Abstract
Kyrgyz walnut-fruit forests harbour a unique walnut diversity, which has rarely been investigated concerning nut properties and the influence of environmental conditions on these. We evaluated the influence of soil properties and altitude on physical and some chemical walnut properties at three sampling sites differing in altitude by 200 m. Walnut samples were collected from 15 randomly chosen trees. Soil samples from two depths under each tree were analysed for plant available mineral nutrients and soil chemical properties. In contrast to our hypothesis, physical nut and chemical kernel quality parameters did not differ between sampling sites at different altitude and were not affected by soil properties. Only pH showed a relationship with manganese availability in soil and kernel content, and was related to amino acid content of kernels. Tree and site-specific variability overrides abiotic influence caused by different altitude or soil properties and reflect the high genetic variability in these forests.
Highlights
The Republic of Kyrgyzstan is home to the largest naturally occurring walnut (Juglans regia L.) forest areas of the world [1], which are found in the Fergana Range North and East of Jalal-Abad at an elevation between approximately 1000 and 2000 m above sea level [2]
Soil organic matter (SOM) soil organic matter; EC electrical conductivity; ND Not detectable in 30–60 cm soil depth, whereas it was not significantly different at 0–30 cm depth, even though the average value was higher at DA
Our study shows that variability of physical and chemical walnut and kernel properties is higher between individual trees than between sites
Summary
The Republic of Kyrgyzstan is home to the largest naturally occurring walnut (Juglans regia L.) forest areas of the world [1], which are found in the Fergana Range North and East of Jalal-Abad at an elevation between approximately 1000 and 2000 m above sea level [2]. The walnut fruit forests are inhabited by around 40,000 people, which are highly dependent on the resources provided by the ecosystem to sustain their subsistence. Parts of the forest are leased to private households and used for wild fruit, fuelwood and hay collection as well as grazing and horticultural activities, which result in overexploitation of the biological resources with reduced forest rejuvenation and increased erosion [1]. Local people collect walnuts in autumn and sell these on local markets from where the nuts are partly exported to neighbouring countries. The unique walnut forests may hold the potential for quality walnut production a marketing beyond the local markets
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