Derivation of stem taper from the pipe theory in a carbon balance framework

A dynamic tree growth model is described. The model derives the development of stem taper and vertical distribution of branch basal area from the pipe model, assuming that reuse of active pipes is regulated by foliage dynamics in a vertically explicit crown with a foliage distribution of constant shape. Based on empirical findings, the pipe model was modified slightly to allow the foliage/sapwood ratio to vary as a function of distance from the treetop. Growth was derived from carbon balance in a stand of different size trees that may shade each other. The model was applied to old and middle-aged trees growing in dense and sparse stands of Scots pine for which stand-level measurements are available as a chronosequence, but individual trees have been measured only once. Measured trees were compared with corresponding simulated trees for stem taper and vertical distribution of branch basal area. The results indicated that the pipe model assumptions, combined with a model of tree growth, are capable of producing realistic predictions of the vertical distribution of stem and branch diameter in trees of different sizes in the stand. A comparison of the results with a simple form of the uniform stress theory showed good agreement between the two models. However, a significant difference was found between the measured relative contribution of heartwood to total stem diameter and the predicted share of disused pipes in the stem. A possible explanation for this discrepancy is that the transition from sapwood to heartwood is gradual rather than abrupt as assumed in the model. A modification of the pipe model to incorporate a gradual transition is outlined.     

Side effects of botanical insecticides on predatory mite Amblyseius andersoni (Chant)

The effects of the botanical insecticides Biopiren plus, Piresan plus and Neemazal T/S on the predatory mite Amblyseius andersoni (Chant) were tested under laboratory, semi-field, and field conditions. The tests carried out in the laboratory allowed detection of the direct toxicity on eggs and females as well as the effects on fecundity, whereas semi-field trials assessed their residual toxicity. In laboratory and semi-field tests, pyrethrins, particularly Piresan plus, proved to have the highest toxicity with E value, concerning both female mortality and fecundity, of 100?% and 45?%, respectively. The same product tested in the field only caused a significant reduction in the phytoseiid population shortly after the treatment. The relevant escape rate registered in semi-field tests could explain the lack of phytoseiid eradication in the field after treatment with pyrethrins.     

Olfactory reactions ofCryptolaemus montrouzieri Mulsant (Col., Coccinellidae) andChrysoperla carnea (Stephens) (Neur., Chrysopidae) in relation to period of starvation

In a laboratory study, it was tried to measure the extent of olfactory responses of two predators namelyCryptolaemus montrouzieri Mulsant andChrysoperla carnea (Stephens) to their respective preys at varied levels of their starvation. Results indicated that both the predators, irrespective of their developmenta stage, oriented more positively to their preys odour when they were deprived of food for certain period of time than they did so when tested directly without subjecting them to starvation. The first, second, third and fourth instar larvae and adults ofC. montrouzieri showed maximum response at 4 h, 8 h, 12 h, 12 h and 24 h of starvation, respectively. Similarly, the larvae ofC. carnea responded maximum with 4 h, 8 h and 12 h of hunger in first, second and third instar, respectively. However it was also evident that the continued starvation for more than certain ideal period affected the predators olfactory orientation negatively. But the adults ofC. montrouzieri differed slightly in their behavior as they could respond positively for comparatively longer period of starvation.

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Zusammenfassung In Laborversuchen wurde das Ausmaß der olfaktorischen Reaktionen der beiden PrädatorenCryptolaemus montrouzieri Mulsant undChrysoperla carnea (Stephens) auf deren BeuteinsektenPlanococcus citri Risso respektiveAcyrthosiphon pisum (Harris) und in Abhängigkeit von der Dauer einer vorangegangenen Hungerperiode, namentlich 2, 4, 8, 12, 16, 20 und 24 Stunden, ermittelt. Wie die Ergebnisse belegen, reagieren beide Prädatoren-Arten unabhängig vom jeweiligen Entwicklungsstadium stärker auf den Geruch ihrer Beute, wenn sie zuvor eine bestimmte Zeit unter Ausschluß von Nahrung gehalten worden waren. Dabei zeigte sich bei den Larven beider Arten ein typischer Verlauf der Attraktivität durch die Beute, nach dem diese mit zunehmender Dauer der Hungerperiode zunächst zunahm, um nach einem Maximum wieder deutlich abzufallen. Dieser Verlauf erwies sich für die einzelnen Larvenstadien als unterschiedlich. So wurde fürC. montrouzieri das Maximum bei den L₁-Larven mit durchschnittlich 9,33 von 15 durch die Beute angelockten Individuen bereits nach einer Hungerperiode von 4 h erreicht, für die L₂ jedoch mit 9,50 Individuen erst nach 8 und für die L₃ sowie L₄ erst nach 12 h mit 8,83 respektive 9,17 Individuen. Lediglich bei denC. montrouzieri-Adulten war eine kontinuierliche Zunahme der Attraktivität der Beute während des Untersuchungszeitraums von 24 h festzustellen, wobei das Maximum bei 10,00 Individuen lag. Analog wurde für das ersteC. carnea-Larvenstadium bei einer 4stündigen Hungerperiode mit 55,5% attrahierten Individuen das Maximum erreicht, wohingegen das zweite Stadium mit 61,1% bei der 8- und das dritte mit 65,5% bei der 12stündigen Hungerperiode die maximale Attraktion durch die Beute aufwies.

