Response of Zweigelt Grapevine to Foliar Application of Potassium Fertilizer: Effects on Gas Exchange,Leaf Potassium Content,and Incidence of Traubenwelke

Zweigelt grapes have recently become susceptible to infestation with Traubenwelke (grape wilting) and the susceptibility has been assumed to be related to potassium (K) deficiency. The aim of the studies was to determine the effects of foliar application of K on leaf K content, leaf gas exchange, and on infestation of grapes with Traubenwelke. Three foliar fertilizers of K (Agripotash, 27.4% K; Nutrileaf, 33.2% K; and KNO₃, 38.7% K) and one of magnesium (Mg) (Agrovit Mg, 4.8% Mg) were tested on grapevines (Vitis vinifera, L. cv. ‘Zweigelt’) in field studies in 2003 and 2004. Foliar analysis showed that the tested foliar fertilizers had no effect on leaf K content in either year. Furthermore, the frequency of infestation with grape wilting was not reduced by K fertilizers. Measurements of leaf gas exchange in 2004 showed that all fertilizer treatments reduced photosynthesis (A) and stomatal conductance (gs) compared with the untreated control.     

Potential renal acid load in the diet of children and adolescents: impact of food groups, age and time trends

OBJECTIVE: The impact of acid-base balance on health is widely accepted. Here, we describe the potential renal acid load (PRAL) in the diet of healthy German children and adolescents. DESIGN: The Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study is an ongoing longitudinal (open cohort) study (start 1985) collecting detailed data on diet, growth, development and metabolism in infants, children and adolescents. SETTING: Research Institute of Child Nutrition, Dortmund. SUBJECTS: Seven hundred and twenty children and adolescents (351 boys and 369 girls), aged 3-18 years, provided 4187 yearly collected 3-day dietary records between 1995 and 2005. RESULTS: Mean daily PRAL was positive in all age/sex groups (6-21 mEq day-1), and significantly higher in boys than in girls after the age of 8 years, even when calculated as mEq MJ-1. Fruits, vegetables and potatoes had a negative impact on PRAL; cheese, dairy products, cereals/bread and meat/fish/eggs had a positive impact. In a mixed linear model, PRAL, expressed as mEq day-1 and mEq MJ-1, remained stable during the study period, since time trends of PRAL-relevant food groups countervail each other. PRAL intake (mEq MJ-1) was significantly positively associated (P < 0.0001) with fat intake (% of energy intake, %E), but negatively with carbohydrate intake (%E; P < 0.0001). CONCLUSIONS: The analysis of dietary habits in our sample of German children and adolescents showed a moderate excess of acidity. Especially older boys should be encouraged to eat more potatoes and vegetables as good sources of dietary alkalinity. The PRAL concept is compatible with current concepts for a healthy diet.     

Do forest decision-makers in Southeastern Norway adapt forest management to climate change?

To study whether, why, and how forestry decision-makers in Southeastern Norway adapt to climate change, we conducted a series of semi-structured interviews in focus groups consisting of non-industrial private forest owners, forest managers, and forest advisors. Our results show that a majority of the participants believed in climate change as a phenomenon, and had experienced events or observed changes that they attributed to climate change. However, we found little evidence of concern regarding climate change impacts on forest ecosystems and forestry among the participants. Instead, the majority regarded climate change more as an opportunity for the Norwegian forest-based sector than a threat. A minority had implemented proactive practices motivated by climate change but in all but one case, the adjustments were adaptation of forest infrastructure. In general, the participants agreed that the uncertainty associated with the effects of climate change and the (economical) uncertainty associated with adaptation of forest ecosystems were too large to change forest management practices at present. However, many participants, in particular the managers, are already adapting in response to experienced problems, such as increased frequency and duration of periods with low carrying capacity of the ground implying reduced or no accessibility within and to stands.     

Mixing oak and pine trees does not improve the functional response to severe drought in central French forests

Key message

Mixing sessile oak and Scots pine in central France to reduce intraspecific competition for water resources did not improve the ability of these two species to withstand severe drought during the summer.

Context

In order to reduce the impact of increasingly extreme droughts on forests, managers must adapt their practices to future climate conditions. Maintaining a greater diversity of tree species in temperate forest ecosystems is one of the recommended options.

Aims

We addressed how interactions between sessile oak and Scots pine in mixed forests in central France affect their functional response to drought.

Methods

We characterized the carbon isotope composition (δ¹³C) in the tree growth rings formed during wet (2001, 2007) or dry (2003, 2004) summers for each of the two species growing both in pure and in mixed stands in order to compare the effect of stand composition on variations in carbon isotope discrimination (Δ¹³C) among contrasted years.

Results

The severe drought in 2003 induced a strong decrease in Δ¹³C for all trees and in all stands as compared to 2001. This decrease was greater in pine than in oak. There was no significant difference between pure and mixed stands in the response of either species to drought.

Conclusion

Mixing sessile oak and Scots pine in stands in central France does not improve the ability of either species to withstand severe drought during the summer.