Bracken effects on inorganic nitrogen leaching from an upland podzol

Leaching of inorganic N species to stream waters from upland areas of the UK is increasing, reflecting the increases in atmospheric deposition of nitrogen species due to increased levels of vehicular emissions. Bracken cover in UK uplands is also increasing overall ( Taylor, 1986 ), and the architectural nature of bracken has been shown to both increase deposition of atmospheric constituents to soils and change their chemical and physical nature. We have tested the nutrient status of upland podzols from the Lake District, Cumbria, UK, from under both moorland grass and bracken. The results show reduced levels of base cations and nitrate throughout the profile and decreases in the organic matter content of surface horizons as a consequence of bracken encroachment. We also report increased ammonium concentrations in lower soil horizons under bracken, possibly leading to increased leaching to stream waters. These results suggest either increased leaching of soil nutrients due to bracken encroachment or increased storage of nutrients within the bracken rhizome system. Results also suggest changes in either microbial activity or the microbial community of podzols, possibly due to the allelopathic nature of bracken. This may have caused changes in the soil nutrient dynamics, possibly accounting for some of the changes seen. We hypothesize that increased bracken cover within the British uplands has the potential to increase leaching of inorganic nitrogen to upland streams.     

Aerial applications of pesticides in the United Kingdom: 1978 to 1998

The aerial application of pesticides increased rapidly following the end of the Second World War, as, along with the development of a wider range of synthetic pesticides, more planes and pilots became available. It also became clear that new and previously inaccessible areas could be sprayed from the air. By the 1980s there were around 100 planes in the United Kingdom (UK) capable of spraying pesticides. However, increasing environmental pressure brought about the introduction of tougher legislation to control pesticide usage. The Food and Environment Protection Act 1985 and the Control of Pesticides Regulations 1986 (as amended) introduced tight controls over the application of pesticides from the air. Aerial application of pesticides has been monitored each year by the UK Ministry of Agriculture, Fisheries and Food (MAFF) since 1978, during which time the area treated has decreased significantly. This has been partly as a result of changes in legislation but also due to technological improvements in conventional crop‐protection methods. The area treated from the air in the UK has never risen above 2.5% of the area treated from the ground and in 1998 had fallen to less than 0.04% of the total area treated with pesticides. It is likely that this figure will continue to fall in the future. By 1998, the only pesticides to be sprayed from the air comprised fungicides, herbicides and insecticides. As a group, herbicides comprised the greatest area of treatment and the only target to show an increase in area treated in recent years has been bracken (Pteridium aquilinum (L) Kuhn). © Crown copyright 2000. Reproduced with the permission of Her Majesty's Stationery Office.     

The effectiveness of old and new strategies for the long‐term control of Pteridium aquilinum,an 8‐year test

There is a need for management strategies to control dominant perennial weeds and restore seminatural communities. We compared the effects of five weed control treatments on dense Pteridium aquilinum relative to an untreated experimental control over an 8‐year period with the aim of restoring acid grassland. The weed control treatments tested were as follows: cutting and bruising, both twice and thrice annually, and herbicide treatment (asulam in year 1 followed by annual spot retreatment of all emergent fronds). Pteridium aquilinum performance and plant species composition were monitored. Data were analysed using Bayesian mixed‐effect models and multivariate techniques. Cutting twice and thrice yearly and the asulam treatment all reduced frond density to zero; both bruising treatments were ineffective. The plant communities in the cut and asulam‐treated plots showed differences from the untreated and bruised plots; the asulam‐treated plots contained more ruderal species and the cut plots were more typical of acid grassland. Acid grassland recovery was fastest in the asulam‐treated plots, but the cut plots caught up after approximately 5 years. There were two important conclusions. First, an intractable weed like P. aquilinum can be eradicated and a vegetation more suited for grazing can be achieved by the continuous application of some treatments over many years. Here, success was achieved by cutting twice/thrice annually, or by a single asulam application followed by annual spot spraying of all emergent fronds for 8 years. Second, bruising, a treatment favoured by some conservation organisations, did not work and cannot be recommended. The use of long‐term, continuously applied treatments might be considered for all perennial weeds with large underground root/rhizome systems.     

