Predicting future community composition from random soil seed bank sampling – evidence from a drained lake bottom

Questions: What is the accuracy and reliability of the commonly used random soil sampling methodology for predicting seedling density, species richness and composition of the emerging seedling community? Location: Lake Kraenepoel, western Belgium. Methods: We compared density, species composition and observed and rarefactioned species richness of the seedling community emerging on a soft water lake bed exposed after drainage with the seedling community germinating in the laboratory from random soil samples in the same plots. Results: Seedling density did not differ between the two methods and there was a significant correlation between seedling density on the exposed lake bed and in the soil samples. This indicates that future seedling density can be reliably predicted based on soil sampling, in particular for the most abundant species. The most frequently occurring and abundant species among the seedlings in the soil samples were also the most frequent and abundant species germinating on the exposed lake bed. In contrast, species richness was much higher on the exposed lake bed than in the soil samples, and this difference was still significant for annual species after correction for differences in sampling intensity by rarefaction. We found no correlation between the number of species retrieved by the two methods. Although seedlings of rare and target species emerged on the lake bed, random soil sampling clearly failed to detect seeds of most of these species. Conclusions: Random soil sampling at a commonly used intensity and using the standard germination conditions can accurately predict future total seedling density and the density of the most abundant species. However, the method is not reliable for predicting the probability of establishment of populations of uncommon species. When executing a seed bank study, sampling intensity and germination conditions need to be adapted to the nature and the level of detail of the research question to be answered.     

Effects of planting method on the recovery of arboreal ant activity on revegetated farmland

Ecological restoration aims to re‐establish both biodiversity and ecological function in damaged ecosystems. Ants are important drivers of ecological functions and are early colonizers of restored ecosystems. Rates at which ants perform functions are thought to be fuelled by access to plant sugars. In revegetated farmland in south‐eastern Australia, I tested if ant activity on trees, which reflects use of arboreal sugars, follows a predictable trajectory of recovery towards a remnant‐like state. Additionally, I examined whether planting method alters this trajectory by comparing tube stock (TS), which results in low Eucalyptus densities, with direct seeding (DS), which results in high Eucalyptus densities. Replicate sites (n = 5) of young (planted between 1998 and 2001) and old (planted between 1989 and 1994) TS and DS revegetation, pastures and remnants were compared. Activity on trunks was significantly positively correlated with ant tending of Hemiptera in young and old revegetation. In DS plantings, activity and estimated liquid loads on Eucalyptus trees were low and rapidly approached that in remnants, while TS sites remained similar to high values observed in pastures with trees. Patterns for Acacia were less clear, reflecting consistent densities for this species between TS and DS. At the whole‐of‐field scale, planting methods did not differ. Importantly, although trajectories differed, neither TS nor DS sites approached the low activity or estimated liquid loads observed in remnants. Rates of ant use of arboreal sugars and associated sugar‐fuelled processes may thus take considerably longer to recover than the period covered by this study. This finding suggests planting method may affect the trajectory and outcome of revegetation for plant health, as well as sugar‐fuelled ecosystem functions performed by ants.     

Farm-scale trials to compare the entomopathogenic fungus Beauveria bassiana with pirimiphos methyl + deltamethrin and essential oil of lemon grass for protection of stored cowpea against Callosobruchus maculatus (Coleoptera: Bruchidae)

In trials conducted in Benin, conidia of Beauveria bassiana were evaluated as a control method against the cowpea weevil, Callosobruchus maculatus , in stored cowpea. In the first trial using a high artificial infestation of C.   maculatus in 8-kg batches of cowpea in jerry cans under typical conditions, concentrations of 1 × 10⁹ and 1 × 10¹¹ conidia kg⁻¹ were compared with lemon grass oil at 2 mL kg⁻¹ and the synthetic pesticide mixture of 1.5% pirimiphos methyl + 0.05% deltamethrin at 0.5 g kg⁻¹. After 2 months of storage, seed losses (SD) were 20.63 (5.3)% in the untreated control, 8.04 (3.2)% in the low-dose B.   bassiana group, 3.12 (1.3)% in the high-dose B.   bassiana group, 2.52 (0.4)% in the lemon grass oil group and 0% in the pirimiphos methyl + deltamethrin group. In a second trial with natural infestations in 50-kg batches of cowpea in 200-L drums, treatment with B.   bassiana 1 × 10¹¹ conidia kg⁻¹ was compared with pirimiphos methyl + deltamethrin at 0.5 g kg⁻¹. After 6 months of storage on six farms, losses reached 30.76 (1.5)% in the control, 1.28 (0.2)% in the pirimiphos methyl + deltamethrin group and 3.69 (0.6)% in the B.   bassiana group.     

Selective light transmittance of translucent bracts in the Himalayan giant glasshouse plant Rheum nobile Hook. f. & Thomson (Polygonaceae)

Translucent bract transmittance of ultraviolet (UV) to infrared (IR) radiation (between 320 and 800 nm) and leaf anatomy were examined in a glasshouse plant, Rheum nobile Hook. f. & Thomson (Polygonaceae) to assess the function of avoiding injury by UV radiation while keeping the inflorescence warm by photosynthetically active (PA) and IR radiation. Although the translucent bracts and rosulate leaves transmitted little UV radiation, the former always transmit more PA and IR radiation. Additionally, the bracts transmit much more scattered solar radiation than direct radiation. The bracts are also anatomically different from the rosulate leaves. They have two or three layers of mesophyll cells with neither palisade nor spongy parenchymatous cells; in addition, the uppermost layer of mesophyll and the epidermis stain easily, and both are thought to play a role in attenuating UV radiation. The leaf epidermis of many land plants has UV absorbing pigments such as flavonoids, which absorb almost all UV radiation. Thus the role of the bracts of R. nobile is to protect the reproductive organs by absorbing UV radiation and to keep them warm by transmitting PA and IR radiation. The bracts are believed to have adapted function and form to the environment, in particular, to the weather conditions of the eastern Himalaya.     

