Factors determining species richness of soil seed banks in lowland ancient woodlands

The demise of coppicing in UK ancient woodlands, combined with the planting of non-native, fast-growing conifers in the twentieth century, heightens the potential recharge value of ground flora seed banks. Soil cores from adjoining semi-natural and conifer-containing stands in four lowland ancient woods in central England were removed to establish seed bank species richness. During a fourteen-month germination trial soil from two depths yielded 6554 seedlings from 81 species, ten of which showed a strong affinity for ancient woodland conditions. Juncus effusus accounted for 80% of emergent seeds whilst 23 other species, including Lysimachia nummularia and Potentilla sterilis, were represented by only one individual. Species richness is described by a model that explains 40% of observed variance (P < 0.00001). The model has three significant variables: species richness increases as soil pH rises, and decreases with both depth and increasing time since the most recent planting/disturbance event. No difference was found in the density of seeds from species common to paired semi-natural and conifer-containing stands that were separated only by a woodland ride, suggesting prior management and environmental conditions have a greater influence on seed banks than current stand type. Sørensen similarity index values revealed poor congruence between above-ground vegetation and species in the seed bank. Taking pH measurements in conifer stands identified as younger in terms of planting/disturbance may help locate areas where greater numbers of species (including woodland specialists) are located. Caution is required, however, as these seed banks may also contain non-target, competitive species that may swamp the regeneration of woodland specialists.     

Seed Treatment with Trichoderma Species for Control of Damping-off of Cowpea Caused by Macrophomina phaseolina

Cowpea seeds treated with three Trichoderma spp. at four inoculum doses, and at four exposure times in three different formulations were planted in soils amended with Macrophomina phaseolin a, and assessed for stand establishment and post-emergence damping off. The highest percentage plant stands at 21 days after planting were 66% for T. koningii and T. harzianum , and 51% for Trichoderma sp., at 6.8 ×10 7 , 2.0 ×10 10 , and 1.0 ×10 7 colony forming units (CFUs) ml -1 , respectively. Across sampling dates and irrespective of time of exposure to the formulations, the T. harzianum and T. koningii formulations resulted in significantly greater percentage plant stands than the seeds treated with a Trichoderma sp. and the controls. Seed treatment formulations with Trichoderma spp. were derived from propagule suspensions at the most effective inoculum dose in Tween 80, in suspension with cooked cassava starch as an adhesive, or in a slurry with uncooked cassava starch. At 21 days, the suspensions with Tween 80 and cooked starch resulted in significantly higher percentage plant stands than the control, while stands from seeds treated in a slurry formulation and starch solutions were not different. Seed exposure to the different formulations for 10, 20, 30, or 40 min, provided mixed results. Seeds treated with benomyl at 0.5 g a.i/50 g resulted in 95 and 100% stands for the two sets of experiments, respectively.     

杨树刺槐混交林及纯林枯落叶分解

研究了杨树（Ｐｏｐｕｌｕｓｓｐｐ．）、刺槐（Ｒｏｂｉｎｉａｐｓｅｕｄｏａｃａｃｉａ）纯林及混交林枯落叶一年中的分解及养分动态变化规律．结果表明,杨树枯落叶分解速度较慢,刺槐较快,而混交林则较杨树有较大提高．在分解过程中,杨树枯落叶Ｎ、Ｐ释放困难,需经过长达１０个月的养分富积过程;刺槐枯落叶Ｎ、Ｐ元素释放较为容易;混交林枯落叶养分富积时间缩短、幅度下降,分解速度加快,说明杨树和刺槐混交有利于枯落叶分解和Ｎ、Ｐ循环．     

The role of seed-tuber and stem inoculum in the development of gangrene in potatoes

