Impact of vegetation type on the content and spectroscopic properties of soil organic matter in the subalpine zone of the Bieszczady Mountains (Eastern Carpathians)

Aims: This study aimed to define how vegetation affects the content and chemistry of soil organic matter (SOM) in topsoil (O and A) horizons under blueberry shrubs (Vaccinietum myrtilli), and tall-grass vegetation in the subalpine zone of the Bieszczady Mountains (Eastern Carpathians, SE Poland). Methods: Topsoil samples (O and A horizons) were collected at ten sites covered with Vaccinium myrtillus L. and at ten sites covered with tall-grass vegetation. Above- and belowground parts of vegetation from each vegetation type were sampled. Total carbon (TC) and nitrogen (TN) content in soil and vegetation samples was determined using an elemental analyzer. SOM chemical properties were determined via Fourier-transform infrared spectroscopy and UV-Vis spectrophotometry. The mineral composition of the A horizons was determined via X-ray diffractometry (XRD). Results: V. myrtillus L. showed significantly higher TC content and C/N ratio in their aboveground parts compared to tall-grass vegetation, though TN content was significantly lower. FTIR-ATR spectra showed more intense absorption bands for V. myrtillus L. Soil mineral composition was similar across vegetation types. Soils under blueberry shrubs showed significantly higher mean content of organic carbon and TN in the O horizon compared to tall-grass vegetation, with no significant differences in the A horizon. Conclusions: Topsoil horizons under blueberry shrubs show higher soil organic carbon (SOC) and C/N ratios than those under tall-grasses. Our results suggest that shrubification may affect carbon concentration in the soil; however, the lack of bulk density measurements prevents quantification of SOM content and overall carbon sequestration, necessitating further studies.