This article presents empirical results of a multivariate analysis run with the aim to identify (apparent and latent) socioeconomic transformations that shape the distribution pattern of cropland in a metropolitan region of southern Europe (Athens, Greece) over a sufficiently long time interval spanning from 1960 to 2010. The study area is representative of monocentric cities expanding in an unregulated fashion and experiencing sequential cycles of economic growth and recession. Percent share of cropland in total municipal area increased moderately over time. A non-linear relationship with the distance from downtown Athens was also observed, indicating that the highest rates of cropland were observed at a distance ranging between 20 and 30 km from the inner city. A multivariate regression was run by decade at each municipality of the study area using 11 predictors with the aim to identify the factors most associated with cropland decline along urban fringes. Distance from downtown Athens, soil and climate quality, population growth rate, and competing land use were the most relevant factors correlated with cropland expansion (or decline) in the study area. Competing land use was particularly important for cropland decline in a first urbanization phase (1960–1980), while population growth rate—and hence an increased human pressure—was positively associated with agricultural areas in a subsequent phase (1990–2010). In these regards, per capita urban land had a non-linear spatial behavior, being correlated negatively with cropland in 1960 and 1970 and positively in 2010, possibly indicating a moderate change from a monocentric model towards a more dispersed metropolitan configuration impacting distribution of agricultural areas. Empirical findings of this study suggest that effective strategies supporting peri-urban agriculture require a comprehensive knowledge of the local socioeconomic context and relevant biophysical conditions—specifically focusing on the dominant soil and climate attributes.
A diverse collection of Juglans species and hybrids with potential to serve as walnut rootstocks was evaluated to identify resistance to Phytophthora cinnamomi, a destructive pathogen affecting commercial production of Persian walnuts worldwide. A total of 35 Juglans genotypes, comprising hybrids and Juglans microcarpa, plus three Juglans regia genotypes as comparison, were inoculated during two seasons (spring and autumn) for 3 years, with two isolates of P. cinnamomi. Inoculations were carried out on excised shoots of the different genotypes by replacing a bark disk with a P. cinnamomi culture plug. After incubation, necrosis length caused by the pathogen was measured. Data were collected and statistically analyzed with generalized linear mixed models. This work pointed out a seasonal influence on some Juglans genotype response to P. cinnamomi: both hybrids and J. microcarpa groups were significantly less sensitive in autumn compared with spring (P = 0.0006), thus this condition must be considered when selecting Juglans for resistance to this pathogen. Three genotypes of J. regia, known for its susceptibility to P. cinnamomi, were used as comparison. Results show good levels of resistance to P. cinnamomi in J. microcarpa genotypes, confirming literature results. Among J. microcarpa genotypes, the Jmi03 is quite promising for its in vitro propagation. A number of Juglans hybrids, H5/18, 7/28,8/29, 10/43, and 6/22, showed significantly higher levels of resistance to P. cinnamomi, compared with susceptible J. regia genotypes. Evaluation, in naturally infected fields, of clonal genotypes and seedling-progenies of resistant genotypes, grafted with commercial walnut varieties, is currently under way and will provide additional information for successful usage.
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