Does low phosphorus supply limit seedling establishment and tree growth in groves of ectomycorrhizal trees in a central African rainforest?

In a forest grove at Korup dominated by the ectomycorrhizal species Microberlinia bisulcata, an experiment tested whether phosphorus (P) was a limiting nutrient. P-fertilization of seven subplots 1995-97 was compared with seven controls. It led to large increases in soil P concentrations. Trees were measured in 1995 and 2000. M. bisulcata and four other species were transplanted into the treatments, and a wild cohort of M. bisulcata seedlings was followed in both. Leaf litter fall from trees and seedlings were analysed for nutrients. Growth of trees was not affected by added P. Transplanted seedlings survived better in the controls than added-P subplots: they did not grow better with added-P.M. bisulcata wildlings survived slightly better in the added-P subplots in yr 1 but not later. Litter fall and transplanted survivors had much higher concentrations of P (not N) in the added-P than control subplots. Under current conditions, it appears that P does not limit growth of trees or hinder seedling establishment, especially of M. bisculcata, in these low-P grove soils.

Endozoochory by slugs can increase bryophyte establishment and species richness

Herbivory can affect plant community composition and diversity by removing biomass and reducing light competition. Herbivory may particularly benefit low growing species such as bryophytes, which are frequently limited by light competition. Gastropods are important herbivores of seed plants and cryptogams, furthermore, they can disperse propagules such as seeds and spores via endozoochory. However, whether gastropod herbivory can reduce the dominance of vascular plants and thereby promote the germination and establishment of endozoochorously dispersed bryophyte spores has never been tested experimentally. Moreover, it is unclear whether these possible interacting effects can influence bryophyte species richness. Here, we tested for endozoochorous spore dispersal by slugs, in combination with sowing of vascular plants, in a fully factorial common garden experiment. Enclosures contained either slugs previously fed with bryophyte sporophytes, control slugs, or no slugs. After 21 days the bryophyte cover was on average 2.8 times higher (3.9 versus 1.4) and after eight months the bryophyte species richness 2.6 times higher (5.8 versus 2.2) in enclosures containing slugs previously fed with bryophyte sporophytes than in the other treatments. Furthermore, after eight months high vascular plant cover reduced bryophyte diversity. On average enclosures without seed sowing harboured 1.6 times more bryophyte species than the ones with seed sowing (4.2 versus 2.6), indicating competitive effects of vascular plants on bryophytes. Our findings suggest that slugs are important dispersal vectors for bryophytes and that they can increase bryophyte populations and maintain bryophyte diversity by reducing the dominance of vascular plants.

Stand der Allgemeinen Psychotherapie und Gedanken zur Psychotherapie-Aus- und -Fortbildung aus psychologischer Sicht

Die Allgemeine Psychotherapie Grawes wird oft als ein bestimmter inhaltlicher Ansatz, gar als neue „Therapieschule“ missverstanden. Dabei hat er damit ein prozessuales Konzept der ständigen empirisch informierten Weiterentwicklung gemeint, mit einem Ziel, das per definitionem nie erreicht wird. Wie weit ist die Psychotherapie generell, wie weit der „Berner Ansatz“ auf dem Weg dahin gekommen? Wodurch wird Allgemeine Psychotherapie bedroht, wodurch voran gebracht? Dieser Beitrag versucht eine Standortbestimmung. Nicht nur die Therapie im engeren Sinne, auch die Art, in der wir PsychotherapeutInnen ausbilden, sollte den Idealen einer Allgemeinen Psychotherapie folgen: Im zweiten Teil des Betrages gehe ich darauf ein, wieweit unsere gegenwärtige Ausbildungs- und Trainingspraxis nicht dem Erkenntnisstand der Expertiseforschung entsprechen, wo Verbesserungspotential steckt, und wo die natürlichen Grenzen sind.