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With one table and one figure     

An artificial diet for shrews (Soricidae)

The common shrew (Sorex araneus L.) and the pygmy shrew (S. minutus L.) could be raised for several months in captivity using the tupaii food Altromin 8010^®. The artificial diet was well accepted and the animals increased in weight.     

Effects of short-term ozone exposure and soil water availability on the carbon economy of juvenile Douglas-fir

Effects of ozone and soil water availability on partitioning and translocation of assimilates were studied in three-year-old Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seedlings exposed, in separate experiments, to 0 and 106 or 0 and 514 micro g m(-3) ozone for 8 h day(-1) for 9 days. The dynamics of carbon from assimilated (14)CO(2) were followed. No interactions between ozone and soil water content were observed. Total net uptake of carbon was reduced by low soil water content, but was unaffected by ozone. Both ozone and low soil water content increased the amount of (14)C-photosynthates retained in the current-year needles. Total starch content in old and current-year needles was unaffected by ozone, but was reduced by low water availability. Translocation of carbon to the root-soil compartment was additively affected by ozone and low soil water content. The results suggest that dry periods in summer combined with high ozone concentrations cause the greatest reduction in the supply of carbon compounds to the root-soil compartment.     

Making British Forest Policy Work

Recent debate about British forest policy has been particularlyintense, and has led to major changes in the emphasis and administrationof policy. New prospects have emerged for lowland afforestation,and the relative importance accorded wood production objectiveshas declined. Changing public opinion and expectations, andchanging land use priorities, offer British foresters and forestrymany opportunities and challenges. The authors believe thata heightened awareness of the context and role of forest policyis essential if the forestry profession is to meet these challenges.This paper summarizes the nature of forest policy, and proposesvarious means by which British forest policy might develop toaddress its new circumstances. It is suggested that the generally-agreedobjectives of British forest policy will best be realized bysubstantive changes in the administration, implementation andfinancing of policy measures.     

Relationship between root growth potential and field performance in Aleppo pine

Commercial stocks of Aleppo pine in Spain vary in quality, but there is no accepted standard for evaluating quality. A RGP test was applied to six commercial seedling stocklots at two dates (November, February) and under two test conditions (growth-chamber, greenhouse). The RGP’s predictive ability was evaluated on two contrasting sites. There was a considerable variation in the RGP depending on application date, test conditions and stock factors. The RGP results for November were correlated with each other but they did not explain outplanting performance. The February results in the growth-chamber correlated well with survival at both sites. Regression models explained survival both in the lower (R ² = 97%) and in the higher (R ² = 92%) quality sites. RGP has a valid predictive ability for this species although it is sensitive to the test conditions. In this sense, a shorter and more intensive test performed right before planting may be more reliable.     

Abscisic acid relations and the response of Populus trichocarpa stomata to leaf water potential

The role of abscisic acid (ABA) in the mediation of stomatal responses to low leaf water potential was examined with intact plants and epidermal strips of Populus trichocarpa Torr. & A. Gray. Clones of this species grown under well-watered conditions maintain a high leaf conductance when the foliage wilts. However, foliar ABA concentration in P. trichocarpa increased manyfold in response to water stress as it did also in P. deltoides Bartr. ex Marsh. and P. trichocarpa x deltoides hybrids. Application of ABA to epidermal strips appeared to cause solute leakage, however stomata of P. trichocarpa remained partially open even when the guard cells were plasmolyzed. Foliar application of ABA induced closure of stomata in young expanding leaves, but not in fully expanded foliage. Ten days after ABA application, stomata on young leaves were open at high water potential but closed at low water potential. These characteristics are discussed with respect to wilty mutants of tomato and potato, which also have stomata unresponsive to leaf wilting.     

Creep in chipboard

Summary A considerable amount of data has been collected over the past few years on the rupture life of particleboard. This information is particularly valuable at the present time because there is increasing interest in the use of particleboard as a structural material. This paper presents a conventional analysis of the time to failure of three commercially available brands of particleboard at 20°C and at three fixed levels of relative humidity. A linear relationship is assumed between the logarithm of time to failure and stress level, and an improvement is made in the usual method of analysis by including censored specimens. The regression lines are projected forward to give estimates of the stress levels that can be sustained for a particular design life. It is found that the regression lines for 30 per cent and 65 per cent rh may be combined, but the specimens at 90 per cent rh are significantly lower in strength at any given time. One of the MUF bonded boards performs significantly better than a second MUF board over the long term, and this gives added weight to the view that there are other factors in the make-up and production of the board that are at least as important as the resin type itself.