The impact of climate on radial growth and nut production of Persian walnut (Juglans regia L.) in Southern Kyrgyzstan

Abstract

This dendroecological study used time series of climate and radial growth and nut production of Juglans regia to investigate the relationships between these parameters. More than 200 trees growing at sites of different altitude, aspect, inclination and human impact intensity were sampled in walnut-fruit forests of the Jalal Abad region in Southern Kyrgyzstan. Tree rings were dated and ring widths measured. Wide and narrow tree rings, so called positive and negative pointer years, could be explained by climatic events. The mean annual increment differed significantly in different regions and altitudes. The highest values could be found in plantations and at higher altitudes (1,700–2,000 m a.s.l.). Analysing the relationships between nut crop yields and annual increment, we found a significantly positive correlation between nut crop of the current year (x) and ring width of the previous year (x − 1). This relationship is influenced by climatic conditions, and may change in the future if climatic conditions in the region will change. Our study shows that Persian walnut (Juglans regia L.) of South Kyrgyzstan can be used in dendrochronological studies, and illustrates the influence of site conditions and management practices on radial growth of this tree species.