Arbeitsger?te bei der Holzhauerei und ihre Instandhaltung

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The importance of the soil skeleton for plant-available nutrients in sites of the Southern Black Forest,Germany

The skeletal fraction of forest soils in the Southern Black Forest has a cation exchange capacity (CEC) within the same order of magnitude as fine earth. As the base saturation in the skeleton is much higher than in the fine earth, stones provide a physiologically more favourable environment for nutrient uptake by plants. The fact that 70% of the skeleton grains showed adherent rhizomorphae and/or fine roots suggests that this potential is widely used by nutrient-adsorbing tissues. Therefore the ecological importance of this additional and, until now, unconsidered ion pool available to plants is probably higher than what is reflected by simple ion quantities. The effective CEC of the coarse fraction in forest sites with crystalline bedrock is reasonably predictable considering the water vapour adsorption of the 105°C dried skeleton at a suction of pF 4.6 (vapour pressure equilibrium with an oversaturated K₂SO₄ solution). The content of exchangeable base cations in the coarse fraction can be estimated using the content of exchangeable Mg in the fine earth. These stochastic relations are causally plausible. The regressions are a first approach to identify pedo-transfer functions predicting the skeletons nutrient potential with the aid of easily measurable site parameters.     

III. Buchbesprechungen

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Mechanical shock during transportation: effects on seedling performance

A study was carried out to monitor shocks to seedling planting stock during transport from nursery to the planting site in normal commercial reforestation operations. Size and exact time of mechanical shocks were measured by a recorder placed inside seedling boxes. Seedling shipments by refrigerated semi-trailer, 5-ton truck, pickup truck, small trailer and all-terrain vehicles were monitored in Alberta and British Columbia. Number of shocks, peak acceleration and average drop height were tabulated for travel on both paved and gravel roads.Twenty-two trials involving seven species were established at nurseries and field locations covering several ecological zones in both provinces. Frozen-stored, cool-stored, and freshly lifted seedlings were used in the trials. Seedlings were given two mechanical stress treatments by dropping them 30 times from 0.5-m and 30 times from 1.0-m, respectively. Control seedlings were not dropped. Treatments were applied to nursery-trial seedlings not exposed to normal handling and transport, and to field-trial seedlings after transport to the planting site. Six root growth potential tests were made with treated and control seedlings in conjunction with the nursery trials.Seedling survival and volume growth were recorded for two growing seasons and the results statistically analysed.     

III. Buchbesprechungen

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