A model for the temperature and density dependent reemergence of the bark beetle Ips typographus

A model is presented that describes the reemergence of parent spruce bark beetles, Ips typographus, based on breeding density and temperature conditions. Laboratory data obtained at one constant temperature provide the distribution of reemergence time and different combinations of threshold temperatures and degreedays (°D) at mean reemergence. Of these combinations, 167.71 °D above 7.5 °C gave the best correspondence between model prediction and field data obtained from densely infested standing trees. The model was in good agreement with the reemergence pattern found for two groups of infested logs under different temperature conditions when adjusted for the lower breeding density. The applicability of the model in the study of bark beetle reproductive biology and in forest management is discussed. The method used to construct the model should be useful in developing other models for poikilothermic processes.

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Résumé Ce modèle décrit la réémergence d'adultes d'I. typographus L. (Coleoptera, Scolytidae) en fonction de la densité et de la température.Les résultats obtenus en laboratoire à des températures constantes fournissent la distribution des réémergences et pour les dates de réémergence moyenne les différentes combinaisons de température de seuil et de degré de jour (°D). De toutes ces combinaisons, 167.71 °D au-dessus de 7,5 °C fournit la meilleure concordance entre les prévisions du modèle et les observations dans la nature à partir d'arbres fortement attaqués.Le modèle a montré un bon accord avec la réémergence observée dans deux groupes de branches attaquées dans différentes conditions de la température quand il a été ajusté aux faibles densités d'élevage.La discussion examine les possibilités d'application du modèle à l'étude de la biologie de la reproduction d'I. typographus et à l'aménagement forestier.La méthode utilisée pour construire le modèle pourrait être employée pour en développer d'autres chez des poikilothermes.

     

On the pathogens of the spruce bark beetle Ips typographus (Coleoptera: Scolytinae) in the Western Carpathians

Pathogens of spruce bark beetle Ips typographus were compared at eleven sites in Slovakia (the Western Carpathians). Seven different pathogen species were recorded: protozoan species Chytridiopsis typographi, Gregarina typographi, Malamoeba scolyti, nematodes of the genus Neoparasitylenchus and one unidentified nematode species. Presence of the entomopathogenic fungus Beauveria bassiana was also observed as well as parasitization by hymenopteran parasitoids. High infection rate of G. typographi and the nematode Neoparasitylenchus was detected in almost all sites and lethal impact of M. scolyti by massive infections was observed. The beetles from seven sites were screened for endosymbiotic bacteria Wolbachia, however, with no positive result.     

子午岭次生油松林立木竞争格局研究

研究干旱区森林立木竞争及空间分布格局,旨在为揭示干旱区森林恢复演替过程中竞争动态和格局形成驱动机制提供科学依据。经全面调查之后,依据时空互代原理选择了4个处于不同演替阶段,面积为0.25 hm²的大样地进行研究。采用Hegyi邻体密度模型研究立木竞争强度指数。采用Kriging法与Hegyi法相结合研究立木竞争的空间格局。采用一元和二元O-ring函数模型分别研究了乔木空间分布格局和乔木种间空间相关性。结果表明：在上述4个群落中油松（Pinus tabuliformis）种群密度分别为1 476、996、800、648株·hm^-2,白桦（Betula platyphylla）种群密度为48、32、44、16株·hm^-2,山杨（Populus davidiana）种群密度分别为64、28、24、12 株·hm^-2。3种主要乔木的竞争指数由高到低依次为油松、白桦、山杨,各物种竞争指数均随演替阶段的增长而下降;演替后期,胸径2~15 cm油松个体减少明显,而胸径大于30 cm的个体数量有所增加;在所有演替阶段中,油松竞争指数均随着胸径的增加而下降;油松种群竞争空间格局为典型的非匀质斑块状格局。点格局分析结果表明,油松种群在0~5 m尺度呈现聚集分布,且与其他树种在5~15 m尺度存在空间负相关。本研究主要结论如下,黄土高原次生油松林群落中油松竞争指数高于其他物种。油松在各演替阶段均呈现出基于径级大小的竞争不对称性,演替后期油松群落自疏机制为限制小径级个体的生长。竞争的格局在水平空间尺度具有斑块性,随着演替的进行,高竞争斑块在数量、范围和强度上减小,但并不会消失。油松生态策略为小尺度聚集分布,与其他树种在5~15 m尺度空间负相关,这个尺度已经超过了经典的树冠竞争理论范畴,其背后的原因需要更加深入地研究。     

