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Autorite kirjalikud load asuvad õendusteaduse osakonnas õppekorralduse spetsialisti käes

Is forest mushroom productivity driven by tree growth? Results from a thinning experiment

• Most of the edible forest mushrooms are mycorrhizal and depend on carbohydrates produced by the associated trees. Fruiting patterns of these fungi are not yet fully understood since climatic factors alone do not completely explain mushroom occurrence. • The objective of this study was to retrospectively find out if changing tree growth following an increment thinning has influenced the diversity patterns and productivity of associated forest mushrooms in the fungus reserve La Chanéaz, Switzerland. • The results reveal a clear temporal relationship between the thinning, the growth reaction of trees and the reaction of the fungal community, especially for the ectomycorrhizal species. The tree-ring width of the formerly suppressed beech trees and the fruit body number increased after thinning, leading to a significantly positive correlation between fruit body numbers and tree-ring width. • Fruit body production was influenced by previous annual tree growth, the best accordance was found between fruit body production and the tree-ring width two years previously. • The results support the hypothesis that ectomycorrhizal fruit body production must be linked with the growth of the associated host trees. Moreover, the findings indicate the importance of including mycorrhizal fungi as important players when discussing a tree as a carbon source or sin

Expeditious building of ring-porous earlywood vessel chronologies without loosing signal information

Chronologies of earlywood vessel size of ring-porous trees contain valuable ecological information, but long preparation procedures limit their application in ecological studies. Recent and fast techniques for wood surface preparation combined with automated image analysis are reducing the work needed to build chronologies, but might also entail measurement inaccuracy. In this study, we aim to evaluate the effect of a possible efficiency-accuracy trade-off on ecological signal strength. To this end, we compare measurements of mean vessel area from two recent and fast procedures carried out on sanded wood surfaces with a reference procedure based on an accurate survey from thin sections. Measurements were performed on increment cores of 15 sessile oaks (Quercus petraea (Mattuschka) Liebl.) for the period 1956-2006. Dissimilarities in results with the reference procedure were quantified and evaluated. Our data show that the workload can be reduced by more than 20-fold when using the highly automated procedure. Signal weakening caused by measurement errors is negligible for vessels >6,000μm2 and can be easily compensated by increasing the sample size. Manual correction of misrecognized vessels hardly reduced this error further. The new procedures constitute a major step towards an efficient and accurate analysis of earlywood vessel chronologies of ring-porous tree specie

Drought alters timing, quantity, and quality of wood formation in Scots pine

Drought has been frequently discussed as a trigger for forest decline. Today, large-scale Scots pine decline is observed in many dry inner-Alpine valleys, with drought discussed as the main causative factor. This study aimed to analyse the impact of drought on wood formation and wood structure. To study tree growth under contrasting water supply, an irrigation experiment was installed in a mature Scots pine (Pinus sylvestris L.) forest at a xeric site in a dry inner-Alpine valley. Inter- and intra-annual radial increments as well as intra-annual variations in wood structure of pine trees were studied. It was found that non-irrigated trees had a noticeably shorter period of wood formation and showed a significantly lower increment. The water conduction cells were significantly enlarged and had significantly thinner cell walls compared with irrigated trees. It is concluded that pine trees under drought stress build a more effective water-conducting system (larger tracheids) at the cost of a probably higher vulnerability to cavitation (larger tracheids with thinner cell walls) but without losing their capability to recover. The significant shortening of the growth period in control trees indicated that the period where wood formation actually takes place can be much shorter under drought than the ‘potential' period, meaning the phenological growth perio

Growth response of Scots pine with different crown transparency status to drought release