To determine the relative importance of seed tubers and stems as sources of inoculum for potato gangrene in progeny tubers, different levels of inoculum of Phoma exigua var. foveata were established in field experiments by planting rotting or contaminated seed tubers and by inoculating stems shortly before haulm desiccation. The pathogen was only occasionally detected by isolation from inside green stems in June and July on plants growing from contaminated but unrotted seed. The incidence of pycnidia on desiccated stems increased with increasing concentration of inoculum contaminating seed tubers and with increasing time interval between desiccation and harvest. Stem infection was probably derived from inoculum on seed tubers spreading via the soil to the stem bases. Stem inoculation of plants growing from uninoculated or uncontaminated seed greatly increased both the gangrene potential of progeny tubers (defined as % wounds with gangrene after uniformly damaging tubers and storing them at 5°C for 12 wk), and tuber contamination (defined as % wounds with gangrene after spreading tuber-borne soil onto test tuber slices and storing them at 5°C for 8 wk). However, when stems of plants growing from rotting or contaminated seed were cut at ground level and removed before desiccation, gangrene potential of progeny tubers was only slightly less than that of tubers from untreated plots. There was no evidence that soil inoculum or aerial spread played a significant role in disease development. Gangrene potential and contamination of progeny tubers were related to Contamination levels on seed tubers. Some transmission also occurred from rotted seed tubers to progeny. Inoculum levels around progeny tubers increased rapidly after desiccation even in plots where stems had previously been cut at soil level and removed to eliminate pycnidial development above ground as a source of inoculum. Both gangrene potential and contamination of progeny tubers were greater on cv. Ulster Sceptre than on cv. Pentland Crown. The results showed that the inoculum on seed tubers, whether from rots or surface contamination, contributed more to the contamination of progeny tubers at harvest than did the inoculum from pycnidia on stems following desiccation of the haulm.     

Estimating nitrogen budgets of Typha angustifolia by considering the regrowth shoot productivity and nitrogen content after harvesting aerial organs in different growing seasons

A dynamic model that includes regrowth after harvesting aerial shoots of an emergent macrophyte, Typha angustifolia L., was applied to evaluate the nitrogen (N) budget and the N uptake by the plant from sediment in Shibakawa Pond, Japan. Under natural conditions (control/uncut stands), the analysis showed that the annual uptake of N from sediment was 26.6 gN/m² and harvesting Typha shoots at their growth peak removed 29.0 gN/m² from the system (142 days in summer). Harvesting in winter after weathering of leaves removed only 13.9 gN/m². To evaluate the N budget considering regrowth shoot characteristics, three sets of harvesting experiments were done on 16 May, 8 July, and 5 August 2003. Our study revealed that May, July, and August harvesting removed 9.4, 21.9, and 16.3 gN/m², respectively. Further, combining the first harvesting from spring to summer and the second harvesting in autumn (before the start of senescence of regrowth shoots), the annual total N removals in stands cut in May and autumn and July and autumn were 34.7 and 36.0 gN/m², respectively—higher than that in stands cut in August and autumn (22.2 gN/m²) or that in uncut stands (13.9 gN/m²). At the same time, the amounts stored in rhizomes by stands cut in May and autumn, July and autumn, and August and autumn were 9.1, 8.4, and 4.4 gN/m², respectively, lower than that in uncut stands (18.8 gN/m²). Our results suggest that summer harvesting, especially in July to August, improves N removal efficiency and decreases the translocation of N from primary shoots to rhizomes, which is important for the sustainable management of Typha-dominated wetlands. Combined summer and autumn harvests further increase the removal efficiency but drastically reduce the storage of N. This might be useful when we need to control the plants properly.     

Black scurf and stem canker of potato (Corticium Solani Bourd. & Galz.)

Black scurf and stem canker of the potato was investigated in field trials on infected soil at Warburton, Cheshire, to study the effect of planting clean and contaminated seed, and the relation between the dates of planting and lifting and the contamination of the crop tubers.
Black scurf was prevalent on crops grown from clean seed but was more severe on crops raised from contaminated seed. Under conditions favourable for the disease the yields from clean and contaminated seed were satisfactory and were not significantly different. Young shoots of plants from contaminated seed were severely attacked and tuber formation was checked; these results were not obtained on clean seed plots.
More black scurf occurred on late-dug crops; on early-dug plots the disease, although almost absent in 1941, was prevalent in 1942. Late planting failed to reduce appreciably the amount of black scurf.
Variety trials included Arran Banner, Kerr's Pink (two vigorous varieties), King Edward and Majestic (two less vigorous varieties). All were heavily infected and each recovered well from an attack on the young shoots.
Inoculation of the seed at planting time did not affect the results; in all trials, misses and wilted shoots caused by Corticium were rare and there was no relation between the yield and the amount of black scurf on the crop tubers.
The results indicate that the disease causes little, if any, loss under farm conditions.     