Prior encounters modulate subsequent choices in host acceptance behavior by the bark beetle Ips pini

Laboratory bioassays indicate that the bark beetle Ips pini employs flexible, rather than absolute, responses to phytochemicals in its host acceptance behavior. Each beetle's decision to enter substrate was influenced by the types and concentrations of monoterpenes present. However, previous rejection of a simulated host containing a moderate concentration of monoterpenes increased the likelihood that the same concentration would be accepted upon a second or third encounter. This flexibility more than offsets any loss of vigor due to starvation and age that accompanies a process of trial and error. Starvation decreased beetles' total lipid content, but beetles can recover some energetic losses by a small amount of feeding during each trial. In addition to its adaptive value, a flexible host acceptance strategy may yield population level consequences. That is, bark beetles preferentially enter trees having low concentrations of monoterpenes, but may modify their acceptance thresholds when cues associated with stressed trees are not available. This could partially explain how some tree-killing bark beetles colonize a broader physiological range of trees during outbreaks. The adaptive value of relating individual decisions to population density may arise from two ecological relationships: first, as populations rise, the pool of stressed trees is rapidly depleted; secondly, healthy trees are attainable through pheromone – mediated mass attacks when adequate numbers of beetles are present. Flexible host acceptance behaviors may also reduce the advantage of relying exclusively on pre-landing cues to distinguish between susceptible and non-susceptible trees.     

Interactions within and between species at different densities of the bark beetleIps typographus and its predatorThanasimus formicarius

Interactions between the bark beetleIps typographus and one of its predators,Thanasimus formicarius, were investigated in caged spruce logs containing both species in eight different density combinations. Productively (offspring per female) ofIps was adversely affected by highIps gallery density as well as highThanasimus density.Thanasimus productivity was enhanced by highIps gallery density but negatively affected by highThanasimus density.Ips productivity andThanasimus developmental rate differed between tree individuals, probably owing to tree-related differences in phloem thickness. Relative predator-causedIps mortality was ca 20% higher at high gallery density (ca 300 egg galeries per m²) than at low gallery density (ca 100 egg galleries per m²), indicating that mortality was density dependent. This difference was due to the fact thatThanasimus larval density was positively related toIps gallery density. Mortality increased by ca 0.4% with each additionalThanasimus larva per m², independently of gallery density. Relative population levels ofIps andThanasimus were monitored with pheromone traps in two regions differing in theirIps typographus outbreak history. Absolute catch as well as theThanasimus/Ips catch ratio were ten times greater in the outbreak region than in the non-outbreak region. Coupled with the results in the caging experiment, this indicates thatT. formicarius responds numerically to changes inI. typographus numbers per unit bark area as well as toIps population changes at the regional level. The findings suggest that predation under bark may be a significant factor in supressingI. typographus outbreaks.     

Evaluating the Efficacy of Entomopathogenic Fungi against the Bark Beetle,Ips stebbingi Strohmeyer (Coleoptera,Curculionidae: Scolytinae) in India

