Bird,weed and interaction effects on yield of irrigated lowland rice

Weeds and grain feeding birds are the two main biological causes of yield losses in irrigated rice in Africa. To quantify the single and combined effect of these biological constraints on rice yields, and to investigate whether weeds attract birds and thereby contribute to increased bird damage, a three-year factorial experiment was set-up in the Senegal River Valley. We tested two management factors (bird and weed management), each with two levels (‘complete’ and ‘absent’), and one crop cycle factor also with two levels (Sahel 202, a medium-cycle and Sahel 108, a short-cycle rice cultivar). Season-long competition from weeds resulted in high but predictable yield losses ranging from 50% to 75%, with lower yield losses for the medium-cycle cultivar Sahel 202 in two of the three seasons. Due to the nature of the pest, season-long exposure to birds resulted in less predictable yield losses ranging from 13% to as high as 94%, with high seasonal variation. In two seasons, much lower bird-inflicted yield losses were observed in the short-cycle cultivar Sahel 108, whereas in one season the medium-cycle cultivar Sahel 202 was much less damaged. When rice was exposed to both weeds and birds, the relative yield losses ranged from 80 to 99%. The yield reducing effect of weeds and birds was never additive. Bird visits to a weedy crop were more frequent compared to a weed-free crop at least in the early rice grain filling stages. This attraction of birds by weeds resulted in an additional yield loss in five of the six cases, ranging from 2 to 62%. Bird-inflicted yield losses in irrigated rice may be reduced by keeping the crop, as much as possible, free from weeds.     

Rice Grain Damage by Combination and Sequence Infestations by the Rice Leaffolder,Cnaphalocrocis medinalis Guenee (Lepidoptera: Pyralidae), and the White-Backed Rice Planthopper,Sogatella furcifera Horváth (Hemiptera: Delphacidae)

The rice leaffolder (RLF), Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae), and the white-backed rice planthopper (WBPH), Sogatella furcifera Horváth (Hemiptera: Delphacidae), are major insect pests in China and several other Asian countries. These two pests commonly occur simultaneously or in a temporal sequence. Thus, the investigation of the effect of complex infestations or temporal sequence infestations by these pests on rice yield has a practical significance for the control of these pests. The present study comprised experiments with the following four different variables in potted rice at the tillering stage: single pest species infestation, complex infestation, complete combination infestation and temporal sequence infestation (C. medinalis infestation prior to S. furcifera and S. furcifera infestation prior to C. medinalis). The results showed that the four infestations resulted in a significant decrease in 1000-grain weight (1000GW) and rate of yield loss (RYL) but an increase in blighted grain rate (BGR), with a significant positive correlation with the infestation density. However, the influences of the complex infestation, complete combination infestation or sequence infestation on the 1000GW, BGR and RYL were greater than those of the single pest species infestations but did not have addition effects, i.e., the effects of the complex infestation and combination infestation or sequence infestation on the 1000GW, BGR and RYL were less than the additive effects of the two single pest species infestations at the same densities. In the condition of the same total infestation pressure, no significant differences in the 1000GW, BGR and RYL were found between C. medinalis infestation prior to S. furcifera and S. furcifera infestation prior to C. medinalis as well as between the sequence infestation and the complex infestation.     

施用不同氮肥对盐碱地湖南稷子生产性能以及养分吸收的影响

为探讨盐碱地湖南稷子(Echinochloa frumentacea)高效生产的最佳施氮种类和施氮量,采用单因素随机区组设计,通过在湖南稷子拔节期设置不施肥(CK)、尿素和硫酸铵(N1,N2)轻施肥(F1:50 kg·hm^-2)、中施肥(F2:100 kg·hm^-2)、重施肥处理(F3:150 kg·hm^-2),研究不同氮肥和施氮水平下湖南稷子田间农艺性状、养分吸收及氮肥利用率的变化,探讨盐碱地湖南稷子实现高效生产的适宜氮肥和施氮量。结果表明：与对照相比,施氮量为F2和F3时能够显著提高盐碱地湖南稷子产量及氮磷钾吸收量(P<0.05),植株不同部位氮含量上升,施氮量F3时能够显著提高氮肥利用效率(P<0.05),且同一施氮量下追施硫酸铵后湖南稷子产量、养分吸收及氮肥利用率均高于尿素。综上所述,氮肥追施量在150 kg·hm^-2时,有利于盐碱地湖南稷子的产量的提升和养分的吸收,且同一条件下追施硫酸铵较追施尿素效果显著。     