鱼类卵子发育能力的进一步研究

作者中的二人[Tung,and Tung.(童第周与叶毓芬)1944;Tung,Chang,andTung.(童第周、张致一与叶毓芬)1945]曾以分割的方法,研究金鱼(Carassiusauratus)卵子的发育能力。他们将2至8细胞时期的金鱼卵子,在去膜后,用玻璃针,按第一次或第二次的分裂平面,将整个卵子分割为二半。每半含有半数分裂球,一半卵黄,和一半未流入分裂球的细胞质。分割后,每半都能继续发育,但产生下列6种不同的情形:(1)二半都发育为完整的,一半大小的胚胎;(2)一个为完整的胚胎,另一个为不完整的胚胎;(3)一个为完整的胚胎,另一人为囊胚;     

Fine-scale genetic structure of Nothofagus pumilio (lenga) at contrasting elevations of the altitudinal gradient

Montane forests provide the natural framework to test for various ecological settings at distinct elevations as they may affect population demography, which in turn will affect the spatial genetic structure (SGS). We analyzed the fine-scale SGS of Nothofagus pumilio, which dominates mountain areas of Patagonia, in three pairs of sites at contrasting elevations (low- vs. high-elevation). Within a total area of 1 ha fresh leaf tissue from 90 individuals was collected at each of the six studied stands following a spatially explicit sampling design. Population genetic diversity parameters were analyzed for all sampled individuals using five polymorphic isozyme loci, and a subset of 50 individuals per stand were also screened for five microsatellite loci. The SGS was assessed on 50 individuals/stand, using the combined datasets of isozymes and microsatellites. Most low-elevation stands consisted of older individuals with complex age structures and genetically diverse plots. In contrast, high-elevation stands and one post-fire low-elevation population yielded even-aged structures with evidence of growth suppression, and were genetically homogeneous. All stands yielded significant SGS. Similarly to mature stands of the non-sprouter congener Nothofagus dombeyi, multi-age low-altitude N. pumilio yielded significant SGS weakened by competing species of the understory and the formation of seedling banks. Alike the sprouter Nothofagus antarctica, high-altitude stands produced significant SGS as a consequence of occasional seedling establishment reinforced by vegetative spread.     

Spontaneous Return of Biodiversity in Restored Subtropical Thicket: Portulacaria afra as an Ecosystem Engineer

An accepted criterion for measuring the success of ecosystem restoration is the return of biodiversity relative to intact reference ecosystems. The emerging global carbon economy has made landscape‐scale restoration of severely degraded Portulacaria afra (spekboom)‐dominated subtropical thicket, by planting multiple rows of spekboom truncheons, a viable land‐use option. Although large amounts of carbon are sequestered when planting a monoculture of spekboom, it is unknown whether this is associated with the return of other thicket biodiversity components. We used available carbon stock data from degraded, restored, and intact stands at one site, and sampled carbon stocks at restored stands at another site in the same plant community. We also sampled plant community composition at both sites. The total carbon stock of the oldest (50 years) post‐restoration stand (250.8 ± 14 t C ha^?1) approximated that of intact stands (245 t C ha^?1) and we observed a general increase in carbon content with restoration age (71.4 ± 24 t C ha^?1 after 35 and 167.9 ± 20 t C ha^?1 after 50 years). A multiple correspondence analysis separated degraded stands from stands under restoration based on ground cover, floristic composition, and total carbon stock. Older post‐restoration and intact stands were clustered according to woody canopy recruit abundance. Our results suggest that spekboom is an ecosystem engineer that promotes spontaneous return of canopy species and other components of thicket biodiversity. The spekboom canopy creates a cooler micro‐climate and a dense litter layer, both likely to favor the recruitment of other canopy species.     