The bark beetle, Ips stebbingi Strohmeyer (Coleoptera: Curculionidae: Scolytinae) is one of the most serious pests of Pinus wallichiana A. B. Jacks (Pinaceae) in Kashmir Himalaya. In order to find an effective biocontrol agent against this pest, we determined the effectiveness of entomopathogenic fungi, viz. Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae sensu lato (Metchnikoff) Sorokin, and Lecanicillium lecanii (Zimmerman) Zare et Gams against I. stebbingi in the laboratory conditions. Each fungal suspension contained 1.0 × 10⁹ spores of fungi in 1 ml. The insecticide (cyclone 505 EC) was also used as positive control in the experiment. The mortality caused with these fungi was recorded in treated branches and Petri dish assay. In treated branches, B. bassiana and M. anisopliae caused higher mortality, i.e., 68% and 71.25%, respectively, 10 days after treatment, and 93.10% and 88%, respectively, 20 days after treatment. The results of Petri dish assay revealed that I. stebbingi adults were highly susceptible to both treated fungal species and insecticide. However, B. bassiana and M. anisopliae caused higher percentage mortality six days after treatment, i.e., 94.16% and 100% respectively. The percentage of mortality caused by treating with insecticide was 60%. Lecanicillium lecanii was found significantly less virulent (mortality 18.33%) in all fungal treatments. Results obtained in the present study are promising and may be used as alternative means of chemical control for management of this beetle pest; however, no recommendations concerning the potential use of these fungal pathogens for forest protection can be given, and further studies are needed in this respect, especially under field conditions.

     

Nitrogen Uptake by Trees and Mycorrhizal Fungi in a Successional Northern Temperate Forest: Insights from Multiple Isotopic Methods

Forest succession may cause changes in nitrogen (N) availability, vegetation and fungal community composition that affect N uptake by trees and their mycorrhizal symbionts. Understanding how these changes affect the functioning of the mycorrhizal symbiosis is of interest to ecosystem ecology because of the fundamental roles mycorrhizae play in providing nutrition to trees and structuring forest ecosystems. We investigated changes in tree and mycorrhizal fungal community composition, the availability and uptake of N by trees and mycorrhizal fungi in a forest undergoing a successional transition (age-related loss of early successional tree taxa). In this system, 82–96% of mycorrhizal hyphae were ectomycorrhizal (EM). As biomass production of arbuscular mycorrhizal (AM) trees increased, AM hyphae comprised a significantly greater proportion of total fungal hyphae, and the EM contribution to the N requirement of EM-associated tree taxa declined from greater than 75% to less than 60%. Increasing N availability was associated with lower EM hyphal foraging and ¹⁵N tracer uptake, yet the EM-associated later-successional species Quercus rubra was nonetheless a stronger competitor for ¹⁵N than AM-associated Acer rubrum, likely due to the more extensive nature of the persistent EM hyphal network. These results indicate that successional increases in N availability and co-dominance by AM-associated trees have increased the importance of AM fungi in the mycorrhizal community, while down-regulating EM N acquisition and transfer processes. This work advances understanding of linkages between tree and fungal community composition, and indicates that successional changes in N availability may affect competition between tree taxa with divergent resource acquisition strategies.     

不同林龄尾巨桉人工林凋落物和土壤C、N、P化学计量特征

为正确认识桉树(Eucalyptus spp.)人工林凋落物和土壤C、N、P时空分配格局及两者间的关系,对5个林龄尾巨桉林分凋落物及土壤C、N、P含量及化学计量比进行测定分析。结果表明,凋落物的C含量均显著大于土壤,且不同林龄间凋落物C含量无显著差异,1年生人工林土壤表层(0~20 cm)的C含量显著小于3~7年生,其他土层C含量在不同林龄间差异不显著。凋落物的N含量均显著高于土壤,且1年生人工林显著大于其他林龄的,而土壤表层的N含量以7年生人工林最大,1年生的最小。凋落物的P含量除1年生人工林显著大于3年生外,其他林龄间均无显著差异,土壤的P含量在不同林龄间的差异均不显著。凋落物C∶N随林龄呈逐渐增大趋势,且显著大于土壤层。凋落物的C∶P和N∶P在不同林龄间的差异不显著,但均显著大于土壤层。凋落物的N含量与表层土壤的C、N含量呈极显著负相关,凋落物的C∶N与表层土壤的C∶P,N∶P呈显著正相关,表层土壤C、N积累受到凋落物N的制约。因此,在桉树人工林经营管理过程中如何降低凋落物分解的N限制性、提高养分传递效率及合理施肥显得十分重要。     