多梯度氮磷添加对高寒草甸植物群落生物量与氮磷含量的影响

为研究不同梯度氮、磷单独及混合添加对高寒草甸植物群落生物量、植物养分含量及化学计量比的影响,本实验分析了青海省门源县典型高寒草甸植物群落地上总生物量,功能群水平地上生物量,植物全氮、全磷含量及氮磷比对多梯度氮、磷添加的响应情况。结果表明：氮、磷添加均对群落地上生物量影响极显著(P<0.001);氮添加对禾草类和豆科生物量影响极显著(P<0.001);磷添加对禾草类和莎草类生物量影响极显著(P<0.001);氮磷交互作用对豆科和莎草类生物量影响显著(P<0.05)。群落水平上,氮添加显著提高了植物全氮含量,对植物氮磷比(N∶P)有正效应,磷添加显著提高了植物全磷含量,对植物N∶P有负效应,植物全磷对N∶P的负效应大于全氮对N∶P的正效应。本研究表明氮、磷添加可能会使高寒草甸植物群落组成和植物养分含量发生改变,植物群落逐渐向禾草类发展;此外,高寒草甸植物生长趋向于受氮磷共同限制。     

Simulation Study of the Impact of Permanent Groundcover on Soil and Water Changes in Jujube Orchards on Sloping Ground

Land degradation is recognized as a major environmental problem in rainfed fruit orchards on the Chinese Loess Plateau. Six treatments were used to investigate surface runoff and soil moisture by means of simulated rainfall experiments: (i) a control (clean cultivation) (CC); (ii) strip cock's foot (Dactylis glomerata L.) cover (SCF); (iii) strip crown vetch (Coronilla varia L.) cover (SCV); (iv) strip bird's foot trefoil (Lotus corniculatus L.) cover (SBF); (v) strip white clover (Trifolium repens L.) cover (SWC); and (vi) complete white clover cover (WCC). The time to runoff was significantly longer under WCC than under other treatments (p < 0·05). The total runoff volume and sediment yield were significantly greater under CC than under the vegetation cover treatments (p < 0·05). The mean infiltration rate under WCC and CC was the largest and lowest and differed significantly from that under other treatments (p < 0·05). The change of soil water storage was the largest under WCC and the least under CC. The soil moisture was significantly greater under SCF than under other treatments (p < 0·05). Treatment SCF seemed to be the best groundcover for rainfed sloping jujube orchards on the Chinese Loess Plateau. Copyright © 2014 John Wiley & Sons, Ltd.     

木材初期腐朽研究综述

木材容易受到各种微生物的侵袭,真菌腐朽是导致木材破坏最严重的一种方式,即使是在木材质量损失率很小的腐朽初期,真菌也可以迅速引起木材结构的破坏,导致木材强度的急剧降低.生物培养和显微镜观察被认为是目前唯一权威的用来检测和评估木材初期腐朽的方法,但这些方法很难对木材的初期腐朽进行快速、准确地评估.因此,寻找一种迅速、准确地检测和评估木材初期腐朽的方法倍受人们的关注.有关初期腐朽及其检测与评估的研究在国外已有大量报道,而在我国却极为少见.本文综述了近几十年国内外有关木材初期腐朽及其检测与评估的研究,旨在增强人们对木材初期腐朽危害的认识,并呼吁有关部门重视相关研究在我国的发展.     

棘托竹荪的生物学特征

棘托竹荪的生物学特征周崇莲（中国科学院沈阳应用生态研究所沈阳１１００１５）曾德容（湖南合同县政协会同４１８３００）关键词棘托竹荪，形态特征，生态习性，营养成份１９８５年对湖南会同县的竹荪进行野外调查时，采到一种不同于竹荪（Ｄｉｃｔｙｏｐｈｏｒａｉｎｄ...     

Comparative analyses on the litter in Korean pine Mongolian Scots pine and Dahurian Larch plantations

Comparative analyses were conducted on the nutrient element content and returning amount of main fractional compositions of litter in Korean pine (KP), Mongolian Scots pine (MSP) and Dahurian larch (DL) plantations in Laoshan Plantation Experiment Station of Maoershan Experiment Forest Farm of Northeast Forestry University. The results are as follows: (1) The nutrient element content and returning amount in litter varies among different fractional compositions and tree species, the total returning amount of all nutrient elements and the returning amount of K, Ca, Mg, N and P are DL > MSP > KP, the returning amount of Cu is DL > KP > MSP, the returning amount of Fe and Mn are MSP > DL > KP; (2) To KP and DL plantations, the main nutrient element returned is dead needles; dead branches, bark scales and dead cones account for a little proportion; whereas to MSP plantation, besides dead needles, dead branches and bark scales also play an important role in the return of nutrient elements; (3) A little deal of dead leaves can provided a great deal of returning amount of nutrient elements.     

梣天牛危害损失调查初报

梣天牛幼虫危害椴树主干,成虫危害椴树叶柄,在3年内使树体从上向下干枯死亡,材质腐化,平均枯死木蓄积占林木蓄积的18．12％。发生林分直接经济损失16 110元·hm-2,生态效益损失在96 660 -322 200元。