Simulation of leaf area development based on dry matter partitioning and specific leaf area for cut chrysanthemum

This work aims to predict time courses of leaf area index (LAI) based on dry matter partitioning into the leaves and on specific leaf area of newly formed leaf biomass (SLA(n)) for year-round cut chrysanthemum crops. In five glasshouse experiments, each consisting of several plant densities and planted throughout the year, periodic destructive measurements were conducted to develop empirical models for partitioning and for SLA(n). Dry matter partitioning into leaves, calculated as incremental leaf dry mass divided by incremental shoot dry mass between two destructive harvests, could be described accurately (R(2 )= 0.93) by a Gompertz function of relative time, R(t). R(t) is 0 at planting date, 1 at the start of short-days, and 2 at final harvest. SLA(n), calculated as the slope of a linear regression between periodic measurements of leaf dry mass (LDM) and LAI, showed a significant linear increase with the inverse of the daily incident photosynthetically active radiation (incident PAR, MJ m(-2 )d(-1)), averaged over the whole growing period, the average glasshouse temperature and plant density (R(2 )= 0.74). The models were validated by two independent experiments and with data from three commercial growers, each with four planting dates. Measured shoot dry mass increase, initial LAI and LDM, plant density, daily temperature and incident PAR were input into the model. Dynamics of LDM and LAI were predicted accurately by the model, although in the last part of the cultivation LAI was often overestimated. The slope of the linear regression of simulated against measured LDM varied between 0.95 and 1.09. For LAI this slope varied between 1.01 and 1.12. The models presented in this study are important for the development of a photosynthesis-driven crop growth model for cut chrysanthemum crops.     

Presence of Listeria and Salmonella spp. in retail chicken in Northern Ireland

AIMS: Retail packs of fresh chicken in Northern Ireland were sampled to determine the frequency with which they were contaminated with Salmonella and Listeria spp. METHODS: Packs of chicken were chosen from supermarkets ensuring a diverse range of EU producer codes were sampled. Salmonellas were isolated using BS EN 12824: 1998 methodology, biotyped and serotyped whilst Listeria spp. were isolated based on EN ISO 11290-1: 1996 procedures and identified using a multiplex PCR system utilizing genus and species specific primers. SIGNIFICANCE AND IMPACT OF THE STUDY: Only three of 205 samples yielded Salmonella spp. indicating that measures undertaken by the poultry industry to control this pathogen have apparently been successful. However, Listeria spp. were present in 38 of 80 samples tested (48%) and 14 (18%) yielded Listeria monocytogenes. Thus Salmonella controls do not markedly affect this pathogen and retail packs of raw chicken must be considered a potential source of L. monocytogenes, and appropriate precautions taken to prevent infection.     

The effect of leaf size on mutual shading and cultivar differences in soybean leaf photosynthetic capacity

This study investigated the basis of the negative relationship between leaf size and photosynthetic rate per unit of area among five cultivars of soybeans. Exposure of developing mainstem leaves to light, and sizes and light saturated photosynthesis rates of those leaves at maturity were compared in cultivars grown in field plots for two years at Beltsville, Maryland, USA. Plants were grown both in stands at 2.5 cm by 1 m spacing and as isolated plants. While cultivar differences in leaf size were large and consistent in both planting arrangements, significant cultivar differences in light saturated photosynthetic rates were found only in plants grown in stands. Similarly, leaf size was significantly correlated with specific leaf weight only for plants grown in stands. The mainstem apex and developing mainstem leaves experienced more severe shading in large-leaved cultivars than in small-leaved cultivars when plants were grown in stands. Thus, cultivar differences in photosynthetic capacity were probably a consequence of differences in the exposure of developing leaves to light.     

The distribution of wood-ants (Formica lugubris Zetterstedt) in a northern English forest

Abstract. 1. A survey of 202 ha of planted forest in Langdale Forest, North Yorkshire, in 1972 discovered 326 occupied and thirty-eight deserted nests of Formica lugubris Zetterstedt. The average density of occupied nests was therefore 1.61 ha^-1.
2. Nests were associated with most crop trees and wild trees present, but were most abundant near to plantation margins and regenerating natural scrub.
3. In planted areas 76% of nests were found 5 m or less from the plantation boundary. More nests were found on the south and west border of plantations than on the north and east respectively, and most nests were not shaded from the south or southeast.
4. An analysis of nearest neighbour measurements showed that the dispersion of nests was not random but contagious (clumped). Nest mounds were higher in shaded situations than in unshaded.
5. The diameter of nest mounds was greater in areas planted with trees before 1945 than in areas planted since 1945.
6. The present population of F.lugubris appears to have spread into planted areas from nests present in marginal natural woodland which escaped the disturbance of the area at the time of planting.     