Clastogenic effect of bracken fern (Pteridium aquilinum v. arachnoideum) diet in peripheral lymphocytes of human consumers: preliminary data

Ingestion of bracken fern (Pteridium aquilinum v. arachnoideum) is associated with digestive tract cancer in different regions of Japan, Venezuela and Brazil. In view of reports that dietary bracken fern causes chromosomal instability in cattle, the clastogenic effect of bracken fern was investigated, in a preliminary study, in peripheral lymphocytes obtained from habitual consumers and a control group of non‐consumers, which were carefully investigated about cancer history or family cancer history, negative in both cases, using protocols comparable to those previously described in studies in cattle raised on bracken pastures. Cytogenetic analysis showed significant increased levels of chromosomal abnormalities, such as chromatid breaks, in cultured peripheral lymphocytes of the consumer group. There was no correlation with subjects, gender, smoking habits or alcohol consumption, and the only correlation was with prolonged exposure to dietary bracken.     

蕨菜栽培及加工技术

蕨菜口味鲜美、营养价值高,日益受到消费者欢迎,种植蕨菜成为特色产业。介绍蕨菜的特性,阐述蕨菜引种、栽培及加工技术要点,并对种植蕨菜的经济效益进行分析,以期为广大农户进行蕨菜栽培、加工提供技术指导。     

不同护绿液对罐头蕨菜护绿效果的影响

采用正交试验极差比较法 ,研究了Cu2 ,Zn2 ,Na2 SO3 对蕨菜护绿效果的影响 ,同时对护绿液的温度和时间进行了选择 .结果表明 ,护绿液的最佳配比为 :Cu2 15 0mg·L-1 Zn2 15 0mg·L-1 Na2 SO3 10 0mg·L-1.其中Cu2 作用居第 1位 ,Zn2 和Na2 SO3 作用居第 2位 .护绿液的温度以 90℃为宜 ;处理时间为 2min .     

Clinico-pathological findings in cattle exposed to chronic bracken fern toxicity

AIM: To describe changes in blood and urine analytes in a large group of cattle exposed to chronic bracken fern toxicity, in order to identify parameters of potential diagnostic value.

METHODS: The study was conducted on two livestock farms on which bovine enzootic haematuria (BEH) was known to occur; Farm A grazed a local breed of cows and Farm B grazed Friesians. Group A1 comprised 66 cows from Farm A, Group B 54 cows from Farm B, and Group A2 13 heifers from Farm A. Ten healthy cows were used as controls. A complete physical examination was performed (Group A1), and blood (all groups) and urine (Groups A1 and B) samples were collected. Necropsies and histopathology were undertaken on four cows.

RESULTS: Anaemia, leucopenia, monocytosis, thrombocytopenia, hypergammaglobulinaemia, microhaematuria and proteinuria were detected. Multivariate statistical analyses established three phases of the disease of increasing severity; an initial phase, characterised by an extremely high monocytosis and otherwise normal parameters; an intermediate phase, characterised by monocytosis and moderate changes to other analytes; and a final phase, characterised by normal levels of monocytes and many changes to other analytes.

CONCLUSIONS AND CLINICAL RELEVANCE: Monocytosis, detected in 31% of the younger animals, could represent an initial response to consumption of bracken fern and might be useful as an early haematological marker of BEH.     

野生蕨菜的栽培

蕨菜主要生长在山区向阳次生林和撂荒地区域,即稀疏针阔混交林下、新开垦小片荒周围,其鲜嫩的茎叶属于安全无化肥、无农药残留等污染的天然绿色食品。在立地条件与野生蕨菜生境相仿林地上开展人工栽培驯化活动,对保护野生蕨菜资源、满足广大消费者需求、发展林农经济具有重要意义。     

蕨菜的栽培技术

介绍了蕨菜的营养价值和用途,并重点阐述了蕨菜的加工技术和人工引栽技术。     

甘肃省蕨菜天然资源调查

2005-2006年对甘肃的蕨菜天然资源进行了调查，结果表明，全省食用类天然蕨菜有4种，面积36．87万hm^2，集中分布在中南部天然林区；年产量1150．36t，加工能力188t.在调查研究的基础上，提出了甘肃省蕨菜天然资源保护建议。