气候变化下西南地区主要亚热带常绿栎属乔木地理分布研究

为了解中国西南地区6种亚热带常绿栎属植物在未来气候情景下的潜在分布,该文利用最大熵模型(maximum entropy model, MaxEnt)和地理信息系统技术,结合帽斗栎(Quercus guyavaefolia)、川滇高山栎(Q. aquifolioides)、毛脉高山栎(Q. rehderiana)、高山栎(Q. semecarpifolia)、灰背栎(Q. senescens)和匙叶栎(Q. dolicholepis)的分布数据、生理生态特性、环境数据及未来2070s (2061—2080年)气候情景数据(SSPs126、SSPs245、SSPs585),分析了未来气候变化对各乔木种潜在地理分布的影响。结果表明,6种乔木MaxEnt模型的AUC均值均大于0.9,模拟效果好。温度季节性、年降水量、海拔、最冷月最低温和坡度等5个环境因子为6种栎属乔木分布的主导环境因子,即多适宜分布在温度季节性变化较小、温暖潮湿的山区。其中,川滇高山栎、毛脉高山栎和高山栎较其他3树种更适宜生长于温度偏低、温度季节性变化略大的中、高山地区。西南地区6种主要亚热带常绿栎属乔木潜在适宜区主要分布在西南地区,华中地区西部、华南地区西部和西北地区南部部分地区也有分布,高适宜区主要位于四川南部和云南西北部。在未来气候情景下,西南地区亚热带常绿主要栎属乔木适宜区面积以增长趋势为主,且向西北方向迁移。     

Mechanisms in the Shift of a Riparian Ground Beetle (Carabidae) Between Reproduction and Hibernation Habitat

Factors affecting the light response of the riparian species Bembidion petrosum (Coleoptera: Carabidae) were studied with various experimental designs in laboratory and in field. B. petrosum, which lives in open gravely/stony sites, oriented towards directed light at higher temperatures (above 15.0°C). This positive phototaxis was replaced by an orientation towards a dark silhouette (screen) at low temperatures. The orientation towards silhouettes is mainly a simple type of form vision, although a fraction of the individuals seems to exhibit a negative phototaxis. In experiments with a dark zone and a zone with directed light, individuals of B. petrosum mainly selected the dark zone. However, if two stones were placed in the light part of the arena, individuals tended to hide under them. This applied independent of light intensity and whether a tuft of grass was present or absent in the dark part of the arena. The experiments indicate that the shift of the species between the reproduction (spring/summer) and hibernation (autumn/winter) habitat involves a change from an orientation towards silhouettes at low temperatures in autumn to an orientation towards directed light at higher temperatures in spring. This is combined with a specialized low thigmokinesis (preference of heavy and rough objects) and lower moisture requirements of the species in autumn/winter than in spring/summer.     

Infection of Blissus antillus (Hemiptera: Lygaeidae) Eggs by the Entomopathogenic Fungi Metarhizium anisopliae and Beauveria bassiana

This study determined the pathogenicity and virulence of Beauveria bassiana and Metarhizium anisopliae to eggs of the chinch bug Blissus antillus (Hemiptera: Lygaeidae). Eggs were inoculated under laboratory conditions by immersion in concentrations of 1 × 10⁴ and 5 × 10⁶ conidia/ml. Inoculated eggs were kept under controlled conditions. Evaluations were carried out daily for 20 days. M. anisopliae isolates were highly virulent to eggs, even at 1 × 10⁴ conidia/ml. All B. bassiana isolates tested were considered to be of low virulence or avirulent. The most virulent isolate tested was ESALQ 818 (M. anisopliae), which caused 96.7% infection, when eggs were immersed in suspensions of 1 × 10⁴ conidia/ml. Conidial production on infected eggs was observed to be highest for M. anisopliae isolate CG144, with a mean value of 11.6 × 10⁵ conidia/ml/egg. Infection of Blissus eggs oviposited on plant stems was greater when M. anisopliae isolate CG144 was formulated in mineral oil (63.5% mortality) than when formulated in Tween 80 (27.1% mortality).     