Effects of salinity and cutting on the development of Phragmites australis

The effects of increased salinity and cutting the above ground biomass on the growth of Phragmites australis were evaluated by investigating four experimental reed stands grown in outdoor tanks. Two stands were treated with 30 salinity and the other two stands with freshwater; one stand of each treatment was cut to 20 cm during the second growing season. Growth conditions were observed until all the plants were dead at the end of the second year. The number of shoots emerged from the freshwater-treated stand was about 70% higher than that of the saltwater-treated stand. The number of shoots emerged from cut plant stands were markedly lower than uncut stands. The average shoot height was negatively affected by salinity and shoots that emerged after cutting further decreased in height. The average number of leaves on a shoot was not significantly affected by salinity, but reduced by cutting in both treatments. Leaf length, width and the distance between leaves were decreased by both salinity and cutting. In the freshwater-treated uncut stand more than 50% of the shoots formed panicles, but this proportion was reduced to 6% by salinity, to 15% by cutting, and to 0% by the combination of salinity and cutting. This study showed again that salinity reduces the growth of aboveground components. The growth, however, was most severely retarded by cutting combined with salinity, which has many implications for better management of P. australis stands.     

Studies in the physiology of the onion plant; further experiments on the effects of storage temperature and other factors on onions grown from sets

A wide range of factorial experiments at Wisley on onions grown from sets included combinations of the factors: storage of sets at high and low temperatures during the winter, variety, set size, set planting date and nitrogen manuring. Bolting, yield and ripening data are recorded. One experiment was repeated in Scotland and Northumberland where early ripening was expected to be more important than at Wisley. In general, all the factors enumerated except nitrogen manuring had large effects on bolting and yield, and storage temperature had a large effect on the time of ripening. Varieties can be selected such that large sets may be used without appreciable loss by bolting and maximum yield thus secured. Storage temperatures of from 20 to 24° C., applied for about 14 weeks from October onwards, can be used to control bolting and to increase the yield even of non-bolting strains by delaying ripening and so extending the growth period. Storage at 24° C. is more effective in preventing bolting than the lower temperatures, but 20° C. is probably more effective in delaying ripening. High-temperature storage is probably unsuitable for sets to be planted in the north and west of Great Britain because of the difficulty of ripening the bulbs. For these districts low-bolting strains are therefore essential. Storage at o° C. gives only a partial control of bolting and has no effect on ripening. Late planting of sets, although very effective in controlling bolting, results in a substantial loss of yield and, therefore, is not a practical measure. Nitrogen manuring had practically no effect on yield and could not be used to prevent the loss of yield caused by late planting.     

Leaf photosynthesis in pure swards of two grasses (Lolium perenne and Lolium multiflorum) subjected to contrasting intensities of defoliation

Photosynthetic rates were measured on light saturated, fully-expanded leaves in pure swards of Lolium perenne and Lolium multiflorum during late summer using 14-carbon dioxide. These swards were defoliated by cutting at three heights of 3, 6 and 9 cm above the ground. The photosynthetic rates of leaves on tillers in swards cut constantly 3 cm above ground level were higher than those of leaves in swards cut constantly 9 cm above ground level. Additional treatments with various sequences of cuts 3, 6 and 9 cm above ground level were designed to reduce damage to the growing points of tillers whilst ensuring satisfactory harvesting of the shoots. The photosynthetic rates of leaves on tillers cut to various heights above ground level at successive harvests were intermediate between those of similar leaves in the constantly low and high cut swards. The rates of photosynthesis of Italian ryegrass leaves were higher than those of perennial ryegrass leaves for a short time after defoliation of the constantly high cut swards. However, these perennial ryegrass leaves quickly adapted their rates of photosynthesis to the higher irradiances they received after cutting. Thus grass species differing in morphology adjust to management practices by the use of different photosynthetic strategies.     

