Ein elektronisches Schorfwarngerät

Construction of an electronical scab warning apparatus The control of the apple-scab in Germany needs an average of 10–15 treatments a year. In order to minimize the pollution of the natural environment and to determine the optimal time of infection an electronical scab warning apparatus has been developed. The system consists of a console, housing the electronic and data display components, and a sensing unit. The sensing unit, placed in the orchard, monitors duration of foliage moisture, temperature, and humidity. These data are processed and stored electronically in the console. The influence of humidity during periods when the foliage is dry, which determines how long the dormant fungus remains viable, is also taken into account. The console can provide an accurate read-out of fungus growth at an stage, and indicates the exact moment for most effective spraying. The basis of this construction is an elarged Mills-table, which enables to determine the infection time according to temperature and moisture on the leaves.     

Fine root biomass of Scots pine stands differing in age and soil fertility in southern Finland

The biomass of small and large fine roots (相似文献   

Zur Verbreitung,Ernährung und Populationsdynamik der Rötelmaus (Clethrionomys glareolus) und der Gelbhalsmaus (Apodemus flavicollis) in einem Waldgebiet der Bayerischen Alpen

Zusammenfassung Nach einem Waldsamenjahr stieg die Populationsdichre der Rötel- und der Gelbhalsmaus bis zum Juni des folgenden Jahres auf das 40- bzw. 30fache bzw. auf schätzungsweise 40 Rötelmäuse und 15 Gelbhalsmäuse pro ha (s.Bäumler undHohenadl, 1980) an. Das Minimum mit einer geschätzten Dichte von 0,5–1 Indiv./ha wurde im Frühjahr des nächsten Jahres erreicht. Eine starke Einschränkung der Fruchtbarkeit bzw. eine Reduktion der Gonaden sowie eine Verminderung der Anzahl trächtiger und säugender Weibchen ging dem Zusammenbruch der Bevölkerungsdichte voraus. Danach erfolgte wieder eine kontinuierliche Zunahme der Fruchtbarkeit bei beiden Arten. Die Dichte blieb jedoch niedrig, vermutlich deshalb, weil die Nahrungsbasis nicht wesentlich verbessert wurde, bzw. weil bislang keine nennenswerte Menge an Samen mehr niedergefallen ist.Hinsichtlich der räumlichen Verteilung war eine deutliche Abhängigkeit von der Höhenlage, der Vegetation, der Bodenart und der Behandlung des Waldes erkennbar. Die Unterschiede in den ökologischen Ansprüchen waren hier allerdings bei der Rötelmaus deutlicher ausgeprägt als bei der Gelbhalsmaus.

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Distribution, nutrition and population dynamics of the bank vole (Clethrionomys glareolus) and the yellow-necked field mouse (Apodemus flavicollis) in a mountain forest of the Bavarian Alps

Nearly 1,300 small mammals, resp. 814 bank voles and 362 yellow-necked field mice were captured during the years 1977–1980 in an area of 50 km² in Chiemgau near Ruhpolding (Bavaria) in different altitudes and forest stands. After a rich seed production of beech (Fagus sylvatica) und spruce (Picea abies) in the year 1977 both species reproduced during the following winter under the snow cover. Until the following spring the density was increased 40- resp. 30-fold compared to the lowest density level in spring 1979. An analysis of the stomach contents showed that mice and voles had consumed mainly beechnuts in the winter 1977/78. In the following springtime seedlings of beech and maple were preferred until the cotyledones faded. Then mushrooms, first of all Ascomycetae and herbs were the main components in the diet. With these changes of nutrition the fertility and as a consequence also the number of animals were reduced beginning in summer 1978 until spring 1979. The density decreased at first in the high populated areas resp. in the lower altitudes of 650–900 m in mixed forests and later also in the higher altitudes of 1200–1450 m in spruce forests. In the following years the fertility (weight of gonads, number of embryoes, percentage of pregnant and lactating females) of both species was increased continuously again without any detectable influence of food or season. However there was nearly no seed production in this last period of observation and the density remained low.