两种芒箕覆盖度下毛竹林土壤团聚体的稳定性及生态化学计量特征比较研究

为了解毛竹林下不同盖度芒萁种群对土壤碳含量和养分状况的影响,研究了四川长宁县芒萁(Dicranopteris dichoyoma)盖度分别为7.75%(PE)和63.25%(DD)下的毛竹(Phyllostachys edulis)林土壤团聚体稳定性和生态化学计量特征。结果表明,DD样方土壤大团聚体含量显著低于PE样方,进而导致团聚体稳定性降低。DD样方土壤总有机碳(TOC)、全氮(TN)、全磷(TP)含量显著低于PE样方,且TP降幅最大,使得土壤C:N、C:P和N:P显著增加。毛竹凋落叶和细根的TOC、TN、TP、C:N、C:P和N:P在DD和PE样方间无显著差异,但DD样方芒萁凋落叶和细根的TN和TP含量显著高于毛竹。相关分析表明PE毛竹细根的TP含量仅与大团聚体的TP含量呈显著正相关;DD毛竹和芒萁细根的TP含量与大团聚体、微团聚体和中团聚体的TP含量均呈显著正相关。毛竹林下高盖度的芒萁种群降低了土壤团聚体稳定性和土壤C、N、P含量,通过改变土壤生态化学计量特征进而增加毛竹和芒萁细根对土壤不同粒径团聚体N和P的吸收,尤其是对P的吸收。因此,在川南地区粗放经营毛竹林中应考虑调整林下...     

香樟凋落叶分解对辣椒及土壤氮营养的限制作用

香樟(Cinnamomum camphora)凋落叶分解能够明显干扰受体植物的生长、生殖、光合生理和活性氧代谢。该研究继续采用盆栽试验,探讨了不同量[0(对照)、25、50和100g]的香樟凋落叶添加到土壤(10kg/盆)中对受体植物辣椒(Capsicum annuum)及其土壤氮营养状况的影响,外源氮(尿素)输入对凋落叶分解的交互作用,以及凋落叶分解效应的产生是否因为其较高的C/N比而导致微生物争氮。结果显示:(1)各剂量(25~100g/盆)凋落叶处理下,辣椒幼苗硝态氮、可溶性蛋白和全氮含量均在至少2个月内大幅显著降低。(2)土壤硝态氮与辣椒硝态氮、全氮间均具有极显著的协同下降趋势;土壤微生物生物量氮则在总体上高于对照,而土壤全氮和铵态氮的响应较小。(3)施氮不仅使辣椒各氮组分和土壤硝态氮含量整体提升,还使凋落叶分解在这些指标上的抑制作用显著减弱。(4)香樟凋落叶的初始C/N为125.61±4.89,其在土壤中分解48~137d后的C/N始终远高于Hodge假说指出的可导致微生物争氮的临界值,但经过分解120d和135d的凋落叶添加到土壤中并不抑制辣椒的生长。研究认为,香樟凋落叶分解初期可能释放了不利于土壤硝化过程的物质,造成土壤硝态氮匮乏,以致受体植物的氮素吸收和积累减少,而凋落叶较高的C/N比及土壤微生物争氮并非主导因素。     

桉树根系共生真菌的分离与鉴定

南方土壤缺磷现象较为严重,菌根真菌等共生真菌对植物吸收磷等养分具有重要的促进作用。该研究采集尾叶桉(Eucalyptus urophylla)、窿缘桉(Eucalyptus exserta)和尾巨桉(E.urophylla×E.grandis)3种华南地区主要造林树种根系,采用组织分离法进行真菌分离,通过形态特征和核糖体18SrDNA基因ITS序列分析进行鉴定,经柯赫氏法则(Kochs Rule)确定桉树根系共生真菌,为桉树共生真菌理论研究和资源利用提供依据。结果表明:(1)3种桉树根系中,窿缘桉具有外生菌根(ectomycorrhizas,ECM)和丛枝菌根(arbuscular mycorrhizas,AM)结构,尾叶桉和尾巨桉同时具有AM结构、ECM结构和深色有隔内生真菌(dark septate endophytes fungi,DSE)结构。(2)3种桉树根系中分离鉴定出6种真菌:三色小皮伞菌(Marasmius tricolor)、黑柄裸脚伞(Gymnopus melanopus)、茎点霉属(Phomasp.)、镰刀霉属(Fusariumsp.)、二型伞霉(Umbelopsis dimorpha)和芒弗里亚拟盘多毛孢(Pestalotiopsis mangifolia)。(3)6种真菌回接巨桉(Eucalyptus grandis)组培苗,三色小皮伞菌和黑柄裸脚伞形成ECM结构,为ECM真菌;茎点霉属、镰刀霉属、二型伞霉和芒弗里亚拟盘多毛孢形成DSE典型的深色有隔菌丝和微菌核结构,推测为DSE;其中2种ECM真菌为桉树中首次报道。     