沿海基干林带结构调控对林分冠层结构参数及林地土壤的影响

以上海浦东沿海水杉基干林带为研究对象,分析水杉林分间伐以及间伐后林下套种其他树种构建复层林2种结构调控措施下林分冠层及林地土壤的变化。结果表明:间伐和复层林构建可显著促进上层乔木树高和胸径的生长,也有助于林下乔灌木和草本植物的发育;未间伐水杉林带LAI最高,其次为复层林带,间伐林分最低。各林分林隙分数的分布特征与LAI相反;3种林分土壤全N、全P和速效K含量差异不显著,而间伐林和复层林土壤速效P、水解N和有机质含量比未间伐林有进一步改善,但间伐林分和复层林带之间土壤养分状况没有显著差异;林分结构调控增加了0～50cm土壤有机碳储量,其中以0～15cm土层有机碳密度最高。复层林带和间伐林土壤呼吸速率比未间伐林分别提高了42%和33%。     

Growth characteristics of black alder in pure and mixed stands at the southern boundary of its range

The age dynamics of the main taxation characteristics (height, diameter, stand basal area, average and current increment of stock, and total stand productivity) have been analyzed in stands of different types. The influence of admixed species on the formation of the stands is assessed. The expediency of planting pure stands on heavy textured soils of floodplains in the forest steppe has been proven.     

The Genus Primula: Section Capitatae Pax

Summary

Atlantic Hazelwoods form a distinctive (yet apparently over-looked) habitat that appears to be unique to western Scotland and, to a lesser degree, western Ireland. The origins of this habitat appear to date from the early Holocene, and there is compelling evidence that some stands may have existed in unbroken succession for 10,000 years. Recognition of the potential relict status of some areas of hazel gradually emerged as a result of several decades of study of the lichen flora. The smooth bark of hazel in western Scotland is known to support a species-rich and specialised lichen community (the Graphidion), including rare, endemic and old woodland indicator species. However, the full expression of this community is found to occur only in certain stands: often coastal, with no (or very few) other trees or shrubs present, and with a long history, but with little evidence of intensive exploitation. Seeking further evidence to back up the relic status of these Atlantic Hazelwood stands proved elusive. Very little work appears to have been directed towards looking at ‘natural’ hazel dynamics, with always the assumption that all stands of hazel have undergone coppice management at some time. It appears that Tansley (1949) is the only authority to recognise that in certain situations and conditions, hazel will form a climax scrub. However, how hazel stools develop over time in the absence of coppicing has been tentatively investigated by using DNA evidence to test for clonality between adjacent stools, with some convincing results. Atlantic Hazelwoods are already recognised as of international importance for their lichen flora. Suggestions are put forward for sympathetic conservation of this habitat, whilst at the same time recognising the need to promote more research to investigate the relict woodland status of the Atlantic Hazelwoods.     

单位面积杆数对温室标准切花菊品质影响的预测模型

通过对切花菊不同品种、不同单株主杆数、不同定植密度和不同定植日期的试验,定量分析了单位面积杆数对标准切花菊叶面积指数动态变化规律和各外观品质指标的影响,在此基础上,构建了以冠层吸收的生理辐热积为指标的可定量预测单位面积不同杆数对温室标准切花菊品质影响的预测模型,并用与建模相独立的试验数据对模型进行了检验.结果表明：随单位面积杆数的增加,切花菊的叶面积指数增加,其植株的平均株高、茎粗、出叶数、花径均降低.所建模型对多杆栽培和不同密度单杆栽培的标准切花菊单杆地上部分鲜质量、株高、茎粗、出叶数、花径和单位面积出花枝数的预测值与实测值的决定系数（R²）分别为0.95、0.96、0.94、0.91、0.81和0.97,预测相对误差分别为16.1%、10.1%、12.8%、13.4%、15.9%和16.1%,模型模拟精度较高.该模型可为温室标准切花菊栽培密度和栽培杆数的优化以及品质的光温调控提供理论依据和决策支持.