C 13-norisoprenoids were measured in Riesling wines produced from the 1996, 1997 and 2003 vintages within the scope of a long-term nitrogen (N) fertilisation experiment. The wines were made from treatments of 0, 60 and 150 kg N/ha; each treatment was repeated four times and arranged in a completely randomised design. N fertilisation led to lower TDN (1,1,6-trimethyl-1,2-dihydronaphthalene) concentrations, whereas the trend was for actinidol and ß-damascenone to increase with increasing fertilisation and vitispirane was not affected by fertilisation. Yield, which was affected by N fertilisation, showed negative correlations with norisoprenoids in 1996 and 1997. Vitispirane, actinidol and TDN increased with storage time. The colder year, 1996, which had fewer sunshine hours, resulted in higher concentrations of ß-damascenone and lower concentrations of the norisoprenoids vitispirane, actinidol and TDN compared with 1997.

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Geostatistical analysis was conducted for the root distribution of Vitis berlandieri x Vitis riparia using dispersion index, fractal dimension, autocorrelation and semivariance. The data were derived from the observation of roots of six 12-year old Riesling/5C vine plants in a field experiment using minirhizothron technique. The dispersion index (DI) indicated the clustering of roots. Autocorrelation as a function of the distance lag showed that a higher DI was related to higher autocorrelation at small lags. Small scale (< 3cm) spatial analysis using variograms, showed a clustering of roots at short distances (< 6cm), but also a periodicity at greater distances (16cm) with hole effects in the variograms. The spatial variance for small scale was 60-85% within a range of 5-8cm. At medium scale (5-10cm) the spatial variance decreased to 0-20%. Geostatistical analysis is a useful tool to demonstrate variation in root distribution at plant level and to improve root sampling. Although the different geostatistical tools were related, it was not possible to deduce one result from the other quantitatively.

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