No Evidence of an Elevation Effect Caused by Temperature Differences on Soil Microbial Properties in a Walnut Fruit Forest in Kyrgyzstan

This study is to investigate the effect of differences in annual average temperature on soil microbial communities as caused by elevation in walnut-fruit forests in Kyrgyzstan with similar vegetation. Soil samples ( n = 10 per site) were collected from top- and subsoil at three elevation levels (1000, 1300 and 1600 m above sea level) with an average temperature difference of 1.3 °C between sites and analysed for soil chemical and biological properties. All soil properties showed high variability within, but most revealed no differences between elevation levels. Microbial biomass, activity and community composition were largely similar at all sites with slightly higher fungal contribution based on internal transcribed spacer (ITS) sequence counts at high elevation, which, however was not reflected by ergosterol. Total soil organic carbon and nitrogen levels did not show elevation effects either. Mehlich-extractable elements revealed positive relationship with soil microbial properties, which was in particular pronounced for copper, manganese and zinc, highlighting the relevance of trace elements for soil microorganisms. The subsoil showed lower levels for all microbial properties even though they were on a comparably high level; it contained smaller sized bacteria and fungi, as revealed by MBC/dsDNA ratios, and fungal ITS counts/ergosterol ratios illustrating growth limitations for microorganisms in subsoils. Elevation with long-term average temperature differences did not yield pronounced differences in soil microbial properties, which were more potentially stronger affected by similar C input quantity and substrate quality from the similar vegetation. Consequently, climate change effects will more likely affect microbial properties indirectly via changes in vegetation.