AM真菌对留兰香和常夏石竹耐盐性的影响

为探究接种丛枝菌根(arbuscular mycorrhiza,AM)真菌对不同盐胁迫水平下留兰香和常夏石竹侵染特性与生理指标的影响,该研究采用盆栽试验的方法,将留兰香和常夏石竹分为接种处理与对照处理,并施加不同浓度(0、50、100、150、200 mmol/L)的NaCl胁迫,胁迫结束后测定两种植物的侵染特性与生理...     

天竺桂凋落叶对凤仙花生长和光合特性的影响

采用盆栽实验,通过向土壤(每盆8kg)中添加0g·pot-1(CK)、20g·pot-1(L)、40g·pot-1(M)和80g·pot-1(H)天竺桂(Cinnamomum japonicum)凋落叶,模拟其自然分解对凤仙花(Impatiens balsamina)生长和光合特性的影响。结果显示:(1)添加天竺桂凋落叶M和H处理下,凤仙花生物量和地径均显著降低,而株高无明显变化;其叶绿素含量受到显著抑制,净光合速率(Pn)和水分利用效率(WUE)显著低于CK,而气孔导度(Gs)、胞间二氧化碳浓度(Ci)和蒸腾速率(Tr)3个气体交换参数显著高于CK。(2)Pn-PAR曲线和Pn-Ci曲线拟合表明,凤仙花在光饱和以及CO2饱和状态下的最大净光合速率(Pn max)、表观量子效率(AQY)、暗呼吸速率(Rd)、RuBP羧化效率(CE)和光呼吸速率(Rp)均随添加天竺桂凋落叶处理量的增加而呈下降趋势。(3)添加天竺桂凋落叶36d和67d时对凤仙花生长影响不明显,而处理58d时有明显抑制作用。研究表明,在模拟天竺桂凋落叶自然分解的土壤环境中,凤仙花的光合色素含量降低,抑制了其光合能力,对环境适应能力降低,导致凤仙花的生长受到抑制。     

Potential Physiological Activities of Fungi and Bacteria in Relation to Plant Litter Decomposition along a Gap Size Gradient in a Natural Subtropical Forest

Abstract The dynamics of fungal and bacterial potential physiological activities during leaf, branch, and bark litter decomposition along a gap size gradient in a subtropical forest was determined using substrate-induced respiration (SIR) with antibiotics selective for fungi and bacteria, respectively. A gap size gradient (1) was under closed canopy; (2) had small gaps with a diameter (≤5m); (3) had small to intermediate gaps (5–15 m diameter); (4) had intermediate to large gaps (15–30 m diameter); and (5) had large gaps (≥30 m diameter). Litter decomposition was studied using a litter bag technique. Fungi had higher SIR than bacteria for each type of litter in any size class of gaps. Gaps 1, 2, and 3 had higher fungal and bacterial SIRs than gaps 4 and 5. Moreover, decomposing leaf litter exhibited higher fungal and bacterial SIRs than branch, and branch higher than bark. Simple correlation analysis indicated that fungal SIR was a reliable index of decomposition rates. Fungal SIR was significantly and positively correlated with soil moisture, whereas bacterial SIR was not significantly correlated with soil moisture. The relationships among microclimatic factors, fungal and bacterial physiological activities, and rates of plant litter decomposition suggest that, in subtropical ecosystems, fungal community activities were strongly and directly regulated by the environmental heterogeneity within gaps, and an important regulator of rates of plant litter decomposition rates. Received: 13 January 1997; Accepted 28 March 1997