入侵植物的繁殖策略以及对本土植物繁殖的影响

理解入侵生物的繁殖策略是阐明生物入侵机制的一个重要方面。入侵植物常表现出一些共同的繁殖特征, 如以两性花为主的性系统、自动自交为主的繁育系统或不依赖传粉媒介的无融合生殖和无性繁殖以及高生殖投资的资源配置策略等。成功入侵的外来植物通过影响本土的传粉者, 在种群和群落水平上影响本土植物的有性繁殖, 甚至促使某些本土植物在繁殖对策和表型性状上发生快速转变。目前, 入侵植物繁殖策略及其生态效应的研究多侧重于入侵种的快速演化, 而有关外来植物与本土植物间的相互影响及其可能存在的协同适应研究还较为缺乏。探讨本土植物在外来种入侵压力下的繁殖对策和响应机制, 将丰富人们对物种间竞争、共存及群落构建等机制的深入了解。从繁殖和适应的角度探求入侵植物与本土植物之间的复杂关系, 将有助于解析生物入侵的机制及人类干扰下的物种演化规律, 也为预测和防控入侵植物提供科学依据。     

Antinociceptive activity of the volatile oils of Hyptis pectinata L. Poit. (Lamiaceae) genotypes

Hyptis pectinata L. Poit (Lamiaceae) is known popularly in Brazil as “sambacaita” or “canudinho” and is used in the treatment of inflammations, bacterial infections and ache. The antinociceptive activity of the volatile oils of six genotypes, at doses of 100, 200 and 400 mg/kg body wt., were investigated using abdominal writhe models induced by acetic acid and hot plate tests. The volatile oils of all the genotypes are composed mainly of sesquiterpenoids. All the genotypes showed antinociceptive effects in both models used; the SAM002 genotype showed the major inhibitory effect at dose of 100 mg/kg body wt. These results suggest that the volatile oil of H. pectinata has peripheral (writhe reduction) and central (time delay of thermal reaction) effects. These observations indicate that H. pectinata may be useful as an analgesic drug.     

Phyto-extraction of heavy metals and biochemical changes with Brassica nigra L. grown in rayon grade paper mill effluent irrigated soil

In this study, distribution of metal accumulation and their biological changes of Indian mustard plants (Brassica nigra L.) grown in soil irrigated with different concentration of rayon grade paper effluent (RGPE, 25%, 50%, 75%, 100%, v/v) were studied. A pronounced effect was recorded at 50% (v/v) RGPE on germination of seeds, amylase activity and other growth parameters in Indian mustard plants. An increase in the chlorophyll and protein contents was also recorded at <50% (v/v) RGPE followed by a decrease at higher concentrations of RGPE (>75%). A significant increase lipid peroxidation was recorded, which was evidenced by the increased malondialdehyde (MDA) content in shoot, leaves and seeds in tested plant at all the concentrations of RGPE. This Indian mustard plants (Brassica nigra L.) are well adapted for tolerance of significant amount of heavy metals due to increased level of antioxidants (cysteine and ascorbic acid) in root shoot and leaves of treated plants at all concentration of RGPE. Moreover, it is also important that RGPE should be treated to bring down the metal concentration well within the prescribed limit prior to use in agricultural soil for ferti-irrigation.     

北京城区花粉致敏植物种类、分布及物候特征

为了解北京城区花粉致敏植物的种类、分布格局和物候特征,结合文献调研及专家访问,对北京5环以内的花粉致敏植物进行了调查.结果表明:1)北京城区五环内共有致敏花粉植物19科32属99种,其中北京本地种52种,占总数的52.5%,国内其他地区引进种和国外引进种各占总数的26.3%和21.2%;2)北京城区32属花粉致敏植物以北温带成分为主,占40.6%,其次是世界性分布与泛热带分布;3)公园内的花粉致敏植物种数最多,行道树种中花粉致敏植物的比例最高.北京城区各功能区中花粉强致敏草本的盖度,从大到小的顺序是城市废弃地>体育中心及机关单位>道路绿地>公园>居民区>学校>广场;4)北京城区木本花粉致敏植物的花期主要集中在3—4月,草本在7—9月.     

Photosynthesis of Cockspur [Echinochloa crus-galli (L.) Beauv.] at Sites of Naturally Elevated CO2 Concentration

High abundance of cockspur (Echinochloa crus-galli) at the geothermal carbon dioxide spring area in Staveinci indicates that this species is able to grow under widely varying CO₂ concentrations. Living cockspur plants can even be found very close to gas-releasing vents where growth is significantly reduced. Plant height correlated well with CO₂ exposure. The ¹³C value of the CO₂ spring air was –3.9 and ¹³C values of high-, medium-, and low-CO₂ plants were –10.14, –10.44, and –11.95 , respectively. Stomatal response directly followed the prevailing CO₂ concentrations, with the highest reduction of stomatal conductance in high CO₂ concentration grown plants. Analysis of the curves relating net photosynthetic rate to intercellular CO₂ concentration (P _N-C_i curves) revealed higher CO₂ compensation concentration in plants growing at higher CO₂ concentration. This indicates adjustment of respiration and photosynthetic carbon assimilation according to the prevailing CO₂ concentrations during germination and growth. There was no difference in other photosynthetic parameters measured.