在功能分化,即黄色短雄蕊主要起招引昆虫作用,暗黄色长雄蕊主要起传粉作用;但2种雄蕊在花粉活性、花粉组织化学成分以及人工控制授粉后的结实率等方面均无显著差异,表明二者在生理上尚未分化;去除雄蕊试验表明,雄蕊的排列方式是影响2种雄蕊功能分化程度的重要因素.6)P/O值、套袋试验以及传粉昆虫观察结果表明,紫薇不存在无融合生殖、主动自交和自交不亲和现象,其交配方式是以异交为主、自交亲和的兼性异交繁育系统.7)传粉昆虫对红色花植株有明显偏好,访问该花色植株的频率显著高于其他2种花色植株(P＜0.01);人工授粉后,白色和紫色花植株的结实率显著提高.[结论]在自然条件下,紫薇的白色和紫色花植株存在一定的花粉限制.此时,增加对雄性功能的投入、延长柱头最佳可授期是其维持繁殖成效的适应策略;在传粉过程中,2种雄蕊既有分工,又有协作.2种雄蕊花药开裂时间不同步,花粉活力维持时间也不同,花粉的这种装配机制是紫薇提高花粉输出效率的繁殖策略.