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Mit 6 Abbildungen und einer Tabelle     

Income and labour productivity of collection and use of indigenous fruit tree products in Zimbabwe

Rural people in Africa periodically rely on wild fruits to supplement their diet and to generate cash income. However, scientific evidence on the economics of using indigenous fruit tree (IFT) products is scarce. The objective of the study was to fill in some of the gaps for which farm-household surveys were conducted in Zimbabwe during 1999–2000. Gross margins and returns to labour in collection, use and sale of products of Uapaca kirkiana (Muell. Arg., Wild Loquat), Strychnos sp. (S. cocculoides (Baker) and S. spinosa (Lam.), Monkey Orange) and Parinari curatellifolia (Planch. ex. Benth., Fever Tree) were compared with other farming activities. A random sample of over three hundred households in the Murehwa Communal and the Takawira Resettlement Areas was interviewed to gather income and expenditure data. Additionally, income, expenditure and labour allocation of 39 households were closely monitored for one year. Results indicated that the majority of rural households benefited from consumption and sale of indigenous (IF), although the extent varied among households. Within the households, children were the main consumers of fruits. Marketing of IF are carried out by women who used the receipts to purchase household goods. While U. kirkiana fruits were more important in generating cash income than others, fruits of P. curatellifoliawere important for home consumption during periods of food shortages. The gross margins for collection of IFT products were lower than for livestock and crop production. However, returns to labour from collection and use of IFT products were considerably greater than from other activities including gardening and livestock rearing. The study indicates that collection of IFT products is an efficient labour allocation strategy in Zimbabwe. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pentachlornitrobenzol-, Pentachloranilin- und Methylthiopentachlorbenzol-Rückstände bei Gemüsekulturen und in gärtnerisch genutzten Erden

In horticultural soils, pentachloronitrobenzene (PCNB, common name: quintozene) can be metabolized either by reduction of the nitrogroup to pentachloroaniline (PCA) or — formally regarded — by nucleophilic exchange of the nitro — against the methylthio-group to methylthiopentachlorobenzene (MTPCB). Formation of MTPCB from PCA in horticultural soils can be excluded.The residues of the metabolite MTPCB in horticultural soils in the period immediately following the date of application of PCNB containing pesticides can be in the same range as the residues of the metabolite PCA or they can exceed the PCA-residues. Then, in comparison with the PCA-residues the MTPCB-residues in horticultural soils disappear more rapid than the PCA-residues. The quotient MTPCB/PCA becomes the smaller the longer removes the date of sample-taking from the date of application of PCNB containing pesticides. These results indicate that MTPCB is not so persistent as PCA in horticultural soils. This statement can be proofed furthermore by the PCA-and MTPCB-residues measured in 1975/1976 in horticultural soils originating from areas to which Brassicol^®, a PCNB containing pesticide, was applicated before or up to 1972: the MTPCB-residues are generally 1/10 or less of the PCA-residues.Leaves or root vegetables grown as following cultures of lettuce on fields to which Brassicol^® was immediately applicated before cultivation of lettuce contain during a certain period HCB (hexachlorobenzene)-, PCNB-, PCA-and MTPCB-residues. Usually, in leaves vegetables, the MTPCB-residues are smaller than the PCA-residues of the same samples. However, in root vegetables, the MTPCB-residues of the same samples can be in the same range as the PCA-residues or can exceed the PCA-residues.Leaves or root vegetables grown in different periods in 1974 to 1976 on horticultural soils to which Brassicol^® was applicated before or up to 1972 usually contain no detectable or only small residues (in the range of 0,02 ppm) of MTPCB. Fruit vegetables grown on these soils does not contain either HCB-, nor PCNB- nor PCA, nor MTPCB-residues in detectable quantities.

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Mit 2 Abbildungen     

Zur Frage von Chlorfenvinphos-und 2,2′,4′-Trichloracetophenon-Rückständen bei Gemüsekulturen und in gärtnerisch genutzten Erden.Teil 1

The present work illustrates the situation of chlorfenvinphos and supposed trichloroacetophenone residues in vegetables and horticultural soils. For that purpose, samples of radishes, cucumbers, cress and soils were analysed. The received results admit — in connection with residue results that are given in literature — the following statements and conclusions:

1. After applications of chlorfenvinphos containing plant protectives chlorfenvinphos residues can remain in soils for half a year or longer. However, chlorfenvinphos is completely metabolized within a defined period and thereafter it cannot be detected. Therefore, repeated applications of chlorfenvinphos containing plant protectives should not lead to a continued accumulation of chlorfenvinphos in soils.
2. Trichloroacetophenone, the hydrolysis product of chlorfenvinphos with boiling half concentrated sulfuric acid, could not be detected in any sample of soils investigated by us — even after 30 applications of the chlorfenvinphos containing plant protective Birlane Granulat at the same area during the last 10 years.
3. A proof for the purpose that chlorfenvinphos is metabolized in vegetables to trichloroacetophenone cannot be given. Also trichloroacetophenone residues in vegetables resulting from soil can be excluded. From this point of view, it seems not to be necessary to establish a tolerance for trichloroacetophenone.
4. After application of Birlane Granulat the German waiting-time for radishes is 30 days and the waiting-time for cucumbers is 60 days. These waiting-times seem to be practically as shown in this work.
5. When Birlane Granulat is applicated to a certain plant culture, not only this culture but following cultures of plants can be contaminated with chlorfenvinphos over a certain period. The results of experiments with cress as following plant culture give rise to the conclusion that cress can contain higher chlorfenvinphos residues as admitted within a period of three months and more after application of Birlane Granulat.

     

Genetic transformation of silver birch (Betula pendula) by particle bombardment

We used in vitro callus and shoot cultures as target material for genetic transformation of silver birch (Betula pendula Roth) by particle bombardment. Cultivation of in vitro shoot cultures before particle bombardment and a long selection period, combined with a high concentration of selective agent after bombardment, led to the production of transformed plantlets that were stable, and no escapes were found among the tree lines produced. Clonal variation in transformation efficiency was found in transient expression of the beta-glucuronidase gene in callus cultures and in plantlets transformed by stable integration of the ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (RbcS) and neomycin phosphotransferase (npt2) genes.     

Use of modeled photosynthesis and decomposition to describe tree growth at the northern tree line

Growth of subarctic Scots pine (Pinus sylvestris L.) trees was investigated by a combination of process-based models and dendroecological approaches. Tree ring width indices were strongly autocorrelated and correlated with simulated photosynthetic production of the previous year and with organic matter N mineralization of the current year. An autoregressive model, with photosynthesis and N mineralization as external inputs, explained growth of the trees well. However, relationships for the period 1950-1992 differed significantly from relationships for the period 1876-1949; the slope of the regression of tree ring width index and photosynthesis was lower for the 1950-1992 period. Also, the autocorrelation structure of the data changed. First-order autocorrelation decreased and second-order autocorrelation increased from the earlier to the later period. This means that growth is becoming less sensitive to variations in photosynthetic production, whereas the relationships between growth and N mineralization are remaining fairly constant. We postulate that, although photosynthesis has increased in response to increasing CO2 concentrations, tree growth rate cannot parallel the increase in photosynthesis because potential growth rate is limited directly by temperature.     

Improving the establishment submodel of a forest patch model to assess the long-term protective effect of mountain forests

Simulation models such as forest patch models can be used to forecast the development of forest structural attributes over time. However, predictions of such models with respect to the impact of forest dynamics on the long-term protective effect of mountain forests may be of limited accuracy where tree regeneration is simulated with little detail. For this reason, we improved the establishment submodel of the ForClim forest patch model by implementing a more detailed representation of tree regeneration. Our refined submodel included canopy shading and ungulate browsing, two important constraints to sapling growth in mountain forests. To compare the old and the new establishment submodel of ForClim, we simulated the successional dynamics of the Stotzigwald protection forest in the Swiss Alps over a 60-year period. This forest provides protection for an important traffic route, but currently contains an alarmingly low density of tree regeneration. The comparison yielded a significantly longer regeneration period for the new model version, bringing the simulations into closer agreement with the known slow stand dynamics of mountain forests. In addition, the new model version was applied to forecast the future ability of the Stotzigwald forest to buffer the valley below from rockfall disturbance. Two scenarios were simulated: (1) canopy shading but no browsing impact, and (2) canopy shading and high browsing impact. The simulated stand structures were then compared to stand structure targets for rockfall protection, in order to assess their long-term protective effects. Under both scenarios, the initial sparse level of tree regeneration affected the long-term protective effect of the forest, which considerably declined during the first 40 years. In the complete absence of browsing, the density of small trees increased slightly after 60 years, raising hope for an eventual recovery of the protective effect. In the scenario that included browsing, however, the density of small trees remained at very low levels. With our improved establishment submodel, we provide an enhanced tool for studying the impacts of structural dynamics on the long-term protective effect of mountain forests. For certain purposes, it is important that predictive models of forest dynamics adequately represent critical processes for tree regeneration, such as sapling responses to low light levels and high browsing pressure.