Tree biomass in the Swiss landscape: nationwide modelling for improved accounting for forest and non-forest trees

Trees outside forest (TOF) can perform a variety of social, economic and ecological functions including carbon sequestration. However, detailed quantification of tree biomass is usually limited to forest areas. Taking advantage of structural information available from stereo aerial imagery and airborne laser scanning (ALS), this research models tree biomass using national forest inventory data and linear least-square regression and applies the model both inside and outside of forest to create a nationwide model for tree biomass (above ground and below ground). Validation of the tree biomass model against TOF data within settlement areas shows relatively low model performance (R 2 of 0.44) but still a considerable improvement on current biomass estimates used for greenhouse gas inventory and carbon accounting. We demonstrate an efficient and easily implementable approach to modelling tree biomass across a large heterogeneous nationwide area. The model offers significant opportunity for improved estimates on land use combination categories (CC) where tree biomass has either not been included or only roughly estimated until now. The ALS biomass model also offers the advantage of providing greater spatial resolution and greater within CC spatial variability compared to the current nationwide estimates

Development of a botanical plant protection product from Larix by-products to protect grapevine from Plasmopara viticola

Extracts from European Larch (Larix decidua) were shown to be efficient to control grapevine downy mildew (Plasmopara viticola) under controlled and field conditions. Larixyl acetate and larixol were identified as the active compounds

Seed production and seed quality in a calcareous grassland in elevated CO2

In diverse plant communities the relative contribution of species to community biomass may change considerably in response to elevated CO2. Along with species-specific biomass responses, reproduction is likely to change as well with increasing CO2 and might further accelerate shifts in species composition. Here, we ask if, after 5 years of CO2 exposure, seed production and seed quality in natural nutrient-poor calcareous grassland are affected by elevated CO2 (650 muL L-1 vs 360 muL L-1) and how this might affect long-term community dynamics. The effect of elevated CO2 on the number of flowering shoots (+ 24 0.01) and seeds (+ 29 to above ground biomass responses in this year, suggesting that the overall allocation to sexual reproduction remained unchanged. Compared among functional groups of species we found a 42 number (P > 0.01) of graminoids, a 33 and no significant change in legumes (- 38 Large responses particularly of two graminoid species and smaller responses of many forb species summed up to the significant or marginally significant increase in seed number of graminoids and forbs, respectively. In several species the increase in seed number resulted both from an increase in flowering shoots and an increase in inflorescence size. In most species, seeds tended to be heavier (+ 12 in eight out of 13 species. The fraction of germinating seeds did not differ between seeds produced in ambient and elevated CO2, but time to germination was significantly shortened in two species and prolonged in one species when seeds had been produced in elevated CO2. Results suggest that species specific increases in seed number and changes in seed quality will exert substantial cumulative effects on community composition in the long run

The symmetry of competitive interactions in mixed Norway spruce, silver fir and European beech forests

Questions: We aim for a better understanding of the different modes of intra- and inter-specific competition in two- and three-species mixed-forests. How can the effect of different modes of competitive interactions be detected and integrated into individual tree growth models? Are species interactions in spruce–fir–beech forests more associated with size-symmetric or size-asymmetric competition? Do competitive interactions between two of these species change from two- to three-species mixtures? Location: Temperate mixed-species forests in Central Europe (Switzerland). Methods: We used data from the Swiss National Forest Inventory to fit basal area increment models at the individual tree level, including the effect of ecological site conditions and indices of size-symmetric and size-asymmetric competition. Interaction terms between species-specific competition indices were used to disentangle significant differences in species interactions from two- to three-species mixtures. Results: The growth of spruce and fir was positively affected by increasing proportions of the other species in spruce–fir mixtures, but negative effects were detected with increasing presence of beech. We found that competitive interactions for spruce and fir were more related to size-symmetric competition, indicating that species interactions might be more associated with competition for below-ground resources. Under constant amounts of stand basal area, the growth of beech clearly benefited from the increasing admixture of spruce and fir. For this species, patterns of size-symmetric and size-asymmetric competitive interactions were similar, indicating that beech is a strong self-competitor for both above-ground and below-ground resources. Only for silver fir and beech, we found significant changes in species interactions from two- to three-species mixtures, but these were not as prominent as the effects due to differences between intra- and inter-specific competition. Conclusions: Species interactions in spruce–fir–beech, or other mixed forests, can be characterized depending on the mode of competition, allowing interpretations of whether they occur mainly above or below ground level. Our outcomes illustrate that species-specific competition indices can be integrated in individual tree growth functions to express the different modes of competition between species, and highlight the importance of considering the symmetry of competition alongside competitive interactions in models aimed at depicting growth in mixed-species forests

Management of soil suppressiveness against soil-borne diseases

Soils suppressive to soil-borne diseases have attracted the attention of farmers and researchers for decades and many suppressive soils have been described. Microorganisms and soil microbial communities involved in suppressiveness have been studied intensively, but the underlying mechanisms are still not well understood. Suppressiveness to soil- as well as air-borne diseases has been shown to be highly site-specific. We will review how suppressiveness can be influenced by agricultural practices. Suppressiveness destroyed e.g. by steam sterilisation of soils could only be partially restored on the short-term by re-inoculation of soils, and the success of re-inoculation depended on the soil matrix as well as on the inoculum used. Long-term management (e.g. conventional or organic management), tillage regime, and short- or long-term fertility inputs have the potential to alter soil suppressiveness, yet the effect of a particular practice is still difficult to predict. Application of biocontrol organisms such as Pseudomonads or Bacillussp. can have a beneficial effect against particular diseases on the short-term, but they can rarely persist after introduction in natural soils. Application of suitable composts can often help to sanitize fields contaminated with soil-borne pathogens more efficiently than individual biocontrol organisms. An ongoing study tries to identify key microbial consortia responsible for the beneficial effect of composts to allow a targeted application