• Context : One short-term adjustment of trees to drought is the reduction of photosynthetic tissues via leaf shedding. But in conifers, it usually takes several years to fully restore needle mass and assimilation capacity. • Aims : This study aims to evaluate whether leaf shedding sustainably damages conifers or if these trees still have the ability to recover from drought with respect to their foliage and wood formation. • Methods : An irrigation experiment was established in a mature dry forest to test the growth reactions of Scots pine (Pinus sylvestris L.) differing in crown transparency (low, medium, high) to a drought release by irrigation in comparison with equivalent control trees growing under naturally dry conditions on the same site. • Results : Drought and high crown transparency had a combined negative effect on radial tree growth: Control trees with medium to high crown transparencies showed a substantially shorter growth period and a long-lasting growth depression in response to the severe summer drought in 2003. However, all trees benefited from irrigation, irrespective of their crown status, and immediately increased growth in response to irrigation. • Conclusion : The progressed drought-induced defoliation seemed to be a weakening factor for trees suffering from drought, but this can be reversed if the water supply is improve

Growth response of Scots pine with different crown transparency status to drought release

• Context : One short-term adjustment of trees to drought is the reduction of photosynthetic tissues via leaf shedding. But in conifers, it usually takes several years to fully restore needle mass and assimilation capacity. • Aims : This study aims to evaluate whether leaf shedding sustainably damages conifers or if these trees still have the ability to recover from drought with respect to their foliage and wood formation. • Methods : An irrigation experiment was established in a mature dry forest to test the growth reactions of Scots pine (Pinus sylvestris L.) differing in crown transparency (low, medium, high) to a drought release by irrigation in comparison with equivalent control trees growing under naturally dry conditions on the same site. • Results : Drought and high crown transparency had a combined negative effect on radial tree growth: Control trees with medium to high crown transparencies showed a substantially shorter growth period and a long-lasting growth depression in response to the severe summer drought in 2003. However, all trees benefited from irrigation, irrespective of their crown status, and immediately increased growth in response to irrigation. • Conclusion : The progressed drought-induced defoliation seemed to be a weakening factor for trees suffering from drought, but this can be reversed if the water supply is improve

ROXAS – an efficient and accurate tool to detect vessels in diffuse-porous species

Wood-anatomical parameters form a valuable archive to study past limitations on tree growth and act as a link between dendrochronology and ecophysiology. Yet, analysing these parameters is a time-consuming procedure and only few long chronologies exist. To increase measurement efficiency of wood-anatomical parameters, novel tools like the automated image-analysis system ROXAS were developed. So far, ROXAS has only been applied to measure large earlywood vessels in ring-porous species. In this study, we evaluate if ROXAS is also suitable for efficient and accurate detection and measurement of vessels in diffuse-porous European beech. To do so, we compared the outcome of ROXAS with that of the established measurement programme Image-Pro Plus in terms of efficiency and accuracy. The two methods differed substantially in efficiency with automatic measurements using ROXAS being 19 times faster than with Image-Pro Plus. Although the procedures led to similar patterns in annual variation of mean vessel area and vessel density, the absolute values differed. Image-Pro Plus measured systematically lower mean vessel areas and higher vessel densities than ROXAS. This was attributed to the species-specific technical settings in ROXAS, leading to more realistic results than those obtained using the default settings in Image-Pro Plus. A shortcoming of ROXAS was, however, that small vessels

Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests

An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner-Alpine regions, the species composition in low elevation forests is changing: The sub-boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub-Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger-scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed-effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small-diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services

Sympathetic Background in Tolkien’s Prose

Considering Tolkien’s poetic sensitivity and love of nature, it is no wonder that his fiction abounds with natural images and landscape descriptions. More often than not, these references to the environment seem to be in harmony with the events or the structure of the story. In other words, Tolkien seems to resort to this old universal literary device usually referred to as “sympathetic background” whereby nature mirrors, mimics or reacts to the characters’ deeds, emotions or state of mind. As a contribution to previous and current studies on nature in Middle-earth, this paper examines Tolkien’s art in portraying nature — whether it be the immediate environment (geography, plants, animals …) , or the workings of the elements (the forces constituting the weather) — in an attempt to unveil a subtext under the prism of “sympathetic background”.